Display device and driving method thereof

Abstract

A display device and a method for driving the same are provided. The display device includes: a screen saver for displaying an image at reduced brightness in a screen save mode by reducing a scaling factor from a first value based on a period of time during which the image is displayed as a still image being longer than a reference time; and an overcurrent protection circuit for detecting an overcurrent and cutting off power to the display device based on a comparison between a predetermined current value reduced according to the scaling factor and a driving current supplied to a display panel on which the image is displayed.

Description

Technical Field

[0001] The present disclosure relates to a display device and a method for driving the display device. More specifically, embodiments of the present disclosure relate to a display device including an overcurrent protection circuit and a method for driving the display device. Background Art

[0002] Among various types of display devices for displaying images, organic light emitting diode (OLED) displays have recently attracted much attention due to their advantageous characteristics over conventional display devices.

[0003] OLED displays include organic light-emitting diodes (OLEDs), which emit light through the recombination of electrons and holes. Due to their self-emissive nature, OLED displays do not require a separate light source, allowing them to be thinner and lighter than liquid crystal displays. OLED displays also exhibit high-quality characteristics such as low power consumption, high brightness, and a fast response time.

[0004] Organic light-emitting diodes (OLEDs) are driven using a data voltage corresponding to an image data signal and a power supply voltage applied between the anode and cathode of the OLED. During manufacturing or operation, a power line to which the power supply voltage is applied may short to another wire, such as a data line to which the data voltage is applied. In this case, an overcurrent may flow between the power supply and the display panel, causing damage to the OLED display, such as degradation of the OLED due to the overcurrent.

[0005] To prevent such damage to the OLED display due to overcurrent, an overcurrent protection circuit may be used to shut down the power supply by detecting overcurrent flowing in the power supply line.

[0006] When the detected current is greater than a predetermined current value, the overcurrent protection circuit can shut down the power supply. However, if the predetermined current value of the overcurrent protection circuit is set to be greater than the maximum current that can flow to the display panel, the overcurrent protection circuit may not be sufficient to protect the OLED display.

[0007] On the other hand, when the image is a still image that is displayed for a predetermined time or longer, the display device may display the image in screen saver mode. In screen saver mode, the brightness of the image may be reduced to prevent afterimages. When displaying an image in screen saver mode, the current flowing through the display panel decreases. In this case, overcurrent may still flow at a low current in screen saver mode, and because the predetermined current value used to determine overcurrent does not change when the image is displayed in screen saver mode, the overcurrent protection circuit may not operate as intended.

[0008] The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0009] The present disclosure provides a display device capable of adaptively operating an overcurrent protection circuit in a screen power saving mode and a method of driving the display device.

[0010] A display device according to an exemplary embodiment of the present disclosure includes: a screen energy saver for displaying an image with reduced brightness in a screen power saving mode by reducing a scaling factor from a first value based on a time period during which the image is displayed as a still image being longer than a reference time; and an overcurrent protection circuit for detecting an overcurrent and cutting off power to the display device based on a predetermined current value reduced according to the scaling factor and a comparison between the predetermined current value and a driving current supplied to a display panel in which an image is displayed.

[0011] The display device further includes a power supply that supplies a driving current to the display panel, wherein the overcurrent protection circuit supplies an enable signal having a cutoff voltage to the power supply to turn off the power supply based on a duration in which the driving current is greater than a predetermined current value being longer than a reference time.

[0012] The overcurrent protection circuit may transmit a return signal to the screen energy saver based on detection of overcurrent in the screen energy saver mode, and the screen energy saver may change the scale factor to a first value according to the return signal and may display an image in the normal mode.

[0013] The overcurrent protection circuit may set a predetermined current value as an original value in the normal mode, and compare the driving current with the predetermined current value in the normal mode to determine to power off the display device.

[0014] The display device may further include: a load calculator that calculates a frame load based on the sum of data values for multiple pixels of the display panel, and calculates a load deviation by comparing the frame load of a previous image frame with the frame load of a current image frame, wherein based on the load deviation, an image can be displayed in a screen power saving mode.

[0015] Based on the duration of the load deviation being less than or equal to the reference deviation being longer than the reference time, the image may be displayed in the screen power saving mode.

[0016] The screen energy saver may subtract a constant value from the scale factor for each image frame to sequentially decrease the scale factor.

[0017] The screen energy saver may sequentially reduce the scale factor by multiplying the scale factor by the reduction ratio for each image frame.

[0018] Screen Saver may reduce the scale factor until the scale factor has a minimum scale factor value.

[0019] According to another exemplary embodiment of the present disclosure, a driving method of a display device includes: monitoring a driving current provided to a display panel displaying an image; displaying an image with reduced brightness in a screen power saving mode by reducing a scaling factor from a first value based on a time period during which the image is displayed as a still image being longer than a reference time; reducing a predetermined current value according to the scaling factor; comparing the predetermined current value with the driving current to detect occurrence of an overcurrent; in response to detecting occurrence of an overcurrent in the screen power saving mode, changing the scaling factor to a first value and changing the predetermined current value to an original value to display an image in a normal mode; and powering off the display device in the normal mode based on detection of the overcurrent, wherein the overcurrent is detected based on a comparison between the driving current provided to the display panel and the predetermined current value.

[0020] The step of displaying the image in the screen power saving mode may include sequentially reducing the scale factor by subtracting a constant value from the scale factor.

[0021] The displaying of the image in the screen power saving mode may include sequentially reducing the scale factor by multiplying the scale factor by a reduction ratio.

