| 摘要 |
PURPOSE: To reduce response time by composing a first PTC device to be changed into a high resistance condition at lower temperatures than a second PTC device, and changing the first PTC device into the high resistance condition. CONSTITUTION: A heater PTC device 24 is disposed to form a heat exchange relation with a protective PTC device 20. A switching temperature of the heater PTC device 24 is higher than a normal ambient temperature, and lower than a switching temperature of the protective PTC device 20. The heater PTC device 24 has a substantially higher initial resistance than the protective PTC device 20. Every time a circuit is energized, the device is changed into a high resistance condition, and heat is transmitted from the heater PTC device 24 to the protective PTC device 20. Response time can thus be reduced, thereby effects of changing ambient temperature conditions on the response time can be reduced. |
