Transformer with controlled interwinding coupling and controlled leakage inductances and circuit using such transformer

(19)

(11)

EP 0 855 723 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	11.11.1998 Bulletin 1998/46

(43)	Date of publication A2:
	29.07.1998 Bulletin 1998/31

(21)	Application number: 98102797.2

(22)	Date of filing: 14.09.1992

(51)	International Patent Classification (IPC)⁶: H01F 27/34, H01F 27/36

(84)	Designated Contracting States:
	DE FR GB

(30)

Priority:

13.09.1991 US 759511

(62)	Application number of the earlier application in accordance with Art. 76 EPC:
	92308315.8 / 0532360

(71)	Applicant: VLT CORPORATION
	San Antonio, Texas 78230 (US)

(72)	Inventors:
	Vinciarelli, Patrizio Boston, Massachusetts 02114 (US) Prager, Jay M. Tyngsboro, Massachusetts 01879 (US)

(74)	Representative: Deans, Michael John Percy et al
	Lloyd Wise, Tregear & Co., Commonwealth House, 1-19 New Oxford Street London WC1A 1LW London WC1A 1LW (GB)


	Remarks:
	This application was filed on 18 - 02 - 1998 as a divisional application to the application mentioned under INID code 62.

(54)	Transformer with controlled interwinding coupling and controlled leakage inductances and circuit using such transformer

(57) A transformer in which a magnetic medium provides flux paths within the medium, two or more windings enclose the flux paths at separated locations along the paths, and an electrically conductive medium, arranged in the vicinity of the magnetic medium and the windings, defines a boundary within which flux emanation from the magnetic medium and the windings is confined and suppressed. In a transformer constructed in accordance with the present invention, both controlled values of leakage inductance and the benefits of separated windings can be achieved. The conductive medium can be configured to reduce the leakage inductance of a controlled-leakage inductance transformer (e.g. for use in a zero-current switching power converter), having separately located windings, by at least 25%, and can be configured to reduce the leakage inductance of a low-leakage inductance transformer (e.g. for use in a PWM power converter), having separately located windings, by at least 75%.

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