EP-3965099-B1 - DISPLAY DEVICE

EP3965099B1EP 3965099 B1EP3965099 B1EP 3965099B1EP-3965099-B1

Inventors

PARK, JUNG KOOK
PARK, DONG WAN
KANG, DO HYUN

Dates

Publication Date: 20260506
Application Date: 20210901

Claims (12)

A method of operating a display device, the display device comprising a plurality of pixels, each pixel comprising an organic light emitting diode (OLED), a data driver, a scan driver, and a timing controller, the timing controller comprising a luminance controller, a plurality of data lines connecting the data driver to respective pixels, a plurality of scan lines connecting the scan driver to respective pixels and a plurality of emission lines connecting the scan driver and respective pixels and the display device having at least a first luminance range and a second luminance range, wherein the luminance of the first luminance range is higher than the luminance of the second luminance range, the method comprising: supplying to the scan driver by the timing controller an emission duty control signal (EDCS); supplying to the pixels by the scan driver an emission control signal with an off-duty number and an off-duty ratio, wherein the off-duty number is the number of pulses of the emission control signal included in one frame and the off-duty ratio is a ratio of a period in which a pixel is turned off to one frame period (1F) including the period in which the pixel is turned off and the period in which the pixel is turned on; supplying to the data driver by the timing controller a respective data signal for each pixel; receiving by the timing controller a control signal from an outside source for setting a dimming mode, according to the dimming mode, operating the display in one of: a first dimming range, corresponding to the first luminance range or a second dimming range, corresponding to the second luminance range, wherein operating in the second dimming range comprise one of: operating in a boundary area of the second dimming range which is adjacent to the first dimming range or operating in the second dimming range outside of the boundary area; supplying, by the data driver, when operating in the boundary area, a data signal value having a constant value to each pixel such that a reference luminance of each said pixel is maintained at a first constant luminance value, wherein the first constant luminance value is the luminance of the pixel during an emission period in which the pixel emits light according to the data signal value and incrementally increasing by the luminance controller, when operating in the boundary area, the off-duty number over a plurality of frames to decrease the emission luminance of each pixel.
A method according to claim 1, wherein the off-duty number is increased by two per frame in the boundary area.
A method according to claim 1 or claim 2, wherein the off-duty number is 1 at a start point of the boundary area and 32 at an end point of the boundary area, and wherein the off-duty number is 1 per one frame in the first dimming range, and 32 per one frame in the second dimming range except for the boundary area.
A method according to any preceding claim, wherein the off-duty ratio of the emission control signal is maintained at a constant value in the boundary area.
A method according to any of claims 1 to 3, wherein in the boundary area, when a change in the off-duty number is eight or more, a section of the emission control signal in which the off-duty ratio is gradually increased is included.
A method according to claim 5, wherein the off-duty ratio is increased in an order of 2 percentages (%), 5%, 10%, and 15% when the off-duty number is 16.
A method according to any preceding claim, wherein in the boundary area, when a change in the off-duty number is eight or more, including a section of the emission control signal in which the off-duty number has an intermediate number less than the change in the off-duty number between a section in which the change of eight or more occurs such that the off-duty number is changed less than eight at a time.
A method according to claim 7, wherein the off-duty number is increased by 1 at a time in a section of the emission control signal in which the off-duty number increases from 16 to 32.
A method according to any preceding claim, comprising: maintaining in the second dimming range except for the boundary area, the reference luminance as the first constant luminance value, and incrementally increasing the off-duty ratio over a plurality of frames.
A method according to any preceding claim, wherein the first luminance range is from 350 nits to 100 nits, and the second luminance range is from 100 nits to 2 nits.
A method according to claim 10, wherein the first luminance range includes an ultra-high luminance range corresponding to about 350 nits to about 265 nits, a high luminance range corresponding to about 265 nits to about 162 nits, and a medium luminance range corresponding to about 162 nits to about 100 nits, and wherein in the ultra-high luminance range, the reference luminance non-linearly decreases to correspond to the dimming luminance, and the off-duty ratio is maintained as a first off-duty ratio.
A display device comprising a plurality of pixels, each pixel comprising an organic light emitting diode (OLED), a data driver, a scan driver, a timing controller, the timing controller comprising a luminance controller, a plurality of data lines connecting the data driver to respective pixels, a plurality of scan lines connecting the scan driver to respective pixels and a plurality of emission lines connecting the scan driver and respective pixels, wherein the luminance controller is configured to: provide at least a first luminance range and a second luminance range, wherein the luminance of the first luminance range is higher than the luminance of the second luminance range; wherein the timing controller is configured to: receive a control signal from an outside source for setting a dimming mode, and, according to the dimming mode, operate the display in one of: a first dimming range, corresponding to the first luminance range or a second dimming range, corresponding to the second luminance range, wherein operating in the second dimming range comprise one of: operating in a boundary area of the second dimming range which is adjacent to the first dimming range or operating in the second dimming range outside of the boundary area; supply to the scan driver an emission duty control signal (EDCS); and supply to the data driver a respective data signal for each pixel; wherein the scan driver is configured to: supply to the pixels an emission control signal with an off-duty number and an off-duty ratio, wherein the off-duty number is the number of pulses of the emission control signal included in one frame and the off-duty ratio is a ratio of a period in which a pixel is turned off to one frame period (1F) including the period in which the pixel is turned off and the period in which the pixel is turned on wherein the data driver is configured to: supply, when operating in the boundary area, a data signal value having a constant value to each pixel such that a reference luminance of each said pixel is maintained at a first constant luminance value, wherein the first constant luminance value is the luminance of the pixel during an emission period in which the pixel emits light according to the data signal value wherein the luminance controller is configured to: incrementally increase , when operating in the boundary area, the off-duty number over a plurality of frames to decrease the emission luminance of each pixel.

