How to make a power supply from energy-saving lamps. Power Sources Added parts are highlighted in red, these are

T transistors silicon structures n-p-n, high-voltage amplifying. The production of 13001 transistors is localized in Southeast Asia and India. They are used in low-power switching power supplies, chargers for various mobile phones, tablets, etc.

Attention! For close (almost ideal) common parameters, different manufacturers transistors 13001 can differ in the location of the pins.

Available in plastic cases TO-92, with flexible leads and TO-126 with rigid ones. The device type is indicated on the case.
The figure below shows the pinout of MJE13001 and 13001 from different manufacturers, with different cases.

The most important parameters.

Current transfer ratio 13001 may have from 10 before 70 , depending on the letter.
For MJE13001A - from 10 before 15 .
For MJE13001B - from 15 before 20 .
For MJE13001C - from 20 before 25 .
For MJE13001D - from 25 before 30 .
For MJE13001E - from 30 before 35 .
For MJE13001F - from 35 before 40 .
For MJE13001G - from 40 before 45 .
For MJE13001H - from 45 before 50 .
For MJE13001I - from 50 before 55 .
For MJE13001J - from 55 before 60 .
For MJE13001K - from 60 before 65 .
For MJE13001L - from 65 before 70 .

Cut-off frequency of current transfer - 8 MHz.

Maximum voltage collector - emitter - 400 V.

Maximum collector current (constant) - 200 ma.

Collector-emitter saturation voltage at collector current 50mA, base 10mA - 0,5 V.

Base-emitter saturation voltage at collector current 50mA, base 10mA - not higher 1,2 V.

Collector power dissipation- in TO-92 package - 0.75 W, in TO-126 package - 1.2 W without heatsink.

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Energy-saving lamps are widely used in everyday life and in production, over time they become unusable, and meanwhile, many of them can be restored after a simple repair. If the lamp itself failed, then from the electronic “stuffing” you can make a fairly powerful power supply for any desired voltage.

What does a power supply from an energy-saving lamp look like?

In everyday life, a compact, but at the same time powerful low-voltage power supply is often required; this can be done using a failed energy-saving lamp. In lamps, lamps most often fail, and the power supply remains in working order.

In order to make a power supply, you need to understand the principle of operation of the electronics contained in an energy-saving lamp.

Advantages of switching power supplies

In recent years, there has been a clear trend towards moving away from classic transformer power supplies to switching ones. This is due, first of all, to the large disadvantages of transformer power supplies, such as large mass, low overload capacity, low efficiency.

The elimination of these shortcomings in switching power supplies, as well as the development of the element base, made it possible to widely use these power units for devices with power from a few watts to many kilowatts.

Power Supply Diagram

The principle of operation of a switching power supply in an energy-saving lamp is exactly the same as in any other device, for example, in a computer or TV.

In general terms, the operation of a switching power supply can be described as follows:

Alternating mains current is converted into direct current without changing its voltage, i.e. 220 V.
A transistor-based pulse-width converter converts a DC voltage into rectangular pulses, with a frequency of 20 to 40 kHz (depending on the lamp model).
This voltage is fed through the choke to the lamp.

Consider the scheme and operation of the switching lamp power supply (figure below) in more detail.

Scheme of the electronic ballast of an energy-saving lamp

The mains voltage is supplied to the bridge rectifier (VD1-VD4) through a limiting resistor R 0 of small resistance, then the rectified voltage is smoothed on the filtering high-voltage capacitor (C 0), and through the smoothing filter (L0) is fed to the transistor converter.

The start of the transistor converter occurs at the moment when the voltage across the capacitor C1 exceeds the opening threshold of the VD2 dinistor. This will start the generator on transistors VT1 and VT2, due to which auto-generation occurs at a frequency of about 20 kHz.

Other circuit elements such as R2, C8 and C11 play a supporting role, making it easier to start the generator. Resistors R7 and R8 increase the closing speed of the transistors.

