When developing a regulated power supply without a high-frequency converter, the developer faces such a problem that with a minimum output voltage and a high load current on the regulating element, the stabilizer dissipates a lot of power. Until now, in most cases, this problem was solved as follows: they made several taps at the secondary winding of the power transformer and divided the entire range of output voltage adjustment into several subranges. This principle is used in many serial power supplies, for example, UIP-2 and more modern ones. It is clear that the use of a power supply with multiple subranges becomes more complicated, and the remote control of such a power supply, for example, from a computer, also becomes more complicated.
The solution seemed to me to be the use of a controlled rectifier on a thyristor, since it becomes possible to create a power source controlled by one output voltage setting knob or one control signal with an output voltage adjustment range from zero (or almost zero) to the maximum value. Such a power supply can be made from commercially available parts.
To date, controlled rectifiers with thyristors have been described in great detail in books on power supplies, but are rarely used in practice in laboratory power supplies. In amateur designs, they are also rare (except, of course, for car battery chargers). I hope that this work will help change this state of affairs.
In principle, the circuits described here can be used to stabilize the input voltage of a high-frequency converter, for example, as is done in Elektronika Ts432 TVs. The circuits shown here can also be used to make laboratory power supplies or chargers.
I give the description of my works not in the order in which I carried them out, but more or less ordered. Let's look at general issues first, then "low-voltage" designs such as power supplies for transistor circuits or battery charging, and then "high-voltage" rectifiers for powering vacuum tube circuits.
Operation of a thyristor rectifier for a capacitive load
The literature describes a large number of thyristor power controllers operating on alternating or pulsating current with active (for example, incandescent lamps) or inductive (for example, an electric motor) load. The rectifier load is usually a filter in which capacitors are used to smooth out ripples, so the rectifier load can be capacitive in nature.
Consider the operation of a rectifier with a thyristor controller for a resistive-capacitive load. A diagram of such a regulator is shown in fig. 1.
Rice. 1.
Here, for example, a full-wave rectifier with a midpoint is shown, however, it can also be made according to another scheme, for example, a bridge. Sometimes thyristors, in addition to regulating the voltage on the load U n they also perform the function of rectifying elements (valves), however, this mode is not allowed for all thyristors (KU202 thyristors with some letters allow operation as valves). For the sake of clarity, let's assume that thyristors are only used to regulate the voltage across the load. U n , and straightening is done by other devices.
The principle of operation of the thyristor voltage regulator is illustrated in Fig. 2. At the output of the rectifier (the connection point of the cathodes of the diodes in Fig. 1), voltage pulses are obtained (the lower half-wave of the sinusoid is “turned” up), indicated U rec . Pulsation frequency f p at the output of a full-wave rectifier is equal to twice the mains frequency, i.e. 100 Hz when powered by mains 50 Hz . The control circuit supplies the control electrode of the thyristor with current pulses (or light if an optothyristor is used) with a certain delay t relative to the beginning of the ripple period, i.e., the moment when the rectifier voltage U rec becomes zero.
Rice. 2.
Figure 2 is made for the case when the delay t exceeds half the period of pulsations. In this case, the circuit operates on the incident part of the sinusoid wave. The longer the thyristor turn-on delay, the lower the rectified voltage will be. U n on load. Voltage ripple on the load U n smoothed by a filter capacitor C f . Here and below, some simplifications are made when considering the operation of the circuits: the output impedance of the power transformer is assumed to be zero, the voltage drop across the rectifier diodes is not taken into account, and the thyristor turn-on time is not taken into account. It turns out that the recharging of the filter capacitance C f happens instantly. In reality, after a trigger pulse is applied to the control electrode of the thyristor, the filter capacitor takes some time to charge, which, however, is usually much less than the pulsation period T p.
Now imagine that the thyristor turn-on delay t is equal to half the pulsation period (see Fig. 3). Then the thyristor will turn on when the voltage at the rectifier output passes through the maximum.
Rice. 3.
In this case, the load voltage U n will also be the largest, approximately the same as if there were no thyristor regulator in the circuit (we neglect the voltage drop across the open thyristor).
This is where we run into a problem. Suppose we want to regulate the load voltage from almost zero to the highest value that can be obtained from the available power transformer. To do this, taking into account the assumptions made earlier, it will be necessary to apply triggering pulses to the thyristor EXACTLY at the moment when U rec passes through a maximum, i.e. t c \u003d T p /2. Taking into account the fact that the thyristor does not open instantly, but recharging the filter capacitor C f also requires some time, the triggering pulse must be applied a little BEFORE half of the pulsation period, i.e. t< T п /2. The problem is that, firstly, it is difficult to say how much earlier, because it depends on such reasons that are difficult to accurately take into account when calculating, for example, the turn-on time of a given thyristor instance or the total (including inductances) output resistance of a power transformer. Secondly, even if the calculation and adjustment of the circuit is absolutely accurate, the turn-on delay time t , the frequency of the network, and hence the frequency and period T p ripple, thyristor turn-on time and other parameters may change over time. Therefore, in order to get the highest voltage on the load U n there is a desire to turn on the thyristor much earlier than half the pulsation period.
