Patent Grant
11532279
Example embodiments of the present disclosure relate to a display device, and more particularly to an organic light emitting diode (OLED) display device performing low frequency driving.
Reduction of power consumption is desirable in an organic light emitting diode (OLED) display device employed in a portable device, such as a smartphone, a tablet computer, etc. Recently, in order to reduce the power consumption of the OLED display device, a low frequency driving technique which drives or refreshes a display panel at a frequency lower than an input frame frequency of input image data has been developed.
However, in an OLED display device using the low frequency driving technique, a threshold voltage of a driving transistor of each pixel may be shifted by the low frequency driving. Further, by the threshold voltage shift, luminance of the OLED display device may be deteriorated, and a flicker may occur.
Some example embodiments provide an organic light emitting diode (OLED) display device capable of reducing or preventing luminance deterioration while performing low frequency driving.
According to example embodiments, there is provided an OLED including a display panel including a plurality of pixels each having an OLED, and a panel driver configured to drive the display panel. The panel driver receives input image data at an input frame frequency, and determines whether the input image data represent a still image. When the input image data do not represent the still image, the panel driver drives the display panel at a first output frame frequency substantially equal to the input frame frequency. When the input image data represent the still image, the panel driver drives the display panel at a second output frame frequency lower than the input frame frequency for a low frequency driving time, and drives the display panel at a third output frame frequency higher than the second output frame frequency for a high frequency insertion time after the low frequency driving time. The high frequency insertion time is determined based on at least one of a panel characteristic of the display panel and a representative gray level of the input image data.
In example embodiments, a threshold voltage shift of a plurality of driving transistors included in the plurality of pixels which occurs during the low frequency driving time may be compensated during the high frequency insertion time.
In example embodiments, the third output frame frequency may be lower than or equal to the first output frame frequency.
In example embodiments, the high frequency insertion time may be periodically inserted while the still image represented by the input image data is not changed.
In example embodiments, each of the plurality of pixels may include a driving transistor configured to generate a driving current, a switching transistor configured to transfer a data signal to a source of the driving transistor, a compensating transistor configured to diode-connect the driving transistor, a storage capacitor configured to store the data signal transferred through the switching transistor and the diode-connected driving transistor, a first initializing transistor configured to provide an initialization voltage to the storage capacitor and a gate of the driving transistor in response to an initialization signal, a first emission controlling transistor configured to connect a line of a power supply voltage to the source of the driving transistor in response to an emission control signal, a second emission controlling transistor configured to connect a drain of the driving transistor to the OLED in response to the first scan signal, a second initializing transistor configured to provide the initialization voltage to the OLED in response to the first scan signal. The OLED is configured to emit light based on the driving current. At least first one of the driving transistor, the switching transistor, the compensating transistor, the first initializing transistor, the first emission controlling transistor, the second emission controlling transistor and the second initializing transistor may be implemented with a P-type Metal Oxide Semiconductor (PMOS) transistor, and at least second one of the driving transistor, the switching transistor, the compensating transistor, the first initializing transistor, the first emission controlling transistor, the second emission controlling transistor and the second initializing transistor may be implemented with an N-type Metal Oxide Semiconductor (NMOS) transistor.
In example embodiments, each of the plurality of pixels may include a driving transistor configured to generate a driving current, a first switching transistor configured to transfer a data signal, a storage capacitor configured to store the data signal transferred through the first switching transistor, a second switching transistor configured to connect the storage capacitor and the driving transistor to an initialization line, an emission controlling transistor configured to connect a line of a power supply voltage to the driving transistor, and the OLED configured to emit light based on the driving current. At least first one of the driving transistor, the first switching transistor, the second switching transistor and the emission controlling transistor may be implemented with a PMOS transistor, and at least second one of the driving transistor, the first switching transistor, the second switching transistor and the emission controlling transistor may be implemented with an NMOS transistor.
In example embodiments, the panel driver may include a still image detector configured to determine whether the input image data represent the still image by comparing the input image data in a previous frame and the input image data in a current frame.
In example embodiments, the high frequency insertion time may be determined according to, as the panel characteristic of the display panel, a luminance decrease rate of the display panel during the low frequency driving time.
In example embodiments, the panel driver may include a driving frequency changer comprising a high frequency insertion time storage configured to store the high frequency insertion time that is determined according to a luminance decrease rate of the display panel during the low frequency driving time, and a driving frequency changing unit configured to output output image data at the first output frame frequency when the input image data do not represent the still image, to output the output image data at the second output frame frequency for the low frequency driving time when the input image data represent the still image, and to output the output image data at the third output frame frequency for the high frequency insertion time stored in the high frequency insertion time storage after the low frequency driving time, and a data driver configured to provide data signals to the plurality of pixels based on the output image data.
