US 11,722,068 B2
Isolated switching converter with secondary side modulation and control method thereof
Hui Li, Hangzhou (CN); Siran Wang, Hangzhou (CN); and Lin Feng, Hangzhou (CN)
Assigned to Chengdu Monolithic Power Systems Co., Ltd., Chengdu (CN)
Filed by Chengdu Monolithic Power Systems Co., Ltd., Chengdu (CN)
Filed on Dec. 9, 2021, as Appl. No. 17/546,805.
Claims priority of application No. 202011622595.6 (CN), filed on Dec. 31, 2020.
Prior Publication US 2022/0209676 A1, Jun. 30, 2022
Int. Cl. H02M 3/335 (2006.01); H02M 1/38 (2007.01); H02M 3/00 (2006.01); H02M 1/00 (2006.01)
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
OG exemplary drawing
 
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.