Voltage clamped parallel resonant converter with controllable duty cycle

摘要

A high efficiency static voltage clamped parallel resonant converter for converting power between two AC and/or DC circuits includes a link circuit between an input switch circuit and an output switch circuit. The link circuit comprises a parallel resonant circuit and link switch elements which are switched to generate a unipolar train of link voltage pulses. All of the switches are "soft-switched" on and off at substantially zero voltage or zero current. Each link voltage pulse consists of a zero segment and a non-zero segment. The duty cycle of these voltage pulses is controllable by the link switches and such that the duration of the zero and non-zero segments are independently controllable. Pulse width modulation (PWM) and pulse area modulation (PAM) can be applied for reduced filtering requirements and maintaining high efficiency for operation at fractional load conditions. The link voltage is clamped to a maximum voltage during the non-zero segment of each link voltage pulse. Resonant oscillation due to the resonant circuit is active only during the transitions between the zero and non-zero voltage levels of the link voltage pulses. As a result, all converter components will be exposed to voltage and current levels which are higher than the load voltage and current levels by just a small fraction.