Transformers as components of automotive electronic devices. Transformers for halogen lamps: types, advantages and applications
Standard transformers assembled on electrical steel have long been no longer used in modern electronic radio equipment. All without exception modern televisions, computers, stereos and receivers have electronic transformers in their power supplies. There are several reasons:Saving. At current prices for copper and steel, it is much cheaper to install a small board with a dozen parts and a small pulse transformer on a ferrite core.
Dimensions. An electronic transformer of similar power will be 5 times smaller in size and weigh as much less.
Stability. Most often, ETs already have built-in protection against short circuits and overcurrents (except for cheap Chinese ones), and the input voltage range is 100-270 volts. Agree - no ordinary transformer will provide stable output voltages with such a power supply variation.
Therefore, it is not surprising that radio amateurs have begun to increasingly use these pulse voltage converters to power their homemade designs. As a rule, such ETs are produced at a voltage of 12V, but increase or decrease it, as well as add a few additional voltages (for example, when creating a bipolar source ULF power supply), you can wind it up a few turns on a ferrite ring.
And you don’t have to waste hundreds of meters of wire, since, unlike a conventional transformer on iron, there is approximately 1 turn per volt. And in more powerful electronic transformers, half a turn or less - look at the photo below, which shows 60 and 160 watt transformers.
In the first case, the 12-volt winding contains 12 turns, and in the second only 6. Therefore, to obtain an acceptable 300 volt output voltage (to power a tube amplifier), you will need to wind up only 150 turns. If you need to get a lower voltage than 12V, we tap from the standard winding. Typical:
Just keep in mind that most of these pulse transformers do not start with a load current of less than 1A. The minimum current may vary for different models. And here read more about the modifications of Chinese electric vehicles that allow them to start even at low currents and are not afraid of short circuits.
About the power of electronic transformers. Don't trust too much what is written on the ET case. If it is labeled as a 160-watt transformer, then already at 100 watts the heating will be such that there is a risk of failure of the output key transistors. Therefore, mentally divide it in half. Or install transistors on normal radiators, not forgetting about thermal paste.
Prices for electronic transformers are comparable to those on hardware. So a 160-watt ET costs $5 in our electrical goods store, and a weaker 60-watt ET costs $3. In general, the only drawback of electronic transformers can be considered an increased level of RF interference and lower operational reliability. If you burnt it, there is no point in repairing it; the probability of a successful repair is not high (unless, of course, the problem is in the fuse at the 220V input). It's cheaper to just buy a new one.
Discuss the article ELECTRONIC STOP TRANSFORMER
Halogen lamps are increasingly used every day in decorating various shopping malls and shop windows. The bright colors and richness of the image rendering make them increasingly popular. Their service life is much longer than that of conventional lamps. At the same time, they can work for a long time without switching off. Halogen lamps use filaments, but the glow process is different in comparison with incandescent lamps due to the filling of the cylinder with a special composition. Such light bulbs are used in various lamps, chandeliers, kitchen furniture and come in 220 and 12 volt. A power supply for halogen lamps with a voltage of 12 volts is necessary, because when they are connected directly to electrical network a short circuit will occur.
Specifications
The voltage of halogen lamps is not only 220 and 12 volts. On sale you can find 24 and even 6 volt light bulbs. The power can also be different - 5, 10, 20 watts. Halogen lamps from 220 V are connected directly to the network. Those that operate on 12 V require special devices that convert current from the network to 12 volts - so-called transformers or special power supplies.
Twelve volt halogens work very well. Previously, in the 90s, a large 50 Hz transformer was used, which ensured the operation of only one halogen lamp. Modern lighting uses pulsed high frequency converters. They are very small in size, but can pull 2 - 3 lamps at the same time.
