Off-line Switching Power Supply Chip Central Molecular Circuit Analysis And Design

Because of the virtues of high integration level, the most cost effective, the lest component count switcher solution, high performance, forming high efficiency power supply and so on. Monolithic SMPS (switching mode power supply) management Integrated Circuit was now widely used. Most of monolithic SMPS chips made abroad are based on BCD process. Although, they have excellent performance, but also have high cost.An off-line switcher chip is developed. A power MOSFET with breakdown voltage exceeds 700 is integrated on this chip, the maximum output power is about 15W, working frequency is fixed at 132 kHz, protective functions has been integrated. We use the patent of XingBi Chen, not using the method of medium insulation or PN junction insulation (BCD process), but make high voltage power device and low voltage CMOS circuit on a same silicon wafer through general CMOS process, which makes SPIC is more cost-effective.The basic theory of SMPS and PWM, PFM are given first. Then, introduce flyback converter, and simple on/off control mode is particularly introduced. And then plot out the system framework. Finally, some of the sub circuits witch the author designed are analyzed. Including noises of power supply insulation, states latch circuit, oscillator with frequency jitter and current limiter. All these sub circuits are theoretically analyzed and calculate some of the important parameter, and then the simulation results are given out.