Charger from housekeeper lamp. DIY power supply from an energy-saving lamp. Selecting Output Coil Parameters

Technical information: → Make a power supply from a burnt-out energy-saving lamp

This publication contains material for repairing or manufacturing switching power supplies of different powers based on the electronic ballast of a compact fluorescent lamp.

You can make a switching power supply for 5...20 Watts in a short time. It can take up to several hours to make a 100-watt power supply.

It will not be difficult to build a power supply if you know how to solder. And undoubtedly, this is not difficult to do than to find a low-frequency transformer suitable for manufacturing of the required power and rewind its secondary windings to the required voltage.

Recently, Compact Fluorescent Lamps (CFLs) have become widespread. 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 has to be 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.

Recently, radio amateurs sometimes have difficulty finding power transformers to power their homemade designs. Even if a transformer is found, then its rewinding requires the use of copper wires of the required diameter, and the weight and dimensional parameters of products assembled on the basis of power transformers are not particularly 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 certain 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 circuits for energy-saving lamps. To convert a CFL circuit into a switching power supply, you need to install just one jumper between points A – A’ and add a pulse transformer with a rectifier. Elements that can be deleted are marked in red.

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

To simplify, the fluorescent lamp and several parts were removed and 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 when using it.

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

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 Watt, 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.

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.

Screw M2.5.
Washer M2.5.
Insulating washer M2.5 – fiberglass, textolite, getinax.
Transistor housing.
The gasket is a piece of tube (cambric).
Gasket – mica, ceramics, fluoroplastic, etc.
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 – 75ºC.
The area of the radiators of each transistor is 27 cm².
Throttle temperature TV1 – 45ºC.
TV2 – 2000NM (Ø28 x Ø16 x 9mm)

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.

Example.
The rectifiers of computer power supplies are made 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 pulsed diodes are not cheap.

How to properly connect a switching power supply to the network?

To set up switching power supplies, the following connection circuit is usually used. Here, an incandescent lamp is used as a ballast with a nonlinear characteristic and protects the UPS from failure in emergency situations. The lamp power is usually chosen close to the power of the switching power supply being tested.
When the switching power supply is operating at idle or at light load, the resistance of the lamp filament 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 the current being limited to a safe value.

This drawing shows a diagram of a stand for testing and setting up pulsed power supplies that meets electrical safety standards. The difference between this circuit and the previous one is that it is equipped with an isolation transformer, which provides galvanic isolation of the UPS under study from the lighting network. Switch SA2 allows you to block the lamp when the power supply supplies more power.

And this is an image of a real stand for repairing and setting up switching power supplies, which I made many years ago according to the diagram located above.

An important operation when testing a power supply is testing on an equivalent load. It is convenient to use powerful resistors such as PEV, PPB, PSB, etc. as a load. These “glass-ceramic” resistors are easy to find on the radio market by their green coloring. Red numbers are power dissipation.

It is known from experience that for some reason there is always not enough power equivalent to the load. The resistors listed above can, for a limited time, dissipate power two to three times higher than the rated power. When the power supply is turned on for a long time to check the thermal conditions, and the equivalent load power is insufficient, the resistors can simply be lowered into water.

Be careful, beware of burns!

Load resistors of this type can heat up to temperatures of several hundred degrees without any external manifestations!

That is, you will not notice any smoke or change in color and you can try to touch the resistor with your fingers.

How to set up a switching power supply?

Actually, a power supply assembled on the basis of a working electronic ballast does not require any special adjustment.
It needs to be connected to the load equivalent and make sure that the power supply is capable of delivering the calculated power.
During a run under maximum load, you need to monitor the dynamics of the temperature rise of the transistors and 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, you need to install them on radiators.
If a home-wound inductor from a CFL is used as a pulse transformer, and its temperature exceeds 60... 65ºС, then the load power must be reduced.
It is not recommended to raise the temperature of the transformer above 60... 65ºС, and of transistors above 80... 85ºС.

What is the purpose of the switching power supply circuit elements?

