Insulation type step-down converter

An insulation type step-down converter comprising first and second step-down transformers aligned with each other,

• the first step-down transformer including
• a first core including a first middle leg, a first one outer leg spaced from the first middle leg and arranged to extend in a direction identical to the first middle leg, and a first other outer leg spaced from the first middle leg opposite to the first one outer leg,
• a first input-side coil wound around the first middle leg of the first core, and
• first and second output-side coils wound around the first middle leg of the first core, overlapping at least part of the first input-side coil and spaced from each other,
• the second step-down transformer including
• a second core including a second middle leg, a second one outer leg spaced from the second middle leg and arranged to extend in a direction identical to the second middle leg, and a second other outer leg spaced from the second middle leg opposite to the second one outer leg,
• a second input-side coil wound around the second middle leg of the second core, and
• third and fourth output-side coils wound around the second middle leg of the second core, overlapping at least part of the second input-side coil and spaced from each other,
• the insulation type step-down converter further comprising:
• a first rectifier element connected in series with the first output-side coil;
• a second rectifier element connected in series with the second output-side coil;
• a third rectifier element connected in series with the third output-side coil;
• a fourth rectifier element connected in series with the fourth output-side coil;
• and
• first and second smoothing coils each connected to two of the serial connections between the first to fourth output-side coils and the first to fourth rectifier elements,
• the first output-side coil includes a first end connected to a reference potential and a second end located opposite to the first end and connected to the first rectifier element, the second output-side coil includes a first end connected to the reference potential and a second end located opposite to the first end and connected to the second rectifier element, the third output-side coil includes a first end connected to the reference potential and a second end located opposite to the first end and connected to the third rectifier element, the fourth output-side coil includes a first end connected to the reference potential and a second end located opposite to the first end and connected to the fourth rectifier element, and each of the first, second, third and fourth output-side coils has an intermediate portion at a part of a path from the first end toward the second end,
• the intermediate portion of the first output-side coil and the intermediate portion of the third output-side coil being connected to each other,
• the intermediate portion of the second output-side coil and the intermediate portion of the fourth output-side coil being connected to each other,
• the first, second, third, and fourth rectifier elements being connected such that electric currents flow simultaneously in the first output-side coil and the third output-side coil, and electric currents flow simultaneously in the second output-side coil and the fourth output-side coil in a manner alternating with the electric currents in the first output-side coil and the third output-side coil, so as to cancel out magnetic fluxes passing through the middle legs each time when electric current flowing in the first and second input-side coils is changed in direction.