Power supply from cl. Power supply from an economy lamp

Despite the small size of energy-saving lamps, they have a lot of electronic components. According to its design, this is an ordinary tubular fluorescent lamp with a miniature bulb, but only coiled into a spiral or other compact spatial line. It is therefore called a compact fluorescent lamp (CFL for short).

And it is characterized by all the same problems and malfunctions as for large tubular light bulbs. But the electronic ballast of a light bulb that has ceased to shine, most likely due to a burnt out spiral, usually retains its performance. Therefore, it can be used for any purpose as a switching power supply (abbreviated as UPS), but with preliminary refinement. This will be discussed further. Our readers will learn how to make a power supply from energy saving lamp.

What is the difference between UPS and electronic ballast

We will immediately warn those who expect to receive a powerful power source from CFLs - you cannot get more power as a result of a simple alteration of the ballast. The fact is that in inductors that contain cores, the working area of ​​magnetization is strictly limited by the design and properties of the magnetizing voltage. Therefore, the pulses of this voltage created by the transistors are precisely matched and determined by the circuit elements. But such an electronic ballast power supply is quite sufficient for powering led strip. Moreover, a switching power supply from an energy-saving lamp corresponds to its power. And it can be up to 100 watts.

The most common CFL ballast circuit is built according to the half-bridge (inverter) circuit. This is an oscillator based on a TV transformer. The TV1-3 winding magnetizes the core and at the same time acts as a choke to limit the current through the EL3 lamp. Windings TV1-1 and TV1-2 provide positive feedback for the appearance of a voltage that controls transistors VT1 and VT2. The diagram shows a CFL bulb with elements that ensure its launch in red.

All inductors and capacitances in the circuit are chosen so as to obtain precisely dosed power in the lamp. The performance of transistors is related to its value. And since they do not have radiators, it is not recommended to strive to get significant power from the converted ballast. The ballast transformer does not have a secondary winding from which the load is powered. This is the main difference between it and the UPS.

What is the essence of the reconstruction of the ballast

To be able to connect the load to a separate winding, you must either wind it on the L5 inductor, or use an additional transformer. The alteration of the ballast in the UPS provides for:

For further conversion of the electronic ballast into a power supply from an energy-saving lamp, a decision must be made regarding the transformer:

• use the existing throttle by modifying it;
• or use a new transformer.

Choke transformer

Let's look at both options next. In order to use the choke from the electronic ballast, it must be unsoldered from the board and then disassembled. If it uses an E-shaped core, it contains two identical parts that are interconnected. In this example, orange duct tape is used for this purpose. It is carefully removed.

The halves of the core are usually glued together so that there is a gap between them. It serves to optimize the magnetization of the core, slowing down this process and limiting the rate of current rise. We take our impulse soldering iron and heat the core. We apply it to the soldering iron with the joints of the halves.

Having disassembled the core, we get access to the coil with the wound wire. The winding that is already on the coil is not recommended to be unwound. This will change the mode of magnetization. If the free space between the core and the coil allows one layer of fiberglass to be wrapped to improve the insulation of the windings from each other, this should be done. And then wind ten turns of the secondary winding with a wire of suitable thickness. Since the power of our power supply will be small, a thick wire is not needed. The main thing is that it fits on the coil, and the halves of the core are put on it.

After winding the secondary winding, we collect the core and fix the halves with adhesive tape. We assume that after testing the PSU, it will become clear what voltage is created by one turn. After testing, we will disassemble the transformer and add the required number of turns. Usually, the conversion aims to make a voltage converter with a 12 V output. This allows you to get, when using stabilization Charger for battery. At the same voltage, you can make a driver for LEDs from an energy-saving lamp, as well as charge a flashlight powered by a battery.

Since the transformer of our UPS will most likely have to be winded, it is not worth soldering it into the board. It is better to solder the wires sticking out of the board, and solder the leads of our transformer to them for the duration of testing. The ends of the terminals of the secondary winding must be cleaned of insulation and coated with solder. Then, either on a separate socket, or directly on the terminals of the wound winding, it is necessary to assemble a rectifier on high-frequency diodes according to the bridge scheme. A 1 uF 50 V capacitor is sufficient for filtering during voltage measurement.

