Display device comparing image data between adjacent frames and determining first and second areas to drive first and second areas at different refresh rates and driving method thereof

A display device includes: a pixel unit including a plurality of pixels connected to a plurality of scan lines and a plurality of data lines; a multi-frequency driver configured to compare image data between adjacent frames to determine a first area of the pixel unit driven at a first refresh rate and a second area of the pixel unit driven at a second refresh rate lower than the first refresh rate; a scan driver configured to sequentially supply scan signals to the scan lines in a first direction, to supply first scan signals of the scan signals to the first area at the first refresh rate, and to supply second scan signals of the scan signals to the second area at the second refresh rate; and a data driver configured to supply a data signal corresponding to the image data to the data lines.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0091913 filed in the Korean Intellectual Property Office on Jul. 29, 2019, the entire contents of which are incorporated herein by reference.

BACKGROUND

Aspects of some example embodiments of the present invention relate to an electronic device, and for example, a display device included in the electronic device and a driving method thereof.

2. Description of the Related Art

A display device includes a display panel (or pixel unit) and a driver. The display panel generally includes scan lines, data lines, and pixels. The driver generally includes a scan driver for providing scan signals to scan lines and a data driver for providing data signals to data lines. Each pixel emits light with luminance corresponding to the data signal provided through the corresponding data line in response to the scan signal provided through the corresponding scan line.

The display device may display an image at a low frequency to reduce power consumption. For example, when the display device displays static images or ambient images (e.g., in the case of an always on display, an ambient display, etc.), it may display the images at a lower refresh rate than a refresh rate for displaying other categories of images (i.e., video, user's use image). Alternatively, only a portion of the display panel may be driven to reduce power consumption.

SUMMARY

Aspects of some example embodiments of the present invention include a display device that compares image data to determine a boundary between a first area and a second area of a pixel unit, and drives the second area at a lower frequency (e.g., refresh rate) than the first area.

Aspects of some example embodiments of the present invention include a driving method for the display device.

However, the characteristics of the present invention are not limited to the characteristics described above, but may be variously extended or modified without departing from the idea and scope of embodiments according to the present invention.

A display device according to some example embodiments of the present invention includes a pixel unit including a plurality of pixels connected to a plurality of scan lines and a plurality of data lines; a multi-frequency driver comparing image data between adjacent frames to determine a first area of the pixel unit driven at a first refresh rate and a second area of the pixel unit driven at a second refresh rate lower than the first refresh rate; a scan driver for sequentially supplying a scan signal to the scan lines in a first direction, supplying the scan signal to the first area at the first refresh rate, and supplying the scan signal to the second area at the second refresh rate; and a data driver for supplying a data signal corresponding to the image data to the data lines.

According to some example embodiments, the multi-frequency driver may determine a boundary pixel row, which is a top pixel row of the second area, based on results of comparing the image data during a plurality of frames.

According to some example embodiments, the scan driver may supply the scan signal from the boundary pixel row to a last pixel row at the second refresh rate.

According to some example embodiments, when a video is displayed on a portion of the pixel unit, the multi-frequency driver may gradually increase a size of an area driven at the second refresh rate in a second direction opposite to the first direction during a search period for determining the boundary pixel row.

According to some example embodiments, the scan driver may gradually increase a number of the scan lines driven at the second refresh rate during the search period in response to a command of the multi-frequency driver.

According to some example embodiments, the multi-frequency driver may include an image analyzer that compares image data of a previous frame of an image block included in the pixel unit with image data of a current frame of the image block included in the pixel unit to determine whether the image block is a static image; a block controller that determines a size, a number and a position of the image block in which it is to be determined whether the image block is a static image; and a frequency controller that applies the second refresh rate to the image block determined as the static image.

According to some example embodiments, when a first image block is determined to the static image, the image analyzer may determine whether the first image block and a second image block adjacent to the first image block is a static image.

According to some example embodiments, the frequency controller may extend a portion of the pixel unit to which the second refresh rate is applied in the second direction opposite to the first direction, in response to a number of image blocks determined as the static image.

According to some example embodiments, when the image block is not determined to the static image, the block controller may reduce a size of the image block by changing a position of the top pixel row of the image block with respect to the first direction.

According to some example embodiments, when the image block is not determined to the static image, the image analyzer may determine whether the reduced image block is the static image.

According to some example embodiments, when a size of the image block is reduced to less than or equal to a predetermined number of pixel rows, the block controller may determine one of pixel rows included in the reduced image block as a boundary pixel row which is a top pixel row of the second area, and may determine the second area including the boundary pixel row.

According to some example embodiments, when image data of the second area is changed, the frequency controller may output an initialization signal to initialize the second area and the boundary pixel row.

According to some example embodiments, the scan driver may supply the scan signal to the scan lines at the first refresh rate in response to the initialization signal.

According to some example embodiments, the image analyzer may determine the static image based on a difference between a checksum of the image data of the previous frame of the image block and a checksum of the image data of the current frame of the image block.

According to some example embodiments, the first area may include a video, and an image displayed in the second area may be a static image.

According to some example embodiments, the display device may further include a timing controller supplying first image data corresponding to the first area to the data driver at the first refresh rate, and supplying second image data corresponding to the second area to the data driver at the second refresh rate; and a processor changing some of the second image data to supply the multi-frequency driver when an image change event of the second area occurs.

