Bp from the ballast of an economy lamp, the capacitors are heated. Charger from economy lamp. High Power Power Supply

Sometimes it becomes necessary to have impulse block medium power supply. Network power supplies using an iron transformer are very huge. But besides the heavy weight, they have another hidden drawback. If you are planning to assemble a power amplifier with a mains power supply (a 50Hz transformer), then you should take into account that after the diode bridge the voltage must be filtered.

You can smooth out high-frequency network ripples with chokes, and high frequencies do not greatly affect the sound of the amplifier. Another thing is low-frequency interference. In modern electronics, it is customary to use smoothing filters, which consist of capacitors (both constant and variable). The quality of the output voltage depends on the total capacitance of these filters. The main interference is transformed from the mains, if the mains voltage rating changes, then the rating at the output of the transformer will change accordingly. In switching power supplies, everything is different. Such power supplies operate at higher frequencies, have a separate generator, control circuit, etc.

This makes it possible to obtain a voltage at the output, the value of which is in no way connected with the mains, such a unit will give a stable output voltage if the input voltage ranges from 90 to 280 volts.

Electronic ballast (ballast from LDS) used at 40 watts from a Chinese manufacturer. The transformer is a ferrite ring, the dimensions in my case are 25.4mm (Outer Diameter) x 15.5mm (Inner Diameter) x 8.5mm (Thickness). The dimensions of the specified transformer are not critical and deviations (plus / minus 50%) are permissible.

The primary winding consists of 100 turns of wire with a diameter of 0.3-0.7mm (0.6mm in my case). The secondary is wound based on needs. To obtain 12 volts, the secondary winding contains 7-8 turns. The current in the secondary winding can reach up to 4 amperes (at a voltage of 12 volts).

One of the output wires of the ballast is connected directly to the transformer, the other through a capacitor (capacitance and voltage of the latter are not critical).
The voltage of the capacitor (C6) can be in the range of 500-5000 Volts (in my case 1600 Volts). It is desirable to select the capacity, the value of the current supplied to the winding depends on it. In my case, the capacitor is used at 6800pF.

Such a unit can be used for almost any purpose, it is not afraid of a short circuit at the output (as is common with other UPSs), but you should not close the winding to for a long time. Works very stably and silently, has the small weight and the compact sizes.

The ballast of an energy-saving lamp (LDS control circuit or simply electronic ballast) is a network UPS, which is designed to increase the mains 220 volts to the desired rating to power the lamp. Schemes of such ballasts work for a long time and reliably, but there are exceptions. Ballasts can have a wide variety of circuits, from which we have selected the most common circuits. The essence of the article is to explain the main problems of such ballasts and offer a variant of strengthening the circuit.

The experimental ballast itself was bought in a store specifically for this article. First, let's look at the design of the ballast.

So, the ballast is designed to power the LDS with a power of 40 watts. Several types of such ballasts are produced. Basically, they are for LDS with a power of 20 or 40 watts, for both one and two lamps (for example, 2x20 or 2x40). The case is quite convenient for installation, it can be attached to literally any surface. We open the case. The pay is amazing! Chinese manufacturers have been pleasantly surprising lately, the assembly is elegant. The built-in line filter at the power input immediately catches the eye. In the mains filter circuit, you can see two chokes, a mains fuse, smoothing capacitors and a thermistor. This is all rather strange if we are talking about the Chinese manufacturer, and you will soon understand why I was so surprised.

The fact is that a completely similar ballast for 40 watts from the same store was bought a few days ago. In the purchased ballast, there was a completely different scheme. The assembly also shines with neatness, but once you take a closer look, it becomes clear that the number of components used is kept to a minimum. No mains filter, just a bare diode rectifier. Cheaper and less power transistors 13003, but back to our scheme. After the mains filter, we see a rectifier, after which there are two 250 Volt 10 microfarad electrolytes. Transistors used are more powerful - 13007 with additional cooling. Each transistor has an additional protective diode. The master windings are wound on a ferrite ring, the ring itself is fixed on a small stand.

Next comes storage chokes. It is hard to see from the photographs, but they are additionally varnished, so that if you decide to disassemble such a throttle, then nothing will work. In addition, the electrical circuit has several protections; in the event of a short circuit, the basic limiting resistors will go out of service, and in very rare cases, transistors. Repairing such a ballast is not difficult. To power the ballast, you just need to change the electrolytic capacitors.

