| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an LED lighting device which can maintain a constant LED current even when a power supply voltage fluctuates, and an LED bulb. <P>SOLUTION: The LED lighting device comprises a rectification circuit which rectifies a power supply voltage, a step-down chopper circuit which controls by PWM an LED current which flows in the LED upon receiving the output of the rectification circuit, a detection circuit which detects the switching current of the step-down chopper circuit, and a PWM control circuit which controls by PWM the step-down chopper circuit so as to maintain a detected switching current at a constant level. The PWM control circuit of this device includes a filter circuit which filters the output voltage of the current detection circuit, a reference voltage generation circuit which generates a reference voltage, a comparison drive circuit which determines an electric conduction period of the step-down chopper circuit according to the result of comparison between the output voltage of the filter circuit and the reference voltage, and a power supply voltage detection circuit which detects the power supply voltage. Here, the reference voltage generation circuit is configured so that, in a prescribed power supply voltage range, the reference voltage monotonously decreases relative to the power supply voltage which is detected by the power supply voltage detection circuit. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
