| Recently, the strong demand of consumer electronic products require high-level power supply modules.These modules provide constant current or constant voltage for the electronic products to guarantee them work stably.There is a wide application of constant current or constant voltage power supply modules,like battery charging process mainly experiences constant current(CC) and constant voltage(CV) phases.AC-DC switching power converter is a circuit which takes power transistor as a switch to control ON state and OFF state realizing AC to DC conversion.It has an advantage of high conversion effiency, low power loss, small size, and wide input range,which is suiteable to apply in modern electronic decives.AC-DC controller is the heart of AC-DC converter, and its design should take things below into consideration: conversion effiency, size, power dissipation and stability.In this paper, a design method of offline,high stability AC-DC converter used in constant voltage or constant current output applilcation is proposed.Then we proposed the design of the heart of this converter: AC-DC controller.The controller chip is designed and implemented using TSMC's 0.6 um CMOS high-voltage mixed process. It drives the emitter of an external NPN transistor, and series with transformer to consist a flyback topology.The system is offline through the use of transformers and opto-coupler transistor.A control logic module is integrated to realize that the converter works on pulse-width modulation (PWM) mode at heavy load and pulse-skipping modulation (PSM) mode at light load,toachieve high effiency conversion on low circuit spend. Meanwhile,the controller introduces frequency jitter technique to reduce the EMI and slope compensation to make the open loop stable. After system level modeling and simulation were made, the design results indicated: the chip can realize 5.0V constant voltage and 1.0A constant current output stably based on two operation modes.
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