[0022] The step of displaying the image in the screen power saving mode may include reducing the scale factor until the scale factor has a minimum scale factor value.

[0023] The display device may be powered off based on a duration in which the driving current is greater than a predetermined current value being longer than a reference time.

[0024] The method of driving a display device may further include calculating a frame load based on a sum of data values for a plurality of pixels of the display panel; and calculating a load deviation by comparing the frame load of a previous image frame with the frame load of a current image frame.

[0025] Based on the duration of the load deviation being less than or equal to the reference deviation being longer than the reference time, the image may be displayed in the screen power saving mode.

[0026] The driving method of the display device may further include determining whether the load deviation is greater than a reference deviation; and resetting the scale factor to a first value and resetting a save count indicating a number of frame counts for displaying a still image to 0 based on the load deviation being greater than the reference deviation.

[0027] The driving method of the display device may further include: adding 1 to the stored count based on the load deviation being not greater than the reference deviation.

[0028] The driving method of the display device may further include determining whether the holding count is greater than a reference time, and based on the holding count being greater than the reference time, reducing a scale factor by a predetermined value and reducing the predetermined current value according to the scale factor.

[0029] The operations of determining whether the load deviation is greater than the reference deviation, adding 1 to the save count, determining whether the save count is greater than the reference time, reducing the proportional factor by a predetermined value, and reducing the predetermined current value according to the proportional factor can be performed during a frame interrupt of one image frame and before outputting the image data signal corresponding to the next frame.

[0030] The overcurrent protection circuit operates adaptively in the screen power saving mode to prevent organic light emitting diodes from degrading. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a block diagram illustrating a display device according to an exemplary embodiment of the present disclosure.

[0032] Figure 2 is a flowchart for driving an overcurrent protection circuit and a screen energy saver according to an exemplary embodiment of the present disclosure.

[0033] Figure 3 is a flowchart for shutting down a power supply through an overcurrent protection circuit according to an exemplary embodiment of the present disclosure.

[0034] Figure 4 is a flowchart for shutting down a power supply through an overcurrent protection circuit according to another exemplary embodiment of the present disclosure.

[0035] Figure 5 is a timing diagram of a display device according to an exemplary embodiment of the present disclosure.

[0036] Figure 6 is a timing diagram of a display device in a screen power saving mode according to an exemplary embodiment of the present disclosure.

[0037] Figure 7 is a circuit diagram illustrating a pixel according to an exemplary embodiment of the present disclosure.

[0038] Figure 8 is a flowchart for driving a display device according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0039] Hereinafter, embodiments of the present disclosure will be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the present disclosure are shown. As will be appreciated by those skilled in the art, the described embodiments may be modified in various forms, configurations, and ways without departing from the spirit or scope of the present disclosure.

[0040] In addition, in the exemplary embodiments, the same reference numerals designate the same elements having the same and / or substantially similar configurations. Elements may be representatively described in one exemplary embodiment, while configurations different from the first exemplary embodiment will be described in other exemplary embodiments.

[0041] Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive, and like reference numerals designate like elements throughout the specification unless expressly stated otherwise.

[0042] In addition, unless explicitly described to the contrary, the word “comprise” and variations such as “comprising” and “comprises” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

[0043] Figure 1 is a block diagram illustrating a display device according to an exemplary embodiment of the present disclosure.

[0044] Reference Figure 1 The display device includes a signal controller 100, a load calculator 110, a screen energy saver 120, an over current protection (OCP) circuit 130, a current sensor 140, a gate driver 200, a data driver 300, a power supply 400 and a display panel 600.

[0045] Figure 1 The load calculator 110, screen energy saver 120, overcurrent protection circuit 130, and current sensor 140 are shown as being separately provided. However, it should be understood that the present disclosure is not limited thereto. For example, in some embodiments, at least one of the load calculator 110, screen energy saver 120, overcurrent protection circuit 130, and current sensor 140 may be included in the signal controller 100. In yet another embodiment, the load calculator 110 may be included in the screen energy saver 120, and / or the current sensor 140 may be included in the overcurrent protection circuit 130.

[0046] The signal controller 100 receives an input image signal ImS and a control signal CONT input from an external device. The input image signal ImS includes brightness information of a plurality of pixels PX in the display panel 600. The brightness information has a predetermined number of grayscale levels. Examples of the control signal CONT include, but are not limited to, a horizontal synchronization signal, a vertical synchronization signal, and a main clock signal.

[0047] The signal controller 100 generates a first drive control signal CONT1, a second drive control signal CONT2, and an image data signal DAT based on an input image signal ImS and a control signal CONT. The signal controller 100 can generate the image data signal DAT by dividing the input image signal ImS into frames according to a vertical synchronization signal and dividing the input image signal ImS into gate lines according to a horizontal synchronization signal.

[0048] In addition, the signal controller 100 receives a scale factor SF from the screen energy saver 120. The signal controller 100 may generate an image data signal DAT by applying the scale factor SF to the input image signal ImS. For example, the signal controller 100 may adjust the brightness of the image data signal DAT by applying the scale factor SF to the input image signal ImS.

[0049] The signal controller 100 transmits the first driving control signal CONT1 to the gate driver 200. The signal controller 100 transmits the image data signal DAT and the second driving control signal CONT2 to the data driver 300. The signal controller 100 may also transmit the image data signal DAT to the load calculator 110.

