Charger from the TV switching power supply. Let's make a charger from a computer power supply. The proposed design provides automatic cut-off of the current supplied to the battery when a full charge is reached.

When using acidic batteries in a vehicle or systems uninterruptible power supply, they need to be charged, preferably in automatic mode. Of course, charging must be provided by the device manufacturer. Fully provide the necessary modes for long-term operation and good condition of the battery installed in it. However, there are situations when there is a need for additional battery charging and maintenance:
1. Such situations arise in the cold season, when the car is in the garage for a long time and the battery loses its charge. It happens that the driver does not turn off the consumers and the car will not start the next day.
2. In uninterruptible power systems, the situation is much better. The device constantly monitors the battery charge, charges it correctly and does not allow it to discharge more than necessary. Until an inquisitive mind gets into it, to improve the characteristics.
My business went according to the second scenario.

Once, in the winter, the situation with the energy supply deteriorated sharply. It soon became clear that this was for a long time, and I took out an uninterruptible power supply. It contained a 7 Ah battery, which was barely enough for a ten-watt LED lighting. The lights were turned off for 2-4 hours, sometimes there was no electricity for 6 hours. Several times they turned on the electricity for two hours during the day, but he did not have time to charge. Yes, and I wanted to watch TV, because the 220 V output was idle.
Later I bought a 75 Ah battery used and took care of charging it. It was necessary to charge it quickly and unattended by people. Moreover, the charger should be cheap and good.
The transformer canceled immediately because mains voltage varied over a wide range, sometimes dropping to 140 V. I had an inexpensive pulse Chinese block power supply 12 V., 60 W, called "S 60-12". However, it will not be difficult to purchase one in an online store or at a local lighting store.
The block has excellent basic characteristics:

After connecting to the battery, troubles began to arise:
1.voltage 13.2V is not enough to charge
2.Very high current when the battery voltage is low
3.discharge of the battery into the power supply

Consider the output circuits of our block, and determine what can be done to solve the problems:
1. You can increase the output voltage by shunting the resistor from the TL431 control pin to the common wire (R15, SVR1)
2. The current can be reduced by installing a high current limiting resistor at the output, or by decreasing the output voltage.
3. Battery discharge is eliminated by a series diode.

I had a weak 7 Ah battery, for it the discharge into the power supply (~ 50 mA) was significant, and I installed a bunch of diodes in series with the UPS output. Later, I gave up the diodes when I switched to a large battery.
First you need to increase the output voltage by installing a 12 kΩ resistor in parallel with R15 (see the first figure). After that, the maximum voltage at the output of the UPS will become 16 V., excluding the drop on the diodes. The current limiting resistor was made of thick nichrome wire. In the absence of such, you can buy a ready-made resistor. The voltage should be set at the output terminals after the diode loaded on the lighting lamp to take into account the drop on the diode assembly. The table shows the nominal resistance (R) and the maximum power dissipation (Pmax) of the resistor, for a charge voltage of 13.8 V. (Umax), a minimum voltage on the battery 11 V. (Umin) and a maximum charge current of 20% of the capacity (s) ... This safe mode, since the current will fall linearly as it charges. You can independently calculate the resistance of the resistor:

R = (Umax-Umin) /0.2*c,

and the maximum power on it:

Pmax = (Umax-Umin) 2 / R

In general, the system turned out to be reliable, requiring no maintenance, but also with drawbacks. Of course, a resistor that shamelessly heats up at high currents. Long charging time and inability to fully charge.
After purchasing a 75 A / H battery and operating it in constant TV viewing mode (plus a 2 * 5W sound amplifier, T2 tuner, modem with a router, charging a phone / tablet, lighting), the resistive circuit no longer had time to recover the wasted charge.

A switching power supply (UPS) stabilizes the output voltage using a controlled SHR1 TL431 zener diode, part of the output circuits is shown in the first figure. The opening of this zener diode occurs when the voltage at the control output exceeds 2.5V. We can say that in normal mode, the voltage at this point is always 2.5 V. Our circuit will act on this pin to change the output voltage. Please note that the output voltage range of this UPS is limited. It is not advisable to increase the output voltage more than 16 V., and when it drops to less than 10 V. it turns off and tries to start. It means that a battery discharged less than 10 V. This charger will not be able to charge. Just as this memory cannot be used as a laboratory power supply unit, due to the impossibility of adjusting the output voltage over a wide range and stabilizing the current during a short circuit.