Suppose that we did so, i.e., set the delay time t much smaller T p /2. Graphs characterizing the operation of the circuit in this case are shown in Fig. 4. Note that if the thyristor opens before half a half cycle, it will remain open until the process of charging the filter capacitor is completed. C f (see the first pulse in Fig. 4).
Rice. 4.
It turns out that for a short delay t possible fluctuations in the output voltage of the regulator. They occur if, at the moment the triggering pulse is applied to the thyristor, the voltage on the load U n there is more voltage at the output of the rectifier U rec . In this case, the thyristor is under reverse voltage and cannot open under the action of a triggering pulse. One or more trigger pulses may be missed (see second pulse in Figure 4). The next turn on of the thyristor will occur when the filter capacitor is discharged and at the moment the control pulse is applied, the thyristor will be under direct voltage.
Probably the most dangerous is the case when every second impulse is missed. In this case, a direct current will pass through the winding of the power transformer, under the influence of which the transformer may fail.
In order to avoid the appearance of an oscillatory process in the thyristor controller circuit, it is probably possible to abandon the pulse control of the thyristor, but in this case the control circuit becomes more complicated or becomes uneconomical. Therefore, the author has developed a thyristor regulator circuit in which the thyristor is normally triggered by control pulses and no oscillatory process occurs. Such a scheme is shown in Fig. 5.
Rice. 5.
Here the thyristor is loaded on the starting resistance R p , and the filter capacitor C R n connected via start diode VD n . In such a circuit, the thyristor starts up regardless of the voltage across the filter capacitor C f .After a trigger pulse is applied to the thyristor, its anode current first begins to pass through the starting resistance R p and, then, when the voltage is on R p exceed the load voltage U n , the starting diode opens VD n and the anode current of the thyristor recharges the filter capacitor C f . Resistance R p such a value is chosen to ensure a stable start of the thyristor with a minimum delay time of the triggering pulse t . It is clear that some power is wasted on the starting resistance. Therefore, in the above circuit, it is preferable to use thyristors with a low holding current, then it will be possible to apply a large starting resistance and reduce power losses.
The scheme in fig. 5 has the disadvantage that the load current passes through an additional diode VD n , on which part of the rectified voltage is uselessly lost. This drawback can be eliminated by connecting a starting resistance R p to a separate rectifier. A circuit with a separate control rectifier from which the start circuit and starting resistance are powered R p shown in fig. 6. In this circuit, the control rectifier diodes can be low-power, since the load current flows only through the power rectifier.
Rice. 6.
Low voltage power supplies with thyristor regulator
Below is a description of several designs of low voltage rectifiers with a thyristor regulator. In their manufacture, I took as a basis the circuit of a thyristor regulator used in devices for charging car batteries (see Fig. 7). This scheme was successfully used by my late comrade A. G. Spiridonov.
Rice. 7.
The elements circled in the diagram (Fig. 7) were installed on a small printed circuit board. Several similar schemes are described in the literature, the differences between them are minimal, mainly in the types and ratings of parts. The main differences are:
1. Time-setting capacitors of different capacities are used, i.e. instead of 0.5m F put 1 m F , and, accordingly, a variable resistance of another value. For the reliability of starting the thyristor in my circuits, I used a capacitor for 1m F.
2. Parallel to the time-setting capacitor, you can not put resistance (3 k Win fig. 7). It is clear that this may require a variable resistance not 15 k W, but a different value. I have not yet found out the influence of the resistance parallel to the time-setting capacitor on the stability of the circuit.
3. In most circuits described in the literature, transistors of the KT315 and KT361 types are used. Sometimes they fail, so in my circuits I used more powerful transistors of the KT816 and KT817 types.
4. To base connection point pnp and npn collector transistors, a divider can be connected from resistances of a different value (10 k W and 12k W in fig. 7).
5. A diode can be installed in the control electrode circuit of the thyristor (see the diagrams below). This diode eliminates the effect of the thyristor on the control circuit.
The diagram (Fig. 7) is given as an example, several similar diagrams with descriptions can be found in the book “Chargers and start-chargers: An information review for motorists / Comp. A. G. Khodasevich, T. I. Khodasevich - M.: NT Press, 2005”. The book consists of three parts, it contains almost all the chargers in the history of mankind.
The simplest rectifier circuit with a thyristor voltage regulator is shown in fig. 8.
Rice. 8.
