| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor light source drive device with high power efficiency, and capable of fast convergence of an average current flowing a semiconductor laser diode when an on-time ratio of PWM control is changed.SOLUTION: Between both terminals of a switching power supply 101, a series connection of a plurality of semiconductor laser diodes 102, an FET 103, and a current detection resister 104 are connected in series. The FET is driven on/off according to a PWM signal. A target value setting part 108 outputs a target average current value corresponding to inputted on-time ratio information, to a comparator 109. A low pass filter 110 averages a current flowing the semiconductor laser diode, detected with the current detection resister 104, and outputs the averaged current value to the comparator. The comparator compares the target average current value from the target value setting part and the average current value from the low pass filter, and provides a comparison result to a control end of the switching power supply as a control signal.SELECTED DRAWING: Figure 1 |