[0050] The display panel 600 may include a plurality of pixels PX to display an image. The area where the plurality of pixels PX are arranged to display an image is referred to as a display area or screen. The display panel 600 includes a plurality of scan lines and a plurality of data lines connected to the plurality of pixels PX. The plurality of scan lines may extend substantially parallel to each other in the row direction. The plurality of data lines may extend substantially parallel to each other in the column direction. The plurality of pixels PX may be arranged in an area where the plurality of scan lines and the plurality of data lines intersect. Depending on the structure of the plurality of pixels PX included in the display panel 600, the signal lines may be modified in various ways. For example, the display panel 600 may further include a plurality of sensing lines extending in the row direction, a plurality of emission lines extending in the row direction, and a plurality of receiving lines extending in the column direction. It should be understood that the configuration of the display panel 600 is not limited to the specific examples described herein.

[0051] The gate driver 200 is connected to a plurality of scan lines. The gate driver 200 generates a plurality of scan signals G[1] to G[n] based on a first drive control signal CONT1. The plurality of scan signals G[1] to G[n] may transmit a gate-on voltage or a gate-off voltage. The gate driver 200 may sequentially apply the scan signals G[1] to G[n] to the plurality of scan lines.

[0052] The data driver 300 is connected to a plurality of data lines. The data driver can sample and hold the image data signal DAT according to the second drive control signal CONT2, and apply a plurality of data voltages D[1] to D[m] to the plurality of data lines. The data driver 300 applies the data voltages D[1] to D[m] having a predetermined voltage range to the plurality of data lines corresponding to the gate-on voltages of the scan signals G[1] to G[n].

[0053] The power supply 400 generates power supply voltages ELVDD and ELVSS. The power supply voltages ELVDD and ELVSS include a first power supply voltage ELVDD and a second power supply voltage ELVSS. The first power supply voltage ELVDD and the second power supply voltage ELVSS are applied to a plurality of pixels PX of the display panel 600. The first power supply voltage ELVDD and the second power supply voltage ELVSS are voltages for driving the plurality of pixels PX. The first power supply voltage ELVDD may be a high-level voltage higher than the second power supply voltage ELVSS and supplies current to the anode of each of the plurality of pixels PX. The second power supply voltage ELVSS may be a low-level voltage lower than the first power supply voltage ELVDD and is applied to the cathode of each of the plurality of pixels PX.

[0054] The load calculator 110 receives the image data signal DAT and calculates a frame load based on the image data signal DAT. The frame load refers to the load added to the display panel 600 to display an image of one frame. The frame load may be the sum of the data values for the plurality of pixels PX included in the display panel 600. The load calculator 110 may calculate a load deviation dL by comparing the frame load of the previous frame (image frame) with the frame load of the current frame. The load deviation dL refers to the difference between the frame load of the previous frame and the frame load of the current frame. The load calculator 110 may transmit the load deviation dL to the screen energy saver 120.

[0055] In another embodiment, the load calculator 110 may transmit the calculated frame load to the screen saver 120, and the screen saver 120 may calculate a load deviation dL by comparing the frame load of the previous frame with the frame load of the current frame. Based on the load deviation dL, the screen saver 120 may cause the display device to display an image in screen saver mode. The screen saver mode includes gradually reducing the brightness of a still image when the image is displayed for a reference time. For example, the screen saver 120 monitors the load deviation dL and, if the load deviation dL is less than or equal to the reference deviation RD for a period longer than the reference time, reduces the scale factor SF to display the image in screen saver mode. In one embodiment, the screen saver 120 may output the scale factor SF as 1 in normal mode and a value less than 1 in screen saver mode. The screen saver 120 may sequentially reduce the scale factor SF in screen saver mode to gradually reduce the brightness of the image. The screen saver 120 transmits the scale factor SF to the signal controller 100 and the overcurrent protection circuit 130.

[0056] The signal controller 100 generates the image data signal DAT by reflecting the scale factor SF which may sequentially decrease in the screen saving mode, and the brightness of the image may gradually decrease as the load deviation dL continues to be less than or equal to the reference deviation RD in the screen saving mode.

[0057] The overcurrent protection circuit 130 may include a predetermined current value for detecting overcurrent. The overcurrent protection circuit 130 may determine a current exceeding the predetermined current value as an overcurrent. In one embodiment, the overcurrent protection circuit 130 may change the predetermined current value from the original predetermined current value (i.e., the original value) according to the scale factor SF. For example, the overcurrent protection circuit 130 may reduce the predetermined current value by multiplying the scale factor SF by the predetermined current value in the screen power saving mode. When the received scale factor SF is 1, the overcurrent protection circuit 130 may reset the predetermined current value to the original predetermined current value. In this way, in the screen power saving mode, the predetermined current value of the overcurrent protection circuit 130 may dynamically change corresponding to the scale factor SF.

[0058] The current sensor 140 measures a driving current DC of the power voltages ELVDD and ELVSS supplied to the display panel 600. The measured driving current DC is transmitted to the overcurrent protection circuit 130.

[0059] If the driving current DC exceeds the predetermined current value, the overcurrent protection circuit 130 may cut off the power to the display device. A single comparison of the driving current DC with the predetermined current value may not be enough to determine power failure of the display device. For example, if the driving current DC exceeds the predetermined current value and is maintained for longer than a reference time, the overcurrent protection circuit 130 may perform the comparison process more than once to signal the power supply 400 to cut off the power to the display device.

