Adjustable regulated power supply circuit with overload and short circuit protection - News - Global IC Trade Starts Here.

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Adjustable regulated power supply circuit with overload and short circuit protection

The circuit is simple, the voltage regulation accuracy is high, and the output voltage is constant after the rated load.
2 With overload and output short circuit protection and alarm function. When the overload occurs, the voltage drop across the resistor R8 increases. When the voltage drop reaches 0 6V, the thyristor SCR turns on, causing the base potential of Q1 to drop to about 1V, so the tube Q1 and the adjusting tubes Q2 and Q3 are both cut off, and the protection is adjusted. The tube is protected from burnout. After Q2 and Q3 are turned off, the output voltage is zero, the electronic switch Q4 is turned off, and Q5 is turned on, so that the multi-vibrator composed of Q6 and Q7 starts to vibrate (tens of Hz), and the LED 2 of the light-emitting tube flashes to show an alarm. When the output is short-circuited (maximum overload), the voltage drop across R8 is much greater than 0 6V, and the thyristor turns on immediately, also cutting off the regulated output. When the short-circuit fault is removed, just press the reset button AN to “reset” the thyristor, and the regulated power supply will work as usual. At this time, Q4 is normally turned on, Q5 is turned off, Q6 and Q7 are stopped, and LED2 is turned off.

The power supply is easy to manufacture, and the β values ​​of Q2 and Q3 should be close to each other. Resistors R2, R4, R5, R6, R14, and R17 are 1/2W, and the rest are 1/4W. The resistor R8 is formed by connecting 6 copper wires of diameter 25 mm and length 18 cm in parallel. If there is no copper wire, it can also be made by connecting 8 1/4 W2 2Ω color ring resistors in parallel. This resistor has only an effect on the protection current setting and is independent of the regulation accuracy. The adjusting tube radiator is made of a commercially available aluminum alloy special radiator and is mounted outside the iron shell.