Browse Prior Art Database

Display Power Management

IP.com Disclosure Number: IPCOM000115147D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 119K

Publishing Venue

IBM

Related People

Hopkins, K: AUTHOR

Abstract

Modern computer displays employing both Cathode Ray Tubes (CRTs) and solid state devices such as liquid crystal panels can be operated with considerable advantage in power consumption and operating life under the control of a power management system which monitors computer activity and adjusts the power supply to the display accordingly. Some computers employ a display protocol, such as the VESA Display Power Management Signalling (DPMS) protocol, to present and interpret activity requiring display power management, whilst others monitor activity of particular components, such as the keyboards and the mouse, to develop the necessary data.

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Display Power Management

      Modern computer displays employing both Cathode Ray Tubes
(CRTs) and solid state devices such as liquid crystal panels can be
operated with considerable advantage in power consumption and
operating life under the control of a power management system which
monitors computer activity and adjusts the power supply to the
display accordingly.  Some computers employ a display protocol, such
as the VESA Display Power Management Signalling (DPMS) protocol, to
present and interpret activity requiring display power management,
whilst others monitor activity of particular components, such as the
keyboards and the mouse, to develop the necessary data.

      The described arrangement, which may be conveniently
implemented using a gate array such as XILINX 3042 100PQFP, allows
power management from either VESA DPMS or Keyboard/Mouse activity
without user intervention.  It will also prioritise the power
management mode if both options are in use.  Since most display
systems for personal computers use Hsync and Vsync then these signals
can be used for power management of the display under control of some
software application running on the system unit.  However, many
desktop computers do not have operating systems that support DPMS, so
monitoring of the Keyboard and mouse can provide an alternative
method of power management.

      The arrangement will default to Keyboard/mouse clock sampling.
The protocol for determining power management state is shown in Fig.
2.  From Fig. 2, it can be seen that it is necessary to set the VESA
mode active or inactive depending on whether Keyboard/mouse and/or
VESA signalling is in operation.

      It is necessary to enable on board power management using the
Keyboard/mouse interface when not in VESA mode.  Referring to Figure
1 the circuitry to achieve this includes a 16-bit counter, an edge
detector, a count decoder and a state machine.  Operation is as
follows:  The 16-bit counter is clocked by a 2Hz oscillator which is
controlled by the state machine.  The output of the counter is then
decoded to give a realtime output in minutes.  The three outputs are
determined by the system specification, and are 29min, 30min and 45
min.  These correspond to: backlight off warning, backlight off and
soft power down respectively.  The state machine then signals the I/O
logic accordingly.  An edge detector detects an edge on the
Keyboard/mouse clock and signals the state machine which will then
output to the I/O controller and the Counter.

Power Management Using Hsync/Vsync DPMS

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