[0060] The overcurrent protection circuit 130 may drive the power supply 400 in a normal mode by supplying an enable signal EN having an on-voltage to the power supply 400. According to the enable signal EN having the on-voltage, the power supply 400 supplies a driving current DC to the display panel 600. In the case where the driving current DC is greater than a predetermined current value for a period longer than a reference time, the overcurrent protection circuit 130 may apply the enable signal EN having an off-voltage to the power supply 400 to shut down the power supply 400.

[0061] If an overcurrent is detected in the screen power saving mode, the overcurrent protection circuit 130 may transmit a return signal RS to the screen energy saver 120. The return signal RS indicates that the screen power saving mode is canceled and the display device may be switched to the normal mode. The screen energy saver 120 may output the scale factor SF as the original value 1 according to the return signal RS, and the display device may be switched to the normal mode. During the switch to the normal mode, the signal controller 100 outputs the image data signal DAT in the normal mode, and the overcurrent protection circuit 130 sets the predetermined current value to the original value. When an image is displayed in the normal mode, the overcurrent protection circuit 130 compares the driving current DC with the predetermined current value, and if the driving current DC is greater than the predetermined current value, applies the enable signal EN having a cut-off voltage to the power supply 400 to turn off the power supply 400.

[0062] The overcurrent protection circuit 130 may reduce the predetermined current value in response to the reduced image brightness in the screen saving mode. Thus, in the screen saving mode, the overcurrent protection circuit 130 may adaptively operate corresponding to the reduced driving current.

[0063] Next, refer to Figures 2 to 6 A driving method of the overcurrent protection circuit 130 and the screen energy saver 120 will be described.

[0064] Figure 2 is a flowchart for driving an overcurrent protection circuit and a screen energy saver according to an exemplary embodiment of the present disclosure. Figure 3 is a flowchart for shutting down a power supply through an overcurrent protection circuit according to an exemplary embodiment of the present disclosure. Figure 4is a flowchart for shutting down a power supply through an overcurrent protection circuit according to another exemplary embodiment of the present disclosure. Figure 5 is a timing diagram of a display device according to an exemplary embodiment of the present disclosure. Figure 6 is a timing diagram of a display device in a screen power saving mode according to an exemplary embodiment of the present disclosure.

[0065] Reference Figure 2 , generating a frame interrupt (S10). The frame interrupt may be generated when the output of the image data signal DAT of one frame ends.

[0066] When a frame interruption occurs, the overcurrent protection circuit 130 increments the frame count FC by 1 ( S11 ).

[0067] The current sensor 140 measures the driving current DC ( S12 ) and transmits the measured driving current DC to the overcurrent protection circuit 130 .

[0068] The overcurrent protection circuit 130 determines whether the frame count FC is greater than the reference frame count RF (S13). The reference frame RF indicates the number of frame counts used to detect overcurrent. The reference frame RF can be predetermined. In some embodiments, the reference frame RF can represent a time period corresponding to the predetermined frame count. In this case, the frame count FC can also represent a time period. For example, the reference frame RF can be set to 600 frames or 10 seconds.

[0069] If the frame count FC is greater than the reference frame RF, the overcurrent protection circuit 130 resets the frame count FC to 0 (S14), resets the peak count PC to 0 (S15), and returns to the frame interruption step (S10) to wait for the next occurrence of the frame interruption. The peak count PC indicates the number of consecutive frame counts for which the overcurrent protection circuit 130 determines the drive current DC to exceed the predetermined current value.

[0070] If the frame count FC is not greater than the reference frame RF, the overcurrent protection circuit 130 determines whether the driving current DC is greater than a predetermined current value RC (S16).

[0071] If the driving current DC is not greater than the predetermined current value RC, the overcurrent protection circuit 130 returns to the frame interrupt step (S10) to wait for the next occurrence of the frame interrupt.

[0072] If the driving current DC is greater than the predetermined current value RC, the overcurrent protection circuit 130 increases the peak count PC by 1 (S17). In the case where the driving current DC is measured to be greater than the predetermined current value RC, the overcurrent protection circuit 130 determines this as a preliminary overcurrent, and the peak count PC indicates the number of occurrences of the preliminary overcurrent.

[0073] The overcurrent protection circuit 130 also determines whether the peak count PC is greater than the reference peak count RP (S18). The reference peak count RP is the number of consecutive frame counts in which a preliminary overcurrent is detected to determine the overcurrent that occurred during the reference frame RF. The reference peak number RP may be a predetermined value representing the duration of an image frame in which the drive current DC is greater than the predetermined current value RC. For example, the reference peak number RP may be determined to be 5 (or 5 frame counts) to 10 (or 10 frame counts). If the peak count PC is not greater than the reference peak number RP, the overcurrent protection circuit 130 returns to the frame interrupt step (S10) to wait for the next occurrence of the frame interrupt. When the peak count PC is greater than the reference peak number RP, the overcurrent protection circuit 130 determines that an overcurrent has occurred and starts process A for shutting down the power supply 400. You can refer to Figure 3 or Figure 4 The process A for shutting down the power supply 400 is explained.

[0074] That is, if the number of occurrences of the preliminary overcurrent during the reference frame RF is greater than the reference peak number RP, the overcurrent protection circuit 130 can determine that an overcurrent has been generated, and can determine that the occurrence of the preliminary overcurrent for a number of frame counts less than the reference peak number RP is attributable to noise or insignificant artifacts that do not result in an actual overcurrent condition. For example, if the preliminary overcurrent occurs five times during a reference frame RF of 10 seconds, the overcurrent protection circuit 130 can determine that an overcurrent has occurred, and if the preliminary overcurrent occurs less than five times, the overcurrent protection circuit 130 can determine that an overcurrent has not occurred.