R0 – limits the peak current flowing through the rectifier diodes at the moment of switching on. In CFLs it also often serves as a fuse.
VD1… VD4 – bridge rectifier.
L0, C0 – power filter.
R1, C1, VD2, VD8 – converter starting circuit.
The launch node works as follows. Capacitor C1 is charged from the source through resistor R1. When the voltage on capacitor C1 reaches the breakdown voltage of dinistor VD2, the dinistor unlocks itself and unlocks transistor VT2, causing self-oscillations. After generation occurs, rectangular pulses are applied to the cathode of the diode VD8 and the negative potential reliably locks the dinistor VD2.
R2, C11, C8 – make it easier to start the converter.
R7, R8 – improve transistor blocking.
R5, R6 – limit the base current of the transistors.
R3, R4 – prevent saturation of transistors and act as fuses in case of breakdown of transistors.
VD7, VD6 – protect transistors from reverse voltage.
TV1 – feedback transformer.
L5 – ballast choke.
C4, C6 are decoupling capacitors on which the supply voltage is divided in half.
TV2 – pulse transformer.
VD14, VD15 – pulse diodes.
C9, C10 – filter capacitors.

Energy-saving lamps are widely used in everyday life and in production; over time they become unusable, but many of them can be restored after simple repairs. If the lamp itself fails, 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, you often need a compact, but at the same time powerful low-voltage power supply; you can make one using a failed energy-saving lamp. In lamps, lamps most often fail, but the power supply remains in working order.

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

Advantages of switching power supplies

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

The elimination of these shortcomings in switching power supplies, as well as the development of the element base, has 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:

The alternating mains current is converted into direct current without changing its voltage, i.e. 220 V.
A pulse-width converter using transistors converts DC voltage into rectangular pulses with a frequency of 20 to 40 kHz (depending on the lamp model).
This voltage is supplied to the lamp through the inductor.

Let's look at the circuit and operating procedure of a switching lamp power supply (figure below) in more detail.

Electronic ballast circuit for 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 a high-voltage filter capacitor (C 0), and through a smoothing filter (L0) is supplied to the transistor converter.

The transistor converter starts at the moment when the voltage on capacitor C1 exceeds the opening threshold of dinistor VD2. This will start the generator on transistors VT1 and VT2, resulting in self-generation 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 resistors R5 and R6 serve as limiting ones in the base circuits of transistors, 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 many transistors designed to work in such devices have such diodes built-in.

TV1 is a transformer, with its windings TV1-1 and TV1-2, the feedback voltage from the output of the generator is supplied to the base circuits of transistors, thereby creating conditions for the operation of the generator.

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

Modification of the block

Before you begin remaking the power supply, you should decide what current power you need to have at the output; the depth of the upgrade 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 watts or more, then a more thorough upgrade will be required.

It should be kept in mind that the output of the power supply will be DC voltage, not AC. It is impossible to obtain an alternating voltage with a frequency of 50 Hz from such a power supply.

Determining power

Power can be calculated using the formula:

P – 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 the manufacture of such a unit will require minimal intervention in the circuit of a 25 W energy-saving lamp.

New parts

Adding new parts to the diagram

The added details are highlighted in red, these are:

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

The added winding to the inductor plays another important role as an isolation transformer, protecting against mains voltage reaching 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 onto the inductor, approximately 10 turns of any wire;
connect to a load resistor with a power of at least 30 W and a resistance of approximately 5-6 Ohms;
connect to the network, measure the voltage at the load resistance;
divide the resulting value by the number of turns to find out how many volts there are per 1 turn;
calculate the required number of turns for a constant winding.

A more detailed calculation is given below.

Test activation of the converted power supply

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

W=U out /U vit, where

W – number of turns;

U out – required output voltage of the power supply;

U vit – voltage per turn.

Winding an additional winding on a standard inductor

The original inductor winding is under mains voltage! When winding an additional winding over it, it is necessary to provide inter-winding insulation, especially if a PEL type wire is wound, in enamel insulation. For interwinding insulation, you can use polytetrafluoroethylene tape to seal threaded connections, 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 permissible current of the transistors.

High Power Power Supply

This will require a more complex upgrade:

additional transformer on a ferrite ring;
replacing transistors;
installing transistors on radiators;
increasing the capacity of some capacitors.

As a result of this modernization, a power supply 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.

100W power supply

As can be seen in the diagram, resistor R0 has been replaced with a more powerful one (3-watt), its resistance has been reduced to 5 Ohms. It can be replaced with two 2-watt 10 ohm ones, connecting them in parallel. Further, C 0 - its capacity is increased to 100 μF, 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 such a capacity, in particular, you can take it from a point-and-shoot camera.

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

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

The calculation of such transformers is quite complicated, but there are many programs on the Internet with which this is very easy to do, for example, “Pulse transformer calculation program Lite-CalcIT”.