In example embodiments, the high frequency insertion time may be determined according to, as the representative gray level of the input image data, an average value, a maximum value or a minimum value of gray levels of the input image data.
In example embodiments, the panel driver may include a representative gray level calculating unit configured to calculate the representative gray level of the input image data, a driving frequency changing unit configured to output output image data at the first output frame frequency when the input image data do not represent the still image, to output the output image data at the second output frame frequency for the low frequency driving time when the input image data represent the still image, and to output the output image data at the third output frame frequency for the high frequency insertion time corresponding to the representative gray level calculated by the representative gray level calculating unit after the low frequency driving time, and a data driver configured to provide data signals to the plurality of pixels based on the output image data.
In example embodiments, the driving frequency changing unit may determine the high frequency insertion time as a first time when the representative gray level is within a high gray range, may determine the high frequency insertion time as a second time shorter than the first time when the representative gray level is within a middle gray range, and may determine the high frequency insertion time as a third time longer than the first time when the representative gray level is within a low gray range.
In example embodiments, the panel driver may include a high frequency insertion time storage configured to store a plurality of high frequency insertion times respectively corresponding to a plurality of gray ranges, the plurality of high frequency insertion times being determined according to luminance decrease rates of the display panel corresponding to the plurality of gray ranges during the low frequency driving time, a representative gray level calculating unit configured to calculate the representative gray level of the input image data, a driving frequency changing unit configured to output output image data at the first output frame frequency when the input image data do not represent the still image, to output the output image data at the second output frame frequency for the low frequency driving time when the input image data represent the still image, and to output the output image data at the third output frame frequency for the high frequency insertion time selected according to the representative gray level among the plurality of high frequency insertion times stored in the high frequency insertion time storage after the low frequency driving time, and a data driver configured to provide data signals to the plurality of pixels based on the output image data.
According to example embodiments, there is provided an OLED display device including a display panel including a plurality of pixels each having an OLED, and a panel driver configured to drive the display panel. The panel driver includes a high frequency insertion pattern memory configured to store a high frequency insertion pattern that is determined according to a panel characteristic of the display panel. The panel driver receives input image data at an input frame frequency, and determines whether the input image data represent a still image. When the input image data do not represent the still image, the panel driver drives the display panel at a first output frame frequency substantially equal to the input frame frequency. When the input image data represent the still image, the panel driver drives the display panel at a second output frame frequency lower than the input frame frequency for a low frequency driving time, and drives the display panel based on the high frequency insertion pattern after the low frequency driving time.
In example embodiments, a threshold voltage shift of a plurality of driving transistors included in the plurality of pixels which occurs during the low frequency driving time may be compensated while the display panel is driven based on the high frequency insertion pattern.
In example embodiments, the high frequency insertion pattern stored in the high frequency insertion pattern memory may represent at least one third output frame frequency higher than the second output frame frequency, and a number of frames for the third output frame frequency. After the low frequency driving time, the panel driver may drive the display panel at the third output frame frequency for a time corresponding to the number of frames based on the high frequency insertion pattern.
In example embodiments, the third output frame frequency may be lower than or equal to the first output frame frequency.
In example embodiments, the high frequency insertion pattern memory may store a plurality of high frequency insertion patterns that are different from each other, and the high frequency insertion pattern may be one of the plurality of high frequency insertion patterns. The high frequency insertion pattern memory may further store pattern select information indicating a selected one of the plurality of high frequency insertion patterns. After the low frequency driving time, the panel driver may drive the display panel based on the selected one of the plurality of high frequency insertion patterns.
In example embodiments, the high frequency insertion pattern memory may store a plurality of high frequency insertion patterns respectively corresponding to a plurality of gray ranges, the high frequency insertion pattern may be one of the plurality of high frequency insertion patterns, and the plurality of high frequency insertion patterns may be determined according to luminance decrease rates of the display panel corresponding to the plurality of gray ranges during the low frequency driving time.
In example embodiments, the panel driver may further include a representative gray level calculating unit configured to calculate the representative gray level of the input image data, a driving frequency changing unit configured to output output image data at the first output frame frequency when the input image data do not represent the still image, to output the output image data at the second output frame frequency for the low frequency driving time when the input image data represent the still image, and to output the output image data based on the high frequency insertion pattern selected according to the representative gray level among the plurality of high frequency insertion patterns stored in the high frequency insertion pattern memory after the low frequency driving time, and a data driver configured to provide data signals to the plurality of pixels based on the output image data.
