| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply used for an image forming device, allowing the abnormality details to be minutely detected. SOLUTION: The switching power unit compares a value detected by an output voltage detector circuit VSEN11 of a first power supply circuit for 5 V output voltage 10 with both a first upper limit threshold and a first lower limit threshold, processes setting of a PWM pulse output to be 0% if the value falls beyond the range of the first upper/lower limit thresholds, and suspends the power supply operation to stop all outputs. Next, it writes the data indicating abnormality in a critical region at 5 V output voltage into a nonvolatile memory 12. Then compares the detected value with both a second upper limit threshold lower than the first upper limit threshold and a second lower limit threshold higher than the first lower limit threshold, if the value falls beyond the range of the second upper/lower limit thresholds, also writes the data indicating abnormality in a critical region at 5 V output voltage into a nonvolatile memory 12. The read digital data will be used for update operations of PWM pulse ON duty, when being within the range of upper/lower limit thresholds. |
