home Usage Electronic transformer connection diagram. A detailed scheme for choosing an electronic transformer and how to do it yourself. With a stable load, like halogen lamps, these electronic transformers can last indefinitely. While working with

Electronic transformer connection diagram. A detailed scheme for choosing an electronic transformer and how to do it yourself. With a stable load, like halogen lamps, these electronic transformers can last indefinitely. While working with

The work of the transformer is built on the conversion of current from a network with a voltage of 220 V. Devices are divided by the number of phases, as well as the overload indicator. On the market there are modifications of single-phase and two-phase types. The current overload parameter ranges from 3 to 10 A. If necessary, you can make an electronic transformer with your own hands. However, for this, it is first of all important to familiarize yourself with the device of the model.

Model Diagram

The electronic 12V circuit assumes the use of a pass relay. The winding is directly applied with a filter. To increase the clock frequency, there are capacitors in the circuit. They are available in open and closed types. Single-phase modifications use rectifiers. These elements are necessary to increase the conductivity of the current.

On average, the sensitivity of the models is 10 mV. With the help of expanders, problems with congestion in the network are solved. If we consider a two-phase modification, then it uses a thyristor. The specified element is usually installed with resistors. Their capacitance is on average 15 pF. The level of current conduction in this case depends on the load of the relay.

How to do it yourself?

You can easily do it yourself. For this, it is important to use a wired relay. It is advisable to select an expander for it impulse type. To increase the sensitivity parameter of the device, capacitors are used. Many experts recommend installing resistors with insulators.

To solve problems with power surges, filters are soldered. If we consider a home-made single-phase model, then it is more expedient to select a modulator for 20 watts. The output impedance in the transformer circuit should be 55 ohms. Output contacts are soldered directly to connect the device.

Capacitor Resistor Devices

The electronic transformer circuit for 12V involves the use of a wired relay. In this case, the resistors are installed behind the lining. As a rule, modulators are used in open type. Also, the electronic transformer circuit for 12V halogen lamps includes rectifiers, which are selected with filters.

Amplifiers are needed to solve switching problems. The output resistance parameter averages 45 ohms. The current conductivity, as a rule, does not exceed 10 microns. If we consider a single-phase modification, then it has a trigger. Some specialists use triggers to increase conductivity. However, in this case, heat losses increase significantly.

Transformers with regulator

The 220-12 V transformer with a regulator is quite simple. The relay in this case is standardly used wired type. The regulator itself is installed with a modulator. To solve problems with reverse polarity, there is a kenotron. It can be used with or without lining.

The trigger in this case is connected through conductors. These elements can only work with impulse expanders. On average, the conductivity parameter for transformers of this type does not exceed 12 microns. It is also important to note that the negative resistance indicator depends on the sensitivity of the modulator. As a rule, it does not exceed 45 ohms.

Using Wired Stabilizers

A 220-12 V transformer with a wired stabilizer is very rare. For normal operation of the device, a high-quality relay is required. The negative resistance index averages 50 ohms. The stabilizer in this case is fixed on the modulator. The specified element is primarily designed to lower the clock frequency.

The heat loss in this transformer is negligible. However, it is important to note that there is a lot of pressure on the trigger. Some experts in this situation recommend the use of capacitive filters. They are sold with or without a guide.

Models with diode bridge

A transformer (12 Volts) of this type is produced on the basis of selective triggers. The threshold resistance indicator for models is on average 35 ohms. To solve problems with lowering the frequency, transceivers are installed. Directly diode bridges are used with different conductivity. If we consider single-phase modifications, then in this case the resistors are selected for two plates. The conductivity index does not exceed 8 microns.

Tetrodes in transformers can significantly increase the sensitivity of the relay. Modifications with amplifiers are very rare. The main problem with transformers of this type is the negative polarity. It occurs due to an increase in the temperature of the relay. To remedy the situation, many experts recommend using triggers with conductors.

Model Taschibra

The electronic transformer circuit for 12V halogen lamps includes a two-plate trigger. The relay of the model is used wired type. Expanders are used to solve problems with reduced frequency. In total, the model has three capacitors. Thus, network congestion problems rarely occur. On average, the output resistance parameter is kept at 50 ohms. According to experts, the output voltage on the transformer should not exceed 30 watts. On average, the sensitivity of the modulator is 5.5 microns. However, in this case, it is important to take into account the workload of the expander.

RET251C device

The specified electronic transformer for lamps is produced with an output adapter. The expander of the model has a dipole type. In total, three capacitors are installed in the device. The resistor is used to solve problems with negative polarity. Capacitors in the model rarely overheat. The modulator is directly connected through a resistor. In total, the model has two thyristors. First of all, they are responsible for the output voltage parameter. Also, thyristors are designed to provide stable work expander.

Transformer GET 03

The transformer (12 Volt) of this series is very popular. In total, the model has two resistors. They are located next to the modulator. If we talk about indicators, it is important to note that the modification frequency is 55 Hz. The device is connected via an output adapter.

The expander is matched with an insulator. Two capacitors are used to solve negative polarity problems. The regulator in the presented modification is missing. The conductivity index of the transformer is 4.5 microns. The output voltage fluctuates around 12 V.

ELTR-70 device

The specified 12V electronic transformer includes two through thyristors. A distinctive feature of the modification is considered to be a high clock frequency. Thus, the current conversion process will be carried out without voltage surges. The expander of the model is used without lining.

There is a trigger to decrease the sensitivity. It is installed as a standard selective type. The negative resistance indicator is 40 ohms. For a single-phase modification, this is considered normal. It is also important to note that devices are connected via an output adapter.

Model ELTR-60

This transformer gives off high voltage stability. The model belongs to single-phase devices. The capacitor is used with high conductivity. Problems with negative polarity are solved by an expander. It is installed behind the modulator. There is no regulator in the presented transformer. In total, the model uses two resistors. Their capacitance is 4.5 pF. If you believe the experts, then overheating of the elements is very rare. The output voltage on the relay is strictly 12 V.

Transformers TRA110

The specified transformers work from the through relay. The expanders of the model are used in different capacities. The average output impedance of a transformer is 40 ohms. The model belongs to two-phase modifications. Its threshold frequency is 55 Hz. In this case, the resistors are dipole type. In total, the model has two capacitors. To stabilize the frequency during operation of the device, a modulator operates. The conductors of the model are soldered with high conductivity.

When assembling a particular design, sometimes the question of a power source arises, especially if the device requires a powerful power supply, and you cannot do without reworking it. Nowadays, it is not difficult to find iron transformers with the required parameters, they are quite expensive, and besides, their large size and weight are their main drawback. Good switching power supplies are difficult to assemble and set up, so they are not available to many. In his release, the video blogger Aka Kasyan will show the process of building a powerful and very simple power supply based on an electronic transformer. Although to a greater extent this video is devoted to reworking and increasing its power. The author of the video does not have a goal to finalize or improve the circuit, he just wanted to show how you can in a simple way increase output power. In the following, if you wish, all ways to refine such circuits with protection against short circuits and other functions can be shown.

You can buy an electronic transformer from this Chinese store.

An electronic transformer with a power of 60 watts was used as an experimental one, from which the master intends to draw as many as 300 watts. In theory, everything should work.

The transformer for alterations was bought for only 100 rubles at a construction store.

Here is a classic taschibra type electronic transformer circuit. This is a simple push-pull half-bridge self-oscillating inverter with a start circuit based on a symmetrical dinistor. It is he who gives the initial impulse, as a result of which the circuit starts. There are two high voltage reverse conduction transistors. In the native circuit, there were mje13003, two half-bridge capacitors for 400 volts, about 1 Mkf, a transformer feedback with three windings, two of which are master or base windings. Each of them consists of 3 turns of wire 0.5 millimeters. The third winding is the current feedback.

