Siemens Aktiengesellschaft

Siemens Mobility Gmbh

Andreas März

Mark-Matthias Bakran

Stefan Hans Werner SCHÖNEWOLF

In a method for protecting a field-effect transistor, which is operated in a switching mode, against an overload current in a switched-on switching state, an electric drain-source voltage between a drain connection and a source connection of the field-effect transistor is detected. The drain-source voltage is compared with a predefined voltage comparison value, and the field-effect transistor is switched into a switched-off switching state in the event that the drain-source voltage is greater than the voltage comparison value. For the purpose of providing a temperature compensation of the protection, the temperature of the field-effect transistor is detected; and the voltage comparison value is adjusted depending on the temperature. The voltage comparison value is, in addition, also dependent on time during the switched-on switching state.

Protection of a field-effect transistor, which is operated in a switching mode, against an overload current

A switching half-bridge has two field-effect transistors and a supplementary circuit arranged upstream of a gate terminal of a first field-effect transistor and formed of a first circuit branch having a damping resistor and an inductor connected in series with the damping resistor and a second circuit branch being connected in parallel with the first circuit branch and having a series resistor and an auxiliary switch connected in series with the series resistor. The half-bridge can be switched from a first switching state to a second switching state, wherein while the auxiliary switch is open, a change in the control voltage causes the first circuit branch to temporarily change the gate-source voltage of the first field-effect transistor from the switch-on level to a second switch-off level greater than a first switch-off level, with the gate-source voltage thereafter returning to the first switch-off level.

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Leinburg, Germany

Andreas März