UPS testing

But before connecting to a 220 V network, a powerful resistor is necessarily connected in series with our block, converted from a lamp with our own hands. This is a security measure. If a short circuit current flows through the pulse transistors in the power supply, the resistor will limit it. In this case, a 220 V incandescent bulb can become a very convenient resistor. In terms of power, it is enough to use a 40-100-watt lamp. At short circuit in our device, the light bulb will glow.

Next, we connect the multimeter probes to the rectifier in the measurement mode constant voltage and apply a voltage of 220 V to electrical circuit with bulb and power supply board. Twisting and open current-carrying parts must be insulated beforehand. To supply voltage, it is recommended to use a wired switch, and put the light bulb in a liter jar. Sometimes they burst when turned on, and the fragments scatter around. Usually the tests pass without problems.

More powerful UPS with separate transformer

They allow you to determine the voltage and the required number of turns. The transformer is finalized, the unit is tested again, and after that it can be used as a compact power source, which is much smaller than an analogue based on a conventional 220 V steel core transformer.

To increase the power of the power source, it is necessary to use a separate transformer, made similarly from a choke. It can be removed from a higher power light bulb that has burned out completely along with the ballast semiconductor products. The same circuit is taken as the basis, which is distinguished by the addition of an additional transformer and some other details shown in red lines.

The rectifier shown in the image contains fewer diodes compared to the rectifier bridge. But for its operation, more turns of the secondary winding will be required. If they do not fit into the transformer, a rectifier bridge must be used. A more powerful transformer is made, for example, for halogens. Anyone who has used a conventional transformer for a halogen lighting system knows that they are powered by a fairly large current. Therefore, the transformer is bulky.

If transistors are placed on radiators, the power of one power supply can be significantly increased. And in terms of weight and dimensions, even several such UPSs for working with halogen lamps will turn out to be smaller and lighter than one transformer with a steel core of equal power. Another option for using workable housekeeper ballasts can be their reconstruction for an LED lamp. Converting an energy-saving lamp to an LED design is very simple. The lamp is disconnected, and a diode bridge is connected instead.

At the output of the bridge, a certain number of LEDs are connected. They can be connected in series with each other. It is important that the current of the LED is equal to the current in the CFL. Energy-saving light bulbs can be called a valuable mineral in the era of LED lighting. They can find use even after the end of their service life. And now the reader knows the details of this application.

Sometimes it becomes necessary to have a medium power switching power supply on hand. Network power supplies using an iron transformer are very huge. But besides the heavy weight, they have another hidden drawback. If you plan to assemble a power amplifier with a mains power supply (a 50Hz transformer), then you should take into account that the voltage after the diode bridge 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 for a long time. Works very stably and silently, has the small weight and the compact sizes.

Modern power tools are popular because during operation they allow you not to become attached to the mains, which expands the possibilities of their operation, even in the field. The presence of a rechargeable battery significantly limits the duration active work, so screwdrivers and drills require constant access to a power source. Unfortunately, for modern tools (often made in China), the power battery has little reliability and often fails quickly, so craftsmen have to make do with improvised materials in order not only to assemble a switching power supply, but also save money on this.
An example of such a hand-made is a switching power supply (UPS) for an 18 V cordless screwdriver, assembled from the elements of an inoperative energy-saving lamp, which can be useful even after its “death”.

The structure and principle of operation of an energy-saving lamp

The structure of an energy-saving lamp

To understand how an energy-saving lamp can be useful, consider its structure.
The design of the lamp consists of the following components:

Two spirals (electrodes) are connected to the bulb of the lamp, which, under the influence of current, heat up and emit electrons from their surface. As a result of the interaction of electrons with mercury vapor, a glow charge arises in the flask, "giving birth" to UV radiation. By acting on the phosphor, ultraviolet "makes" the lamp glow. The color temperature of the "housekeeper" is determined by the chemical composition of the phosphor.