At the input there is a small 1 ohm resistor as a fuse and a diode rectifier. The electronic transformer, despite the simple circuitry, works flawlessly. This option does not have protection against short circuits, therefore, if you close the output wires, there will be an explosion - this is at least.

There is no stabilization of the output voltage, since the circuit is designed to work with a passive load in the face of office halogen lamps. The main power transformer has two - primary and secondary. The latter is designed for an output voltage of 12 volts plus or minus a couple of volts.

The first tests showed that the transformer has quite a lot of potential. Then the author found on the Internet a patented scheme for a welding inverter built almost according to such a scheme and immediately created a board for a more powerful version. I made two boards, because at the beginning I wanted to build a resistance welding machine. Everything worked without any problems, but then I decided to rewind the secondary winding to shoot this video, since the initial winding gave out only 2 volts and a huge current. And at the moment it is not possible to measure such currents due to the lack of the necessary measuring equipment.

You have more than powerful circuit. There are even fewer details. A couple of little things were taken from the first scheme. This is a feedback transformer, a capacitor and a resistor in the start circuit, a dinistor.

Let's start with transistors. On the native board were mje13003 in the to-220 package. Were replaced by more powerful mje13009 from the same line. the diodes on the board were of the n4007 type at one ampere. I replaced the assembly with a current of 4 amperes and with a reverse voltage of 600 volts. Any diode bridges of similar parameters will do. The reverse voltage must be at least 400 volts and the current must be at least 3 amperes. Half-bridge film capacitors with a voltage of 400 volts.

Experiments with electronic transformer Taschibra (Tashibra, Tashibra). Electronic Circuit Transformers

Experiments with electronic transformer Taschibra (Tashibra, Tashibra)

I think that the advantages of this transformer have already been appreciated by many of those who have ever dealt with the problems of powering various electronic structures. And the advantages of this electronic transformer are not few. Light weight and dimensions (as with all similar circuits), ease of alteration for one's own needs, the presence of a shielded case, low cost and relative reliability (at least if extreme modes and short circuits are not allowed, a product made according to a similar circuit is able to work long years). The range of application of power supplies based on "Tasсhibra" can be very wide, comparable to the use of conventional transformers.

The use is justified in cases of lack of time, funds, lack of the need for stabilization. Well, what, let's experiment? I will make a reservation right away that the purpose of the experiments was to test the Taschibra start-up circuit at various loads, frequencies and the use of various transformers. I also wanted to choose the optimal ratings of the POS circuit components and check the temperature regimes of the circuit components when working for various loads, taking into account the use of the Tasсhibra case as a radiator.

Scheme ET Taschibra (Tashibra, Tashibra)

Despite the large number of published electronic transformer circuits, I will not be too lazy to put it on display again. See fig1 illustrating the filling of "Tashibra".

The scheme is valid for ET "Tashibra" 60-150W. The mockery was carried out on ET 150W. It is assumed, however, that due to the identity of the schemes, the results of experiments can be easily projected onto specimens with both lower and higher power.

And once again I remind you what is missing "Tashibra" for a full-fledged power supply.1. The absence of an input smoothing filter (it is also an anti-interference filter that prevents conversion products from entering the network), 2. Current POS, which allows the excitation of the converter and its normal operation only in the presence of a certain load current,3. No output rectifier, 4. No output filter elements.

Let's try to fix all the listed shortcomings of "Tasсhibra" and try to achieve its acceptable operation with the desired output characteristics. To begin with, we will not even open the case of the electronic transformer, but simply add the missing elements ...

1. Input filter: capacitors C`1, C`2 with a symmetrical two-winding inductor (transformer) T`12. diode bridge VDS`1 with smoothing capacitor C`3 and resistor R`1 to protect the bridge from the charging current of the capacitor.

A smoothing capacitor is usually selected at the rate of 1.0 - 1.5 microfarads per watt of power, and a discharge resistor with a resistance of 300-500 kOhm should be connected in parallel with the capacitor for safety (touching the terminals of a charged relatively high voltage capacitor - not very nice). Resistor R`1 can be replaced with a thermistor 5-15Ohm / 1-5A. Such a replacement will reduce the efficiency of the transformer to a lesser extent.

At the output of the ET, as shown in the diagram in Fig. 3, we connect a circuit of the diode VD`1, capacitors C`4-C`5 and the inductor L1 connected between them - to obtain a filtered constant voltage at the output of the "patient". In this case, the polystyrene capacitor, placed directly behind the diode, accounts for the main share of the absorption of the conversion products after rectification. It is assumed that the electrolytic capacitor, "hidden" behind the inductance of the inductor, will perform only its direct functions, preventing the voltage "failure" at the peak power of the device connected to the ET. But in parallel with it, it is recommended to install a non-electrolytic capacitor.

After the addition of the input circuit, changes occurred in the operation of the electronic transformer: the amplitude of the output pulses (up to the VD`1 diode) increased slightly due to an increase in the voltage at the input of the device due to the addition of C`3, and modulation with a frequency of 50 Hz is practically absent. This is at the design load for ET. However, this is not enough. "Tashibra" does not want to start without a significant load current.

Installation of load resistors at the output of the converter for the occurrence of any minimum value current, capable of starting the converter, only reduces the overall efficiency of the device. Starting at a load current of about 100mA is performed at a very low frequency, which will be quite difficult to filter if the power supply is supposed to be used with UMZCH and other audio equipment with low current consumption in no signal mode, for example. The amplitude of the pulses is also less than at full load.

The change in frequency in modes of different power is quite strong: from a couple to several tens of kilohertz. This circumstance imposes significant restrictions on the use of "Tashibra" in this (still) form when working with many devices.

But let's continue. There were proposals to connect an additional transformer to the ET output, as shown, for example, in Fig.2.

It was assumed that the primary winding of the additional transformer is capable of creating a current sufficient for the normal operation of the basic ET circuit. The proposal, however, is tempting only because without disassembling the ET, with the help of an additional transformer, you can create a set of the necessary (to your liking) voltages. In fact, the no-load current of the additional transformer is not enough to start the ET. Attempts to increase the current (like a 6.3VX0.3A light bulb connected to an additional winding), capable of ensuring the NORMAL operation of the ET, only led to starting the converter and lighting the light bulb.

But, perhaps, someone will be interested in this result as well. connecting an additional transformer is also true in many other cases for solving many problems. So, for example, an additional transformer can be used in conjunction with an old (but working) computer PSU, capable of providing significant output power, but having a limited (but stabilized) set of voltages.

One could continue to search for the truth in shamanism around "Tashibra", however, I considered this topic exhausted for myself, because to achieve the desired result (stable start and exit to operating mode in the absence of load, and, therefore, high efficiency; a slight change in frequency when the PSU is operating from minimum to maximum power and stable start at maximum load) it is much more effective to get inside the Tashibra "and make all the necessary changes in the circuit of the ET itself in the manner shown in Figure 4. Moreover, since fifty such circuits were collected by me back in the era of Spectrum computers (for these computers). Various UMZCH, powered by similar PSUs, are still working somewhere. PSUs made according to this scheme proved to be the best, working, being assembled from a wide variety of components and in various versions.

Are we redoing? Of course!

Moreover, it is not difficult at all.

We solder the transformer. We heat it up for ease of disassembly in order to rewind the secondary winding to obtain the desired output parameters as shown in this photo or using any other technology.

In this case, the transformer is soldered out only in order to take an interest in its winding data (by the way: W-shaped magnetic circuit with a round core, standard dimensions for computer PSUs with 90 turns of the primary winding, wound in 3 layers with a wire with a diameter of 0.65 mm and 7 turns secondary winding with a fivefold folded wire with a diameter of approximately 1.1 mm; all this without the slightest interlayer and interwinding insulation - only varnish) and make room for another transformer.

