With Multiple Working Mode Of High Efficiency Ac/dc Switching Power Supply Chip Design

With the fast development of the electric and electronic technology, all kinds of electronic equipments become the necessity in human’s life and work. As the consumption of the energy increases, peoples are becoming focus on the efficiency. The requirement for stable, high efficient, safe power product is becoming more and more eager. Most electronic equipments can not be powered by the city electricity, so the monolithic AC/DC power IC is widely used because the advantage of highly integrated, high efficiency, high cost performance.The objective is to design a monolithic off-line AC/DC switching power IC which can be used for adaptors for Notebook, Monitors and so on. This chip integrate a700V power MOSFET, it can work at multi-mode to maximize efficiency at all loads with extended power range, the output overvoltage protection is user programmable for non latching or latching shutdown witch can sense both primary and secondary, it has the function of line under-voltage or line overvoltage detection, the current limit is programmable, line voltage feed-forward can reject the line ripple, this chip can work at two different frequencies132K or66K, integrated soft-start for minimum start up stress, frequency jittering to reduce EMI, hysteretic thermal shut-down.This thesis first present the theory of the fly-back topology, then introduce the circuit structure and the working principle of this chip and presents the details of the circuit design and simulation results including the OSC, Frequency jittering, PWM,UV/OV. The function of the whole circuit is verified by simulation. Then BCD process and the design of the layout is introduced. Finally, the main characteristics and work of this issue is reviewed.