| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve nonconformity that a protective circuit which utilizes a positive temperature coefficient thermistor repeats conduction and break, in a relatively short time. <P>SOLUTION: A semiconductor-switching element (Tr0), which performes operations of the conduction and breakage of a current passage from a power source 13 to a load, is controlled by an operation mode control circuit 12 which includes a first operation mode for shifting it from a conductive operation to break operation when the temperature of a temperature detection part rises and reaches a specified break temperature, making use of the resistance change of a first positive temperature coefficient thermistor (PTC1) and a second operation mode for shifting it from the break operation to the conductive operation when the temperature of the temperature detection part drops and reaches a recovery temperature (a temperature set to a temperature lower by a specified value than a blocking temperature), making use of the resistance change of a second positive temperature coefficient thermistor (PTC2), and it performs the control of the operation modes under a condition that both the positive temperature coefficient thermistors are thermally coupled with each other with respect to a temperature-detecting part. <P>COPYRIGHT: (C)2004,JPO |
