| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply unit which allows the reduction of loss owing to a forward voltage of a diode for reverse current prevention while preventing DC current from reversely flowing to a step-down chopper circuit by means of the diode for reverse current prevention. <P>SOLUTION: The power supply unit comprises: a solar battery 1; a step-down DC/DC circuit 2; a first diode 3 for reverse current prevention; an AC power source 5; an AC/DC circuit 6; and a second diode 7 for reverse current prevention. The power supply unit selectively executes first and second modes. In the first mode, the step-down DC/DC circuit 2 performs voltage conversion of a DC voltage supplied from the solar battery 1 and provides the resultant voltage to a load through the first diode 3 for reverse current prevention. In the second mode, the AC/DC circuit 6 converts an AC voltage supplied from the AC power source 5 into a DC voltage, and provides the DC voltage to the load through the second diode 7 for reverse current prevention. The power supply unit further comprises: an FET 11 which is connected in parallel with the first diode 3 for reverse current prevention, and has on-resistance smaller than the forward resistance of the first diode 3 for reverse current prevention; and an FET control circuit 12 which turns on the FET 11 on sensing the activation of the step-down DC/DC circuit 2, and turns off the FET 11 on sensing the operation stop of the step-down DC/DC circuit 2. <P>COPYRIGHT: (C)2012,JPO&INPIT |