According to some example embodiments, the data driver may supply the data signal corresponding to the first area to the pixel unit at the first refresh rate, and may supply the data signal corresponding to the second area to the pixel unit at the second refresh rate.

A driving method of a display device according to some example embodiments of the present invention includes comparing image data of a previous image frame of a first image block with image data of a current image frame of the first image block to determine whether the first image block is a static image; driving the first image block at a first refresh rate, and reducing a size of the first image block in a first direction when the first image block is not a static image; determining one of pixel rows included in the reduced first image block as a boundary pixel row between a static image area and a video area, and determining the static image area including the boundary pixel row; and driving the first image block at a second refresh rate lower than the first refresh rate when the first image block is a static image.

According to some example embodiments, the determining the static image area may further include driving the static image area at the second refresh rate and driving the video area at the first refresh rate. The static image area may include an area from the boundary pixel row to a last pixel row.

According to some example embodiments, a size of an area driven at the second refresh rate may gradually increase during a search period for determining the boundary pixel row.

A display device and a driving method thereof according to some example embodiments of the present invention may compare image data in real time without a frame memory and the like, and may detect an optimal (or desired) boundary pixel row between a first area and a second area while gradually increasing an area to which a second refresh rate is applied for a short time. Thus, power consumption for driving at a multiple frequency (or multiple refresh rate) may be minimized or reduced without increasing a cost for detecting the boundary pixel row detection.

However, the characteristics of example embodiments according to the present invention are not limited to the characteristics described above, but may be variously extended in a range that does not depart from the idea and scope of the present invention.

DETAILED DESCRIPTION

Hereinafter, with reference to accompanying drawings, aspects of some example embodiments of the present invention will be described in more detail. The same reference numerals are used for the same constituent elements on the drawing and duplicate descriptions for the same constituent elements are omitted.

FIG.1is a block diagram showing a display device according to some example embodiments of the present invention.

Referring toFIG.1, a display device1000may include a pixel unit100, a multi-frequency driver200, a timing controller300, a scan driver400, an emission driver500, and a data driver600. According to some example embodiments, the display device1000may further include a processor10.

The display device1000may display an image by a command and data supplied from the processor10. The processor10may be implemented as an application processor, a graphics processor, and the like.

Meanwhile, the display device1000may be implemented as an organic light emitting diode display, a liquid crystal display, and the like. However, this is merely an example, and a configuration of the display device1000is not limited thereto. For example, the display device1000may include any suitable display device

The pixel unit100may include a plurality of scan lines SL1to SLn, a plurality of emission control lines EL1to ELn, and a plurality of data lines DL1to DLm, and may include a plurality of pixels PX connected to the scan lines SL1to SLn, the emission control lines EL1to ELn, and the data lines DL1to DLm (here m and n are integer greater than 1). Each of the pixels PX may include a driving transistor and a plurality of switching transistors.

The pixel unit100displays an image by using an emission of the pixels PX. For displaying a video, a relatively high driving frequency (or refresh rate) is required to represent smoother and continuous movement. The refresh rate may be referred to as a screen refresh rate, and represent a frequency at which a display screen is played for one second. That is, the refresh rate is a driving frequency of a signal output of the data driver600and/or the scan driver400. For example, the refresh rate for driving the video may be a frequency of about 60 Hz or more (e.g., 120 Hz).

A high refresh rate may not be desired or necessary for displaying the static image. Therefore, the related art systems may display an image by setting the refresh rate of the entire pixel unit100to a low frequency of 40 Hz or less in order to reduce the power consumption for displaying the static image.

Meanwhile, the pixel unit100may display a screen in which the static image and the video are mixed. Related-art frequency control systems may change the refresh rate for the entire screen depending on an image mode (or power mode). Therefore, the refresh rate may be separated according to the area of the pixel unit100in an operating condition for driving the pixel unit100. The refresh rate may be divided with respect to pixel rows (e.g., set or predetermined pixel rows). For example, an upper area of the pixel row selected by a low frequency driving signal LFD may be driven at a first frame rate, and a lower area of the selected pixel row may be driven at a second frame rate.

The display device1000according to some example embodiments of the present invention may apply different refresh rates to a portion corresponding to the static image and a portion where the video is displayed when displays a screen in which the static image and the video are mixed. Therefore, high quality videos can be implemented and power consumption can be reduced concurrently (e.g., simultaneously).

The multi-frequency driver200may determine (e.g., automatically determine) a first area including the video and a second area in which the static image is displayed, and may control the display device1000to apply different refresh rates to the first area and the second area. The multi-frequency driver200may compare image data IDATA between adjacent frames to determine the first area and the second area. The image data IDATA may be provided from the processor10.

In addition, the multi-frequency driver200may provide a command (e.g., low frequency driving signal LFD) for driving the first area at the first refresh rate and the second area at the second refresh rate to the timing controller300

The low frequency driving signal LFD may include information indicating the first pixel row to which the second refresh rate is applied among the pixel rows included in the pixel unit100.

According to some example embodiments, the multi-frequency driver200may determine a boundary pixel row which is a top pixel row of the second area based on a result of comparing image data IDATA during a plurality of frames. For example, the multi-frequency driver200may gradually increase a size of an area driven at the second refresh rate during a search period for determining the boundary pixel row. Accordingly, the pixel row indicated by the low frequency driving signal LFD during the search period may vary.