For experiments, it was easier for me to use ring magnetic circuits. They take up less space on the board, which makes it possible (if necessary) to use additional components in the body volume. In this case, a pair of ferrite rings with outer, inner diameters and height, respectively, 32X20X6mm, folded in half (without gluing) - H2000-HM1, was used. 90 turns of the primary (wire diameter - 0.65 mm) and 2x12 (1.2 mm) turns of the secondary with the necessary winding insulation.

The communication winding contains 1 turn of the mounting wire with a diameter of 0.35 mm. All windings are wound in the order corresponding to the numbering of the windings. Insulation of the magnetic circuit itself is mandatory. In this case, the magnetic circuit is wrapped with two layers of electrical tape, reliably, by the way, fixing the folded rings.

Before installing the transformer on the ET board, we solder the current winding of the switching transformer and use it as a jumper, soldering it there, but not passing the transformer ring through the window.

We install the wound transformer Tr2 on the board, soldering the leads in accordance with the diagram in Fig. 4. and passing the winding wire III through the ring window of the switching transformer. Using the rigidity of the wire, we form a kind of geometrically closed circle and the feedback loop is ready. In the gap of the mounting wire, which forms the windings III of both (switching and power) transformers, we solder a sufficiently powerful resistor (> 1W) with a resistance of 3-10 Ohms.

In the diagram in Figure 4, standard ET diodes are not used. They should be removed, as, indeed, the resistor R1 in order to increase the efficiency of the unit as a whole. But you can also neglect a few percent efficiency and leave the listed details on the board. At least at the time of the experiments with ET, these details remained on the board. The resistors installed in the base circuits of the transistors should be left - they perform the functions of limiting the base current when the converter is started, facilitating its work on a capacitive load.

Transistors should certainly be installed on radiators through insulating heat-conducting pads (borrowed, for example, from a faulty computer PSU), thereby preventing them from accidental instantaneous heating and providing some of their own safety in case the radiator is touched during operation of the device.

By the way, the electrical cardboard used in ET to isolate transistors and the board from the case is not heat-conductive. Therefore, when "packing" the finished power supply circuit into a standard case, such gaskets should be installed between the transistors and the case. Only in this case will at least some kind of heat sink be provided. When using a converter with powers over 100W, it is necessary to install an additional heatsink on the device case. But this is so - for the future.

In the meantime, having completed the installation of the circuit, we will perform another safety point by turning on its input in series through a 150-200 W incandescent lamp. The lamp, in case of an emergency (short circuit, for example), will limit the current through the structure to a safe value and, in the worst case, will create additional illumination of the workspace.

At best, with some observation, the lamp can be used as an indicator, for example, of a through current. So, a weak (or somewhat more intense) glow of the lamp filament with an unloaded or lightly loaded converter will indicate the presence of a through current. The temperature of the key elements can serve as a confirmation - heating in the through current mode will be quite fast. When a working converter is working, the glow of a filament of a 200-watt lamp visible against the background of daylight will appear only at the threshold of 20-35 watts.

First start

So, everything is ready for the first launch of the converted "Tashibra" scheme. We turn it on for a start - without load, but do not forget about the pre-connected voltmeter to the output of the converter and the oscilloscope. With correctly phased feedback windings, the converter should start without problems.

If the start did not occur, then the wire passed into the window of the switching transformer (having previously soldered it from the resistor R5), we pass it on the other side, giving it, again, the appearance of a finished coil. Solder the wire to R5. Reapply power to the converter. Did not help? Look for errors in installation: short circuit, "non-solder", erroneously set ratings.

When starting a working converter with the specified winding data, the display of an oscilloscope connected to the secondary winding of the transformer Tr2 (in my case, to half of the winding) will display a sequence of clear rectangular pulses that does not change in time. The conversion frequency is selected by the resistor R5 and in my case, with R5 = 5.1 Ohm, the frequency of the unloaded converter was 18 kHz.

With a load of 20 ohms - 20.5 kHz. With a load of 12 ohms - 22.3 kHz. The load was connected directly to the instrument-controlled winding of the transformer with effective value voltage 17.5 V. The calculated voltage value was somewhat different (20 V), but it turned out that instead of the nominal value of 5.1 ohms, the resistance installed on the board R1 = 51 ohms. Be attentive to such surprises from Chinese comrades.

However, I considered it possible to continue the experiments without replacing this resistor, despite its significant but tolerable heating. When the power delivered by the converter to the load was about 25 W, the power dissipated by this resistor did not exceed 0.4 W.

As for the potential power of the PSU, at a frequency of 20 kHz, the installed transformer will be able to deliver no more than 60-65W to the load.

Let's try to increase the frequency. When the resistor (R5) with a resistance of 8.2 ohms is turned on, the frequency of the converter without load increased to 38.5 kHz, with a load of 12 ohms - 41.8 kHz.

With such a conversion frequency, with the existing power transformer, you can safely serve a load with a power of up to 120W. You can experiment further with the resistances in the POS circuit, achieving the required frequency value, bearing in mind, however, that too much resistance R5 can lead to generation failures and unstable start-up of the converter . When changing the PIC parameters of the converter, it is necessary to control the current passing through the converter keys.

You can also experiment with the PIC windings of both transformers at your own peril and risk. In this case, you should first calculate the number of turns of the switching transformer according to the formulas posted on the page //interlavka.narod.ru/stats/Blokpit02.htm, for example, or using one of the programs of Mr. Moskatov posted on the page of his website // www.moskatov.narod.ru/Design_tools_pulse_transformers.html.

Tashibra improvement - a capacitor in the PIC instead of a resistor!

You can avoid heating the resistor R5 by replacing it with ... a capacitor. In this case, the POS circuit certainly acquires some resonant properties, but no deterioration in the operation of the PSU is manifested. Moreover, a capacitor installed instead of a resistor heats up much less than a replaced resistor. Thus, the frequency with a 220nF capacitor installed increased to 86.5 kHz (without load) and amounted to 88.1 kHz when operating on a load. The start-up and operation of the converter remained as stable as in the case of using a resistor in the POS circuit. Note that the potential power of the PSU at this frequency increases to 220 W (minimum). Transformer power: the values are approximate, with certain assumptions, but not overestimated.

Unfortunately, I did not have the opportunity to test a PSU with a high load current, but I believe that the description of the experiments performed is enough to draw the attention of many to such, here, simple circuits of power converters worthy of use in a wide variety of designs .

I apologize in advance for possible inaccuracies, reticences and errors. I'll correct my answers to your questions.

Constantine (riswel)

Russia, Kaliningrad

Since childhood - music and electro / radio equipment. Soldered a lot of schemes of the most diverse for various reasons, and simply - for the sake of interest - both my own and others'.

For 18 years of work in North-West Telecom, he has manufactured many different stands for testing various equipment being repaired. Designed several, different in functionality and element base, digital meters pulse duration.

More than 30 rationalization proposals for the modernization of units of various specialized equipment, incl. - power supply. For a long time I have been more and more engaged in power automation and electronics.

Why am I here? Yes, because everyone here is the same as me. There are a lot of interesting things for me here, since I am not strong in audio technology, but I would like to have more experience in this particular direction.

datagor.ru

Electronic transformers. Device and work. Peculiarities

Consider the main advantages, advantages and disadvantages of electronic transformers. Consider the scheme of their work. Electronic transformers appeared on the market quite recently, but managed to gain wide popularity not only in amateur radio circles.

Recently, articles based on electronic transformers have often been observed on the Internet: homemade blocks power supplies, chargers and more. In fact, electronic transformers are a simple network switching power supply. This is the cheapest power supply. The phone charger is more expensive. The electronic transformer works from a network of 220 volts.

