Converter transformer

Details Converter transformer Converter transformer

1998-08-03

2000-05-16

Gellner, Michael L.

Inductor devices

Windings

336170, 336180, 336185, 336198, 336199, H01F 2728

Patent

active

060642912

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a converter transformer for the switching power supply to be built in color television receivers, various display devices, video tape recorders and such other electronic appliances.


BACKGROUND OF THE INVENTION

The switching power supplies to be built in electronic appliances have been required to have a good noise characteristic, a high coupling for yielding a good output voltage characteristic, a low temperature-rise property and a high reliability, in addition to be compact, light in weight and efficient. A new technology has been requested for developing a converter transformer meeting the above requirements.
An example of conventional converter transformer is shown in FIG. 7 and FIG. 8, and other example in FIG. 9 and FIG. 10. FIG. 7 shows a cross sectional view cut into half, FIG. 8 is a connection diagram of windings. FIG. 9 shows a cross sectional view of other exemplary conventional converter transformer cut into half, FIG. 10 is a connection diagram of windings of the converter transformer.
In FIG. 7 and FIG. 8, a converter transformer comprises a inputting winding 1 (hereinafter referred to as primary winding) formed with split windings 1a and 1b for inputting a power supply, and output windings 3, 4, 5, 6, 7 (hereinafter referred to as secondary winding) for supplying electricity to load in the secondary side. The secondary windings 3 and 4 are main secondary windings for supplying major power to load in the secondary side, while the secondary windings 5, 6 and 7 are auxiliary secondary windings for supplying minor power to load in the secondary side. Contained further in the converter transformer includes, an output winding 2 (hereinafter referred to as primary sub-winding) for supplying electricity to a control IC in the primary side, a coil bobbin 8, an insulating material 11 provided between windings, and a magnetic core 10 made of a ferrite core.
A conventional converter transformer of this category is assembled with the split winding 1a of primary winding 1, the secondary windings 3-7, the split winding 1b and the primary sub-winding 2, each wound in the order around coil bobbin 8 with the insulating material 11 of 25 .mu.m or 50 .mu.m thick polyethylene terephtalate sticking tape in between the windings, and the magnetic core 10. The secondary windings 3, 4, 5, 6 and 7 are normally disposed between the split winding 1a and the split winding 1b, and the split winding 1a and the split winding 1b are connected in series.
In the above described conventional structure, a large encountering area may be provided between primary winding 1 and secondary windings 3-7, because each winding can share a large width; furthermore, the encountering distance between primary winding 1 and secondary windings 3-7 can be made very small as the insulation between windings is made with a thin film. As a result, the coupling between primary winding 1 and respective secondary windings 3, 4, 5, 6 and 7 may be raised to quite a high level, bringing about a high conversion efficiency with low temperature rise of a converter transformer.
Drawback with the conventional converter transformer includes that when the major output load, which is being supplied from main secondary windings 3 and 4, is varied the output voltage of auxiliary secondary windings 5, 6 and 7 makes a substantial fluctuation because of the high coupling with primary winding 1.
Further, the position of winding is easily displaced and the coupling is quite high in the conventional constitution, therefore a slight displacement of winding produces a substantial change in coupling, and shift in the output voltage. For example, if a protection circuit for overvoltage detection is contained in the output of primary sub-winding 2 the protection circuit readily makes an erroneous operation, because of the above described change in coupling.
Furthermore, there is a large stray capacitance existing between primary winding 1 and the whole secondary windings 3-7, and the impedance is small; as a result

REFERENCES:
patent: 3054976 (1962-09-01), Lipshutz
patent: 3652968 (1972-03-01), Johnston et al.
patent: 4229786 (1980-10-01), Mitani et al.
patent: 4500833 (1985-02-01), Napp et al.
patent: 4590453 (1986-05-01), Weissman
patent: 4635019 (1987-01-01), Akachi et al.
patent: 4639706 (1987-01-01), Shimizu
patent: 5530415 (1996-06-01), Takaya et al.
Japanese language search report for Int'l Appln No. PCT/JP97/04389 dated Mar. 10, 1998.
Form PCT/ISA/210.

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