The multi-frequency driver200can perform frequency division driving at an optimal or desired ratio for the pixel unit100by precisely detecting the first area to which the first refresh rate is applied and the second area to which the second refresh rate is applied.

The timing controller300may generate a first control signal SCS, a second control signal ECS, and a third control signal DCS in response to synchronization signals supplied from the processor10or the like. The first control signal SCS may be supplied to the scan driver400, the second control signal ECS may be supplied to the emission driver500, and the third control signal DCS may be supplied to the data driver600.

In addition, the timing controller300may rearrange image data IDATA supplied from an external component (e.g., the processor10) and may supply the rearranged image data IDATA to the data driver600. According to some example embodiments, the timing controller300may divide the image data IDATA into first area data DATA1corresponding to the first area of the pixel unit100and second area data DATA2corresponding to the second area of the pixel unit100, and may supply the first area data DATA1and the second area data DATA2to the data driver600at different frequencies. For example, the timing controller300may supply the first area data DATA1to the data driver600at a frequency corresponding to the first refresh rate, and may supply the second area data DATA2to the data driver600at a frequency corresponding to the second refresh rate. Accordingly, a power consumption of the display device1000may be improved.

The first control signal SCS may include a scan start pulse and clock signals. The scan start pulse may control a first timing of the scan signal. The clock signals may be used to shift the scan start pulse.

The second control signal ECS may include an emission control start pulse and clock signals. The emission control start pulse may control a first timing of the emission control signal. The clock signals may be used to shift the emission control start pulse.

The third control signal DCS may include a source start pulse and clock signals. The source start pulse controls a sampling starting time point of data. The clock signals are used to control a sampling operation.

According to some example embodiments, the timing controller300may supply a masking signal MS to the scan driver400for a multi-frequency driving. The masking signal MS may be generated in response to the low frequency driving signal LFD. For example, the masking signal MS is a signal for controlling a scan line of a pixel row (e.g., a first pixel row of an area to which the second refresh rate is applied) indicated by the low frequency driving signal LFD. For example, the masking signal MS may be supplied to the scan driver400at the second refresh rate. Accordingly, the scan driver400may output a scan signal at a second refresh rate from a scan line of the pixel row indicated by the masking signal MS to the last scan line.

The scan driver400may receive the first control signal SCS and the masking signal MS from the timing controller300, and may supply the scan signal to the scan lines SL1to SLn based on the first control signal SCS and the masking signal MS. For example, the scan driver400may sequentially supply the scan signal to the scan lines SL1to SLn. When the scan signal is supplied sequentially, the pixels PX may be selected in unit of horizontal line (or in unit of pixel row).

According to some example embodiments, the scan driver400may supply the scan signal to the first area at a frequency of the first refresh rate, and may supply the scan signal to the second area at a frequency of the second refresh rate in response to the masking signal MS. For example, the scan driver400may supply the scan signal from the boundary pixel row to the last pixel row at the second refresh rate.

According to some example embodiments, during the search period for determining the boundary pixel row, the scan driver400may gradually increase the number of the scan lines driven at the second refresh rate in response to the low frequency driving signal LFD.

The scan signal may be set to a gate-on voltage (e.g., low voltage). A transistor included in the pixel PX and receiving the scan signal may be set to a turn-on state when the scan signal is supplied.

The emission driver500may receive a second control signal ECS from the timing controller300, and may supply the scan signal to the emission control lines EL1to ELn based on the second control signal ECS. For example, the emission driver500may sequentially supply the emission control signals through the emission control lines EL1to ELn.

The emission control signal may be set to a gate-on voltage (e.g., low voltage). A transistor included in the pixel PX and receiving the emission control signal may be turned on when the emission control signal is supplied, and may be turned off in other cases.

The emission control signal is used to control a light emitting time of the pixels PX. For this purpose, the emission control signal may be set to have a width greater than the scan signal.

According to some example embodiments, the emission driver500may supply the emission control signal to the first area at the first refresh rate, and may supply the emission control signal to the second area at the second refresh rate. However, this is an example, and the emission driver500may supply the emission control signal to the entire pixel unit100at the same frequency.

The scan driver400and the emission driver500may be mounted on a substrate through a thin film process, respectively. In addition, the scan driver400may be located at both sides with the pixel unit100interposed therebetween. The emission driver500may also be located on both sides with the pixel unit100interposed therebetween.

In addition, the scan driver400and the emission driver500are shown to provide the scan signal and the emission control signal, respectively inFIG.1, but embodiments according to the present invention are not limited thereto. For example, the scan signal and the emission control signal may be supplied by one driver.

The data driver600may receive the third control signal DCS and the image data signal (e.g., first area data DATA1and second area data DATA2) from the timing controller300. The data driver600may supply the data signal to the data lines DL1to DLm in response to the third control signal DCS. The data signal supplied to the data lines DL1to DLm may be supplied to the pixels PX selected by the scan signal. For example, the data driver600may supply the data signal to the data lines DL1to DLm to be synchronized with the scan signal.

According to some example embodiments, the data driver600may supply the data signal to the first area at a frequency of the first refresh rate, and may supply the data signal to the second area at a frequency of the second refresh rate. Accordingly, a power consumption of the display device1000may be improved.