And the resistors R5 and R6 serve as limiting resistors in the transistor base circuits, R3 and R4 protect them from saturation, and in the event of a breakdown they play the role of fuses.

Diodes VD7, VD6 are protective, although in many transistors designed to work in such devices, such diodes are built-in.

TV1 is a transformer, from its windings TV1-1 and TV1-2, the feedback voltage from the generator output is fed into the base transistor circuits, thereby creating conditions for the generator to work.

In the figure above, the parts to be removed when reworking the block are highlighted in red, points A–A` must be connected with a jumper.

Block rework

Before proceeding with the alteration of the power supply, you should decide what current power you need to have at the output, the depth of modernization will depend on this. So, if a power of 20-30 W is required, then the alteration will be minimal and will not require much intervention in the existing circuit. If you need to get a power of 50 or more watts, then a more thorough upgrade will be required.

It should be borne in mind that the output of the power supply will be a constant voltage, not an alternating one. It is impossible to get an alternating voltage with a frequency of 50 Hz from such a power supply.

We determine the power

Power can be calculated using the formula:

Р – power, W;

I - current strength, A;

U - voltage, V.

For example, let's take a power supply with the following parameters: voltage - 12 V, current - 2 A, then the power will be:

Taking into account the overload, 24-26 W can be accepted, so that the manufacture of such a unit will require minimal intervention in the circuit of a 25 W energy-saving lamp.

New details

Adding New Parts to a Schematic

Added parts are highlighted in red, these are:

diode bridge VD14-VD17;
two capacitors C 9, C 10;
additional winding placed on the L5 ballast choke, the number of turns is selected empirically.

The added winding to the inductor plays another important role of an isolation transformer, preventing mains voltage from entering the output of the power supply.

To determine the required number of turns in the added winding, do the following:

a temporary winding is wound on the inductor, about 10 turns of any wire;
connected to a load resistance, with a power of at least 30 W and a resistance of about 5-6 ohms;
plug into the network, measure the voltage at the load resistance;
the resulting value is divided by the number of turns, find out how many volts per 1 turn;
calculate the required number of turns for a permanent winding.

A more detailed calculation is given below.

Test inclusion of a converted power supply

After that, it is easy to calculate the required number of turns. To do this, the voltage that is planned to be received from this block is divided by the voltage of one turn, the number of turns is obtained, about 5-10% is added to the result obtained in reserve.

W \u003d U out / U vit, where

W is the number of turns;

U out - the required output voltage of the power supply;

U vit - voltage per turn.

Winding an additional winding on a standard choke

The original inductor winding is under mains voltage! When winding an additional winding over it, it is necessary to provide interwinding insulation, especially if a PEL-type wire is wound in enamel insulation. For winding insulation, you can use PTFE thread sealing tape, which is used by plumbers, its thickness is only 0.2 mm.

The power in such a block is limited by the overall power of the transformer used and the allowable current of the transistors.

High Power Power Supply

This will require a more complex upgrade:

additional transformer on a ferrite ring;
replacement of transistors;
installation of transistors on radiators;
increasing the capacitance of some capacitors.

As a result of such an upgrade, a power supply unit with a power of up to 100 W is obtained, with an output voltage of 12 V. It is capable of providing a current of 8-9 amperes. This is enough to power, for example, a medium power screwdriver.

The diagram of the upgraded power supply is shown in the figure below.

100 W power supply

As you can see in the diagram, the resistor R 0 has been replaced with a more powerful one (3-watt), its resistance has been reduced to 5 ohms. It can be replaced by two 2-watt 10 ohm ones by connecting them in parallel. Further, C 0 - its capacitance is increased to 100 microfarads, with an operating voltage of 350 V. If it is undesirable to increase the dimensions of the power supply, then you can find a miniature capacitor of this capacity, in particular, you can take it from a soap camera.

