Switching power supply for charger. Simple switching power supply DIY 14V switching power supply

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In this article, we, together with Roman (author YouTube channel“Open Frime TV”) we will assemble a universal power supply on the IR2153 chip. This is a kind of “Frankenstein” that contains best qualities from different schemes.

The Internet is full of power supply circuits based on the IR2153 chip. Each of them has some positive features, but the author has not yet encountered a universal scheme. Therefore, it was decided to create such a diagram and show it to you. I think we can go straight to it. So, let's figure it out.

The first thing that catches your eye is the use of two high voltage capacitors instead of one 400V. This way we kill two birds with one stone. These capacitors can be obtained from old computer power supplies without spending money on them. The author specially made several holes in the board for different sizes capacitors.

If the unit is not available, then the prices for a pair of such capacitors are lower than for one high-voltage one. The capacitance of the capacitors is the same and should be at the rate of 1 µF per 1 W of output power. This means that for 300W of output power you will need a pair of capacitors of 330uF each.

Also, if we use this topology, there is no need for a second decoupling capacitor, which saves us space. And that is not all. The voltage of the decoupling capacitor should no longer be 600 V, but only 250 V. Now you can see the sizes of capacitors for 250V and 600V.

The next feature of the circuit is power supply for IR2153. Everyone who built blocks on it encountered unrealistic heating of the supply resistors.

Even if you put them on during recess, a lot of heat is released. An ingenious solution was immediately applied, using a capacitor instead of a resistor, and this gives us the fact that there is no heating of the element due to the power supply.

The author of this homemade product saw this solution from Yuri, the author of the YouTube channel "Red Shade". The board is also equipped with protection, but the original version of the circuit did not have it.

But after tests on the breadboard, it turned out that there was too little space to install the transformer and therefore the circuit had to be increased by 1 cm, this gave extra space for which the author installed protection. If it is not needed, then you can simply install jumpers instead of the shunt and not install the components marked in red.

The protection current is regulated using this trimming resistor:

Shunt resistor values ​​vary depending on the maximum output power. The more power, the less resistance needed. For example, for power below 150 W, 0.3 Ohm resistors are needed. If the power is 300 W, then 0.2 Ohm resistors are needed, and at 500 W and above we install resistors with a resistance of 0.1 Ohm.

This unit should not be assembled with a power higher than 600 W, and you also need to say a few words about the operation of the protection. She's hiccupping here. The starting frequency is 50 Hz, this happens because the power is taken from an alternator, therefore, the latch is reset at the mains frequency.

If you need a snap-on option, then in this case the power supply for the IR2153 microcircuit must be taken constant, or rather from high-voltage capacitors. The output voltage of this circuit will be taken from a full-wave rectifier.

The main diode will be a Schottky diode in a TO-247 package; you select the current for your transformer.

If you don’t want to take a large case, then in the Layout program it’s easy to change it to TO-220. There is a 1000 µF capacitor at the output, it is sufficient for any currents, since at high frequencies the capacitance can be set to less than for a 50 Hz rectifier.

It is also necessary to note such auxiliary elements as snubbers in the transformer harness;

smoothing capacitors;

as well as a Y-capacitor between the high and low side grounds, which dampens noise on the output winding of the power supply.

There is an excellent video about these capacitors on YouTube (the author attached the link in the description under his video (SOURCE link at the end of the article)).

You cannot skip the frequency-setting part of the circuit.

This is a 1 nF capacitor, the author does not recommend changing its value, but he installed a tuning resistor for the driving part, there were reasons for this. The first of them is the exact selection of the desired resistor, and the second is a slight adjustment of the output voltage using frequency. Now a small example, let's say you are making a transformer and see that at a frequency of 50 kHz the output voltage is 26V, but you need 24V. By changing the frequency, you can find a value at which the output will have the required 24V. When installing this resistor, we use a multimeter. We clamp the contacts into crocodiles and rotate the resistor handle to achieve the desired resistance.

Now you can see 2 prototype boards on which tests were carried out. They are very similar, but the protection board is slightly larger.

The author made the breadboards in order to order the production of this board in China with peace of mind. In the description under the author's original video, you will find an archive with this board, circuit and seal. There will be both the first and second options in two scarves, so you can download and repeat this project.