The current stabilization circuit was hastily assembled and the diode was excluded. The design and diagram are presented below:

The presented scheme has several disadvantages.
1. Inability to quickly adjust the current
2. Poor current stabilization accuracy, depending on its level and output voltage
3. Absence of indication of the end of the process, for fast charging of car batteries

The circuit worked for 4 months without malfunctions. The only maintenance is constantly rotting wires on the battery terminals (not connected securely)

Now that the need for battery power has disappeared and free time, I decided to improve the device. Current regulation was introduced with an external variable resistor. Added a bug booster to improve accuracy. Introduced LED indication of the operating mode.

ATTENTION - soldering the resistor that increases the output voltage of the UPS, in this version of the control circuit is not required. Its function is performed by R10

As a result, the schematic diagram became slightly more complex. The second op-amp, IC1B, operates in an error integrator / amplifier mode, comparing the IC1A output current, which is proportional to the output current, with the reference voltage at RES.2 set by the regulator. At its output (pin. 7 IC1B), the voltage can be in two states. Near zero when the current cannot reach the value set by the resistor. And, about 3.5 V., when the output current is captured and stabilized, that is, there is a charge. The "Charge" LED connected to the LED point indicates the state of the device. The VR1 TL431 parallel zener regulator provides a reference voltage for the current regulator resistor. At its cathode, the voltage should be 2.5 V. Two resistors R7, R8 instead of one are installed to reduce the power dissipated across them.
The shunt resistance (Rsh), together with the IC1A gain (k) and the voltage at RES.1 (Vref), determine the maximum charging current (Imax) of the regulator:

Imax = Vref / (k * Rsh).

Where is the gain of the differential amplifier:

k = R5 / R1, with R1 = R2, R5 = R3.

In our case:

Rsh = 0.1 Ohm / 3 = 0.0333 Ohm,
k = 1500 Ohm / 100 Ohm = 15,
Imax = 2.5 V / (15 * 0.0333 Ohm) = 5 A.

After checking the correct installation of the control board, you need to correctly connect it to the UPS. I tried to depict clearly so that there would be no connection problems. The control wire should be connected to the disassembled unit, having previously disconnected it from the 220 V network. !! Before switching on, it is necessary to install the PSU casing in its regular place and adjust the resistor R10 to the maximum high resistance. We include. we adjust the output voltage of the UPS, for operation as part of an uninterruptible power supply, with open contacts of the "Mode" button, with the SVR1 resistor (see the first figure) at the level of 13-13.8 V. When you press the "Mode" button, set the output voltage 14 , 4 V. resistor R10, for one-time battery charging. We check the voltage at the extreme terminals of the adjustment resistor, it should be 2.5 V. Having connected a working battery, we will check the adjustment of the output current. The maximum current must not exceed 5 A. for this UPS. If the current is not sufficient, you need to change the amplifier gain to IC1A. However, after this amplifier, you can put a trimmer resistor on the common wire and connect the engine of this resistor to 5 pins. IC1. to adjust the maximum. The minimum will be about zero amperes and does not need adjustment. A power resistor or coil from an electric stove can be used to check the output current, but the current will only stabilize over a small voltage range from about 10 V. to 13 or 14.4 V., depending on the switch settings.

Charger has features:
- When charging up to 14.4 V., it is necessary to observe the state of the "Charge" LED. At the end of the charge, it will go out, and you should disconnect the charger from the battery.
- In the event of a battery malfunction and the voltage on it is less than 10 V., the LED will flash and there will be no charge.
- If the output terminals are short-circuited, there will be no LED indication, but the UPS will activate the internal protection.
- This charger has no protection against polarity reversal of the battery terminals and it is advisable to install a 5 A fuse at the output.

