DC/AC cold cathode fluorescent lamp inverter
First Claim
1. A DC to AC cold cathode fluorescent lamp inverter circuit, comprising:
- a step-up transformer with a primary winding and a secondary winding for providing increased voltage to a cold cathode fluorescent lamp, wherein said primary winding and said secondary winding are electrically coupled to ground;
a first MOSFET switch coupled to said step-up transformer for selectively allowing direct current of a first polarity to flow through said step-up transformer;
a second MOSFET switch coupled to said step-up transformer for selectively allowing direct current of a second polarity to flow through said step-up transformer;
a capacitor divider electrically coupled to said cold cathode fluorescent lamp for providing a first voltage signal representing a voltage across said cold cathode fluorescent lamp;
a first feedback signal line coupled to said capacitor divider for receiving said first voltage signal from said capacitor divider representing said voltage across said cold cathode fluorescent lamp;
a timer circuit coupled to said first feedback signal line for providing a time-out sequence of a predetermined duration when said first voltage signal exceeds a predetermined threshold; and
a protection circuit coupled to said timer circuit, said first switch and said second switch for shutting down said first switch and said second switch when said first voltage signal exceeds said predetermined threshold after said predetermined duration.
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Accused Products
Abstract
A DC/AC cold cathode fluorescent lamp (CCFL) inverter circuit includes a transformer with a primary winding and a secondary winding for providing increased voltage to a CCFL, a first and second MOSFET switches for selectively allowing direct current of a first polarity and a second polarity to flow through the transformer respectively. The primary and secondary windings of the transformer are electrically coupled to ground. A capacitor divider is electrically coupled to the CCFL for providing a first voltage signal representing a voltage across the CCFL. A first feedback signal line receives the first voltage signal. A timer circuit is coupled to the first feedback signal line for providing a time-out sequence of a predetermined duration when the first voltage signal exceeds a predetermined threshold. A protection circuit shuts down the first switch and the second switch when the first voltage signal exceeds the predetermined threshold after the predetermined duration.
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Citations
20 Claims
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1. A DC to AC cold cathode fluorescent lamp inverter circuit, comprising:
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a step-up transformer with a primary winding and a secondary winding for providing increased voltage to a cold cathode fluorescent lamp, wherein said primary winding and said secondary winding are electrically coupled to ground; a first MOSFET switch coupled to said step-up transformer for selectively allowing direct current of a first polarity to flow through said step-up transformer; a second MOSFET switch coupled to said step-up transformer for selectively allowing direct current of a second polarity to flow through said step-up transformer; a capacitor divider electrically coupled to said cold cathode fluorescent lamp for providing a first voltage signal representing a voltage across said cold cathode fluorescent lamp; a first feedback signal line coupled to said capacitor divider for receiving said first voltage signal from said capacitor divider representing said voltage across said cold cathode fluorescent lamp; a timer circuit coupled to said first feedback signal line for providing a time-out sequence of a predetermined duration when said first voltage signal exceeds a predetermined threshold; and a protection circuit coupled to said timer circuit, said first switch and said second switch for shutting down said first switch and said second switch when said first voltage signal exceeds said predetermined threshold after said predetermined duration. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A liquid crystal display unit comprising:
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a liquid crystal display panel; a cold cathode fluorescent lamp for illuminating said liquid crystal display panel; a step-up transformer with a primary winding and a secondary winding coupled to said cold cathode fluorescent lamp for providing increased voltage to said cold cathode fluorescent lamp, wherein said primary winding and said secondary winding are electrically coupled to ground; a first MOSFET switch coupled to said step-up transformer for selectively allowing direct current of a first polarity to flow through said step-up transformer; a second MOSFET switch coupled to said step-up transformer for selectively allowing direct current of a second polarity to flow through said step-up transformer; a capacitor divider electrically coupled to said cold cathode fluorescent lamp for providing a first voltage signal representing a voltage across said cold cathode fluorescent lamp; a first feedback signal line coupled to said capacitor divider for receiving said first voltage signal from said capacitor divider representing said voltage across said cold cathode fluorescent lamp; a timer circuit coupled to said first feedback signal line for providing a time-out sequence of a predetermined duration when said first voltage signal exceeds a predetermined threshold; and a protection circuit coupled to said timer circuit, said first switch and said second switch for shutting down said first switch and said second switch when said first voltage signal exceeds said predetermined threshold after said predetermined duration. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method for providing power to a cold cathode fluorescent lamp of a liquid crystal display unit, said method comprising:
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providing direct current of a first polarity through a primary winding of a transformer; providing direct current of a second polarity through said primary winding of said transformer; providing increased voltage from said transformer to said cold cathode fluorescent lamp; providing a first feedback signal representing a voltage across said cold cathode fluorescent lamp from a capacitor divider electrically coupled to said cold cathode fluorescent lamp; receiving said first feedback signal representing said voltage across said cold cathode fluorescent lamp; providing a time-out sequence of a predetermined duration when said first voltage signal exceeds a predetermined threshold; and shutting down power to said cold cathode fluorescent lamp when said first voltage signal exceeds said predetermined threshold after said predetermined duration. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification