Patent ID: 8526201

Claim:
A switching power unit comprising a full-bridge type AC/DC converter circuit structured in combination with a power-factor improvement unit and a current resonance converter unit, the power-factor improvement unit and the current resonance converter unit sharing first and second switching elements, the switching power unit including: a PFC voltage detector that is provided in the power-factor improvement unit and that detects PFC voltages stored in a first smoothing capacitor connected in parallel with a series circuit of the first and second switching elements; an output voltage detector that is provided in the current resonance converter unit and that detects DC output voltages stored in a second smoothing capacitor on a secondary side through a high-frequency transformer based on high-frequency voltages obtained by ON-and-OFF operations of a full-bridge circuit on a primary side, the full-bridge circuit being structured as that the first and second switching elements are connected in parallel with third and fourth switching elements; and a switching controller into which output signals from the PFC voltage detector and output signals from the output voltage detector are input so as to control ON-and-OFF operations of the first to fourth switching elements, wherein the switching controller controls the PFC voltage by changing on-duty of the first and second switching elements based on output signals from the PFC voltage detector, and also controls the output voltages by changing switching frequencies of the first to fourth switching elements based on output signals from the output voltage detector, the first and the second switching elements both being adapted to change the on-duty and the switching frequencies at the same time.