To ensure reliable operation of the unit, it is useful to slightly reduce the values of the resistors R 5 and R 6, up to 18–15 Ohms, and also increase the power of the resistors R 7, R 8 and R 3, R 4. If the generation frequency turns out to be low, then the values \u200b\u200bof the capacitors C 3 and C 4 - 68n should be increased.

The most difficult may be the manufacture of the transformer. For this purpose, in impulse blocks, ferrite rings of appropriate sizes and magnetic permeability are most often used.

The calculation of such transformers is quite complicated, but there are many programs on the Internet with which it is very easy to do this, for example, "Lite-CalcIT Pulse Transformer Calculation Program".

What does a pulse transformer look like?

The calculation carried out using this program gave the following results:

For the core, a ferrite ring is used, its outer diameter is 40, its inner diameter is 22, and its thickness is 20 mm. The primary winding with PEL wire - 0.85 mm 2 has 63 turns, and two secondary ones with the same wire - 12.

The secondary winding must be wound in two wires at once, while it is advisable to first slightly twist them together along the entire length, since these transformers are very sensitive to the asymmetry of the windings. If this condition is not observed, then the VD14 and VD15 diodes will heat up unevenly, and this will further increase the asymmetry, which, in the end, will disable them.

But such transformers easily forgive significant errors when calculating the number of turns, up to 30%.

Since this circuit was originally designed to work with a 20 W lamp, transistors 13003 were installed. In the figure below, position (1) is medium power transistors, they should be replaced with more powerful ones, for example, 13007, as in position (2). They may have to be installed on a metal plate (radiator), with an area of \u200b\u200babout 30 cm 2.

Trial

A trial run should be carried out with some precautions in order not to damage the power supply:

The first test switching on should be done through a 100 W incandescent lamp in order to limit the current to the power supply.
Be sure to connect a load resistor of 3-4 ohms, with a power of 50-60 watts, to the output.
If everything went well, let it run for 5-10 minutes, turn it off and check the degree of heating of the transformer, transistors and rectifier diodes.

If no mistakes were made during the replacement of parts, the power supply should work without problems.

If the trial run showed the unit to work, it remains to test it in full load mode. To do this, reduce the resistance of the load resistor to 1.2-2 ohms and plug it into the network directly without a light bulb for 1-2 minutes. Then turn off and check the temperature of the transistors: if it exceeds 60 0 C, then they will have to be installed on radiators.

As a radiator, you can use both a factory radiator, which will be the most correct solution, and an aluminum plate with a thickness of at least 4 mm and an area of 30 sq.cm. Under the transistors it is necessary to put a mica gasket, they must be fixed to the radiator with screws with insulating bushings and washers.

Lamp block. Video

How to make a switching power supply from an economy lamp, see the video below.

You can make a switching power supply from the ballast of an energy-saving lamp with your own hands, having minimal skills in working with a soldering iron.

Most modern network chargers are assembled according to the simplest pulse circuit, on one high-voltage transistor (Fig. 1) according to the blocking generator circuit.

Unlike simpler circuits based on a 50 Hz step-down transformer, the transformer for pulse converters of the same power is much smaller in size, which means that the dimensions, weight and price of the entire converter are smaller. In addition, pulse converters are safer - if in a conventional converter, in the event of a failure of power elements, a high unstabilized (and sometimes even alternating) voltage from the secondary winding of the transformer gets into the load, then in case of any malfunction of the “pulse” (except for the failure of the reverse optocoupler connections - but it is usually very well protected) there will be no voltage at all at the output.

Rice. 1
A simple pulsed blocking oscillator circuit

A detailed description of the principle of operation (with pictures) and calculation of the circuit elements of a high-voltage pulse converter (transformer, capacitors, etc.) can be found, for example, in "TEA152x Efficient Low Power Voltage supply" at http://www. nxp.com/acrobat/applicationnotes/AN00055.pdf (in English).

