Browse Prior Art Database

Liquid Crystal Display Backlight Brightness Control

IP.com Disclosure Number: IPCOM000118123D
Original Publication Date: 1996-Sep-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 93K

Publishing Venue

IBM

Related People

Nagai, M: AUTHOR [+2]

Abstract

Disclosed is a method for controlling the brightness of a Liquid Crystal Display (LCD) backlight. The method can provide both an easy one action human interface and higher complex functions of a power management system.

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This is the abbreviated version, containing approximately 52% of the total text.

Liquid Crystal Display Backlight Brightness Control

      Disclosed is a method for controlling the brightness of a
Liquid Crystal Display (LCD) backlight.  The method can provide both
an easy one action human interface and higher complex functions of a
power management system.

      Currently, an LCD screen with a backlight system is used in
many portable information handling devices (e.g., notebook
computers).  The major backlight system uses a discharge lamp as its
light source, and such a kind of lamp requires a DC/AC inverter
unit.  Fig. 1 shows an example diagram of the LCD modules.  Almost
all of the color portable devices have some kind of dimming function
of the  brightness of the backlight by changing the lamp current.
Following are two conventional implementations of the dimming
function:
  1.  The simplest way to control the brightness of the backlight
       is to use a variable register with a sliding or rotating
       knob on an inverter as shown in Fig. 2.  The user can
       easily change the brightness of the backlight by tuning
       the mechanical knob.  This method is very easy for a one
       action human interface, but is not suitable for a higher
       function power management system which wants to control
       the brightness according to many situations to save the
       power consumption of the battery.
  2.  Another way is to supply some signal to the inverter
       which is generated by a system unit as shown in Fig. 3
       (e.g., Analog continuous voltage generated by Digital
       to Analog (D/A) converter).  This method is better for
       a power management system because the system takes control
       of the bri...