As described above, an OLED display device according to example embodiments may determine whether input image data represent a still image. When the input image data represent the still image, the OLED display device may drive a display panel at an output frame frequency lower than an input frame frequency for a low frequency driving time, and may drive the display panel at a frequency higher than the output frame frequency for a high frequency insertion time after the low frequency driving time. Accordingly, a threshold voltage shift of a plurality of driving transistors which occurs during the low frequency driving time may be compensated during the high frequency insertion time, thereby reducing or preventing luminance deterioration and a flicker. Further, the high frequency insertion time may be determined based on at least one of a panel characteristic of the display panel and a representative gray level of the input image data, and thus high frequency insertion suitable for each display panel may be performed.
Further, an OLED display device according to other example embodiments may determine whether input image data represent a still image. When the input image data represent the still image, the OLED display device may drive a display panel at an output frame frequency lower than an input frame frequency for a low frequency driving time, and may drive the display panel based on a high frequency insertion pattern that is determined according to a panel characteristic of the display panel after the low frequency driving time. Accordingly, the luminance deterioration and the flicker caused by the low frequency driving may be reduced or prevented, and the high frequency insertion suitable for each display panel may be performed.
Illustrative, non-limiting example embodiments will be more clearly understood from the following detailed description in conjunction with the accompanying drawings.
Hereinafter, embodiments of the present inventive concept will be explained in detail with reference to the accompanying drawings.
Referring to
The display panel 110 may include a plurality of data lines, a plurality of scan lines, and the plurality of pixels PX coupled to the plurality of data lines and the plurality of scan lines. In some example embodiments, each pixel PX may include at least one capacitor, at least two transistors and an organic light emitting diode (OLED), and the display panel 110 may be an OLED display panel. In some example embodiments, each pixel PX may be a hybrid oxide polycrystalline (HOP) pixel suitable for low frequency driving for reducing power consumption. For example, in the HOP pixel, at least one first transistor may be a low-temperature polycrystalline silicon (LTPS) P-type Metal Oxide Semiconductor (PMOS) transistor, and at least one second transistor may be an oxide N-type Metal Oxide Semiconductor (NMOS) transistor.
In some example embodiments, as illustrated in
In some example embodiments, at least one of the driving transistor T1, the switching transistor T2, the compensating transistor T3, the first initializing transistor T4, the first emission controlling transistor T5, the second emission controlling transistor T6 and the second initializing transistor T7 may be implemented with a PMOS transistor, and at least one of the driving transistor T1, the switching transistor T2, the compensating transistor T3, the first initializing transistor T4, the first emission controlling transistor T5, the second emission controlling transistor T6 and the second initializing transistor T7 may be implemented with an NMOS transistor. For example, as illustrated in
In other example embodiments, as illustrated in
In some example embodiments, at least one of the driving transistor TDR, the first switching transistor TSW1, the second switching transistor TSW2 and the emission controlling transistor TEM may be implemented with a PMOS transistor, and at least one of the driving transistor TDR, the first switching transistor TSW1, the second switching transistor TSW2 and the emission controlling transistor TEM may be implemented with an NMOS transistor. For example, as illustrated in
Although
Referring back to
Still referring to
The controller (e.g., a timing controller; TCON) 140 may receive input image data IDAT and a control signal CTRL from an external host processor (e.g., an application processor (AP), a graphic processing unit (GPU) or a graphic card)). In some example embodiments, the input image data IDAT may be an RGB image data including red image data, green image data and blue image data. Further, in some example embodiments, the control signal CTRL may include, but not be limited to, a vertical synchronization signal, a horizontal synchronization signal, an input data enable signal, a master clock signal, etc. The controller 140 may generate the output image data ODAT, the data control signal DCTRL, and the scan control signal SCTRL based on the input image data IDAT and the control signal CTRL. The controller 140 may control an operation of the data driver 120 by providing the output image data ODAT and the data control signal DCTRL to the data driver 120, and may control an operation of the scan driver 130 by providing the scan control signal SCTRL to the scan driver 130.
The controller 140 may receive the input image data IDAT at the input frame frequency IFF from the host processor, and may determine whether the input image data IDAT represent a still image. In some example embodiments, the input frame frequency IFF may be a constant or fixed frequency. For example, the input frame frequency IFF may be, but not be limited to, about 60 Hz, about 120 Hz, or the like. In a case where the input image data IDAT do not represent the still image, or in a case where the input image data IDAT represent the moving image, the controller 140 may control the data driver 120 and the scan driver 130 to drive the display panel 110 at the first output frame frequency OFF1 substantially the same as the input frame frequency IFF. In a case where the input image data IDAT represent the still image, the controller 140 may control the data driver 120 and the scan driver 130 to drive the display panel 110 at the second output frame frequency OFF2 lower than the input frame frequency IFF for the low frequency driving time. After the low frequency driving time, the controller 140 may control the data driver 120 and the scan driver 130 to drive the display panel 110 at the third output frame frequency OFF3 higher than the second output frame frequency OFF2 and lower than or equal to the input frame frequency IFF for the high frequency insertion time. In some example embodiments, the high frequency insertion time may be determined based on at least one of a panel characteristic of the display panel 110 and a representative gray level of the input image data IDAT. After the high frequency insertion time, the controller 140 may control the data driver 120 and the scan driver 130 to drive the display panel 110 again at the second output frame frequency OFF2. To perform these operations, the controller 140 may include a still image detector 150 and a driving frequency changer 160.
