Display unit and backlight unit

• US 7,511,695 B2
• Filed: 07/08/2005
• Issued: 03/31/2009
• Est. Priority Date: 07/12/2004
• Status: Expired due to Fees

• Current Assignee: Saturn Licensing LLC (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Kikuchi, Kenichi, Ichikawa, Hiroaki, Furukawa, Norimasa
• Primary Examiner(s): Abdulselam; Abbas I
• Application Number:
  US11/176,391
• Publication Number:
  US 20060022616A1
• Time in Patent Office: 1,362 Days
• Field of Search: 345/102, 345/22, 345/76, 345/77, 345/83, 345/88, 345/600, 315/309, 315/291, 349/61, 349/70, 362/800, 348/471, 348/566
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• 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

Abstract

The screen is exempt from variation in brightness due to uneven temperature distribution.

The color liquid crystal display unit has a color display panel of transmissive type and a backlight unit placed behind the color display panel. The backlight unit has a plurality of LEDs connected in series, the drive unit to drive the LEDs in correspondence with the LEDs, and the temperature sensor to detect the temperature of LEDs. The groups of LEDs are arranged in regions where the display unit has the same temperature. The drive unit controls current to be supplied to LEDs in response to temperature detected by the temperature sensor so that the LEDs retain the constant brightness even when the LEDs fluctuate in temperature.

Claims

1. A backlight unit installed in the back of a display unit, comprising:

lighting units, each lighting unit comprising;

red, green, and blue light emitting diodes connected in series, and

a temperature detecting unit to detect the temperature of the lighting unit, and

a drive unit to control current supplied to the light emitting diodes according to the temperature of the lighting unit, so that each lighting unit keeps a uniform brightness even though each lighting unit changes in temperature, to adjust current to be supplied to the light emitting diodes by means of pulse width modulation, so as to keep at least the brightness of light emitted from each lighting unit uniform, to control the peak value of the current to be supplied to the light emitting diodes, so that the resolution of pulse width is the same for the red, green, and blue light emitting diodes, and to adjust the peak value of current to be supplied to the light emitting diodes in response to the detected temperature,

wherein the lighting units are arranged in various positions at which the light emitting diodes keep a prescribed temperature.

2. The backlight unit as defined in claim 1, wherein the drive unit controls current supplied to the light emitting diodes, so that each lighting unit keeps a uniform brightness as well as a uniform chromaticity even though each lighting unit changes in temperature.

3. The backlight unit as defined in claim 1, wherein the lighting units are placed behind the display unit such that the light emitting diodes are connected in series and arranged in the horizontal direction of the screen.

4. The backlight unit as defined in claim 1, wherein the temperature detecting unit detects the temperature of one of the lighting units having a malfunctioning temperature sensor according to information from a memory which previously stored the temperature of the lighting unit having the malfunctioning temperature sensor in response to the temperature of one of the lighting units at the position where a temperature sensor is installed.

5. The backlight unit as defined in claim 1, further comprising a light detecting sensor to detect the brightness of light emitted from the light emitting diodes in each lighting unit, wherein the drive unit adjusts current supplied to the light emitting diodes so as to keep at least the brightness of light emitted from each lighting unit uniform.

6. A display unit comprising:

a non-luminous screen of transmissive-type,

lighting units, placed behind the screen, each lighting unit comprising;

red, green, and light emitting diodes connected in series, and

a temperature detecting unit to detect the temperature of the lighting unit, and

a drive unit to control current supplied to the light emitting diodes according to the temperature of the lighting unit, so that each lighting unit keeps a uniform brightness even though each lighting unit changes in temperature, to adjust current to be supplied to the light emitting diodes by means of pulse width modulation, so as to keep at least the brightness of light emitted from each lighting unit uniform, to control the peak value of the current to be supplied to the light emitting diodes, so that the resolution of pulse width is the same for the red, green, and blue light emitting diodes, and to adjust the peak value of current to be supplied to the light emitting diodes in response to the detected temperature

wherein the lighting units are arranged in various positions at which the light emitting diodes keep a prescribed temperature.

7. The display unit as defined in claim 6, wherein the drive unit controls current supplied to the light emitting diodes, so that each lighting unit keeps a uniform brightness as well as a uniform chromaticity even though each lighting unit changes in temperature.

8. The display unit as defined in claim 6, wherein the lighting units are placed behind the display unit such that the light emitting diodes are connected in series and arranged in the horizontal direction of the screen.

9. The display unit as defined in claim 6, wherein the temperature detecting unit detects the temperature of one of the lighting units having a malfunctioning temperature sensor according to information from a memory which previously stored the temperature of the lighting unit having the malfunctioning temperature sensor in response to the temperature of one of the lighting units at the position where temperature sensor is installed.

10. The display unit as defined in claim 6, further comprising a light detecting sensor to detect at least the brightness of light emitted from the light emitting diodes in each lighting unit, wherein the drive unit adjusts current to be supplied to the light emitting diodes so as to keep at least the brightness of light emitted from each lighting unit uniform.

11. The display unit as defined in claim 6, which further comprises an optical system that uniformly mixes the colors of light emitted from each light emitting diode in each lighting unit, and wherein the drive unit acquires as a representative value the brightness or chromaticity detected by the light detecting sensor and adjusts current to be supplied to each light emitting diode in each lighting unit so that the lighting unit changes uniformly as a whole and the light emitted from each lighting unit remains constant in brightness or chromaticity.