The Analysis of the Charge Unbalance in Flying Capacitors of a Novel Three-level ZVS Converter

This paper analyzes the two different operation principles of an improved three-level ZVS converter, which employs a coupled inductor to achieve zero-voltage switching, under two different control strategies. It indicates that an inapposite choice of control strategy will cause the charge unbalance in flying capacitors and result in the failure of the three-level operation under light load and open voltage loop condition (this condition may occur in dynamic load). The reasons are analyzed in detail. With a modified control strategy the charge unbalance is removed, and a 1kW, 80kHz experimental proto type is made to verify the phenomena and the theoretical analysis.