Meanwhile, the multi-frequency driver200, the timing controller300, and the data driver600are shown as separate configurations or components inFIG.1, but embodiments according to the present invention are not limited thereto. For example, at least two of the multi-frequency driver200, the timing controller300, and/or the data driver600may be included in one driving chip TED or an integrated circuit. Alternatively, the multi-frequency driver200may be included in the timing controller300.

In addition, n scan lines SL1to SLn and n emission control lines EL1to ELn are shown inFIG.1, but embodiments according to the present invention are not limited thereto. For example, pixels PX located on a current horizontal line (or current pixel row) corresponding to a circuit structure of the pixels PX may be further connected to a scan line located on a previous horizontal line (or a previous pixel row) and/or a scan line located on a next horizontal line (or a next pixel row). For this purpose, dummy scan lines and/or dummy emission control lines not shown may be additionally formed in the pixel unit100.

According to some example embodiments, the display device1000may supply a first power supply VDD (e.g., supplying a high voltage), a second power supply VSS (e.g., supplying a low voltage or ground), and an initialization power supply Vint (e.g., supplying an initialization voltage) for driving the pixel PX to the pixel unit100.

FIG.2Ais a circuit diagram showing an example of a pixel circuit of one or more of the pixels PX included in a display device shown inFIG.1, andFIG.2Bis a timing diagram showing an example of an operation of the pixel circuit shown inFIG.2A.

Referring toFIGS.2A and2B, one or more of the pixels PX may each include first to seventh transistors T1to T7, a storage capacitor Cst, and a light emitting element LD.

Each of the first to seventh transistors T1to T7may be implemented as a P-type transistor, but is not limited thereto. For example, at least some of the first to seventh transistors T1to T7may be implemented as an N-type transistor. In addition, each active layer (or semiconductor layer) of the first to seventh transistors T1to T7may include a polysilicon-based semiconductor (e.g., low temperature poly-silicon semiconductor, etc.) or oxide semiconductor.

A first electrode of the first transistor T1(or driving transistor) may be connected to a second node N2or may be connected to a first power line via the fifth transistor T5. The second electrode of the first transistor T1may be connected to a first node N1or may be connected to an anode of the light emitting element LD via the sixth transistor T6. A gate electrode of the first transistor T1may be connected to a third node N3. The first transistor T1may control an amount of current flowing from the first power line (e.g., a power line transferring a voltage of the first power supply VDD) via the light emitting element LD to the second power line (e.g., a power line transferring a voltage of the second power supply VSS) in response to a voltage of the third node N3.

The second transistor T2may be connected between the data line DLj and the second node N2. A gate electrode of the second transistor T2may be connected to the scan line SLi. The second transistor T2may be turned on when the scan signal is supplied to the scan line SLi to electrically connect the data line DLj and the first electrode of the first transistor T1.

The third transistor T3may be connected between the first node N1and the third node N3. A gate electrode of the third transistor T3may be connected to the scan line SLi. The third transistor T3may be turned on when the scan signal is supplied to the scan line SLi to electrically connect the first node N1and the third node N3. Therefore, when the third transistor T3is turned on, the first transistor T1may be connected in a form of a diode.

The storage capacitor Cst may be connected between the first power supply VDD and the third node N3. The storage capacitor Cst may store a voltage corresponding to the data signal and the threshold voltage of the first transistor T1.

The fourth transistor T4may be connected between the third node N3and the initialization power supply Vint. A gate electrode of the fourth transistor T4may be connected to the previous scan line SLi−1. The fourth transistor T4may be turned on when the scan signal is supplied to the previous scan line SLi−1 to supply a voltage of the initialization power supply Vint to the first node N1. The voltage of the initialization power supply Vint may be set to have a lower voltage level than the data signal.

The fifth transistor T5may be connected between the first power line and the second node N2. A gate electrode of the fifth transistor T5may be connected to the emission control line ELi. The fifth transistor T5may be turned off when the emission control signal is supplied to the emission control line ELi, and may be turned on in other cases.

The sixth transistor T6may be connected between the first node N1and the light emitting element LD. A gate electrode of the sixth transistor T6may be connected to an emission control line ELi. The sixth transistor T6may be turned off when the emission control signal is supplied to the emission control line ELi, and may be turned on in other cases.

The seventh transistor T7may be connected between the initialization power supply Vint and the anode of the light emitting element LD. A gate electrode of the seventh transistor T7may be connected to the scan line SLi. The seventh transistor T7may be turned on when the scan signal is supplied to the scan line SLi to supply the initialization power supply Vint to the anode of the light emitting element LD.

The anode of the light emitting element LD may be connected to the first transistor T1via the sixth transistor T6, and the cathode of the light emitting element LD may be connected to the second power supply VSS (e.g., supplying a low voltage or ground). The light emitting element LD may generate light having a luminance (e.g., a set or predetermined luminance) in response to the current supplied from the first transistor T1.

FIG.2Bshows the previous scan signal SCAN[i−1] supplied to the previous scan line SLi−1, the scan signal SCAN[i] supplied to the scan line SLi, the emission control signal EM[i] supplied to the emission control line ELi, and a data signal DATA during one frame section.

The previous scan signal SCAN[i−1] may be supplied between the first time point t1and the second time point t2. A first pulse width PW1of a section in which the previous scan signal SCAN[i−1] has a turn-on voltage level may be less than one horizontal time1H.

The fourth transistor T4may be turned on, and the third node N3or the storage capacitor Cst may be initialized by the voltage of the initialization power supply Vint in response to the previous scan signal SCAN[i−1]. For example, a section between the first time point t1and the second time point t2may be an initialization section.

