One flyback off line AC/DC switching power supply design

AC/DC switching power supply is widely used in various types of electronic equipment. In order to reduce the production cost and integrates multi-protection, a design based on off line flyback converter and 0.5μm CMOS process used in this paper. The chip works on constant current state achieved by pulse frequency modulation and constant voltage mode achieved by a unique off-time modulation method. It is also integrates multi-protection functions circuit to avoid the chip working extreme conditions. At last, each module circuit has been simulated by using EDA tools Spectre to meet the design specification.