Power dissipation control for a visual display screen

A visual display screen is partitioned into a plurality of screen portions. Power drivers associated with the screen portions are grouped selectively according to the number of screen portions. The power supplied to each group of drivers is selectively controlled to select which screen portions receive power at any given time. In the event that a screen portion is not active for a current display after a preselected minimum amount of time, that screen portion is disabled because the power to that screen portion is selectively turned off.

BACKGROUND OF THE INVENTION 
This invention generally relates to electronic visual display screens. More 
particularly, this invention relates to a system and method for 
controlling power dissipation in a visual display screen. 
A variety of electronic visual display screens are currently used in a 
variety of applications. Workers in the art are constantly trying to 
improve the operating parameters of electronic visual display screens. For 
example, a "screen-saver" program is typically provided with a home 
computer for reducing the possibility of damage to the computer monitor 
display as a result of leaving a static image on the screen for a 
prolonged period of time. 
Conventional screen-savers may not be useful, however, in all applications. 
For example, when a visual screen display is incorporated into a vehicle, 
it may be necessary to keep at least part of the screen active at all 
times. Therefore, conventional screen-savers, which typically disrupt the 
display on the entire screen, are not useful in such situations. Further, 
some applications require a minimization of power usage. Conventional 
screen savers do not adequately address such situations. Accordingly, 
there is a need for an improved system and method for controlling a 
display on an electronic visual display screen. 
This invention is a system and method that is useful for controlling 
selected portions of a visual display screen. The system and method of 
this invention provide the ability to selectively disable or turn off 
portions of a visual display screen to reduce the amount of power 
dissipated by the screen and to protect the screen from potential damage. 
SUMMARY OF THE INVENTION 
In general terms, this invention is a system for controlling an 
electrically generated display. The system includes a display screen 
having a matrix of a plurality of screen portions wherein the matrix 
includes a plurality of columns and a plurality of rows. A plurality of 
power drivers are associated with the plurality of columns. Similarly, a 
plurality of power drivers are associated with the plurality of rows. An 
electronic controller controls the display on the display screen. A 
plurality of power switches couple the power drivers to the electronic 
controller. A power control module that is coupled to the power switches 
and the power drivers selectively controls a supply of power to the power 
drivers depending on an operation condition of the power switches. 
In general terms, the method of this invention is a method of controlling 
power usage for a visual display screen. The method includes several basic 
steps. First, the visual display screen is divided into a plurality of 
display surfaces. Power is supplied to all of the display surfaces. A 
display is generated on the display screen. Next, an inactive display 
surface is defined as a display surface that has not included at least a 
portion of the generated display for at least a preselected period of 
time. A determination is made whether any of the display surfaces is an 
inactive display surface. The power to any inactive display surface is 
then shut off once such a determination is made. 
The various features and advantages of this invention will become apparent 
to those skilled in the art from the following detailed description of the 
presently preferred embodiment. The drawings that accompany the detailed 
description can be described as follows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 schematically illustrates a system 20 for controlling the power 
dissipation and display on a visual display screen 22. The display screen 
22 is divided into a plurality of screen portions including the 
illustrated portions 24, 26, 28 and 30. The ellipses 32 indicate that any 
number of screen portions can exist between the illustrated portions. The 
screen portions preferably are immediately adjacent each other so that the 
entire display screen 22 is accounted for by a screen portion. 
A video controller 34, which is a conventional microprocessor or computer 
unit, controls the display on the display screen 22. Data 36 from various 
subsystems coupled with the controller 34 and video data from computer 
memory, for example, are supplied to the video controller 34 for 
generating the display on the display screen 22. 
The display screen 22 is divided into a number of pixels as is understood 
by those skilled in the art. The screen pixels are arranged in a matrix 
having locations identifiable by column and row position. Each screen 
pixel preferably is powered by a column voltage and a row voltage. 
Accordingly, each screen portion is made up of a plurality of screen 
pixels. 
According to this invention, electrodes for providing a column voltage are 
divided and the outputs are grouped into banks of column drivers. One 
column driver bank is associated with each screen portion. For example, a 
column driver bank 38 is associated with the screen portion 24. The screen 
pixels within the screen portion 24 are powered by the column drivers 38 
and the row drivers 40 and the row drivers 42. The bank of row drivers 40 
accounts for the odd numbered rows through the screen portion 24, while 
the row drivers 42 account for the even numbered rows through the screen 
portion 24. Similarly, the column voltages for the screen pixels in the 
screen portion 26 are provided through the bank of column drivers 44. The 
row voltages of the pixels in the screen portion 26 are provided through 
the bank of row drivers 40 and 42. The screen portion 28 is powered 
through the column driver bank 46 and the row driver banks 48 and 50. 