This circuit uses a full-wave mid-point rectifier because it contains fewer diodes, so fewer heatsinks are needed and higher efficiency. The power transformer has two secondary windings for alternating voltage 15 V . The thyristor control circuit here consists of a capacitor C1, resistances R 1- R 6, transistors VT 1 and VT 2, diode VD 3.
Let's consider how the circuit works. Capacitor C1 is charged through a variable resistance R 2 and constant R 1. When the voltage across the capacitor C 1 will exceed the voltage at the connection point of the resistances R4 and R 5, open the transistor VT 1. Collector current of the transistor VT 1 opens VT 2. In turn, the collector current VT 2 opens VT 1. Thus, the transistors open like an avalanche and the capacitor is discharged C 1 to thyristor control electrode VS 1. This is how the triggering impulse is obtained. By changing the variable resistance R 2 trigger pulse delay time, the output voltage of the circuit can be adjusted. The greater this resistance, the slower the capacitor charges. C 1, the trigger pulse delay time is longer and the output voltage at the load is lower.
Constant resistance R 1, connected in series with a variable R 2 limits the minimum pulse delay time. If it is greatly reduced, then at the minimum position of the variable resistance R 2, the output voltage will abruptly disappear. That's why R 1 is selected in such a way that the circuit works stably at R 2 in the position of minimum resistance (corresponding to the highest output voltage).
The circuit uses resistance R 5 power 1 W only because it came to hand. It will probably suffice to install R 5 with a power of 0.5 W.
resistance R 3 is set to eliminate the influence of interference on the operation of the control circuit. Without it, the circuit works, but is sensitive, for example, to touching the terminals of transistors.
Diode VD 3 eliminates the influence of the thyristor on the control circuit. In experience, I checked and made sure that the circuit works more stable with a diode. In short, you don’t need to skimp, it’s easier to put the D226, whose reserves are inexhaustible and make a reliable device.
resistance R 6 in thyristor control electrode circuit VS 1 increases the reliability of its operation. Sometimes this resistance is set to a larger value or not set at all. The circuit without it usually works, but the thyristor can spontaneously open due to interference and leakage in the control electrode circuit. I have installed R 6 value 51 Was recommended in the reference data of thyristors KU202.
Resistance R 7 and diode VD 4 provide a reliable start of the thyristor with a short delay time of the triggering pulse (see Fig. 5 and explanations to it).
Capacitor C 2 smoothes the voltage ripple at the output of the circuit.
As a load during the experiments, the regulator used a lamp from a car headlight.
A diagram with a separate rectifier for powering the control circuits and starting the thyristor is shown in fig. 9.
Rice. 9.
The advantage of this circuit is a smaller number of power diodes that require installation on radiators. Note that the diodes D242 of the power rectifier are connected by cathodes and can be installed on a common radiator. The anode of the thyristor connected to its case is connected to the “minus” of the load.
The wiring diagram of this version of the controlled rectifier is shown in fig. 10.
Rice. 10.
To smooth the ripple of the output voltage can be applied LC -filter. A diagram of a controlled rectifier with such a filter is shown in fig. eleven.
Rice. eleven.
I applied exactly LC -filter for the following reasons:
1. It is more resistant to overloads. I was designing a circuit for a laboratory power supply, so overloading it is quite possible. I note that even if you make any protection scheme, it will have some response time. During this time, the power supply should not fail.
2. If you make a transistor filter, then some voltage will definitely drop across the transistor, so the efficiency will be low, and the transistor may need a radiator.
The filter uses a serial inductor D255V.
Consider possible modifications of the thyristor control circuit. The first of them is shown in Fig. 12.
Rice. 12.
Usually, the time-setting circuit of a thyristor regulator is made from a time-setting capacitor and a variable resistance connected in series. Sometimes it is convenient to build a circuit so that one of the outputs of the variable resistance is connected to the "minus" of the rectifier. Then you can turn on the variable resistance in parallel with the capacitor, as done in Figure 12. When the engine is in the lower position according to the circuit, the main part of the current passing through the resistance 1.1 k Wenters the time-setting capacitor 1mF and charges it quickly. In this case, the thyristor starts at the “tops” of the rectified voltage ripples or a little earlier, and the output voltage of the regulator is the highest. If the engine is in the upper position according to the diagram, then the timing capacitor is shorted and the voltage on it will never open the transistors. In this case, the output voltage will be zero. By changing the position of the variable resistance slider, it is possible to change the strength of the current charging the timing capacitor and, thus, the delay time of the triggering pulses.
Sometimes it is required to control the thyristor regulator not with the help of a variable resistance, but from some other circuit (remote control, control from a computer). It happens that the parts of the thyristor regulator are under high voltage and direct connection to them is dangerous. In these cases, an optocoupler can be used instead of a variable resistance.
Rice. 13.
