Quasi-resonant Multi-mode Flyback AC/DC Contoller

As the development of economy and progress of scientific, our society focuses more and more attention on saving energy. Governments and industry associations make energy standards to conform to this trend. California Energy Committee (CEC), energy star, Federal Energy Management Plan (FEMP) and the appropriate agencies in China or Europe all constitute laws and regulations to restrict the maximum power of usually consumer electronic devices in standby and load mode. Not only to save energy, but also to satisfy relevant regulations, it's significant to make a study of improving products' efficiency.QR (Quasi-Resonant) mode, PWM (Pulse Width Modulation) mode, PFM (Pulse Frequency Modulation) mode, green mode has high converting efficiency only in the specific load condition. Taking advantage of this feature, the dissertation proposes a multi-mode quasi-resonant flyback AC/DC controller. By controlling the conduction time and switching frequency separately, chip can switch mode to fit the particular load condition. AC/DC converter can achieve a properly high efficiency in full load condition.The dissertation analysis principles of switching mode power supply and feature of every mode. To achieve multimode control, chip concludes references, mode clamp, voltage clamp, soft start, fault logic, conduction time control, oscillator, output, quasi-resonant module. Designs and simulation results of every module are detailed in the dissertation. Top simulation of chip shows that automatic mode switch is achieved and convert efficiency is properly high.All the design and fabrication are based by 1.5um 25V BCD technology. Test results of fabricated modules can also be found in this dissertation.