Display device and driving method thereof

Abstract

The present invention discloses a display device and a driving method thereof. The display device comprises: a display panel comprising a plurality of pixels; a data driver configured to supply a black voltage to the display panel; and a controller configured to: set an initial driving power supply voltage of the display panel; determine a bright spot voltage of the display panel while the data driver is supplying the black voltage to the display panel; and set any one of the bright spot voltage and the initial driving power supply voltage as a final driving power supply voltage.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2018-0138289 filed in the Korean Intellectual Property Office on November 12, 2018, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to a display device and a driving method thereof. Background Art

[0004] The driving power supply voltage of a general display panel can be determined based on the brightness and chromaticity of the display panel. Therefore, when the brightness required in the display panel increases and high reliability is required, the low potential driving power supply voltage can be reduced.

[0005] However, when the low-potential driving power supply voltage is reduced, a bright spot may appear in which the brightness corresponding to the black grayscale increases due to leakage current. As a result, the image quality may be deteriorated.

[0006] The Background section of the specification includes information intended to provide context for exemplary embodiments and the information in this Background section does not necessarily constitute prior art. Summary of the invention

[0007] Some exemplary embodiments may include a display device that determines a driving power supply voltage of a display panel by considering a bright spot, and a driving method of the display device.

[0008] Some exemplary embodiments may also include a display device and a driving method of the display device, wherein the display device determines a bright spot voltage based on a result obtained by measuring a pixel current for each driving power supply voltage or a black voltage, and determines a driving power supply voltage of a display panel based on the determined bright spot voltage.

[0009] According to some exemplary embodiments of the present disclosure, a display device includes: a display panel including a plurality of pixels; a data driver configured to supply a black voltage to the display panel; and a controller configured to: set an initial driving power supply voltage of the display panel; determine a bright spot voltage of the display panel while the data driver is supplying the black voltage to the display panel; and set any one of the bright spot voltage and the initial driving power supply voltage as a final driving power supply voltage.

[0010] The controller may change the driving power voltage by a preset unit within a threshold range while the data driver is supplying the black voltage to the display panel, and measure the current of the display panel corresponding to each of the changed driving power voltages.

[0011] The threshold range may include an initial drive supply voltage.

[0012] The initial driving power supply voltage may be determined by the brightness and chromaticity of the display panel.

[0013] The controller may change the black voltage by a preset unit within a threshold range while the data driver is supplying the black voltage to the display panel, and measure the current of the display panel corresponding to each of the changed black voltages.

[0014] The controller may determine a reference current according to the driving power supply voltage, and determine the driving power supply voltage as the bright spot voltage when a difference between the reference current and the measured current exceeds a preset threshold by comparing the reference current with the measured current.

[0015] When the measured current is approximated as an arbitrary quadratic equation, the reference current can be defined by the tangent line of the quadratic equation at the initial driving power supply voltage.

[0016] The controller may set a larger voltage between an initial driving power supply voltage and a bright spot voltage as a final driving power supply voltage.

[0017] The driving power supply voltage may be a low potential voltage.

[0018] According to some exemplary embodiments of the present disclosure, in a method for driving a display device having a display panel including a plurality of pixels, the method includes: setting an initial driving power supply voltage of the display panel; determining a bright spot voltage by supplying a black voltage and a driving power supply voltage to the display panel; and setting any one of the bright spot voltage and the initial driving power supply voltage as a final driving power supply voltage.

[0019] The determination of the bright point voltage may include: changing the driving power voltage by a preset unit within a threshold range while the black voltage is supplied to the display panel; and measuring the current of the display panel corresponding to each of the changed driving power voltages.

[0020] The threshold range may include an initial drive supply voltage.

[0021] The initial driving power supply voltage may be determined based on the brightness and chromaticity of the display panel.

[0022] The determination of the bright point voltage may include: changing the black voltage by a preset unit within a threshold range while the black voltage is supplied to the display panel; and measuring a current of the display panel corresponding to each of the changed black voltages.

[0023] Determining the bright spot voltage may include: determining a reference current based on a driving power supply voltage; comparing the reference current and the measured current; and based on the comparison result, determining the driving power supply voltage when the difference between the reference current and the measured current exceeds a preset threshold as the bright spot voltage.

[0024] Determining the reference current may include: approximating the measured current to an arbitrary quadratic equation; and defining the reference current according to a tangent line of the quadratic equation at the initial driving power supply voltage.

