Single Phase Current Source PFC Based On UC3854

This thesis focuses on the single phase current source PFC circuit. Therefore, the project aims to touch two goals:1) input voltage and input current have the same frequency and are in phase with each other;2) output current can maintain a constant value, as a current source.Compared with the conventional PFC, the power stage circuit is displaced from Boost structure to Buck topology which allows the output voltage to be smaller than the input voltage. Thus, the segment of step down of the voltage can be omitted on the occasion of which small voltage is needed. In addition, a parallel resonant filter is employed to reduce the output inductor and to smooth the output current.Meanwhile, the input current is directly controlled by average current control scheme based on UC3854to deliver near sinusoidal AC current at unity power factor, which is different form the traditional current source PFC that employs the indirect control scheme. Also different from the traditional PFC, the new control system is composed of two current loops. The traditional voltage outer loop is replaced by the current outer loop. A current transducer is used to sense the output current.A200w single phase current source PFC has been developed. With the control scheme, the output current can be kept at1A. Also, the output voltage is200v which is lower than the input voltage220v (RMS), which overcomes the disadvantage of the Boost PFC.The experimental and analyzed results show that the proposed converter can supply a constant DC current to a load, meanwhile, make the input port unity power factor.The proposed converter is applicable to the current source load and the occasion of the low output voltage. It appears that such a converter may also be useful for the battery chargers and UPS applications.