| 主权项 |
1. A switching power-supply apparatus comprising:
a direct-current power-supply input unit arranged to input a direct-current input voltage; a transformer including at least a first primary coil, a first secondary coil, and a second secondary coil; a half-bridge primary-side power converter circuit that includes a first series circuit connected to both ends of the direct-current power-supply input unit and including a first switch circuit that includes a first switching element, a first capacitor, and a first diode connected in parallel with one another, and a second switch circuit that includes a second switching element, a second capacitor, and a second diode connected in parallel with one another, and both ends of a second series circuit including at least a first input inductor, the first primary coil and an input capacitor being connected to both ends of the first switch circuit or the second switch circuit; a secondary-side synchronous rectifier circuit including a third switch circuit arranged to rectify a voltage generated by the first secondary coil and including a third switching element, a third capacitor, and a third diode connected in parallel with one another, and a fourth switch circuit arranged to rectify a voltage generated by the second secondary coil and including a fourth switching element, a fourth capacitor, and a fourth diode connected in parallel with one another, the secondary-side synchronous rectifier circuit being arranged to operate due to switching operations of the third switch circuit and the fourth switch circuit being controlled in accordance with complementary switching operations of the first switch circuit and the second switch circuit; a first inductor arranged so as to smooth currents flowing in the first secondary coil and the second secondary coil; and a smoothing capacitor connected downstream from the first inductor; wherein a load is connected downstream from the smoothing capacitor; the first switch circuit and the second switch circuit are arranged to perform mutually complementary switching operations before and after a predetermined dead time and to control an on time ratio of an on time of the first switching element to an on time of the second switching element to control power supplied to the load, regardless of a length of the predetermined dead time; when the load is a light load, an operation mode is performed in which energy is regenerated from the secondary side to the primary side by causing a negative current to flow in a direction opposite to a rectification direction in at least one of the third switching element and the fourth switching element; the negative current is provided by the smoothing capacitor; an output voltage of the switching power supply apparatus is controlled by the negative current when the load is a light load, such that the power supply apparatus does not operate in a current discontinuous mode; and when the load is a light load, the output voltage is linearly controlled by controlling the on time ratio. |
