Regulated power supply with current protection. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Regulated power supply with current protection. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Power Supplies

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They gave you a car tape recorder for repair. And you have nothing to ask him. You need a stabilized power supply with good low and high frequency filtering. If you have a factory stabilizer, then where is the guarantee of the integrity of the output stages of the amplifier. When these cascades are closed, the tape recorder consumes a current of 3 A or more, which leads to the failure of the stabilizer.

Figure 1 shows a stabilizer circuit, from which you can power not only a car tape recorder, but also any amateur radio design with a voltage of 1 to 35 V and which is not afraid of high load currents, since current protection has been introduced.

(click to enlarge)

The voltage regulator is assembled on a DA1 chip, which is supplemented with a powerful transistor that can deliver a current of up to 5 A to the load. With a resistor R5 = 0,3 Ohm, the maximum load current is 2,8 A.

With a further increase in current to 2,9-3 A, the protection made on the VD6 optocoupler is triggered. When the voltage at R5 becomes large, the LED inside the VD6 optocoupler lights up.

The dinistor thyristor opens and passes a negative voltage to pin 8 of the DA1 microcircuit, which leads to a voltage drop at the output of the stabilizer to 1 V. You can return the voltage at the output of the stabilizer by pressing the SA2 button. Adjust the output voltage with resistor R4.

For smoothing at low and high frequencies, the inductor Dr1 and capacitors C2, C3 are used. The use of an optocoupler increases the reliability and speed of protection.

Construction and details. The following parts are used in the power supply. Any transformer T1 with an output voltage of 35 V and a current of at least 3,5 A, any capacitor C1 with a rated voltage of 250 V, instead of C4, you can use imported 1000 uF x 50 V. Resistors R1-R3 of the MLT type with a power of 0,25 W. Chip DA1 type K142EN12, its complete analogue is a foreign-made chip LM317T. Transistor VT1 type KT803A, KT805G, KT808, optocoupler VD6 type AOU103V.

The printed circuit board is shown in Figure 2.

Regulated power supply with current protection

Author: A.S. Kovalchuk

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