An example of including an optocoupler in a thyristor controller circuit is shown in fig. 13. Type 4 transistor optocoupler is used here N 35. The base of its phototransistor (pin 6) is connected through a resistance to the emitter (pin 4). This resistance determines the gain of the optocoupler, its speed and resistance to temperature changes. The author tested the regulator with a resistance of 100 indicated in the diagram k W, while the dependence of the output voltage on temperature turned out to be NEGATIVE, i.e., with a very strong heating of the optocoupler (the PVC insulation of the wires melted), the output voltage decreased. This is probably due to a decrease in the output of the LED when heated. The author thanks S. Balashov for advice on the use of transistor optocouplers.
Rice. 14.
When adjusting the thyristor control circuit, it is sometimes useful to adjust the transistor threshold. An example of such adjustment is shown in Fig. 14.
Consider also an example of a circuit with a thyristor regulator for a higher voltage (see Fig. 15). The circuit is powered by the secondary winding of the TCA-270-1 power transformer, which provides an alternating voltage of 32 V . The ratings of the parts indicated in the diagram are selected for this voltage.
Rice. 15.
The scheme in fig. 15 allows you to smoothly adjust the output voltage from 5 V to 40 V , which is sufficient for most semiconductor devices, so this circuit can be taken as the basis for the manufacture of a laboratory power supply.
The disadvantage of this circuit is the need to dissipate a sufficiently large power on the starting resistance R 7. It is clear that the smaller the holding current of the thyristor, the greater the value can be and the lower the power of the starting resistance R 7. Therefore, it is preferable to use thyristors with low holding current.
In addition to conventional thyristors, an optothyristor can be used in the thyristor regulator circuit. On fig. 16. shows a circuit with a TO125-10 optothyristor.
Rice. 16.
Here, the optothyristor is simply turned on instead of the usual one, but since its photothyristor and LED are isolated from each other, the schemes for its use in thyristor regulators may be different. Note that due to the low holding current of thyristors TO125, the starting resistance R 7 requires less power than in the circuit in fig. 15. Since the author was afraid to damage the optothyristor LED with high pulsed currents, resistance R6 was included in the circuit. As it turned out, the circuit works without this resistance, and without it, the circuit works better at low output voltages.
High voltage power supplies with thyristor regulator
When developing high-voltage power supplies with a thyristor regulator, the optothyristor control circuit developed by V.P. Burenkov (PRZ) for welding machines was taken as a basis. Printed circuit boards have been developed and are being produced for this circuit. The author is grateful to V.P. Burenkov for a sample of such a board. A diagram of one of the layouts of an adjustable rectifier using a board designed by Burenkov is shown in fig. 17.
Rice. 17.
The parts installed on the printed circuit board are circled in the diagram with a dotted line. As can be seen from fig. 16, quenching resistances are installed on the board R1 and R 2, rectifier bridge VD 1 and zener diodes VD 2 and VD 3. These parts are for 220V mains power V . To test the thyristor regulator circuit without alterations in the printed circuit board, a TBS3-0.25U3 power transformer was used, the secondary winding of which is connected in such a way that an alternating voltage of 200 is removed from it. V , i.e. close to the normal supply voltage of the board. The control circuit works in the same way as described above, i.e., the capacitor C1 is charged through a trimmer R 5 and a variable resistance (installed off-board) until the voltage across it exceeds the voltage at the base of the transistor VT 2, after which the transistors VT 1 and VT2 open and the capacitor C1 is discharged through the opened transistors and the optocoupler thyristor LED.
The advantage of this circuit is the ability to adjust the voltage at which the transistors open (using R 4), as well as the minimum resistance in the timing circuit (using R 5). As practice shows, having the possibility of such adjustment is very useful, especially if the circuit is assembled in amateur conditions from random parts. With the help of tuning resistors R4 and R5, it is possible to achieve voltage regulation over a wide range and stable operation of the regulator.
With this circuit, I began my R&D work on the development of a thyristor regulator. In it, the skipping of triggering pulses was also detected when the thyristor operated on a capacitive load (see Fig. 4). The desire to improve the stability of the regulator led to the appearance of the circuit in Fig. 18. In it, the author tested the operation of a thyristor with starting resistance (see Fig. 5.
Rice. 18.
In the scheme of Fig. 18. used the same board as in the diagram of fig. 17, only the diode bridge was removed from it, because here, one common rectifier is used for the load and the control circuit. Note that in the diagram in Fig. 17, the starting resistance is selected from several connected in parallel to determine the maximum possible value of this resistance, at which the circuit begins to work stably. A wire resistance 10 is connected between the optothyristor cathode and the filter capacitor.W. It is needed to limit the current surges through the optoristor. Until this resistance was set, after turning the variable resistance knob, the optothyristor passed one or more whole half-waves of the rectified voltage into the load.