What does a pulse transformer look like?

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

A ferrite ring is used for the core, 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 the two secondary windings with the same wire have 12.

The secondary winding must be wound into two wires at once, and 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 met, then the diodes VD14 and VD15 will heat up unevenly, and this will further increase the asymmetry, which will ultimately damage 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 about 30 cm2.

Trial

A test run should be carried out with certain precautions taken so as not to damage the power supply:

The first test run should be carried out using a 100 W incandescent lamp to limit the current to the power supply.
Be sure to connect a 3-4 Ohm load resistor with a power of 50-60 W to the output.
If everything went as expected, 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 errors were made during the process of replacing parts, the power supply should work without problems.

If a trial run shows the unit is working, all that remains is to test it in full load mode. To do this, reduce the resistance of the load resistor to 1.2-2 Ohms and connect it directly to the network 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 either a factory radiator, which will be the most correct solution, or an aluminum plate with a thickness of at least 4 mm and an area of 30 sq. cm. It is necessary to place a mica gasket under the transistors; they must be secured to the radiator using screws with insulating bushings and washers.

Lamp block. Video

The video below shows how to make a switching power supply from an economy lamp.

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

The range of modern stores is very large. Every day new items appear. This also applies to lighting devices, which are becoming more advanced. The main differences between them are brightness, economic characteristics and the creation of the necessary comfort for the eyes.

Most manufacturers have tried to create a product similar to a conventional incandescent lamp, only with more advanced functions. Which will reduce the need for electricity, while reducing the degree of heating and impact on the environment. Therefore, the world saw a new type of LED and energy-saving lamps, which are in no way inferior to the characteristics of standard products and have a number of advantages.

Many craftsmen are trying to create a power supply from. After all, the cost of some products is significantly inflated. And to make a power supply with your own hands you won’t need a lot of time and money.

How to make a power supply from an energy-saving lamp

It is quite simple to create a switching power supply from an energy-saving lamp. It is enough to have the basic knowledge that we will need in the process of creating this product.

In order to create you will need the following materials:

Old lamp. A burnt out, non-working lamp will do.
Fiberglass for connecting parts. There are other options for attaching LEDs without soldering. You can use any other option known to you.
All the necessary elements that are in a special circuit, which necessarily contain LEDs. In order to save as much as possible, you can use any available means. It is also better to buy them on the radio components market, where prices are more affordable than in the store.
Capacitors of the required volumes, which are suitable for a maximum voltage of 400 volts.
Required number of LEDs.
Glue for fixing the product.

What kind of lamp do we need?

A power supply made from the ballast of energy-saving lamps is an excellent option for creating cheap and high-quality lighting with your own hands, without high costs. This way you can replace all the lamps in your home.

To create a power supply from an energy-saving lamp with your own hands, you first need to cut a circle from PCB to the size of the product. Then you need to draw round stripes on this shape. To do this, you can use any available means that you have on the farm. In this matter, the accuracy and evenness of the lines is important. After all, LEDs will be attached according to this scheme. While the product is drying, you can prepare other necessary parts to create a power supply. This includes soldering all the necessary parts, drilling holes with a drill that are needed for fastening, and fastening all the elements together. All parts are attached with a special adhesive that is resistant to different temperatures.

In order to create a power supply from an energy-saving lamp you will not need much time. The procedure itself will not take more than an hour. At the same time, you can get a high-quality product that will help you save on electricity.

There are also many other ways to create a power supply from an energy-saving one, which are completely accessible and within the power of almost everyone.

In this article you will find a detailed description of the process of manufacturing switching power supplies of different powers based on the electronic ballast of a compact fluorescent lamp.
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.

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.

At the same time, modern radio amateurs experience great difficulties when 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 circuits for energy-saving lamps. To convert a CFL circuit into a switching power supply, it is enough to install just one jumper between points A – A’ and add a pulse transformer with a rectifier. Elements that can be deleted are marked in red.

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

To simplify, the fluorescent lamp and several parts were removed and 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 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

Don't be scared! You can wind a pulse transformer within the course of watching one movie, or even faster if you are going to do this monotonous work with concentration.

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.

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. 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 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 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

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.

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.

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

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 – 75ºC.
The area of the radiators of each transistor is 27 cm².
Throttle temperature TV1 – 45ºC.
TV2 – 2000NM (Ø28 x Ø16 x 9mm)

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.