The design of the control unit is made on a prototype printed circuit board with output components. The scheme uses widespread elements. Instead of a zener diode VR1, you can use an ordinary zener diode for a voltage of 3.3-5.1 V. (Vref), changing the coefficient. gain diff. amplifier according to the above formula. Ultra-bright red LED in a transparent case, such at low current shine well. Variable resistor of any convenient type of regulator with a nominal value of 1-10 kOhm.
As a current shunt, I used 0.1 ohm 1 W resistors, they are quite common and not in short supply. The connection to the shunt was made as shown in the figure and photograph. You can use a ready-made shunt or low resistance resistors of 0.03-0.01 Ohm with a power of 3 or more watts, for example, MPR-5W, BPR56. In extreme cases, you can use a coil of low-section copper wire, but the parameters will change with warming up.

List of radioelements

Not bad Charger with good output characteristics can be made from old TVs with pulsed power supplies such as MP1, MP3-3, MP403, etc. A slight modification of the unit allows you to use it for charging Battery with a current of up to 6-7A, repair of car radios and other equipment.

Battery charger from MP3-3

The whole point of block rework consists in increasing the load capacity of TPI and rectifier diodes, for this we connect the windings with terminals 12.18 and 10.20 in parallel, terminal 20 is connected to the common terminal of secondary sources (12), and terminal 10 is to terminal 18, rectifier diodes 12V and 15V we turn off and connect a diode for a current of 10-25A to terminals 10, 18, which must be installed on the heat sink, for these purposes I used a drain from a standard 12 V stabilizer.

The details of which are as unnecessary you can remove it from the board (except for the drain), you can put a new diode on it, connect a 470pf condenser in parallel to it and an electrolyte at 470 uF x 40V at the output, in parallel we put a load resistor MLT 2 with a nominal value of 510-680 ohm and a ceramic capacitor on 1 microfarad, these parts are installed to exclude the appearance of high-frequency voltage at the output of the power supply unit.

To adjust the output voltage you can use a trimmer resistor R2 according to the scheme, which is evaporated and instead of it we connect an external variable wire-wound resistor of the PPZ type 1-1.5 kΩ, adjusting the output voltage from 13V to 18V.

To bring the block to the mode stabilization, it must be loaded, for this you can use a lamp from the refrigerator by connecting it to terminals 6 and 18.

In its block for loading I used the +28 V output, connecting a 28 V 5 W lamp to it, which simultaneously serves as the illumination of the voltmeter scale with an extended scale from the "five". The unit heats up under load as in normal mode, but it will be better if you make forced airflow by placing the cooler from the computer.
When connecting the battery, it is necessary to observe the polarity and put a 10A fuse at the output.

Sometimes it happens that the battery in the car sits down and it is no longer possible to start it, since the starter does not have enough voltage and, accordingly, current to turn the engine shaft. In this case, you can “light up” from another car owner so that the engine starts up and the battery starts charging from the generator, but this requires special wires and a person who wants to help you. You can also charge the battery yourself using a specialized charger, but they are quite expensive and do not have to be used very often. Therefore, in this article we will take a closer look at a homemade device, as well as instructions on how to make a do-it-yourself car battery charger.

Homemade device

The normal voltage for a battery disconnected from the vehicle is between 12.5 volts and 15 volts. Therefore, the charger must supply the same voltage. The charge current should be equal to about 0.1 of the capacity, it can be less, but this will increase the charging time. For a standard battery with a capacity of 70-80 a / h, the current should be 5-10 amperes, depending on the specific battery. Our homemade battery charger must meet these parameters. To assemble a car battery charger, we need the following items:

Transformer. US any will do from an old electrical appliance or bought on the market with an overall power of about 150 watts, more is possible, but not less, otherwise it will get very hot and may fail. It's great if the voltage of its output windings is 12.5-15 V, and the current is about 5-10 amperes. You can view these parameters in the documentation for your part. If the required secondary winding is not available, then it will be necessary to rewind the transformer for a different output voltage. For this:

Thus, we have found or assembled the perfect transformer to make a do-it-yourself battery charger.

We will also need:

Having prepared all the materials, you can proceed to the very process of assembling the car charger.