The scan signal SCAN[i] may be supplied between the second time point t2and the third time point t3.

The second transistor T2and the third transistor T3may be turned on, and a data signal (i.e., the data signal DATA[i] corresponding to the scan signal SCAN[i]) may be stored in the storage capacitor Cst in response to the scan signal SCAN[i] of a turn-on voltage level. The section between the second time point t2and the third time point t3may be a writing section.

In addition, the seventh transistor T7may be turned on in response to the scan signal SCAN[i], and the anode of the light emitting element LD may be initialized by the voltage of the initialization power supply Vint between the second time point t2and the third time point t3.

After the third time point t3, the emission control signal EM[i] may transition from a turn-off voltage level to a turn-on voltage level.

In response to the emission control signal EM[i] of the turn-on voltage level, the fifth transistor T5and the sixth transistor T6may be turned on, a current corresponding the voltage level (i.e., data signal DATA[i] corresponding to the scan signal SCAN[i]) of the third node N3may be supplied to the light emitting element LD, and the light emitting element LD may emit light with luminance corresponding to the current. A section after the third time point t3of one frame section may be a light emitting section.

According to some example embodiments, at least one of the scan signal SCAN[i], the data signal DATA[i], or the emission control signal EM[i] supplied to the pixel PX may vary according to the selected refresh rate.

FIG.3is a drawing showing an example of an image displayed on a display device shown inFIG.1.

Referring toFIGS.1and3, the pixel unit100may display a static image SI and a video VI simultaneously.

A scan direction to which the scan signal is sequentially supplied may be a first direction DR1.

The multi-frequency driver200may distinguish the first area DA1and the second area DA2with respect to the boundary pixel row BPL. The first area DA1may include an area where the video VI is displayed, and the second area DA2may include the static image SI other than the first area DA1.

The multi-frequency driver200may analyze the image data IDATA during the search period (e.g., a set or predetermined search period) to determine the boundary pixel row BPL of an optimal or desired position. According to some example embodiments, the multi-frequency driver200compares the image data of the previous frame corresponding to an image block IB with the image data of the current frame corresponding to an image block IB to determine whether or not the image block IB is a static image. A specific method of determining the second area DA2and the boundary pixel row BPL using the image block IB will be described in detail with reference toFIG.5or below.

The first area DA1may be defined as an area on the boundary pixel row BPL, and the first area DA1may be driven at the first refresh rate RR1. For example, the first refresh rate RR1may be set to 240 Hz, 120 Hz, 60 Hz, or the like. The remaining area except the first area DA1of the pixel unit100may be the second area, and the second area DA2may be driven at the second refresh rate RR2. The second refresh rate RR2may be a frequency lower than the first refresh rate RR1and may be set to 30 Hz, 10 Hz, 1 Hz, or the like.

The boundary pixel row BPL may be the top pixel row of the second area. In addition, a scan signal may be supplied at a frequency of the second refresh rate RR2from an i+1-th scan line SLi+1 connected to the boundary pixel row BPL to an n-th scan line SLn. On the other hand, the scan signal may be supplied at a frequency of the first refresh rate RR1from a first scan line SL1to an i-th scan line SLi.

According to some example embodiments, in response to the driving frequency of the scan signal, the data driver600may supply data signals corresponding to the first area DA1at the frequency of the first refresh rate RR1, and may supply data signals corresponding to the second area DA2at the frequency of the second refresh rate RR2.

Thus, as will be described in more detail below, according to some example embodiments, the display device may be configured to identify a boundary pixel row BPL separating a first display area DA1from a second display area DA2based on the images being displayed, where the first display area DA1displays images to be displayed at a first refresh rate (e.g., video images), and the second display area DA2displays images to be displayed at a second refresh rate (e.g., static images).

FIGS.4A and4Bare timing diagrams showing examples of signals supplied to a pixel unit to display an image ofFIG.3.

Referring toFIGS.1,3,4A and4B, the scan driver400may supply scan signals sequentially to scan lines (e.g., first to i-th scan lines SL1to SLi) of first area DA1at the first refresh rate RR1, and may supply scan signals sequentially to scan lines (e.g., i+1-th to n-th scan lines SLi+1 1 to SLn) of the second area DA2at the second refresh rate RR2.

The timing diagrams ofFIGS.4A and4Bshow only a scan signal whose refresh rate (or frequency) changes according to a command of the multi-frequency driver200among a plurality of scan signals supplied to one pixel. For example, when a plurality of scan signals are supplied to the pixel, some scan signals may be supplied at one frequency regardless of a change of a refresh rate for driving the pixel.

For example, in a case of the pixel PX ofFIG.2A, different scan signals may be supplied to the second transistor T2and the third transistor T3according to the refresh rate. For example, the scan signal supplied to the third transistor T3may be supplied at the frequency changing according to a change of the refresh rate (i.e., in response to the masking signal MS). On the other hand, the scan signal supplied to the second transistor T2may be supplied at a constant frequency regardless of the change of the refresh rate. In this case,FIGS.4A and4Bshows the scan signal supplied to the third transistor T3.

According to some example embodiments, dummy scan line SL0is for supplying a dummy scan signal for driving pixels PX in a first pixel row.

