Design Of Switching Power Supply Based On Current Limit Control

Switching Power Supply(SPS), because of its small size, light weight,high efficiency, low cost, wide input voltage range, is widely used inmobile phone, PAD, notebook computers and other portable electronicdevices. The strong demand of high efficiency and low power IC will bringa good market prospect of SPS.An off-line fly-back AC-DC Switching Power Supply chip based oncurrent limit control is presented. This chip uses1um700V BCD process,input of220V directly, five-pin DIP package, a power MOSFET is internalintegrated, has the advantages of simple structure, high integration, andeasy application. Its input is85~265VAC, the output is10V1A, themaximum efficiency is90%. By monitoring the current through powerMOSFET, this chip could adjust current limit stalls to control powerMOSFET on and off, which will control the output power and improve theconversion efficiency under different load conditions. Otherwise, this chiphas additional functions such as output short and overload protection, autorestart, over temperature protection, frequency jitter, leading edge blanking,input line under voltage detection.This dissertation introduces the development of SPS, and the principlesabout the classification, topologies, modulation, working mode. The topdesign of SPS, including pin functions as well as the sub-module functionsand their connections, is provided. The design and analysis of the currentlimit module, auto restart module, reference source module includingbandgap voltage source and current limit source by piecewise linearcompensation are presented. The simulation results show that this chip is designed to meet the expected design specifications. At the end, the layoutdesign and an application circuit of the Switching Power Supply chip aregiven.