Assembly technology

To make a do-it-yourself car battery charger, you must follow the step-by-step instructions:

1. We create a homemade charging circuit for the battery. In our case, it will look like this:
   
2. We use the TS-180-2 transformer. It has multiple primary and secondary windings. To work with it, you need to connect in series two primary and two secondary windings in order to obtain the desired voltage and current at the output.
   
   
3. Using a copper wire, we connect pins 9 and 9 'together.
   
4. On a fiberglass plate, we assemble a diode bridge from diodes and radiators (as shown in the photo).
   
5. Conclusions 10 and 10 'are connected to the diode bridge.
6. Install a jumper between pins 1 and 1 '.
   
7. We attach the power cord with a plug to pins 2 and 2 'using a soldering iron.
8. We connect a 0.5 A fuse to the primary circuit, and a 10-amp fuse, respectively, to the secondary.
9. In the gap between the diode bridge and the battery, we connect an ammeter and a piece of nichrome wire. One end of which is fixed, and the other must provide a movable contact, thus the resistance will change and the current supplied to the battery will be limited.
10. We insulate all connections with heat shrink or electrical tape and place the device in the case. This is necessary to avoid electric shock.
11. We install a movable contact at the end of the wire so that its length and, accordingly, the resistance is maximum. And we connect the battery. By decreasing and increasing the length of the wire, it is necessary to set the desired current value for your battery (0.1 of its capacity).
12. During the charging process, the current supplied to the battery will itself decrease and when it reaches 1 ampere, we can say that the battery is charged. It is also advisable to control directly the voltage on the battery, however, for this it must be disconnected from the charger, since during charging it will be slightly higher than the actual values.

The first start-up of the assembled circuit of any power source or charger is always carried out through an incandescent lamp, if it lights up at full incandescence - either there is an error somewhere, or the primary winding is closed! The incandescent lamp is installed in the gap of the phase or neutral wire supplying the primary winding.

This circuit of a homemade battery charger has one big drawback - it does not know how to independently disconnect the battery from charging after reaching the desired voltage. Therefore, you will have to constantly monitor the readings of the voltmeter and ammeter. There is a design that is devoid of this drawback, but its assembly will require additional parts and more effort.

An illustrative example of a finished product

Operating rules

The disadvantage of a homemade charger for a 12V battery is that after fully charging the battery automatic shutdown the device does not occur. That is why you will have to periodically glance at the scoreboard in order to turn it off in time. Another important nuance - it is strictly forbidden to check the memory "for a spark".

The article discusses several options for assembling a power supply and charger with your own hands.

Power supply + 12V charger from scrap materials

The simplest power supply unit should simply convert an alternating current of 220V into a direct voltage of 12V. The first task (lowering the voltage) is performed using a step-down transformer of any origin, the second (replacing alternating current with direct current) using a diode bridge and a capacitor.

Accordingly, the schematic diagram of the simplest power supply is as follows:

Let's deal with the necessary details in order. Any step-down transformer with sufficient capacity can be used as a transformer. The latter depends on the tasks that you entrust to the planned power supply; 10-20 W is enough to charge car batteries. Since a partial voltage loss is almost inevitable, in order to ensure stable operation of the device, the secondary winding must provide a voltage of 14-20 volts (optimally 16-18V).

The easiest way to find a suitable transformer is at a radio parts store or at the nearest radio flea market. You can and well look in the attic - this type of converters are used in audio recorders, game consoles, office computer equipment. If there is a transformer with an inappropriate voltage (for example 24V), you can change the parameters of the secondary winding or use resistors.

The simplest diode bridge is assembled from four identical diodes, which, as a result, will perform the functions of a full-wave rectifier.

A capacitor is necessary to avoid failures and, we can safely say one thing, than more capacity, all the better. You can use a 16-volt 1000 uF or more.

The assembly order is as follows:

- we collect the diode bridge;

- we connect a transformer to it;

- we connect the capacitor to the free outputs of the diode bridge, observing the polarity;

- we remove the power connector from the capacitor.

You can pack it all in a beautiful box and tie it up with a beautiful ribbon.

The proposed scheme is primitive and has many disadvantages, therefore there are many more complex options, for example, with the ability to adjust the output voltage and current, using a variety of protective systems (against overheating, against voltage drops, current), volt-ammeters and others.