[0075] On the other hand, the load calculator 110 receives the image data signal DAT and calculates a frame load according to the image data signal DAT when a frame interruption occurs ( S21 ). The load calculator 110 may output the calculated frame load to the screen energy saver 120 .

[0076] The screen energy saver 120 compares the frame load of the previous frame (eg, the immediately previous frame or any previous frame within a specific frame count) with the frame load of the current frame to calculate a load deviation dL (S22). Figure 1 As discussed, the load calculator 110 may replace the screen energy saver 120 to calculate the load deviation dL.

[0077] The load calculator 110 or the screen energy saver 120 determines whether the load deviation dL is greater than the reference deviation RD (S23). The reference deviation RD is a reference for determining whether the image displayed on the display panel 600 is a still image. If the load deviation dL is greater than the reference deviation RD, the image displayed on the display panel 600 is determined to be a dynamic image (e.g., a moving picture) rather than a still image. If the load deviation dL is less than or equal to the reference deviation RD, the image displayed on the display panel 600 is determined to be a still image.

[0078] If the load deviation dL is greater than the reference deviation RD, the screen energy saver 120 resets the scale factor SF to 1 and resets the save count SC to 0 (S24). The save count SC indicates the number of frames in which the still image is displayed. Resetting the scale factor SF to 1 means maintaining the normal mode or switching the screen energy saving mode to the normal mode.

[0079] If the load deviation dL is not greater than the reference deviation RD, the screen energy saver 120 increases the save count SC by 1 ( S25 ).

[0080] The screen saver 120 determines whether the save count SC is greater than the reference time RT (S26). The reference time RT is a reference time for turning on the screen save mode (or a frame count corresponding to turning on the screen save mode). For example, the reference time RT can be set from 1 minute (or a frame count corresponding to 1 minute) to 10 minutes (or a frame count corresponding to 10 minutes), and can be changed in various ways by the user. If the still image display exceeds the reference time RT, the display mode of the image is switched from the normal mode to the screen save mode.

[0081] If the save count SC is greater than the reference time RT, the screen energy saver 120 reduces the scale factor SF to switch the display mode to the screen energy saving mode (S27). The screen energy saver 120 may sequentially reduce the scale factor SF by subtracting a constant value from the scale factor SF for each frame. Alternatively, the screen energy saver 120 may sequentially reduce the scale factor SF by multiplying the scale factor SF by a constant reduction ratio for each frame. For example, the screen energy saver 120 may sequentially reduce the scale factor SF on a frame-by-frame basis by subtracting 0.001 from the scale factor SF for each frame. Alternatively, the screen energy saver 120 may sequentially reduce the scale factor SF on a frame-by-frame basis by multiplying the scale factor SF by 0.999 for each frame. The screen energy saver 120 may reduce the scale factor SF until the scale factor SF reaches a minimum scale factor value. The minimum scale factor value may be a predetermined value. For example, the minimum scale factor value may be set to 0.5. The screen energy saver 120 transmits the reduced scale factor SF to the overcurrent protection circuit 130.

[0082] The predetermined current value RC may have a preset original value. The overcurrent protection circuit 130 reduces the predetermined current value RC from the original value or the current value of the predetermined current value RC by reflecting the scale factor SF to calculate the predetermined current value RC (S28). The screen energy saver 120 may also transmit the reduced scale factor SF to the signal controller 100, so that the brightness of the image is reduced according to the screen energy saving mode.

[0083] Therefore, by the reduced scale factor SF in the screen power saving mode, the brightness of the image is reduced and the predetermined current value RC of the overcurrent protection circuit 130 is reduced. In the screen power saving mode, the overcurrent protection circuit 130 can operate adaptively with respect to the driving current DC reduced by reducing the predetermined current value RC by applying the reduced scale factor SF. Figure 2 Steps S13, S16, S18, S23, and S26 are described as comparing one value to be "greater than" another value, but it should be understood that the comparison to be "equal to or greater than" may be performed based on the definition of the values being compared and / or the timing of the comparison regarding the increments or changes in the values without departing from the scope of the present disclosure.

[0084] In the following, reference is made to Figure 3 and Figure 4 An exemplary embodiment of a process A of shutting down the power supply 400 when an overcurrent occurs will be described.

[0085] Reference Figure 3 If it is determined that an overcurrent has occurred, the overcurrent protection circuit 130 applies an enable signal EN having a cutoff voltage to the power supply 400 (ie, outputs an enable signal EN having a cutoff voltage) regardless of the display mode of the display device (S41).

[0086] The power supply 400 is turned off due to the enable signal EN having the cut-off voltage, and the display device is powered off ( S42 ).

[0087] That is, if it is determined that an overcurrent has occurred, the display device may be powered off regardless of whether the display mode of the display device is the normal mode or the screen power saving mode.

[0088] Reference Figure 4 Another exemplary embodiment of process A of shutting down the power supply 400 when an overcurrent occurs will be described.

[0089] Reference Figure 4 If it is determined that an overcurrent has occurred, the overcurrent protection circuit 130 determines whether the scale factor SF is less than 1 (S31). That is, the overcurrent protection circuit 130 determines whether the display device is displaying an image in the screen saving mode. If the scale factor SF is less than 1, the image is displayed in the screen saving mode.

