Interleaved Boost PFC Converter With Coupled Inductor

Boost converter is one of the preferred topologies for power-factor-correction (PFC) converterbecause of its simple topology, high input power factor and low input current ripple. In order toexpand output power, multiple boost PFC converters can be connected in parallel, and they can beoperated with interleaved control to reduce the input and output current ripples. The discrete inductorsof these converters can be magnetic coupled to reduce the number of magnitec components and itsvolume, and improve the performance of the converter. This dissertation is dedicated to analyzing theinterleaved critical-current-mode (CRM) and discontinuous-current-mode (DCM) boost PFCconverter with coupled inductor and the characteristic of differential-mode (DM) conductedelectromagnetic interference of CRM boost PFC converter.In charpter II, the characteristics of a two-channel interleaved CRM boost PFC converter withcoupled inductor are investigated. The inductor current and the input current, the switching frequencyand the flux linkage are derived. Then, the coupling effects on the converter such as the minimumswitching frequency, the maximum flux linkage in the magnetic core legs are presented, and theproper coupling coefficient is discussed. Comparing with the non-coupled case, the converter withcoupled inductor features a higher minmum swithching frequency, a lower flux linkage which meansless turns number and a smaller volume, with the price of enlarging the input current ripple. Thecurves of the above properties varied with coupling coefficient are proved for coupled inductor design.A300W prototype is built and the experimental results are provided to verify the analysis.In charpter III, the two-channel interleaved DCM boost PFC converter with coupled inductor isanalyzed. The inductor current and input current in different modes are derived, and the couplingeffects on the input PF, self-inductance and flux linkage are analyzed. Based on the inductor current isalways working in DCM, the self-inductance of coupled inductor can be increased, which lead tolower peak inductor current and rms value. The input PF is reduced and the maximum flux leakage isincreased by coupling. So, the coupling coefficient of coupled inductor should not be very high. A300W prototype is built and tested in the lab to verify the analysis and coupled inductor design.In charpter IV, the differential-mode (DM) electromagnetic interference (EMI) noise of boost PFCconverter operating in CRM for single-channel, two-channel interleaved with discrete inductors andcoupled inductor are analyzed. The DM noise spectra are calculated based on the EMI receiver modeland the required corner frequency of DM filter are obtained. It can be seen that the minimum cornerfrequency happens when the noises at150kHz reaches its maximum value. According to the relation between the magnitude of inductor or input current ripple and the DM noise with the same frequency,the worst conditions of the nosis spectra which see the maximum noise value at150kHz are figuredout by analysizing the ripple magnitude at150kHz. This method can be used for single-channel andtwo-channel interleaved cases both. The mathematical and experimental resluts are provided at last toverify the analysis. For the two-channel interleaved case, the maximum noise at150kHz is increaseddue to coupling, which means lower corner frequency and larger DM filter. So the couplingcoefficient should be a trade off between the input filter and the coupled inductor.