| 摘要 |
In a power supply circuit for performing PAM control by using a switching element, the ripple voltage of a capacitor in a smoothing circuit is prevented from increasing and the size and cost of the capacitor are reduced. The power supply circuit comprises a bridge circuit (12) of diodes (D1 to D4) for rectifying alternating-current power, a smoothing circuit (13) having two capacitors (C1, C2) connected in series and connected to the output side of the bridge circuit (12), and a PAM controller (15) for switching a switching element (S) at a predetermined timing. The PAM controller (15) includes a phase difference detecting section (15d) for detecting a phase shift of a PAM waveform on the basis of a change in the voltage difference between the two capacitors (C1, C2) and a phase correcting section (15e) for correcting the phase of the PAM waveform so that an input current approximates a sine wave. |