On the modern market there are both expensive and cheap power supplies. As a percentage of expensive ones, about 5% are sold, and much more cheap ones. Although, in principle, high cost is not a guarantee of reliability. Cool converters, unfortunately, do not use high-quality parts, but only use clever circuit “bells and whistles” that contribute to the normal operation of the power supply, at least during the warranty period. As soon as it runs out, the device burns out.
Classification
Transformers are electromagnetic and electronic (pulse). Electromagnetic ones are affordable, reliable, and can be made with your own hands if desired. They also have their disadvantages - decent weight, large overall dimensions, increased temperature during prolonged operation. And voltage drops significantly shorten the life of halogen lamps.
Electronic transformers weigh much less, they have a stable output voltage, they do not heat up too much, they can be protected against short circuits and smooth start, increasing the life of the lamp.
Transformers for halogen lamps
The analysis will be carried out using the example of a power supply from Feron German Technology. The output of this transformer is no less than 5 amperes. For such a small box the value is amazing. The case is made in a hermetically sealed manner, with the absence of any kind of ventilation. This is probably why some copies of such power supplies melt from high temperatures.
The converter circuit in the first version is very simple. The set of all the details is so minimal that it is unlikely that anything can be thrown out of it. When enumerating we see:
- diode bridge;
- RC circuit with a dinistor to start the generator;
- generator assembled on a half-bridge circuit;
- transformer that reduces the input voltage;
- low resistance resistor that serves as a fuse.
With a large voltage drop, such a converter will “die” 100%, taking the entire “blow” upon itself. Everything is made from a fairly cheap set of parts. Only there are no complaints about the transformers, because they are made to last.
The second option looks very weak and unfinished. Resistors R5 and R6 are inserted into the emitter circuits to limit the current. At the same time, the blocking of transistors in the event of a sharp increase in current is not thought out at all (it simply does not exist!). The electrical circuit (in the diagram it is red in the diagram) raises doubts.
The Feron German Technology company produces halogen lamps with a power of up to 60 watts. The output current of the power supply is 5 amperes. This is a bit much for such a light bulb.
When removing the cover, pay attention Special attention on the dimensions of the radiator. For a 5 amp output they are very small.
Calculation of transformer power for lamps and connection diagram
Various transformers are sold today, so there are certain rules for selecting the required power. You should not take a transformer that is too powerful. It will work practically idle. Lack of power will lead to overheating and further failure of the device.
You can calculate the power of the transformer yourself. The problem is rather mathematical and is within the capabilities of every novice electrician. For example, it is necessary to install 8 halogen spot lights with a voltage of 12 V and a power of 20 watts. The total power will be 160 watts. We take approximately a 10% margin and purchase a power of 200 watts.
Scheme No. 1 looks something like this: there is a single-key switch on line 220, with the orange and blue wires connected to the transformer input (primary terminals).
On the 12 volt line, all lamps are connected to a transformer (to the secondary terminals). Connecting copper wires must have the same cross-section, otherwise the brightness of the bulbs will be different.
Another condition: the wire connecting the transformer to the halogen lamps must be at least 1.5 meters long, preferably 3. If you make it too short, it will start to heat up and the brightness of the lamps will decrease.
Scheme No. 2 – for connecting halogen lamps. Here you can do things differently. Break, for example, six lamps into two parts. For each, install a step-down transformer. The correctness of this choice is due to the fact that if one of the power supplies breaks down, the second part of the lamps will still continue to work. The power of one group is 105 watts. With a small safety factor, we find that you need to purchase two 150-watt transformers.
Advice! Power each step-down transformer with its own wires and connect them in distribution box. Leave the connection points freely accessible.
Do-it-yourself power supply modification
To operate halogen lamps, pulsed current sources with high-frequency voltage conversion began to be used. During home production and setup, expensive transistors quite often burn out. Since the supply voltage in the primary circuits reaches 300 volts, very high requirements are placed on insulation. All these difficulties can be completely avoided by using a ready-made electronic transformer. It is used to power 12-volt halogen backlights (in stores), which are powered from a standard electrical outlet.
