Zero-current-transition converters for high-power-factor AC/DC applications

Zero-current-transition, discontinuous-conduction-mode (ZCT-DCM) converters are introduced in this paper. Compared to hard-switching (PWM) converters in DCM, the ZCT-DCM converters have similar current stresses and conduction losses, and much reduced turn-off switching losses. At the expense of increased voltage stresses, current/zero-voltage switching is maintained wide range of loads and voltage conversion ratios without the need for auxiliary active devices. In AC/DC applications, high power factor is obtained automatically, without the need for active control over the input current. An experimental 100 kHz, 500 W ZCT-DCM Sepic rectifier with isolation transformer and single IGBT switch is described.