Abstract: A semiconductor power module is configured to prevent concentration of load in a certain semiconductor power switching element. A diagnosis circuit (PC) of a module (10a or 10b) compares a sensing signal (SSE) for example, which is sent out from a sensing circuit (Se) and is proportional to the collector current of an IGBT element, with a reference voltage, and judges presence or absence of abnormality in the collector current. If abnormal, a shutdown signal (S.sub.SD) is sent out to a shutdown circuit (SD), and the IGBT element is cut off, and simultaneously an abnormality detection signal (S.sub.F01 or S.sub.F02) is sent out to the other module (10b or 10a). The diagnosis circuit (PC of the module (10b or 10a) receives the abnormality detection signal (S.sub.F01 or S.sub.F02), and sends out the shutdown signal (S.sub.SD) to the shutdown circuit (SD), thereby shutting down the IGBT element. Since the transmission timing of both shutdown signals (S.sub.

Abstract: In order to prevent a malfunction caused by an electrical noise and limit an excessive main current at a high speed while cutting off the same to a value close to zero, the main current is regulated by an IGBT (1) which is connected with a load. A part of this main current is shunted to another IGBT (2). The as-shunted current flows through a resistor (3), to be converted to a voltage across the resistor (3). When the main current is excessively increased by shorting of the load or the like, this voltage exceeds a prescribed value so that a transistor (5) and a thyristor (7) enter conducting states. Consequently, a voltage across a gate (G) and an emitter (E) of the IGBT (1) is so reduced as to cut off the main current. The transistor (5) prevents the main current from excessive increase since the same has a high speed of response, while the thyristor (7) cuts off the main current to zero since the same has lower resistance in conduction.