There is a certain opinion that getting a homemade switching power supply is a simple matter. You can only add a rectifier bridge, a smoothing capacitor and a voltage stabilizer. In reality, everything is much more complicated. If you connect an LED to the rectifier, then only one ignition can be detected when turned on. If you turn the converter off and on again, another flash will occur. In order for a constant glow to appear, it is necessary to connect an additional load to the rectifier, which, taking away useful power, would convert it into heat.
One of the options for self-manufacturing a switching power supply
The described power supply can be made from an electronic transformer with a power of 105 W. In practice, this transformer resembles a compact pulse voltage converter. For assembly, you will additionally need a matching transformer T1, a mains filter, a rectifier bridge VD1-VD4, and an output choke L2.
Bipolar power supply circuit Such a device operates stably for a long time with a low-frequency amplifier with a power of 2x20 watts. At 220 V and a current of 0.1 A, the output voltage will be 25 V; when the current increases to 2 amperes, the voltage drops to 20 volts, which is considered normal operation.
The current, bypassing the switch and fuses FU1 and FU2, goes to a filter that protects the circuit from interference from the pulse converter. The middle of capacitors C1 and C2 is connected to the shielding casing of the power supply. Then the current is supplied to input U1, from where a reduced voltage is supplied from the output terminals to the matching transformer T1. The alternating voltage from the other (secondary winding) rectifies the diode bridge and smoothes the L2C4C5 filter.
Self-assembly
Transformer T1 is manufactured independently. The number of turns on the secondary winding affects the output voltage. The transformer itself is made on a K30x18x7 ring magnetic core made of M2000NM ferrite. The primary winding consists of a PEV-2 wire with a diameter of 0.8 mm, folded in half. The secondary winding consists of 22 turns of PEV-2 wire, folded in half. By connecting the end of the first half-winding to the beginning of the second, we obtain the midpoint of the secondary winding. We also make the throttle ourselves. It is wound on the same ferrite ring, both windings contain 20 turns.
Rectifier diodes are located on a radiator with an area of at least 50 sq.cm. Please note that diodes whose anodes are connected to the negative output are insulated from the heat sink with mica spacers.
Smoothing capacitors C4 and C5 consist of three K50-46 connected in parallel with a capacity of 2200 μF each. This method is used to reduce the overall inductance of electrolytic capacitors.
It would be better to install a surge filter at the input of the power supply, but it is possible to work without it. For a line filter choke, you can use a DF of 50 Hz.
All parts of the power supply are mounted on a board made of insulating material. The resulting structure is placed in a shielding casing made of thin sheet brass or tinned sheet. Don't forget to drill holes in it for air ventilation.
A correctly assembled power supply does not require adjustment and starts working immediately. But just in case, you can check its performance by connecting a resistor with a resistance of 240 Ohms and a dissipation power of 3 W to the output.
Step-down transformers for halogen lamps generate a very large amount of heat during operation. Therefore, several requirements must be met:
- Do not connect the power supply without load.
- Place the unit on a non-flammable surface.
- The distance from the block to the light bulb is at least 20 centimeters.
- For better ventilation install the transformer in a niche with a volume of at least 15 liters.
A power supply is required for halogen lamps operating on 12 volts. It is a kind of transformer that lowers the input 220 V to the required values.
The operation of the transformer is based on converting current from a 220 V network. The devices are divided by the number of phases, as well as the overload indicator. Modifications of single-phase and two-phase types are available on the market. The current overload parameter ranges from 3 to 10 A. If necessary, you can make an electronic transformer with your own hands. However, to do this, it is first important to familiarize yourself with the structure of the model.
Model diagram
The electronic 12V circuit involves the use of a pass relay. The winding itself is used with a filter. To increase the clock frequency, there are capacitors in the circuit. They are produced open and closed type. For single-phase modifications, rectifiers are used. These elements are necessary to increase current conductivity.