[0090] If the scale factor SF is not less than 1, the display device displays an image in the normal mode. In this case, the overcurrent protection circuit 130 applies the enable signal EN having a cutoff voltage to the power supply 400 (S41), the power supply 400 is turned off due to the enable signal EN having the cutoff voltage, and the display device is powered off (S42).

[0091] If the scale factor SF is less than 1, the display device displays an image in the screen saving mode, and the overcurrent protection circuit 130 transmits a return signal RS to the screen energy saver 120. The screen energy saver 120 sets the scale factor SF to 1 based on the return signal RS (S32). The screen energy saver 120 switches from the screen saving mode to the normal mode by transmitting the scale factor SF of 1 to the signal controller 100 and the overcurrent protection circuit 130.

[0092] In the process of switching to the normal mode, the overcurrent protection circuit 130 increases the predetermined current value RC to its original value ( S33 ).

[0093] The signal controller 100 outputs the image data signal DAT in the normal mode.

[0094] The current sensor 140 measures the driving current DC in the normal mode ( S34 ).

[0095] The overcurrent protection circuit 130 determines whether the drive current DC is greater than the predetermined current value RC (S35). That is, after switching to the normal mode, the overcurrent protection circuit 130 again compares the drive current DC with the predetermined current value RC. When the drive current DC in the normal mode is not greater than the predetermined current value RC, the overcurrent protection circuit 130 can determine that no overcurrent has occurred.

[0096] In the normal mode, if the driving current DC is greater than the predetermined current value RC, the overcurrent protection circuit 130 applies the enable signal EN having a cut-off voltage to the power supply 400 (S41), the power supply 400 is turned off due to the enable signal EN having the cut-off voltage, and the display device is powered off (S42).

[0097] As described above, when the display device displays an image in the screen saving mode, the overcurrent protection circuit 130 again determines whether an overcurrent has occurred after switching to the normal mode and may shut down the power supply 400 of the display device according to the comparison result.

[0098] Next, refer to Figure 5 To describe the reference Figures 2 to 4 The operation timings of the screen energy saver 120 and the overcurrent protection circuit 130 are described.

[0099] Reference Figure 5The signal controller 100 outputs the image data signal DAT for each frame. The screen energy saver 120 and the overcurrent protection circuit 130 can be used to output the image data signal DAT from the frame interruption of one frame to the start of the output of the image data signal DAT of the next frame. Figure 2 and Figure 3 Operation or Figure 2 and Figure 4 The operation is performed once.

[0100] For example, in the Nth frame, a frame interruption occurs when the output of the image data signal DAT is completed (S10). Figure 5 In FIG, the output of the image data signal DAT is indicated as a high level, and a low level indicates that the image data signal DAT is not output.

[0101] Following the frame interruption, a process of calculating a frame load may be performed during a first period t1 ( S21 ).

[0102] The frame load is calculated based on the image data signal DAT, and the calculated frame load can be output. Figure 5 , the output of the frame load is indicated to have a high level.

[0103] The calculation process of the screen energy saver 120 may be performed during the second period t2 after the frame load is output. That is, during the second period t2, a plurality of processes including a process (S22) in which the screen energy saver 120 calculates the load deviation dL and a process (S26) in which it determines whether the save count SC is greater than the reference time RT may be performed.

[0104] To determine switching the display mode to the screen saving mode after performing the calculation process of the screen saver 120 , a process ( S27 ) in which the screen saver 120 reduces the scale factor SF and transmits the scale factor SF to the overcurrent protection circuit 130 may be performed during the third period t3 .

[0105] The calculation process of the overcurrent protection circuit 130 and the output process of the enable signal EN may be performed during a fourth period t4 after the third period t3 and before the image data signal DAT of the N+1th frame is output. That is, during the fourth period t4, the process (S28) in which the overcurrent protection circuit 130 reduces the predetermined current value RC and the process (S41) in which the enable signal EN having a cut-off voltage is output may be performed.

[0106] Next, refer to Figure 6 To describe by repeated reference Figures 2 to 4 The operation of the display device in the screen saving mode is performed by describing the operations of the screen saver 120 and the overcurrent protection circuit 130 .

[0107] Reference Figure 6The reference frame RF of the period in which the overcurrent protection circuit 130 detects overcurrent may include a plurality of frames. The overcurrent protection circuit 130 may determine the occurrence of overcurrent by counting a peak count PC in which the driving current DC exceeds a predetermined current value RC for each frame.

[0108] In order for the screen energy saver 120 to activate the screen energy saving mode, the reference time RT may be greater than the reference frame RF. The reference time RT may include multiple reference frames RF. For example, the reference frame RF may be 600 frames or 10 seconds, while the reference time RT may be 3600 frames or 1 minute. However, it should be understood that the reference frame RF and the reference time RT are not limited and can be changed in various ways by the user.

[0109] The screen saving mode includes a first screen saving period SS1 and a second screen saving period SS2. The first screen saving period SS1 is a period in which the scale factor SF is sequentially reduced for each frame. The second screen saving period SS2 is a period in which the scale factor SF is maintained at a minimum scale factor value.

[0110] When a still image is displayed while exceeding a reference time RT, the image is displayed in screen power saving mode, and a first screen power saving period SS1 begins. As the first screen power saving period SS1 begins, the scale factor SF may be sequentially decreased from 1. The predetermined current value RC and the drive current DC may be decreased in response to the decreasing scale factor SF. If the scale factor SF reaches a minimum scale factor value, a second screen power saving period SS2 begins.