[0025] Setting the final driving power supply voltage may include: comparing the initial driving power supply voltage and the bright spot voltage; when the initial driving power supply voltage is greater than the bright spot voltage, setting the initial driving power supply voltage to the final driving power supply voltage; and when the bright spot voltage is greater than the initial driving power supply voltage, setting the bright spot voltage to the final driving power supply voltage.

[0026] The driving power supply voltage may be a low potential voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Various aspects of some exemplary embodiments will now be described more fully below with reference to the accompanying drawings; however, these exemplary embodiments may be embodied in different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure is more thorough and more complete, and the scope of the exemplary embodiments is more fully conveyed to those skilled in the art.

[0028] In the accompanying drawings, dimensions may be exaggerated for clarity of illustration. It should be understood that when an element is referred to as being "between" two elements, it may be the only element between the two elements, or one or more intermediate elements may also be present. The same reference numerals refer to the same elements throughout the text.

[0029] Figure 1 is a block diagram illustrating a display device according to some exemplary embodiments of the present disclosure.

[0030] Figure 2 It is shown Figure 1 An embodiment of a pixel is shown in FIG.

[0031] Figure 3 is a flowchart illustrating a driving method of a display device according to some exemplary embodiments of the present disclosure.

[0032] Figure 4 is a flow chart illustrating a method for determining a driving power supply voltage according to some exemplary embodiments of the present disclosure.

[0033] Figure 5is a flow chart illustrating a method for determining a driving power supply voltage according to some exemplary embodiments of the present disclosure.

[0034] Figures 6 to 8 is a diagram illustrating a method for determining a driving power supply voltage according to some exemplary embodiments of the present disclosure. DETAILED DESCRIPTION

[0035] With reference to the embodiments described below in conjunction with the accompanying drawings, the characteristics and features of some exemplary embodiments of the present invention and the modes for realizing them will become more apparent. However, the present disclosure is not limited to the exemplary embodiments, but can be implemented in different forms. These exemplary embodiments are provided only for the purpose of illustration, and are used to enable those skilled in the art to more fully understand the scope of some exemplary embodiments of the present disclosure.

[0036] Throughout the specification, when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element, or may be indirectly connected or coupled to the other element with one or more intermediate elements interposed therebetween. It should be noted that when reference numerals are given to elements of each drawing, the same reference numerals refer to the same elements even if the same elements are shown in different drawings.

[0037] Figure 1 is a block diagram illustrating a display device according to some exemplary embodiments of the present disclosure.

[0038] refer to Figure 1 According to some exemplary embodiments of the present disclosure, a display device may include a display panel 100 including a plurality of pixels PX, a scan driver 210, a data driver 220, an emission driver 230, a power supply 240, and a controller (eg, a timing controller) 250.

[0039] The controller 250 may generate a scan drive control signal, a data drive control signal, an emission drive control signal, and a power drive control signal based on a signal input from the outside. The scan drive control signal generated by the controller 250 may be supplied to the scan driver 210, the data drive control signal generated by the controller 250 may be supplied to the data driver 220, the emission drive control signal generated by the controller 250 may be supplied to the emission driver 230, and the power drive control signal generated by the controller 250 may be supplied to the power supply 240.

[0040] The scan drive control signal may include a plurality of clock signals and a scan start signal. The scan start signal may control the output timing of the first scan signal. The clock signal may be used to shift the scan start signal.

[0041] The data driving control signal may include a source start pulse and a clock signal. The source start pulse may control the sampling start time of the data, and the clock signal may be used to control the sampling operation.

[0042] The emission drive control signal may include an emission start pulse and a clock signal. The emission start pulse may control the first timing of the emission control signal. The clock signal may be used to shift the emission start pulse.

[0043] The power driving control signal may include a first driving power VDD and a second driving power VSS (see Figure 2 In various embodiments of the present disclosure, the controller 250 may determine the bright spot voltage by measuring the current change of the display panel 100 according to the second driving power VSS or the black voltage during the period when the display panel 100 is displaying the black grayscale. The controller 250 may determine the optimal second driving power VSS according to the bright spot voltage, and provide the power supply 240 with information related to the second driving power VSS determined by the power drive control signal.

[0044] Meanwhile, although an embodiment in which the controller 250 fixes the first driving power VDD and controls the second driving power VSS is described in the present disclosure, embodiments of the present disclosure are not limited thereto.

