It is a small metal, usually aluminum case, the halves of which are fastened with just two rivets. However, some companies produce similar devices in plastic cases.

To see what's inside, these rivets can simply be drilled out. The same operation has to be done if alteration or repair of the device itself is planned. Although at its low price it is much easier to go and buy something else than to repair the old one. And yet there were many enthusiasts who not only managed to understand the device's structure, but also developed several on its basis.

The schematic diagram is not attached to the device, as well as to all current electronic devices. But the diagram is quite simple, contains a small amount of details and therefore schematic diagram an electronic transformer can be drawn from a printed circuit board.

Figure 1 shows a similarly removed diagram of a Taschibra transformer. Converters manufactured by Feron have a very similar circuit. The only difference is in the design of printed circuit boards and the types of parts used, mainly transformers: in Feron converters, the output transformer is made on a ring, while in Taschibra converters on an E-shaped core.

In both cases, the cores are made of ferrite. It should be noted right away that ring-shaped transformers with various modifications of the device lend themselves better to rewinding than W-shaped ones. Therefore, if an electronic transformer is purchased for experiments and alterations, it is better to buy a Feron device.

When using an electronic transformer only for power supply, the name of the manufacturer does not matter. The only thing you should pay attention to is the power: electronic transformers are available with a capacity of 60 - 250 watts.

Figure 1. Schematic of an electronic transformer from Taschibra

A brief description of the electronic transformer circuit, its advantages and disadvantages

As can be seen from the figure, the device is a push-pull autogenerator made according to a half-bridge circuit. Two legs of the bridge are Q1 and Q2, and the other two legs contain capacitors C1 and C2, therefore such a bridge is called a half-bridge.

One of its diagonals is supplied with mains voltage rectified by a diode bridge, and the other is loaded with a load. In this case it is primary winding output transformer. They are made according to a very similar scheme, but instead of a transformer, they include a choke, capacitors and filaments of fluorescent lamps.

Review of the popular Chinese electronic transformer TASCHIBRA. One fine day, a friend of mine brought a pulse electronic transformer for repair to power the halogen lamps used to power it. The repair was a quick replacement of the dinistor. After giving it to the owner. there was a desire to make the same block for myself. First, I found out where he bought it and bought it for later copying.

Technical data TASCHIBRA TRA25

• Input AC 220V 50/60 Hz.
• AC 12V output. 60W MAX.
• Protection class 1.

Electronic transformer circuit

More details of the diagram can be found List of parts for manufacturing:

1. n-p-n transistor 13003 2 pcs.
2. Diode 1N4007 4 pcs.
3. Film capacitor 10nF 100V 1 pc (C1).
4. Film capacitor 47nF 250V 2 pcs (C2, C3).
5. Dinistor DB3
6. Resistors:

• R1 22 ohm 0.25W
• R2 500 kOhm 0.25W
• R3 2.5 ohm 0.25W
• R4 2.5 ohm 0.25W

Manufacturing of a transformer on a W-shaped ferrite core from a computer power supply.

The primary winding contains a 1-core wire with a diameter of 0.5 mm, a length of 2.85 m and 68 turns. The standard secondary winding contains a 4-core wire with a diameter of 0.5 mm, length 33 cm and 8-12 turns. The winding of the transformer must be wound in one direction. Winding the choke on a ferrite ring with a diameter of 8 mm of the coil: 4 turns of the green wire, 4 turns of the yellow wire and an incomplete 1 (0.5) turn of the red wire.

Dinistor DB3 and its characteristics:

• (I open - 0.2 A), V 5 is the voltage in the open state;
• Average maximum allowable value when open: A 0.3;
• In the open state, the pulse current is A 2;
• Maximum voltage (during the closed state): V 32;
• Off-state current: μA - 10; the maximum impulse non-firing voltage is 5 V.

Here's a design. The view is certainly not very good, but I was convinced that you can assemble this switching power supply yourself.

Standard transformers assembled on electrical steel are no longer used in modern electronic radio equipment. Without exception, all modern TVs, computers, stereos and receivers have electronic transformers in their power supplies. There are several reasons for this:

Saving... At current prices for copper and steel, it is much cheaper to install a small board with a dozen parts and a small pulse transformer on a ferrite core.

Dimensions (edit)... An electronic transformer of a similar power will have a size 5 times smaller, and by the same amount less weight.

Stability... In ET, protection against short-circuits and overcurrent (except for cheap Chinese ones) is most often already built-in, and the input voltage range is 100-270 volts. Agree - not a single conventional transformer will give stability of output voltages with such a power spread.

Therefore, it is not surprising that radio amateurs have begun to increasingly use these switching voltage converters to power their homemade designs. As a rule, such ETs are produced at a voltage of 12V, but increase or decrease it, as well as add a few more additional voltages (for example, when creating a bipolar ULF power supply), you can wind up a few turns on the ferrite ring.

