This is a design circuit for a power supply. This circuit is basic for high power supply that is based on LM317 for the regulator IC. This is the figure of the circuit.
How is the circuit work? Zener diode D1 ensures that the LM317H sees only a 5V input-output differential over the entire range of output voltage from 1.2V to 160V. Since high-voltage transistors by necessity have a low β, a Darlington is used to stand off the high voltage. The zener impedance is low enough that no bypass capacitor is required directly at the LM317 input. (In fact, no capacitor should be used here if the circuit is to survive an output short!) R3 limits short circuit current to 50 mA. The RC network on the output improves transient response as does by passing the ADJUST pin, while R4 and D2 protect the ADJUST pin during shorts. [Circuit schematic source: National Semiconductor Notes].
How is the circuit work? Zener diode D1 ensures that the LM317H sees only a 5V input-output differential over the entire range of output voltage from 1.2V to 160V. Since high-voltage transistors by necessity have a low β, a Darlington is used to stand off the high voltage. The zener impedance is low enough that no bypass capacitor is required directly at the LM317 input. (In fact, no capacitor should be used here if the circuit is to survive an output short!) R3 limits short circuit current to 50 mA. The RC network on the output improves transient response as does by passing the ADJUST pin, while R4 and D2 protect the ADJUST pin during shorts. [Circuit schematic source: National Semiconductor Notes].
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