Research On AC/DC Resonant Converter With PFC Part

The fast advance in VLSI technology made smaller, mor powerful systems available. At the same time, it called for high power density and low profile power system. For some topologies their high switching loss related to high turn off current limited the power efficiency. To achieve this goals, it is necessary for a good performance topologies call for lou conduction loss, low voltage stress, low switching loss with wide input range.On the labor basis, the LLC resonant half-bridge DC/DC converter with FOT-PFC is analyzed in detail. Three advantages are achieved with this resonant converter. First, ZVS turn on and low turn off current of MOSFETs are achieved. The switching loss is reduced so we can operate the converter at higher switching frequency. Second advantage is that with this topology, we can optimize the converter at high input voltage. And last advantage is that with this topology, we can eliminate the secondary filter inductor, so the voltage stress on secondary will be limited to two times the output voltage, better rectifier diodes can be used and secondary conduction loss can be reduced. The converter ulilizes leakage and magnetizing inductance of a transform. This thesis has discussed the operational process, character, steady-state operation and small signal character. Based on a delailed quantitative analysis this thesis present a comprehensive design methodology for an LLC resonant converter with FOT-PFC. This allow the converter can not only fulfill input voltage and output power specification data but also soft-switching and no-load operation constraints.This thesis presents the test result of a 360W AC/DC samples, it could achieve a 0.98 PF and 0.85 efficiency.