As shown inFIG.4A, the scan signal may be supplied to lines SL1to SLi corresponding to the first area DA1at a frequency of 120 Hz, and the scan signal may be supplied to lines SLi+1 to SLn corresponding to the second area DA2at a frequency of 60 Hz. Therefore, a power consumption due to a toggling of the scan signal supplied to the second area DA2may be reduced.

On the other hand, the emission control signal may be supplied to the emission control lines EL1to ELn at the same frequency (e.g., 120 Hz) as the first refresh rate RR1regardless of the change of the refresh rate between display areas.

However, this is as an example, the emission control signal may be supplied to the emission control lines ELi+1 to ELn of the second area DA2at a frequency of the second refresh rate RR2.

For example, as shown inFIG.4B, the emission control signal supplied to the second area DA2may have a turn-off level at a frequency of the second refresh rate RR2. Accordingly, a toggling of the emission control signal corresponding to the second area DA2may be reduced, thereby reducing power consumption.

FIG.5is a block diagram showing an example of a multi-frequency driver included in a display device ofFIG.1, andFIG.6is a block diagram showing an example of an image analyzer included in a multi-frequency driver ofFIG.5.

Referring toFIGS.1,3,5and6, the multi-frequency driver200may include an image analyzer220, a block controller240and a frequency controller260.

The image analyzer220may receive image data IDATA from the processor10, and may receive information on an image block IB of which the image data is compared from the block controller240. The image analyzer220may compare image data IB_D1of the previous frame of the image block IB included in the pixel unit100with image data IB_D2of the current frame the image block IB to determine whether or not the image block IB is a static image. According to some example embodiments, the image block IB may include a plurality of pixel rows. A size of the image block IB may be adjusted according to a use environment, a user setting, and the like.

According to some example embodiments, the image analyzer220may determine the static image based on a difference between a checksum (e.g., first checksum CS1) of the image data IB_D1of the previous frame of the image block IB and a checksum (e.g., second checksum CS2) of the image data IB_D2of the current frame of the image block IB. For example, when the difference between the first checksum CS1and the second checksum CS2is greater than the reference value (e.g., a set or predetermined reference value) (e.g., 0), the image analyzer220may determine that the corresponding image block IB includes a video (or is not a static image), and may provide a first result VD to the block controller240.

When the first checksum CS1and the second checksum CS2are equal (or less than or equal to the reference value), the image analyzer220determines that the corresponding image block IB is a static image, and may provide the second result SD to the block controller240.

However, this is an example, but a method of judging the static image is not limited thereto. Whether or not the image block IB is a static image may be determined through various known algorithms and/or hardware configurations.

Meanwhile, the static image only needs to check whether or not the image data of the corresponding area matches, so that only a least significant bit (LSB) of the data checksum may be compared. For example, only the last 4 bits of the sum of the image data of the corresponding image block IB may be compared. Accordingly, a burden for comparing data is reduced, and a memory configuration such as a frame memory is not used.

According to some example embodiments, the image analyzer220may include a data selector222, a checksum calculator224, and a comparator226.

The image analyzer220may receive information on image data IDATA and an image block IB. The image analyzer220may provide image data information of the image block IB selected from the image data IDATA of the entire pixel unit100to the checksum calculator224.

The checksum calculator224may calculate the checksums CS1and CS2of the image data IB_D1and IB_D2corresponding to the image block IB.

The comparator226may output a first result VD or a second result SD based on the difference between the first checksum CS1and the second checksum CS2.

The block controller240may determine a size, a number and a position of the image block IB in which it is to be determined whether or not the image block is a static image based on the first result VD or the second result SD received from the image analyzer220. In addition, the block controller240may supply first static image area data SIA1or second static image area data SIA2including information on an area determined as the static image in the current frame to the frequency controller260based on the first result VD or the second result SD.

According to some example embodiments, when the first image block (e.g., a set or predetermined first image block) is determined to be a static image, the block controller240may provide information on a new second image block to the image analyzer220. According to some example embodiments, the second image block may be an image block adjacent to the first image block in the second direction DR2. The image analyzer220may determine whether or not the second image block is a static image. The block controller240and the image analyzer220may repeat the operation until a video is detected.

When it is determined that all of the image blocks corresponding to the entire pixel unit100are static images, the block controller240may provide the first static image area data SIA1to the frequency controller260. In this case, the first static image area data SIA1may indicate the entire pixel unit100.

According to some example embodiments, when it is determined that the image block is not a static image, the block controller240may reduce a size of the image block by changing a position of the top pixel row of the image block in the first direction DR1. The block controller240may provide information on the reduced image block to the image analyzer220. The image analyzer220may determine whether or not the reduced image block is a static image. In this case, when the reduced image block is determined as a static image, the block controller240may provide the first static image area data SIA1to the frequency controller260. The first static image area data SIA1may indicate an area from the top pixel row to the last pixel row of the reduced image blocks.

Meanwhile, the block controller240and the image analyzer220may repeat the operation of comparing the image data by reducing the corresponding image block until the static image is detected. However, when the size of the image block is reduced to less than or equal to the number of pixel rows (e.g., a set or predetermined number of pixel rows), the block controller240may stop reducing the image block and provide the second static image area data SIA2to the frequency controller260. In this case, the second static image area data SIA2may be data that finally determines the second area DA2. That is, the top pixel row included in the second static image area data SIA2is determined as a boundary pixel row BPL.

