| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a power supply circuit for driving an LED, that suppresses heat generation of semiconductor devices and circuit devices even with its driving current being high. <P>SOLUTION: The power supply circuit for driving an LED includes: a full-wave rectifier 1 for performing full-wave rectification on a commercial alternating-current power supply voltage; a switching circuit 2 including a semiconductor switching element, whose input terminal is connected to an output side of the full-wave rectifier 1; a smoothing circuit 3 connected to an output terminal side of the switching circuit 2; an LED 4 as a load, connected to the smoothing circuit 3; a current limiter circuit 5 for keeping a current flowed through the LED 4 certain; a reference voltage production circuit 6 for producing a direct-current reference voltage from an output voltage of the full-wave rectifier 1; a voltage comparison circuit 7 for comparing an output voltage of the full-wave rectifier 1 with the reference voltage produced by the reference voltage production circuit 6; and a drive circuit 8 for turning on the switching circuit 2 when the output voltage of the full-wave rectifier 1, that has been compared with the reference voltage by the voltage comparison circuit 7, is lower than the reference voltage. The full-wave rectified voltage is shared by the switching circuit 2 and the current limiter circuit 5. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
