Switching power unit having switching controller controlling PFC voltage by changing on-duty of first and second switching elements

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, and also controls the output voltages by changing switching frequencies of the full-bridge circuit based on output signals from the PFC voltage detector and the output voltage detector, respectively, and
• the power-factor improvement unit comprises:
• a series circuit of first and second diodes connected in parallel with the series circuit of the first and second switching elements in a forward direction;
• a booster inductor and an AC source connected in series at an intermediate portion between both of the series circuits;
• and the first smoothing capacitor connected at both ends of the series circuit of the first and second diodes so as to be placed in parallel to the first and second switching elements,
• the switching power unit further comprising a polar detector that is connected in parallel with the AC source where the first switching element is arranged on a high-voltage side while the second switching element is arrange on a low-voltage side,
• wherein the polar detector detects a voltage of at least one side of the AC source so as to detect polarity of the AC source and to output the detected result to the switching controller,
• the switching controller sets on-duty of the second switching element to 50% or less in case that the intermediate point side of the first and the second switching elements of the AC source is a positive polarity, and
• the switching controller sets on-duty of the first switching element to 50% or less in case that the intermediate point side of the first and second diodes of the AC source is a positive polarity.

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, and also controls the output voltages by changing switching frequencies of the full-bridge circuit based on output signals from the PFC voltage detector and the output voltage detector, respectively,
• the switching controller is arranged on the secondary side of the high-frequency transformer;
• output signals from the PFC voltage detector on the primary side is transmitted to the switching controller on the secondary side through a second insulation means;
• and switching controlled signals output from the switching controller are transmitted to the first to fourth switching elements on the primary side through a third insulation means based on output signals from the output voltage detector on the secondary side, and based on output signals from the second insulation means, and
• output signals from the polar detector are transmitted to the switching controller on the secondary side through a fourth insulation means.