An LLC Resonant AC-DC Converter with PFC Function Based on a Double Inductor Structure

摘要

The traditional AC-DC power switching supplies often use the diode rectifier, due to the presence of the large filter capacitor and the switching devices, the power factor of the circuit is usually low, and the harmonic pollution in the grid side is serious. To solve the problem, a method that cascades a PFC (power factor correction) circuit is generally used, however, this increases the circuit stages, which not only reduces the circuit efficiency, but also causes the circuit structure and the control strategy more complex. In this paper, we study a kind of LLC resonant AC-DC converter circuit with PFC function based on a double inductor structure circuit, which can realize the single-stage power conversion and improve the power transmission efficiency. The characteristics of the circuit can achieve the conventional LLC resonant conversion, which ensures the switching devices working in soft-switching mode. And the double inductor structure PFC circuit, using interleaving methods, can better overcome the harmonic distortion problem in the input current in the traditional single-stage PFC AC-DC circuit. In this paper, the theoretical analysis and simulation of the circuit topology are given out, and the experimental results verify the correctness of the theoretical analysis, it also proves that the circuit can both have a good PFC and a AC-DC transform function.