Abstract: For use with a three-phase boost converter having a primary stage with a primary rectifier and a primary boost switch coupled between an input and output of the three-phase boost converter, an auxiliary stage, method of reducing input current total harmonic distortion (THD) at the input of the three-phase boost converter, and a three-phase boost converter employing the auxiliary stage and method. In one embodiment, the auxiliary stage includes first, second and third auxiliary boost inductors coupled to corresponding phases of the input. The auxiliary stage also includes an auxiliary boost switch, interposed between the first, second and third auxiliary boost inductors and the output, that conducts to draw corresponding phase currents through the first, second and third auxiliary boost inductors thereby reducing input current THD at the input of the three-phase boost converter.

Abstract: To protect a semiconductor switch from high forward blocking voltage stresses during turn-off, a relief circuit is provided comprising a diode and a capacitor. The energy generated when the semiconductor switch is turned off or switched to the non-conducting state, is temporarily stored in the capacitor of the relief circuit until the semiconductor switch is changed back to its conducting state. Then the energy stored in the capacitor is transferred to a useful impedance by means of a further semiconductor switch being changed to its conducting state.