[0045] The scan driver 210 may output a scan signal corresponding to the scan drive control signal. The scan driver 210 may sequentially supply the scan signal to the scan lines SC1 to SCn. The scan signal may be set to a gate-on voltage (eg, a high level voltage), at which a transistor included in the pixel PX may be turned on.

[0046] The data driver 220 may supply data signals to the data lines D1 to Dm corresponding to the data driving control signal. The data signals supplied to the data lines D1 to Dm may be supplied to the pixels PX to which the scan signals are supplied. To this end, the data driver 220 may supply data signals to the data lines D1 to Dm in synchronization with the scan signals.

[0047] The emission driver 230 may supply an emission control signal to the emission control lines E1 to En corresponding to the emission drive control signal. The emission control signal may be used to control the emission time of the pixel PX. For example, a specific pixel PX supplied with the emission control signal may be set to an emission state during a period in which the emission control signal is supplied, and may be set to a non-emission state during the remaining period.

[0048] The power supply 240 may supply driving power to each of the pixels PX included in the display panel 100 based on the power driving control signal. The power supply 240 may supply a first driving power VDD through a first power line VDDL, and may supply a second driving power VSS through a second power line VSSL. The first driving power VDD may be set to a high potential voltage, and the second driving power VSS may be set to a low potential voltage.

[0049] The display panel 100 may include a plurality of pixels PX coupled to the data lines D1 to Dm, the scan lines SC1 to SCn, and the emission control lines E1 to En. The pixels PX may be supplied with a first driving power VDD and a second driving power VSS from the power supply 240.

[0050] Each of the pixels PX may be supplied with a data signal from a corresponding data line among the data lines D1 to Dm when a scan signal is supplied to a corresponding scan line coupled to the pixel among the scan lines SC1 to SCn. The pixel PX supplied with the data signal may control the amount of current flowing from the first driving power source VDD to the second driving power source VSS via the light emitting device (not shown) in response to the data signal.

[0051] The light emitting device may generate light having a predetermined brightness corresponding to the amount of current. In addition, the first driving power source VDD may be set to a voltage higher than that of the second driving power source VSS.

[0052] Figure 2 It is shown Figure 1 FIG. 1 is a diagram of an exemplary embodiment of a pixel shown in FIG. Figure 2 Pixels PX coupled to the i-th scan line SCi, the (i-1)-th scan line SCi-1, the (i+1)-th scan line SCi+1, and the j-th data line Dj are shown in FIG.

[0053] The pixel PX may include a light emitting device OLED, first to seventh transistors T1 to T7 , and a storage capacitor Cst.

[0054] One end of the light emitting device OLED is coupled to the first transistor T1 via the sixth transistor T6, and the other end of the light emitting device OLED is coupled to the second driving power source VSS. The light emitting device OLED generates light having brightness (eg, predetermined brightness) corresponding to the amount of current supplied from the first transistor T1.

[0055] The source electrode of the first transistor (driving transistor) T1 is coupled to the first driving power source VDD via the fifth transistor T5, and the drain electrode of the first transistor T1 is coupled to one end of the light emitting device OLED via the sixth transistor T6. The first transistor T1 controls the amount of current flowing from the first driving power source VDD to the second driving power source VSS via the light emitting device OLED corresponding to the voltage of the first node N1 as its gate electrode.

[0056] The second transistor T2 is coupled between the jth data line Dj and the source electrode of the first transistor T1.

[0057] The gate electrode of the second transistor T2 is coupled to the i-th scan line SCi. When a scan signal is supplied to the i-th scan line SCi, the second transistor T2 is turned on to electrically couple the j-th data line Dj and the source electrode of the first transistor T1 to each other.

[0058] The third transistor T3 is coupled between the drain electrode of the first transistor T1 and the first node N1. In addition, the gate electrode of the third transistor T3 is coupled to the i-th scan line SCi. When the scan signal is supplied to the i-th scan line SCi, the third transistor T3 is turned on to electrically couple the drain electrode of the first transistor T1 and the first node N1 to each other. Therefore, when the third transistor T3 is turned on, the first transistor T1 is diode-coupled.

