Automatic ambient light compensation for display backlighting
AssigneeNational Semiconductor Corporation
InventorKhosrow Vijeh
Life of this patent
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Abstract
Control circuitry is used to control the backlighting of electronic displays. A light sensor (such as a phototransistor) is used to continuously measure ambient light conditions that are associated with an electronic display. A linear, continuous light-level signal is produced in response to the continuous measuring by the light sensor. The light-level signal is applied to a first input pin of an operational amplifier. The operational amplifier produces an output signal that is linear with respect to the light-level signal. The output signal is coupled to a second input pin, which provides feedback for the amplifier. The output signal is further coupled to an LED driver for driving backlighting LEDs.
Claims13
A method for controlling backlighting, comprising:
- continuously measuring ambient light conditions with a light sensor;
- producing a continuous light-level signal in response to the continuous measuring by the light sensor;
- producing a continuous feedback signal in response to the continuous light-level signal, wherein the continuous feedback signal is produced by summing the continuous light-level signal and a voltage reference signal at a first input node of an amplifier, and wherein the continuous feedback signal is provided by coupling an output of the amplifier to a second input pin of the amplifier;
- and
- producing a signal for driving backlighting in response to the continuous feedback signal such that the driving signal drives the backlighting in proportion to ambient light.
A circuit for controlling backlighting, comprising:
- means for continuously measuring ambient light;
- means for producing a continuous light-level signal in response to the continuous measuring by the ambient light measuring means;
- amplifier means for producing a continuous feedback signal in response to the continuous light-level signal, wherein the continuous feedback signal is produced by summing the continuous light-level signal and a voltage reference signal at a first input node of the amplifier means, and wherein the continuous feedback signal is provided by coupling an output of the amplifier means to a second input pin of the amplifier means;
- and
- means for producing a signal for driving backlighting in response to the continuous feedback signal such that the driving signal drives the backlighting in proportion to ambient light.
A circuit for controlling backlighting, comprising:
- a light sensor that is arranged to continuously measuring ambient light conditions;
- a resistor that is arranged to produce a continuous light-level signal in response to the continuous measuring by the light sensor;
- an amplifier that is arranged to produce a continuous feedback signal in response to the continuous light-level, and wherein the continuous feedback signal is provided by coupling an output of the amplifier to a second input pin of the amplifier;
- and
- a driver that is arranged to produce a signal for driving backlighting in response to the continuous feedback signal such that the driving signal drives the backlighting in proportion to ambient light.
Dependencies are inferred from the claim text.