The still image detector 150 may determine whether the input image data IDAT represent the still image. For example, the still image detector 150 may compare the input image data IDAT in a previous frame and the input image data IDAT in a current frame, may determine that the input image data IDAT do not represent the still image when the input image data IDAT in the current frame are different from the input image data IDAT in the previous frame, and may determine that the input image data IDAT represent the still image when the input image data IDAT in the current frame are substantially the same as the input image data IDAT in the previous frame. In some example embodiments, to compare the input image data IDAT in the previous frame and the input image data IDAT in the current frame, the still image detector 150 may calculate a representative value (e.g., an average value, a checksum, etc.) of the input image data IDAT in the previous frame and a representative value of and the input image data IDAT in the current frame, and may compare the representative values.
The driving frequency changer 160 may selectively output the input image data IDAT as the output image data ODAT according to whether the input image data IDAT represent the still image. In a case where the input image data IDAT do not represent the still image, the driving frequency changer 160 may output all the input image data IDAT as the output image data ODAT. For example, as illustrated in
In a case where the input image data IDAT represent the still image, the driving frequency changer 160 may output, among the input image data IDAT of a plurality of frames, the input image data IDAT of a first portion of the plurality of frames as the output image data ODAT for the low frequency driving time LFDT. For example, as illustrated in
After the low frequency driving time LFDT, the driving frequency changer 160 may output, among the input image data IDAT of the plurality of frames, the input image data IDAT of a second portion greater than the first portion of the plurality of frames or the input image data IDAT of all of the plurality of frames as the output image data ODAT for the high frequency insertion time HFIT. According to example embodiments, the low frequency driving time LFDT may be determined according to the panel characteristic of the display panel 110, or may be settable. For example, as illustrated in
After the high frequency insertion time HFIT, the driving frequency changer 160 may output the output image data ODAT again at the second output frame frequency OFF2, and the data driver 120 may drive the display panel 110 again at the second output frame frequency OFF2 based on the output image data ODAT. In some example embodiments, if the low frequency driving at the second output frame frequency OFF2 is performed again for the low frequency driving time LFDT, the display panel 110 may be driven again at the third output frame frequency OFFS for the high frequency insertion time HFIT. That is, in some example embodiments, the high frequency insertion time HFIT may be periodically inserted while the still image represented by the input image data IDAT is not changed. For example, as illustrated in
In some example embodiments, a threshold voltage shift of a plurality of driving transistors included in the plurality of pixels PX which occurs during the low frequency driving time LFDT may be compensated during the high frequency insertion time HFIT. For example, during the low frequency driving time LFDT, an off-bias may be applied to the plurality of driving transistors, and thus threshold voltages of the plurality of driving transistors may be shifted, which results in a deterioration of luminance of the display panel 110. For example, as illustrated in
However, if the high frequency insertion time HFIT inserted during the low frequency driving is excessively long, the power consumption may not be reduced during the low frequency driving. Furthermore, if the high frequency insertion time HFIT is excessively short, the threshold voltage shift may not be sufficiently compensated, and the luminance deterioration and the flicker may not be reduced or prevented. Still furthermore, the threshold voltage shift and the luminance deterioration may occur at different levels with respect to different display panels 110. However, in the OLED display device 100 according to example embodiments, the high frequency insertion time HFIT may be determined based on at least one of the panel characteristic of the display panel 110 (e.g., the luminance decrease rate of the display panel 110 during the low frequency driving time LFDT) and the representative gray level of the input image data IDAT. Thus, the display panel 110 may be driven at the third output frame frequency OFF3 higher than the second output frame frequency OFF2 for the high frequency insertion time HFIT suitable for each display panel 110. That is, the high frequency insertion may be performed corresponding to each display panel 110. Accordingly, in the OLED display device 100 according to example embodiments, the reduction of the power consumption may be maximized by the low frequency driving, the threshold voltage shift may be sufficiently compensated, and the luminance deterioration and the flicker caused by the low frequency driving may be reduced or prevented.
