Quasi-resonant flyback PSR converter with adaptive frequency control

In this paper, a quasi-resonant (QR) flyback primary-side regulation (PSR) converter with adaptive frequency control is proposed. The converter adopts the PSR scheme to detect load information through the auxiliary winding. The converter employs the QR control scheme to switch in the valley mode either in CV or CC operation, which greatly reduces the switching loss. In addition, according to the load condition, the converter adaptively reduces the switching frequency and realize valley switching, which achieves better light-load efficiency in the CV mode. The proposed QR converter was implemented using the HHGRACE 0.35 mu m BCD process and verified in a 5 V/1A circuit prototype. Experimental results show that the light-load power efficiency of the proposed converter is improved by up to 4.0% when compared to the conventional QR controller. In addition, the valley switching is realized under different load conditions, which improves the system efficiency in the entire range of output load.