Device and principle of operation

Scheme of work

The generator in this circuit is a diode thyristor or dinistor. Mains voltage 220 V is rectified by a diode rectifier. There is a limiting resistor at the power input. It serves as both a fuse and protection against throws. mains voltage when turned on. The operating frequency of the dinistor can be determined from the ratings of the R-C chain.

Thus, it is possible to increase the operating frequency of the generator of the entire circuit or reduce it. The operating frequency in electronic transformers is from 15 to 35 kHz, it can be adjusted.

The feedback transformer is wound on a small ring of the core. It has three windings. The feedback winding consists of one turn. Two independent windings of driving circuits. These are the basic windings of transistors with three turns.

These are equivalent windings. Limiting resistors are designed to prevent false positives of transistors and at the same time limit the current. Transistors are used high-voltage type, bipolar. Often use transistors MGE 13001-13009. It depends on the power of the electronic transformer.

t half-bridge capacitors also depend on a lot, in particular the power of the transformer. They are used with a voltage of 400 V. The power also depends on the overall dimensions of the core of the main pulse transformer. It has two independent windings: mains and secondary. Secondary winding with a rated voltage of 12 volts. It is wound based on the required output power.

The primary or network winding consists of 85 turns of wire with a diameter of 0.5-0.6 mm. Low-power rectifier diodes with a reverse voltage of 1 kV and a current of 1 ampere are used. This is the cheapest rectifier diode you can find in 1N4007 series.

The diagram shows in detail the capacitor that sets the frequency of the dinistor circuits. The resistor at the input protects against voltage surges. Dinistor series DB3, its domestic analogue KH102. There is also a limiting resistor at the input. When the voltage on the frequency-setting capacitor reaches its maximum level, the dinistor breaks down. A dinistor is a semiconductor spark gap that fires at a certain breakdown voltage. Then it sends a pulse to the base of one of the transistors. Schema generation starts.

Transistors work in opposite phase. An alternating voltage is formed on the primary winding of the transformer of a given frequency of operation of the dinistor. On the secondary we get the right voltage. In this case, all transformers are designed for 12 volts.

Transformer model of the Chinese manufacturer Taschibra

It is designed to power 12 volt halogen lamps.

With a stable load, like halogen lamps, these electronic transformers can last indefinitely. During operation, the circuit overheats, but does not fail.

Operating principle

A voltage of 220 volts is supplied, rectified by a VDS1 diode bridge. Capacitor C3 begins to charge through resistors R2 and R3. The charge continues until the DB3 dinistor breaks through.

The opening voltage of this dinistor is 32 volts. After it is opened, voltage is supplied to the base of the lower transistor. The transistor opens, causing self-oscillations of these two transistors VT1 and VT2. How do these self-oscillations work?

The current begins to flow through C6, transformer T3, base control transformer JDT, transistor VT1. When passing through the JDT, it causes VT1 to close and VT2 to open. After that, the current flows through VT2, through the base transformer, T3, C7. Transistors constantly open and close each other, work in antiphase. appear at the middle point rectangular pulses.

The conversion frequency depends on the inductance of the feedback winding, the capacitance of the bases of the transistors, the inductance of the transformer T3 and the capacitances C6, C7. Therefore, it is very difficult to control the conversion frequency. The frequency also depends on the load. To force the opening of transistors, accelerating capacitors of 100 volts are used.

To reliably close the VD3 dinistor, after generation occurs, rectangular pulses are applied to the cathode of the VD1 diode, and it securely locks the dinistor.

In addition, there are devices that are used for lighting fixtures, feed powerful halogen lamps for two years, work faithfully.

Power supply based on electronic transformer

Mains voltage through a limiting resistor is supplied to the diode rectifier. The diode rectifier itself consists of 4 low-power rectifiers with a reverse voltage of 1 kV and a current of 1 ampere. The same rectifier is on the transformer block. After the rectifier, the DC voltage is smoothed by an electrolytic capacitor. The charge time of the capacitor C2 depends on the resistor R2. At the maximum charge, the dinistor is activated, a breakdown occurs. On the primary winding of the transformer, an alternating voltage of the operating frequency of the dinistor is formed.

The main advantage of this scheme is the presence galvanic isolation with a 220 volt network. The main disadvantage is the low output current. The circuit is designed to power small loads.

Transformer model DM-150T06A

Current consumption 0.63 amperes, frequency 50-60 hertz, operating frequency 30 kilohertz. Such electronic transformers are designed to power more powerful halogen lamps.

Advantages and Benefits

If you use the devices for their intended purpose, then there is good feature. The transformer does not turn on without an input load. If you just plugged in the transformer, then it is not active. You need to connect a powerful load to the output in order to start working. This feature saves power. For radio amateurs who convert transformers into a regulated power supply, this is a disadvantage.

You can implement an auto-on system and a short-circuit protection system. Despite the shortcomings, the electronic transformer will always be the cheapest type of half-bridge power supply.

On sale you can find better inexpensive power supplies with a separate generator, but they are all implemented on the basis of half-bridge circuits using self-clocked half-bridge drivers, such as the IR2153 and the like. Such electronic transformers work much better, are more stable, short-circuit protection is implemented, at the input network filter. But the old Taschibra remains indispensable.

Disadvantages of electronic transformers

They have a number of disadvantages, despite the fact that they are made according to good schemes. This is the absence of any protection in cheap models. We have the simplest electronic transformer circuit, but it works. It is this scheme that is implemented in our example.

There is no mains filter at the power input. At the output after the inductor, there should be at least a smoothing electrolytic capacitor for a few microfarads. But he is also missing. Therefore, at the output of the diode bridge, we can observe an impure voltage, that is, all network and other interference is transmitted to the circuit. At the output, we get the minimum amount of interference, since galvanic isolation is implemented.

The operating frequency of the dinistor is extremely unstable, depending on the output load. If without an output load the frequency is 30 kHz, then with a load a rather large drop of up to 20 kHz can be observed, depending on the specific load of the transformer.

Another disadvantage is that the output of these electronic transformers is variable frequency and current. To use it as a power supply, you need to rectify the current. You need to rectify with pulse diodes. Conventional diodes are not suitable here due to the increased operating frequency. Since no protection is implemented in such power supplies, it is only necessary to close the output wires, the unit will not only fail, but will explode.

At the same time, during a short circuit, the current in the transformer increases to a maximum, so the output switches (power transistors) will simply burst. The diode bridge also fails, since they are designed for an operating current of 1 ampere, and in the event of a short circuit, the operating current increases sharply. The limiting resistors of the transistors, the transistors themselves, the diode rectifier, the fuse, which should protect the circuit, also fail, but does not.

A few more components may fail. If you have such an electronic transformer unit, and it accidentally fails for some reason, then it is not advisable to repair it, since it is not profitable. Only one transistor costs $1. A ready-made power supply can also be bought for $ 1, brand new.

Powers of electronic transformers

Today on sale you can find different models transformers, ranging from 25 watts to several hundred watts. A 60 watt transformer looks like this.

The manufacturer is Chinese, produces electronic transformers with power from 50 to 80 watts. Input voltage from 180 to 240 volts, mains frequency 50-60 hertz, operating temperature 40-50 degrees, output 12 volts.

Scheme of an electronic transformer for 12V halogen lamps. How is an electronic transformer arranged?

Model Diagram

The electronic transformer circuit for 12V halogen lamps involves the use of a pass relay. The winding is directly applied with a filter. To increase the clock frequency, there are capacitors in the circuit. They are available in open and closed types. Single-phase modifications use rectifiers. These elements are necessary to increase the conductivity of the current.

How to do it yourself?