Types of breakdowns of energy-saving lamps

An energy-saving lamp can fail in two cases:

• broken lamp bulb;
• the electronic ballast (EB) has failed (voltage converter high frequency), which is responsible for converting alternating current into direct current, gradually heating the electrodes and preventing the device from flickering during switching on.

If the bulb is destroyed, the lamp can simply be thrown away, and if the electronic ballast breaks down, it can be repaired or used for its own purposes, for example, used to make a UPS by adding to the circuit isolating transformer and rectifier.

Complete set of electronic ballast of an energy-saving lamp
Most EB lamps are high-frequency voltage converters assembled on semiconductor triodes (transistors).
More expensive devices are equipped with a complex EB circuit, respectively, cheaper ones are simplified.
The electronic ballast is “complete” with the following electrical elements:

• bipolar transistor operating at voltages up to 700 V and currents up to 4A;
• protective diodes (mainly, these are elements of the D4126L type or similar);
• pulse transformer;
• throttle;
• bidirectional dinistor, similar to the dual KH102;
• capacitor 10/50V
• some EB circuits are equipped with field effect transistors.

The figure below shows the composition of the electronic ballast of a lamp with functional description each element.

Functional description

Some EB circuits of energy-saving lamps allow you to almost completely replace the circuit of a home-made pulsed source, supplementing it with several elements and making minor changes.

Separate converter circuits operate on electrolytic capacitors or contain a specialized microcircuit. It is better not to use such EB circuits, because they are often the sources of failures for many electronic devices.

What is common between the electrical circuits of "housekeepers" and UPS?

Below is one of the common electrical circuits lamps, supplemented jumper A-A’, which replaces the missing parts and the lamp, with a pulse transformer and a rectifier. Schematic elements highlighted in red can be deleted.

The electrical circuit of the "housekeeper" at 25 W

As a result of some changes and necessary additions, as can be seen from the diagram below, it is possible to assemble a switching power supply, where the added elements are highlighted in red.

What PSU power parameters can be achieved from an energy-saving lamp?

The “second” life of the “housekeeper” is often used by modern radio amateurs. After all, their hand-mades often require power transformer, with the presence of which there are certain difficulties, starting with its purchase and ending with the expense a large number wires for winding and overall dimensions of the final product. Therefore, craftsmen got used to replacing the transformer with a switching power supply. Especially if for these purposes you use the electronic ballast of a faulty lighting device, this will save a lot of money, especially for a transformer with a power of more than 100W.

A low-power switching power supply can be built by rewinding the frame of an existing inductor. To get a power supply more high power, an additional transformer is required. A switching power supply of 100 W m more can be made on the basis of EB lamps with a power of 20-30 W, the circuit of which will have to be slightly changed, supplementing it with a rectifying diode bridge VD1-VD4 and changing the section of the inductor winding L0 upwards.

Homemade transformer PSU

If it is not possible to increase the gain of the transistors, it will be necessary to increase the current of their base by changing the values ​​of the resistors R5-R6 to smaller ones. In addition, you will have to increase the power parameters of the resistors in the base and emitter circuits.
With a low generation frequency, it will be necessary to replace the capacitors C4, C6 with elements with a larger capacity.

Homemade power supply

Power Supply

A low-power switching power supply with power parameters of 3.7-20 W does not require the use of a pulse transformer. To do this, it will be enough to increase the number of turns of the magnetic circuit on an existing inductor. The new winding can be wound over the old one. For this, it is recommended to use MGTF wire with fluoroplastic insulation, which will fill the gap of the magnetic circuit, which will not require a large amount of material and will provide the necessary power of the device.

To increase the power of the UPS, you will have to use a transformer, which can also be built on the basis of an existing EB inductor. Only for this it is recommended to use a varnished winding copper wire, having previously wound it on the native choke winding protective film to avoid breakdown. The optimal number of turns of the secondary winding is usually selected empirically.

How to connect a new UPS to a screwdriver?

