BENCH_TOP_POWER_SUPPLY

Published:2009/7/2 3:38:00 Author:May | From:SeekIC

Circuit Notes A tapped transformer drives a diode bridge (D1-D4) and two 2500 pF filter capacitors (C1 and C2), that provide a noload voltage of 37 or 47 volts, depending upon the position of switch 52a. The unregulated dc is then fed to a pre-regulator stage composed of Q1 and D5. Those components protect IC1（the 723）from an over-voltage condition; the 723 can't handle more than 40 volts. The LED (LEDl) and its 2.2 k current-limiting resistor（R1）provide on/off indication. The current through the LED varies slightly according to the transformer tap selected, but that's of no real consequence. The series-pass transistor in IC1 drives voltage-follower Q2, providing current amplification. The transistor can handle lots of power. It has a maximum collector current of 15 amps and a maximum VCE of 70V, both of which are more than adequate for our supply.



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