You can easily make an electronic transformer with your own hands. For this, it is important to use a wired relay. It is advisable to select an expander for it of an impulse type. To increase the sensitivity parameter of the device, capacitors are used. Many experts recommend installing resistors with insulators.

Capacitor Resistor Devices

The electronic transformer circuit for 12V halogen lamps involves the use of a wired relay. In this case, the resistors are installed behind the lining. As a rule, modulators are used in open type. Also, the electronic transformer circuit for 12V halogen lamps includes rectifiers, which are selected with filters.

Transformers with regulator

Using Wired Stabilizers

Models with diode bridge

Model Taschibra

RET251C device

The specified electronic transformer for lamps is produced with an output adapter. The expander of the model has a dipole type. In total, three capacitors are installed in the device. The resistor is used to solve problems with negative polarity. Capacitors in the model rarely overheat. The modulator is directly connected through a resistor. In total, the model has two thyristors. First of all, they are responsible for the output voltage parameter. Thyristors are also designed to ensure stable operation of the expander.

Transformer GET 03

ELTR-70 device

Model ELTR-60

Transformers TRA110

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Alteration of electronic transformer | all he

An electronic transformer is a network switching power supply that is designed to power 12 Volt halogen lamps. More about this device in the article "Electronic transformer (introduction)".

The device has a fairly simple circuit. A simple push-pull oscillator, which is made according to a half-bridge circuit, the operating frequency is about 30 kHz, but this figure is highly dependent on the output load.

The circuit of such a power supply is not very stable, it does not have any protection against short circuit at the output of the transformer, perhaps precisely because of this, the circuit has not yet found wide application in amateur radio circles. Although recently in various forums there has been a promotion of this topic. People offer various options for refining such transformers. Today I will try to combine all these improvements in one article and offer options not only for improvement, but also for strengthening ET.

We will not delve into the basis of the operation of the circuit, but will immediately get down to business. We will try to refine and increase the power of the Chinese Taschibra ET by 105 watts.

To begin with, I want to explain why I decided to take on the power and alteration of such transformers. The fact is that recently a neighbor asked me to order Charger for a car battery that would be compact and lightweight. I didn’t want to collect, but later I came across interesting articles that dealt with the alteration of an electronic transformer. This prompted the thought - why not try?

Thus, several ETs from 50 to 150 watts were purchased, but the experiments with the alteration were not always successful, of all only 105 watts ET survived. The disadvantage of such a block is that it does not have a ring transformer, and therefore it is inconvenient to unwind or rewind the turns. But there was no other choice and this particular block had to be redone.

As we know, these blocks do not turn on without load, this is not always a virtue. I plan to get a reliable device that can be freely used for any purpose, without fear that the power supply may burn out or fail during a short circuit.

Refinement No. 1

The essence of the idea is to add short circuit protection, as well as eliminate the above disadvantage (activation of the circuit without an output load or with a low-power load).

Looking at the block itself, we can see the simplest circuit UPS, I would say that the scheme is not fully developed by the manufacturer. As we know, if you close the secondary winding of the transformer, then in less than a second the circuit will fail. The current in the circuit increases dramatically, the keys fail in an instant, and sometimes the basic limiters. Thus, the repair of the circuit will cost more than the cost (the price of such an ET is about $ 2.5).

The feedback transformer consists of three separate windings. Two of these windings feed the basic key chains.

To begin with, we remove the communication winding on the OS transformer and put a jumper. This winding is connected in series with the primary winding of the pulse transformer. Then we wind only 2 turns on the power transformer and one turn on the ring (OS transformer). For winding, you can use a wire with a diameter of 0.4-0.8 mm.

Next, you need to select a resistor for the OS, in my case it is 6.2 ohms, but the resistor can be selected with a resistance of 3-12 ohms, the higher the resistance of this resistor, the lower the short-circuit protection current. In my case, a wire resistor was used, which I do not advise you to do. We select the power of this resistor 3-5 watts (you can use from 1 to 10 watts).

During a short circuit on the output winding of a pulse transformer, the current in the secondary winding drops (in standard schemes ET during a short circuit, the current increases, disabling the keys). This leads to a decrease in the current on the OS winding. Thus, generation stops, the keys themselves are locked.

The only drawback of such a solution is that with a long-term short circuit at the output, the circuit fails, since the keys heat up and quite strongly. Do not subject the output winding to a short circuit with a duration of more than 5-8 seconds.

The circuit will now start up without load, in a word, we got a full-fledged UPS with short circuit protection.

Refinement No. 2

Now we will try to smooth out the mains voltage from the rectifier to some extent. To do this, we will use chokes and a smoothing capacitor. In my case, a ready-made choke with two independent windings was used. This choke was removed from the UPS DVD player, although you can use homemade choke.

After the bridge, an electrolyte with a capacity of 200 microfarads with a voltage of at least 400 volts should be connected. The capacitance of the capacitor is selected based on the power of the power supply 1uF per 1 watt of power. But as you remember, our PSU is designed for 105 watts, why is the capacitor used at 200uF? You will understand this very soon.

Refinement No. 3

Now about the main thing - the power of the electronic transformer and is it real? Actually there is only one reliable way enhancements without much modification.

For power it is convenient to use an ET with a ring transformer, since it will be necessary to rewind the secondary winding, it is for this reason that we will replace our transformer.

The network winding is stretched over the entire ring and contains 90 turns of wire 0.5-0.65 mm. The winding is wound on two stacked ferrite rings, which were removed from the ET with a power of 150 watts. The secondary winding is wound based on needs, in our case it is designed for 12 volts.

It is planned to increase the power to 200 watts. That is why an electrolyte was needed with a margin, which was mentioned above.

We replace the half-bridge capacitors with 0.5 microfarads; in the standard circuit, they have a capacitance of 0.22 microfarads. We replace the MJE13007 bipolar switches with MJE13009. The power winding of the transformer contains 8 turns, the winding was done with 5 wires of 0.7 mm wire, so we have a wire with a total cross section of 3.5 mm in the primary.

Move on. We put film capacitors with a capacity of 0.22-0.47 μF with a voltage of at least 400 Volts before and after the chokes (I used exactly the capacitors that were on the ET board and which had to be replaced to increase power).

Next, replace the diode rectifier. Conventional 1N4007 series rectifier diodes are used in standard circuits. The current of the diodes is 1 Amp, our circuit consumes a lot of current, so the diodes should be replaced with more powerful ones in order to avoid unpleasant results after the first turn on of the circuit. You can use literally any rectifier diodes with a current of 1.5-2 Amperes, reverse voltage of at least 400 volts.

All components, except for the board with the generator, are mounted on a breadboard. The keys were reinforced for heat dissipation through insulating gaskets.

We continue our alteration of the electronic transformer, adding a rectifier and a filter to the circuit. The chokes are wound on powdered iron rings (removed from a computer power supply unit), they consist of 5-8 turns. Winding is conveniently done immediately with 5 cores of wire with a diameter of 0.4-0.6 mm each core.

We select a smoothing capacitor with a voltage of 25-35 Volts, one powerful Schottky diode is used as a rectifier (diode assemblies made of computer block nutrition). You can use any fast diodes with a current of 15-20 Amperes.

all-he.ru

SCHEME OF ELECTRONIC TRANSFORMER FOR HALOGEN LAMPS

At present, pulse electronic transformers, due to their small size and weight, low price and wide range, are widely used in mass equipment. Due to mass production, electronic transformers are several times cheaper than conventional inductive iron transformers of the same power. Although electronic transformers from different companies may have different designs, the circuit is almost the same.

