| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a switching power supply device which can convert voltages between two DC power supplies, and can properly charge the two power supplies on the basis of an inputted AC voltage. <P>SOLUTION: When a main battery 10 is preferentially charged in the switching power supply device, an SW control part 6 controls a duty ratio of a switching operation at a switching circuit 51 so as to be constant, and controls a duty ratio of a switching operation at a bidirectional switching circuit 13 so as to be variable. On the other hand, when an auxiliary battery 30 is preferentially charged, the SW control part 6 controls the duty ratios of switching operations at the switching circuit 51 and the bidirectional switching circuit 13 so as to be variable. When the auxiliary battery 30 is preferentially charged, the duty ratio of the switching operation at the switching circuit 51 may be controlled so as to be constant, and the duty ratio of a switching operation by a switching element Q9 may be controlled so as to be variable. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