By increasing their capacitance, you can achieve an increase in the overall power of the circuit. In such control schemes, everything is provided with a margin, so that the replacement of electrolytic capacitors will not lead to undesirable consequences. In my case, the 10 uF capacitors were replaced with 15 uF, you can increase it to 25 uF, I didn’t try further.

Such a replacement increases the current consumption of the circuit, which leads to an increase in output power. The circuit before and after the replacement was used to power the horizontal transformer, the result is obvious! With factory capacitors, the power sometimes reaches 60 watts, when replaced, it increases to 80 watts (using 15uF capacitances). At the same time, I must say that the transistors are already starting to heat up and it is advisable to change the heat sinks to larger ones. And in our next articles, we will consider the option of manufacturing a pulsed PSU using LDS control circuits. Such a power supply will be better than some factory ones, on this I say goodbye to you. AKA KASYAN

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 is out of order, then from the electronic "stuffing" you can make quite powerful block 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 last 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 - transformer, from its windings TV1-1 and TV1-2, voltage feedback from the output of the generator is fed into the base circuits of transistors, thereby creating conditions for the operation of the generator.

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. Get from such a power supply AC voltage 50 Hz is not possible.

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:

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

1. The first test switching on should be done through a 100 W incandescent lamp in order to limit the current to the power supply.
2. Be sure to connect a load resistor of 3-4 ohms, with a power of 50-60 watts, to the output.
3. 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 heatsink, can be used as a factory heatsink, which will be the most right decision, 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.

A fluorescent lamp is a rather complex mechanism. In design energy saving lamps there are many different small components that together provide the lighting that such a device produces. The basis of the entire design of energy-saving devices is a glass tube filled with mercury vapor and an inert gas.

Impulse block and its purpose

Electrodes, cathode and anode are installed at both ends of this tube. After applying current to them, they begin to heat up. Having reached the required temperature, they release electrons that hit the mercury molecules and it begins to emit ultraviolet light.

Ultraviolet is converted into a spectrum visible to the human eye thanks to the phosphor, which is located in the tube. Thus, the lamp lights up after a while. Typically, the rate of ignition of the lamp depends on the period of its development. The longer the lamp has been on, the longer the interval between switching on and full ignition will be.

To understand the purpose of each of the UPS components, it is necessary to analyze separately what functions they perform:

• R0 - works as a limiter and fuse for the power supply. It stabilizes and stops the excess power supply current at the moment of turn-on, which flows through the diodes of the rectifier.
• VD1, VD2, VD3, VD4 - are used as bridge rectifiers.
• L0, C0 - filter the current supply and make it without drops.
• R1, C1, VD8 and VD2 - the starting circuit of the converters. The launch process is as follows. The charging source for capacitor C1 is the first resistor. After the capacitor gains such power that it is able to break through the VD2 dinistor, it opens on its own and simultaneously opens the transistor, which causes self-oscillation in the circuit. Then a rectangular pulse is sent to the cathode of the VD8 diode and the resulting negative indicator closes the second dinistor.
• R2, C11, C8 - make the starting process of converters easier.
• R7, R8 - Make the closing of transistors more efficient.
• R6, R5 - create boundaries for the current at the bases of each transistor.
• R4, R3 - work as fuses in the event of a sharp increase in voltage in transistors.
• VD7 VD6 - protect each power supply transistor from return current.
• TV1 is a reverse transformer for communication.
• L5 - ballast choke.
• C4, C6 - separation capacitors, where all voltage and power is divided in half.
• TV2 is a transformer for creating impulses.
• VD14, VD15 - diodes operating on pulses.
• C9, C10 - filter capacitors.

Thanks to the correct placement and careful selection of the characteristics of all the listed components, we get the power supply we need the power for further use.

Differences in the design of the lamp from the impulse block

It is very similar in structure to a switching power supply, which is why you can make a switching power supply very easily and quickly. For alteration, it is necessary to install a jumper and additionally install a transformer that generates pulses and is equipped with a rectifier.

To facilitate the UPS, the glass cover has been removed. Fluorescent Lamp and some of the structural components that have been replaced with a special connector. You may have noticed that it only takes a few steps to change. simple operations, and this will be enough.

Board with energy-saving lamp

The output power rating is limited by the size of the transformer used, the maximum possible throughput rating of the main transistors, and the dimensions of the cooling system. To increase the power a little, it is enough to wind more windings on the inductor.

pulse transformer

The main key characteristic of a switching power supply is the ability to adapt to the performance of the transformer used in the design. And the fact that the reverse current does not need to pass through the transformer, which we made ourselves, makes it much easier for us to calculate the rated power of the transformer.