After ordering, the author was impatiently waiting for the payment, and now they have already arrived. We open the parcel, the boards are packed quite well - you can’t complain. We visually inspect them, everything seems to be fine, and immediately proceed to soldering the board.

And now she is ready. It all looks like this. Now let’s quickly go through the main elements not previously mentioned. First of all, these are fuses. There are 2 of them, on the high and low sides. The author used these round ones because their sizes are very modest.

Next we see the filter capacitors.

They can be obtained from an old computer power supply. The author wound the choke on a T-9052 ring, 10 turns with 0.8 mm wire 2 cores, but you can use a choke from the same computer unit nutrition.
Diode bridge - any, with a current of at least 10 A.

There are also 2 resistors on the board for discharging the capacitance, one on the high side, the other on the low side.

I also made an inverter so that it could be powered from 12 V, that is, a car version. After everything was done in terms of ULF, the question was posed: what to power it with now? Even for the same tests, or just to listen? I thought it would cost the entire ATX power supply, but when I try to “pile up”, the power supply reliably goes into protection, and somehow I don’t really want to redo it... And then the idea dawned on me to make my own, without any “bells and whistles” of the power supply (except for protection, of course). I started by searching for schemes, looking closely at schemes that were relatively simple for me. In the end I settled on this one:

It holds the load perfectly, but replacing some parts with more powerful ones will allow you to squeeze 400 W or more out of it. The IR2153 microcircuit is a self-clocking driver, which was developed specifically for operation in ballasts of energy-saving lamps. It has very low current consumption and can be powered via a limiting resistor.

Assembling the device

Let's start with etching the board (etching, stripping, drilling). Archive from PP.

First I bought some missing parts (transistors, IR, and powerful resistors).

By the way, the surge protector was completely removed from the power supply from the disc player:

Now the most interesting thing about the SMPS is the transformer, although there is nothing complicated here, you just need to understand how to wind it correctly, and that’s all. First you need to know what and how much to wind; there are many programs for this, but the most common and popular among radio amateurs is - Excellent IT. This is where we will calculate our transformer.

As you can see, we have 49 turns of the primary winding, and two windings of 6 turns each (secondary). Let's rock!

Transformer manufacturing

Since we have a ring, most likely its edges will be at an angle of 90 degrees, and if the wire is wound directly onto the ring, the varnish insulation may be damaged, and as a result, an interturn short circuit and the like. In order to eliminate this point, the edges can be carefully cut with a file, or wrapped with cotton tape. After this, you can wind the primary.

After we have wound it, we again wrap the ring with the primary winding with electrical tape.

Then we wind the secondary winding on top, although this is a little more complicated.

As can be seen in the program, the secondary winding has 6+6 turns and 6 cores. That is, we need to wind two windings of 6 turns with 6 strands of 0.63 wire (you can select it by first writing in the field with the desired wire diameter). Or even simpler, you need to wind 1 winding, 6 turns with 6 wires, and then the same one again. To make this process easier, it is possible, and even necessary, to wind into two buses (bus-6 cores of one winding), this way we avoid voltage imbalance (although it may occur, it is small and often not critical).

If desired, the secondary winding can be insulated, but not necessary. Now, after this, we solder the transformer with the primary winding to the board, the secondary winding to the rectifier, and I used a unipolar rectifier with a midpoint.

Copper consumption is of course greater, but there is less loss (and therefore less heating), and you can use just one diode assembly with an ATX power supply that has expired or is simply not working. The first switch-on must be carried out with the light bulb connected to the mains power supply; in my case, I simply pulled out the fuse, and the plug from the lamp fits perfectly into its socket.

If the lamp flashes and goes out, this is normal, since the mains capacitor has charged, but I did not experience this phenomenon, either because of the thermistor, or because I temporarily installed the capacitor at only 82 uF, or maybe it provides everything in the place smooth start. As a result, if there are no problems, you can connect the SMPS to the network. With a load of 5-10 A, I didn’t drop below 12 V, which is what I need to power car amplifiers!

