A new family of zero-current-switching PWM converter

Abstract

This paper presents a new family of DC/DC pulse-width-modulated (PWM) converters, featuring soft-commutation at zero-current (ZC) in the active switches. The new ZCS-PWM boost and new ZCS-PWM Zeta converters, both based on the new ZCS-PWM soft-commutation cell proposed, are used as examples to illustrate the operation of the new family of converters. This soft-commutation cell proposed is composed of two active switches (main and auxiliary transistors), two diodes, two small resonant inductors and one resonant capacitor. In this cell, the turn-on of the active switches occurs in zero-current (ZC) and they turn off in zero-current and zero-voltage (ZCZV). For the diodes, their turn-on processes occur in zero-voltage (ZV) and the reverse-recovery effects of them are eliminated. These characteristics makes this cell suitable for insulated-gate bipolar transistors (IGBTs). The family of DC/DC converters, generated based on this new soft-commutation cell, provides conditions to obtain naturally isolated converters, as an example: derived buck-boost, Sepic and Zeta converters. The principle of operation, the theoretical analysis, a design example for the new boost DC/DC converter and experimental results for a test unit with 1.6 kW output power, 400 V/sub dc/ output voltage, 220 V/sub dc/ input voltage, operating with 20 kHz switching frequency, are presented. Its measured efficiency is equal to 98.1% at rated load. Also presented is the principle of operation, the theoretical analysis and a design example for the new Zeta DC/DC step-down converter.