| 摘要 |
PROBLEM TO BE SOLVED: To correctly count the number of times of self-interruption due to heat generation of a MOSFET with a heat interruption circuit built in. SOLUTION: This semiconductor relay system supplies electric power to a load by an ON/OFF control which is conducted by applying charge pump output voltage obtained by stepping up power supply voltage with a charge pump circuit, by means of a microcomputer to the gate of a MOSFET with a heat interruption circuit built in through a driving circuit. The current supplied to the load is detected and, if it is larger than a reference set value higher than a rated current value, a driving circuit is controlled to cut off the voltage applied to the gate of the MOSFET for stopping power supply to the load. When the source voltage occurring on the source side of the MOSFET is detected and a command signal to turn on the MOSFET is outputted from the microcomputer, the number of times when the source voltage occurring on the source side of the MOSFET is lower than the reference voltage value is counted and, if the count reaches the preset number of times, the semiconductor relay system is turned off to prevent generation of resetting.
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