An Asymmetric Control Method for Switched-Capacitor-Based Resonant Converters

This article proposes an asymmetric control method for switched-capacitor-based resonant converters (SCRCs). The proposed method simultaneously controls the switching frequency, phase-shift angle, and the duty ratio of each half-bridge circuit. By controlling the duty ratios, the asymmetric control method is capable to regulate the switched-capacitor average voltage, allowing the asymmetric resonant current to flow. Either positive or negative portion of the asymmetric resonant current always resembles the resonant current with the frequency and phase-shift control method at the nominal voltage conversion ratio even though the actual voltage conversion ratio is not equal to the nominal value. As a result, the asymmetric control method is capable to reduce the operating frequency, and thus, improves the power conversion efficiency by reducing the frequency-dependent losses. A 350-kHz, 3-kW prototype was constructed and tested to verify the loss reduction and the improvement in the conversion efficiency. The SCRC with the proposed asymmetric control method reduces the power loss by 40% compared with the frequency and phase-shift control method and exhibits the maximum power conversion efficiency of 98.6% at the input and output voltages of 300 and 200 V.