Power down mode for computer system

• US 5,757,365 A
• Filed: 06/07/1995
• Issued: 05/26/1998
• Est. Priority Date: 06/07/1995
• Status: Expired due to Fees

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Ho, Simon
• Primary Examiner(s): Liang, Regina
• Application Number:
  US08/487,115
• Time in Patent Office: 1,084 Days
• Field of Search: 345/212, 345/211, 345/89, 345/97, 345/147, 345/98, 345/204, 364/707, 395/750.01, 395/750.03, 395/750.06
• US Class Current: 345/212
• CPC Class Codes: G06F 1/3218 of display devices
• CPC Class Codes: G06F 1/3281 Power saving in PCMCIA card
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: G09G 5/363 Graphics controllers
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A computer system includes a CPU and VGA/LCD controller interacting with a main system memory for processing input data and displaying it on an LCD panel screen that includes a plurality of row and column drive chips on the panel. Each column drive chip includes a panel driver memory and panel driver control logic. A frame rate modulated grey-scale data signal is fed from the processor and VGA/LCD controller to the panel driver memory. Timing signals, including horizontal and vertical clocks, and data shift signals, are fed to the panel driver control circuit to control the panel driver memory from which data is read out for display on the LCD panel screen. Upon detection of the absence of screen update information for two full frame periods the system enters a power down mode by re-mapping the grey-scale data to black-and-white data, stopping the data shift clock, and disabling portions of the VGA/LCD controller and its sequencer so that the latter enters a screen off mode. Stopping of the data shift clock causes the display panel and its panel driver memory to enter a self-refresh mode in which a frame of data stored in the panel driver memory is repetitively read out under control of the vertical and horizontal clock signals.

Claims

1. A power saving computer system comprising:

an information processor for storing and processing information, comprising;

a display controller for generating frames of update data, each frame of update data including a plurality of grey-scale pixel data groups, each pixel data group having an n-bit signal defining one of a plurality of grey-scale brightness grades;

a power-saving circuit responsive to absence of a predetermined number of frames of update data for temporarily disabling portions of said information processor; and

remapping means in communication with said display controller and said power-saving circuit for remapping the grey-scale pixel data groups of a current frame of update data into corresponding black-and-white pixel data defining only one of two brightness grades in response to the absence of update data; and

a display panel for selectively receiving the frames of update data from said information processor to generate an image on a panel screen, comprising;

a panel memory in communication with said display controller for storing at least the remapped current frame of update data; and

refresh means in communication with said panel memory, said display controller, and said power-saving circuit to self-refresh the panel screen from update data stored in said panel memory in response to the absence of update data.

2. The computer system of claim 1 including means for re-enabling said portions of said information processor upon reoccurrence of said update data.

3. The computer system of claim 1 wherein said display panel further comprises a panel driver connected to transmit panel display control information from said display controller to said panel memory.

4. The computer system of claim 3 wherein

said display controller includes timing means for generating a vertical timing signal, a horizontal timing signal, and a data shift signal;

wherein said panel driver includes means for receiving the timing signals and controlling flow of update data into and out of said panel memory in response to the timing signals;

wherein the data shift signal controls transmission of update data from said display controller into said panel memory, said power-saving circuit including means for temporarily disabling transmission of the data shift signal to said panel driver; and

wherein said display panel further comprises means for repetitively transferring information stored in said panel memory to said display panel under control of said horizontal and vertical timing signals.

5. The computer system of claim 1, further comprising means for transmitting at least one full frame of black-and- white data to said panel memory after remapping the current frame of update data.

6. The computer system of claim 1, further comprising means for storing one full frame of said black-and-white signal output in said panel memory.

7. The computer system of claim 1, wherein said display controller comprises a VGA/LCD controller having a sequencer;

and

wherein said power-saving circuit includes means for disabling portions of said sequencer.

8. The computer system of claim 7 wherein said VGA/LCD controller includes a graphics controller, an attributes controller, and a look-up table, and wherein said power-saving circuit further includes means for disabling said graphics controller, said attributes controller and said look-up table.

9. A power saving computer system comprising:

an information processor for storing and processing information and including a display controller;

a display panel for receiving frames of update data from said information processor;

means responsive to absence of a predetermined number of frames of update data for temporarily disabling portions of said information processor; and

means for re-enabling said portions of said information processor upon reoccurrence of said update data,

wherein said display panel includes a panel screen and a panel driver memory connected to store and transmit data from said information processor to said panel screen, and means for causing said panel driver memory to self-refresh said panel screen from data stored in said panel driver memory in response to the absence of update data;

wherein said display panel includes a panel screen and a panel driver memory connected to store and transmit data from said information processor to said panel screen and including a panel driver connected to transmit panel display control information from said information processor to said panel driver memory;

wherein said information processor includes means for generating a vertical timing signal, a horizontal timing signal, and a data shift signal, wherein said panel driver includes means for receiving said timing signals and controlling flow of data into and out of said panel driver memory in response to said timing signals, and wherein said data shift signal controls transmission of data from said information processor into said panel driver memory, said means responsive to absence of update data including means for temporarily disabling transmission of said data shift signal to said panel driver, and including means for repetitively reading information stored in said panel driver memory to said display panel under control of said horizontal and vertical timing signals; and

wherein said data includes a plurality of grey-scale pixel data groups each having an n-bit signal defining one of a plurality of grey-scale brightness grades, and grey-scale means in said information processor for causing said panel driver and panel driver memory to control said panel screen according to the brightness grade of the pixel data group of said data signal, said means for temporarily disabling including means for re-mapping said grey-scale means to provide a black-and-white signal output that controls said panel screen to display pixels having only one of two brightness grades.

