Design Of Isolated APFC Circuit

With the rapid development of electronic information industry, power electronics equipments such as switching power supply have been widely applied. A large number of harmonic current from electronic machines and electric power devices generate emission of noise interference to peripheral devices easily, at the same time, electric network suffers harmonic pollution. Recently, internal and overseas power supply fields put highly premium on Power Factor Correction technique.Firstly, the paper summarizes the current research situation of correction technology for active power factor. Then the passive PFC approach, the active two-stage PFC approach and the active single-stage PFC approach are analyzed and compared. Furthermore, the virtues and defects of them are point out. For switching power supply , in order to comply with harmonic regulation and realize low-cost ,high-performance ,the single-stage power factor (PFC) techniques have gained much attention these years, especially in low power applications. A single-stage PFC converter combines the PFC stage and a DC/DC converter into one stage with a shared switch and control implements, the input current is shaped and the output voltage is regulated.The principle of active power factor correction circuit is analyzed in this paper and several common topology of APFC are contrasted with their performance. After these , the paper presents the control mode of APFC and summarizes the characteristics. The paper studies the flyback isolated APFC converter in detail, since it achieves high power factor and ensures high efficiency, is easy to be realized and controlled in circuit, can work in boost and buck mode, furthermore, it can be input and multi-output isolated with wide range voltage。According to the electric circuit design target, choosing flyback converter as main circuit and using the L6562a chip to design control circuit, a wide voltage input (150Vac- 280Vac), 48Vdc/8A output APFC electric circuit is designed. This paper introduces the ST's current critical control mode power factor correction chip-L6562a,including the internal structure, functions, principles, as well as some performance improvements. And gives specific power control circuit parameters and circuit parameters calculation and detailed circuit diagram.Using the matlab simulation software, in the simulink environment tools, the electric circuit simulation model is established, and its simulation result is obtained. The output voltage wave is nearly an invariable dc and the input current is not a narrow pulse but a sine wave which meet to the design requirement .