[0059] The fourth transistor T4 is coupled between the first node N1 and the initialization power supply Vint. In addition, the gate electrode of the fourth transistor T4 is coupled to the (i-1)th scan line SCi-1. When the scan signal is supplied to the (i-1)th scan line SCi-1, the fourth transistor T4 is turned on to supply the voltage of the initialization power supply Vint to the first node N1. The initialization power supply Vint is set to a voltage lower than the data signal.

[0060] The fifth transistor T5 is coupled between the first driving power source VDD and the source electrode of the first transistor T1.

[0061] A gate electrode of the fifth transistor T5 is coupled to the i-th emission control line Ei. When the emission control signal is supplied to the i-th emission control line Ei, the fifth transistor T5 is turned off, otherwise it is turned on.

[0062] The sixth transistor T6 is coupled between the drain electrode of the first transistor T1 and one end of the light emitting device OLED. In addition, the gate electrode of the sixth transistor T6 is coupled to the i-th emission control line Ei. When the emission control signal is supplied to the i-th emission control line Ei, the sixth transistor T6 is turned off, otherwise it is turned on.

[0063] The seventh transistor T7 is coupled between the initialization power supply Vint and one end of the light emitting device OLED. In addition, the gate electrode of the seventh transistor T7 is coupled to the (i+1)th scan line SCi+1. When the scan signal is supplied to the (i+1)th scan line SCi+1, the seventh transistor T7 is turned on to supply the voltage of the initialization power supply Vint to one end of the light emitting device OLED.

[0064] The storage capacitor Cst is coupled between the first driving power source VDD and the first node N1. The storage capacitor Cst stores a voltage corresponding to the data signal and a threshold voltage of the first transistor T1.

[0065] Figure 3 is a flowchart illustrating a driving method of a display device according to some exemplary embodiments of the present disclosure.

[0066] refer to Figure 1 and Figure 3 According to some exemplary embodiments of the present disclosure, the display device sets an initial driving power voltage of the display panel 100 (310). The initial driving power voltage may include a voltage of a first driving power VDD (hereinafter referred to as a first driving power voltage) and a voltage of a second driving power VSS (hereinafter referred to as a second driving power voltage).

[0067] The initial driving power supply voltage may be set based on the brightness and chromaticity of the display panel 100. The brightness and chromaticity of the display panel 100 may be determined by the type, specification, size of the display panel 100, etc. of the display device. The initial driving power supply voltage may be set by the manufacturer of the display device, etc.

[0068] Next, the display device performs multiple programming (MTP) (320). For example, the display device may program the reference gamma voltage in real time so that the brightness and chromaticity of the display panel 100 are suitable for a value (e.g., a desired value). The reference gamma voltage is a voltage input to the data driver 220, which generates a data signal for determining display brightness. The data driver 220 uses the reference gamma voltage to generate a data signal corresponding to the grayscale of the input image data, and provides the generated data signal to the display panel 100. The light-emitting device OLED provided in each pixel PX of the display panel 100 emits light corresponding to the data signal. The display device programs the reference gamma voltage so that the display panel 100 can have a target brightness and a target chromaticity.

[0069] Next, the display device may set a gamma voltage (e.g., black voltage) corresponding to the black grayscale (330). For example, the display device may set a gamma voltage corresponding to the black grayscale with respect to each pixel PX. The display device may not only set a gamma voltage corresponding to the black grayscale, but may also set a corresponding gamma voltage with respect to a preset grayscale that can be represented by the pixel PX.

[0070] Next, the display device may set a driving power voltage based on the bright spot voltage of the display panel 100 ( 340 ).

[0071] In some exemplary embodiments of the present disclosure, the controller 250 may provide a black voltage to the display panel 100 through the data driver 220, and may measure a current flowing through the display panel 100 while changing the second driving power supply voltage. The current is a current flowing through the light emitting device OLED provided in each pixel PX of the display panel 100, and may be a current of the second driving power supply VSS. The black voltage is a preset gamma voltage corresponding to a black grayscale.

[0072] The controller 250 uses the current measurement result to determine the bright spot voltage of the display panel 100. The controller 250 may reset the bright spot voltage to the second driving power voltage or set the preset initial second power voltage to the final second driving power voltage based on a result obtained by comparing the determined bright spot voltage with the preset initial second power voltage.

[0073] Hereinafter, the above-mentioned method for setting the driving power supply voltage of the display device will be described in more detail.

