Distortion Behavior Analysis of General Pulse-Width Modulated Zeta PFC Converter Operating in Continuous Conduction Mode

For most actual power applications, power-factor correction (PFC) converters usually operate in the stable continuous conduction mode (CCM), but input current distortion will occur as long as these converters operate in oscillatory condition. This distortion usually manifests itself as a local oscillation within one line cycle. Typically, a Zeta PFC converter under the general pulse-width modulated (GPWM) control possesses high performance, and requires simpler control circuitry with fewer external components. However, due to the large-signal nonlinearity of the GPWM controller, the dynamic analysis and modeling of the input current distortion in its PFC converters remains vacant. In this paper, a large-signal average SPICE model is derived to capture the time-domain waveforms of the input current and output voltage. A power-balance approach for the PFC converter operating in CCM is developed, which can predict the steady-state values of the converters by using the Fourier series expansion. Analysis of the distortion behavior is provided in terms of the proposed model and the unbalanced power transfer mode. Experimental results are presented to verify the proposed method.