| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To improve an LED drive circuit by shortening a non-lighting period or eliminating the period using a capacitor of smallest possible capacitance, thereby stabilizing a THD, the LED drive circuit turning on an LED array by rectifying an AC power supply. <P>SOLUTION: A current supply circuit 2 which supplies a current to a light-emitting circuit 3 when a rectification circuit is cut off has a discharge-time constant longer than a charge-time constant. The light-emitting circuit 3 comprises an LED array 4a and a constant current circuit 5. The constant current circuit 5 includes an LED array 4b. When a voltage (absolute value) of a commercial AC power supply is high, 4a and 4b are turned on. When the voltage (absolute value) of the commercial AC power supply is near the sum of the first LED array 4a and the LED array 4b threshold, the constant current circuit 5 is operated, and the LED array 4a is turned on with a constant current, and the LED array 4b are gradually turned off. When the voltage further decreases, only the LED 4a remains on. <P>COPYRIGHT: (C)2012,JPO&INPIT</p> |