[0074] Figure 4 is a flow chart illustrating a method for determining a driving power supply voltage according to some exemplary embodiments of the present disclosure in more detail. Figure 5 is a flowchart illustrating in detail a method for determining a driving power supply voltage according to some exemplary embodiments of the present disclosure. Figures 6 to 8 is a diagram illustrating a method for determining a driving power supply voltage according to some exemplary embodiments of the present disclosure.

[0075] refer to Figure 4 First, the display device displays an image with a specific grayscale (341). In an embodiment, the display device may display an image with a black grayscale on the display panel 100. The data driver 220 provides a black voltage to the display panel 100 so that the pixels PX of the display panel 100 may emit light with a brightness corresponding to the black grayscale.

[0076] Next, while the driving power supply voltage is being changed, the display device measures the current of the display panel 100 ( 342 ).

[0077] In some exemplary embodiments of the present disclosure, the controller 250 of the display device changes (increases and / or decreases) the second driving power supply voltage supplied from the power supply 240 to the display panel 100 by a preset unit within a threshold range. The threshold range for changing the second driving power supply voltage can be determined based on the initial driving power supply voltage. For example, the threshold range can be determined to include the initial second power supply voltage.

[0078] In some exemplary embodiments, when the initial second power supply voltage is set to -10V, the display device may change the second driving power supply voltage supplied to the display panel 100 from -10V to -11.1V at intervals of 0.1V.

[0079] While the second driving power supply voltage supplied to the display panel 100 is being changed, the display device measures the current of the display panel 100. The measured current is the current flowing through the light emitting device OLED provided in each pixel PX. In other words, the measured current may be the current flowing through the second driving power supply VSS. The controller 250 may measure the current of the display panel 100 with respect to each second driving power supply voltage changed by a preset unit. Figure 6 , as an example, a result obtained by measuring the current while the second driving power supply voltage is being changed from -10 V to -11.1 V at intervals of 0.1 V is shown. In the example, the relationship between the second driving power supply voltage and the measured current can be defined by an arbitrary quadratic equation or can be approximated as an arbitrary quadratic equation.

[0080] However, the embodiments of the present disclosure are not limited thereto. For example, according to some exemplary embodiments of the present disclosure, the display device may be as follows: Figure 5 As shown in , the current change is measured according to the data voltage (i.e., the black voltage corresponding to the black grayscale (e.g., 7V)) (342'). In another embodiment, the data driver 220 can change the black voltage by a preset unit within a threshold range, and supply a data signal corresponding to the changed black voltage to the display panel 100. The threshold range can be determined based on a predetermined black voltage. For example, the threshold range can be determined to include a predetermined black voltage.

[0081] Next, the display device determines a bright spot voltage of the display panel 100 based on the measured current variation ( 343 ).

[0082] The controller 250 may determine the reference current based on the second driving power supply voltage. The reference current may be determined based on the current measured at the initial second power supply voltage. In some exemplary embodiments, when the relationship between the second driving power supply voltage and the measured current is defined by an arbitrary quadratic equation, the reference current may be determined by a tangent of the corresponding quadratic equation at the initial second power supply voltage. The tangent at the initial second power supply voltage may be defined by the following equation 1.

[0083] Equation 1

[0084] I=a×(V VSS -V VSS_int )+I 0

[0085] Here, I is the reference current relative to the second driving power supply voltage, V VSS is the second driving power supply voltage, V VSS_int is the initial second power supply voltage, I 0 is the current measured at the initial second power supply voltage, and a is the differential value of the quadratic equation at the initial second power supply voltage.

[0086] exist Figure 7 As an example, it is shown Figure 6 That is, in Figure 7 , as an example, a tangent line when the second driving power supply voltage is -10 V (which is the initial second power supply voltage) is shown.

[0087] The controller 250 compares the reference current with the current measured relative to the second driving power supply voltage. Figure 8 As shown in , when the difference between the reference current and the measured current exceeds a preset threshold, the controller 250 may determine the corresponding second driving power voltage as the bright spot voltage.

[0088] In the present disclosure, the method for determining the bright spot voltage of the display device is not limited thereto.

[0089] When determining the bright spot voltage, the display device can determine whether the bright spot voltage is greater than the preset driving power voltage by comparing the bright spot voltage with the preset driving power voltage (344). That is, the controller 250 can compare the determined bright spot voltage with the preset second driving power voltage.

