Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Induction-type discharge device load
Reexamination Certificate
2000-02-28
2001-06-12
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Induction-type discharge device load
C315S291000, C315S278000, C315SDIG004, C315S158000
Reexamination Certificate
active
06246183
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of The Invention
The present invention relates generally to electrodeless light sources and, more particularly, to a method and apparatus for dimming an electrodeless fluorescent light source.
2. Background Of The Related Art
This section is intended to introduce the reader to various aspects of art which may be related to various aspects of the present invention which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Conventional fluorescent lamps are driven with an electronic ballast which powers the lamps via electrodes disposed at each end of the lamp. The electrodes, however, are major life-limiting components of the fluorescent lamp. Electrodeless fluorescent lamps also are known. An electrodeless lamp is configured as a closed loop tube around which one or more coupling transformers are positioned. As with conventional fluorescent tubes, the electrodeless lamp is energized by an electronic ballast. However, rather than applying power to electrodes disposed at each end of a lamp tube, the ballast drives the coupling transformers, which, in turn, inductively couple the power to the lamp. The elimination of electrodes from the fluorescent lamp is particularly advantageous as it increases the life and reliability of the lamp and systems incorporating such lamps. Thus, electrodeless lamps are particularly useful in applications in which access to the lamps is restricted such that replacement of the lamps becomes difficult or expensive.
Backlit video display devices are one type of application in which the access to the lamp is not readily available. Such video displays may be found in computer systems, automatic teller machines, information kiosks, gas pumps, shipboard controls, etc. To enhance viewing of displayed images, such video displays commonly include a backlight source to provide a brightly lit background that contrasts with the displayed image. However, such video displays often are located in environments in which the ambient lighting conditions vary considerably, interfering with vivid viewing of the displayed image. For example, in a dimly lit environment (e.g., a cloudy day, the enclosed interior of a ship, etc.), a brightly lit background provides for the best viewing of a displayed image. However, in a brightly lit environment (e.g., a sunny day, a well-lit office, etc.), a dimly lit background provides for better viewing. Accordingly, it would be desirable to provide the capability to control the brightness of the backlighting to compensate for variations in ambient lighting to enhance the viewing capabilities of the video display unit further. Unfortunately, electrodeless lamps rarely are used in such displays due to the lack of suitable means for dimming such lamps.
The use of electrodeless fluorescent lamps is not limited to backlight sources for video display units or applications in which the lamp is not readily accessible. Electrodeless lamps also may be used in other types of applications requiring a light source, such as office or home lighting systems, desk lamps, etc. Moreover, if the control of the brightness of the light generated by the lamps in these other applications also is desirable, it would be advantageous to provide the capability to vary the brightness of the generated light in any type of lighting application in which an electrodeless fluorescent lamp is incorporated. Still further, it would be advantageous to provide a dimming module for electrodeless lamps that can be easily installed in existing electrodeless lighting systems to retrofit such systems with a brightness control capability
The present invention may address one or more of the problems set forth above.
SUMMARY OF THE INVENTION
Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
In accordance with one aspect of the present invention, a dimmable light source includes an electrodeless lamp to generate light, a ballast coupled to the lamp to energize the lamp, and a dimming circuit coupled to the lamp. The dimming circuit controls the amount of energy provided to the lamp to vary the brightness of the generated light.
In accordance with another aspect of the present invention, there is provided a dimming circuit for an electrodeless lamp that is inductively coupled to a coupling transformer. The coupling transformer provides electromagnetic energy to cause the lamp to generate light. The dimming circuit includes an auxiliary winding electromagnetically coupled to the coupling transformer, a switch coupled to the auxiliary winding, and a drive circuit coupled to the switch. The drive circuit is configured to transition the switch between a conductive state and a non-conductive state during a time interval to control the brightness of the generated light. During the conductive state, a current-carrying path is established through the auxiliary winding and the switch.
In accordance with still another aspect of the present invention, a dimmable display device includes an electrodeless lamp to generate light, a display unit to display an image and to use the light to enhance viewing of the image, and a dimming module coupled to the lamp. The dimming module controls the brightness of the generated light in response to a control signal, such as a signal representative of a detected amount of ambient light or a signal representative of a user-selected dimming setting.
In accordance with yet another aspect of the present invention, there is provided a method for dimming an electrodeless lamp. The method includes inductively coupling energy to an electrodeless lamp to energize the lamp and generate light and restricting the coupling of the energy during a first time interval of a repetitive time period to dim the generated light.
In accordance with a further aspect of the present invention, there is provided a method for making a dimmable electrodeless light source. The method includes providing an electrodeless lamp, attaching a coupling transformer to the lamp, and disposing an auxiliary winding on the coupling transformer. The method further includes coupling the auxiliary winding to a drive circuit that is configured to establish a current-carrying path through the auxiliary winding for a first time interval of a repetitive time period and to interrupt the current-carrying path through the auxiliary winding for a second time interval of the repetitive time period.
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OSRAM Sylvania Icetron Inductively Coupled Elcetrodeless Lighting System, Design Guide, Jul. 1998.
Fletcher Yoder & Van Someren
Litton Systems Inc.
Philogene Haissa
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