Abstract: A switching power supply apparatus includes a first commutation inductor which is provided in a path of current flowing from a power supply input unit through a first switching circuit and an inductor during an ON period of a first switching circuit, and a second commutation inductor provided in a path of current flowing through the inductor during an OFF period of the first switching circuit. The first and second commutation inductors and the inductor are connected to a first junction point. One end of a clamping series circuit, which includes a second switching circuit and a series capacitor connected in series, is connected to a second junction point, which connects the first commutation inductor and the first switching circuit, and the other end thereof is connected so that the first and second commutation inductors and the series capacitor constitute a resonance circuit. Accordingly, first and second switching elements can be turned on at a zero voltage.

Abstract: A switching power supply apparatus includes a first commutation inductor which is provided in a path of current flowing from a power supply input unit through a first switching circuit and an inductor during an ON period of a first switching circuit, and a second commutation inductor provided in a path of current flowing through the inductor during an OFF period of the first switching circuit. The first and second commutation inductors and the inductor are connected to a first junction point. One end of a clamping series circuit, which includes a second switching circuit and a series capacitor connected in series, is connected to a second junction point, which connects the first commutation inductor and the first switching circuit, and the other end thereof is connected so that the first and second commutation inductors and the series capacitor constitute a resonance circuit. Accordingly, first and second switching elements can be turned on at a zero voltage.

Abstract: A transformer including a first magnetic core and a second magnetic core having the shape of a flat plate. In the first magnetic core, a middle leg and substantially L-shaped outer legs whose inner sides are formed as circular-arc-shaped surfaces are provided in a standing manner at the central portion and at the comers of a rectangular flat plate, respectively. In addition, in the first magnetic core, a winding accommodating portion is formed between the circular-arc-shaped surfaces of the corresponding outer legs and an outer peripheral surface of the middle leg. Three coil portions, formed by spiral winding operations in level states, are placed upon each other, and are inserted into the winding accommodating portion of the first magnetic core. Then, from above the coil portions, the second magnetic core is placed thereon in order to form an integral structure.

Abstract: A transformer comprises first and second flat coils stacked with each other. Each of first and second flat coils comprises a conductive wire which is wound in a flat spiral shape having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively. The inner end of the first flat coil passes through the through hole of the second flat coil, thus reducing the overall thickness of the transformer because both inner ends pass over only one flat coil.

Abstract: A transformer including a first magnetic core and a second magnetic core having the shape of a flat plate. In the first magnetic core, a middle leg and substantially L-shaped outer legs whose inner sides are formed as circular-arc-shaped surfaces are provided in a standing manner at the central portion and at the comers of a rectangular flat plate, respectively. In addition, in the first magnetic core, a winding accommodating portion is formed between the circular-arc-shaped surfaces of the corresponding outer legs and an outer peripheral surface of the middle leg.