Balanced power supply circuit for multiple cold-cathode fluorescent lamps
First Claim
1. A CCFL driving circuit comprising a transformer comprising a plurality of primary windings and secondary windings, each said primary windings being coupled directly in parallel with one another and coupled to a voltage source, each of said secondary windings being coupled to a CCFL (cold cathode fluorescent lamp) circuit, each said CCFL circuit coupled together at a common node, a single feedback signal for sensing the current flowing through a selected one of said CCFL circuits, and a controller for regulating said voltage source based at least in part on said current flowing through said selected one CCFL circuit.
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Abstract
The present invention provides a CCFL driving circuit having a parallel-arranged transformer system and a feedback loop positioned to sense the current in one of the lamps in the system. Each CCFL in the system is driven by the secondary side an individual transformer. Based on the current sensed in the feedback loop, a controller supplies the appropriate driving voltage to the primary side of the transformers, which in turn powers each CCFL. Since the primary sides of the transformers are arranged in parallel, and since each CCFL is connected at a common node, it is ensured that each transformer receives identical voltage, and the current in each CCFL loop is balanced.
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16 Claims
- 1. A CCFL driving circuit comprising a transformer comprising a plurality of primary windings and secondary windings, each said primary windings being coupled directly in parallel with one another and coupled to a voltage source, each of said secondary windings being coupled to a CCFL (cold cathode fluorescent lamp) circuit, each said CCFL circuit coupled together at a common node, a single feedback signal for sensing the current flowing through a selected one of said CCFL circuits, and a controller for regulating said voltage source based at least in part on said current flowing through said selected one CCFL circuit.
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13. A method of delivering power to a cold cathode fluorescent lamp (CCFL), said method comprising the steps of:
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driving a plurality of primary windings coupled directly in parallel with one another with a power source; driving a plurality of respective secondary windings connected to a plurality of respective CCFL circuits; coupling each said CCFL circuits together at a common node; providing a single feedback signal from a selected one of said plurality of CCFL circuits for determining a current flowing through said selected CCFL; regulating said power source at least in part by the value of said current flowing through said CCFL. - View Dependent Claims (14, 15, 16)
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Specification