PURPOSE: To securely detect power source abnormality and to prevent a power semiconductor element from breaking by providing a voltage detecting circuit which sends out its output in three stages and specific integration circuits which are connected with respective outputs.
CONSTITUTION: The voltage detecting circuit 7 detects a power source input and sends out three stages of outputs High, Mid, and Low as the detected voltage. Further, the 1st and 2nd integration circuits 8 and 9 are connected to the High and Low outputs of the voltage detecting circuit 7 and the 3rd integration time 10 which has a smaller time constant than the 1st and 2nd integration circuits 8 and 9 is connected to the Mid output. Therefore, only the 3rd integration circuit 10 varies abruptly in case of the power source abnormality, and the output of the 3rd integration circuit 10 becomes larger than the output 8 of the 1st integration circuit in case of a lightning surge and below the output of the 2nd integration circuit 9 in case of an instantaneous power failure, so that they are protected by the outputs of 1st and 2nd comparators 11 and 12 respectively. Consequently, the power semiconductor element is securely protected in case of the power failure abnormality and prevented from breaking.
OGATA HIDEO
HAGIMOTO TAKEO
KOMINAMI HIDEYUKI
OMORI HIDEKI
MATSUSHITA ELECTRIC IND CO LTD
| JPS61296677A | 1986-12-27 | |||
| JPS61227678A | 1986-10-09 |
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