Likewise, the screen portion 30 is powered through the column drivers bank 
51 and the row driver banks 48 and 50. 
In the illustrated embodiment, the screen 22 is effectively divided into a 
top half and a bottom half. The top half and the bottom half each have a 
designated number of row drivers associated with them. The top half is 
then effectively subdivided into a plurality of screen portions and the 
bottom half is similarly subdivided into a plurality of screen portions. 
It is also possible, according to this invention, to subdivide the screen 
from top to bottom into more screen portions where necessary. 
A voltage source 52 provides the power to the column drivers 38 through a 
power switch 54. The power switch 54 preferably is an FET type switch. The 
voltage source 52 also powers the column driver bank 44 through a power 
switch 56. Another voltage source 58 is used for powering the column 
drivers 46 through a power switch 60 and the column driver bank 51 through 
a switch 62. All of the switches 54, 56, 60 and 62 preferably are FET 
switches. 
A power conservation module 64 is coupled to the power switches 54, 56, 60 
and 62. The power conservation module is also coupled to the voltage 
sources 52 and 58 and the row driver banks 40, 42, 48 and 50. Any 
conventional microprocessor or computer can be used as the power 
conservation module 64. 
The power conservation module 64 selectively disconnects any of the column 
dryer banks from their respective voltage sources by controlling the power 
switches. Although it is not specifically illustrated in FIG. 1, the row 
driver banks preferably are powered in a manner similar to that 
illustrated for powering the column driver banks. Accordingly, the power 
conservation module 64 can also turn off the power to the row driver 
banks. 
The power module 64 controls the power to the various row and bank drivers. 
The power supplied to different driver banks is selectively controlled by 
the power module 64 to reduce the amount of power dissipation in the 
display screen 22. Reducing the amount of power dissipation when a display 
screen is used in a vehicle is especially advantageous because the overall 
amount of electrical power available on a vehicle is limited for practical 
reasons. In the preferred embodiment, a timer and monitoring module within 
the controller 34 monitors the power switches and determines whether the 
switches are active. When a control switch has not been active for a 
preselected period of time, the video controller 34 modifies the 
horizontal and vertical synchronization signals that are supplied to the 
screen 22. The controller 34 communicates with the power module 64 that 
responsively disconnects one or more of the banks of drivers from its 
respective voltage source. 
In an alternative embodiment, the internal timer and the monitoring module 
are located within the power module 64. In that embodiment, the 
communications between the controller 34 and the power module 64 are 
modified appropriately. 
The preselected minimum amount of time for a power switch to be inactive, 
which indicates that a corresponding screen portion is inactive, depends 
upon a particular application. Given this specification, one skilled in 
the art can develop specific software for achieving the monitoring, timing 
and power switching functions associated with this invention. 
FIG. 2 schematically illustrates the display screen 22 divided into four 
screen portions. Assuming that the power switches for the screen portions 
26, 28 and 30 have been inactive for more than a preselected minimum 
amount of time, the controller 34 communicates with the power module 64 
that those screen portions can be disabled because they are not being used 
for the current display. The power module responsively disables the screen 
portions 26, 28 and 30 by turning off the appropriate power switches to 
disconnect the appropriate drivers from their respective voltage source. 
Accordingly, only the screen portion 24 receives power and generates the 
current display. 
In the event that the controller 34 determines that a new display or 
additional display is required on the screen 22, it communicates with the 
power module 64. The power module 64 then responsively provides power to 
the necessary screen portions of the screen 22. 
The strategy for dividing the screen 22 into a plurality of screen portions 
according to this invention can be summarized as follows. The screen 22 
preferably is partitioned into 2K screen portions, where K is an integer 
greater than or equal to 2. The column electrodes are then split and the 
column outputs are grouped into K banks of column drivers. In FIG. 2, for 
example, K equals 2. Under the scenario described above, the screen 
portion 24 is the only active surface of the display. Since there are two 
column banks, the column bank associated with the screen portions 26 and 
30 is disabled. The row drivers associated with the screen portions 28 and 
30 are also disabled. Accordingly, the amount of power utilized by the 
screen 22 is reduced by approximately 75% and only one-quarter of the 
screen is powered as needed. 
The foregoing description is exemplary rather than limiting in nature. 
Modifications and variations to the disclosed embodiment will become 
apparent to those skilled in the art that do not necessarily depart from 
the purview and spirit of this invention. Accordingly, the legal scope 
afforded to this invention can only be determined by studying the appended 
claims.