On average, the sensitivity of the models is 10 mV. With the help of expanders, problems with network congestion are solved. If we consider a two-phase modification, then it uses a thyristor. The specified element is usually installed with resistors. Their capacity is on average 15 pF. The level of current conduction in this case depends on the relay load.
How to do it yourself?
You can easily do it yourself. For this it is important to use a wired relay. It is advisable to select an expander for it of the pulse type. To increase the sensitivity parameter of the device, capacitors are used. Many experts recommend installing resistors with insulators.
To solve problems with voltage surges, filters are soldered. If we consider a homemade single-phase model, then it is more appropriate to select a modulator for 20 W. The output impedance in the transformer circuit should be 55 Ohms. The output contacts are soldered directly to connect the device.
Devices with capacitor resistor
The electronic transformer circuit for 12V involves the use of a wired relay. In this case, resistors are installed behind the plate. Typically, modulators are used open type. Also, the electronic transformer circuit for 12V halogen lamps includes rectifiers that are matched with filters.
To solve switching problems, amplifiers are needed. The average output resistance is 45 ohms. Current conductivity, as a rule, does not exceed 10 microns. If we consider a single-phase modification, then it has a trigger. Some specialists use triggers to increase conductivity. However, in this case, heat losses increase significantly.
Transformers with regulator
The 220-12 V transformer with a regulator is quite simple. The relay in this case is usually used as a wired type. The regulator itself is installed with a modulator. To solve problems with reverse polarity there is a kenotron. It can be used with or without a cover.
The trigger in this case is connected through conductors. These elements can only work with pulse expanders. On average, the conductivity parameter of transformers of this type does not exceed 12 microns. It is also important to note that the negative resistance value depends on the sensitivity of the modulator. As a rule, it does not exceed 45 Ohms.
Using wire stabilizers
A 220-12 V transformer with a wire stabilizer is very rare. For normal operation of the device, a high-quality relay is necessary. The negative resistance indicator is on average 50 ohms. The stabilizer in this case is fixed on the modulator. This element is primarily intended to lower the clock frequency.
The heat losses from the transformer are insignificant. However, it is important to note that there is a lot of pressure on the trigger. Some experts recommend using capacitive filters in this situation. They are sold with or without a guide.
Models with diode bridge
A transformer (12 Volt) of this type is made on the basis of selective triggers. The threshold resistance of the models is on average 35 Ohms. To solve problems with frequency reduction, transceivers are installed. Directly diode bridges are used with different conductivities. If we consider single-phase modifications, then in this case the resistors are selected for two plates. The conductivity indicator does not exceed 8 microns.
Tetrodes in transformers can significantly increase the sensitivity of the relay. Modifications with amplifiers are very rare. The main problem with this type of transformers is negative polarity. It occurs due to an increase in the temperature of the relay. To remedy the situation, many experts recommend using triggers with conductors.
Model Taschibra
The electronic transformer circuit for 12V halogen lamps includes a trigger with two plates. The model's relay is of the wired type. To solve problems with reduced frequency, expanders are used. In total, the model has three capacitors. Therefore, network congestion problems rarely occur. On average, the output resistance parameter is kept at 50 Ohms. According to experts, the output voltage at the transformer should not exceed 30 W. On average, the sensitivity of the modulator is 5.5 microns. However, in this case it is important to take into account the load on the expander.
Device RET251C
The specified electronic transformer for lamps is produced with an output adapter. The model has a dipole type expander. There are a total of three capacitors installed in the device. A resistor is used to solve problems with negative polarity. The model's capacitors rarely overheat. The modulator is directly connected through a resistor. In total, the model has two thyristors. First of all, they are responsible for the output voltage parameter. Thyristors are also designed to ensure stable operation of the expander.
Transformer GET 03
The transformer (12 Volt) of this series is very popular. In total, the model has two resistors. They are located next to the modulator. If we talk about indicators, it is important to note that the modification frequency is 55 Hz. The device is connected via an output adapter.
