| 摘要 |
PROBLEM TO BE SOLVED: To provide an LED driving device and an illuminating device using the same capable of modulating the light while preventing color variation of an LED with a simple circuit.SOLUTION: The LED driving device comprises a boosting circuit 1 connected to a DC power supply DC1 to output an intermediate voltage VC1; a step-down circuit 2 connected to a light source 3 having plural LEDs 30 to step down the intermediate voltage VC1 to a load voltage V2 to output the same to a light source 3; a main control circuit 4 that controls the boosting circuit 1 and the step-down circuit 2; and a modulation control circuit 5 that controls the main control circuit 4 to modulate the light source 3 based on the modulation ratio of the light source 3 which is set from the outside. The step-down circuit 2 has a switching element Q2, and the main control circuit 4 performs a PWM control on the switching element Q2 in the step-down circuit 3 at a low-frequency, switches the operation of the boosting circuit 1 or the step-down circuit 2 between the case when the input voltage V1 is smaller than the output voltage V2 and the case when the input voltage V1 is larger than the output voltage V2, thereby modulating the light source 3. |
