Circuit for obtaining a wide dimming ratio from a royer inverter
First Claim
1. A DC-to-AC inverter circuit for obtaining a wide dimming ratio in a display back light, said DC-to-AC inverter circuit adapted to receive power from a power source, said DC-to-AC inverter circuit comprising:
- an inverter circuit, wherein said inverter circuit further comprises;
a first transistor having a collector, base and emitter;
a second transistor having a collector, base and emitter;
a resistor coupled to said emitter of only one of said first transistor and second transistor; and
a transformer having a base winding having a first lead coupled to said base of said first transistor and a second lead coupled to said base of said second transistor, a primary winding having a first lead coupled to said collector of said first transistor, a second lead coupled to said collector of said second transistor, and a center-tap lead coupled to said power source, and a secondary winding coupled to said back light.
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Accused Products
Abstract
The present invention relates to a circuit for obtaining a wide dimming ratio from a Royer inverter and, more particularly, to a circuit that allows a back light to have wide dimming ratio without having unwanted current spikes that would significantly reduce the life of the back light bulbs. The invention is directed to a DC-to-AC inverter circuit for obtaining a wide dimming ratio in a display back light. The DC-to-AC inverter circuit consists of a voltage source, a Royer inverter circuit and switch circuit to turn on the Royer inverter. The Royer inverter is configured to receive a DC pulse modulated (PWM) signal that is coupled a transformer to produce an output AC PWM signal that is sent to the display back light. The configuration creates an imbalance in the Royer circuit that in turn prevents current spikes that occur when rapidly turning on the Royer inverter.
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Citations
13 Claims
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1. A DC-to-AC inverter circuit for obtaining a wide dimming ratio in a display back light, said DC-to-AC inverter circuit adapted to receive power from a power source, said DC-to-AC inverter circuit comprising:
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an inverter circuit, wherein said inverter circuit further comprises;
a first transistor having a collector, base and emitter;
a second transistor having a collector, base and emitter;
a resistor coupled to said emitter of only one of said first transistor and second transistor; and
a transformer having a base winding having a first lead coupled to said base of said first transistor and a second lead coupled to said base of said second transistor, a primary winding having a first lead coupled to said collector of said first transistor, a second lead coupled to said collector of said second transistor, and a center-tap lead coupled to said power source, and a secondary winding coupled to said back light. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A DC-to-AC inverter circuit for obtaining a wide dimming ratio in a display back light, said DC-to-AC inverter circuit adapted to receive power from a power source, said DC-to-AC inverter circuit comprising:
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an inverter circuit, wherein said inverter circuit further comprises;
a first transistor having a collector, base, emitter and saturation characteristic;
a second transistor having a collector, base, emitter, and saturation characteristic, wherein said second transistor saturation characteristic is different from said first transistor saturation characteristic and, wherein said difference in saturation characteristic between said first transistor and second transistor is of sufficient value to prevent current spikes in said DC-to-AC inverter circuit during turn-on; and
a transformer having a base winding having a first lead coupled to said base of said first transistor and a second lead coupled to said base of said second transistor, a primary winding having a first lead coupled to said collector of said first transistor, a second lead coupled to said collector of said second transistor, and a center-tap lead coupled to said power source, and a secondary winding coupled to said back light. - View Dependent Claims (10, 11, 12, 13)
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Specification