Primary side current balancing scheme for multiple CCF lamp operation
First Claim
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1. A backlight system comprising:
- a first group of lamp transformers with primary windings coupled in series to conduct a first AC current and secondary windings configured for coupling to different lamps belonging to a first group of lamps;
a first group of differential amplifiers configured to receive sensed voltages indicative of voltages across the respective primary windings in the first group of lamp transformers; and
a fault detector circuit configured to receive outputs from the first group of differential amplifiers and to determine fault conditions in the first group of lamp transformers or in the first group of lamps based on amplitude changes in the sensed voltages.
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Abstract
A backlight system drives multiple lamps using balanced groups of serially-connected lamp transformers. A plurality of lamp transformers is divided into multiple transformer groups. Primary windings of the lamp transformers are coupled in series in each transformer group. Lamps are coupled to secondary windings of the lamp transformers. The transformer groups are arranged in a parallel configuration. One or more balancing transformers couple the transformer groups to a common power source. The balancing transformers divide a common current from the common power source into multiple balanced currents for the respective transformer groups.
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Citations
15 Claims
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1. A backlight system comprising:
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a first group of lamp transformers with primary windings coupled in series to conduct a first AC current and secondary windings configured for coupling to different lamps belonging to a first group of lamps; a first group of differential amplifiers configured to receive sensed voltages indicative of voltages across the respective primary windings in the first group of lamp transformers; and a fault detector circuit configured to receive outputs from the first group of differential amplifiers and to determine fault conditions in the first group of lamp transformers or in the first group of lamps based on amplitude changes in the sensed voltages. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method to detect fault conditions in a backlight system with multiple lamps, the method comprising:
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electrically coupling a first plurality of primary windings in series to conduct a first AC current, wherein the first plurality of primary windings belong to a first group of lamp transformers and secondary windings in the first group of lamp transformers are separately coupled to different lamps belonging to a first group of lamps; generating a plurality of differential voltages, wherein each of the differential voltages indicates a voltage drop across one of the primary windings; and determining a fault condition based on differences among the plurality of differential voltages. - View Dependent Claims (11, 12, 13, 14, 15)
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Specification