Power Supply Regulators Unit 7 – DC to DC Converter
When transistor switch Q1 is turned off, energy from the inductor flows through CR1 (now
forward biased) into C1 and the load.
A typical dc to dc converter circuit uses a transistor switch to chop up the dc line voltage into
high frequency pulses. The pulses are rectified and filtered to provide a dc output voltage.
Due to the high frequency pulses (25 kHz or higher), the rectifier and filter components are
generally smaller in size than required in conventional linear power supplies.
On your circuit board, a 78S40 type of universal switching regulator subsystem, housed in a 16-
pin molded DIP package, is used for the dc to dc converter circuit block.
The 78S40 is a monolithic regulator subsystem consisting of the active building blocks required
for a dc to dc converter circuit.