The alternating mains voltage is rectified by the VD1 diode (although sometimes the generous Chinese put as many as four diodes in a bridge circuit), the current pulse when turned on is limited by the resistor R1. Here it is desirable to put a resistor with a power of 0.25 W - then, when overloaded, it will burn out, performing the function of a fuse.

The converter is assembled on a transistor VT1 according to the classic flyback circuit. Resistor R2 is needed to start generation when power is applied, it is optional in this circuit, but the converter works a little more stable with it. Generation is supported by the capacitor C1, included in the PIC circuit on the winding, the generation frequency depends on its capacitance and the parameters of the transformer. When the transistor is unlocked, the voltage at the lower terminals of the windings / and II is negative, at the upper ones it is positive, the positive half-wave through the capacitor C1 opens the transistor even more strongly, the voltage amplitude in the windings increases ... That is, the transistor opens like an avalanche. After some time, as the capacitor C1 charges, the base current begins to decrease, the transistor begins to close, the voltage at the top output of the winding II according to the circuit begins to decrease, through the capacitor C1 the base current decreases even more, and the transistor closes like an avalanche. Resistor R3 is needed to limit the base current during circuit overloads and surges in the AC mains.

At the same time, the amplitude of the self-induction EMF through the VD4 diode recharges the capacitor C3 - therefore, the converter is called a flyback. If you swap the terminals of the winding III and recharge the capacitor C3 during the forward stroke, then the load on the transistor will increase sharply during the forward stroke (it may even burn out due to too much current), and during the reverse stroke, the self-induction EMF will be unspent and will be allocated to collector junction of the transistor - that is, it can burn out from overvoltage. Therefore, in the manufacture of the device, it is necessary to strictly observe the phasing of all windings (if you confuse the terminals of winding II, the generator simply will not start, since the capacitor C1 will, on the contrary, disrupt generation and stabilize the circuit).

The output voltage of the device depends on the number of turns in the windings II and III and on the stabilization voltage of the Zener diode VD3. The output voltage is equal to the stabilization voltage only if the number of turns in the windings II and III is the same, otherwise it will be different. During the reverse stroke, the capacitor C2 is recharged through the diode VD2, as soon as it is charged to about -5 V, the zener diode will begin to pass current, the negative voltage at the base of the transistor VT1 will slightly reduce the amplitude of the pulses on the collector, and the output voltage will stabilize at a certain level. The stabilization accuracy of this circuit is not very high - the output voltage varies within 15 ... 25%, depending on the load current and the quality of the VD3 zener diode.
A diagram of a better (and more complex) converter is shown in rice. 2

Rice. 2
Electrical circuit more complex
converter

To rectify the input voltage, a diode bridge VD1 and a capacitor are used, the resistor must have a power of at least 0.5 W, otherwise, at the moment of switching on, when charging the capacitor C1, it may burn out. The capacitance of capacitor C1 in microfarads should be equal to the power of the device in watts.

The converter itself is assembled according to the already familiar scheme on the transistor VT1. The emitter circuit includes a current sensor on the resistor R4 - as soon as the current flowing through the transistor becomes so large that the voltage drop across the resistor exceeds 1.5 V (with the resistance indicated on the circuit - 75 mA), the transistor VT2 opens slightly through the diode VD3 and limits the base the current of the transistor VT1 so that its collector current does not exceed the above 75 mA. Despite its simplicity, such a protection scheme is quite effective, and the converter turns out to be almost eternal even with short circuits in the load.

To protect the transistor VT1 from self-induction EMF emissions, a smoothing circuit VD4-C5-R6 is added to the circuit. Diode VD4 must be high-frequency - ideally BYV26C, a little worse - UF4004-UF4007 or 1 N4936, 1 N4937. If there are no such diodes, it is better not to install a chain at all!

