Development Of A High Efficiency Flyback Switching Power Supply Based On Power-Factor-Correction

With the rapid development of electronic information industry, power electronics equipments such as switching power supply have been widely applied. At the same time, such conventional switching power supply contaminated electrical network, consequently a novel power supply with power factor correction (PFC), a type of low electromagnetic contamination, emerges as the times require, that is "green power supply". With people's more demand for quality of power, the power supply with high efficiency, little bulk and low contamination have became mainstream of research and development. So striving hard to improve transforming efficiency of DC/DC and utilizing Synchronous Rectifier can be able to improve transforming efficiency greatly. This paper attempts to associate PFC technology with Quasi-Resonant DC/DC Converter and Synchronous Rectifier technology, to work out a novel switching power supply with higher efficiency and low contamination, which both achieved high power factor, improved effecting on electrical network and ensured high efficiency, furthermore, it is easy to be realized and controlled in circuit. Therefore it has great value of application.Firstly, future development of switching power supply, power factor correcting and synchronous rectifier technology is described, and isolation of Quasi-Resonant Flyback Converter is selected from several topology of DC/DC, which may reduces power loss effectively. Next several common topology of PFC are contrasted with their performance, and BOOST circuit elected is analyzed with operating in critical mode, which adopts new technology of output voltage following along with changing of input, not only can bulk of inductance lessen, but also can voltage stress of switching tube decrease, and reaches power factor correcting easily and effectively, this technology should be extended. Because efficiency of Flyback Converter is lower commonly, so this paper improves on technology of common Synchronous Rectifier and schemes out a new high efficiency scheme of Synchronous Rectifier. About current surge when start in wide voltage, corresponding control circuit of start-up is designed in this paper. Finally, to depress Electromagnetic Interference (EMI) and achieve Electromagnetic Compatibility (EMC), EMI filter is designed at input of switching power supplyspecially.This paper constructs small-signal modeling according to entire circuit and analyzes systemic stabilization, which proves stability of it. Simulates parts of circuit using simulation software of OrCAD Pspice A/D, selects circuit components, designs...