The expander is matched with an insulator. To solve problems with negative polarity, two capacitors are used. There is no regulator in the presented modification. The conductivity index of the transformer is 4.5 microns. The output voltage fluctuates around 12 V.
Device ELTR-70
The specified 12V electronic transformer includes two pass-through thyristors. A distinctive feature of the modification is the high clock frequency. Thus, the current conversion process will be carried out without voltage surges. The model's expander is used without lining.
There is a trigger to reduce sensitivity. It is installed as a standard selective type. The negative resistance indicator is 40 ohms. For a single-phase modification this is considered normal. It is also important to note that the devices are connected via an output adapter.
Model ELTR-60
This transformer features high voltage stability. The model refers to single-phase devices. It uses a capacitor with high conductivity. Problems with negative polarity are solved by using an expander. It is installed behind the modulator. There is no regulator in the presented transformer. In total, the model uses two resistors. Their capacitance is 4.5 pF. According to experts, overheating of elements is observed very rarely. The output voltage to the relay is strictly 12 V.
Transformers TRA110
These transformers operate from a pass-through relay. The model’s expanders are used in different capacities. The average output impedance of the transformer is 40 ohms. The model belongs to two-phase modifications. Its threshold frequency is 55 Hz. In this case, dipole type resistors are used. In total, the model has two capacitors. To stabilize the frequency during operation of the device, a modulator operates. The conductors of the model are soldered with high conductivity.
Electronic transformers are replacing bulky steel core transformers. The electronic transformer itself, unlike the classical one, is a whole device - a voltage converter.
Such converters are used in lighting to power 12-volt halogen lamps. If you have repaired chandeliers with a remote control, then you have probably encountered them.
Here is a diagram of an electronic transformer JINDEL(model GET-03) with short circuit protection.
The main power elements of the circuit are npn transistors MJE13009, which are connected according to the half-bridge circuit. They operate in antiphase at a frequency of 30 - 35 kHz. All the power supplied to the load - halogen lamps EL1...EL5 - is pumped through them. Diodes VD7 and VD8 are necessary to protect transistors V1 and V2 from reverse voltage. A symmetrical dinistor (aka diac) is necessary to start the circuit.
On transistor V3 ( 2N5551) and elements VD6, C9, R9 - R11, a short circuit protection circuit is implemented at the output ( short circuit protection).
If a short circuit occurs in the output circuit, the increased current flowing through resistor R8 will cause transistor V3 to operate. The transistor will open and block the operation of the DB3 dinistor, which starts the circuit.
Resistor R11 and electrolytic capacitor C9 prevent false operation of the protection when the lamps are turned on. When the lamps are turned on, the filaments are cold, so the converter produces a significant current at the beginning of the start-up.
For straightening mains voltage 220V uses a classic bridge circuit of 1.5-amp diodes 1N5399.
Inductor L2 is used as a step-down transformer. It takes up almost half the space on the converter PCB.
Due to its internal structure, it is not recommended to turn on the electronic transformer without load. Therefore, the minimum power of the connected load is 35 - 40 watts. The operating power range is usually indicated on the product body. For example, on the body of the electronic transformer in the first photo the output power range is indicated: 35 - 120 watts. Its minimum load power is 35 watts.
It is better to connect halogen lamps EL1...EL5 (load) to an electronic transformer with wires no longer than 3 meters. Since significant current flows through the connecting conductors, long wires increase the total resistance in the circuit. Therefore, lamps located further away will shine dimmer than those located closer.
It is also worth considering that the resistance of long wires contributes to their heating due to the passage of significant current.
It is also worth noting that, due to their simplicity, electronic transformers are sources of high-frequency interference in the network. Typically, a filter is placed at the input of such devices to block interference. As we can see from the diagram, electronic transformers for halogen lamps do not have such filters. But in computer power supplies, which are also assembled using a half-bridge circuit and with a more complex master oscillator, such a filter is usually mounted.