We will consider these schemes in more detail using specific examples of building a battery charger.

Example 1 Assembling a charger based on a power supply from a Kenon printer.

For this we need:

- the actual power supply;

- volt-ammeter;

- variable resistors (3 pcs);

- cooler of any origin;

- power button;

- voltage regulators on the microcircuit (LM 2596 or analog);

- output connectors;

- bolts, nuts and other fasteners.

The printer's power supply is well suited because it has sufficient power and reliability, and, importantly, has a built-in voltage regulation board. Therefore, if you need a power supply of a strictly specified voltage, you just need to find the required microcircuit (in this case, TL431) and select the right resistor to replace the original one.

We will try to assemble a unit with the ability to change the operating voltage in the range of 0-30V, the schematic diagram of which is in the figure:

Procedure:

Since the ceiling of the required operating voltage is higher than the inherent voltage of the printer unit, you need to "raise the bar". To do this, replace the resistor on the above-mentioned board.

We take the case of the future charger and make holes in the front part for three resistors, a volt-ammeter and a power button

We mount all of the above on the panel

Similarly, we make holes in back cover for a cooler, output connectors and a power plug (transferred from the case of the printer unit)

We mount the back panel

We mount the insides - the main power supply board of the printer, voltage regulators

Putting together an electrical circuit. We connect one converter to a cooler and a voltmeter, it must be adjusted to 12V. The second makes it possible to adjust the current strength. We connect two resistors (10 and 1 kOhm, respectively) in series, as a result we get the ability to accurately adjust the voltage, the third limits the current in the range from 0 to 3A.

We assemble the case, produce trial run, we use.

Example 2. Assembling a thyristor charger

This type of charging is based on a network transformer with a tailored output voltage (18-20V) and a thyristor-based current pulse generator. In this case, the driving pulses are formed by transistors, and the thyristor only passes the generated pulse to the storage battery.

Schematic diagram on the image

Diodes are best used for 10 amperes, a capacitor of at least 1000 microfarads at 40V. Using capacitors of lower voltage and capacity is risky as it can lead to unstable and short-lived service. The cooler is extremely important, since charging the battery takes a lot of time and the transformer can get hot, so it is better to use a fan of good performance (from an old computer, laptop, electric welding) and place it in the front (will provide maximum airflow to the inside of the case). The housing can be selected or made from sheet metal / plastic.

Example 3 Another charger for especially sophisticated radio amateurs.

The proposed design provides automatic cut-off of the current supplied to the battery when a full charge is reached.

Schematic diagram in the figure:

Features of such a device:

- despite its simplicity, it requires the use of a special printed circuit board;

- the thyristor is used not only as a switch, but also as a rectifier;

The material in this article is intended not only for owners of already rare TVs who want to restore their performance, but also for those who want to understand the circuitry, device and principle of operation of switching power supplies. If you assimilate the material of this article, then you can easily figure out any circuit and principle of operation of switching power supplies for household appliances, be it a TV, laptop or office equipment. And so let's get started ...

In Soviet-made TVs, the third generation ZUSTST, impulse power supplies - MP (power module) were used.

Switching power supplies, depending on the TV model where they were used, were divided into three modifications - MP-1, MP-2 and MP-3-3. Power modules are assembled according to the same electrical diagram and differ only in the type of pulse transformer and in the voltage rating of the capacitor C27 at the output of the rectifier filter (see schematic diagram).

Functional diagram and principle of operation of the switching power supply unit of the TV ZUSTST

Rice. 1. Functional diagram of the switching power supply unit of the TV ZUSTST:

1 - mains rectifier; 2 - trigger pulse shaper; 3 - pulse generator transistor, 4 - control stage; 5 - stabilization device; 6 - protection device; 7 - pulse transformer of the power supply unit for TVs 3USCT; 8 - rectifier; 9 - load

