CPC H02M 3/33592 (2013.01) [H02M 1/38 (2013.01); H02M 3/01 (2021.05); H02M 1/0058 (2021.05); H02M 3/33523 (2013.01)] | 20 Claims |
15. A control method of an isolated switching converter, wherein the isolated switching converter has a transformer having a primary winding and a secondary winding, a primary switch coupled to the primary winding and a secondary switch coupled to the secondary winding, the control method comprises:
generating a pulse frequency modulation signal based on a feedback signal indicative of an output voltage of the isolated switching converter;
coupling to the secondary switch and generating a valley pulse signal by detecting one or more valleys of the resonant voltage across the secondary switch;
generating a target valley number based on the pulse frequency modulation signal, the valley pulse signal and a last-cycle valley number and providing a valley enable signal corresponding to the target valley number;
generating a primary on enable signal based on the valley enable signal, the pulse frequency modulation signal and the valley pulse signal;
sending the primary on enable signal to an input terminal of the isolation circuit and generating a synchronous signal electrically isolated from the primary on enable signal; and
generating a primary control signal to control the primary switch based on the synchronous signal.
|