| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply unit which includes a power factor improvement circuit with low noise and is capable of accommodating wide input voltage, with a simple circuit structure. SOLUTION: A choke coil for power factor improvement is formed by performing switching control, so that multiple coils provided in the power factor improvement circuit 3 may be connected in series or parallel corresponding to an inputted commercial AC voltage level. For example, when the inputted AC voltage is of 100 V system, two coils L1, L2 are connected in parallel to form the choke coil with small inductance value and large current capacity. When the AC voltage is of 200 V system, the two coils L1, L2 are connected in series to form the choke coil with large inductance value. |