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.

How to properly connect a switching power supply to the network?

When the switching power supply is operating at idle or at light load, the resistance of the lamp filament 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 the current being limited to a safe value.

Be careful, beware of burns!
Load resistors of this type can heat up to temperatures of several hundred degrees without any external manifestations!
That is, you will not notice any smoke or change in color and you can try to touch the resistor with your fingers.

How to set up a switching power supply?

Actually, a power supply assembled on the basis of a working electronic ballast does not require any special adjustment.

It needs to be connected to the load equivalent and make sure that the power supply is capable of delivering the calculated power.

During a run under maximum load, you need to monitor the dynamics of the temperature rise of the transistors and 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, you need to install them on radiators.

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

What is the purpose of the switching power supply circuit elements?

R0 – limits the peak current flowing through the rectifier diodes at the moment of switching on. In CFLs it also often serves as a fuse.

VD1… VD4 – bridge rectifier.

L0, C0 – power filter.

R1, C1, VD2, VD8 – converter starting circuit.

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

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

R7, R8 – improve transistor blocking.

R5, R6 – limit the base current of the transistors.

R3, R4 – prevent saturation of transistors and act as fuses in case of breakdown of transistors.

VD7, VD6 – protect transistors from reverse voltage.

TV1 – feedback transformer.

L5 – ballast choke.

C4, C6 are decoupling capacitors on which the supply voltage is divided in half.

TV2 – pulse transformer.

VD14, VD15 – pulse diodes.

C9, C10 – filter capacitors.

Well-known to most users, energy-saving lamps, despite their popularity, quickly become unusable and usually cannot be completely restored. However, if only one lamp burns out in them, and the electronic ballast circuit feeding it remains relatively intact, it can be used as an independent power supply (see photo).

Artificially “extending the life” of energy-saving products, in which only one illuminator has burned out, makes it possible to obtain a cheap and relatively powerful UPS, the output voltage of which can be chosen arbitrarily.

Design and principle of operation

Energy-saving lamps produced by the domestic industry, as well as their widespread Chinese analogues, have a similar electronic circuit (electronic ballast), operating on the principle of pulse conversion. This design of an energy-saving lamp provides it with the following obvious advantages:

The electronic filling included in energy-saving lamps guarantees a high load capacity of the product operating in a long-term (continuous) glow mode;
The efficiency of using mains voltage (efficiency) in this case increases significantly;
The built-in circuit of the energy-saving lamp allows you to get a compact and lightweight product (due to the absence of a bulky and heavy transformer).

Additional Information. The energy-saving switching power supply circuit under consideration has only one small drawback, which is its low reliability and frequent failure.

The essence of the operation of the electronic ballast device (the so-called ballast) is quite simple and consists of the following:

First, the voltage of 220 Volts is converted in the rectifier module into a constant potential of approximately the same value;
Then, in the electronic circuit, under the influence of rectified voltage, a sequence of high-voltage pulses with a frequency of 20 to 40 kHz is formed (the exact value depends on the specific product model);
At the final stage of the conversion, the electrical pulses are rectified (smoothed) by the output inductor, and the resulting high voltage is supplied directly to the lighting lamp.

To better understand the principle by which energy-saving lamps operate, a closer look at the electronic circuitry used in them will be required.

Electronic ballast circuit

The principle approach to reusing an energy-saving product involves using an electronic board that has not yet burned out as a switching power source.

Note! If a lamp connected to the lighting network is still on, but at the same time begins to blink frequently and turn off on its own, this is a sure sign that with a certain probability it can be attributed to lamps that have already burned out.

To understand how energy-saving lamps work, you will need to understand their electronic circuit (see figure below).

The working circuit of the electronic ballast includes the following mandatory elements:

A rectifier unit on diodes VD1-VD4, to which the mains voltage is supplied through an additional limiting resistor R0;
High voltage filter capacitor (C0) and smoothing filter (L0);
A special transistor converter that ensures the formation of operating ESL pulses (this circuit contains a number of electronic parts that facilitate the automatic start of oscillations with a frequency of 20 kHz).

Diodes VD7 and VD6 perform a protective function, and transformers TV1-1 and TV1-2 form feedback circuits that increase the stability of the generation process. In red in the figure, which shows the lamp (more precisely, its diagram), a set of parts is highlighted that must be removed when modifying the electronic unit.