Capacitor C5 can be anything, however, it must withstand a voltage of 250 ... 350 V. Such a chain can be installed in all similar circuits (if it is not there), including in a circuit according to rice. 1- it will significantly reduce the heating of the body of the key transistor and significantly "prolong the life" of the entire converter.

Stabilization of the output voltage is carried out using the Zener diode DA1, standing at the output of the device, galvanic isolation is provided by the V01 optocoupler. The TL431 chip can be replaced with any low-power zener diode, the output voltage is equal to its stabilization voltage plus 1.5 V (voltage drop across the V01 optocoupler LED) ', a small resistance resistor R8 is added to protect the LED from overloads. As soon as the output voltage becomes slightly higher than the set value, a current will flow through the zener diode, the optocoupler LED will start to glow, its phototransistor will open slightly, the positive voltage from the capacitor C4 will slightly open the transistor VT2, which will reduce the amplitude of the collector current of the transistor VT1. The instability of the output voltage of this circuit is less than that of the previous one, and does not exceed 10 ... 20%, also, thanks to the capacitor C1, there is practically no background of 50 Hz at the output of the converter.

It is better to use an industrial transformer in these circuits, from any similar device. But you can wind it yourself - for an output power of 5 W (1 A, 5 V), the primary winding should contain approximately 300 turns of wire with a diameter of 0.15 mm, winding II - 30 turns of the same wire, winding III - 20 turns of wire with a diameter of 0 .65 mm. Winding III must be very well isolated from the first two, it is advisable to wind it in a separate section (if any). The core is standard for such transformers, with a dielectric gap of 0.1 mm. In extreme cases, you can use a ring with an outer diameter of approximately 20 mm.
Download: Basic circuits of switching network adapters for charging phones
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The switching regulator circuit is not much more complicated than the usual one used in transformer power supplies, but more difficult to set up.

Therefore, insufficiently experienced radio amateurs who do not know the rules for working with high voltage (in particular, never work alone and never tune the device with two hands - only one!), I do not recommend repeating this scheme.

On fig. 1 shows the electrical circuit of a switching voltage regulator for charging cell phones.

Rice. 1 The electrical circuit of the switching voltage stabilizer

The circuit is a blocking oscillator implemented on a transistor VT1 and a transformer T1. The diode bridge VD1 rectifies the alternating mains voltage, the resistor R1 limits the current pulse when turned on, and also acts as a fuse. Capacitor C1 is optional, but thanks to it, the blocking oscillator works more stably, and the heating of transistor VT1 is slightly less (than without C1).

When the power is turned on, the transistor VT1 opens slightly through the resistor R2, and a small current begins to flow through the I winding of the transformer T1. Due to inductive coupling, current also begins to flow through the remaining windings. At the upper (according to the diagram) terminal of winding II, a small positive voltage is applied, it opens the transistor even more through the discharged capacitor C2, the current in the transformer windings increases, and as a result, the transistor opens completely, to saturation.

After a while, the current in the windings stops increasing and starts to decrease (transistor VT1 is fully open all this time). The voltage on the winding II decreases, and through the capacitor C2, the voltage at the base of the transistor VT1 decreases. It begins to close, the voltage amplitude in the windings decreases even more and changes the polarity to negative.

Then the transistor is completely closed. The voltage on its collector increases and becomes several times greater than the supply voltage (inductive surge), however, thanks to the R5, C5, VD4 chain, it is limited to a safe level of 400 ... 450 V. Thanks to the R5, C5 elements, the generation is not completely neutralized, and through for some time, the polarity of the voltage in the windings changes again (according to the principle of operation of a typical oscillatory circuit). The transistor starts to turn on again. This continues indefinitely in a cyclic mode.

On the remaining elements of the high-voltage part of the circuit, a voltage regulator and a node for protecting the transistor VT1 from overcurrent are assembled. Resistor R4 in the circuit under consideration acts as a current sensor. As soon as the voltage drop across it exceeds 1 ... 1.5 V, the transistor VT2 opens and closes the base of the transistor VT1 to the common wire (forces it to close). Capacitor C3 speeds up the reaction VT2. Diode VD3 is necessary for the normal operation of the voltage regulator.

