Split phase inverters for CCFL backlight system
First Claim
1. An inverter comprising:
- 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 two-switch network configured to generate a first alternating current signal across a secondary winding of the first transformer using a first control signal to control a first switch and a substantially inverted version of the first control signal to control a second switch, wherein first dead times are inserted between the first control signal and the substantially inverted version of the first control signal at respective first switch-over transitions;
a second two-switch network configured to generate a second alternating current signal across a secondary winding of the second transformer using a second control signal to control a third switch and a substantially inverted version of the second control signal to control a fourth switch, wherein the first and the second alternating current signals have substantially constant duty cycles, and second dead times are inserted between the second control signal and the substantially inverted version of the second control signal at respective second switch-over transitions; and
a controller configured to generate the first control signal and the second control signal, wherein power to the lamp structure is adjusted by varying a phase difference between the first control signal and the second control signal.
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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.
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Citations
15 Claims
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1. 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 two-switch network configured to generate a first alternating current signal across a secondary winding of the first transformer using a first control signal to control a first switch and a substantially inverted version of the first control signal to control a second switch, wherein first dead times are inserted between the first control signal and the substantially inverted version of the first control signal at respective first switch-over transitions; a second two-switch network configured to generate a second alternating current signal across a secondary winding of the second transformer using a second control signal to control a third switch and a substantially inverted version of the second control signal to control a fourth switch, wherein the first and the second alternating current signals have substantially constant duty cycles, and second dead times are inserted between the second control signal and the substantially inverted version of the second control signal at respective second switch-over transitions; and a controller configured to generate the first control signal and the second control signal, wherein power to the lamp structure is adjusted by varying a phase difference between the first control signal and the second control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An inverter comprising:
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a controller; a first power transformer; a second power transformer, wherein at least one lamp is coupled between the first power transformer and the second power transformer; and split switching arms, wherein each of the split switching arms comprises a two-switch network, one of the split switching arms is dedicated to the first power transformer to generate a first output voltage by driving a first switch with a first control signal responsive to said controller and driving a second switch with a substantially inverted version of the first control signal responsive to said controller, wherein first dead times are inserted between the first control signal and the substantially inverted version of the first control signal at respective first switch-over transitions by said controller, another of the split switching arms is dedicated to the second power transformer to generate a second output voltage by driving a third switch with a second control signal responsive to said controller and driving a fourth switch with a substantially inverted version of the second control signal responsive to said controller, wherein second dead times are inserted between the second control signal and the substantially inverted version of the second control signal at respective second switch-over transitions by said controller, the the first output voltage and the second output voltage combine to generate a voltage across the lamp, and power to the lamp is adjusted by symmetrically adjusting the pulse widths of the first and the second control signals. - View Dependent Claims (10, 11, 12, 13)
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14. A method for driving a lamp, the method comprising:
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driving a first terminal of a lamp with a first dedicated two-switch network comprising a first switch and a second switch, wherein the first switch is controlled by a first control signal and the second switch is controlled by a substantially inverted version of the first control signal; driving a second terminal of the lamp with a second dedicated two-switch network comprising a third switch and a fourth switch, wherein the third switch is controlled by a second control signal and the fourth switch is controlled by a substantially inverted version of the second control signal; varying power to the lamp by either symmetrically adjusting the pulse widths of the first control signal and the second control signal or adjusting a phase difference between the first control signal and the second control signal; and inserting dead times between the controls signals and their respective inverted versions. - View Dependent Claims (15)
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Specification