Abstract: A voltage balancing circuit for capacitor banks or voltage cells connected in series. The circuit includes a DC-link with at least two capacitors or voltage cells connected in series and at least two emitter follower balancing circuits connected in parallel. At least one emitter resistor is provided between the emitter of each emitter follower balancing circuit and the mid-point of the DC-link. The gate emitter voltage applied to each emitter follower balancing circuit may be equal to its common gate voltage minus the voltage drop on the corresponding emitter resistor. The invention is also directed at a variable frequency drive for driving an electric motor or a power converter, having a corresponding voltage balancing circuit.

Abstract: A method for pulse-width modulation of a power converter (10) and a power converter (10) are presented. The method comprises determining (110) a modulation index, selecting (120), based on the modulation index, a modulation technique from a plurality of pre-deter-mined modulation techniques, and modulating (130) an output (16) of the power converter (10) by utilizing the selected modulation technique.

Abstract: A method for pulse-width modulation of a power converter (10) and a power converter (10) are presented. The method comprises determining (110) a modulation index, selecting (120), based on the modulation index, a modulation technique from a plurality of pre-determined modulation techniques, and modulating (130) an output (16) of the power converter (10) by utilizing the selected modulation technique.