Power supply for TVK-110 LM, 5-25 volts. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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The power supply (Figure 2-8) provides a bipolar output voltage that can be changed from 5 to 25 V. The maximum load current can reach 1 A. If this current is exceeded or there is a short circuit, the output protection device is triggered and the output voltage drops sharply simultaneously on both channels . Transformers T1 and T2 are included as step-down, each of them "works" on both channels. Rectifiers are made on diodes VD1 ... VD4, the rectified voltage is smoothed out by capacitors C1 and C2 of relatively large capacity.
On transistors VT1, VT2, VT10, a voltage regulator of a positive polarity channel is assembled according to a compensation circuit, and on a transistor VT9 and a zener diode VD5 - a reference voltage source for this stabilizer. The output voltage of the stabilizer is regulated by a variable resistor R5.
Transistor VT7 and resistor R3 make up the current protection node. When the load current exceeds the set value, the transistor opens and the voltage regulator enters the current stabilization mode. In the negative polarity channel, the voltage stabilizer is assembled on transistors VT4 ... VT6, and the current protection unit is assembled on transistor VT8 and resistor R4.
(click to enlarge)
The printed circuit board is shown in fig. 2.9.
The exemplary voltage for this stabilizer is the output voltage of the positive polarity channel stabilizer, which is fed through the resistor R7 to the base of the transistor VT4. Therefore, when the variable resistor R5 changes the voltage of positive polarity, the output voltage of negative polarity will also change. In order for this change to occur synchronously and both output voltages to be as equal as possible, resistors R7 and R8 are selected with the same resistances, and back-to-back diodes VD6 and VD7 are introduced into the zener diode circuit.
With a normally operating power supply, the voltage taken from the common connection point of the resistors relative to the common wire is zero and the transistor VT3, to the base of which this voltage is supplied, is closed. In addition to the specified unified transformers, ready-made transformers TS-31-1 can also be used in the unit, or one transformer with a power of at least 60 W with two secondary windings with a voltage of 27 ... 30 V each at a load current of up to 1 A.
Transistor VT1 can be KT815A ... KT815G, KT603A ... KT603G, KT608A, KT608B; VT2 - KT819A, KT819P KT805A, KT805B, KT808A; VT3, VT7, VTI0 - KT3102A...KT3102V, KT342V, KT312V, KT315V...KT315E; VT4, VT8 - KTZ 107A ... KTZ 107K, KT361V ... KT361E; VT5 - KT814A...KT814G, KT816A...KT816G; VT6 - KT818A...KT818G; VT9 - KP303D, KP303E, KP302A, KP302B, KP307A, KP307B. Diodes VD1 ... VD4 - D242, D242B, D245, KD202A ... KD202K or similar powerful ones; VD6, VD7 - KD105B, KD105G, KD103A, KD103B, as well as other silicon rectifier diodes. Zener diode VD5 - KS133A, KS139A, KS147A.
Powerful diodes VD1 ... VD4 can be used without radiators, but transistors VT2 and VT6 must be installed on radiators with a total surface area of at least 200 cm2. When checking the operation of the unit, if it is necessary to change the adjustment range of the output voltage, resistor R6 should be selected. The value of the protection operation current can be set by selecting resistors R3 and R4.
Author: Semyan A.P.
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