An Improved Constant Current Control Scheme for Multimode PSR Flyback Converter

For low cost and wide power range, the constant current (CC) control scheme for multimode primary-side regulation (PSR) flyback converter is prevalent in low and medium power applications. Although some multimode CC control schemes have been presented to raise CC accuracy, the current deviation caused by the mode conversion and inherent propagation delay remains unsolved. An improved CC control scheme is adopted to mitigate the influence of propagation delay or mode conversion on CC accuracy, which can be added into an IC controller with no extra pin penalty. The proposed scheme is implemented in 0.18 mu m 5V/40V BCD process. The experimental results reveal that the deviation of the output current is within +/- 0.8% under different input and load conditions.