To connect a switching power supply assembled on the basis of an electronic ballast, it is necessary to disassemble the screwdriver by removing all fasteners. Using soldering or heat shrink tubing, we connect the motor wires of the device to the UPS output. Connecting wires by twisting is not a desirable contact, so we forget about it as unreliable. First, we drill a hole in the body of the tool through which we put the wires. To prevent accidental pulling out, the wire must be crimped with an aluminum clip at the very opening of the inner surface of the power tool case. Clip sizes that exceed the diameter of the hole will prevent the wire from being mechanically damaged and falling out of the case.

screwdriver

As you can see, even after working out, an energy-saving lamp can last long time bringing benefit. On its basis, you can assemble a low-power power pulse unit up to 20 W, which will perfectly replace the 18 V power tool battery or any other charger. To do this, you can use the elements of the electronic ballast of an energy-saving lamp and the technology described above, which is what craftsmen use, most often to repair a failed battery or save on buying a new power source.

How to convert the housekeeper converter into a switching power supply?

If you have a housekeeper lamp lying around with a faulty bulb, do not rush to throw it away. Inside the base, she has a high-frequency converter circuit, which replaces the overall and heavy ballast choke, as in conventional LDS connection diagrams. Based on this converter, you can make a 20-watt switching power supply, and with a more careful approach, you can squeeze out more than a hundred.

Below is one of the most common options for housekeeper converter circuits:

This is a 25 watt Vitoone energy saving lamp circuit. The red color on it indicates those elements that we do not need, so we exclude them from the diagram, and put a jumper between points A and A '. It remains the case for small things, to fasten a pulse transformer and a rectifier to the output.

A variant of the already converted "energy saving" circuit into a switching power supply is shown in the figure below:

As can be seen from the diagram, R0 was set at 2 times the lower value, but its power was increased, C0 was replaced by 100.0 mF, and TV2 was added at the output with a rectifier on VD14, VD15, C9 and c10. Resistor R0 serves as a fuse and charging current limiter when turned on. Select the capacitance rating C0 so that it is (approximately) numerically equal to the power of the PSU that you are making.

Regarding the capacitor C0: it can be "teared out" from an old Kodak-type film camera, or any other film soap dish, there in the flash lamp circuit it just costs the one we need, 100mF at 350V.

TV2 is a pulse transformer, the power of the power supply itself depends on its overall power, as well as on the maximum allowable current of the key transistors. To manufacture a low-power pulsed PSU, it is enough to wind the secondary winding on the existing inductor, as shown in the following diagram:

To power any low voltage charger or not very powerful amplifier, wind 20 turns over the existing L5 winding, this will be enough.

The picture above shows a working version of the power supply without a 20 watt rectifier. At idle, the frequency of self-oscillations is 26 kHz, under load 20W 32 kHz, the transformer heats up to 60 ºС, transistors up to 42 ºС.

Important!!! On the primary winding during the operation of the converter there is mains voltage, so be sure to lay a layer of paper insulation that will separate the primary and secondary windings, even if the primary already has a synthetic protective film.

But it also happens that in the window of the existing inductor there is not enough space for winding the secondary winding, or in the case when we have to create a power supply unit of much greater power than the power of the converted "energy saving" - here we cannot do without the use of an additional pulse trance (see second article outline).

For example, we make a switching PSU with more than 100W of power, and use a ballast from a 20-watt light bulb. In this case, it will be necessary to replace VD1 - VD4 with more "current" diodes, and wind the inductor L0 with a thicker wire. If the current gain of VT1 and VT2 is insufficient, increase the base current of the transistors by reducing the ratings of R5 and R6, as well as increasing the power of the resistances in the base and emitter circuits.

If the generation frequency is insufficient, increase the ratings of the capacitances C4 and C6.

Practical tests have shown that half-bridge pulse power supplies are not critical to the parameters of the output transformer, because the OS circuit does not pass through it, therefore, calculation errors of up to 150 percent are allowed.

Switching PSU 100 watts.

As already mentioned above, in order to get a powerful PSU, an additional TV2 pulse transformer is wound, R0 is replaced, C0 is replaced by 100 mF, it is advisable to replace transistors 13003 with 13007, they are designed for more current, and it is better to put them on small radiators through insulating gaskets (mica for example).