10. In a computer system having an information processor that receives and processes information and transmits a data signal together with control and timing signals to a display panel for displaying frames of data, said information processor including a grey-scale controller for providing data defining a grey-scale display, wherein said control and timing signals include a data shift clock, a horizontal clock, and a vertical clock, and wherein said display panel includes a panel screen, a panel driver memory responsive to said data signal for storing at least one frame of said data, and a panel driver responsive to said control and timing signals for controlling said panel driver memory to read data from said panel driver memory to said panel screen, a method for reducing power consumption of said computer system, comprising the steps of:

monitoring transmission of said data signal from said information processor to said display panel; and

causing said computer system to enter a power down mode upon detection of the absence of transmission of said data at a signal to said display panel for a predetermined number of frames of data, said step of causing said computer system to enter a power down mode comprising;

disabling parts of said information processor;

changing operation of said grey-scale controller to cause it to provide data defining a black-and-white display to said panel driver memory;

waiting for at least two full frames after detection of the absence of transmission of said data signal to ensure storage of one complete frame of black-and-white data in said panel driver memory;

disabling transmission of said data shift clock to said panel driver; and

entering a self-refresh mode, said self-refresh mode comprising the steps of repetitively reading a frame of data from said panel driver memory to said panel screen under control of said horizontal and vertical clock signals.

11. The method of claim 10 wherein said control and timing signals include an internal vertical clock having a vertical clock period, said step of detection of the absence of transmission of said data signal comprising monitoring presence or absence of said data signal for a time interval that is an integral multiple of said vertical clock period, waiting at least two additional vertical clock period upon detection of the absence of transmission of said data signal, at the end of said two additional vertical clock period performing said steps of disabling parts of said information processor and disabling said data shift clock, and at the second vertical clock following the end of said two additional internal vertical clock periods, initiating a self-refresh operation by repetitively reading a frame of data stored in said panel driver memory to said panel screen under control of said horizontal and frame clocks.

12. The method of claim 10 wherein said computer system includes a sequencer, and wherein said step of causing said computer system to enter a power down mode comprises disabling parts of said sequencer.

13. A video display system, comprising:

a video display for displaying a grey-scale image specified by plural frames of video data, said video display having a first operating mode and a second operating mode consuming less power than the first operating mode;

a conversion means for converting a given frame of video data comprising plural sequences of grey-scale image data into corresponding two-state image data; and

control means for controlling the video display to switch from the first operating mode to the second operating mode in response to non-receipt of a predetermined number of consecutive frames of the video data for a predetermined period of time, in which the control means controls the video display to display a two-state image specified by the converted given frame of video data.

14. A system as in claim 13, in which the control means controls the video display to switch from the first operating mode to the second operating mode in response to non-receipt of two consecutive frames of video data.

15. A system as in claim 13, in which:

the video display receives update pulses together with said frames of video data respectively; and

the control means controls the video means to switch from the first operating mode to the second operating mode in response to non-receipt of a predetermined number of consecutive update pulses.

16. A system as in claim 13, in which:

the video display comprises a frame memory for storing a frame of video data including the converted given frame of video data; and

the control means controls the video display to repetitively read out and display the converted given frame of video data stored in the frame memory when the video display has been switched to the second operational mode.

17. A method for reducing power consumption in a video display system, comprising:

(a) providing a video display for displaying a grey-scale image specified by plural frames of video data, the video display having a first operating mode, and a second operating mode that consumes less power than the first operating mode;

(b) converting a given frame of video data comprising plural sequences of grey-scale image data into corresponding two-state image data; and

(c) controlling the video display to switch from the first operating mode to the second operating mode in response to non-receipt of a predetermined number of consecutive frames of the video data for a predetermined period of time, in which the control means controls the video display to display a two-state image specified by the converted given frame of video data.

18. A method as in claim 17, in which step (c) comprises controlling the video display to switch from the first operating mode to the second operating mode in response to non-receipt of two consecutive frames of video data.

19. A method as in claim 17, in which:

the video display receives update pulses together with said frames of video data respectively; and

step (c) comprises controlling the video display means to switch from the first operating mode to the second operating mode in response to non-receipt of a predetermined number of consecutive update pulses.

20. A method as in claim 17, in which:

the video display comprises a frame memory for storing a frame of video data including the converted given frame of input data; and

step (c) comprises controlling the video display to repetitively read out and display the converted given frame of video data stored in the frame memory when the video display has been switched to the second operational mode.

21. A video display system, comprising:

a video display for displaying a grey-scale image specified by plural frames of video data, said video display having a first operating mode and a second operating mode consuming less power than the first operating mode;

a conversion means for converting a given frame of video data comprising plural sequences of N bit per pixel image data into corresponding one bit per pixel image data, wherein N is greater than one; and

control means for controlling the video display to switch from the first operating mode to the second operating mode in response to non-receipt of a predetermined number of consecutive frames of the video data for a predetermined period of time, in which the control means controls the video display to display a one bit per pixel image specified by the converted given frame of video data.

22. A method for reducing power consumption in a video display system, comprising:

(a) providing a video display for displaying an N bit per pixel image specified by plural frames of video data, the video display having a first operating mode, and a second operating mode that consumes less power than the first operating mode;

(b) converting a given frame of video data comprising plural sequences of N bit per pixel image data into corresponding one bit per pixel image data, wherein N is greater than one; and

(c) controlling the video display to switch from the first operating mode to the second operating mode in response to non-receipt of a predetermined number of consecutive frames of the video data for a predetermined period of time, in which the control means controls the video display to display a one bit per pixel image specified by the converted given frame of video data.