Power-conservation feature for liquid crystal display
An improved liquid crystal display (LCD) system that includes a user-selectable method for reducing the amount of electrical power consumed by the LCD. When a power-conservation mode is selected, power-conservation circuitry acts upon the pixel activation sequence as normally determined by the LCD driver. To minimize power consumption, a subset of the pixels otherwise to be activated are sent no power. The subset of no-power pixels may be a fixed percentage, such as fifty percent, or may vary according to the image being displayed. In either case, the pixel elements of the no-power subset may be alternated so as to minimize the impact of the power-conservation feature on the displayed image.
1. A method for conserving electrical power at an electrically-powered device having a liquid-crystal display (LCD) comprising a driver and a plurality of pixels, wherein the optical characteristics of the liquid crystal associated with each pixel are defined by the selective local application of an electrical charge, the electrically-powered device for communicating with a communications network, said method of conserving electrical power comprising the steps of:
receiving, in a driver of the LCD, data from the communications network, the data containing an image display on the LCD;
determining that a power-conservation mode, in which a selected number of the pixels are not energized, is appropriate according to predetermined criteria, the predetermined criteria comprising signals received from the communications network, the signals generated by the communications network upon detection of a device transmission signal transmitted by the electrically-powered device lower than a predetermined threshold;
analyzing the image data in a microprocessor of the LCD driver to determine the pixel-charging sequence required to produce the image associated with the data;
automatically entering power-conservation mode in which the selected number of the pixels are not energized by modifying the pixel-activation sequence to reduce the number of pixels to which voltage is to be supplied; and
displaying on the LCD an image created by the modified pixel-activation sequence.
2. The method of claim 1 , wherein the predetermined criteria for entering the power-conservation mode further comprises receipt of a user-entered instruction to enter power-conservation mode.
3. The method of claim 1 , wherein the predetermined criteria for entering the power conservation mode further comprises a low-power indication generated within the device.
4. The method of claim 1 , wherein the predetermined criteria for entering a power conservation mode further comprises a reduce-power signal.
5. The method of claim 1 , further comprising the steps of:
determining that leaving the power-conservation mode is appropriate according to predetermined criteria; and
leaving the power-conservation mode by returning to full power for all pixels.
6. The method of claim 1 , further comprising the step of selectively alternating the subset of no-power pixels.
7. A method of claim 1 , wherein the predetermined criteria for entering power-conservation mode includes an indication of the level of ambient light.
8. A for method of claim 1 , wherein the predetermined criteria for entering power conservation mode includes an automatically-generated timing signal.
9. The method of claim 1 , wherein the subset of no-power pixels is selected according to the image being displayed.
10. A portable electronic device for communicating with a communication network comprising:
a receiver for receiving information from the communications network;
a liquid-crystal display (LCD) comprising a plurality of pixels for displaying images according to the information received from the communications network; and
an LCD driver for receiving the received information and translating at least a portion of the information into instructions for selectively activating the pixels in order to produce an image, wherein the LCD driver determines if a power-conservation mode in which a selected number of pixels are not energized has been automatically selected, the power-conservation mode determined to be automatically selected if signals generated by the communications network upon detection of a device transmission signal transmitted by the portable electronic device is lower than a predetermined threshold, and, if so, modifies the instructions accordingly.
11. The device of claim 10 , wherein the automatic selection of power-conservation mode is further responsive to a low-battery indication.
12. The device of claim 10 , wherein the instruction modification performed if power-conservation mode has been selected includes omitting a predetermined number of pixel-activations.
13. The device of claim 12 , wherein the number of omitted pixel-activations is determined as a first selected percentage of the total number of pixels to be charged during a first defined portion of the pixel-activation sequence.
14. The device of claim 13 , wherein approximately fifty percent of the pixel-activation are omitted.
15. The device of claim 13 , wherein a second selected percentage of the total number of pixels to be activated determines the omitted pixel-activations in a second defined portion of the pixel-activation sequence.