| 摘要 |
PROBLEM TO BE SOLVED: To prevent chattering of a detection signal although a hysteresis operation is not stably performed in a monitoring circuit when direct voltage moves up and down with respect to a set value in a short time in monitoring the direct voltage applied to a driving circuit of a semiconductor element with the hysteresis operation. SOLUTION: A comparison circuit 4 comprises a schmidt buffer 4a having a first and second thresholds, and a buffer 4b having a threshold larger than the first threshold and smaller than the second threshold. An integrating circuit 3 and the comparison circuit 4 function as a timer circuit based on three value comparison. The input signal IN decreases from a reference voltage signal V6, a control signal becomes an H level with the passage of time determined with the time constant of the integrating circuit 3 and the threshold of the buffer 4b, and further a detection signal FO is outputted with the passage of time (≥response time of the circuit 4) corresponding to the difference between the second threshold and the above-mentioned threshold. COPYRIGHT: (C)2006,JPO&NCIPI
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