| 摘要 |
PROBLEM TO BE SOLVED: To provide an active filter and a switching power supply device, which make their composition simple and their size small and emit little noise. SOLUTION: An active filter 30 which is connected to a commercial AC power supply and is provided for a power factor improvement and a harmonics suppression has a rectifier circuit 12 which converts the commercial AC power supply to an undulating voltage, a piezoelectric transformer 33 and a driving circuit 32 which makes switching of the piezoelectric transformer 33. The active filter has a rectifier circuit 34 which rectifies the voltage outputted from the piezoelectric transformer 33, a smoothing circuit 35 which smoothes the output of the rectifier circuit 34, and a control circuit 37 which controls the driving circuit 32 by detecting this smoothed voltage. The output of the smoothing circuit 35 is connected to a DC/DC converter 40 of non-insulated step-down chopper type and the output of the DC/DC converter 40 is inputted to a load 42. |