The frequency controller260may apply the second refresh rate RR2to the image block determined as the static image based on the first static image area data SIA1or the second static image area data SIA2. The frequency controller260may generate a low frequency driving signal LFD indicating a first pixel row to which the second refresh rate RR2is applied based on static image area data SIA. The frequency controller260may supply the low frequency driving signal LFD to the timing controller300.

The low frequency driving signal LFD includes information on the top pixel row included in the static image area data SIA. Accordingly, a position of a display area driven at the second refresh rate RR2may be changed. According to some example embodiments, the low frequency driving signal LFD may further include frequency information of the second refresh rate RR2.

According to some example embodiments, when the image data of the static image area or the second area is changed, the frequency controller260may output an initialization signal INS for initializing the static image area or the second area. The scan driver400may supply the scan signal to the entire scan lines SL1to SLn at the first refresh rate RR1in response to the initialization signal INS.

As described above, by repeating the operation of comparing the image data while changing the position, the size, and the number of the image block, an accurate boundary between the first area DA1and the second area DA2may be detected. In addition, as the area to which the second refresh rate is applied gradually increases, an optimal or desired boundary pixel row BPL may be determined.

Therefore, power consumption for driving at a multiple frequency (or multiple refresh rate) may be minimized.

FIGS.7A to7Iare drawings showing a driving method of a display device according to some example embodiments of the present invention.

Referring toFIGS.1,7A to7I, the display device1000simultaneously displaying the video VI and the static image SI may determine the boundary pixel row BPL, which is the top pixel row of the second area DA2, based on the result of comparing the image data IDATA during a plurality of frames.

As shown inFIG.7A, the multi-frequency driver200may determine whether or not the first image block IB1is a static image. The multi-frequency driver200may determine whether or not the first image block IB1is a static image based on a difference between the image data of the previous frame (e.g., k−1-th frame (k is a natural number)) of the first image block IB1and the image data of the current frame (e.g., k-th frame).

When the first image block IB1is determined as a static image, the multi-frequency driver200may generate a first low frequency driving signal LFD1corresponding to the top pixel row of the first image block IB1.

The timing controller300and the scan driver400may drive the first image block IB1at the second refresh rate RR2in the current frame based on the first low frequency driving signal LFD1. According to some example embodiments, the emission driver500and/or the data driver600may drive the first image block IB1at the second refresh rate RR2. Accordingly, the multi-frequency driving may be performed in real time without losing a frame by analyzing the image data received from the processor10immediately.

The remaining area except the first image block IB1is driven at the first refresh rate RR1.

As shown inFIG.7B, for the image data of the k+1-th frame, the multi-frequency driver200may determine whether or not the first image block IB1and the second image block IB2are static images. The second image block IB2may be adjacent to the first image block IB1in the second direction DR2. That is, the determination of whether or not the image block is a static image may be performed in a reverse direction of the scan direction.

When the first and second image blocks IB1and IB2are determined as static images, the multi-frequency driver200may generate a second low frequency driving signal LFD2corresponding to the top pixel row of the second image block IB2. Accordingly, the first and second image blocks IB1and IB2may be driven at the second refresh rate RR2in a k+1-th frame. Next, the operation shown inFIG.7Cmay be performed.

Meanwhile, inFIG.7B, when it is determined that the first image block IB1is not a static image, the operation for comparing the image data may be reset. For example, the operation for comparing the image data is stopped, and after time elapses (e.g., a set or predetermined time elapses), the operation ofFIG.7Amay be performed.

As shown inFIG.7C, the multi-frequency driver200may determine whether or not the first image block IB1, the second image block IB2, and the third image block IB3are static images for the image data of a k+2-th frame. Because the operation ofFIG.7Cis substantially the same as the operation ofFIG.7B, redundant descriptions will be omitted.

The multi-frequency driver200may generate a third low frequency driving signal LFD3corresponding to the top pixel row of the third image block IB3. Accordingly, first to third image blocks IB1to IB3may be driven at the second refresh rate RR2in the k+2-th frame.

Next, as shown inFIG.7D, the determination of whether or not first to fourth image blocks IB1to IB4are static images may be performed for image data of the k+3-th frame. When the fourth image block IB4includes a video, an output of the third low frequency driving signal LFD3may be maintained. Therefore, only first to third image blocks IB1to IB3may be driven at the second refresh rate RR2.

Next, as shown inFIGS.7E and7F, the fourth image block IB4may be reduced (i.e., shown as IB4′ and IB4″) until no video is included in the fourth image block IB4. The multi-frequency driver200may also perform a static image determination on the reduced fourth image block IB4′ and IB4″. The operation of determining the static image by reducing the image block may be repeated until a boundary between the static image and the video is detected. However, when the reduced image to reduce a burden of a system and the operation has a set or predetermined size or less, the operation for detecting the boundary may be stopped.

According to some example embodiments, when the reduced fourth image block IB4″ has less than or equal to the number of pixels rows (e.g., a set or predetermined number of pixel rows), the multi-frequency driver200may stop reducing the image block, and determine the top pixel row of the reduced fourth image block IB4″ as the boundary pixel row BPL. For example, when the reduced fourth image block IB4″ includes 20 or less pixel rows, a reduction of the image block may be stopped.

The multi-frequency driver200may output a fourth low frequency driving signal LFD4corresponding to the boundary pixel row BPL. Accordingly, the last pixel row from the boundary pixel row BPL may be determined as the second area DA2, and be driven at the second refresh rate RR2.

