Design Of Critical Conduction Mode Boost APFC Controller XD2812

Widespread using of power electronic devices leads to serious harmonic pollution in the public electricity line, which has caused a lot of useless power consumption. Solving harmonic pollution has become an increasing national attention. The active power factor correction is the main method of power factor correction. Based on the project Theoretical Research and Design of Key Technique for AC/DC convertor with BCD process of the Institute of Electronic CAD of Xidian University, a critical conduction mode APFC controller XD2812is presented in this thesis.Firstly, the development status of the power factor correction technology is proposed in the paper. Secondly, the basic topologies of APFC are described, as well as control methods and operate modes. Thirdly, based on the analysis above, the system design, circuit design and simulation have been completed. XD2812works in the critical conduction mode and is controlled by the peak current mode, which means that\the power MOSFET turns on when the inductor current reaches zero, so the MOSFET switch on is lossless. In XD2812a supply regulation voltage is used as the power supply of most internal circuit, which ensures that the chip operates normally within a wide range of input power supply. Considering that the bandwidth of error amplifier in the control loop is narrow, a two-step over voltage protection circuit is designed. It enables to handle over-voltage safely and promptly either dynamic over-voltage or static over-voltage. Furthermore, to improve the power factor, a novel design can considerably optimize total harmonic distortion of the AC input current by increasing the switch-on time near the zero-crossings of the line voltage.Based on the0.4μm20V BCD process model, each module of the chip and the whole chip is simulated by Hspice. Simulation results show that the chip meets the design requirements of the target and has good control performance of power factor correction.