[0111] If the load deviation dL is greater than the reference deviation RD during the first screen power saving period SS1 or the second screen power saving period SS2, the proportional factor SF is reset to 1, and the display mode of the display device is switched to the normal mode. Alternatively, if it is determined that an overcurrent has occurred during one of the first screen power saving period SS1 and the second screen power saving period SS2, the proportional factor SF is reset to 1, and the display mode of the display device is switched to the normal mode.

[0112] When the display mode of the display device is switched to the normal mode, a scale factor SF of 1 is applied to the image data signal DAT. Since the image data signal DAT is output in the normal mode, the driving current DC can be increased. The overcurrent protection circuit 130 increases the predetermined current value RC to its original value.

[0113] Next, refer to Figure 7 An exemplary embodiment of a pixel PX that may be included in a display device will be described.

[0114] Figure 7 is a circuit diagram of a pixel according to an exemplary embodiment of the present disclosure. Figure 1An example among the plurality of pixels PX in the display panel 600 is described, where the pixel PX disposed in the n-th pixel row and the m-th pixel column (n and m are integers greater than 1).

[0115] Reference Figure 7 , the pixel PX includes an organic light emitting diode (OLED) and a pixel circuit 10 .

[0116] The pixel circuit 10 is configured to control current flowing through an organic light emitting diode (OLED). The pixel circuit 10 may include a driving transistor TR1, a switching transistor TR2, a sensing transistor TR3, a light emitting transistor TR4, and a storage capacitor Cst.

[0117] The driving transistor TR1 includes a gate electrode connected to a first node N1, a first electrode to which a first power supply voltage ELVDD is applied via the light emitting transistor TR4, and a second electrode connected to a second node N2. The driving transistor TR1 is connected between the first power supply voltage ELVDD and the organic light emitting diode (OLED), and controls the amount of current flowing from the first power supply voltage ELVDD through the organic light emitting diode (OLED) in accordance with the voltage at the first node N1.

[0118] The switching transistor TR2 includes a gate electrode connected to the scan line SCLn, a first electrode connected to the data line DLm, and a second electrode connected to the first node N1. The switching transistor TR2 is connected between the data line DLm and the driving transistor TR1. The switching transistor TR2 is turned on by a scan signal having a gate-on voltage applied to the scan line SCLn and transmits a data voltage Vdat applied to the data line DLm to the first node N1.

[0119] The sensing transistor TR3 includes a gate electrode connected to a sensing line SSLn, a first electrode connected to a second node N2, and a second electrode connected to a receiving line RLm. The sensing transistor TR3 is connected between the second electrode of the driving transistor TR1 and the receiving line RLm. The sensing transistor TR3 is turned on by a sensing signal having a gate-on voltage applied to the sensing line SSLn, and transmits the current flowing through the driving transistor TR1 to the organic light-emitting diode (OLED) to the receiving line RLm. The receiving line RLm can be used as a signal line for transmitting an initialization voltage to the second node N2. The initialization voltage transmitted to the second node N2 via the receiving line RLm can initialize the anode voltage of the organic light-emitting diode (OLED).

[0120] The light emitting transistor TR4 includes a gate electrode connected to the light emitting line EMLn, a first electrode to which the first power supply voltage ELVDD is applied, and a second electrode connected to the first electrode of the driving transistor TR1. The light emitting transistor TR4 is turned on by a light emitting signal having a gate-on voltage applied to the light emitting line EMLn and transmits the first power supply voltage ELVDD to the driving transistor TR1.

[0121] The driving transistor TR1, the switching transistor TR2, and the sensing transistor TR3 may be n-channel field-effect transistors, and the light-emitting transistor TR4 may be a p-channel field-effect transistor. An n-channel field-effect transistor can be turned on by a high-level gate-on voltage and turned off by a low-level gate-off voltage. A p-channel field-effect transistor can be turned on by a low-level gate-on voltage and turned off by a high-level gate-off voltage. According to an exemplary embodiment, at least one of the driving transistor TR1, the switching transistor TR2, and the sensing transistor TR3 may be a p-channel field-effect transistor, and the light-emitting transistor TR4 may be an n-channel field-effect transistor.

[0122] The storage capacitor Cst includes a first electrode connected to the first node N1 and a second electrode connected to the second node N2. In response to a scan signal having a gate-on voltage applied to the scan line SCLn, the data voltage Vdat is transmitted to the first node N1, and the storage capacitor Cst functions to maintain the voltage at the first node N1.

[0123] The organic light emitting diode (OLED) includes an anode connected to a second node N2 and a cathode connected to a second power supply voltage ELVSS. The organic light emitting diode (OLED) can emit light having a brightness corresponding to the current supplied from the pixel circuit 10. The organic light emitting diode (OLED) can emit light of one of the primary colors and white. Examples of the primary colors are the three primary colors of red, green, and blue. Other examples of the primary colors include yellow, cyan, and magenta.

[0124] Next, refer to Figure 8 A method for driving a display device is described. Figure 8 The driving method of the display device described can be applied to Figures 2 to 6 The driving method described or reference Figures 2 to 6 The described driving method is combined.

[0125] Figure 8 is a method for driving a Figure 1 Flowchart of the display device.

[0126] Reference Figure 8, the display device monitors the driving current DC flowing to the display panel 600 through the current sensor 140 ( S110 ).