Take for example a standard electronic transformer marked 12V 50W, which is used to power table lamp. circuit diagram will be like this:

The electronic transformer circuit works as follows. The mains voltage is rectified by means of a rectifier bridge to a half-sine wave with twice the frequency. The D6 element of the DB3 type is called "TRIGGER DIODE" in the documentation, it is a bidirectional dinistor in which the polarity of the inclusion does not matter and it is used here to start the transformer converter. The dinistor fires during each cycle, starting the half-bridge generation. The opening of the dinistor can be adjusted. This can use for example for the function of dimming the connected lamp.The generation frequency depends on the size and magnetic conductivity of the feedback transformer core and the parameters of the transistors, usually in the range of 30-50 kHz.

At present, the production of more advanced transformers with the IR2161 chip has begun, which provides both the simplicity of the electronic transformer design and the reduction in the number of components used, as well as high performance. The use of this microcircuit significantly increases the manufacturability and reliability of the electronic transformer for powering halogen lamps. The schematic diagram is shown in the figure.

Features of the electronic transformer on IR2161: Intelligent half-bridge driver; Load short-circuit protection with automatic restart; Overcurrent protection with automatic restart; Operating frequency sweep to reduce electromagnetic interference; lamps; Soft start, excluding current overloads of lamps.

The input resistor R1 (0.25 watts) is a kind of fuse. Transistors type MJE13003 are pressed to the case through an insulating gasket with a metal plate. Even when operating at full load, the transistors heat up weakly. There is no ripple-smoothing capacitor after the mains voltage rectifier, so the output voltage of the electronic transformer when operating on a load is 40 kHz rectangular oscillations modulated by 50 Hz mains voltage ripples. Transformer T1 (feedback transformer) - on ferrite ring, the windings connected to the bases of the transistors contain a pair of turns, the winding connected to the junction point of the emitter and the collector of power transistors contains one turn of a single-core insulated wire. In ET, transistors MJE13003, MJE13005, MJE13007 are usually used. Output transformer on a ferrite W-shaped core.

To use an electronic transformer in a switching power supply, you need to connect a rectifier bridge on high-frequency high-power diodes to the output (regular KD202, D245 will not work) and a capacitor to smooth out ripples. At the output of the electronic transformer, a diode bridge is placed on diodes KD213, KD212 or KD2999. In short, we need diodes with a low voltage drop in the forward direction, capable of operating well at frequencies of the order of tens of kilohertz.

An electronic transformer converter does not work normally without a load, so it must be used where the load is constant in current and consumes sufficient current to reliably start the ET converter. When operating the circuit, it must be taken into account that electronic transformers are sources of electromagnetic interference, therefore an LC filter must be installed to prevent interference from penetrating into the network and into the load.

Personally, I used an electronic transformer to make a switching power supply tube amplifier. It also seems possible to feed them with powerful ULF class A or led strip, which are just designed for sources with a voltage of 12V and a large output current. Naturally, such a tape is not connected directly, but through a current-limiting resistor or by correcting the output power of an electronic transformer.

Forum on electronic transformers

Discuss the article SCHEME OF ELECTRONIC TRANSFORMER FOR HALOGEN LAMPS

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Electronic transformers for 12 V halogen lamps

Power supply

Home Ham radio Power supply

The article describes the so-called electronic transformers, which in fact are pulse step-down converters for powering halogen lamps, designed for a voltage of 12 V. Two versions of the transformers are proposed - on discrete elements and using a specialized microcircuit.

Halogen lamps are, in fact, a more advanced modification ordinary lamp incandescent. The fundamental difference lies in the addition of halogen compound vapors to the lamp bulb, which block the active evaporation of the metal from the surface of the filament during lamp operation. This allows the filament to be heated to higher temperatures, resulting in higher light output and a more uniform emission spectrum. In addition, the lamp life is extended. These and other features make the halogen lamp very attractive for home lighting, and more. A wide range of halogen lamps of various powers for 230 and 12 V is commercially produced. Lamps with a supply voltage of 12 V have the best technical specifications and a longer resource compared to 230 V lamps, not to mention electrical safety. To power such lamps from a 230 V network, it is necessary to reduce the voltage. You can, of course, use a conventional network step-down transformer, but this is expensive and impractical. The best solution is to use a 230V/12V step-down converter, often referred to in such cases as an electronic transformer or a halogen converter. Two variants of such devices will be discussed in this article, both are designed for a load power of 20 ... 105 watts.

One of the simplest and most common circuit solutions for step-down electronic transformers is a half-bridge converter with positive current feedback, the circuit of which is shown in fig. 1. When the device is connected to the network, capacitors C3 and C4 are quickly charged to the amplitude voltage of the network, forming half the voltage at the connection point. The R5C2VS1 circuit generates a trigger pulse. As soon as the voltage across the capacitor C2 reaches the opening threshold of the dinistor VS1 (24.32 V), it will open and a forward bias voltage will be applied to the base of the transistor VT2. This transistor will open and the current will flow through the circuit: the common point of the capacitors C3 and C4, the primary winding of the transformer T2, the winding III of the transformer T1, the collector-emitter section of the transistor VT2, the negative terminal of the diode bridge VD1. On the winding II of the transformer T1, a voltage will appear that maintains the transistor VT2 in the open state, while the reverse voltage from the winding I will be applied to the base of the transistor VT1 (windings I and II are turned on in antiphase). The current flowing through the winding III of the transformer T1 will quickly bring it into saturation. As a result, the voltage on the windings I and II T1 will tend to zero. Transistor VT2 will start to close. When it is almost completely closed, the transformer will begin to go out of saturation.

Rice. 1. Diagram of a half-bridge converter with positive current feedback

Closing the transistor VT2 and exiting the saturation of the transformer T1 will lead to a change in the direction of the EMF and an increase in the voltage on the windings I and II. Now, a forward voltage will be applied to the base of the transistor VT1, and the reverse voltage will be applied to the base of VT2. Transistor VT1 will start to open. The current will flow through the circuit: the positive terminal of the diode bridge VD1, the collector-emitter section VT1, the winding III T1, the primary winding of the transformer T2, the common point of the capacitors C3 and C4. Further, the process is repeated, and the second half-wave of voltage is formed in the load. After starting, the VD4 diode maintains the capacitor C2 in a discharged state. Since the converter does not use a smoothing oxide capacitor (it is not necessary when working on an incandescent lamp, on the contrary, its presence worsens the power factor of the device), then at the end of the half-cycle of the rectified mains voltage, the generation will stop. With the advent of the next half-cycle, the generator will start again. As a result of the operation of an electronic transformer, oscillations close in shape to sinusoidal ones with a frequency of 30 ... 35 kHz are formed at its output (Fig. 2), following in bursts with a frequency of 100 Hz (Fig. 3).

Rice. 2. Close in shape to sinusoidal oscillations with a frequency of 30 ... 35 kHz

Rice. 3. Oscillations with a frequency of 100 Hz

An important feature of such a converter is that it will not start without load, since in this case the current through the III T1 winding will be too small, and the transformer will not enter saturation, the self-generation process will fail. This feature makes idle protection unnecessary. The device with indicated in fig. 1 rating stably starts at a load power of 20 watts or more.

On fig. 4 shows a diagram of an improved electronic transformer, in which a noise suppression filter and a short-circuit protection unit in the load are added. The protection unit is assembled on a transistor VT3, a diode VD6, a zener diode VD7, a capacitor C8 and resistors R7-R12. A sharp increase in the load current will lead to an increase in the voltage on the windings I and II of the transformer T1 from 3 ... 5 V in the nominal mode to 9 ... 10 V in the short circuit mode. As a result, a bias voltage of 0.6 V will appear on the basis of the transistor VT3. The transistor will open and shunt the start circuit capacitor C6. As a result, with the next half-cycle of the rectified voltage, the generator will not start. Capacitor C8 provides a protection shutdown delay of about 0.5 s.

