| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a switching power supply unit that can improve power supply efficiency. <P>SOLUTION: A load state is determined by a load state determining circuit 25 based on a pulse signal for making a second switching element 8 subjected to on/off-control. A PFC on/off switching circuit 24 stops the operation of a power factor improvement converter 26 when it is determined that the load state is a light load state that is lighter than a specified load state. When it is determined that the load state is a heavy load state that is heavier than the specified load state, the operation of the power factor improvement converter 26 is activated. <P>COPYRIGHT: (C)2003,JPO |