[0127] The display device operates in the screen saving mode by reducing the scale factor SF from a first value (eg, SF=1) and lowers the brightness of the still image based on a duration of the still image exceeding a reference time RT ( S120 ).

[0128] The display device calculates a frame load based on the sum of data values for a plurality of pixels PX according to the image data signal DAT. The display device can calculate a load deviation dL by comparing the frame load of the previous frame with the frame load of the current frame. If the load deviation dL is less than or equal to the reference deviation RD for a period longer than the reference time RT, the display device can operate in a screen power saving mode.

[0129] The display device determines whether the load deviation dL is greater than the reference deviation RD. When the load deviation dL is greater than the reference deviation RD, the display device may reset the scale factor SF to a first value (eg, 1) and reset the save count SC to 0.

[0130] When the load deviation dL is not greater than the reference deviation RD, the display device may increment the storage count SC by 1. When the storage count SC is greater than the reference time RT, the display device may reduce the scale factor SF by a predetermined value. The display device may sequentially reduce the scale factor SF by subtracting a predetermined value from the scale factor SF. Alternatively, the display device may sequentially reduce the scale factor SF by multiplying the scale factor SF by a reduction ratio. The display device may reduce the scale factor SF until the scale factor SF reaches a predetermined minimum scale factor value.

[0131] The display device reduces the predetermined current value RC according to the scale factor SF, and compares the driving current DC with the predetermined current value RC to determine the possibility of occurrence of overcurrent (S130).

[0132] If the driving current DC is greater than the predetermined current value RC in the screen power saving mode, the peak count PC is incremented, and if the peak count PC is greater than the reference peak count RP in the screen power saving mode (ie, when overcurrent is detected), the display device can be powered off.

[0133] Alternatively, if an overcurrent event is detected in the screen power saving mode, the display device may switch to the normal mode by changing the scale factor SF to the first value and setting the predetermined current value RC to the original value. The display device measures the driving current DC flowing to the display panel 600 in the normal mode (S140).

[0134] If the display device compares the driving current DC with the predetermined current value RC in the normal mode and detects an overcurrent event, the display device is powered off ( S150 ).

[0135] The above detailed description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of the exemplary embodiments of the present disclosure as defined by the claims and their equivalents. The present disclosure provides various specific details to assist in understanding, but these details are to be considered as exemplary only. Therefore, it will be appreciated by those skilled in the art that various changes and modifications of the embodiments described herein may be made without departing from the scope and spirit of the present disclosure. Therefore, the scope of the present disclosure should be determined in accordance with the present disclosure to include the entirety of the appended claims and their equivalents.

Claims

1. A display device, comprising: a load calculator that calculates a frame load based on a sum of data values for a plurality of pixels of the display panel and calculates a load deviation by comparing the frame load of a previous image frame with the frame load of a current image frame, wherein when the load deviation is less than or equal to a reference deviation, the image is displayed as a still image; a screen energy saver for causing the image to be displayed with reduced brightness in a screen power saving mode by reducing a scale factor from a first value based on a time period during which the image is displayed as the still image being longer than a reference time; and An overcurrent protection circuit detects an overcurrent and cuts off power to the display device based on a predetermined current value reduced according to the scale factor and a comparison between the predetermined current value and a driving current supplied to the display panel in which the image is displayed.

2. The display device according to claim 1, further comprising: a power supply to supply the driving current to the display panel, and The overcurrent protection circuit provides an enable signal having a cutoff voltage to the power supply to shut down the power supply based on the duration that the driving current is greater than the predetermined current value being longer than the reference time.

3. The display device according to claim 1, wherein: The overcurrent protection circuit transmits a return signal to the screen energy saver based on detection of overcurrent in the screen energy save mode, and The screen saver changes the scale factor to the first value according to the return signal and displays the image in a normal mode.

4. The display device according to claim 3, wherein: The overcurrent protection circuit sets the predetermined current value to an original value in the normal mode, and compares the driving current with the predetermined current value in the normal mode to determine to power off the display device.

5. The display device according to claim 1, wherein: The image is displayed in the screen power saving mode based on a duration of the load deviation being less than or equal to the reference deviation being longer than the reference time.

6. The display device according to claim 1, wherein: The screen energy saver subtracts a constant value from the scale factor for each image frame to sequentially decrease the scale factor.

7. The display device according to claim 1, wherein: The screen energy saver sequentially reduces the scale factor by multiplying the scale factor by a reduction ratio for each image frame.

8. The display device according to claim 1, wherein: The screen energy saver decreases the scale factor until the scale factor has a minimum scale factor value.

9. A method for driving a display device, the method comprising: monitoring a driving current supplied to a display panel displaying an image; calculating a frame load based on a sum of data values for a plurality of pixels of the display panel; calculating a load deviation by comparing the frame load of the previous image frame with the frame load of the current image frame; determining the image as a still image based on comparing the load deviation with a reference deviation; displaying the image with reduced brightness in a screen power saving mode by decreasing a scale factor from a first value based on a time period during which the image is displayed as the still image being longer than a reference time; reducing the predetermined current value according to the proportional factor; comparing the predetermined current value with the driving current to detect occurrence of an overcurrent; In response to detecting the occurrence of the overcurrent in the screen power saving mode, changing the scale factor to the first value and changing the predetermined current value to an original value to display the image in a normal mode; as well as The display device is powered off based on detection of the overcurrent in the normal mode, wherein the overcurrent is detected based on a comparison between the driving current supplied to the display panel and the predetermined current value.

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