And you do not have to spend hundreds of meters of wire, since, unlike a conventional transformer on iron, there is about 1 turn per volt here. And in more powerful electronic transformers, half a turn or less - look at the photo below, where 60 and 160 watt transformers are shown.

In the first case, the 12-volt winding contains 12 turns, and in the second only 6. Therefore, to get 300 volts of the output voltage (for power supply tube amplifier), you will need to wind up only 150 turns. If you need to get a lower voltage than 12V, we make a tap from the standard winding. Typical:

Just keep in mind that most of these pulse transformers do not start with a load current of less than 1A. The minimum current may differ for different models. And here read more about the modifications of the Chinese ETs, allowing them to run even at low currents and are not afraid of short circuits.

About the power of electronic transformers. Do not trust too much what is written on the ET body. If it is marked as a 160-watt transformer, then already at 100 watts the heating will be such that there will be a risk of failure of the output key transistors. Therefore, mentally divide it in half. Or put transistors on normal heatsinks without forgetting about thermal grease.

Prices for electronic transformers are comparable to those for iron. So a 160-watt ET costs $ 5 in our electrical store, and a weaker 60-watt ET costs $ 3. In general, the only drawback of electronic transformers can be considered an increased level of RF interference and less reliability in operation. If you burned it, there is no point in repairing, the probability of a successful repair is not high (unless, of course, the problem is in the fuse at the 220V input). It's cheaper to just buy a new one.

Discuss the article ELECTRONIC LOWERING TRANSFORMER

Currently, 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 iron-based inductive transformers of the same capacity. Although electronic transformers from different companies may have different designs, the circuitry is practically the same.

Take, for example, a standard electronic transformer labeled 12V 50W, which is used to power a table lamp. The schematic diagram will be as follows:

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

Currently, the production of more advanced transformers with the IR2161 microcircuit has begun, which provides both the simplicity of the design of the electronic transformer and the reduction in the number of components used, and 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;
Swing the working frequency to reduce electromagnetic interference;
Micropower trigger 150 μA;
Possibility of use with phase controllers of brightness with control on the leading and trailing edges;
Output voltage offset compensation increases lamp life;
Soft start, eliminating current overloads of lamps.

Input resistor R1 (0.25 watts) is a kind of fuse. MJE13003 type transistors are pressed to the body through an insulating gasket with a metal plate. Even when operating at full load, the transistors do not heat up well. After the rectifier of the mains voltage, there is no capacitor that smooths out the ripples, therefore, the output voltage of the electronic transformer when operating on a load is rectangular oscillations of 40 kHz, modulated by ripples of the mains voltage of 50 Hz. Transformer T1 (feedback transformer) - on a ferrite ring, the windings connected to the bases of the transistors contain a couple of turns, the winding connected to the junction point of the emitter and collector of power transistors - 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 pulsed one, you need to connect a rectifier bridge on high-frequency high-power diodes to the output (ordinary KD202, D245 will not work) and a capacitor to smooth out the ripple. At the output of the electronic transformer, a diode bridge is installed on the diodes KD213, KD212 or KD2999. In short, diodes with a low forward voltage drop are needed, capable of working well at frequencies of the order of tens of kilohertz.

The converter of an electronic transformer does not work normally without a load, so it should be used where the load is constant in current and consumes enough current to confidently start the ET converter. When operating the circuit, it must be borne in mind that electronic transformers are sources of electromagnetic interference, therefore, an LC filter must be installed to prevent the penetration of interference into the network and into the load.

Personally, I used an electronic transformer to make a switching power supply for a tube amplifier. It is also possible to supply them with powerful class A ULFs or LED strips, which are just intended for sources with a voltage of 12V and a high output current. Naturally, the connection of such a tape is not made directly, but through a current-limiting resistor or by correcting the output power of an electronic transformer.

Discuss the article SCHEME OF ELECTRONIC TRANSFORMER FOR HALOGEN LAMPS

Fluorescent and halogen lamps are gradually becoming a thing of the past, giving way to LED lamps. In the lamps where they were used, unnecessary electronic transformers were left that were responsible for lighting these lamps. It seems that unnecessary - a place in the trash heap. But this is not the case. These transformers can be used to assemble powerful power supplies that can power power tools, LED strips, and more.

Electronic transformer device

The massive transformers we are accustomed to have recently begun to be replaced by electronic ones, which are distinguished by their low cost and compactness. The dimensions of the electronic transformer are so small that they are built into the housings of compact fluorescent lamps (CFLs).

All such transformers are made according to the same scheme, the differences between them are minimal. The circuit is based on a symmetrical oscillator, otherwise called a multivibrator.

They consist from a diode bridge, transistors and two transformers: matching and power... These are the main parts of the circuit, but not all. In addition to them, the circuit includes various resistors, capacitors and diodes.

Schematic diagram of an electronic transformer.

