Research Of Bridgeless Boost PFC Technology

In order to restrain harmonic pollution and improve power system quality, power factor correction circuit is applied in pre-stage of power supply. In conventional Boost PFC topology, the consumed power for rectifier will increase with the increase of power, which seriously limits its application in the high-power occasions. In recent years, the bridgeless Boost PFC topology was proposed. By omitting rectifier, this proposed topology greatly reduces the conduction losses, and be suited for using in the high-power occasions.The thesis makes a deep study on bridgeless Boost PFC technology, analysing several bridgeless Boost circuits emerged at present and the circuits'EMI, proposing a novel Boost PFC circuit with simple control and low EMI.Based on the proposed bridgeless PFC topology, this thesis makes a contrast study of the average current control and one-cycle control (OCC), and designs corresponding control circuits with the two control methods. In the average current control system, the parameters of input voltage sensing circuit, voltage error amplifier and current error amplifier are designed. The input voltage sensing circuit uses resistance network. This method can obtain simple sensing circuit, small distortion factor and good control performance comparing with the old method. PFC circuit is nonlinear system. This thesis uses OCC method to obtain quick dynamic response and robustness. The designed OCC system can cancel error in every cycle and obtain high power factor by using reset integrator. The contrast analysis of the two control strategies is also introduced. This can provide a guid for choosing control method of bridgeless circuit.Based on average current control chip L4981 and one-cycle control chip IR1150, a 2000W bridgeless Boost PFC prototype with 220±20%VAC input voltage and 400V DC output voltage has been made. The experimental results satisfy design requirment and the proposed bridgeless PFC circuit has good performance.