Based on the experiments carried out, a rectifier circuit with a thyristor regulator was developed, suitable for practical use. It is shown in fig. 19.
Rice. 19.
Rice. 20.
PCB SCR 1M 0 (Fig. 20) is designed for installation on it of modern small-sized electrolytic capacitors and wire resistances in a ceramic case of the type SQP . The author expresses his gratitude to R. Peplov for his help with the fabrication and testing of this printed circuit board.
Since the author was developing a rectifier with the highest output voltage of 500 V , it was necessary to have some reserve for the output voltage in case of a decrease in the mains voltage. It was possible to increase the output voltage if the windings of the power transformer were reconnected, as shown in fig. 21.
Rice. 21.
Note also that the diagram in Fig. 19 and board fig. 20 are designed with the possibility of their further development. For this on board SCR 1M 0 there are additional conclusions from the common wire GND 1 and GND 2, from the rectifier DC 1
Development and adjustment of a rectifier with a thyristor regulator SCR 1M 0 were carried out jointly with student R. Pelov at PSU. C with his help, photographs of the module were taken SCR 1M 0 and waveforms.
Rice. 22. View of the SCR 1 M module 0 part side
Rice. 23. View of the module SCR 1M 0 solder side
Rice. 24. View of the module SCR 1 M 0 on the side
Table 1. Oscillograms at low voltage
|
No. p / p |
Minimum voltage regulator position |
According to the scheme |
Notes |
|
On the cathode VD5 |
5 V/div 2 ms/div |
||
|
|
On capacitor C1 |
2 V/div 2 ms/div |
|
|
|
ie connections R2 and R3 |
2 V/div 2 ms/div |
|
|
|
At the anode of the thyristor |
100 V/div 2 ms/div |
|
|
|
At the thyristor cathode |
50 V/div 2 ms/de |
Table 2. Oscillograms at medium voltage
|
No. p / p |
Middle position of the voltage regulator |
According to the scheme |
Notes |
|
|
On the cathode VD5 |
5 V/div 2 ms/div |
|
|
|
On capacitor C1 |
2 V/div 2 ms/div |
|
|
|
ie connections R2 and R3 |
2 V/div 2 ms/div |
|
|
|
At the anode of the thyristor |
100 V/div 2 ms/div |
|
|
|
At the thyristor cathode |
100 V/div 2 ms/div |
Table 3. Oscillograms at maximum voltage
|
No. p / p |
Maximum voltage regulator position |
According to the scheme |
Notes |
|
|
On the cathode VD5 |
5 V/div 2 ms/div |
|
|
|
On capacitor C1 |
1 V/div 2 ms/div |
|
|
|
ie connections R2 and R3 |
2 V/div 2 ms/div |
|
|
|
At the anode of the thyristor |
100 V/div 2 ms/div |
|
|
|
At the thyristor cathode |
100 V/div 2 ms/div |
To get rid of this shortcoming, the regulator circuit was changed. Two thyristors were installed - each for its own half-cycle. With these changes, the circuit was tested for several hours and no “outliers” were noticed.
Rice. 25. SCR 1 M 0 scheme with modifications
A simple thyristor charger.
A device with electronic control of the charging current, made on the basis of a thyristor phase-pulse power controller.
It does not contain scarce parts; with obviously working parts, it does not require adjustment.
The charger allows you to charge car batteries with a current of 0 to 10 A, and can also serve as an adjustable power source for a powerful low-voltage soldering iron, vulcanizer, portable lamp.
Charging current is close to pulsed in shape, which is believed to help prolong battery life.
The device is operable at ambient temperature from - 35 °С to + 35 °С.
The scheme of the device is shown in fig. 2.60.
The charger is a thyristor power regulator with phase-pulse control, fed from the winding II of the step-down transformer T1 through the diode moctVDI + VD4.
The thyristor control unit is made on the analog of the unijunction transistor VTI, VT2. The time during which the capacitor C2 is charged before switching the unijunction transistor can be adjusted by the variable resistor R1. When the position of its engine is at the extreme right in the diagram, the charging current will become maximum, and vice versa.
Diode VD5 protects the control circuit of the thyristor VS1 from the reverse voltage that appears when the thyristor is turned on.
In the future, the charger can be supplemented with various automatic units (shutdown at the end of charging, maintaining normal battery voltage during long-term storage, signaling the correct polarity of the battery connection, protection against output short circuits, etc.).
The shortcomings of the device include - fluctuations in the charging current with an unstable voltage of the electric lighting network.
Like all similar thyristor phase-pulse controllers, the device interferes with radio reception. To combat them, it is necessary to provide a network LC- a filter similar to that used in switching power supplies.
Capacitor C2 - K73-11, with a capacity of 0.47 to 1 μF, or K73-16, K73-17, K42U-2, MBGP.
