Light source device

• US 20060055660A1
• Filed: 09/08/2005
• Published: 03/16/2006
• Est. Priority Date: 09/13/2004
• Status: Abandoned Application

• Current Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Original Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Inventors: Teranishi, Kentaro
• Application Number:
  US11/220,847
• Publication Number:
  US 20060055660A1
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A light source device includes lamp-type light sources which respectively illuminate display areas obtained by dividing a screen of a display panel, and a backlight drive circuit which drives the lamp-type light sources. Particularly, the backlight drive circuit includes a dimmer control circuit which generates dimmer control signals having a common duty ratio which is changed to define ON time for each preset period of time and being set to different phases, and driving units which respectively drive the lamp-type light sources according to the dimmer control signals generated from the dimmer control circuit.

Claims

1. A light source device comprising:

a plurality of lamp-type light sources which respectively illuminate display areas obtained by dividing a screen of a display panel; and

a light source driving circuit which drives said lamp-type light sources;

wherein said light source driving circuit includes a dimmer control circuit which generates dimmer control signals having a common duty ratio which is changed to define an ON time for each preset period of time, and being set to different phases, and a plurality of driving units which respectively drive said lamp-type light sources according to the dimmer control signals generated from said dimmer control circuit.

2. The light source device according to claim 1, wherein said dimmer control circuit includes a duty ratio detector which detects a duty ratio of a dimmer signal supplied externally and outputs a pulse width modulation signal of a duty ratio identical to the result of detection, and a plurality of phase controllers which change a phase of the pulse width modulation signal output from the duty ratio detector to attain the dimmer control signals.

3. The light source device according to claim 2, wherein said pulse width modulation signal has the same frequency as that of the dimmer signal.

4. The light source device according to claim 1, wherein different phase differences of the dimmer control signals are determined based on distances between said lamp-type light sources.

5. The light source device according to claim 2, wherein each of said driving units includes a voltage converter which converts the dimmer control signal from a corresponding one of said phase controllers to a drive voltage for a corresponding one of said lamp-type light sources.

6. The light source device according to claim 1, wherein each of said lamp-type light sources includes at least one cold cathode fluorescent tube.

7. The light source device according to claim 1, wherein the screen of said display panel includes a plurality of OCB liquid crystal pixels.

8. The light source device according to claim 2, wherein different phase differences of the dimmer control signals are determined based on distances between said lamp-type light sources.