Important! The control points A–A' indicated in the figure must be connected by a metal jumper.

Features of electronic module modification

Selection by power

Before you make a power supply from an energy-saving lamp, first of all, you will need to decide on the power that will be required from it in each specific case. The degree of modernization of the electronic part, ensuring the possibility of normal operation of the equipment connected to it, will depend on this parameter.

So, with a small operating power of the future power supply, alteration of the electronic ballasts will affect only a small part of the entire circuit (see figure).

If you plan to make a switching power supply from an energy-saving lamp, designed for significant loads (to connect a pulse soldering iron, for example), its load characteristic must be increased. This will require significant modification of the electronic ballast circuit for an output power of more than 50 watts.

To calculate this parameter, remember that it is defined as the product of the output current and the operating voltage. That is, if a 50-watt pulse soldering iron is designed for a voltage of 25 Volts, then a homemade power supply must provide an output current of at least 2 Amps (the upgraded circuit is given below).

In addition to a soldering iron, any low-voltage, medium-power lamp can operate from such a switching power supply.

What parts will be required

In the revised diagram No. 1, the new parts are highlighted in red and indicate the following elements:

Diode bridge VD14-VD17;
Two capacitors (simple and electrolytic) C9 and C10;
An additional winding wound on the ballast choke L5, the number of turns of which is selected experimentally.

Important! It serves as a separating element, eliminating the possibility of 220 V mains voltage reaching the output of the power module.

Let's figure out what can be done to protect the power supply output from overloads by correctly choosing the number of turns of the output coil.

Selecting Output Coil Parameters

To calculate the required number of turns in the removable winding L5, you need to experiment a little, that is, proceed as follows:

First, you need to wind about 10 turns of any insulated wire over the existing coil;
Then you should load the wound part onto a rheostat with a resistance of 5-6 Ohms and a power of about 30 Watts (the soldering method can be used to connect it);
The result is the design shown in the figure below;

After this, the circuit is connected to the network, and then the voltage on the rheostat is measured using a tester;
The resulting value in volts is divided by the previously wound number of turns, resulting in a figure corresponding to the specific voltage per 1 turn.

At the end of the experiment, the required number of turns necessary to obtain a given output voltage is determined by dividing its value by the previously obtained result.

Winding design

When modifying the output coil, you must always remember that the primary winding is under high voltage. Therefore, all design changes should be carried out only with the converter device disconnected from the network.

Winding according to version No. 1

When winding additional turns onto an existing inductor in an electronic ballast, one should not forget about the inter-winding insulation, which is mandatory for PEL type wires (in thin enamel insulation).

As such insulation, wound in several layers, a special polytetrafluoroethylene tape should be used, which is often used to seal threaded connections.

Additional Information. This insulating tape is only 0.2 mm thick and is most often used when carrying out repair and plumbing work.

The finished winding is loaded onto a diode bridge, the rectified voltage from which is supplied to the load (this could be an ordinary low-voltage light bulb, for example). The output power in a power supply made according to this circuit is usually limited by the size of the transformer used and the permissible currents of the switched device on transistors TV1 and TV2.

Winding according to version No. 2

To obtain a higher power power supply to which a pulsed soldering iron can be connected, for example, more complex modifications will be required (see the diagram in the figure below).

The finalized part of the diagram, highlighted in red in the figure, includes the following elements:

Additional transformer TV2 with three windings (for its manufacture it is most convenient to use a ferrite ring with the appropriate magnetic conductivity);
Two semiconductor rectifying diodes VD14 and VD15;
Smoothing capacitors C9 and C10 of sufficient capacity.

In addition, it will be necessary to replace the switching transistors TV1 and TV2 with more powerful samples and simultaneously install them on cooling radiators.

Note! To better smooth out ripples, the capacitances of most capacitors (including output C9 and C10) will need to be slightly increased.

As a result of the modernization, a partially burnt energy-efficient lamp turns into a fairly powerful power supply (up to 100 Watt). Moreover, its output voltage can take values from 12 Volts and higher with an operating current in the load of up to 8-9 Amperes. The indicated parameters of a device converted from a burnt lamp may well be enough to power a simple screwdriver, for example.

In conclusion, we note that in order to use a burnt-out energy-saving lamp to make a switching power supply (UPS) yourself, you need certain skills in handling an electric soldering iron. In addition, you will need the ability to understand electronic circuits at least at the level of understanding the material presented in this review.