Let at the initial moment of time in the device 2 a pulse will be formed, which will open the transistor of the pulse generator 3. In this case, a linearly increasing sawtooth current will begin to flow through the winding of the pulse transformer with terminals 19, 1. At the same time, energy will accumulate in the magnetic field of the transformer core, the value of which is determined by the on-state time of the transistor of the pulse generator. The secondary winding (terminals 6, 12) of the pulse transformer is wound and connected in such a way that during the period of accumulation of magnetic energy, a negative potential is applied to the anode of the diode VD and it is closed. After some time, control stage 4 closes the transistor of the pulse generator. Since the current in the winding of the transformer 7 cannot instantly change due to the accumulated magnetic energy, an EMF of self-induction of the opposite sign occurs. The VD diode opens, and the secondary winding current (terminals 6, 12) rises sharply. Thus, if in the initial period of time the magnetic field was associated with the current that flowed through the winding 1, 19, then now it is created by the current of the winding 6, 12. When all the energy accumulated during the closed state of the key 3 goes into the load, then in the secondary winding will reach zero.

From the given example, we can conclude that by adjusting the duration of the on-state of the transistor in the pulse generator, it is possible to control the amount of energy that is supplied to the load. Such adjustment is carried out using a control cascade 4 according to a feedback signal - the voltage at the terminals of the winding 7, 13 of the pulse transformer. The feedback signal at the terminals of this winding is proportional to the voltage across the load 9.

If the voltage across the load for some reason decreases, then the voltage that goes to the stabilization device will also decrease. In turn, the stabilization device through the control cascade will start to close the transistor of the pulse generator later. This will increase the time during which current will flow through the winding 1, 19, and, accordingly, the amount of energy transferred to the load will increase.

The moment of the next opening of the transistor 3 is determined by the stabilization device, where the signal coming from the winding 13, 7 is analyzed, which makes it possible to automatically maintain the average value of the output constant voltage.

The use of a pulse transformer makes it possible to obtain voltages of different amplitude in the windings and eliminates the galvanic connection between the circuits of secondary rectified voltages and the power supply network. Control stage 4 determines the amplitude of the pulses generated by the generator and, if necessary, turns it off. The generator is turned off when the mains voltage drops below 150 V and the power consumption drops to 20 W, when the stabilization stage ceases to function. When the stabilization stage is not working, the pulse generator turns out to be uncontrollable, which can lead to the appearance of large current pulses in it and to the failure of the pulse generator transistor.

Schematic diagram of the switching power supply unit of the TV ZUSTST

Let's consider the schematic diagram of the MP-3-3 power supply module and the principle of its operation.

Rice. 2 Schematic diagram of the switching power supply unit of the TV ZUSTST, module MP-3-3

It includes a low-voltage rectifier (diodes VD4 - VD7), a trigger pulse generator (VT3), a pulse generator (VT4), a stabilization device (VT1), a protection device (VT2), a pulse transformer T1 of a power supply unit 3USCT and rectifiers on diodes VD12 - VD15 with voltage regulator (VT5 - VT7).

The pulse generator is assembled according to the blocking generator scheme with collector-base connections on the VT4 transistor. When the TV is turned on, the constant voltage from the output of the low-voltage rectifier filter (capacitors C16, C19 and C20) through the winding 19, 1 of the transformer T1 enters the collector of the transistor VT4. At the same time, the mains voltage from the VD7 diode through the capacitors C11, C10 and the resistor R11 charges the capacitor C7, and also goes to the base of the transistor VT2, where it is used in the protection device of the power supply module from undervoltage. When the voltage across the capacitor C7, applied between the emitter and base 1 of the unijunction transistor VT3, reaches 3 V, the transistor VT3 will open. The capacitor C7 is discharged along the circuit: the emitter-base transition 1 of the transistor VT3, the emitter transition of the transistor VT4, connected in parallel, the resistors R14 and R16, the capacitor C7.

The discharge current of the capacitor C7 opens the transistor VT4 for a time of 10 - 15 μs, sufficient for the current in its collector circuit to increase to 3 ... 4 A. The flow of the collector current of the transistor VT4 through the magnetizing winding 19, 1 is accompanied by the accumulation of energy in the magnetic field of the core. After the end of the discharge of the capacitor C7, the transistor VT4 closes. The termination of the collector current causes the appearance of an EMF of self-induction in the coils of the transformer T1, which creates positive voltages at the terminals 6, 8, 10, 5 and 7 of the transformer T1. In this case, a current flows through the diodes of one-half-period rectifiers in the secondary circuits (VD12 - VD15).

