Soft start circuit for regulated power supply

摘要

A power supply feedback circuit includes a regulating element at an input side of an optical isolator. The control lead for the regulating element is connected to a voltage divider to receive the divided voltage. A bypass circuit is provided on the voltage divider to change the resistance in a bypassed branch of the voltage divider during start up of the circuit. The bypass time depends on charging of a capacitor at a control lead, base or gate, of an active element by the bypass circuit. The output voltage of the circuit is brought gradually to the desired level as the capacitor charges and the active element removes the bypass from the voltage divider or applies the bypass to the voltage divider.