Multi-mode control strategy for primary-side regulation system

A multi-mode control strategy for primary-side regulation (PSR) system is presented. The idea uses four mode control strategy to improve the efficiency under variety load conditions. In addition, the usual peak current control mode is replaced by voltage control mode under standby condition. By this way, the pulse width of drive signal can be reduced regardless of the leading edge blanking time in the peak current control mode when the power switch turns on. Thus the standby power can be reduced when the system switching frequency remains the same as conventional system. The prototype is achieved by using CSMC 700V BCD technology. The experiment results show that the average efficiency is improved about 3.6% comparing with conventional system and the standby power is less than 10mW under different conditions.