| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a bulb-type LED lamp for preventing thermal failure caused by overheating of LEDs and of a transistor. <P>SOLUTION: An overheat protecting resistor R2 whose resistance value increases/decreases in response to increase/decrease of the temperature in a temperature range greater than or equal to the Curie temperature thereof is connected to series-connected LEDs 22 that are connected to the positive-side terminal T1 of a full-wave rectification element REC. The collector terminal C of a transistor Tr is connected to the overheat protecting resistor R2; the emitter terminal E of the same is connected to a current-detecting resistor R3; and the base terminal B of the same is connected to a constant-voltage circuit 21. When at least one of the LEDs 22 or the transistor Tr is shorted by failure, the resistance value of the overheat protecting resistor R2 increases in association with overheating of the transistor Tr caused by the increase of the voltage applied to the transistor Tr or in association with overheating of the LEDs 22 caused by the increase of the load current flowing through the LEDs 22, and suppresses the voltage applied to the transistor Tr or the load current flowing through the LEDs 22. Thereby, thermal failure caused by overheating of the LEDs 22 and of the transistor Tr is prevented. <P>COPYRIGHT: (C)2010,JPO&INPIT |
