| 摘要 |
A power supply device which converts a voltage by a switching method is connected to a load. Whether a current supplied from the power supply device to the load falls within a proper range is determined. At this time, while preventing an increase in cost in current detection and reducing Joule loss caused by an unwanted resistance component, it is determined that the current falls within the proper range. In order to determine a current supplied from a DC/DC converter to the load, a current determination unit (1) is arranged. The current determination unit (1) compares, with a preset voltage, a voltage obtained by DC-detecting a gate driving pulse signal used to turn on/off a switching MOS transistor (3), thereby determining whether the current flowing from the DC/DC converter to the load exceeds a predetermined current (proper range). In current detection, Joule loss by an unwanted resistance component can be reduced.
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