The voltage regulator is assembled on a single chip - an adjustable zener diode DA1.

For galvanic isolation of the output voltage from the mains, optocoupler VOL is used. The operating voltage for the transistor part of the optocoupler is taken from winding II of transformer T1 and smoothed by capacitor C4. As soon as the voltage at the output of the device becomes greater than the nominal, a current will begin to flow through the zener diode DA1, the optocoupler LED will light up, the collector-emitter resistance of the phototransistor VOL2 will decrease, the transistor VT2 will open slightly and reduce the voltage amplitude based on VT1.

It will open more weakly, and the voltage on the transformer windings will decrease. If the output voltage, on the contrary, becomes less than the nominal one, then the phototransistor will be completely closed and the transistor VT1 will "swing" in full force. To protect the zener diode and the LED from overcurrent, it is advisable to include a resistor with a resistance of 100 ... 330 Ohm in series with them.

Establishment
The first stage: it is recommended to turn on the device for the first time through a 25 W, 220 V lamp, and without capacitor C1. The engine of the resistor R6 is set to the lower (according to the diagram) position. The device is turned on and immediately turned off, after which the voltages on the capacitors C4 and Sb are measured as quickly as possible. If there is a slight voltage on them (according to the polarity!), It means that the generator has started, if not, the generator does not work, you need to search for an error on the board and installation. In addition, it is advisable to check the transistor VT1 and resistors R1, R4.

If everything is correct and there are no errors, but the generator does not start, swap the terminals of the winding II (or I, but not both at once!) And check the performance again.

The second stage: turn on the device and control with a finger (only not by the metal pad for heat dissipation) the heating of the VTI transistor, it should not heat up, the 25 W light bulb should not glow (the voltage drop on it should not exceed a couple of Volts).

Connect some small low-voltage lamp to the output of the device, for example, designed for a voltage of 13.5 V. If it does not light up, swap the terminals of the winding III.

And at the very end, if everything is working fine, they check the performance of the voltage regulator by rotating the engine of the tuning resistor R6. After that, you can solder the capacitor C1 and turn on the device without a current-limiting lamp.

The minimum output voltage is about 3 V (the minimum voltage drop at the DA1 pins exceeds 1.25 V, at the LED pins-1.5 V).
If you need a lower voltage, replace the Zener diode DA1 with a resistor with a resistance of 100 ... 680 Ohms. The next setting step requires setting the output voltage of the device to 3.9 ... 4.0 V (for a lithium battery). This device charges the battery with an exponentially decreasing current (from about 0.5 A at the beginning of the charge to zero at the end (for a lithium battery with a capacity of about 1 Ah, this is acceptable)). In a couple of hours of charging mode, the battery gains up to 80% of its capacity.

About details
A special structural element is a transformer.
The transformer in this circuit can only be used with a split ferrite core. The operating frequency of the converter is quite large, so only ferrite is needed for transformer iron. And the converter itself is single-cycle, with constant bias, so the core must be split, with a dielectric gap (one or two layers of thin transformer paper are laid between its halves).

It is best to take a transformer from an unnecessary or faulty similar device. In extreme cases, you can wind it yourself: core section 3 ... 5 mm2, winding I-450 turns with a wire with a diameter of 0.1 mm, winding II-20 turns with the same wire, winding III-15 turns with a wire with a diameter of 0.6 .. .0.8 mm (for output voltage 4...5 V). When winding, strict observance of the direction of winding is required, otherwise the device will work poorly, or will not work at all (you will have to make efforts when adjusting - see above). The beginning of each winding (in the diagram) is at the top.

