Temperature detection circuit for display device

Patent metadata

Field	Value
Publication number	US-2018196301-A1
Application number	US-201815866067-A
Country	US
Kind code	A1
Filing date	Jan 9, 2018
Priority date	Jan 12, 2017
Publication date	Jul 12, 2018
Grant date	—

Abstract

A liquid crystal display device includes an upper substrate, a lower substrate including a data line and a gate line insulated from the data line, a liquid crystal layer between the lower substrate and the upper substrate, a current sensing unit which detects a data current based on a data signal applied to the data line so as to detect a change in a liquid crystal capacitance of the liquid crystal layer, a rectifying amplifier which rectifies or amplifies the detected data current so as to generate and output a rectified signal, a pulse generator which generates a sensing pulse by comparing the rectified signal with a reference voltage, and a duty width detector which detects a duty width of the sensing pulse generated by the pulse generator where the reference voltage is set based on a voltage difference between data signals successively applied to the data line.

First claim

What is claimed is:

1 . A liquid crystal display device comprising:
an upper substrate; a lower substrate opposing the upper substrate and comprising a data line and a gate line insulated from the data line; a liquid crystal layer between the lower substrate and the upper substrate; a current sensing unit which detects a data current based on a data signal applied to the data line so as to detect a change in a liquid crystal capacitance of the liquid crystal layer; a rectifying amplifier which rectifies or amplifies the detected data current so as to generate and output a rectified signal; a pulse generator which generates a sensing pulse by comparing the rectified signal with a reference voltage; and a duty width detector which detects a duty width of the sensing pulse generated by the pulse generator, wherein the reference voltage is set based on a voltage difference between data signals successively applied to the data line.

2 . The liquid crystal display device as claimed in claim 1 , further comprising a temperature calculator which calculates a temperature of the liquid crystal layer based on the duty width of the sensing pulse.

3 . The liquid crystal display device as claimed in claim 1 , wherein the reference voltage is proportional to a voltage difference between the data signal applied to the data line and a data signal applied during a previous horizontal synchronization period.

4 . The liquid crystal display device as claimed in claim 3 , wherein the reference voltage has a voltage value between a lowest voltage and a highest voltage of the rectified signal corresponding to the data current during a horizontal synchronization period.

5 . The liquid crystal display device as claimed in claim 4 , wherein the pulse generator generates a plurality of sensing pulses having a substantially same duty width when a temperature of the liquid crystal layer is constant.

6 . The liquid crystal display device as claimed in claim 1 , wherein the sensing pulse has a narrower pulse width as a temperature of the liquid crystal layer rises.

7 . The liquid crystal display device as claimed in claim 1 , wherein the current sensing unit comprises at least one of a sensing resistor, a photo-coupler and a current mirror circuit.

8 . The liquid crystal display device as claimed in claim 1 , further comprising data lines,
wherein the current sensing unit is separately connected to each of the data lines and detects the data current for each of the data lines.

9 . The liquid crystal display device as claimed in claim 8 , wherein the current sensing unit is integrated with the data driver which applies the data signal to the data line.

10 . The liquid crystal display device as claimed in claim 1 , further comprising a plurality of data lines,
wherein the current sensing unit is connected to the plurality of data lines and detects the data current by summing the data currents applied to the plurality of data lines.

11 . The liquid crystal display device as claimed in claim 1 , wherein the rectifying amplifier separates and rectifies a positive current and a negative current of the data current.

12 . A liquid crystal display device comprising:
a display panel; a pixel on the display panel, the pixel comprising a liquid crystal layer having a liquid crystal capacitance which varies depending on a temperature change; a data driver which applies a data signal to the pixel and a gate driver which applies a gate signal to the pixel; a timing controller which controls the data driver and the gate driver; and a temperature sensor which detects a temperature of the liquid crystal layer, and comprises:
a current sensing unit which detects a data current generated by the data signal;
a rectifying amplifier which rectifies or amplifies the detected data current so as to output a rectified signal;
a reference voltage conversion unit which sets a reference voltage based on a voltage difference between data signals successively applied to the data line;
a pulse generator which compares the rectified signal with the reference voltage so as to generate a sensing pulse;
a duty width detector which detects a duty width of the sensing pulse output from the pulse generator; and
a temperature calculator which determines the temperature of the liquid crystal layer based on the duty width,
wherein the timing controller corrects an input image data based on the temperature of the liquid crystal layer output from the temperature sensor.

13 . The liquid crystal display device as claimed in claim 12 , wherein the timing controller receives red, green and blue image data and corrects the red, green and blue image data with a correction gamma value, and
the timing controller corrects the red, green and blue image data by applying a less correction gamma value as the sensed temperature is higher.

14 . The liquid crystal display device as claimed in claim 13 , wherein the timing controller applies different correction gamma values for respective colors to correct light emission characteristics of red, green and blue pixels.

15 . The liquid crystal display device as claimed in claim 12 , wherein the timing controller applies a correction value so that an image data of a current frame increases from an image data of a previous frame, and
the correction value when the sensed temperature is relatively high is less than the correction value when the sensed temperature is relatively low.

16 . The liquid crystal display device as claimed in claim 12 , wherein the timing controller increases an application period of the gate signal depending on a degree of separation between the pixel to which the gate signal is applied and the data driver.

17 . The liquid crystal display device as claimed in claim 16 , wherein the application period of the gate signal by the timing controller is shorter when the sensed temperature is relatively high as compared to the application period of the gate signal when the sensed temperature is relatively low.

18 . The liquid crystal display device as claimed in claim 12 , wherein the gate driver outputs a plurality of gate signals overlapping one data signal.

19 . The liquid crystal display device as claimed in claim 18 , wherein one of the plurality of gate signals overlaps a plurality of data signals.

20 . The liquid crystal display device as claimed in claim 19 , wherein the reference voltage conversion unit varies the reference voltage according to a number of the plurality of gate signals overlapping the data signal.

Assignees

• Samsung Display Co Ltd

Inventors

• Choi Minsoo
• Moon Seunghwan
• Shin Okkwon
• Lee Junpyo

Classifications

• G09G2320/0666

  for control of colour parameters, e.g. colour temperature · CPC title

• G02F1/133382 Primary

  Heating or cooling of liquid crystal cells other than for activation, e.g. circuits or arrangements for temperature control, stabilisation or uniform distribution over the cell · CPC title

• G09G2320/041

  Temperature compensation · CPC title

• G09G2310/0221

  with use of split matrices (G09G3/3644 and G09G3/3666 take precedence) · CPC title

• G09G2360/16

  Calculation or use of calculated indices related to luminance levels in display data · CPC title