Referring to
The high frequency insertion time storage 162a may store the high frequency insertion time that is determined according to a panel characteristic of the display panel 110. In some example embodiments, the high frequency insertion time stored in the high frequency insertion time storage 162a may be determined according to a luminance decrease rate of the display panel 110 as the panel characteristic of the display panel 110 during a low frequency driving time. For example, the high frequency insertion time may be determined to be relatively long with respect to the display panel 110 having a relatively high luminance decrease rate, and may be determined to be relatively short with respect to the display panel 110 having a relatively low luminance decrease rate.
The driving frequency changing unit 164a may output the output image data ODAT at the first output frame frequency OFF1 substantially the same as the input frame frequency IFF when the input image data IDAT do not represent the still image, and may output the output image data ODAT at the second output frame frequency OFF2 lower than the input frame frequency IFF for the low frequency driving time when the input image data represent the still image. Furthermore, after the low frequency driving time, the driving frequency changing unit 164a may output the output image data ODAT at the third output frame frequency OFF3 higher than the second output frame frequency OFF2 for the high frequency insertion time stored in the high frequency insertion time storage 162a.
Hereinafter, a method of operating the OLED display device 100 including the driving frequency changer 160a will be described below with reference to
Referring to
A panel driver 170 may receive the input image data IDAT at the input frame frequency IFF from a host processor (S220), and may determine whether the input image data IDAT represent the still image (S230). For example, a still image detector 150 included in the panel driver 170 may determine whether the input image data IDAT represent the still image by comparing the input image data IDAT in a previous frame and the input image data IDAT in a current frame.
When the input image data IDAT do not represent the still image (S230: NO), the panel driver 170 may drive the display panel 110 at the first output frame frequency OFF1 substantially the same as the input frame frequency IFF (S240). For example, the driving frequency changing unit 164a may output the output image data ODAT at the first output frame frequency OFF1 substantially the same as the input frame frequency IFF, and a data driver 120 may drive the display panel 110 at the first output frame frequency OFF1 based on the output image data ODAT.
When the input image data IDAT represent the still image (S230: YES), the panel driver 170 may drive the display panel 110 at the second output frame frequency OFF2 lower than the input frame frequency IFF for the low frequency driving time (S250), and may drive the display panel 110 at the third output frame frequency OFF3 higher than the second output frame frequency OFF2 and lower than or equal to the first output frame frequency OFF1 for the high frequency insertion time stored in the high frequency insertion time storage 162a after the low frequency driving time (S260). For example, during the low frequency driving time, the driving frequency changing unit 164a may output the output image data ODAT at the second output frame frequency OFF2, and the data driver 120 may drive the display panel 110 at the second output frame frequency OFF2 based on the output image data ODAT. Furthermore, during the high frequency insertion time after the low frequency driving time, the driving frequency changing unit 164a may output the output image data ODAT at the third output frame frequency OFF3, and the data driver 120 may drive the display panel 110 at the third output frame frequency OFF3 based on the output image data ODAT. In some example embodiments, driving the display panel 110 at the second output frame frequency OFF2 for the low frequency driving time and driving the display panel 110 at the third output frame frequency OFF3 for the high frequency insertion time may be repeated until the still image represented by the input image data IDAT are changed (S270).
As described above, in the method of operating the OLED display device 100 according to example embodiments, the high frequency insertion time may be determined according to the panel characteristic of the display panel 110, or according to the luminance decrease rate of the display panel 110 during the low frequency driving time LFDT. Accordingly, power consumption may be reduced by low frequency driving, a threshold voltage shift may be sufficiently compensated, and luminance deterioration and a flicker caused by the low frequency driving may be reduced or prevented.
Referring to
The representative gray level calculating unit 163b may calculate the representative gray level of input image data IDAT. In some example embodiments, the representative gray level calculating unit 163b may calculate, as the representative gray level of the input image data IDAT, an average value of gray levels of (a plurality of pixel data included in) the input image data IDAT, a maximum value of the gray levels of the input image data IDAT, a minimum value of the gray levels of the input image data IDAT, or a value extracted from the gray levels of the input image data IDAT.