In this circuit, direct current from the diode bridge is fed to the transistors of the oscillator, which pump energy into the power transformer. The ratings and type of all radio components are selected so that a strictly defined voltage is obtained at the output.

If you turn on such a transformer without load, then the autogenerator will not start and there will be no voltage at the output.

DIY assembly

Electronic ballast can be bought in a store or found in your bins, but the most interesting option would be to assemble an electronic transformer with your own hands. It is assembled quite simply, and most of the necessary parts can be dig into broken power supplies and in energy-saving lamps.

• Required components: A diode bridge with a reverse voltage of at least 400 V and a current of at least 3 A or four diodes with the same characteristics.
• 5 amp fuse.
• Symmetrical dynistor DB3.
• 500 kΩ resistor.
• 2 resistors 2.2 Ohm, 0.5 W.
• 2 bipolar transistors MJE13009.
• 3 film capacitors 600 V, 100 nF.
• 2 toroidal cores.
• Lacquered wire 0.5 mm².
• Conventional insulated wire 2.5 mm².
• Radiator for transistors.
• Bread board.

It all starts with a breadboard, on which you will install all the radio components. On the market, you can buy two types of boards - with one-sided metallization on brown fiberglass.

And with double-sided end-to-end, on green.

The choice of the board depends on how much time and effort you will spend on assembling the project.

Brown boards are of disgusting quality. They are metallized in such a thin layer that gaps are visible in some places... It is poorly wetted with solder, even if you use a good flux. And everything that was soldered - comes off along with the metallization at the slightest effort.

Green ones cost one and a half to two times more, but everything is in order with the quality. Metallization on them with thickness has no problems. All holes in the board are tinned at the factory, due to which copper does not oxidize and problems do not arise during soldering.

You can find and buy these layouts both in the nearest radio store and on aliexpress. In China, they cost half the price, but delivery will have to wait.

Choose radio components with long leads, they will come in handy when installing the circuit. If you are going to use used parts, be sure to check their functionality and the absence of external damage.

The only detail you have to make yourself is the transformer.

The matching wire must be wound with a thin wire. Number of turns in each winding:

• I - 7 turns.
• II - 7.
• III - 3.

Do not forget to fix the windings with tape, otherwise they will creep.

The power transformer consists of only two windings. Wrap the primary with a 0.5mm² wire, and the secondary - 2.5mm². The primary and secondary housing consist of 90 and 12 turns, respectively.

For soldering, it is better not to use "old-fashioned" soldering irons - they can easily burn temperature-sensitive radioelements. Take a better soldering iron with power adjustment, they do not overheat, unlike the first ones.

install the transistors on the radiators in advance. Doing this on an already assembled board is extremely inconvenient. You need to assemble the diagram from small details to large ones. If you install the large ones first, they will get in the way when soldering the small ones. Consider this.

When assembling, look at the schematic diagram, all connections of radioelements must correspond to it. Slide the leads of the parts into the holes on the board and bend them in the desired direction. If the length is not enough, extend them with a wire. After soldering, glue the transformers to the board with epoxy resin.

After assembly, connect a load to the terminals of the device and make sure that it works.

Conversion into a power supply

It so happens that the batteries of the power tool fail, but there is no opportunity to buy a new one. In this case, an adapter in the form of a power supply will help. After a little modification, such an adapter can be assembled from an electronic transformer.

Details that will be needed for the rework:

• NTC thermistor 4 ohm.
• Capacitor 100 μF, 400 V.
• Capacitor 100 uF, 63V.
• Film capacitor 100 nF.
• 2 resistors 6.8 Ohm, 5 W.
• 500 ohm resistor, 2 W.
• 4 diodes KD213B.
• Radiator for diodes.
• Toroidal core.
• Wire with a cross section of 1.2 mm².
• A piece of a circuit board.

Before starting work, check if you have forgotten any part. If all parts are in place, start converting the electronic transformer into a power supply.

Solder a 400 V, 100 μF capacitor to the diode bridge output. To reduce the charging current of the capacitor, solder the thermistor into the break in the power wire. If you forget to do this, the diode bridge will burn out the first time you turn on the network.

Disconnect the second winding of the matching transformer and replace it with a jumper. Add one winding to both transformers. Make one turn on the matching one, and two on the power one. Connect the windings to each other by soldering two parallel-connected 6.8 Ohm resistors into the wire break.

To make a choke, wind 24 turns of 1.2 mm² wire around the core and secure it with tape. Then, on the breadboard, assemble the remaining radio components according to the diagram and connect the assembly to the main circuit. Remember to install diodes on the heatsink, when working under load, they get very hot.

Secure the entire structure in any suitable enclosure and the power supply can be considered assembled.

After final assembly, plug in the device and test its operation. It should give out a voltage of 12 volts. If the power supply gives them out, you did your job perfectly well. If it doesn't work, check if you took a non-working transformer.