| 摘要 |
PROBLEM TO BE SOLVED: To provide an overcurrent detecting circuit capable of securely detecting an overcrrent using a voltage generated in the source side and the drain side of a current supply line based on on-resistance of a field effect transistor. SOLUTION: This overcurrent detecting circuit 100 includes the field effect transistor 1 disposed in the current supply line S, in which the source and the drain are connected to the current supply circuit S; and a comparator 3 for detecting the voltage of the current supply line S in a connecting point P4 of the source side and a connecting point P3 of the drain side of the field effect transistor 1, and outputting an overcurrent detection signal when the detected difference of the voltage is not less than a predetermined reference value. The current supply line S of the drain side is separated to mount a resistor R3 between them. An NTC thermistor 7 is mounted to the resistor R3 in parallel. The voltage generated by the resistor R3 mounted in parallel and the NTC thermistor 7 is applied to the comparator 3. The field effect transistor 1 is thermally coupled to the NTC thermistor 7. COPYRIGHT: (C)2007,JPO&INPIT
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