Replace the KT361A transistor with KT361B -- KT361Yo, KT3107L, KT502V, KT502G, KT501Zh - KT50IK, and KT315L - on KT315B + KT315D KT312B, KT3102L, KT503V + KT503G, P307. Instead of KD105B, diodes KD105V, KD105G or D226 with any letter index are suitable.
Variable resistor R1- SP-1, SPZ-30a or SPO-1.
Ammeter RA1 - any direct current with a scale of 10 A. It can be made independently from any milliammeter by selecting a shunt according to a standard ammeter.
fuse F1- fusible, but it is convenient to use a network machine for 10 A or an automobile bimetallic for the same current.
Diodes VD1 + VP4 can be any for a forward current of 10 A and a reverse voltage of at least 50 V (series D242, D243, D245, KD203, KD210, KD213).
Rectifier diodes and a thyristor are placed on heat sinks, each with a useful area of \u200b\u200babout 100 cm *. To improve the thermal contact of devices with heat sinks, it is better to use heat-conducting pastes.
Instead of the KU202V thyristor, KU202G - KU202E are suitable; It has been verified in practice that the device operates normally with more powerful thyristors T-160, T-250.
It should be noted that it is possible to use the iron wall of the casing directly as a thyristor heat sink. Then, however, there will be a negative output of the device on the case, which is generally undesirable because of the threat of inadvertent short circuits of the output positive wire to the case. If you strengthen the thyristor through a mica gasket, there will be no threat of a short circuit, but the heat transfer from it will worsen.
A ready-made network step-down transformer of the required power with a secondary winding voltage of 18 to 22 V can be used in the device.
If the transformer has a voltage on the secondary winding of more than 18 V, the resistor R5 should be replaced by others, the highest resistance (for example, at 24 * 26 V, the resistance of the resistor should be increased to 200 ohms).
In the case when the secondary winding of the transformer has a tap from the middle, or there are two uniform windings and the voltage of each is within the specified limits, then it is better to perform the rectifier according to the usual full-wave circuit on 2 diodes.
With a voltage of the secondary winding of 28 * 36 V, you can completely abandon the rectifier - its role will be simultaneously played by the thyristor VS1( rectification - half-wave). For this version of the power supply, you need between the resistor R5 and connect a separating diode KD105B or D226 with any letter index with a positive wire (cathode to resistor R5). The choice of a thyristor in such a circuit will become limited - only those that allow operation under reverse voltage are suitable (for example, KU202E).
For the described device, a unified transformer TN-61 is suitable. 3 of its secondary windings must be connected in series, while they are capable of delivering current up to 8 A.
All parts of the device, except for the transformer T1, diodes VD1 + VD4 rectifier, variable resistor R1, fuse FU1 and thyristor VS1, mounted on a printed circuit board made of foil fiberglass with a thickness of 1.5 mm.
A drawing of the board is featured in Radio Magazine #11, 2001.
They gave me a block that was still incomprehensible from Soviet times. It looks like some kind of power regulator or something. By itself, it did not represent any value, but the KU202 available in it really wanted to be adapted somewhere.
I want to bring to your attention a small experiment with phase-pulse charging. The well-known scheme was taken as a basis
The purpose of the experiment is to make the circuit more reliable and practical.
The circuit is also well suited to this charger.
How much will a similar charger cost?
KU202 80*2=160
BD140/139 15*2=26
Diodes D4/5/8 3*5=15
Diodes D1/2 2*100=200
Resistors 9*3=27
Potentiometer 60
Capacitor 20
Textolite 50
And that 558R plus a transformer 1500R and, if desired, an ammeter + 500R.
It's good to have something of your own. For this scheme as a whole, I paid 300R, having bought a trifle.
Charging on KU202, just an experiment. For safe, high-quality and reliable charging of any types of batteries, I recommend this
With uv. Admin check
Many questions are asked about this charger. I post the most interesting ones here. Write comments at the bottom of the page
-Did I understand you correctly that this scheme has some nuances?
-Yes, it has. each time before connecting to the battery, it is necessary to set the voltage in the region of 14.4V or 16.5 "for some calcium". The voltage is not stable and depends on the voltage in the primary winding of the transformer. in general Protection has no current and voltage stabilization
-How long have you been using it?
— This one was used by 2 battery charges 65A
How did she present herself?
-Charged, but you have to control the voltage all the time
-I would supplement it with voltage control, for automatic shutdown
- It’s easier to assemble the scheme that you were offered. Supplementing that scheme is just hemorrhoids
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Do not want to delve into the routine of radio electronics? I recommend paying attention to the proposals of our Chinese friends. For a very reasonable price, you can buy pretty high-quality chargers
Simple charger with LED charging indicator, green battery is charging, red battery is charged.
