Reduced Power Displays
First Claim
1. A backlight for a display, the backlight comprising:
- a plurality of groups of light emitters, each group comprising at least one light emitter;
a power supply, the power supply configured to supply power to the groups of light emitters; and
one or more controllers, the controllers configured to control brightness levels of the light emitters within the groups by applying pulse width modulation (PWM) driving signals to each light emitter, the PWM driving signals having a period T, a duty cycle proportional to the brightness level, and a phase offset that varies between the groups;
wherein the brightness levels depend upon received image data representing an image to be displayed and wherein the brightness levels of at least two light emitters are independently controllable.
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Accused Products
Abstract
A backlight for a display comprises a plurality of independently controllable groups of light emitters. The brightness levels of the groups of light emitters are controllable by pulse width modulation (PWM) signals generated by PWM driving circuits. The phases of PWM signals to different groups of light emitters are configured to be offset by different amounts, so as to stagger the start times of light emitters of different groups. Such phase-shifting of PWM signals may result in total power consumption that ramps up more gradually, is distributed more evenly over time, and is held to a lower maximum value than if the same PWM signals were not phase-shifted. The duration of a first PWM cycle of PWM signals for an image may also be made longer than subsequent PWM cycles for the image so as to extend the initial power ramp-up time.
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Citations
17 Claims
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1. A backlight for a display, the backlight comprising:
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a plurality of groups of light emitters, each group comprising at least one light emitter; a power supply, the power supply configured to supply power to the groups of light emitters; and one or more controllers, the controllers configured to control brightness levels of the light emitters within the groups by applying pulse width modulation (PWM) driving signals to each light emitter, the PWM driving signals having a period T, a duty cycle proportional to the brightness level, and a phase offset that varies between the groups; wherein the brightness levels depend upon received image data representing an image to be displayed and wherein the brightness levels of at least two light emitters are independently controllable. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for controlling light emitters of a backlight, the method comprising:
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determining brightness values for groups of the light emitters based on image data representing an image to be displayed; determining PWM duty cycles for the groups of light emitters based on the brightness values; applying PWM driving signals having the determined duty cycles and having phase offsets that are different for each group to the light emitters; wherein a duration of a first PWM cycle of the PWM driving signals for the image is longer than the duration of subsequent PWM cycles for the image. - View Dependent Claims (8, 9)
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10. A backlight comprising a plurality of light emitters and a power supply, the power supply having a maximum power surge capacity that is less than a combined current draw of all of the light emitters of the backlight.
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11. A display comprising N light emitters, each of the light emitters, when driven, drawing an in-rush current A, and a power supply connected to supply electrical power to the N light emitters, the power supply having a maximum out-rush current M where M<
- (N)(A).
- View Dependent Claims (12, 13)
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14. A display comprising:
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a spatial light modulator; a backlight comprising a plurality of groups of light emitters for illuminating the spatial light modulator, each group comprising at least one light emitter; a power supply, the power supply configured to supply power to the groups of light emitters; and one or more controllers, the controllers configured to control brightness levels of the light emitters within the groups by applying pulse width modulation (PWM) driving signals to each light emitter, the PWM driving signals having a period T, a duty cycle proportional to the brightness level, wherein the one or more controllers are configured to apply a different phase offset to the PWM driving signals for the light emitters of each of the groups; wherein the brightness levels depend upon received image data representing an image to be displayed and wherein the brightness levels of at least two light emitters are independently controllable.
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- 15. A lighting apparatus comprising a plurality of PWM driving circuits, each PWM driving circuit configured to generate PWM signals to drive one or more light emitters, wherein the PWM signals of each PWM driving circuit are configured to have a different phase offset.
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17. A lighting apparatus comprising a plurality of PWM driving circuits, each PWM driving circuit configured to generate PWM signals to drive one or more light emitters, wherein the PWM signals of each PWM driving circuit are configured to be time multiplexed.
Specification