Method and circuit arrangement for limiting an overvoltage
First Claim
1. A method for limiting an overvoltage at a freewheeling device arranged in parallel with a semiconductor power switch, with at least a first and a second semiconductor power switch each parallel-connected with a freewheeling device being connected in series, and with an output terminal arranged between the first and second semiconductor power switch for coupling to an inductive load, the method comprising the steps of:
- providing a feedback path between output and control terminals of the semiconductor power switch, the feedback path comprising a transformer in series with an amplifier connected to a common input of a push-pull stage of a gate driver connected to the control terminalcontrolling one of the semiconductor power switches into the turned-off state and the other one into the non-turned-off state, andswitching the turned-off semiconductor power switch, at least at the instant of the occurrence of an overvoltage at the associated freewheeling device or during the decay of a current spike, temporarily on to such an extent that a short-time current is generated at the output of the semiconductor power switch.
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Accused Products
Abstract
In order to limit an overvoltage at a parallel circuit of IGBT (3) and freewheeling diode (7), an undesirable current spike is used to switch on the intrinsically turned-off IGBT (3′) during the presence of the current spike precisely to an extent such that a current which counteracts the overvoltage arises in the IGBT/freewheeling diode pair. The oppositely acting current reduces the current gradient in leakage inductances (Lσ) and reduces the undesirable induced overvoltages.
20 Citations
9 Claims
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1. A method for limiting an overvoltage at a freewheeling device arranged in parallel with a semiconductor power switch, with at least a first and a second semiconductor power switch each parallel-connected with a freewheeling device being connected in series, and with an output terminal arranged between the first and second semiconductor power switch for coupling to an inductive load, the method comprising the steps of:
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providing a feedback path between output and control terminals of the semiconductor power switch, the feedback path comprising a transformer in series with an amplifier connected to a common input of a push-pull stage of a gate driver connected to the control terminal controlling one of the semiconductor power switches into the turned-off state and the other one into the non-turned-off state, and switching the turned-off semiconductor power switch, at least at the instant of the occurrence of an overvoltage at the associated freewheeling device or during the decay of a current spike, temporarily on to such an extent that a short-time current is generated at the output of the semiconductor power switch. - View Dependent Claims (2, 3, 4, 5, 6)
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- 7. A circuit arrangement for limiting an overvoltage at a freewheeling device arranged in parallel with a semiconductor power switch, comprising at least a first and a second semiconductor power switch each parallel-connected with a freewheeling device being connected in series, an output terminal arranged between the first and second semiconductor power switch for coupling to an inductive load, wherein a feedback path is provided between output and control terminals of the semiconductor power switch, the feedback path comprising a transformer in series with an amplifier connected to a common input of a push-pull stage of a gate driver connected to the control terminal wherein a voltage drop across internal and/or external leakage inductances which are coupled in series with said first and/or second semiconductor switch is utilized for the feedback.
Specification