| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To suppress fluctuations of light output due to the fluctuations of the power supply and the fluctuations of the forward direction voltage of the LED with a simple circuit structure in a lighting device which lights a plurality of LEDs using a power source having a large fluctuation range such as a battery. <P>SOLUTION: This is a lighting device in which a switching element Tr1, an LED unit in which a plurality of LEDs are connected in series, and a resistor R12 are connected in series to the DC power source Vdc. The switching element Tr1 is turned on and off so that the integrated value of the current flowing in the LED unit may be constant. When the power source voltage fluctuates and the peak current flowing in the LED increases, the voltage drop of the resistor R12 becomes large, and the charge of the integrating circuit made of a resistor R11 and a capacitor C2 becomes quick, thereby the ON duty of the transistor Tr1 becomes short, and the increase of the average current is suppressed. <P>COPYRIGHT: (C)2004,JPO</p> |
