Analysis Of Conducted Electromagnetic Interference Based On Critical Mode Boost PFC

Boost converter is one of the preferred topologies for power-factor-correction (PFC) converter because of its simple topology, high input power factor and low input current ripple. Boost PFC converter can work in continuous inductor current mode (CCM), critical continuous mode (CRM) and discontinuous conduction mode (DCM). In this dissertation, the single path Boost PFC CRM converter is researched. Under different working conditions, a single switching period, the peak inductor current, switching frequency of expression, and the corresponding curves are analyzed in this dissertation. The control modes are simply introduced, including voltage and current mode, the current control mode including average current control and peak current control type. In this dissertation, the peak current control method is used to control the PWM wave, and at the same time to control the on-ofF of MOSFET. At the same time, the parameters of the boost inductor, switch, output capacitance are analyzed and designed, the components of the application model are selected. In the experiment, the parasitic parameters in the circuit has a large impact on the circuit characteristics, non-ideal inductor current impulse phenomenon is occured, thus further analysis of the mechanism of parasitic capacitance and inductance of input parallel resonance is necessary, and the expressions of inverse current impulse is gived. Finally, the ideal model of CRM boost PFC and non-ideal model are established by the MATLAB/ Simulink to verify the reliability of the theory. Finally, A input 90-265V, output 400V prototype is built and the experimental results are provided to verify the analysis.The differential-mode (DM) electromagnetic interference (EMI) noise of boost PFC converter operating in CRM for single-channel is analyzed. Firstly, the mathematical model of EMI receiver is established, including intermediate frequency filter, envelope detector, peak detector, quasi peak detector and the average detector. The high frequency digital oscilloscope is used to collect inductor current, the EMI receiver model is used to analyze inductor current, then the estimate DM noise spectra are calculated. The estimate DM noise spectra of single channel CRM PFC boost converter under different input voltage and input power is calculated by EMI receiver model, the change rule of the DM noise spectra is calculated under different input voltage and input power by EMI receiver model. According to the characteristics of the DM noise spectra, the design of the filter can be effectively guided.