There is short circuit protection and reverse polarity protection. Perfect for charging Moto batteries with a capacity of up to 20A\h, a 9A\h battery will charge in 7 hours, 20A\h in 16 hours. Price for this charger 403 rubles, delivery is free
This type of charger is able to automatically charge almost any type of car and motorcycle batteries 12V up to 80Ah. It has a unique charging method in three stages: 1. Constant current charging, 2. Constant voltage charging, 3. Trickle charging up to 100%.
There are two indicators on the front panel, the first indicates the voltage and percentage of charge, the second indicates the charging current.
Pretty high-quality device for home use, the price of everything 781.96 rubles, delivery is free. At the time of this writing number of orders 1392, grade 4.8 out of 5. europlug
Charger for a wide variety of types of batteries 12-24V with current up to 10A and peak current 12A. Able to charge Helium batteries and SA \ SA. The charging technology is the same as the previous one in three stages. The charger is capable of charging both in automatic mode and in manual mode. The panel has an LCD indicator indicating voltage, charge current and percentage of charge.
A good device if you need to charge all possible types of batteries of any capacity, up to 150A / h
Price for this miracle 1 625 rubles, delivery is free. At the time of this writing, the number orders 23, grade 4.7 out of 5. When ordering, do not forget to specify europlug
If a product has become unavailable, please write in the comment at the bottom of the page.
With uv. Edward
The need to charge a car battery occurs regularly among our compatriots. Someone does this because of the battery discharge, someone - as part of maintenance. In any case, the presence of a charger (charger) greatly facilitates this task. Read more about what a thyristor charger for a car battery is and how to make such a device according to the scheme - read below.
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Description of thyristor memory
The thyristor charger is a device with electronically controlled charging current. Such devices are made on the basis of a thyristor power controller, which is phase-pulse. There are no scarce components in a memory device of this type, and if all its parts are intact, then it will not even have to be adjusted after manufacture.
With the help of such a charger, you can charge the vehicle battery with a current from zero to ten amperes. In addition, it can be used as a regulated power source for certain devices, for example, a soldering iron, portable lamp, etc. In its form, the charging current is very similar to the pulse, and the latter, in turn, allows you to extend the life of the battery. The use of a thyristor charger is allowed in the temperature range from -35 to +35 degrees.
Scheme
If you decide to build a thyristor charger with your own hands, then you can use many different schemes. Consider the description using the example of circuit 1. In this case, the thyristor charger is powered from winding 2 of the transformer assembly through the VDI + VD4 diode bridge. The control element is made in the form of an analogue of a unijunction transistor. In this case, using a variable resistor element, you can adjust the time during which the charge of the capacitor component C2 will be carried out. If the position of this part is the extreme right, then the charging current indicator will be the largest, and vice versa. Thanks to the diode VD5, the control circuit of the thyristor VS1 is protected.
Advantages and disadvantages
The main advantage of such a device is high-quality current charging, which will allow not to destroy, but to increase the life of the battery as a whole.
If necessary, the memory can be supplemented with all kinds of automatic components designed for such options:
- the device will be able to turn off automatically when charging is completed;
- maintaining the optimal voltage of the battery in case of long-term storage without operation;
- another feature that can be regarded as an advantage - the thyristor charger can inform the car owner about whether he connected the battery polarity correctly, and this is very important when charging;
- also, in the case of adding additional components, another advantage can be realized - protecting the node from output short circuits (the author of the video is the Blaze Electronics channel).
As for the shortcomings directly, they include fluctuations in the charging current if the voltage in the household network is unstable. In addition, like other thyristor controllers, such a charger can create certain interference with signal transmission. To prevent this, it is necessary to additionally install an LC filter during the manufacture of the memory. Such filter elements are used, for example, in mains power supplies.
How to make a memory yourself?
If we talk about the production of memory with our own hands, then we will consider this process using the example of scheme 2. In this case, thyristor control is carried out by means of a phase shift. We will not describe the whole process, since it is individual in each case, depending on the addition of additional components to the design. Below we consider the main nuances that should be considered.
In our case, the device is assembled on a regular hardboard, including a capacitor:
- Diode elements, marked on the diagram as VD1 and VD 2, as well as thyristors VS1 and VS2, should be installed on a heat sink, the installation of the latter is allowed on a common heat sink.
- Resistance elements R2, as well as R5, should be used at least 2 watts each.
- As for the transformer, it can be purchased at a store or taken from a soldering station (high-quality transformers can be found in old Soviet soldering irons). You can rewind the secondary wire to a new one with a cross section of about 1.8 mm per 14 volts. In principle, thinner wires can also be used, since this power will be sufficient.
- When all the elements are in your hands, the entire structure can be installed in one case. For example, for this you can take an old oscilloscope. In this case, we will not make any recommendations, since the body is a personal matter for everyone.