Description

Technical Field The disclosure relates to a display device. Discussion of the Related Art As an information technology is developed, importance of a display device that is a connection medium between a user and information is emphasized. In response to this, use of display devices such as a liquid crystal display device and an organic light emitting device is increasing. Among the display devices, an organic light emitting display device displays an image using an organic light emitting diode that generates light by recombination of an electron and a hole. Such an organic light emitting display device has an advantage that the organic light emitting display device has a fast response speed and the organic light emitting display device is driven with low power consumption. However, compared to a liquid crystal display device that may control an overall luminance by controlling an amount light incident on a liquid crystal display panel by adjusting a magnitude of a voltage applied to a back light unit, the organic light emitting display device is a display device using light emission of an organic light emitting layer. Therefore, implementing dimming of controlling the overall luminance in the organic light emitting display device is difficult. Accordingly, the organic light emitting display device implements dimming of a display panel through a smart dimming method that sets a lower luminance level using an arithmetic expression by a gamma curve for a luminance for grayscale based on a maximum luminance, an AMOLED impulsive driving ("AID") method that performs dimming by adjusting on/off-duty of an emission control signal by applying an impulse driving method, and/or the like. US 2015/097764 and US 2018/151132 both provide disclosures related to display devices. SUMMARY According to a first aspect, there is provided a method of operating a display device according to claim 1. According to a second aspect, there is provide a display device according to claim 12. Details of embodiments are provided in the dependent claims. Human vision tends to better recognize a change in a low luminance area than in a high luminance area. During dimming of the organic light emitting display device, when the AID method is applied to the low luminance area, a problem that a flicker phenomenon is visible when the number of cycles (that is, the off-duty number of the emission control signal included in one frame) of the AID is low may occur. An aspect to be solved by the disclosure is to provide a display device capable of reducing a flicker phenomenon when an AID method is applied in a low luminance area. However, the aspect of the disclosure according to the invention is not limited to the above-described aspects, and may be variously expanded without departing from the scope of the claims. According to an aspect of the disclosure for solving the above-described aspect, a display device includes at least a first luminance range and a second luminance range which includes a luminance different from the first luminance range. In a boundary area of a second dimming range corresponding to the second luminance range and which is adjacent to a first dimming range corresponding to the first luminance range, a reference luminance emitted from a pixel is maintained as a first constant luminance value, and an off-duty number, which is the number of periods in which the pixel is turned off during one frame, is gradually increased by an emission control signal. The off-duty number may be the number of pulses of the emission control signal included in one frame. The off-duty number may increase by twice per frame in the boundary area. The off-duty number may be 1 at a start point of the boundary area and 32 at an end point of the boundary area. An off-duty ratio of the emission control signal may be maintained at a constant value in the boundary area. In the boundary area, when a change in the off-duty number is eight or more, a section in which the off-duty ratio gradually increases may be included. The off-duty ratio may increase in an order of about 2 percentages (%), about 5%, about 10%, and about 15% when the off-duty number is 16. In the boundary area, when a change in the off-duty number is eight or more, a section in which the off-duty number has an intermediate number may be further included between a section in which the change of eight or more occurs such that the off-duty number is changed less than eight at a time. The off-duty number may increase by 1 at a time in a section in which the off-duty number increases from 16 to 32. The off-duty number may be 1 per one frame in the first dimming range, and 32 per one frame in the second dimming range except for the boundary area. In the second dimming range except for the boundary area, the reference luminance may be maintained as the first constant luminance value, and the off-duty ratio may be gradually increased. The first constant luminance value may be in a range of about 90 t