| Single-chip switch power supply (AC/DC power IC) has many virtues such as high integration level, most cost effective, lowest component count switcher solution and high performance. Its being used can form high efficiency insulated switch power supply without using utility power transformer. The increasing rates of power supply in market are forcing higher levels of integration of small, light and tiny.Based on the Trench DMOS technology, a type of AC/DC switch power supply management IC is designed. It works at high frequency with pulse width modulation (PWM) mode; the maximum operation temperature is 135℃; The working frequency is fixed at 100 KHz and the range of duty cycle is 2.7% to 67%. The noteble feature is that the ripple is less than 5% and the efficiency is up to 90% ,while the range of input voltage is 85 to 265VAC and the output voltage is 5V。In the paper, the characteristics of TOP-Switch series and the basic theory of PWM mode is given firstly. Then the total structure of the IC is present according to the function requirement. In the meantime, the working theory of all sub-circuits is described and all sub-circuits are designed and simulated carefully. Besides, the synthetic circuit is simulated about power-up working, normal working, automatic restart working and over-current working; the results of simulation meet the function requirement.Then the possible process and internal power MOSFET structures are given, especially the Trench DMOS structure. At last, the parameter designs of the external application circuit are detailed presented. And all the simulations are operated in Cadence.
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