[Abstract]:With the rapid upgrading of consumer electronics and information technology (IT) products, the miniaturization and efficiency of switching power supply has become an inevitable trend of development. In order to reduce the pollution of current harmonic to the power grid and improve the quality of power supply, the switching power supply usually adopts the two-stage circuit topology of the first stage as power factor correction (PFC) and the second stage as DC-DC converter. An interleaved Boost converter is used to construct the front-stage PFC circuit, which can reduce the input and output current ripple and the current stress of the switch transistor, and improve the power density of the circuit. The control scheme adopts constant on time control based on the inductor current critical conduction (CRM) mode, which can simplify the circuit structure and reduce the switching loss and electromagnetic interference (EMI);). Due to its soft-switching characteristics, LLC resonant converter is suitable for high switching frequency, and has a wide input voltage range and strong dynamic response. It has become the first choice of circuit topology for later-stage DC-DC converter. In order to improve the efficiency of low voltage output, the synchronous rectifier technology is introduced into the LLC resonant converter, and the control of the synchronous rectifier is realized by detecting the drain source voltage. On the basis of the above, the working principle of the high power factor half bridge LLC resonant circuit with synchronous rectifier is analyzed in detail. The specific design process and parameter selection basis of the circuit are introduced. Finally, two experimental prototypes are developed respectively. One 300W interleaved boost PFC prototype and the other 240W LLC resonant circuit prototype with synchronous rectifying half-bridge were debugged and the corresponding experimental waveforms were given. The experimental results show that the system achieves high power factor and high efficiency.