Backlight driver, backlight device including the same, and operating method of the backlight device

Patent metadata

Field	Value
Publication number	US-11615752-B2
Application number	US-202117244369-A
Country	US
Kind code	B2
Filing date	Apr 29, 2021
Priority date	May 7, 2020
Publication date	Mar 28, 2023
Grant date	Mar 28, 2023

Abstract

A backlight device includes LED elements divided into dimming groups; a panel driver configured to output a reference current for driving the LED elements; and pixel circuits, each of which is connected to the panel driver through a common line and is respectively configured to drive first LED elements comprised in a corresponding dimming group. Each of the pixel circuits is configured to: in a first period of a frame period, obtain a reference voltage based on the reference current and store the reference voltage, in a second period of the frame period, obtain luminance data of an image displayed by the corresponding dimming group, and in a third period of the frame period, drive the first LED elements during a light emitting time corresponding to the luminance data obtained in the second period using the reference voltage stored in the first period.

First claim

What is claimed is:

1. A backlight device comprising:
a plurality of light emitting diode (LED) elements divided into a plurality of dimming groups;
a panel driver configured to output a reference current for driving the plurality of LED elements; and
a plurality of pixel circuits, each of which is connected to the panel driver through a common line and is respectively configured to drive first LED elements comprised in a corresponding dimming group among the plurality of dimming groups,
wherein each of the plurality of pixel circuits is configured to:
in a first period of a frame period, obtain a reference voltage based on the reference current and store the reference voltage,
in a second period of the frame period, obtain luminance data of an image displayed by the corresponding dimming group, and
in a third period of the frame period, drive the first LED elements during a light emitting time corresponding to the luminance data obtained in the second period using the reference voltage stored in the first period.

2. The backlight device of claim 1 , wherein the first period of the frame period comprises a plurality of sampling periods respectively corresponding to the plurality of pixel circuits, and
wherein each of the plurality of pixel circuits is configured to obtain the reference voltage and store the reference voltage in a corresponding sampling period among the plurality of sampling periods.

3. The backlight device of claim 2 , wherein the panel driver comprises a current source configured to output the reference current in the first period of the frame period; and
a current writing controller configured to output a plurality of writing signals corresponding to the plurality of pixel circuits respectively indicating the plurality of sampling periods, and
wherein each of the plurality of pixel circuits is configured to obtain the reference voltage based on a corresponding writing signal among the plurality of writing signals.

4. The backlight device of claim 3 , wherein each of the plurality of pixel circuits comprises a conversion circuit configured to obtain the reference voltage by converting the reference current into the reference voltage based on the corresponding writing signal;
a sample and hold circuit configured to store the reference voltage; and
LED drivers configured to respectively drive the first LED elements using the reference voltage stored by the sample and hold circuit.

5. The backlight device of claim 4 , wherein the conversion circuit comprises a delay element configured to delay the corresponding writing signal, and
wherein the conversion circuit is configured to convert the reference current into the reference voltage based on a delayed writing signal provided by the conversion circuit.

6. The backlight device of claim 4 , wherein the sample and hold circuit comprises a first sample and hold circuit; and a second sample and hold circuit, and
wherein the LED drivers comprise:
first LED drivers configured to drive LED elements of a first group among the first LED elements based on the reference voltage stored in the first sample and hold circuit; and
second LED drivers configured to drive LED elements of a second group among the first LED elements based on the reference voltage stored in the second sample and hold circuit.

7. The backlight device of claim 4 , wherein each of the plurality of pixel circuits comprises a switching circuit comprising switches configured to connect the first LED elements to the LED drivers; and
a switching controller configured to obtain the luminance data and control the switching circuit to drive the switches in accordance with the light emitting time corresponding to the luminance data.

8. The backlight device of claim 7 , wherein the luminance data comprises pulse width modulation (PWM) data having a width corresponding to a luminance, and
wherein the switching controller is configured to drive the first LED elements during the light emitting time corresponding to the width of the PWM data.

9. The backlight device of claim 1 , wherein the panel driver comprises a current source controller configured to control a current source to change a magnitude of the reference current, and
wherein the current source controller is configured to select the magnitude of the reference current based on the luminance data and control the current source to output the reference current of the selected magnitude.

10. The backlight device of claim 1 , wherein a portion of the first period overlaps with the second period.

11. The backlight device of claim 1 , wherein a portion of the first period overlaps with the third period.

12. The backlight device of claim 1 , wherein the plurality of pixel circuits are configured to:
for each of a preset number of frame periods, sequentially obtain the reference voltage based on the reference current and store the reference voltage in the first period, and
for every frame period, obtain the luminance data in the second period, and drive, in the third period, the first LED elements during the light emitting time corresponding to the luminance data obtained in the second period.

13. The backlight device of claim 12 , wherein first pixel circuits among the plurality of pixel circuits are configured to, for each of the preset number of frame periods with respect to a first frame period, sequentially obtain the reference voltage based on the reference current and store the reference voltage in the first period, and
wherein second pixel circuits among the plurality of pixel circuits are configured to, for each of the preset number of frame periods based on a second frame period, sequentially obtain the reference voltage based on the reference current and store the reference voltage in the first period.

14. The backlight device of claim 1 , wherein the plurality of pixel circuits are configured to, based on luminance data of a previous frame and a current frame having a common value, omit an operation of obtaining the luminance data in the second period.

15. A backlight driver configured to operate in units of a frame period comprising a charging period and a display period, the backlight driver comprising:
a first pixel circuit configured to drive first light emitting diode (LED) elements corresponding to a first region of a display panel;
a second pixel circuit configured to drive second LED elements corresponding to a second region of the display panel; and
a panel driver comprising a current source connected in parallel with the first pixel circuit and the second pixel circuit, and configured to provide a reference current to the first pixel circuit and the second pixel circuit based on the current source,
wherein the first pixel circuit is configured to:
in a first sampling period of the charging period, obtain a reference voltage based on the reference current and store the reference voltage, and
in the display period, drive the first LED elements based on first luminance data representing a luminance corresponding to the first region, and

wherein the second pixel circuit is configured to:
in a second sampling period of the charging period, obtain the reference voltage based on the reference current and store the reference voltage, and
in the display period, drive the second LED elements based on second luminance data representing a luminance corresponding to the second region.

16. The backlight driver of claim 15 , wherein the panel driver is configured to, output a first writing signal indicating the first sampling period and a second writing signal indicating the second

Assignees

• Samsung Electronics Co Ltd

Inventors

• Lee Changju
• Kwon Yongil
• Choi Yoon-Kyung
• Huh Junho

Classifications

• H10W90/00

  Package configurations · CPC title

• G09G2320/064

  by time modulation of the brightness of the illumination source · CPC title

• G09G3/32

  semiconductive, e.g. using light-emitting diodes [LED] · CPC title

• G09G2320/062

  Adjustment of illumination source parameters · CPC title

• G09G3/3406 Primary

  Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336) · CPC title