The connection section of transistors with radiators is shown in the figure below:

The current model of a switching power supply unit operating at a load of 100 W is shown in the picture below:

The transformer is wound on a 2000HM ring, outer diameter 28mm, inner diameter 16mm, ring height 9mm.
Due to insufficient power load resistors, they are placed in a saucer of water.
Generation without load 29 kHz, under load 100 W - 90 kHz.

About the rectifier.

So that the magnetic circuit of the transformer TV2 does not enter saturation, make the rectifiers in the half-bridge pulsed power supply units full-wave, i.e. they must be bridge (1), or with a zero point (2). See picture below.

With a bridge circuit, a little less wire is required per winding, but at the same time, 2 times more energy is dissipated on VD1-VD4. The second fragment of the figure shows a variant of the rectifier circuit with a zero point, it is more economical, but the windings in this case must be absolutely symmetrical, otherwise the magnetic circuit will enter saturation. The second option is used when, with a small output voltage, you need to have a significant current. To minimize losses, silicon diodes are replaced by Schottky diodes, the voltage drops on them less than 2-3 times.

Let's look at an example:

At P=100W, U=5V, TV1 with midpoint, 100 / 5 * 0,4 = 8 , i.e. Schottky diodes dissipate 8 watts of power.
At P=100W, U=5V, TV1 with bridge rectifier and conventional diodes, 100 / 5 * 0,8 * 2 = 32 , i.e. VD1-VD4 will dissipate power of the order of 32 watts.

Keep this in mind, and don't look for half the lost power afterwards.

Setting up a pulsed power supply.

Connect the UPS to the network according to the diagram below (fragment 1). Here HL1 will act as a ballast with a non-linear characteristic and will protect your device if an emergency occurs. The power of HL1 should be approximately equal to the power of the power supply that you are testing.

When the power supply is turned on without load, or is operating at low load, the HL1 filament has little resistance, so it does not have any effect on the operation of the PSU. When some kind of malfunction occurs, the currents VT1 and VT2 increase, the lamp starts to glow, the resistance of the filament increases, thereby reducing the current in the circuit.

If you are constantly engaged in the repair and adjustment of switching power supplies, it will not be superfluous to assemble a special stand (figure above, fragment 2). As you can see, there is an isolation transformer here (galvanic isolation between the PSU and the household network), and there is also a toggle switch that allows you to supply voltage to the PSU bypassing the lamp. This is necessary in order to test the converter when operating on a powerful load.

Powerful glass-ceramic resistors can be used as a load, they are usually green in color (see figure below). The red numbers in the figure indicate their power.

During long-term tests, when it is necessary to check the thermal regime of the PSU circuit elements, and the load resistors are not powerful enough, the latter can be lowered in a saucer with water. During operation, the load dummy gets very hot, so do not grab the resistors with your hands to avoid burns.

If you did everything carefully and correctly, and at the same time used a known-good ballast from an energy-saving lamp, then there is nothing special to fix. The scheme should work immediately. Connect the load, apply power, and figure out if your PSU is capable of delivering the required power. Watch the temperatures of VT1, VT2 (should be no higher than 80-85 ºС) and the output transformer (should be no more than 60-65 ºС).

With high heating of the transformer, increase the wire cross-section, or wind the transformer on a magnetic circuit with a larger overall power, or you may have to do both the first and second.

When heating transistors - put them on a radiator (through insulating gaskets).

If you invented a low-power UPS, and at the same time you wound up the existing inductor, and during operation it heats up above the permissible norm, try how it works for a lower power load.

You can download the calculation programs for pulse transformers in the article:

Good luck with the changes.

When to get 12 volts for LED strip, or for some other purpose, there is an option to make such a power supply with your own hands.

Light bulb power supply circuit

Since the main reason for the failure of compact fluorescent lamps is the burnout of one of the filaments of the bulb, almost all of them can be converted into a switching power supply with the desired voltage.

