| 摘要 |
<p>The present invention relates to a technique of limiting an overcurrent of a power semiconductor element (1) such as an IGBT. In a background art overcurrent protection circuit (10P), when an emitter current (i) and a current sense current (is) do not show the same behavior even in a transient state, the current sense current tends to momentarily increase at a turnoff, and in such a case, the energizing capability of a MOSFET (2P) in the overcurrent protection circuit increases and the turnoff speed of an IGBT (1P) becomes much faster than necessary and as a result, a surge voltage disadvantageously increases. Then, in the present invention, a diode (5) having a forward voltage set not lower than a threshold voltage of the MOSFET (2) is so provided as a voltage clamping circuit (4) between a gate electrode (2G) and a source electrode (2S) as to be biased in the forward direction in an overcurrent protection circuit (10) of an IGBT (1). With this provision of the voltage clamping circuit (4), when a voltage value (is.Rs) developed in a sense resistor (3) becomes equal to or higher than the forward voltage of the diode (5), the diode (5) is energized to cramp a gate voltage of the MOSFET (2) to the forward voltage. <IMAGE></p> |