The driving frequency changing unit 164b may output the output image data ODAT at the first output frame frequency OFF1 substantially the same as the input frame frequency IFF when the input image data IDAT do not represent the still image, and may output the output image data ODAT at the second output frame frequency OFF2 lower than the input frame frequency IFF for the low frequency driving time when the input image data represent the still image. Furthermore, after the low frequency driving time, the driving frequency changing unit 164a may output the output image data ODAT at the third output frame frequency OFF3 higher than the second output frame frequency OFF2 for the high frequency insertion time corresponding to the representative gray level calculated by the representative gray level calculating unit 163b. In some example embodiments, the driving frequency changing unit 164b may determine the high frequency insertion time as a first time when the representative gray level is within a high gray range (e.g., from a 100-gray level to a 255-gray level), may determine the high frequency insertion time as a second time shorter than the first time when the representative gray level is within a middle gray range (e.g., from a 30-gray level to a 99-gray level), and may determine the high frequency insertion time as a third time longer than the first time when the representative gray level is within a low gray range (e.g., from a 0-gray level to a 29-gray level). For example, a luminance decrease rate of a display panel 110 during the low frequency driving time in a case where the display panel 110 displays a high gray image may be greater than a luminance decrease rate of the display panel 110 during the low frequency driving time in a case where the display panel 110 displays a middle gray image, and thus the high frequency insertion time when the representative gray level is within the high gray range may be longer than the high frequency insertion time when the representative gray level is within the middle gray range. Still furthermore, a flicker may be prone to be perceived by a user when the display panel 110 displays a low gray image, and thus the high frequency insertion time when the representative gray level is within the low gray range may be relatively long.
Hereinafter, a method of operating the OLED display device 100 including the driving frequency changer 160b will be described below with reference to
Referring to
When the input image data IDAT do not represent the still image (S330: NO), the panel driver 170 may drive the display panel 110 at the first output frame frequency OFF1 substantially the same as the input frame frequency IFF (S340).
When the input image data IDAT represent the still image (S330: YES), the panel driver 170 may calculate the representative gray level of input image data IDAT (S350). For example, the representative gray level calculating unit 163b included in the panel driver 170 may calculate, as the representative gray level of the input image data IDAT, the average value, the maximum value, the minimum value or any value extracted from the gray levels of the input image data IDAT.
The panel driver 170 may drive the display panel 110 at the second output frame frequency OFF2 lower than the input frame frequency IFF for the low frequency driving time (S360), and may drive the display panel 110 at the third output frame frequency OFF3 higher than the second output frame frequency OFF2 and lower than or equal to the first output frame frequency OFF1 for the high frequency insertion time corresponding to the representative gray level calculated by the representative gray level calculating unit 163b after the low frequency driving time (S370). In some example embodiments, the driving frequency changing unit 164b included in the display panel 110 may determine the high frequency insertion time according to whether the representative gray level is within the high gray range, the middle gray range or the low gray range. For example, as illustrated in
As described above, in the method of operating the OLED display device 100 according to example embodiments, the high frequency insertion time may be determined according to the representative gray level of the input image data IDAT. Accordingly, power consumption may be reduced by low frequency driving, a threshold voltage shift may be sufficiently compensated, and the luminance deterioration and the flicker caused by the low frequency driving may be reduced or prevented.
Referring to
The plurality of high frequency insertion times corresponding to the plurality of gray ranges stored in the high frequency insertion time storage 162c may be determined according to luminance decrease rates of a display panel 110 corresponding to the plurality of gray ranges during a low frequency driving time. For example, the high frequency insertion time storage 162c may store a first high frequency insertion time corresponding to a high gray range, a second high frequency insertion time corresponding to a middle gray range, and a third high frequency insertion time corresponding to a low gray range. Furthermore, for example, the first high frequency insertion time may be determined the luminance decrease rate of the display panel 110 during the low frequency driving time when a high gray image is displayed, the second high frequency insertion time may be determined the luminance decrease rate of the display panel 110 during the low frequency driving time when a middle gray image is displayed, and the third high frequency insertion time may be determined the luminance decrease rate of the display panel 110 during the low frequency driving time when a low gray image is displayed.
The representative gray level calculating unit 163c may calculate the representative gray level of the input image data IDAT. According to example embodiments, the representative gray level calculating unit 163c may calculate, as the representative gray level of the input image data IDAT, an average value, a maximum value, a minimum value or any value extracted from gray levels of the input image data IDAT.
The driving frequency changing unit 164c may output the output image data ODAT at the first output frame frequency OFF1 substantially the same as the input frame frequency IFF when the input image data IDAT do not represent the still image, and may output the output image data ODAT at the second output frame frequency OFF2 lower than the input frame frequency IFF for the low frequency driving time when the input image data represent the still image. Furthermore, after the low frequency driving time, the driving frequency changing unit 164c may output the output image data ODAT at the third output frame frequency OFF3 higher than the second output frame frequency OFF2 for a high frequency insertion time selected according to the representative gray level among the plurality of high frequency insertion times stored in the high frequency insertion time storage 162c. For example, the driving frequency changing unit 164c may output the output image data ODAT at the third output frame frequency OFF3 for the first high frequency insertion time when the representative gray level is within the high gray range, may output the output image data ODAT at the third output frame frequency OFF3 for the second high frequency insertion time when the representative gray level is within the middle gray range, and may output the output image data ODAT at the third output frame frequency OFF3 for the third high frequency insertion time when the representative gray level is within the low gray range. The data driver 120 may drive the display panel 110 at the first output frame frequency OFF1, the second output frame frequency OFF2 or the third output frame frequency OFF3 based on the output image data ODAT.