Thus, the boundary between the first area DA1and the second area DA2may be detected relatively accurately by the process ofFIGS.7A to7F. In addition, during the search period for detecting the second area DA2(and boundary pixel row BPL), a size of the area driven at the second refresh rate RR2may be gradually increased to the second direction DR2. Therefore, the number of scan lines and/or emission control lines driven at the second refresh rate RR2may gradually increase during the search period.

Meanwhile, a static image detection and a multi-frequency driving are performed at intervals of 1 frame inFIGS.7A to7F, but the static image detection and the multi-frequency driving is not limited thereto. For example, after generating the low frequency driving signal LDF by comparing the image data in the k-th frame, the corresponding area may be driven at the second refresh rate RR2based on the low frequency driving signal LDF in the k-th frame.

Next, as shown inFIG.7G, the multi-frequency driver200may reset the entire second area to one new image block N_IB and perform a static image determination of the new image block N_IB. Because the static image is monitored by one image block, a usage of a resource for comparing image data may be reduced, and a sensing of an image change in the new image block N_IB may be easy.

Next, as shown inFIG.7H, an image change event in which an image of the second area DA2is changed may occur in the j-th frame (where j is a natural number). For example, a position of a video may be changed (from VI1to VI2) or a size of a video may be changed. Alternatively, an image of the second area DA2may be changed by a touch of the user. In this case, as shown inFIG.7I, the multi-frequency driver200may generate the initialization signal to provide it to the timing controller300and/or the scan driver400. The initialization signal may include a command to initialize (or delete) the position of the boundary pixel row BPL and the second area DA2.

Accordingly, the scan driver400may supply the scan signal to the scan lines SL1to SLn at the first refresh rate RR1in response to the initialization signal. That is, the entire pixel unit100may be driven at the first refresh rate RR1.

Next, the operation ofFIG.7Amay be resumed.

As described above, the display device1000and its driving method according to some example embodiments of the present invention may perform image data comparison in real time without configuration of a frame memory and the like and may detect an optimal or desired boundary pixel row BPL between the first area DA1and the second area DA2while gradually increasing an area to which the second refresh rate RR2is applied for a short time. Accordingly, power consumption for driving at a multiple frequency (or multiple refresh rate) may be minimized without increasing a cost for detecting the boundary pixel row detection.

FIG.8is a drawing showing an example of an operation of a display device ofFIG.1.

Referring toFIGS.1,7H,7I and8, when the image change event of the second area DA2occurs, the display device1000may be driven at a single frequency by escaping the multi-frequency driving.

A first case CASE1shows an example embodiment in which the display device is driven at a single frequency by the driving ofFIGS.7H and7I. That is, when an image change event of the second area DA2occurs in the j-th frame, a single frequency driving may be delayed by one frame or more by a static image determination operation of the multi-frequency driver200in the j+1-th frame.

According to some example embodiments, when the image change event of the second area DA2occurs, the processor10may provide a command signal which command to drive immediately at a single frequency to the multi-frequency driver200and/or the timing controller300. For example, when an image change event of the second area DA2occurs in the j-th frame, the pixel unit100may be driven at a single frequency (single refresh rate) in the j+1-th frame.

According to some example embodiments, when the image change event of the second area DA2occurs in the j-th frame, the processor10may change the image data corresponding to the second area DA2in the j-th frame, and may supply the changed image data CDAA to the multi-frequency driver200(in a second case CASE2). For example, the processor10may change image data of one pixel included in the last pixel row. Accordingly, the multi-frequency driver200may detect a change of image data of the second area DA2. The multi-frequency driver200may output an initialization signal (shown as INS inFIG.5) In the j-th frame, and the pixel unit100may be driven at a single frequency in the j+1-th frame.

Therefore, the single frequency driving may be performed without delay, and an image quality may be improved when switching from the multi frequency driving to the single frequency driving.

FIG.9is a flowchart showing a driving method of a display device according to some example embodiments of the present invention.

Referring toFIG.9, a driving method of the display device may determine whether or not the first image block is a static image by comparing the image data of the previous image frame of the first image block with the image data of the current image frame of the first image block 9 (S110). When the first image block is not a static image, the first image block may be driven at the first refresh rate (S130), and a size of the first image block may be reduced in the first direction (S140). Next, one of the pixel rows included in the reduced first image block may be determined as the boundary pixel row, and a static image area included in the boundary pixel row may be determined (S160).

The boundary pixel row may be a pixel row separating the static image area and a video area.

When the first image block is a static image, the first image block may be driven at the second refresh rate lower than the first refresh rate (S120). In this case, whether or not the second image block adjacent to the first image block in a reverse direction of the first direction is a static image may be determined again (S110).

According to some example embodiments, when the static image area is determined, the static image area may be driven at the second refresh rate, and the video area may be driven at the first refresh rate (S170). The static image area may include an area from the boundary pixel row to the last pixel row.

According to some example embodiments, a size of an area driven at the second refresh rate may be gradually increased during the search period for determining the boundary pixel row.

Because the driving method of the display device including the operations S110to S170and an effect thereof are shown in and the effect is described in detail with reference toFIGS.1to7F, redundant descriptions will be omitted.

While aspects of some example embodiments of the invention are described with reference to the attached drawings, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims, and their equivalents.