Transistor VT1 - any power of 1 W or more, collector current of at least 0.1 A, voltage of at least 400 V. Current gain b2b must be greater than 30. Ideal transistors are MJE13003, KSE13003 and all other types 13003 of any company. As a last resort, domestic transistors KT940, KT969 are used. Unfortunately, these transistors are designed for a voltage limit of 300 V, and at the slightest increase in the mains voltage above 220 V, they will break through. In addition, they are afraid of overheating, i.e., they need to be installed on a heat sink. For transistors KSE13003 and MGS13003, a heat sink is not needed (in most cases, the pinout is like that of domestic KT817 transistors).

Transistor VT2 can be any low-power silicon, the voltage on it should not exceed 3 V; the same applies to the diodes VD2, VD3. Capacitor C5 and diode VD4 must be rated for a voltage of 400 ... 600 V, diode VD5 must be rated for the maximum load current. The diode bridge VD1 must be designed for a current of 1 A, although the current consumed by the circuit does not exceed hundreds of milliamps - because when turned on, a rather powerful current surge occurs, and it is impossible to increase the resistance of the resistor Ш to limit the amplitude of this surge - it will get very hot.

Instead of the VD1 bridge, you can put 4 diodes of the type 1N4004 ... 4007 or KD221 with any letter index. Stabilizer DA1 and resistor R6 can be replaced with a zener diode, the voltage at the output of the circuit will be 1.5 V more than the stabilization voltage of the zener diode.

The "common" wire is shown in the diagram only to simplify the graphics, it must not be grounded and (or) connected to the device case. The high voltage part of the device must be well insulated.

Decor
The elements of the device are mounted on a board made of foil fiberglass in a plastic (dielectric) case, in which two holes are drilled for indicator LEDs. A good option (used by the author) is to design the device board in a case from a used A3336 battery (without a step-down transformer).

Everyone knows that there is such an operation as pre-sale preparation of goods. A simple but very necessary step. By analogy with it, I have long been using pre-operational preparation of all purchased Chinese-made goods. There is always the possibility of refinement in these products, and I note that it is really necessary, which is a consequence of the manufacturer's savings on high-quality material of its individual elements or not installing them at all. I will allow myself to be suspicious and suggest that all this is not accidental, but is a constituent element of the manufacturer's policy aimed ultimately at reducing the service life of the manufactured goods, which results in an increase in sales. Having decided on the active use of a miniature electric massager (of course, made in China), I immediately drew attention to its power supply, which looks like a mobile phone charger, and even with the inscription COURIER CHARGER- mobile charger. Having an OUTPUT of 5 volts and 500 mA. Without even being convinced of its serviceability, I took it apart and looked at the contents.

The electronic components installed on the board, and especially the zener diode at the output, indicated that this was indeed a power supply. By the way, the absence of a diode bridge is not a positive thing.

The connected load, in the form of two 2.5 V bulbs in series, with a current consumption of 150 mA, detected 5.76 V at the output. anything else, in this particular case, is clearly useless.

I preferred to search for a circuit on the Internet to draw in, according to a previously taken photo, a printed circuit board with electronic components located on it.

Adapter diagram and rework

The image of the printed circuit board made it possible to draw an existing power supply circuit. The CHY 1711 transistor optocoupler, C945, S13001 transistors and other components did not allow me to call the circuit primitive, but with the existing ratings of some components and the absence of others, it did not suit me.

A 160 mA fuse was introduced into the new circuit, and instead of the existing rectifier, a diode bridge consisting of 4 1N4007 diodes. The value of the zener diode VD3 controlling the optocoupler has been changed from 4V6 to 3V6, which should reduce the output voltage to the desired one.

There was enough free space on the board so that it was not difficult to implement the planned changes. The newly assembled power supply had an output voltage of almost 4.5 volts.

And current output up to 300 mA inclusive.

As a result, some additional electronic components and time devoted to interesting work gave me the opportunity to have a decent power supply, which I hope will serve faithfully for a long time. Babay was engaged in debugging the PSU.