Switching Power Supply Pwm Control Circuit Chip Design

Electronic systems become more and more popular with the development of electronic science and technology. Electronic equipment has more and more demands on the power supply .The core of switching power supply control circuit to achieve integrated is the development direction of switching power supply .Single-chip switching power supply with good frequency characteristics, high linearity and small output voltage ripple , etc., has been used in the communications, computer and other fields widely.Based on Shanghua 0.5umCMOS technology and using the Hspice and Cadence EDA ,A type of current feedback PWM is designed. In this paper ,the basic theory of current feedback PWM is given firstly. Based on its actual application, the all sub-circuits including digital circuits and analog circuits are designed. The digital circuits include inverter, AND gate, OR gate, RS type flip-flop and 8 frequency divider. The analog circuits include reference circuit , PWM comparator, error amplifier, oscillator generator, ramp compensation, soft activation and some protection circuit. The result show the reference circuit has smaller temperature coefficient and wide voltage range; At the same time, the design of the error amplifier , frequency compensation , the ramp compensation circuit and protection circuits are introducted.In this paper, the operating frequency of switching power supply PWM is 100KHz,maximum duty cycle of the output signal is the 75% , the temperature range is 0℃～130℃.