Thus, most of the errors in the calculation become insignificant due to the use of such a scheme.

We calculate the capacitance of the required voltage

To save money, capacitors with a small capacitance index are used. It is from them that the ripple of the input voltage will depend. To reduce the ripple, it is necessary to increase the volume of capacitors, it is also done to increase the ripple index only in the reverse order.

To reduce the size and improve the compactness, it is possible to use capacitors on electrolytes. For example, you can use such capacitors that are built into photographic equipment. They have a capacity of 100µF x 350V.

To provide a bp with an indicator of twenty watts, it is enough to use a standard circuit from energy-saving lamps and not at all winding additional windings on transformers. In the case when the throttle has free space and can additionally fit the turns, you can add them.

Thus, two or three dozen turns of winding should be added so that it is possible to recharge small devices or use the UPS as an amplifier for equipment.

20 watt power supply circuit

If you need a more efficient increase in power, you can use the simplest copper wire, coated with varnish. It is specially designed for winding. Make sure that the insulation on the standard inductor winding is good enough, as this part will be under the value of the incoming current. It should also be protected from secondary turns with paper insulation.

The current power supply model is 20 watts.

For insulation, we use special cardboard with a thickness of 0.05 mm or 0.1 mm. In the first case, two words are needed, in the second one is enough. We use the cross section of the winding wire from the maximum large, the number of turns will be selected by sampling. Usually, only a few turns are needed.

Having done everything necessary actions, you get a power supply of 20 watts and operating temperature transformer sixty degrees, transistor forty-two. It will not work to make more power, since the dimensions of the inductor are limited and it will not work to make more windings.

Reducing the transverse diameter of the wire used will, of course, increase the number of turns, but this will only affect the power in a minus.

In order to be able to increase the power of the power supply unit to hundreds of watts, it is necessary to additionally tighten the pulse transformer and expand the capacitance of the filter capacitor to 100 farads.

Schematic 100 watt PSU

To lighten the load and reduce the temperature of the transistors, radiators should be added to them for cooling. With this design, the efficiency will be around ninety percent.

Transistor 13003 should be connected

A 13003 transistor should be connected to the electronic ballast, which can be fixed with a shaped spring. They are advantageous in that with them there is no need to install a gasket due to the lack of metal pads. Of course, their heat transfer is much worse.

It is best to fasten with M2.5 screws, with pre-installed insulation. It is also possible to use thermal paste that does not transmit mains voltage.

Make sure that the transistors are well insulated, as current flows through them and a short circuit is possible if the insulation is poor.

Connection to a network of 220 volts

The connection is made using an incandescent lamp. It will serve as a protective mechanism and is connected in front of the power supply.

Energy-saving power supplylamps.

If the electronic ballast fails, it can be repaired. But, when the bulb itself fails, the light bulb is usually thrown away. However, the electronic ballast of such a light bulb is an almost ready-made switching power supply (PSU). The only thing in which the electronic ballast circuit differs from a real pulse power supply is the absence of an isolation transformer and a rectifier.

Let's see what's interesting on it.

- Diodes - 6 pcs. High-voltage (220 Volts) are usually low-power.

Throttle. Removes network interference.

Medium power transistors are usually MJE13003.

high voltage electrolyte. The capacitance is small (4.7 microfarads), at 400 volts.

Capacitors of different capacities, all 250 volts.

Two high frequency transformers.

Several resistors.

The purpose of the circuit elements of a switching power supply.

R0 - limits the peak current flowing through the rectifier diodes at the moment of switching on, also often acts as a fuse.

VD1 ... VD4 - bridge rectifier.

L0, C0 - power filter.

R1, C1, VD2, VD8 - converter start circuit.

The launch node works as follows. Capacitor C1 is charged from the source through resistor R1. When the voltage on the capacitor C1 reaches the breakdown voltage of the VD2 dinistor, the dinistor unlocks itself and unlocks the VT2 transistor, causing self-oscillations. After the onset of generation, rectangular pulses are applied to the cathode of the VD8 diode and the negative potential securely locks the VD2 dinistor.

R2, C11, C8 - make it easier to start the converter.

R7, R8 - improve the locking of transistors.

R5, R6 - limit the current of the bases of transistors.

R3, R4 - prevent saturation of transistors and act as fuses during breakdown of transistors.

