Patent ID: 8614905
Filing Date: 2013-12-24
Classification: H02M,H03K

Abstract:
1. A voltage converting apparatus comprising a series connection of at least four switching elements, each comprising at least one semiconductor device of turn-off type and a free-wheeling diode connected in anti-parallel therewith, where opposite ends of said series connection are configured to be connected to different potentials resulting in a direct voltage across said series connection, and a mid point of the series connection being configured to be connected to an alternating voltage side of the apparatus while dividing the series connection in two halves, a control unit configured to control said semiconductor devices of the switching elements for obtaining a determined alternating voltage on said alternating voltage side of the apparatus, and a measuring device configured to measure a parameter representative of the voltage across each said free-wheeling diode when being turned-off, wherein said semiconductor devices are gate-controlled and have the respective free-wheeling diode built in therein, said control unit comprises an arrangement configured to control the amount of charge stored in each said free-wheeling diode at the moment the free-wheeling diode stops to conduct thereby being turned-off, depending upon the results of said measurement carried out by said measuring device for measuring the parameter when being turn-off through applying a positive pulse on the gate of a said semiconductor device when the free-wheeling diode built in therein is conducting and making the properties of the positive pulse depending upon the results of said measurement carried out by said measuring device.