| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent a load from concentrating on a part of semiconductor power switching elements. SOLUTION: A diagnostic circuit PC of a module 10a (10b) judges whether abnormality is generated in a collector current, by comparing, e.g. a sensing signal SSE which is sent out from a sensing circuit Se and proportional to the collector current of an IGBT element with a reference voltage. When an abnormality exists, a cutoff signal SSD is sent to a cutoff circuit SD, and the IGBT element is cut off. At the same time, an abnormality detection signal SF01 (SF02 ) is sent to the other module 10b (10a). When the abnormality detection signal SF01 (SF02 ) is received, a diagnostic circuit PC of the module 10b (10a) sends a cutoff signal SSD to the cutoff circuit SD, and cuts off the IGBT element. Both timings of sending the cutoff signal SSD coincide with each other, so that both of the IGBT elements are simultaneously cut off. Hence it can be prevented that either one of the IGBT elements is cut off in advance and a load concentrates on the other belated IGBT element.</p> |