Rice. 4. Scheme of an improved electronic transformer

The second version of the electronic step-down transformer is shown in fig. 5. It is easier to repeat, since it does not have one transformer, while being more functional. This is also a half-bridge converter, but controlled by a specialized IR2161S chip. All the necessary protective functions: from low and high mains voltage, from idle mode and short circuit in the load, from overheating. The IR2161S also has a soft start function, which consists in a smooth increase in the output voltage when turned on from 0 to 11.8 V for 1 s. This eliminates a sharp surge of current through the cold filament of the lamp, which significantly, sometimes several times, increases its service life.

Rice. 5. The second version of the electronic step-down transformer

At the first moment, and also with the arrival of each subsequent half-cycle of the rectified voltage, the microcircuit is powered through the VD3 diode from the parametric stabilizer on the VD2 zener diode. If the power is supplied directly from the 230 V network without using a phase power regulator (dimmer), then the R1-R3C5 circuit is not needed. After entering the operating mode, the microcircuit is additionally powered from the output of the half-bridge through the d2VD4VD5 circuit. Immediately after starting, the frequency of the internal clock generator of the microcircuit is about 125 kHz, which is much higher than the frequency of the output circuit C13C14T1, as a result, the voltage on the secondary winding of the transformer T1 will be small. The internal oscillator of the microcircuit is controlled by voltage, its frequency is inversely proportional to the voltage across the capacitor C8. Immediately after switching on, this capacitor begins to charge from the internal current source of the microcircuit. In proportion to the increase in voltage on it, the frequency of the microcircuit generator will decrease. When the voltage on the capacitor reaches 5 V (approximately 1 s after switching on), the frequency will decrease to an operating value of about 35 kHz, and the voltage at the transformer output will reach a nominal value of 11.8 V. This is how a soft start is implemented, after it is completed, the DA1 microcircuit goes into operating mode in which pin 3 of DA1 can be used to control the output power. If you connect parallel to the capacitor C8 variable resistor with a resistance of 100 kOhm, it is possible, by changing the voltage at pin 3 of DA1, to control the output voltage and adjust the brightness of the lamp. When the voltage at pin 3 of the DA1 chip changes from 0 to 5 V, the generation frequency will change from 60 to 30 kHz (60 kHz at 0 V is the minimum output voltage and 30 kHz at 5 V is the maximum).

The CS input (pin 4) of the DA1 chip is the input of the internal error signal amplifier and is used to control the load current and voltage at the half-bridge output. In the event of a sharp increase in load current, for example, during a short circuit, the voltage drop across the current sensor - resistors R12 and R13, and therefore at pin 4 of DA1, will exceed 0.56 V, the internal comparator will switch and stop the clock generator. In the event of a load break, the voltage at the output of the half-bridge may exceed the limit allowable voltage transistors VT1 and VT2. To avoid this, a resistive-capacitive divider C10R9 is connected to the CS input through the VD7 diode. When the threshold value of the voltage across the resistor R9 is exceeded, the generation also stops. In more detail, the operating modes of the IR2161S chip are discussed in.

You can calculate the number of turns of the windings of the output transformer for both options, for example, using a simple calculation method, you can choose a suitable magnetic circuit for overall power using the catalog.

According to , the number of turns of the primary winding is

NI = (Uc max t0 max) / (2 S Bmax),

where Uc max - maximum mains voltage, V; t0 max - maximum open state time of transistors, ms; S - cross-sectional area of the magnetic core, mm2; Bmax - maximum induction, Tl.

Number of turns of the secondary winding

where k is the transformation ratio, in our case we can take k = 10.

Drawing printed circuit board the first version of the electronic transformer (see fig. 4) is shown in fig. 6, the location of the elements - in fig. 7. Appearance the assembled board is shown in fig. 8. covers. The electronic transformer is assembled on a board made of fiberglass laminated on one side with a thickness of 1.5 mm. All elements for surface mounting are installed on the side of printed conductors, output elements are on the opposite side of the board. Most of the parts (transistors VT1, VT2, transformer T1, dynistor VS1, capacitors C1-C5, C9, C10) will fit from cheap cheap electronic ballasts for fluorescent lamps type T8, for example, Tridonic PC4x18 T8, Fintar 236/418, Cimex CSVT 418P, Komtex EFBL236/418, TDM Electric EB-T8-236/418, etc., since they have similar circuitry and element base. Capacitors C9 and C10 - metal-film polypropylene, designed for high pulsed current and alternating voltage of at least 400 V. Diode VD4 - any high-speed diode with a permissible reverse voltage of at least 150 V in Fig. 11.

Rice. 6. Drawing of the printed circuit board of the first version of the electronic transformer

Rice. 7. Location of elements on the board

Rice. 8. Appearance of the assembled board

Transformer T1 is wound on an annular magnetic circuit with a magnetic permeability of 2300 ± 15%, its outer diameter is 10.2 mm, its inner diameter is 5.6 mm, and its thickness is 5.3 mm. Winding III (5-6) contains one turn, windings I (1-2) and II (3-4) - three turns of wire with a diameter of 0.3 mm. The inductance of windings 1-2 and 3-4 should be 10...15 µH. The output transformer T2 is wound on an EV25/13/13 (Epcos) magnetic circuit without a non-magnetic gap, N27 material. Its primary winding contains 76 turns of 5x0.2 mm wire. The secondary winding contains eight turns of 100x0.08 mm litz wire. The inductance of the primary winding is 12 ±10% mH. The inductor of the noise suppression filter L1 is wound on an E19/8/5 magnetic core, material N30, each winding contains 130 turns of wire with a diameter of 0.25 mm. You can use a standard two-winding choke with an inductance of 30 ... 40 mH that is suitable in size. Capacitors C1, C2, it is desirable to use the X-class.

A drawing of the printed circuit board of the second version of the electronic transformer (see Fig. 5) is shown in fig. 9, the location of the elements - in fig. 10. The board is also made of fiberglass foiled on one side, the elements for surface mounting are located on the side of the printed conductors, the output elements are on the opposite side. The appearance of the finished device is shown in Fig. 11 and fig. 12. The output transformer T1 is wound on a ring magnetic circuit R29.5 (Epcos), material N87. The primary winding contains 81 turns of wire with a diameter of 0.6 mm, the secondary - 8 turns of wire 3x1 mm. The inductance of the primary winding is 18 ±10% mH, the secondary is 200 ±10% mH. Transformer T1 was calculated for a maximum power of up to 150 W, to connect such a load, transistors VT1 and VT2 must be installed on a heat sink - an aluminum plate with an area of 16 ... 18 mm2, 1.5 ... 2 mm thick. In this case, however, a corresponding alteration of the printed circuit board will be required. Also, the output transformer can be used from the first version of the device (you will need to add holes on the board for a different pin arrangement). Transistors STD10NM60N (VT1, VT2) can be replaced with IRF740AS or similar. The Zener diode VD2 must have a power of at least 1 W, the stabilization voltage is 15.6 ... 18 V. Capacitor C12 is preferably disk ceramic for a rated DC voltage of 1000 V. Capacitors C13, C14 are metal-film polypropylene, designed for high pulse current and AC voltage of at least 400 V. Each of the resistive circuits R4-R7, R14-R17, R18-R21 can be replaced with one output resistor of the appropriate resistance and power, but this will require changing the printed circuit board.

Rice. 9. Drawing of the printed circuit board of the second version of the electronic transformer

Rice. 10. Location of elements on the board

Rice. 11. Appearance of the finished device

Rice. 12. Appearance of the assembled board

Literature

1. IR2161 (S) & (PbF). Halogen converter control IC. - URL: http://www.irf.com/product-info/datasheets/data/ir2161.pdf (24.04.15).

2. Peter Green. 100VA dimmable electronic converter for low voltage lighting. - URL: http://www.irf.com/technical-info/refdesigns/irplhalo1e.pdf (24.04.15).

