Balancing transformers for multi-lamp operation
First Claim
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1. A backlight system comprising:
- a plurality of loads in a parallel configuration;
a current source for powering the plurality of loads;
a ring balancer coupled in series with the plurality of loads, wherein the ring balancer comprises a plurality of balancing transformers with respective primary windings and respective secondary windings, each of the primary windings connected in series with at least one load, the secondary windings connected in series with each other; and
a fault detection circuit configured to monitor a plurality of node voltages in the secondary windings, to generate a feedback voltage corresponding to at least one of the plurality of node voltages, and to compare the feedback voltage with a reference voltage to determine a fault condition.
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Abstract
A ring balancer comprising a plurality of balancing transformers facilitates current sharing in a multi-lamp backlight system. The balancing transformers have respective primary windings separately coupled in series with designated lamps and have respective secondary windings coupled together in a closed loop. The secondary windings conduct a common current and the respective primary windings conduct proportional currents to balance currents among the lamps. The ring balancer facilitates automatic lamp striking and the lamps can be advantageously driven by a common voltage source.
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Citations
20 Claims
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1. A backlight system comprising:
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a plurality of loads in a parallel configuration; a current source for powering the plurality of loads; a ring balancer coupled in series with the plurality of loads, wherein the ring balancer comprises a plurality of balancing transformers with respective primary windings and respective secondary windings, each of the primary windings connected in series with at least one load, the secondary windings connected in series with each other; and a fault detection circuit configured to monitor a plurality of node voltages in the secondary windings, to generate a feedback voltage corresponding to at least one of the plurality of node voltages, and to compare the feedback voltage with a reference voltage to determine a fault condition. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method to balance currents among multiple parallel branches of loads and to detect a fault condition, the method comprising:
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providing a ring balancer in series with a plurality of loads, wherein the ring balancer comprises a plurality of balancing transformers with respective primary and respective secondary windings; connecting each of the primary windings of the balancing transformers in series with at least one load; connecting the secondary windings of the balancing transformers in series with each other such that a common current circulates in the secondary windings when at least one load is conducting current; monitoring a plurality of node voltages in the secondary windings to detect a fault condition; and turning off a current source when the fault condition occurs. - View Dependent Claims (9, 10, 11, 12, 13)
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14. An illumination system comprising:
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a plurality of load structures in a parallel configuration; a current source for powering the plurality of load structures; a ring balancer coupled in series with the plurality of load structures, wherein the ring balancer comprises a plurality of balancing transformers with respective primary windings and respective secondary windings, each of the primary windings connected in series with at least one load structure, the secondary windings connected in series with each other; and a fault detection circuit configured to monitor voltages in the secondary windings. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification