VOLTAGE CONVERTING APPARATUS AND METHOD FOR CONVERTING A VOLTAGE
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Accused Products
Abstract
A voltage converting apparatus includes a series connection of at least four switching elements each including at least one semiconductor device of turn-off type and a free-wheeling diode connected in anti-parallel therewith. The apparatus has a device configured to measure a parameter representative of the voltage across each free-wheeling diode when turned off and an arrangement configured to control the amount of charge stored in each diode at the moment the diode is turned-off by stopping to conduct depending upon the results of the measurement carried out by the device for controlling the voltage across the diode after turn-off thereof.
10 Citations
32 Claims
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1-12. -12. (canceled)
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13. 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 means 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, the apparatus comprises an arrangement configured to control the amount of charge stored in each said diode at the moment the diode stops to conduct thereby being turned-off, said control depending upon the results of said measurement carried out by said means for measuring a parameter when being turn-off through applying a positive pulse on the gate of a said semiconductor device when the diode built in therein is conducting and make the properties of this pulse depending upon the results of said measurement carried out by said means.
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21. A method for converting a voltage by controlling 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 being gate-controlled having the respective free-wheeling diode built in therein, where opposite ends of said series connection being 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, in which said semiconductor devices of the switching elements are controlled for obtaining a determined alternating voltage on said alternating voltage side of the apparatus,
said method comprising the steps of: -
measuring a parameter representative of the voltage across each said free-wheeling diode when being turned-off, and controlling the amount of charge stored in each said diode at the moment the diode stops to conduct thereby being turned off, said controlling depending upon the results of said measurement of said parameter representative of the voltage across the diode when being turned-off through applying a positive pulse on the gate of a said semiconductor device when the diode built in therein is conducting and make the properties of this pulse depend upon the results of said measuring. - View Dependent Claims (22, 23, 24)
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Specification