1. If the power is only about 200 W, then the resistor that sets the protection threshold R10 should be 0.33 Ohm 5 W. If it breaks or burns out, all the transistors will burn out, as well as the microcircuit.
2. The network capacitor is selected at the rate of: 1-1.5 µF per 1 W of unit power.
3. In this circuit, the conversion frequency is approximately 63 kHz, and during operation, it is probably better for a 2000NM ring to reduce the frequency to 40-50 kHz, since the limiting frequency at which the ring operates without heating is 70-75 kHz. You should not chase a high frequency; for this circuit and a 2000NM ring, 40-50 kHz will be optimal. Too high a frequency will lead to switching losses on the transistors and significant losses on the transformer, which will cause it to heat up significantly.
4. If your transformer and switches heat up at idle speed when assembled correctly, try reducing the capacitance of the snubber capacitor C10 from 1 nF to 100-220 pF. The keys must be isolated from the radiator. Instead of R1, you can use a thermistor with an ATX power supply.

Here are the final photos of the power supply project:

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Discuss the article POWERFUL PULSE NETWORK BIPOLARY POWER SUPPLY

You can make a switching power supply for 5...20 Watts in less than an hour. It will take several hours to make a 100-watt power supply.

Building a power supply won't be much more difficult than reading this article. And certainly, it will be easier than finding a low-frequency transformer of suitable power and rewinding its secondary windings to suit your needs.

Introduction.

Compact Fluorescent Lamps (CFLs) are now widely used. To reduce the size of the ballast choke, they use a high-frequency voltage converter circuit, which can significantly reduce the size of the choke.

If the electronic ballast fails, it can be easily 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 unit (PSU). The only way the electronic ballast circuit differs from a real switching power supply is the absence of an isolation transformer and a rectifier, if necessary.

At the same time, modern radio amateurs experience great difficulty in finding power transformers to power their homemade products. Even if a transformer is found, its rewinding requires the use of a large amount of copper wire, and the weight and dimensions of products assembled on the basis of power transformers are not encouraging. But in the vast majority of cases, the power transformer can be replaced with a switching power supply. If you use ballast from faulty CFLs for these purposes, the savings will amount to a significant amount, especially if we are talking about transformers of 100 watts or more.

The difference between a CFL circuit and a pulse power supply.

This is one of the most common electrical diagrams energy saving lamps. To convert a CFL circuit into a switching power supply, it is enough to install just one jumper between the points A - A’ and add a pulse transformer with a rectifier. Elements that can be deleted are marked in red.

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

For simplicity, removed Fluorescent Lamp and several parts that were replaced with a jumper.

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

What power power supply can be made from CFLs?

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

A small 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 necessary 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 need to get a power supply with a power of over 100 Watts, and you are using a ballast from a 20-30 Watt lamp, then, most likely, you will have to make small changes to the electronic ballast circuit.

In particular, you may need 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 turns out to be insufficient, then you will have to increase the base current of the transistors by reducing the values ​​of resistors R5, R6. In addition, you will have to increase the power of 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 half-bridge switching power supplies with self-excitation 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 forgive errors in calculations of up to 150% or more. :) Tested in practice.

Input filter capacitance and voltage ripple.

In the input filters of electronic ballasts, to save space, 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 power supply output, you need to increase the capacitance of the input filter capacitor. It is advisable 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 power supply 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 it should be replaced with a more powerful one.

If you need to build a compact power supply, you can use electrolytic capacitors, which are used in film flash lamps. For example, Kodak disposable cameras have miniature capacitors without identification marks, but their capacity is as much as 100µF at a voltage of 350 Volts.

Power supply 20 Watt.

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 charger or a small power amplifier.

The picture shows that one layer of insulated wire was wound over the existing winding. I used MGTF wire (stranded wire in fluoroplastic insulation). However, in this way you can get a power of only a few watts, since most of the window will be occupied by the wire insulation, and the cross-section of the copper itself will be small.

If more power is required, then ordinary varnished copper winding wire can be used.

Attention! The original inductor winding is under mains voltage! When making the modification described above, be sure to take care of reliable inter-winding insulation, especially if the secondary winding is wound with ordinary varnished winding wire. Even if the primary winding is covered with a synthetic protective film, an additional paper gasket is necessary!

