| 摘要 |
PROBLEM TO BE SOLVED: To surely detect an overcurrent even in a turn-on period to protect a switching device from the overcurrent. SOLUTION: When a switching signal is inputted from an upper hierarchy control circuit, a predicted collector voltage pattern, which is predicted to be generated when an IGBT 1 is in switching operation, is outputted by a predicted voltage pattern generator 2 to a comparator 4 and a collector voltage of the IGBT 1 is outputted by a collector voltage detector 3 to the comparator 4 for comparing the collector voltage with the predicted collector voltage pattern. If the collector voltage is higher than the predicted collector voltage pattern by a value which is not less than the prescribed value, an overcurrent detection signal is outputted to a gate voltage generator 5 and, if a transistor 55 is turned on by the overcurrent detection signal, a transistor 58 is turned on, and the gate voltage of the IGBT 1 is lowered, a current flowing through the IGBT 1 is cut off and the IGBT 1 can be protected from an overcurrent. |
