| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To control an output current to be constant against fluctuations in an output voltage. <P>SOLUTION: A step-up/down DC-DC converter 1 includes a step-down part 2 which has a step-down switch SW1 that receives a DC voltage from a DC power source and a choke coil L connected to the step-down switch SW1 and which outputs an output voltage Vout lower than the input voltage Vin to an LED 40, a step-up part 3 which has a step-up switch SW2 connected to the step-down switch SW1 via the choke coil L and outputs an output voltage Vout higher than the input voltage Vin to the LED 40, a constant current clamp switch 5 which controls a light source drive current Iout flowing to the LED 40 to be constant, and a control unit 6 which controls the step-down switch SW1, the step-up switch SW2, or the constant current clamp switch 5 according to the light source drive current Iout. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