As described above, in the method of operating the OLED display device 100 according to example embodiments, the plurality of high frequency insertion times may be determined according to the panel characteristics of the display panel 110 corresponding to the plurality of gray ranges, and one of the plurality of high frequency insertion times may be selected according to the representative gray level of the input image data IDAT. Accordingly, power consumption may be reduced by low frequency driving, a threshold voltage shift may be sufficiently compensated, and luminance deterioration and a flicker caused by the low frequency driving may be reduced or prevented.
Referring to
The high frequency insertion pattern memory 480 may store a high frequency insertion pattern that is determined according to a panel characteristic of the display panel 110. For example, the high frequency insertion pattern may be determined according to a luminance decrease rate of the display panel 110 when low frequency driving is performed. In some example embodiments, the high frequency insertion pattern may represent one or more frequencies higher than a frequency of the low frequency driving, and the respective numbers of frames for the one or more frequencies. In other example embodiments, the high frequency insertion pattern memory 480 may store a plurality of high frequency insertion patterns that are different from each other, and store pattern select information indicating a selected one of the plurality of high frequency insertion patterns.
The still image detector 450 may receive input image data IDAT at an input frame frequency IFF, and may determine whether the input image data IDAT represent a still image.
When the input image data IDAT do not represent the still image, the driving frequency changer 460 may output output image data ODAT at a first output frame frequency OFF1 substantially the same as the input frame frequency IFF, and the data driver 120 may drive the display panel 110 at the first output frame frequency OFF1 based on the output image data ODAT.
When the input image data IDAT represent the still image, the driving frequency changer 460 may output the output image data ODAT at a second output frame frequency OFF2 lower than the input frame frequency IFF for a low frequency driving time, and the data driver 120 may drive the display panel 110 at the second output frame frequency OFF2 based on the output image data ODAT. After the low frequency driving time, the driving frequency changer 460 may output the output image data ODAT based on the high frequency insertion pattern stored in the high frequency insertion pattern memory 480, and the data driver 120 may drive the display panel 110 corresponding to the high frequency insertion pattern based on the output image data ODAT. For example, the high frequency insertion pattern may represent at least one third output frame frequency OFF3 higher than the second output frame frequency OFF2 and lower than or equal to the first output frame frequency OFF1, and the number of frames for the third output frame frequency OFF3, and, after the low frequency driving time, the panel driver 470 may drive the display panel 110 at the third output frame frequency OFF3 represented by the high frequency insertion pattern for a time corresponding to the number of frames based on the high frequency insertion pattern. In some example embodiments, a threshold voltage shift of a plurality of driving transistors included in the plurality of pixels PX which occurs during the low frequency driving time may be compensated while the display panel 110 is driven at the third output frame frequency OFF3 higher than the second output frame frequency OFF2 based on the high frequency insertion pattern.
As described above, in the OLED display device 400 according to example embodiments, in a case where the input image data IDAT represent the still image, the display panel 110 may be driven at the second output frame frequency OFF2 lower than the input frame frequency IFF for the low frequency driving time, and, after the low frequency driving time, the display panel 110 may be driven based on the high frequency insertion pattern determined according to the panel characteristic of the display panel 110. Accordingly, luminance deterioration and a flicker caused by low frequency driving may be reduced or prevented, and the high frequency insertion suitable for each display panel 110 may be performed.
Referring to
A panel driver 470 may receive input image data IDAT at an input frame frequency IFF from a host processor (S520), and may determine whether the input image data IDAT represent a still image (S530).
When the input image data IDAT do not represent the still image (S530: NO), the panel driver 470 may drive the display panel 110 at a first output frame frequency OFF1 substantially the same as the input frame frequency IFF (S540).
When the input image data IDAT represent the still image (S530: YES), the panel driver 470 may drive the display panel 110 at a second output frame frequency OFF2 lower than the input frame frequency IFF for a low frequency driving time (S550), and may drive the display panel 110 based on the high frequency insertion pattern stored in the high frequency insertion pattern memory 480 after the low frequency driving time (S560).
For example, in a case where the high frequency insertion pattern illustrated in
In another example, as illustrated in
Referring to
A panel driver 470 may receive input image data IDAT at an input frame frequency IFF from a host processor (S620), and may determine whether the input image data IDAT represent a still image (S630).
