Dimmable electrodeless light source
AssigneeLitton Systems, Inc.
InventorCarl E. Buonavita
Life of this patent
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Abstract
A dimmable electrodeless light source includes an electrodeless lamp, an electronic ballast and a dimming module. The light source further includes coupling transformers coupled to the electrodeless lamp for inductively coupling power to the lamp to generate light. An auxiliary winding electromagnetically coupled to the primary winding of at least one of the coupling transformers is driven by switching circuitry in the dimming module. The switching circuitry is pulse width modulated to control the average brightness of the light generated by the electrodeless lamp. An exemplary application for the dimmable electrodeless light source is as a backlight for a video display device, such as an liquid crystal display unit.
Claims33
A dimmable light source, comprising:
- an electrodeless lamp to generate light;
- a ballast coupled to the electrodeless lamp to provide energy to energize the lamp;
- a dimming circuit coupled to the electrodeless lamp to control the energy provided to the lamp to vary the brightness of the generated light;
- a coupling transformer inductively coupled to the electrodeless lamp, wherein the ballast is coupled to the coupling transformer to provide the energy to energize the lamp;
- and
- an auxiliary winding electromagnetically coupled to the coupling transformer to couple the dimming circuit to the electrodeless lamp.
A dimming circuit for an electrodeless lamp inductively coupled to a coupling transformer that provides electromagnetic energy to cause the lamp to generate light, the dimming circuit comprising:
- an auxiliary winding adapted to be electromagnetically coupled to the coupling transformer;
- a switch coupled to the auxiliary winding;
- and
- a drive circuit coupled to the switch to transition the switch between a conductive state and a non-conductive state during a time interval to control brightness of the generated light, wherein a current-carrying path is established through the auxiliary winding and the switch during the conductive state.
A dimmable display device, comprising:
- an electrodeless lamp to generate light;
- a display unit to display an image, the lamp being operably positioned with respect to the display unit to illuminate the display unit to enhance viewing of the image;
- a dimming module coupled to the electrodeless fluorescent lamp to control brightness of the generated light in response to a control signal;
- and
- a coupling transformer coupled to the electrodeless lamp, the coupling transformer providing electromagnetic energy to energize the lamp to generate the light,
- wherein the dimming module comprises an auxiliary winding electromagnetically coupled to the coupling transformer, a switch coupled to the auxiliary winding, and a drive circuit to transition the switch between a conductive state and a non-conductive state during a time interval, wherein a current-carving path is established through the auxiliary winding and the switch during the conductive state.
A method for dimming an electrodeless lamp, comprising:
- inductively coupling energy to an electrodeless lamp to energize the electrodeless lamp and generate light;
- and
- restricting the coupling of the energy during a dimming portion of a time period to dim the generated light, the time period having a frequency of occurrence.
A method for making a dimmable electrodeless light source, comprising:
- providing an electrodeless lamp having a coupling transformer;
- disposing an auxiliary winding on the coupling transformer;
- and
- coupling the auxiliary winding to a drive circuit, the drive circuit being configured to establish a current carrying path through the auxiliary winding for a first time interval of a time period and to interrupt the current carrying path through the auxiliary winding for a second time interval of the time period to control brightness of light generated by the lamp.
A dimmable display device, comprising:
- an electrodeless lamp to generate light;
- a display unit to display an image, the lamp being operably positioned with respect to the display unit to illuminate the display unit to enhance viewing of the image;
- and
- a dimming module coupled to the electrodeless fluorescent lamp to control brightness of the generated light in response to a control signal, wherein the dimming module comprises a photodetector to detect ambient light and the control signal is representative of the detected ambient light.
A dimmable display device, comprising:
- an electrodeless lamp to generate light;
- a display unit to display an image, the lamp being operably positioned with respect to the display unit to illuminate the display unit to enhance viewing of the image;
- and
- a dimming module coupled to the electrodeless fluorescent lamp to control brightness of the generated light in response to a control signal, wherein the dimming module comprises a dimming control device having a range of manually selectable dimming settings and the control signal is based on the selected dimming setting.
Dependencies are inferred from the claim text.