| 摘要 |
PROBLEM TO BE SOLVED: To provide a load control device that prevents generation of radiation/conduction noise and suppresses a variation in duty ratio even if a supply voltage varies across a predetermined value.SOLUTION: A first comparator 7 outputs a normally L level DC signal when a supply voltage VI is not more than a first predetermined value, and if the first predetermined value is exceeded, outputs a first pulse signal with a duty ratio increasing with increasing supply voltage VI. A second pulse signal output circuit 8 outputs a second pulse signal with a constant duty ratio if the supply voltage VI is not less than the first predetermined value, and stops outputting the second pulse signal when the supply voltage VI falls below a second predetermined value lower than the first predetermined value while the second pulse signal is output. An OR gate 9 selects one which has the longer H level period if the firs pulse signal and the second pulse signal are input and selects the second pulse signal if the DC signal and the second pulse signal are input, and uses the selected pulse signal for controlling on/off a FET. |
