A novel feedback scheme for reducing standby power of flyback converter

A novel feedback network and the related circuit design for isolated flyback converters are presented. The proposed feedback topology generates a feedback signal which is in opposite phase with the conventional one to achieve low power consumption under light/no-load conditions. For implementing the proposed scheme, a PWM controller and a secondary-side integrated circuit are designed using the SPICE model for VIS 0.5-μm 5-V/40-V high-voltage CMOS process. Simulations reveal that a 12-V/18-W flyback converter adopting this proposed feedback technique saves a power of 30 mW under no-load condition and improves the system efficiency by 1% under 10%-load condition.