An Improved ZVS PWM Three-Level Converter

This paper proposes an improved zero-voltage-switching pulse-width-modulation three-level converter (ZVS PWM TL converter), which is improved from the original ZVS PWM TL converter just by exchanging the position of the resonant inductor and the transformer, such that the transformer is connected with the lagging switches. The improved converter has several advantages over the original one, e.g., the clamping diodes conduct only once in a switching period, and the resonant inductor current is smaller in zero state, leading to a higher efficiency and reduced duty cycle loss. A blocking capacitor is usually introduced to the primary side to prevent the transformer from saturating, this paper analyzes the effects of the blocking capacitor in different positions, and a best scheme is determined. A 2.5-kW prototype converter verifies the effectiveness of the improved converter and the best scheme for the blocking capacitor