| 摘要 |
PROBLEM TO BE SOLVED: To improve the detection accuracy of abnormality, such as the overload, etc., and also to improve the resistance to the noise interference by converting the change of an extracted load current into a current change voltage signal and comparing this voltage signal with a prescribed reference voltage to output a comparison signal. SOLUTION: A comparator 7 compares the detection voltage V1 with the reference voltage V0 and outputs a comparison signal S1, in response to the difference between the V1 and V0. The shape of each element and a circuit constant are set, so that the V1 is equal to the V0, when the load current IL of its upper limit value flows into the load Z2. Thus, the relation of values between the V1 and V0 is inverted between a normal state is which the current IL is smaller than its set upper limit value and an overload state where the current IL exceeds its set upper limit value. As a result, the output level of the signal S1 has a large change, and the state of an FET 1 is detected. Furthermore, the influence of the current error caused at a current mirror circuit can be reduced, since this circuit has a single stage. |
