Analysis of the improved soft-commutated PWM inverter by using an AC current transformer

In the high power DC-DC converter and DC-AC inverter, the soft-commutated PWM technique has been receiving much attention from the viewpoints of decreasing the switching noise, reducing the switching power loss in the main power switch and removing the complicated snubber circuit and so forth. However, the conventional soft-commutated PWM converter and inverter have some defects such as high voltage and/or high current stresses on the switches, the necessity of the additional switches for realizing soft-commutation, and the relatively large power loss caused by the large circulating current composed of the load and resonant ones. This paper presents an improved half-bridge type soft-commutated PWM inverter, in which an AC current transformer and an additional resonant capacitor are employed to realize the soft-commutated PWM operation of the switches and to decrease the circulating current. Consequently, in the proposed circuit. the power loss caused by this circulating current is sufficiently reduced. The operation performance characteristics of this soft-commutated PWM inverter are analyzed. >