Research On Single Phase Power Factor Correction Circuits And Their Control Strategies

Conventional off-line power converters with diode-capacitor rectifiers have resulted in distorted input current waveforms with high harmonic currents. In compliance with IEC61000-3-2 harmonic regulation, the traditional two-stage approach is the most commonly used power factor correction (PFC) circuit. In this method, a BOOST PFC circuit is adopted as the front end to force the line current to track the line voltage and thus achieve the near unit power factor. The main drawbacks of this approach are its higher cost and larger size resulting from its increased component number and complicated control circuits. Some new researches have been done on how to promote the efficiency and power density and achieve cost down.Partâ… is focused on single stage isolated power factor correction circuit. Some proposed single stage topology and control methods are reviewed, in which several techniche problems in application have been mentioned. For a 90W AC adapter, 4 single stage topologies with coupled PFC inductor and flyback converter are proposed. The characteristic of these topologies operating in DCM and DCM/CCM boundary condition is analyzed, which can help to design the isolated transformerand the PFC inductor to meet IEC 61000-3-2 CLASS D requirement, and alleviate the stress of the bulk capacitor. Small singal model is arrived according to averaged state space method for control loop analysis and parameter design. In order to alleviate the ouput low frequency ripple, the fast dynamic reponse of the outer voltage loop should be ensured. The theoretical analysis is verified by a 90 W prototype and its experimental results.Partâ…¡is focused on interleaved CCM PFC. Compared with conventional BOOST PFC circuit, interleaved application realizes AC/DC conversion through multiple converters, which can help to increase the reliability problem resulting from the parallel application of power device and promote the power level of PFC converter. The characteristic of this two topology will be analysized, including the voltage and current stress and loss analysis. The experiments are based on 400/1200W prototypes for universal input application. The switching frequency of the interleaved CCM PFC converter is 65kHz, which is about half for that of the traditional CCM BOOST PFC circuit. In interleaved circuit, the currents in two converters will be added and the ripple current will be decreased. These two topologies are researched by experiments.