With a positive voltage at terminals 5, 7 of the transformer T1, capacitors C14 and C6 are charged, respectively, in the anode and control electrode circuits of the thyristor VS1 and C2 in the emitter-base circuit of the transistor VT1.

Capacitor C6 is charged along the circuit: terminal 5 of transformer T1, diode VD11, resistor R19, capacitor C6, diode VD9, terminal 3 of the transformer. Capacitor C14 is charged along the circuit: terminal 5 of transformer T1, diode VD8, capacitor C14, terminal 3 of the transformer. Capacitor C2 is charged through the circuit: terminal 7 of transformer T1, resistor R13, diode VD2, capacitor C2, terminal 13 of the transformer.

Similarly, the subsequent switching on and off of the VT4 transistor of the blocking generator is carried out. Moreover, several such forced oscillations are sufficient to charge the capacitors in the secondary circuits. With the end of the charging of these capacitors between the windings of the blocking generator connected to the collector (conclusions 1, 19) and to the base (conclusions 3, 5) of the transistor VT4, a positive Feedback... In this case, the blocking generator goes into self-oscillation mode, in which the VT4 transistor will automatically open and close at a certain frequency.

During the open state of the transistor VT4, its collector current flows from the plus of the electrolytic capacitor C16 through the winding of the transformer T1 with terminals 19, 1, the collector and emitter junctions of the transistor VT4, resistors R14, R16 connected in parallel to the minus of the capacitor C16. Due to the presence of inductance in the circuit, the increase in the collector current occurs according to a sawtooth law.

To exclude the possibility of failure of the transistor VT4 from overload, the resistance of the resistors R14 and R16 is selected in such a way that when the collector current reaches 3.5 A, a voltage drop is created across them sufficient to open the thyristor VS1. When the thyristor is opened, the capacitor C14 is discharged through the emitter junction of the transistor VT4, the resistors R14 and R16 connected in parallel, the open thyristor VS1. The discharge current of the capacitor C14 is subtracted from the base current of the transistor VT4, which leads to its premature closing.

Further processes in the operation of the blocking generator are determined by the state of the thyristor VS1, the earlier or later opening of which makes it possible to regulate the rise time of the sawtooth current and thereby the amount of energy stored in the transformer core.

The power module can operate in stabilization and short-circuit mode.

The stabilization mode is determined by the operation of the DCA (DC amplifier) ​​assembled on the VT1 transistor and VS1 thyristor.

At a mains voltage of 220 Volts, when the output voltages of the secondary power supplies reach their nominal values, the voltage on the winding of the transformer T1 (terminals 7, 13) increases to a value at which the constant voltage at the base of the transistor VT1, where it enters through the divider Rl - R3, becomes more negative than at the emitter, where it is transferred completely. Transistor VT1 opens along the circuit: terminal 7 of the transformer, R13, VD2, VD1, emitter and collector junctions of transistor VT1, R6, thyristor control electrode VS1, R14, R16, terminal 13 of the transformer. This current, summed up with the initial current of the control electrode of the thyristor VS1, opens it at the moment when the output voltage of the module reaches its nominal values, stopping the rise of the collector current.

By changing the voltage at the base of the transistor VT1 with the trimming resistor R2, it is possible to regulate the voltage across the resistor R10 and, therefore, to change the moment of opening the thyristor VS1 and the duration of the open state of the transistor VT4, thereby setting the output voltage of the power supply.

With a decrease in the load (or an increase in the mains voltage), the voltage at terminals 7, 13 of the transformer T1 increases. In this case, the negative voltage at the base increases with respect to the emitter of the transistor VT1, causing an increase in the collector current and a drop in voltage across the resistor R10. This leads to an earlier opening of the thyristor VS1 and the closing of the transistor VT4. This reduces the power delivered to the load.

