Control Chip Design Of Flyback Converter

With the popularity of portable consumer electronics, switched mode power supplies based on the flyback topology have gained more and more market demand. Meanwhile, with the digitization trend of power industry, digital control of switched mode power supply came into being, and became hot topic of power supplies because of its high reliability, high integration and high flexibility.A novel digital control chip for flyback topology is proposed in this paper. According to design procedures, first the basic structure of digital control system was introduced, along with the detail design scheme of key modules, which are digital compensator, analog-to-digital converter and digital pulse width modulator.Complete theoretical design process is presented for digital control system, along with deep discussion of key issues:theoretical analysis of quasi-resonant control scheme in system efficiency improvement; modeling analysis of quantization effects and limit cycle oscillation phenomenon brought by digital control; Step-by-step analysis of digital compensation design.Finally, analog modules in the system, including the current bias circuit, the voltage reference circuit, LDO and oscillator are proposed with whole design process and simulation results.The chip is designed in CSMC 0.18μm 25V BCD process and verified by simulation.