Transformer and dc-dc converter including same

A DC-DC converter comprising:

• a drive circuit;
• a transformer;
• and
• an output circuit, wherein
• the transformer comprises:
• a core unit having a body, a first outer leg extending from one side of the body in a first direction, a second outer leg extending from the-an other side of the body in the first direction, and a middle leg disposed between the first outer leg and the second outer leg, the middle leg extending from the body in the first direction;
• a secondary coil unit comprising a plurality of conductive plates stacked in the first direction so as to form turns around the middle leg;-and
• a primary coil unit comprising a first conductive wire wound so as to form turns around the first outer leg and a second conductive wire wound so as to form turns around the second outer leg;
• and
• a bobbin having a first through hole, through which the middle leg extends, a second through hole, through which the first outer leg extends, and a third through hole, through which the second outer leg extends, wherein
• the secondary coil unit comprises an upper coil unit disposed at an upper part of the bobbin and a lower coil unit disposed at a lower part of the bobbin,
• the bobbin provides a first receiving hole configured to receive the upper coil unit, a second receiving hole configured to receive the first conductive wire, a third receiving hole configured to receive the second conductive wire, and a fourth receiving hole configured to receive the lower coil unit,
• the first receiving hole is configured to expose upwards an upper surface of a conductive plate located at an uppermost end of the upper coil unit, and
• the fourth receiving hole is configured to expose downwards a lower surface of a conductive plate located at a lowermost end of the lower coil unit.