As you can see, the winding of the inductor is covered with a synthetic film, although often the winding of these chokes is not protected by anything at all.

We wrap two layers of electrical cardboard 0.05 mm thick or one layer 0.1 mm thick over the film. If there is no electrical cardboard, we use any paper of suitable thickness.

We wind the secondary winding of the future transformer on top of the insulating gasket. The wire cross-section should be selected as large as possible. The number of turns is selected experimentally, fortunately there will be few of them.

Thus, I managed to obtain power at a load of 20 Watts at a transformer temperature of 60ºC, and a transistor temperature of 42ºC. It was not possible to obtain even more power at a reasonable temperature of the transformer due to the too small area of ​​the magnetic circuit window and the resulting wire cross-section.

The picture shows a working power supply model.

The power supplied to the load is 20 watts. The frequency of self-oscillations without load is 26 kHz. Self-oscillation frequency at maximum load - 32 kHz Transformer temperature - 60ºС Transistor temperature - 42ºС

100 Watt power supply.

To increase the power of the power supply, we had to wind a TV2 pulse transformer. In addition, I increased the capacitance of the mains voltage filter capacitor C0 to 100µF.

Since the efficiency of the power supply is not 100%, we had to attach some radiators to the transistors.

After all, if the efficiency of the unit is even 90%, you will still have to dissipate 10 Watts of power.

I was unlucky; my electronic ballast was equipped with transistors 13003 pos. 1 of a design that was apparently designed to be attached to a radiator using shaped springs. These transistors do not need gaskets, since they are not equipped with a metal platform, but they also transfer heat much worse. I replaced them with transistors 13007 pos. 2 with holes so that they could be screwed to the radiators with ordinary screws. In addition, 13007 have several times higher maximum permissible currents.

If you wish, you can safely screw both transistors onto one radiator. I checked it works.

Only, the housings of both transistors must be insulated from the radiator housing, even if the radiator is located inside the electronic device housing.

It is convenient to fasten with M2.5 screws, onto which you must first put insulating washers and sections of an insulating tube (cambric). It is allowed to use heat-conducting paste KPT-8, since it does not conduct current.

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

The drawing shows a sectional view of the connection of the transistor to the cooling radiator.

1. Screw M2.5.
2. Washer M2.5.
3. Insulating washer M2.5 - fiberglass, textolite, getinax.
4. Transistor housing.
5. The gasket is a piece of tube (cambric).
6. Gasket - mica, ceramics, fluoroplastic, etc.
7. Cooling radiator.

And this is a working 100-watt switching power supply.

The load equivalent resistors are placed in water because their power is insufficient.

The power released at the load is 100 watts.

The frequency of self-oscillations at maximum load is 90 kHz.

The frequency of self-oscillations without load is 28.5 kHz.

Transistor temperature is 75ºC.

The area of ​​the radiators of each transistor is 27 cm².

Throttle temperature TV1 is 45ºC.

Rectifier.

All secondary rectifiers of a half-bridge switching power supply must be full-wave. If this condition is not met, the magnetic pipeline may become saturated.

There are two widely used full-wave rectifier designs.

1. Bridge circuit.

2. Circuit with 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 location can lead to saturation of the magnetic circuit.

However, it is precisely zero-point circuits that are used when it is necessary to obtain high 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.

Computer power supply rectifiers are designed according to a zero-point circuit. With a power delivered to the load of 100 Watts and a voltage of 5 Volts, even Schottky diodes can dissipate 8 Watts.

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 when you design a power supply so that you don’t have to look for where half the power disappeared. :)

In low-voltage rectifiers it is better to use a circuit with a zero point. Moreover, with manual winding, you can simply wind the winding in two wires. In addition, high-power pulse diodes are not cheap.

Or create a winding, you can assemble a switching type power supply with your own hands, which requires a transformer with only a few turns.

In this case, a small number of parts are required, and the work can be completed in 1 hour. In this case, the IR2151 chip is used as the basis for the power supply.