- After the charger is ready, it is necessary to check its performance. If you have doubts about the build quality, then we would recommend diagnosing the device on an older battery, which in which case it would not be a pity to throw it away. But if you did everything correctly, in accordance with the scheme, then there should be no problems in terms of operation. Please note that the manufactured memory does not need to be configured, it should initially work correctly.
Thyristor auto-chargers are very popular among home-made car enthusiasts, in which power from a powerful transformer is supplied to the battery through a thyristor controlled by pulses from the generator that open it. In its simplest form, the diagram will look like this:
And there is nothing to smile about - it is really working and at one time it was successfully operated for quite a long time. A more complex version, with a separate pulse generator and control of charge modes (battery voltage) is shown in the following circuit diagram:
But if experience allows, it is better to assemble a third automatic thyristor charger, which, in addition to being assembled by many people, has quite good parameters and capabilities.
Schematic and printed circuit board memory on SCR
The printed circuit board is drawn by hand with a marker. You can do the wiring yourself, for example, based on this picture:
Charger options
- Output voltage 1 - 15 V
- Limit current up to 8 A
- Battery overcharge protection.
- Protection against accidental short circuit output
- Polarity reversal protection
Functional description of the circuit
Alternating voltage from the secondary winding of the transformer (about 17 V) is supplied to the controlled thyristor-diode bridge, then, depending on the control pulses following from the controller, it is supplied to the battery terminals.
The controller consists of a separate mains transformer, its voltage is formed by the LM7812 stabilizer, the CD4538 double multivibrator makes control pulses on thyristors, and has battery voltage control circuits consisting of a CNY17 optocoupler and a TL431 voltage reference source operating as a comparator.
If the voltage at the TL431 (R) output is below 2.5 V (divider system with PR2 with resistors), no current flows through TL431 through LED2 and CNY17 due to blocking of the BC238 transistor, which leads to a high state at the reset pin 13 of the chip CD4538 and its normal operation (if control pulses are sent to the gates of the thyristor), if the voltage increases (as a result of battery charging), then TL431 starts to act, the current stops flowing through LED2 and CNY17, BC238 is triggered and the low state is applied to pin 13, generation control pulses on the gate of the thyristor stops, and the voltage on the battery is turned off. The cut-off voltage is set by PR4 at 14.4V. LED1 during charging becomes more and more frequent and almost at the final stage.
We also used 2 temperature sensors 80 C. One is glued to the radiator, and the other is glued to the secondary winding of the mains transformer, the sensors are connected in series. Activation of the sensor leads to a voltage cutoff on the optocoupler and blocking of the CD4538 multivibrator and the absence of thyristor gate control signals.
The fan is permanently connected to the battery.
The circuit has the AUT / MAN switch in the MAN position, with the automatic battery voltage control system disabled and the battery can be manually charged by controlling the voltage.
Here are several options for connecting rectifiers and thyristors:
- The scheme in fig. A. The least favorable turn-on, high voltage drop and strong heating of the bridge plus losses on the thyristor. Advantages: A single heatsink can be used because the rectifier bridges are usually insulated from the chassis.
- The scheme in fig. B most profitable, losses only on thyristors. But two radiators.
- The scheme in fig. WITH moderately beneficial. Three or one heatsink (with one heatsink, one double Schottky diode or two cathode diodes on the package.
These are the normal voltages at the pins of the CD4538 chip:
1 - 0 V
2 - from 11.5 V to 6 V when turning the potentiometer P
3.16 - 12 V
4,6,11 - 2V to 12V when turning P
5 - approximately 10 V
10.12 - about 0.1 V
13 - about 11.5 V with LED1 off
14 - about 12 V
15 — 0
The BD135 collector has about 19.9 V. For more detailed settings, you will need an oscilloscope. The circuit is quite simple and, if assembled correctly, should start immediately after applying voltage.
Photo of the charging process
The diode-thyristor bridge is located on separate boards and can conduct current up to 20 A, the radiators are isolated from each other and the case. The secondary winding of the transformer is wound with a wire with a diameter of about 2 mm, and with forced cooling it can give about 8 A for a long time (enough for most needs of motorists, charging batteries up to 82 A / h). But nothing prevents you from installing a transformer with even more power.
Separate test leads are used here, which are connected to the current terminals.
Battery charging: the charging current is 1/10 of the battery capacity, after a while, depending on the degree of discharge, LED1 starts flashing and soon approaches a voltage of 14.4 V. Most often, the charging current also drops, at the end of charging, the diode shines almost all the time. A small hysteresis is introduced by an electrolytic capacitor on the R-terminal of the TL431.
The cost of assembling a home-made memory device is determined by the main transformer (160 W, 24 V) of about 1000 rubles, as well as powerful diodes and thyristors. Usually there is enough of this stuff in amateur radio bins (as well as ready-made cases from something), so ideally it will not cost a penny.
