Insulating transformer and power conversion device

1. An insulating transformer, comprising:

a semiconductor substrate;

an insulating substrate which overlies only a portion of the semiconductor substrate so that the semiconductor substrate extends laterally beyond the insulating substrate;

a primary winding provided on one of the semiconductor substrate and the insulating substrate;

a secondary winding provided on the other of the semiconductor substrate and the insulating substrate, the primary winding and the secondary winding being arranged to face each other;

an electrode pattern disposed on a portion of the semiconductor substrate extending laterally from the insulating substrate, the electrode pattern being connected to the primary winding or the secondary winding formed on the semiconductor substrate; and

an insulating spacer layer provided in between the semiconductor substrate and the insulating substrate for insulating and separating the primary winding and the secondary winding, the insulating spacer layer being non-perforate and free of electrical conductors passing therethrough and maintaining a constant interval between the semiconductor substrate and the insulating substrate.

2. An insulating transformer according to claim 1 , further comprising:

a penetrating hole formed exclusively in the insulating substrate; and

an electrode formed on a face opposite to another face of the insulating substrate on which the primary winding or secondary winding is formed and which is connected to the primary winding or secondary winding via the penetrating hole so that a wire is connected to the electrode.

3. An insulating transformer according to claim 1 , wherein the insulating spacer layer is an organic insulating layer in a form of a film.

4. An insulating transformer according to claim 3 , wherein the organic insulating layer is a polyimide layer.

5. An insulating transformer according to claim 1 , wherein the insulating substrate has a relative permittivity higher than that of the insulating spacer layer.

6. An insulating transformer according to claim 1 , further comprising an insulating film formed on an under surface of the insulating spacer layer such that the primary winding or the secondary winding is covered.

7. A power conversion device, comprising:

a pair of switching elements connected in series for operating as an upper arm and a lower arm, respectively, and conducting and blocking current flowing into a load;

a control circuit for generating control signals to direct the switching elements to become conductive or non-conductive;

a driving circuit for driving control terminals of the switching elements based on the control signals; and

the insulating transformer according to claim 1 .

8. A power conversion device according to claim 7 , wherein the insulating layer is in a film form.

9. An insulating transformer according to claim 1 , further comprising a lead wire layer formed in the semiconductor substrate and connecting the electrode pattern and the primary winding or the secondary winding formed on the semiconductor substrate.

10. An insulating transformer according to claim 9 , wherein the electrode pattern is exposed on the semiconductor substrate without being covered by the insulating substrate.

11. An insulating transformer according to claim 10 , further comprising an adhesive layer between the semiconductor substrate and the insulating substrate.

12. An insulating transformer according to claim 11 , wherein the adhesive layer is disposed directly on a surface of the insulating spacer layer.