VD7, VD6 - protect transistors from reverse voltage.

TV1 - feedback transformer.

L5 - ballast choke.

C4, C6 - separating capacitors, on which the supply voltage is divided in half.

TV2 - pulse transformer.

VD14, VD15 - pulse diodes.

C9, C10 - filter capacitors.

The difference between the lamp circuit and the pulse power supply.

This is one of the most common electrical circuits energy saving lamps.

To convert the economy lamp circuit into a switching power supply, it is enough to install only one jumper between the points A - A' and add a pulse transformer with a rectifier. Items that need to be removed are marked in red.

And this is already a complete switching power supply circuit, assembled on the basis of an economy lamp using an additional pulse transformer.

To simplify, the fluorescent lamp and a few parts have been removed and replaced with a jumper.

As you can see, the circuit does not require major changes. Additional elements added to the scheme are marked in red.

The power of the power supply is limited by the overall power of the pulse transformer, the maximum allowable current key transistors and the size of the cooling radiator, if used.

A low power power supply can be built by winding the secondary winding directly onto the frame of an existing inductor.

If the choke window does not allow winding the secondary winding, or if it is required to build a power supply with a power significantly exceeding the power of the CFL, then an additional pulse transformer will be needed.

If you want to get a power supply unit with a power of more than 100 watts, and a ballast from a 20-30 watt lamp is used, then you will have to make small changes to the electronic ballast circuit.

In particular, it may be necessary to install more powerful diodes VD1-VD4 in the input bridge rectifier and rewind the input inductor L0 with a thicker wire. If the current gain of the transistors is insufficient, then the base current of the transistors will have to be increased by decreasing the values ​​of the resistors R5, R6. In addition, you will have to increase the power of the resistors in the base and emitter circuits.

If the generation frequency is not very high, then it may be necessary to increase the capacitance of the isolation capacitors C4, C6.

Pulse transformer for power supply.

A feature of self-excited half-bridge switching power supplies is the ability to adapt to the parameters of the transformer used. And the fact that the feedback circuit will not pass through our homemade transformer completely simplifies the task of calculating the transformer and setting up the unit.

Power supplies assembled according to these schemes almost always forgive errors in calculations.

Winding a pulse transformer is not so difficult.

Capacity input filter and voltage ripple.

In the input filters of electronic ballasts, due to economy, small capacitors are used, on which the magnitude of voltage ripple with a frequency of 100 Hz depends. To reduce the level of voltage ripple at the output of the PSU, you need to increase the capacitance of the input filter capacitor. It is desirable that for every watt of PSU power there is one microfarad or so. An increase in capacitance C0 will entail an increase in the peak current flowing through the rectifier diodes at the moment the PSU is turned on. To limit this current, a resistor R0 is needed. But, the power of the original CFL resistor is small for such currents and should be replaced with a more powerful one.

If a compact power supply is required, then electrolytic capacitors can be used, which are used in flash lamps of film "soap dishes". For example, disposable cameras have unmarked miniature capacitors, their capacity is approximately 100µF x 350V.

20 watt power supply.

A power supply with a power close to the power of the original CFL can be assembled without even winding a separate transformer. If the original inductor has enough free space in the magnetic circuit window, then you can wind a couple of dozen turns of wire and get, for example, a power supply for a charger or a small power amplifier. The picture shows that one layer of insulated wire was wound over the existing winding. MGTF wire (stranded wire in fluoroplastic insulation) was used. However, in this way it is possible to obtain a power of only a few watts, since most of the window will be occupied by the insulation of the wire, and the cross section of the copper itself will be small. If you want to greater power, then you can use an ordinary copper varnished winding wire.

Attention!

The original inductor winding is under mains voltage! With the refinement described above, be sure to take care of reliable winding insulation, especially if the secondary winding is wound with ordinary varnished winding wire. Even if the primary winding is covered with synthetic protective film, extra paper pad is needed!

	The winding of the inductor is covered with a synthetic film, although it often happens that the winding of these chokes is not protected at all.
	We wind two layers of electric cardboard 0.05 mm thick or one layer 0.1 mm thick over the film. If there is no electric cardboard, we use any paper that is suitable in thickness.
	We wind the secondary winding of the future transformer over the insulating gasket. The cross section of the wire should be chosen as large as possible. The number of turns is selected experimentally (there will be few of them).