3. Ferrites and accessories. - URL: http://en.tdk.eu/tdk-en/1 80386/tech-library/epcos-publications/ferrites (24.04.15).

Publication date: 30.10.2015

Readers' opinions

Veselin / 11/08/2017 - 22:18 Which electronic transformers on the market with them 2161 or similar
Eduard / 26.12.2016 - 13:07 Hello, is it possible to put 180W instead of a 160W transformer? Thank you.
Mikhail / 12/21/2016 - 10:44 pm I redid these http://ali.pub/7w6tj
Yuri / 05.08.2016 - 17:57 Hello! Is it possible to know the frequency AC voltage at the output of a transformer for halogen lamps? Thank you.

You can leave your comment, opinion or question on the above material:

www.radioradar.net

It happens that when assembling a particular device, you need to decide on the choice of power source. This is extremely important when devices need powerful block nutrition. It is not difficult to buy iron transformers with the necessary characteristics today. But they are quite expensive, and large size and weight are their main disadvantages. And the assembly and adjustment of good switching power supplies is a very complicated procedure. And a lot of people don't take it.

Next, you will learn how to assemble a powerful and at the same time simple power supply, taking an electronic transformer as the basis for the design. By and large, the conversation will be about increasing the power of such transformers.

For alteration, a 50-watt transformer was taken.

It was planned to increase its power to 300 watts. This transformer was purchased at a nearby store and cost about 100 rubles.

The standard transformer circuit looks like this:

The transformer is a conventional push-pull half-bridge autogenerator inverter. The symmetrical dinistor is the main triggering component of the circuit as it supplies the initial pulse.

The circuit uses 2 high-voltage reverse-conducting transistors.

The transformer circuit before rework contains the following components:

Transistors MJE13003.
Capacitors 0.1uF, 400V.
A transformer having 3 windings, two of which are master and have 3 turns of wire with a cross section of 0.5 sq. mm. Another one as current feedback.
The input resistor (1 ohm) is used as a fuse.
Diode bridge.

Despite the lack of protection against short circuit in this option, the electronic transformer works without failures. The purpose of the device is to work with a passive load (for example, office "halogen lamps"), so there is no stabilization of the output voltage.

As for the main power transformer, its secondary winding produces about 12 V.

Now take a look at the transformer circuit with increased power:

It has even fewer components. From the original circuit, a feedback transformer, a resistor, a dinistor and a capacitor were taken.

The remaining parts were removed from old computer PSUs, and these are 2 transistors, a diode bridge and a power transformer. Capacitors were purchased separately.

It does not hurt to replace the transistors with more powerful ones (MJE13009 in the TO220 package).

The diodes were replaced with a ready-made assembly (4 A, 600 V).

Diode bridges from 3 A, 400 V are also suitable. The capacitance should be 2.2 microfarads, but 1.5 microfarads is also possible.

The power transformer was removed from the 450W ATX PSU. All standard windings were removed from it and new ones were wound. The primary winding was wound with a triple wire of 0.5 sq. mm in 3 layers. The total number of turns is 55. It is necessary to monitor the accuracy of the winding, as well as its density. Each layer was insulated with blue electrical tape. The calculation of the transformer was carried out empirically, and the golden mean was found.

The secondary winding is wound at the rate of 1 turn - 2 V, but this is only if the core is the same as in the example.

Be sure to use a 40-60 W incandescent safety lamp when you turn it on for the first time.

It is worth noting that at the time of starting the lamp will not flash, since there are no smoothing electrolytes after the rectifier. The output is high frequency, so in order to make specific measurements, you must first rectify the voltage. For these purposes, a powerful dual diode bridge assembled from KD2997 diodes was used. The bridge can withstand currents up to 30 A if a heatsink is attached to it.

The secondary winding was supposed to be 15 V, although in reality it turned out a little more.

Everything that was at hand was taken as a load. This is a powerful lamp from a 400 W movie projector at a voltage of 30 V and 5 20-watt lamps at 12 V. All loads were connected in parallel.

Biometric lock - LCD layout and assembly

Electronic transformers began to come into vogue quite recently. In fact, it is a switching power supply, which is designed to lower mains 220 volts to 12 volts. Such transformers are used to power 12 volt halogen lamps. The power produced by ET today is 20-250 watts. The designs of almost all schemes of this kind are similar to each other. This is a simple half-bridge inverter, quite unstable in operation. The circuits are not protected against short circuit at the output of the pulse transformer. Another disadvantage of the circuit is that generation occurs only when a load of a certain magnitude is connected to the secondary winding of the transformer. I decided to write an article because I think that ET can be used in amateur radio structures as a power source, if some simple alternative solutions are introduced into the ET circuit. The essence of the alteration is to supplement the circuit with short circuit protection and force the ET to turn on when mains voltage is applied and without a light bulb at the output. In fact, the alteration is quite simple and does not require special skills in electronics. The diagram is shown below, in red - changes.

On the ET board, we can see two transformers - the main (power) and the OS transformer. The OS transformer contains 3 separate windings. Two of them are the basic windings of power switches and consist of 3 turns. On the same transformer there is another winding, which consists of only one turn. This winding is connected in series to the mains winding of the pulse transformer. It is this winding that must be removed and replaced with a jumper. Next, you need to look for a resistor with a resistance of 3-8 ohms (the protection against short circuit depends on its value). Then we take a wire with a diameter of 0.4-0.6 mm and wind two turns on the pulse transformer, then 1 turn on the OS transformer. We select the OS resistor with a power of 1 to 10 watts, it will heat up, and quite strongly. In my case, a 6.2 ohm wire resistor was used, but I do not advise using them, since the wire has some inductance, which may affect the further operation of the circuit, although I can’t say for sure - time will tell.

In the event of a short circuit at the output, protection will immediately work. The fact is that the current in the secondary winding of the pulse transformer, as well as on the windings of the OS transformer, will drop sharply, this will lead to blocking of the key transistors. To smooth out network noise, a choke is installed at the power input, which was soldered from another UPS. After the diode bridge, it is desirable to install an electrolytic capacitor with a voltage of at least 400 volts, select the capacitance based on the calculation of 1 μF per 1 watt.

But even after the alteration, you should not close the output winding of the transformer for more than 5 seconds, since the power switches will heat up and may fail. A pulsed PSU converted in this way will turn on without an output load at all. With a short circuit at the output, the generation breaks down, but the circuit will not suffer. The usual ET, when the output is closed, simply burns out instantly:

Continuing to experiment with blocks of electronic transformers for powering halogen lamps, you can modify the pulse transformer itself, for example, to obtain an increased bipolar voltage to power a car amplifier.

The transformer in the UPS of halogen lamps is made on a ferrite ring, and the desired watts can be squeezed out of this ring. All factory windings were removed from the ring and new ones were wound in their place. The output transformer must provide a bipolar voltage - 60 volts per arm.

To wind the transformer, a wire was used from Chinese conventional iron transformers (included in the set of the Sega set-top box). Wire - 0.4 mm. The primary winding is wound with 14 cores, first 5 turns around the entire ring, we do not cut the wire! After winding 5 turns, we make a tap, twist the wire and wind another 5. This solution will eliminate the difficult phasing of the windings. The primary winding is ready.

The secondary winds also. The winding consists of 9 strands of the same wire, one shoulder consists of 20 turns, it is also wound around the entire frame, then a tap and we wind another 20 turns.

To clean the varnish, I simply set fire to the wires with a lighter, then cleaned them with a mounting knife and wiped the tips with solvent. I must say - it works great! The output received the required 65 volts. In future articles, we will look at options of this kind, and also add a rectifier at the output, turning the ET into a full-fledged switching power supply that can be used for almost any purpose.

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