When the input image data IDAT do not represent the still image (S630: NO), the panel driver 470 may drive the display panel 110 at a first output frame frequency OFF1 substantially the same as the input frame frequency IFF (S640).
When the input image data IDAT represent the still image (S630: YES), the panel driver 470 may calculate a representative gray level of the input image data IDAT (S650). For example, a representative gray level calculating unit included in the panel driver 470 may calculate, as the representative gray level of the input image data IDAT, an average value, a maximum value, a minimum value or any value extracted from gray levels of the input image data IDAT.
The panel driver 470 may drive the display panel 110 at a second output frame frequency OFF2 lower than the input frame frequency IFF for a low frequency driving time (S660), and may drive the display panel 110 based on a high frequency insertion pattern selected according to the representative gray level among the plurality of high frequency insertion patterns stored in the high frequency insertion pattern memory 480 after the low frequency driving time (S670). For example, in a case where the high frequency insertion pattern memory 480 stores the first through third high frequency insertion patterns as illustrated in
Referring to
The processor 1110 may perform various computing functions or tasks. The processor 1110 may be an application processor (AP), a micro processor, a central processing unit (CPU), etc. The processor 1110 may be coupled to other components via an address bus, a control bus, a data bus, etc. Furthermore, in some example embodiments, the processor 1110 may be further coupled to an extended bus such as a peripheral component interconnection (PCI) bus.
The memory device 1120 may store data for operations of the electronic device 1100. For example, the memory device 1120 may include at least one non-volatile memory device such as an erasable programmable read-only memory (EPROM) device, an electrically erasable programmable read-only memory (EEPROM) device, a flash memory device, a phase change random access memory (PRAM) device, a resistance random access memory (RRAM) device, a nano floating gate memory (NFGM) device, a polymer random access memory (PoRAM) device, a magnetic random access memory (MRAM) device, a ferroelectric random access memory (FRAM) device, etc, and/or at least one volatile memory device such as a dynamic random access memory (DRAM) device, a static random access memory (SRAM) device, a mobile dynamic random access memory (mobile DRAM) device, etc.
The storage device 1130 may be a solid state drive (SSD) device, a hard disk drive (HDD) device, a CD-ROM device, etc. The I/O device 1140 may be an input device such as a keyboard, a keypad, a mouse, a touch screen, etc, and an output device such as a printer, a speaker, etc. The power supply 1150 may supply power for operations of the electronic device 1100. The OLED display device 1160 may be coupled to other components through the buses or other communication links.
The OLED display device 1160 may determine whether input image data represent a still image. When the input image data represent the still image, the OLED display device 1160 may drive a display panel at an output frame frequency lower than an input frame frequency for a low frequency driving time, and may drive the display panel at a frequency higher than the output frame frequency for a high frequency insertion time after the low frequency driving time. Accordingly, a threshold voltage shift of a plurality of driving transistors which occurs during the low frequency driving time may be compensated during the high frequency insertion time, thereby reducing or preventing luminance deterioration and a flicker. Furthermore, the high frequency insertion time may be determined based on at least one of a panel characteristic of the display panel and a representative gray level of the input image data, and thus high frequency insertion suitable for each display panel may be performed.
The present disclosure may be applied to any OLED display device 1160, and any electronic device 1100 including the OLED display device 1160. For example, the inventive concepts may be applied to a mobile phone, a smart phone, a wearable electronic device, a tablet computer, a television (TV), a digital TV, a 3D TV, a personal computer (PC), a home appliance, a laptop computer, a personal digital assistant (PDA), a portable multimedia player (PMP), a digital camera, a music player, a portable game console, a navigation device, etc.
The foregoing is illustrative of example embodiments and is not to be construed as limiting thereof. Although a few example embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the novel teachings and advantages of the present disclosure. Accordingly, all such modifications are intended to be included within the scope of the present disclosure as defined in the claims. Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and is not to be construed as limited to the specific example embodiments disclosed, and that modifications to the disclosed example embodiments, as well as other example embodiments, are intended to be included within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2019-0093149 | Jul 2019 | KR | national |
This application is a continuation application of U.S. patent application Ser. No. 16/923,008 filed on Jul. 7, 2020, which claims priority under 35 USC § 119 to Korean Patent Application No. 10-2019-0093149, filed on Jul. 31, 2019 in the Korean Intellectual Property Office (KIPO), the disclosures of which are incorporated herein in their entirety by reference.
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| 20090122087 | Maruyama | May 2009 | A1 |
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| Number | Date | Country |
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| Number | Date | Country | |
|---|---|---|---|
| 20210193054 A1 | Jun 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16923008 | Jul 2020 | US |
| Child | 17190962 | US |