Thus, it was possible to obtain power at a load of 20 watts at a transformer temperature of 60ºC, and transistors - 42ºC. To get even more power, at a reasonable temperature of the transformer, was not allowed by the too small area of ​​​​the window of the magnetic circuit and the resulting cross section of the wire.

100 watt power supply.

To increase the power of the power supply, it was necessary to wind the TV2 pulse transformer and increase the capacitance of the mains voltage filter capacitor C0 to 100µF.

	Since the efficiency of the power supply is not at all equal to 100%, I had to screw some kind of radiators to the transistors. After all, if the efficiency of the block is even 90%, you still have to dissipate 10 watts of power. In this electronic ballast, transistors 13003 pos. 1 of such a design were installed, which is designed to be attached to a radiator using shaped springs. These transistors do not need gaskets, since they are not equipped with a metal pad, but they also give off heat much worse. It is better to replace them with transistors 13007 pos.2 with holes so that they can be screwed to the radiators with ordinary screws. In addition, 13007 have several times the maximum permissible currents. You can safely screw both transistors onto one radiator. Only, the cases of both transistors must be insulated from the case of the heatsink, even if the heatsink is inside the case of the electronic device. It is convenient to fasten with M2.5 screws, on which you must first put on insulating washers and pieces of an insulating tube (cambric). It is allowed to use heat-conducting paste KPT-8, since it does not conduct current.
	Image of the connection of the transistor with the radiator: 1. Screw M2,5. 2. Washer M2,5. 3. Insulating washer M2,5. 4. Transistor housing. 5. Gasket - a piece of tube ( cambric). 6. Gasket - mica, ceramic, fluoroplastic, etc. 7. Cooling radiator.

Attention!

Transistors are under mains voltage, so insulating gaskets must provide conditions electrical safety!

Rectifier.

All secondary rectifiers of a half-bridge switching power supply must be full-wave. If this condition is not met, then the main line may enter saturation.

There are two widely used schemes full-wave rectifiers.

1. Bridge circuit.

2. Scheme with a zero point.

The bridge circuit saves a meter of wire, but dissipates twice as much energy on the diodes.

The zero point circuit is more economical but requires two perfectly symmetrical secondary windings. Asymmetry in the number of turns or arrangement can lead to core saturation.

However, it is the zero-point circuits that are used when it is required to obtain large currents at a low output voltage. Then, to further minimize losses, instead of conventional silicon diodes, Schottky diodes are used, on which the voltage drop is two to three times less.

Example.

Rectifiers of computer power supplies are made according to the scheme with a zero point. With a power output of 100 watts and a voltage of 5 volts, even on Schottky diodes, 8 watts can be dissipated.

100 / 5 * 0,4 = 8 (Watt)

If you use a bridge rectifier, and even ordinary diodes, then the power dissipated by the diodes can reach 32 watts or even more.

100 / 5 * 0,8 * 2 = 32 (Watt).

Pay attention to this so that later you don’t look for where half the power has disappeared.

	In low-voltage rectifiers, it is better to use a zero-point circuit. Moreover, with manual winding, you can simply wind the winding in two wires.
How to properly connect a switching power supply to the network?
	For setting up switching power supplies, such a switching circuit is usually used. Here, the incandescent lamp is used as a ballast with a non-linear characteristic and protects the UPS from failure in abnormal situations. The lamp power is usually chosen close to the power of the tested switching power supply. When the pulse power supply is idling or at low load, the resistance of the filament of the lamp's kakala is small and it does not affect the operation of the unit. When, for some reason, the current of the key transistors increases, the lamp coil heats up and its resistance increases, which leads to current limitation to a safe value.
	This drawing shows a diagram of a bench for testing and adjusting a pulsed power supply that meets the standards electrical safety. The difference between this circuit and the previous one is that it is equipped with an isolation transformer, which provides galvanic isolation of the investigated UPS from the lighting network. The SA2 switch allows you to block the lamp when the power supply delivers more power.

How to set up a switching power supply?

The power supply, assembled on the basis of a serviceable electronic ballast, does not require special adjustment.

It must be connected to a load dummy and make sure that the PSU is able to deliver the calculated power.

During the run under maximum load, you need to follow the dynamics of the temperature increase of the transistors and the transformer. If the transformer heats up too much, then you need to either increase the cross section of the wire, or increase the overall power of the magnetic circuit, or both.

If the transistors get very hot, then you need to install them on radiators.

If a homemade choke from a CFL is used as a pulse transformer, and its temperature exceeds 60 ... 65ºС, then the load power must be reduced.