Preregulated-high-voltage-supply

  
One of the control circuit`s triacs selects the tap on main transformer Tl, which provides the proper, preregulated voltage to the secondary regulator. T2 and its associated components comprise the secondary regulator. The ADC 0804, IC1, digitizes a voltage-feedback signal from the secondary regulator`s output. The MC1415 demultiplexer, IC2, decodes the digitizer`s output. IC2, in turn, drives Tl`s optoisolated triacs via the 74LS240 driver chip, IC3, and associated optoisolators.
Preregulated-high-voltage-supply - schematic

Transformer T3 samples the circuit"s current output. The auxiliary, 12 V winding on Tl ensures noload starting. The combination of op amp IC5 and the inverting transistor, Ql, square this current signal. The output of Ql is the CLK signal, which triggers one-half of the one shot, IC4A, to begin the circuit"s AID conversion. The one shots" periods are set to time out within 1l2 cycle of the ac input. Upon completion of its AID conversion, ICl"s INTR output triggers the other half of the one shot, IC4B, which enables the converter"s data outputs. The rising edge of the CLK signal resets the one shot and latches the new conversion value into IC2. The latch, associated driver, and optoisolator trigger a selected triac according to the latest value of the voltage-feedback signal, V,.




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