Composite transformer and power converter using same

1. A composite transformer comprising first and second windings which generate magnetic fluxes when excited and which are wound to form a first inductor, a second inductor, and a transformer, the composite transformer further comprising:

a transformer core including a core leg around which a portion of the first winding and a portion of the second winding are wound, and a base fixing the core leg thereof;

a first inductor core including a core leg around which another portion of the first winding is wound, and a base fixing the core leg thereof; and

a second inductor core including a core leg around which another part of the second winding is wound, and a base fixing the core leg thereof, wherein:

the first winding and the second winding are wound in such directions that magnetic fluxes generated by the first and second windings are cancelled with each other; and wherein

the first winding and the second winding are wound around the core leg of the transformer core so as to be alternately overlapped with each other, and are respectively wound around the core leg of the first inductor core and the core leg of the second inductor so as to be apart from each other to suppress interference of the magnetic fluxes generated by the first and second windings.

2. The composite transformer according to claim 1 , wherein the first and second windings have the same winding length.

3. The composite transformer according to claim 2 , wherein the first and second windings have the same width.

4. The composite transformer according to claim 1 , wherein the transformer core comprises divisional core pieces and the divisional core pieces are symmetrical relative to a divisional plane.

5. A power converter comprising the composite transformer according to claim 1 , the power converter comprising:

first and second input/output terminals, the first input/output terminal comprising a first positive terminal and a common reference terminal that is a negative terminal, the second input/output terminal comprising a second positive terminal and the common reference terminal, the first positive terminal of the first input/output terminal being connected to one ends of the first winding and the second winding;

a first switching device including one end connected to another end of the first winding, and another end connected to the common reference terminal;

a second switching device including one end connected to another end of the first winding, and another end connected to the second positive terminal of the second input/output terminal;

a third switching device including one end connected to another end of the second winding, and another end connected to the common reference terminal; and

a fourth switching device including one end connected to another end of the second winding, and another end connected to the second positive terminal.

6. A power converter including the composite transformer according to claim 1 , the power converter comprising:

input and output terminals, the input terminal comprising a first positive terminal and a common reference terminal that is a negative terminal, the output terminal comprising a second positive terminal and the common reference terminal, the first positive terminal of the input terminal being connected to one ends of the first winding and the second winding;

a first switching device including one end connected to another end of the first winding, and another end connected to the common reference terminal;

a first diode which includes one end connected to another end of the first winding, and another end connected to the second positive terminal of the output terminal, wherein a forward direction of the first diode is from another end of the first winding toward the second positive terminal;

a second switching device including one end connected to another end of the second winding, and another end connected to the common reference terminal; and

a second diode which includes one end connected to another end of the second winding, and another end connected to the second positive terminal, wherein a forward direction of the second diode is from another end of the second winding toward the second positive terminal.

7. A power converter comprising the composite transformer according to claim 1 , the power converter comprising:

input and output terminals, the output terminal comprising a first positive terminal and a common reference terminal that is a negative terminal, the input terminal comprising a second positive terminal and the common reference terminal, the first positive terminal of the output terminal being connected to one ends of the first winding and the second winding;

a first diode which includes one end connected to another end of the first winding, and another end connected to the common reference terminal, wherein a forward direction of the first diode is from the common reference terminal toward another end of the first winding;

a first switching device including one end connected to another end of the first winding, and another end connected to the second positive terminal of the input terminal;

a second diode which includes one end connected to another end of the second winding, and another end connected to the common reference terminal, wherein a forward direction of the second diode is from the common reference terminal toward another end of the second winding; and

a second switching device including one end connected to another end of the second winding, and another end connected to the second positive terminal.

8. The power converter according to claim 5 , wherein each of the switching devices comprises an IGBT.

9. The power converter according to claim 5 , wherein each of the switching devices comprises a MOSFET.