Method and apparatus for dimming a lamp in a backlight of a liquid crystal display
First Claim
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1. An apparatus for dimming the brightness of at least one lamp, the apparatus comprising:
- a power supply that supplies direct-current power, the power supply being referenced to ground; and
an inverter, operatively connectable to said power supply, for driving the lamp, the inverter comprising;
first switching means for creating alternating-current power from the direct-current power;
power conversion means, operatively connectable to said first switching means, for providing and maintaining an arc voltage across the lamp;
modulating means, operatively connectable to said power conversion means, for modulating the alternating-current power to control and vary the alternating-current power across the lamp between zero volts and the arc voltage;
a plurality of reactive components operatively connectable to the power conversion means, said plurality of reactive components storing energy provided by said power supply; and
second switching means, operatively connectable to said plurality of reactive components, for switching the lamp between an on and an off state, said second switching means being positioned in the inverter such that energy stored in said plurality of reactive components is discharged to ground when the lamp is switched to the off state.
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Abstract
A method and apparatus for dimming a lamp in a backlight system of a display device, e.g., liquid crystal display ("LCD"), with a brightness dimming ratio of 10,000:1, which is a factor of 10 better than conventional dimming devices. A switch is provided in an inverter circuit, which has reactive components, that drives the lamp. The is positioned in the inverter circuit such that, when it is closed, the energy stored within the reactive components of the inverter circuit is discharged to ground. In one embodiment, the signals from the power supply are pulse width modulated.
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Citations
16 Claims
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1. An apparatus for dimming the brightness of at least one lamp, the apparatus comprising:
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a power supply that supplies direct-current power, the power supply being referenced to ground; and an inverter, operatively connectable to said power supply, for driving the lamp, the inverter comprising; first switching means for creating alternating-current power from the direct-current power; power conversion means, operatively connectable to said first switching means, for providing and maintaining an arc voltage across the lamp; modulating means, operatively connectable to said power conversion means, for modulating the alternating-current power to control and vary the alternating-current power across the lamp between zero volts and the arc voltage; a plurality of reactive components operatively connectable to the power conversion means, said plurality of reactive components storing energy provided by said power supply; and second switching means, operatively connectable to said plurality of reactive components, for switching the lamp between an on and an off state, said second switching means being positioned in the inverter such that energy stored in said plurality of reactive components is discharged to ground when the lamp is switched to the off state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus for dimming the brightness of at least one lamp, the apparatus comprising:
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a power supply that supplies direct-current power, the power supply being referenced to ground; and an inverter, operatively connectable to said power supply, for driving the lamp, the inverter comprising; switching means for creating alternating-current power from the direct-current power and for switching the lamp between an on and an off state; power conversion means, operatively connectable to said switching means, for providing and maintaining an arc voltage across the lamp; modulating means, operatively connectable to said power conversion means, for modulating the alternating-current power to vary the alternating-current power across the lamp between zero volts and the arc voltage; and a plurality of reactive components operatively connectable to the power conversion means, said plurality of reactive components storing energy provided by said power supply; and wherein said switching means is configured in the inverter such that energy stored in said plurality of reactive components is discharged to ground when the lamp is switched to the off state. - View Dependent Claims (14)
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15. A method of dimming the brightness of at least one lamp, the method comprising the steps of:
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providing a power supply that supplies direct-current power, the power supply being referenced to ground; and providing an inverter to drive the lamp, the inverter comprising a plurality of reactive components that store energy provided by the power supply, the step of providing an inverter comprising the steps of; converting the direct-current power to alternating-current power; providing and maintaining an arc voltage across the lamp; modulating the alternating-current power to control and vary the alternating-current power across the lamp between zero volts and the arc voltage; and switching the lamp between an on and an off state through the use of switching means that are positioned in the inverter such that energy stored in the plurality of reactive components is discharged to ground when switched to the off state. - View Dependent Claims (16)
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Specification