A 3 kW soft switching DC-DC converter

This paper presents a circuit technique designed to reduce the negative impact of reverse recovery in the rectifiers for high output voltage converters. This technique works by combining reduced amplitude of the reverse recovery current and a lower voltage across the rectifier during the turn off commutation. Another major advantage of the proposed circuit is the fact that the current reflected in the primary is shaped to a triangular form with a low dl/dt during the turn on of the main switch. This will allow the completion of the resonant transition to zero voltage across the primary switches. In the secondary section the reverse recovery current is reduced due to low, dI/dt current slope at turn off and the reverse voltage is clamped to the output voltage. The maximum reverse recovery voltage does not exceed the output voltage. The soft commutation in the primary section and the secondary allows a higher frequency of operation without penalty in efficiency. A 3 kW converter for on board battery charger in electric vehicles provides an output voltage between 170 V to 380 V. Efficiency above 96% is obtained at a switching frequency of 250 kHz while the power density of the converter exceeds 100 W/inc/sup 3/.