[0090] When the bright spot voltage is greater than the preset driving power voltage, the display device sets the bright spot voltage to the driving power voltage (345). That is, when the bright spot voltage is greater than the preset second driving power voltage, the controller 250 can set the bright spot voltage to the second driving power voltage.

[0091] On the contrary, when the bright spot voltage is less than or equal to the preset driving power voltage, the display device sets the preset driving power voltage as the final driving power voltage (346). That is, when the bright spot voltage is less than or equal to the preset second driving power voltage, the controller 250 sets the preset second driving power voltage as the final second driving power voltage.

[0092] When the display device is driven by the driving power supply voltage determined as described above, degradation of image quality due to the occurrence of bright spots of the display panel 100 may be prevented or reduced, and the yield and reliability of the display device may be improved.

[0093] In the display device and the driving method thereof according to the present disclosure, the driving power supply voltage of the display panel is determined by considering the bright spot, so that the possibility of image quality being deteriorated due to the occurrence of the bright spot can be prevented or reduced.

[0094] Furthermore, in the display device and the driving method thereof according to the present disclosure, an optimal black grayscale voltage is determined, so that the yield and reliability of the display device can be improved.

[0095] Exemplary embodiments have been disclosed herein, and although specific terms are used, they are used and interpreted in a general and descriptive sense only, and not for purposes of limitation. In some cases, as will be apparent to one of ordinary skill in the art to which this application is submitted, features, characteristics, and / or elements described in conjunction with a particular embodiment may be used alone or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless expressly indicated otherwise. Therefore, it should be understood by those skilled in the art that various changes may be made in form and detail without departing from the spirit and scope of the present disclosure as set forth in the appended claims and their equivalents.

Claims

1. A display device, comprising: A display panel including a plurality of pixels; a data driver configured to supply a black voltage to the display panel; as well as The controller is configured as: Setting an initial driving power supply voltage of the display panel; while the data driver is supplying the black voltage to the display panel, changing a driving power supply voltage by a preset unit within a threshold range, and measuring a current of the display panel corresponding to each change of the driving power supply voltage; determining a bright spot voltage of the display panel; and Setting any one of the bright spot voltage and the initial driving power supply voltage as the final driving power supply voltage, The controller is configured to determine a reference current according to the driving power supply voltage, and determine the driving power supply voltage when the difference between the reference current and the measured current exceeds a preset threshold as the bright spot voltage.

2. The display device according to claim 1, wherein: The threshold range includes the initial driving power supply voltage.

3. The display device according to claim 1, wherein: The initial driving power supply voltage is determined by the brightness and chromaticity of the display panel.

4. The display device according to claim 1, wherein: When the measured current is approximated by an arbitrary quadratic equation, the reference current is defined by a tangent line of the quadratic equation at the initial driving power supply voltage.

5. The display device according to claim 1, wherein: The controller is configured to set a larger voltage of the initial driving power supply voltage and the bright spot voltage as the final driving power supply voltage.

6. A method for driving a display device having a display panel, wherein the display panel comprises a plurality of pixels, the method comprising: Setting an initial driving power supply voltage of the display panel; while a black voltage is supplied to the display panel, changing a driving power supply voltage by a preset unit within a threshold range; measuring a current of the display panel corresponding to each change of the driving power supply voltage; Determine the bright spot voltage; as well as Setting any one of the bright spot voltage and the initial driving power supply voltage as the final driving power supply voltage, Wherein, the determination of the bright spot voltage comprises: Determine a reference current according to the driving power supply voltage; comparing the reference current to the measured current; and According to the comparison result, the driving power supply voltage when the difference between the reference current and the measured current exceeds a preset threshold is determined as the bright spot voltage.

7. The method according to claim 6, wherein: The threshold range includes the initial driving power supply voltage.

8. The method according to claim 6, wherein: The determining of the reference current comprises: approximating the measured current as an arbitrary quadratic equation; and The reference current is defined according to a tangent line of the quadratic equation at the initial driving power supply voltage.

9. The method according to claim 6, wherein: The setting of the final driving power supply voltage includes: comparing the initial driving power supply voltage with the bright spot voltage; When the initial driving power supply voltage is greater than the bright spot voltage, setting the initial driving power supply voltage to the final driving power supply voltage; and When the bright spot voltage is greater than the initial driving power supply voltage, the bright spot voltage is set as the final driving power supply voltage.

Images