For work you will need the following materials and parts:

1. PTC thermistor any type.
2. Pair of capacitors, which are selected with the calculation of 1 μF. at 1 W. When creating the design, we select capacitors so that they draw 220 W.
3. Diode assembly"vertical" type.
4. Drivers type IR2152, IR2153, IR2153D.
5. Field effect transistors type IRF740, IRF840. You can choose others if they have a good resistance indicator.
6. Transformer can be taken from old computer system units.
7. Diodes, installed at the outlet, it is recommended to take from the HER family.

In addition, you will need the following tools:

1. Soldering iron and consumables.
2. Screwdriver and pliers.
3. Tweezers.

Also, do not forget about the need for good lighting at the work site.

Step-by-step instruction

circuit diagram
structural scheme

Assembly is carried out according to the drawn circuit diagram. The microcircuit was selected according to the characteristics of the circuit.

Assembly is carried out as follows:

1. At the entrance install a PTC thermistor and diode bridges.
2. Then, a pair of capacitors is installed.
3. Drivers necessary to regulate the operation of the gates of field-effect transistors. If drivers have a D index at the end of the marking, there is no need to install FR107.
4. Field effect transistors installed without shorting the flanges. When attaching to the radiator, use special insulating gaskets and washers.
5. Transformers installed with shorted leads.
6. The output is diodes.

All elements are installed in the designated places on the board and soldered on the reverse side.

Examination

In order to correctly assemble the power supply, you need to be careful about installing the polar elements, and you should also be careful when working with mains voltage. After disconnecting the unit from the power source, there should be no dangerous voltage remaining in the circuit. If assembled correctly, no further adjustment is required.

You can check the correct operation of the power supply as follows:

1. We include in the circuit, at the output of the light bulb, for example, 12 volts. At the first short-term start, the light should be on. In addition, you should pay attention to the fact that all elements should not heat up. If something gets hot, it means the circuit is assembled incorrectly.
2. On the second start We measure the current value using a tester. Let the unit operate for a sufficient amount of time to ensure that there are no heating elements.

In addition, it would be useful to check all elements using a tester for the presence of high current after turning off the power.

1. As previously noted, the operation of a switching power supply is based on feedback. The considered circuit does not require a special organization of feedback and various power filters.
2. Particular attention should be paid to the selection of field-effect transistors. In this case, IR FETs are recommended because they are renowned for their thermal resolution. According to the manufacturer, they can operate stably up to 150 degrees Celsius. However, in this circuit they do not heat up very much, which can be called a very important feature.
3. If the transistors heat up constantly, active cooling should be installed. As a rule, it is represented by a fan.

Advantages and disadvantages

The pulse converter has the following advantages:

1. High rate stabilization coefficient allows you to provide power conditions that will not harm sensitive electronics.
2. Designs considered have a high efficiency rate. Modern options executions have this indicator at 98%. This is due to the fact that losses are reduced to a minimum, as evidenced by the low heating of the block.
3. Large input voltage range- one of the qualities due to which such a design has spread. At the same time, the efficiency does not depend on the input current indicators. It is the immunity to the current voltage indicator that allows you to extend the service life of electronics, since jumps in the voltage indicator are a common occurrence in the domestic power supply network.
4. Input frequency affects the operation of only the input elements of the structure.
5. Small dimensions and weight, are also responsible for their popularity due to the proliferation of portable and portable equipment. After all, when using a linear block, the weight and dimensions increase several times.
6. Organization of remote control.
7. Lower cost.

There are also disadvantages:

1. Availability pulse interference.
2. Necessity inclusion in the circuit of power factor compensators.
3. Complexity self-regulation.
4. Less reliability due to the complexity of the chain.
5. Severe consequences when one or more circuit elements fail.

When creating such a design yourself, you should take into account that mistakes made can lead to failure of the electrical consumer. Therefore, it is necessary to provide protection in the system.

Design and operating features

When considering the operating features of the pulse unit, the following can be noted:

1. At first The input voltage is rectified.
2. Rectified voltage depending on the purpose and features of the entire structure, it is redirected in the form of a high-frequency rectangular pulse and fed to an installed transformer or filter operating at low frequencies.
3. Transformers are small in size and weight when using a pulse unit due to the fact that increasing the frequency makes it possible to increase the efficiency of their operation, as well as reduce the thickness of the core. In addition, ferromagnetic material can be used in the manufacture of the core. At low frequency, only electrical steel can be used.
4. Voltage stabilization occurs through negative feedback. Thanks to the use of this method, the voltage supplied to the consumer remains unchanged, despite fluctuations in the incoming voltage and the generated load.

