| 摘要 |
PROBLEM TO BE SOLVED: To obtain an overheat protective circuit which is kept free from malfunctions caused by noises and capable of surely preventing a semiconductor element which supplies a current to and electric loading from being damaged by heat. SOLUTION: An overheat protective circuit for protecting an IGBT 1, which supplies a current to a load against thermal damage, is equipped with a temperature detecting element 3 which generates a signal V0 corresponding to the temperature of the IGBT 1, a comparator 13 and a delay circuit 15 which causes the IGBT 1 to turn off when they detect that the IGBT 1 is kept at a temperature higher than a first temperature T1 (rated temperature of IGBT 1) for a prescribed time resting on the signal V0 sent from the temperature detecting element 3, and a comparator 17 which cauges the IGBT 1 to turn off instantaneously, when it detects resting on the signal V0 that the temperature of the IGBT 1 is higher than the temperature T1 and becomes higher than a second temperature T2, which is set lower than a certain temperature at which the IGBT 1 becomes uncontrollable. Therefore, an overheat protective circuit is kept free of malfunctions caused by noises and protecting an IGBT 1 against overheat, when a load is short-circuited.
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