Based On The Modulation Of Pwm / Psm Efficient Flyback Converter Design,

Portable products. Which accelerate the development of switching mode power supply(SMPS), are largly invented with social progress. Due to small volume, light weight and high efficiency, the SMPS is widely used in many kinds of electronic equipments. Suitable application in high voltage and low power field promotes the fast development in flyback converter. The requirements of high efficiency, high integration desity, low cost, and low energy dissipation are even more than ever because of the market challengesAn AC/DC chip, which integrates PWM and PSM modes for different load situations, is studied in this article. The efficiency is improved by the usage of double modes. This control chip integrates PWM, PSM, MOSFET, protection circuit, soft start circuit, high voltage charging circuit and loop compensation circuit. The out-port is separated from electrical network through high-frequency transformer, that makes monolithic integration achieved and the requirement of power frequency transformer is elimated. This control chip can support step down, step up, forward and flyback topologies.The basic principle of flyback converter is analyzed in this article, PWM, PFM and PSM mode's operating features and the chip whole topview is introduced. Then the soft start, the oscillator, the current limit and error amplifier and the whole circuit are analyzed and simulated, the PWM/PSM modes and autorestarting function are confirmed, standby power loss is computed,3μm high pressure BCD process is used to tipe out, the test results are analyzed to prove the rationality of the circuit.The output voltage of the flyback converter is 13V, with a maximum output power of 20W. The flyback converter can be used in TVs, monitors and some portable equipments. High voltage BCD process is adopted for small area with low voltage and high voltage blocks integrated together.