Feedback can be organized as follows:

1. With galvanic isolation, an optocoupler or transformer winding output is used.
2. If you don't need to create a junction, a resistor voltage divider is used.

Using similar methods, the output voltage is maintained with the required parameters.

Standard switching power supplies, which can be used, for example, to regulate the output voltage during power supply , consists of the following elements:

1. Input part, high voltage. It is usually represented by a pulse generator. Pulse width is the main indicator that affects the output current: the wider the indicator, the greater the voltage, and vice versa. The pulse transformer stands at the section between the input and output parts and separates the pulse.
2. There is a PTC thermistor at the output part. It is made of semiconductor and has a positive temperature coefficient. This feature means that when the temperature of the element increases above a certain value, the resistance indicator rises significantly. Used as a key security mechanism.
3. Low voltage part. The pulse is removed from the low-voltage winding, rectification occurs using a diode, and the capacitor acts as a filter element. The diode assembly can rectify current up to 10A. It should be taken into account that capacitors can be designed for different loads. The capacitor removes the remaining pulse peaks.
4. Drivers they suppress the resistance that arises in the power circuit. During operation, drivers alternately open the gates of installed transistors. Work occurs at a certain frequency
5. Field effect transistors selected taking into account resistance indicators and maximum voltage when open. At a minimum value, the resistance significantly increases efficiency and reduces heating during operation.
6. Transformer standard for downgrade.

Taking into account the chosen circuit, you can begin to create a power supply of the type in question.

Sometimes in our practice we need a fairly powerful unstabilized DC voltage source. From such a source you can power, for example, a heated stage of a 3D printer, a battery-powered screwdriver, or even a powerful class D low-frequency amplifier (in this case, the UPS should be equipped with an additional filter to reduce high-frequency interference). In the case of manufacturing a power source designed for a power of 200 - 500 W, it is cheaper to go along the route of manufacturing a pulsed source, since a 50 Hz network transformer for such power will be quite expensive and very heavy.

The easiest way to assemble such a power supply is using a half-bridge circuit based on the IR2153 driver. This chip is usually used in high-quality drivers (electronic ballasts) of fluorescent lamps.

Schematic diagram of a switching power supply based on IR2153. Click on the diagram to enlarge it

The 220V mains voltage is supplied to the rectifier (diode bridge) through a surge filter on elements C1, C2, C3, C4, L1. This filter prevents high-frequency interference from the power supply from entering the electrical network. The thermistor at the input of the device reduces the current surge through the diode bridge when the power supply is turned on to the network, when capacitors C5 and C6 are charged.

Line filter coil L1, thermistor and capacitorsC5 and C6 can be removed from an old computer power supply. The pulse power transformer T1 will have to be wound independently. We also take the transformer core from an old computer unit. The transformer needs to be disassembled. To do this, place the transformer in a container of water (jar, saucepan) so that it is completely immersed in the liquid. Place the container on the stove and boil for about half an hour. After this, we drain the water, remove the transformer and while it is hot, we try to carefully disassemble the core. We unwind all the factory windings from the frame and wind new ones. The primary winding contains 40 turns of wire with a diameter of 0.8 mm. The secondary winding contains 2 parts of 3 turns each and is wound “obliquely” from 7 wires of the same wire with a diameter of 0.8 mm.

Resistor R2 in the power supply circuit of the microcircuit must have a power of at least 2 W and during operation it will heat up slightly. This is fine. The diode bridge of the mains voltage rectifier can be made up of four 1N5408 diodes (3A 1000V). IRF840 transistors must be installed on the radiator through insulating gaskets. It is advisable to install a small fan in the power supply case to cool these transistors and other circuit elements.

The first connection of the power supply to the network must be done through a 100W incandescent lamp connected in series with fuse FU1. When switched on, the lamp may flash, then it should go out. If the lamp is constantly on, this means that there is a problem with the unit - a short circuit in the installation or a component failure. In this case, you cannot connect the unit directly to the network without an incandescent lamp. We need to find the cause of the problem.