In this particular case, I reworked the electronic ballast circuit of a 15 watt light bulb into a 12 volt 1 amp switching power supply.

Each lamp manufacturer has its own sets of parts with certain ratings in the circuits of manufactured electronic ballasts, but all circuits are typical. Therefore, in the diagram, I did not give the entire circuit of the lamp, but indicated only its typical beginning and the strapping of the lamp bulb. The electronic ballast circuit is drawn in black and red. red- the flask and the capacitor connected to two filaments are highlighted. They should be removed. Green the color on the diagram indicates the elements that need to be added. Capacitor C1 - should be replaced with a larger capacity, for example, 10-20u 400v.

A fuse and an input filter are added to the left side of the circuit. L2 is made on the ring from motherboard, has two windings of 15 turns with a wire from a twisted pair Ø - 0.5 mm. The ring has an outer diameter of 16mm, an inner diameter of 8.5mm and a width of 6.3mm. Choke L3 has 10 turns Ø - 1 mm, made on the ring from the transformer of another energy-saving lamp.

You should choose a lamp with a larger void of the inductor window Tr1, since it will need to be converted into a transformer. I managed to wind 26 turns Ø - 0.5 mm on each of the half of the secondary winding. This type of winding requires perfectly symmetrical winding halves. To achieve this, I recommend winding the secondary winding into two wires at once, each of which will serve as a symmetrical half of each other.

Transistors left without radiators, because. the estimated consumption of the circuit is less than the power that the lamp consumed. As a test, 5 meters of RGB LED strip was connected to the maximum glow for 2 hours, consuming 12v 1A.

In this article, we will consider a simple option impulse block nutrition. Ballast from LDS in our time costs a penny, like an electronic transformer (ET) from halogen lamps. We know about the main disadvantages of a UPS for halogens - it works too unstable, the output voltage may deviate in one direction or another, it does not have a surge protector.

But all these shortcomings are nothing compared to the two main ones - with even a second short circuit at the output, the circuit literally explodes. Another main drawback is that the device only works under load, that is, if we connect an LED with a limiting resistor at the output, it will not glow, which makes this UPS very inconvenient for other purposes.

Ballast from LDS - compared to ET units, they are more stable, there are ballasts with line filters. Even in cheap blocks, we can observe a choke, a thermistor and electrolytes for power, a fuse is almost always installed in them. All this makes the ballast durable and reliable.

But let's remember that the output voltage of the ballast is only suitable for powering the LDS. In my case, a 40 watt LDS ballast was used.
I decided combine these two schemes to obtain a new type of UPS.

The Chinese electronic transformer for 105 watts was disassembled, a pulse transformer was soldered from the board.

There is no need to do any special alterations, just high voltage from the ballast is supplied to the primary winding of the pulse transformer. Power is supplied through a 3kV 6800pF capacitor (both the capacitance and the voltage of the capacitor can deviate in one direction or another by 30-40%)
On the secondary winding of the transformer, we get just 12 volts.

The power of such a power supply is small, but it is enough to create a low-power laboratory UPS. By supplementing the circuit with a rectifier, we will get a UPS that can be used as a charger or a power supply for power amplifiers, the scope is quite wide, because no design will work without a power supply.

When supplementing with a diode rectifier, pulse diodes must be used, since the operating frequency of the device is 15-30 kHz or more (the frequency depends on the device circuit, its power and manufacturer, it is different for everyone).

Also, it should be noted that the output current can reach up to 3.5-4A, therefore, powerful diodes are needed. It is very convenient to use diode assemblies from computer power supplies; KD213A is perfect from a domestic interior.

List of radio elements

Energy-saving lamps were actively positioned as a replacement for low-cost and unreliable incandescent lamps. The gradual decline in prices for "housekeepers" has led to the fact that they have become almost universal distribution.

The biggest disadvantage of LEDs is their high cost. Not surprisingly, many are converting energy-saving lamps into LEDs, using the most affordable and inexpensive element base.

