High Power Factor CRM Boost PFC Converter With Optimum Switching Frequency Variation Range Control Based on Variable Inductor

Critical conduction-mode boost power factor correction converter with constant on-time control is widely used in low-to-medium power applications. However, the range of the switching frequency varies with different input voltages and load conditions. In this letter, a theoretical all-fixed switching frequency method based on the continuous variable inductance control is proposed first. Considering that the existing variable inductor technology is difficult to achieve a wide variation range, a switching frequency optimization compromise based on the segment variable inductance (SVI) control is put forward. Ensuring unit power factor, the proposed method significantly reduces the switching frequency variation range, which facilitates the electromagnetic interference filter design. A prototype with SVI control has been built and tested in the lab to demonstrate the validity of the proposed method.

I. Introduction

Power factor correction (PFC) technology can reduce or eliminate the input current harmonics, and meanwhile reduce the phase difference between the fundamental current and the input voltage, which is an effective way to solve the harmonic problem [1]–[4]. Critical conduction-mode (CRM) boost PFC converter is widely employed in low-to-medium power applications because of its several merits [5]–[7]. However, the switching frequency of the CRM boost PFC converter varies in a half line cycle, and the variation range increases with the root-mean-square (rms) input voltage. The study in [8] limits the output voltage and power of the CRM boost PFC converter to keep the switching frequency within a predefined range considering that the input voltage and load resistance vary to some extent.