| 摘要 |
<p>PROBLEM TO BE SOLVED: To detect the abnormality of a power supply system without monitoring a control signal outputted to a switching element in an electric load driving device for controlling the duty ratio of power supply to an electric load. SOLUTION: In the device for controlling the duty ratio of power supply to the electric load by outputting a control signal of a prescribed duty ratio from a CPU, turning on the switching element in accordance with the control signal from the CPU and allowing a current to flow into the load, a detection circuit different from the CPU outputs a binary detection signal SM showing whether the load is in a conductive state or a non-conductive state to the CPU. The CPU reads out the level of the detection signal for every period sufficiently shorter than the period of the control signal (S110), respectively measures practical power supply continuation time to the electric load and non-power supply continuation time as the values of respective counters CL, CH (S120, S150), and when each measured value exceeds a decision value, decides the occurrence of abnormality (YES in S130 or S160).</p> |
