Browse Prior Art Database

No Screen Garbage Power On/Off Method of Backlight Liquid Crystal Display

IP.com Disclosure Number: IPCOM000114294D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 4 page(s) / 75K

Publishing Venue

IBM

Related People

Itoh, H: AUTHOR [+2]

Abstract

Disclosed is Backlight Liquid Crystal Display (LCD) which has No Screen garbage power on/off method. At first "Screen garbage" is explained as follows: 1. As for Power-on sequence, Backlight starts lightening earlier before completion of driving LCD for 1st frame, or 2. As for Power-off sequence, Backlight keeps lightening continuously after termination of LCD drive.

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This is the abbreviated version, containing approximately 67% of the total text.

No Screen Garbage Power On/Off Method of Backlight Liquid Crystal
Display

      Disclosed is Backlight Liquid Crystal Display (LCD) which has
No Screen garbage power on/off method.  At first "Screen garbage" is
explained as follows:
  1.  As for Power-on sequence, Backlight starts lightening earlier
       before completion of driving LCD for 1st frame, or
  2.  As for Power-off sequence, Backlight keeps lightening
       continuously after termination of LCD drive.

      These 1) and 2) cases bring Screen garbage on Front Of Screen
(FOS), which means Backlight comes through incompletely driven LCD.

      In order to prevent this Screen garbage, relationship between
Vcc (power for LCD drive circuit) and Vbl (power for Backlight) in
the following Fig. 1 is used to be fine tuned in conventional method.
But this conventional method is very difficult to be tuned and needs
much time to arrange this relationship.  Fig. 1 shows a Conventional
method circuit of LCD with Backlight.  Fig. 2 shows Relationship
Timing between Vcc and Vbl at power On/Off of conventional method.

      By the way, in this No Screen garbage method, we don't care
about relationship between Vcc and Vbl On/Off timing, we care only
Vcc Power On/Off timing.  At power on sequence, Backlight starts
lightening after completion of driving LCD for 1st frame.  Because in
Fig. 3, by 1)addition of "Backlight-ON delay timer circuit" to
conventional circuit, there is a valid delay...