With a decrease in the mains voltage, the voltage on the winding of the transformer T1 and the potential of the base of the transistor VT1 in relation to the emitter become correspondingly less. Now, due to a decrease in the voltage created by the collector current of the transistor VT1 across the resistor R10, the thyristor VS1 opens at a later time and the amount of energy transferred to the secondary circuits increases. Important role in the protection of the transistor VT4, a cascade plays on the transistor VT2. When the mains voltage decreases below 150 V, the voltage on the winding of the transformer T1 with terminals 7, 13 turns out to be insufficient to open the transistor VT1. In this case, the stabilization and protection device does not work, the VT4 transistor becomes uncontrollable and the possibility of its failure is created due to exceeding the maximum acceptable values voltage, temperature, current of the transistor. To prevent the failure of the VT4 transistor, it is necessary to block the blocking generator. The transistor VT2 intended for this purpose is turned on in such a way that a constant voltage is supplied to its base from the divider R18, R4, and a pulsating voltage with a frequency of 50 Hz is applied to the emitter, the amplitude of which is stabilized by the Zener diode VD3. When the mains voltage decreases, the voltage at the base of the transistor VT2 decreases. Since the voltage at the emitter is stabilized, a decrease in the voltage at the base leads to the opening of the transistor. Through an open transistor VT2, trapezoidal pulses from the VD7 diode are fed to the control electrode of the thyristor, opening it for a time determined by the duration of the trapezoidal pulse. This leads to the termination of the blocking generator.

Short circuit mode occurs when there is a short circuit in the load of the secondary power supplies. In this case, the power supply is started by triggering pulses from the starting device assembled on the VT3 transistor, and the shutdown is performed using the VS1 thyristor according to the maximum collector current of the VT4 transistor. After the end of the trigger pulse, the device is not energized, since all the energy is consumed in the short-circuited circuit.

After removing the short circuit, the module enters the stabilization mode.

Rectifiers impulse voltages, connected to the secondary winding of the transformer T1, are assembled according to a half-wave circuit.

The VD12 diode rectifier creates a voltage of 130 V to power the circuit line scan... The ripple of this voltage is smoothed out by an electrolytic capacitor C27. Resistor R22 eliminates the possibility of a significant increase in voltage at the output of the rectifier when the load is disconnected.

A 28 V voltage rectifier is assembled on the VD13 diode, designed to power the vertical scan of the TV. Voltage filtering is provided by capacitor C28 and choke L2.

A 15 V voltage rectifier for powering an audio frequency amplifier is assembled on a VD15 diode and a SZO capacitor.

The 12 V voltage used in the chromaticity module (MC), radio channel module (MRK) and vertical scanning module (MC) is created by a rectifier on the VD14 diode and capacitor C29. At the output of this rectifier, a compensating voltage stabilizer collected on transistors is included. It includes a control transistor VT5, a current amplifier VT6 and a control transistor VT7. The voltage from the output of the stabilizer through the divider R26, R27 goes to the base of the transistor VT7. Variable resistor R27 is designed to set the output voltage. In the emitter circuit of the transistor VT7, the voltage at the output of the stabilizer is compared with the reference voltage at the Zener diode VD16. The voltage from the VT7 collector through an amplifier on the VT6 transistor is fed to the base of the VT5 transistor connected in series in the rectified current circuit. This leads to a change in its internal resistance, which, depending on whether the output voltage has increased or decreased, either increases or decreases. Capacitor C31 protects the stabilizer from excitation. Through the resistor R23, a voltage is supplied to the base of the transistor VT7, which is necessary to open it when it is turned on and recover from a short circuit. Choke L3 and capacitor C32 are an additional filter at the output of the stabilizer.

Capacitors C22 - C26, shunt rectifier diodes to reduce interference emitted by pulse rectifiers into the electrical network.

Power supply unit surge protector ZUSCT

The PFP power filter board is connected to the electrical network through connector X17 (A12), switch S1 in the TV control unit and mains fuses FU1 and FU2.

As mains fuses, fuses of the VPT-19 type are used, the characteristics of which make it possible to provide much more reliable protection of television receivers in the event of malfunctions than fuses of the PM type.

The purpose of the suppressor filter is.

The power filter board contains elements of the suppression filter (C1, C2, C3, choke L1) (see schematic diagram).

Resistor R3 is designed to limit the current of the rectifier diodes when the TV is turned on. The posistor R1 and the resistor R2 are elements of the kinescope mask demagnetization device.