Method for controlling push-pull series-resonant converter switching power supplies with regulated output voltage

摘要

A push-pull series resonant converter switching power supply includes an inductive transformer with a primary winding and at least one secondary winding. Two semiconductor switches are interconnected at a circuit node and connected in a half-bridge circuit between an input potential and an input ground potential. A series-resonant circuit connected between the connecting node and the input ground potential includes a capacitor and an inductor connected in series with the primary winding of the transformer. Diodes are connected between the input potential and the input ground potential for preventing a potential at the capacitor from significantly exceeding the input potential. An output is connected to the secondary winding of the transformer for supplying an output voltage. A control circuit triggers the two semiconductor switches with turn-on pulses for regulating the output voltage to a constant value as a function of a load to be connected to the output by variation of a turn-on pulse repetition rate. A method for controlling the push-pull series resonant converter switching power supply includes controlling a maximum allowable repetition rate of the turn-on pulses and the duration of the turn-on pulses as a function of the input potential.