Split phase inverters for CCFL backlight system
First Claim
1. A method to drive a plurality of floating lamps, said method comprising:
- generating a first AC signal across a secondary winding of a first transformer, wherein the first transformer is driven by a first switching network;
generating a second AC signal across a secondary winding of a second transformer, wherein the second transformer is driven by a second switching network;
coupling at least a first lamp between a first terminal of the secondary winding of the first transformer and a first terminal of the secondary winding of the second transformer; and
coupling at least a second lamp between a second terminal of the secondary winding of the first transformer and a second terminal of the secondary winding of the second transformer such that the first AC signal and the second AC signal combine to generate respective lamp voltages across the first lamp and the second lamp;
using a common controller to control both the first switching network and the second switching network such that the first AC signal and the second AC signal combine destructively when switching states of the first switching network and the second switching network are in phase, and such that the first AC signal and the second AC signal combine constructively when switching states of the first switching network and the second switching network are out of phase.
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Accused Products
Abstract
An apparatus and method for driving a lamp are provided. In one embodiment, an inverter having four switching elements is split into two inverter arms that are deployed at separate terminals of a floating lamp structure to achieve even light output. A controller drives both inverter arms such that power switching lines do not cross the floating lamp structure. In one embodiment, the controller adjusts the brightness of the lamp structure by adjusting the phase difference between outputs of a first inverter arm relative to a second inverter arm. In one embodiment, the controller adjusts the brightness by symmetrically pulse width modulating the outputs of the first inverter arm and the second inverter arm.
366 Citations
20 Claims
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1. A method to drive a plurality of floating lamps, said method comprising:
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generating a first AC signal across a secondary winding of a first transformer, wherein the first transformer is driven by a first switching network; generating a second AC signal across a secondary winding of a second transformer, wherein the second transformer is driven by a second switching network; coupling at least a first lamp between a first terminal of the secondary winding of the first transformer and a first terminal of the secondary winding of the second transformer; and coupling at least a second lamp between a second terminal of the secondary winding of the first transformer and a second terminal of the secondary winding of the second transformer such that the first AC signal and the second AC signal combine to generate respective lamp voltages across the first lamp and the second lamp; using a common controller to control both the first switching network and the second switching network such that the first AC signal and the second AC signal combine destructively when switching states of the first switching network and the second switching network are in phase, and such that the first AC signal and the second AC signal combine constructively when switching states of the first switching network and the second switching network are out of phase. - View Dependent Claims (2, 3, 4, 5)
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6. A backlight system comprising:
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a first switching network configured to drive a first transformer to generate a first AC signal across a secondary winding of the first transformer; a second switching network configured to drive a second transformer to generate a second AC signal across a secondary winding of the second transformer, wherein a common controller controls the first switching network and the second switching network; a first lamp coupled between a first terminal of the secondary winding of the first transformer and a first terminal of the secondary winding of the second transformer; and a second lamp coupled between a second terminal of the secondary winding of the first transformer and a second terminal of the secondary winding of the second transformer, wherein the first AC signal and the second AC signal combine to generate respective lamp voltages across the first lamp and the second lamp. - View Dependent Claims (7, 8, 9, 10)
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11. A method to drive one or more lamps, said method comprising:
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coupling a lamp structure between a secondary winding of a first transformer and a secondary winding of a second transformer, wherein the lamp structure comprises one or more lamps; driving the first transformer with a first push-pull switching network such that separate primary windings of the first transformer alternately conduct to generate a first AC signal across the secondary winding of the first transformer; driving the second transformer with a second push-pull switching network such that separate primary windings of the second transformer alternately conduct to generate a second AC signal across the secondary winding of the second transformer, wherein the first AC signal and the second AC signal combine to generate a lamp voltage across the lamp structure; and controlling the first push-pull switching network and the second push-pull switching network with one controller such that the first AC signal and the second AC signal combine destructively during a first switching state of the first switching network and the second switching network, and such that the first AC signal and the second AC signal combine constructively during a second switching state of the first switching network and the second switching network. - View Dependent Claims (12, 13, 14, 15)
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16. An inverter comprising:
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a first transformer; a second transformer, wherein a lamp structure is coupled in a floating configuration between a secondary winding of the first transformer and a secondary winding of the second transformer; a first push-pull switching network configured to drive the first transformer such that separate primary windings of the first transformer alternately conduct to generate a first AC signal across the secondary winding of the first transformer; and a second push-pull switching network configured to drive the second transformer such that separate primary windings of the second transformer alternately conduct to generate a second AC signal across the secondary winding of the second transformer, wherein one controller controls both the first push-pull switching network and the second push-pull switching network such that the first AC signal and the second AC signal combine destructively during a first period, and such that the first AC signal and the second AC signal combine constructively during a second period. - View Dependent Claims (17)
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18. An inverter comprising:
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a first transformer; a second transformer, wherein a lamp structure is coupled in a floating configuration between a secondary winding of the first transformer and a secondary winding of the second transformer; a first push-pull switching network configured to drive the first transformer such that separate primary windings of the first transformer alternately conduct to generate a first AC signal across the secondary winding of the first transformer; and a second push-pull switching network configured to drive the second transformer such that separate primary windings of the second transformer alternately conduct to generate a second AC signal across the secondary winding of the second transformer, wherein one controller controls both the first push-pull switching network and the second push-pull switching network, wherein each of the transformers comprises a primary winding with a center tap coupled to a first polarity of a DC source and each of the push-pull switching networks comprises; a first transistor coupled between a second polarity of the DC source and a first terminal of the primary winding; and a second transistor coupled between the second polarity of the DC source and a second terminal of the primary winding.
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19. An inverter comprising:
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a first transformer; a second transformer, wherein a lamp structure is coupled in a floating configuration between a secondary winding of the first transformer and a secondary winding of the second transformer; a first push-pull switching network configured to drive the first transformer such that separate primary windings of the first transformer alternately conduct to generate a first AC signal across the secondary winding of the first transformer; and a second push-pull switching network configured to drive the second transformer such that separate primary windings of the second transformer alternately conduct to generate a second AC signal across the secondary winding of the second transformer, wherein one controller controls both the first push-pull switching network and the second push-pull switching network, wherein each of the transformers comprises two primary windings and each of the push-pull switching networks comprises; a first transistor coupled between a first polarity of a DC source and a first terminal of a first primary winding, wherein a second terminal of the first primary winding is coupled to a second polarity of the DC source; and a second transistor coupled between the second polarity of the DC source and a first terminal of a second primary winding, wherein a second terminal of the second primary winding is coupled to the first polarity of the DC source. - View Dependent Claims (20)
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Specification