Electronic transformers began to come into fashion quite recently. Essentially, it is a switching power supply that is designed to reduce the 220 Volt network to 12 Volts. Such transformers are used to power 12 Volt halogen lamps. The power of electric vehicles produced today is 20-250 watts. The designs of almost all schemes of this kind are similar to each other. This is a simple half-bridge inverter, quite unstable in operation. The circuits do not have short circuit protection at the output of the pulse transformer. Another disadvantage of the circuit is that generation occurs only when a load of a certain size is connected to the secondary winding of the transformer. I decided to write the article because I believe that the ET can be used in amateur radio designs as a power source if some simple alternative solutions are introduced into the ET circuit. The essence of the modification is to supplement the circuit with short-circuit protection and force the electric vehicle to turn on when mains voltage is applied and without a light bulb at the output. In fact, the conversion is quite simple and does not require special electronics skills. The diagram is shown below, with changes in red.
On the ET board we can see two transformers - the main (power) and the OS transformer. The OS transformer contains 3 separate windings. Two of them are the basic windings of power switches and consist of 3 turns. On the same transformer there is another winding, which consists of only one turn. This winding is connected in series to the mains winding of the pulse transformer. It is this winding that needs to be removed and replaced with a jumper. Next you need to look for a resistor with a resistance of 3-8 Ohms (the operation of short-circuit protection depends on its value). Then we take a wire with a diameter of 0.4-0.6 mm and wind two turns on the pulse transformer, then 1 turn on the OS transformer. We select an OS resistor with a power from 1 to 10 watts; it will heat up, and quite strongly. In my case, a wire-wound resistor with a resistance of 6.2 Ohms was used, but I do not recommend using them, since the wire has some inductance, which may affect the further operation of the circuit, although I can’t say for sure - time will tell.
If there is a short circuit at the output, the protection will immediately work. The fact is that the current in the secondary winding of the pulse transformer, as well as in the windings of the OS transformer, will drop sharply, this will lead to the key transistors being turned off. To smooth out network noise, a choke is installed at the power input, which was soldered from another UPS. After the diode bridge, it is advisable to install electrolytic capacitor with a voltage of at least 400 Volts, select the capacity based on the calculation of 1 μF per 1 watt.
But even after the modification, you should not short-circuit the output winding of the transformer for more than 5 seconds, since the power switches will heat up and may fail. A switching power supply converted in this way will turn on without any output load at all. In the event of a short circuit at the output, generation is disrupted, but the circuit will not be damaged. An ordinary ET, when the output is closed, simply burns out instantly:
Continuing to experiment with blocks of electronic transformers for powering halogen lamps, you can modify the pulse transformer itself, for example, to obtain an increased bipolar voltage to power a car amplifier.
The transformer in the UPS of halogen lamps is made on a ferrite ring, and from the looks of this ring you can squeeze out the required watts. All factory windings were removed from the ring and new ones were wound in their place. The output transformer must provide bipolar voltage - 60 volts per arm.
To wind the transformer, we used wire from Chinese ordinary iron transformers (included in the Sega set-top box). Wire - 0.4 mm. The primary winding is wound with 14 wires, first 5 turns around the entire ring, do not cut the wire! After winding 5 turns, we make a tap, twist the wire and wind 5 more. This solution will eliminate the difficult phasing of the windings. The primary winding is ready.
The secondary also shakes. The winding consists of 9 cores of the same wire, one arm consists of 20 turns, it is also wound around the entire frame, then a tap and we wind another 20 turns.
To clean the varnish, I simply lit the wires on fire with a lighter, then cleaned them with a nail knife and wiped the ends with solvent. I must say - it works great! At the output I received the required 65 volts. In further articles we will look at options of this kind, and also add a rectifier at the output, turning the ET into a full-fledged switching power supply that can be used for almost any purpose.
