Patent ID: 7965523
Filing Date: 2011-06-21
Classification: H02M

Abstract:
1. A switching power supply device comprising: a first switch circuit defined by a parallel-connected circuit including a first switch element, a first diode, and a first capacitor; a second switch circuit defined by a parallel-connected circuit including a second switch element, a second diode, and a second capacitor; a third switch circuit defined by a parallel-connected circuit including a third switch element, a third diode, and a third capacitor; an input-side rectifier circuit including at least one rectifying element arranged to rectify an alternating input voltage; a fourth capacitor, to which a voltage rectified by the input-side rectifier circuit is applied; a transformer including at least a primary coil, a secondary coil, a first drive coil, and a second drive coil; a rectifying/smoothing circuit connected to the secondary coil; a first inductor connected in series with the primary coil; a second inductor connected such that a voltage of the fourth capacitor is applied to the second inductor during an on period of the third switch circuit that operates such that the on period of the third switch circuit is included in an on period of the first switch circuit; a fourth diode including an anode connected to one end of the second inductor and a cathode connected to one end of the second switch element so as to prevent a backward current from flowing to the second inductor; a fifth capacitor connected such that the fifth capacitor is charged with exciting energy stored in the second inductor and applies a voltage to a series circuit defined by the primary coil and the first inductor, during an on period of the first switch circuit; a sixth capacitor connected in parallel with the primary coil of the transformer and defining a series circuit including the second switch circuit; a first switching control circuit and a second switching control circuit arranged to alternately turn on or off the first and second switch elements with an intervening period during which both the first and second switch elements turn off; and a third switching control circuit arranged to turn on or off the third switch element; wherein each of the first switching control circuit and the third switching control circuit operates on a voltage generated at the first drive coil, and the second switching control circuit operates on a voltage generated at the second drive coil.