Electricity: electrical systems and devices – Safety and protection of systems and devices – Transformer protection
Reexamination Certificate
1997-12-30
2001-07-17
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Transformer protection
C361S056000, C361S111000
Reexamination Certificate
active
06262870
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a transformer shielded with a short ring, and more particularly to suppression of electrostatic interference from a transformer with a short ring by electrical connection of the short ring to a predetermined potential through a discharge path.
When a transformer is used in an electronic circuit or system, it is known to reduce or eliminate leakage flux from the transformer by use of a short ring. In this regard, a short ring is a closed, annular ring of electrically conductive material (or soft magnetic material) that girds the transformer, on the outside of the transformer's windings and core. The purpose of the short ring is to shield nearby components from magnetic flux that leaks from the transformer's windings and core. For example, in a color television (CTV) system, use of a short ring in a switching power supply can reduce or eliminate 60 Hz “hum” from the audio and video portions of TV programming.
While a short ring can effectively suppress or eliminate electromagnetic interference, its structure and operation, and/or the structure and operation of a transformer shielded by the short ring, can produce an electrical potential that may capacitatively discharge to adjacent components, causing electrostatic disruption of the components.
SUMMARY OF THE INVENTION
The problem is solved by the inventor's critical realization that the charge induced in at least one short ring of a multi-winding transformer can be safely and effectively discharged by provision of an electrically conductive discharge path from the short ring to a predetermined potential. Preferably, the predetermined potential is a ground to which one side of the transformer is referenced. Alternatively, the predetermined potential may be a drive signal in response to which the transformer operates.
The inventor has further realized that, for a transformer having at least one Faraday shield, as well as at least one short ring, both the Faraday shield and the short ring can be connected through one or more electrical discharge paths to the predetermined potential.
Accordingly, an objective of this invention is to provide to a transformer that has at least one short ring with an electrically conductive discharge path between the at least one short ring and a predetermined potential.
Achievement of this objective provides the unexpected benefit of suppression or elimination of electrostatic and electromagnetic interference caused by the operation of a multi-winding transformer having at least one short ring.
Achievement of these and other objectives and advantages by this invention will be evident when the following detailed description is read with reference to the below-described drawings.
REFERENCES:
patent: 4475097 (1984-10-01), Kikuchi
patent: 4540967 (1985-09-01), Chitose
patent: 5150046 (1992-09-01), Lim
patent: 5248938 (1993-09-01), Kobayashi et al.
patent: 5548254 (1996-08-01), Ueno et al.
patent: 5684446 (1997-11-01), Adkins et al.
Gray Cary Ware & Freidenrich
Jackson Stephen W.
Matsushita Electric Corporation of America
LandOfFree
Suppression of electrostatic interference from a transformer... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Suppression of electrostatic interference from a transformer..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Suppression of electrostatic interference from a transformer... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2469532