Research On Digital Control Of APFC Technology

With the rapid development of electronic power technology, more and more electric and electronic equipment are put into the power grid. It could cause power factor reducing and harmonic damage. Active Power Factor Correction (APFC) technology is an important strategy which can effectively reduce the rectification circuit harmonic current. This technology can make the input current have same phase to the input voltage and improve the power factor. However, the traditional power factor correction technology using analog control has many defects, and now with the development of digital control technology, more and more the control strategy adopting a digital signal processor (DSP) could be achieved. The control strategy is realized by digital control, which makes the switch frequency higher, but the switching losses increase same time. Thus, it must be considered how to reduce the switching loss in research of high power factor correction technology for high frequency applications.In order to solve the switching losses problem and improve the overall performance of the circuit, the ZVS soft-switching technique is applied into the digitalized PFC control circuit for its main and auxiliary switches to achieve soft-switching function, and reduce the switching losses of the device.In this paper, through referring to the reference materials extensively, the circuit topology and control strategy of the power factor correction device based on soft-switching technique are determined. Then the design and simulation process on the main circuit, control circuit, soft-switching circuit and other parts of device, including selection of components and parameters of calculations, are specifically described in detail. The current and voltage double closed-loop control structure are adopted as the control strategy, traditional PI algorithm is used as control algorithm, and designing methods of PI regulator's coefficients based on the simplified average small signal model are given. The Pspice9.2, a kind of circuit special emulator, is applied to analyzing the digital PFC system and the parameters of the equipment are gained by it. Finally the soft-switching circuit for the APFC equipment is implemented, and the digital control of APFC converter based on soft switching with switching frequency 50 kHz is realized by TMS320F2812. And how to design the two loops, hardware and software of control system are analyzed in detail. The simulation and experiment results indicate that this converter's topology structure and control strategy is able to improve the power factor, while the power losses of device are reduced effectively, have achieved the desired performance.