Theoretical justification

LEDs operate at low voltage - about 2-3V. But most importantly, for normal operation not voltage stability is required, but current stability flowing through them. When the current decreases, the brightness of the glow decreases, and the excess leads to the failure of the diode element. Semiconductor devices, which include LEDs, have a pronounced temperature dependence. When heated, the junction resistance drops and the forward current increases.

A simple example: a stable voltage source outputs 3V, while the current consumption of the LED is 20mA. When the temperature rises, the voltage on the LED remains unchanged, and the current increases up to unacceptable values.

To exclude the described situation, light sources on semiconductors are powered by a current stabilizer, which is also a driver. By analogy with fluorescent lamps the driver is sometimes called a ballast for LEDs.

The presence of an input voltage of 220V, together with the requirement for current stabilization, leads to the need to create complex scheme nutrition LED lamps.

Practical implementation of the idea

The simplest power supply for LEDs from a 220V network is as follows:

In the figure shown, the resistor provides a drop in the excess voltage of the supply network, and the diode connected in parallel protects the LED element from voltage pulses of reverse polarity.

As can be seen from the figure, which can be verified by calculations, a quenching resistor is required high power which generates a lot of heat during operation.

Below is a diagram where a quenching capacitor is used instead of a resistor.

Using a capacitor as a ballast allows you to get rid of a powerful resistor and increase the efficiency of the circuit. Resistor R1 limits the current at the moment the circuit is turned on, R2 serves to quickly discharge the capacitor at the moment it is turned off. R3 further limits the current through the group of LEDs.

Capacitor C1 serves to dampen excess voltage, and C2 smoothes out power ripples.

The diode bridge is formed by four diodes of the 1N4007 type, which can be soldered from an unusable energy-saving lamp.

The circuit calculation was made for HL-654H245WC LEDs with an operating current of 20mA. It is not excluded the use of similar elements with the same current.

Just as in the previous circuit, current stabilization is not provided here. In order to prevent the failure of the LEDs, in the ballast circuit for LED lamps, the capacitance of the capacitor C1 and the resistance of the resistor R3 are chosen with a margin so that at the maximum input voltage and elevated temperature of the LEDs, the current through them does not exceed the allowable values. In normal mode, the current through the diodes is somewhat less than the nominal one, but this practically does not affect the brightness of the lamp.

The disadvantage of such a scheme is that the use of more powerful LEDs will require an increase in the capacitance of the quenching capacitor, which has large dimensions.

Similarly, the LED strip is powered from the energy-saving lamp board. It is important that the current of the LED strip matches the line of LEDs, that is, 20mA.

Using an energy-saving lamp driver

A more reliable circuit is when a driver from an energy-saving lamp is used with minimal alterations. As an example, the figure shows the conversion of a 20W energy-saving lamp to power powerful LED with a current consumption of 0.9A.

Alteration of electronic ballast for LED lamps in this example minimal. Most of the elements in the circuit are left from the old lamp driver. The L3 choke has undergone changes and a rectifier bridge has been added. In the old circuit, a fluorescent lamp was connected between the right terminal of the capacitor C10 and the cathode of the diode D5.

Now the capacitor and diode are connected directly, and the inductor is used as a transformer.

Alteration of the inductor consists in winding the secondary winding, from which the voltage will be removed to power the LED.

Without disassembling the inductor, you need to wind 20 turns of enameled wire with a diameter of 0.4mm around it. When turned on, the open circuit voltage of the newly made winding should be about 9.5–9.7V. After connecting the bridge and the LED, the ammeter included in the power supply of the LED element should show about 830-850mA. A greater or lesser value requires correction of the number of turns of the transformer.

Diodes 1N4007 or similar can be used from another failed lamp. Diodes in housekeepers are used with a large margin of current and voltage, so they rarely fail.

All the above LED driver circuits from an energy-saving lamp, although they provide low-voltage power, have a galvanic connection with the network alternating current, so when working on debugging, you need to take precautions.

It is best and safest to use a separating transformer with the same primary and secondary windings during operation. Having the same 220V at the output, the transformer will provide reliable galvanic isolation of the primary and secondary circuits.