Backlight driver, backlight device and operating method of backlight device

Abstract

A backlight device includes: LED elements divided into dimming groups; a panel driver configured to output a reference current for driving the LED elements; and a plurality of pixel circuits, wherein each pixel circuit is connected to the panel driver through a common line and is respectively configured to drive a first plurality of LED elements included in a corresponding dimming group. Each of the pixel circuits is configured to: obtain a reference voltage based on the reference current and store the reference voltage in a first period of a frame period; obtain brightness data of an image displayed by the corresponding dimming group in a second period of the frame period; and drive the first plurality of LED elements during a light-emission time corresponding to the brightness data obtained in the second period using the reference voltage stored in the first period in a third period of the frame period.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of Korean Patent Application No. 10-2020-0054762 filed on May 7, 2020, in the Korean Intellectual Property Office, and Korean Patent Application No. 10-2021-0004923 filed on January 13, 2021, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] Methods, devices and systems consistent with the example embodiments relate to a backlight driver, a backlight device including the backlight driver and an operating method of the backlight device, and more specifically, to a backlight driver that drives a light emitting diode (LED) element using multiple pixel circuits sharing a current source, a backlight device including the backlight driver and an operating method of the backlight device. Background Art

[0004] Display devices are widely used in smart phones, notebook computers, and monitors, and may include a display panel that displays an image. In this regard, when the display panel is a liquid crystal display (LCD) panel rather than an organic light emitting diode (OLED) panel including self-luminous elements, a backlight device for improving contrast may be provided. The backlight device may include a plurality of light emitting diode (LED) elements and may be disposed on the rear surface of the display panel.

[0005] Recently, local dimming of multiple LED elements driving each area of ​​a display panel has been widely used in backlight devices. In particular, full array local dimming (FALD) in which LED elements are arranged in a 2D array over the entire area of ​​a display panel has attracted great attention. Because FALD requires a large number of LED elements, a large number of pixel circuits for driving the LED elements are also required. However, as the number of pixel circuits increases, chip-to-chip uniformity may deteriorate, and manufacturing costs may increase due to the increase in components. Summary of the invention

[0006] Example embodiments provide a backlight driver that stores reference currents in a plurality of pixel circuits sharing one current source in a time division method and performs a local dimming operation based on the stored reference currents, a backlight device including the same, and an operating method of the backlight device.

[0007] According to one aspect of an exemplary embodiment, a backlight device includes: a plurality of light emitting diode (LED) elements divided into a plurality of dimming groups; a panel driver configured to output a reference current for driving the plurality of LED elements; and a plurality of pixel circuits, each of which is connected to the panel driver through a common line and is respectively configured to drive a first plurality of LED elements included in a corresponding dimming group among the plurality of dimming groups. Each of the plurality of pixel circuits is configured to: obtain a reference voltage based on the reference current and store the reference voltage in a first period of a frame period; obtain brightness data of an image displayed by the corresponding dimming group in a second period of the frame period; and drive the first plurality of LED elements during a light emission time corresponding to the brightness data obtained in the second period using the reference voltage stored in the first period in a third period of the frame period.

[0008] According to one aspect of an exemplary embodiment, a backlight driver is provided. The backlight driver is configured to operate in units of a frame period including a charging period and a display period, and the backlight driver includes: a first pixel circuit configured to drive a first plurality of light emitting diode (LED) elements corresponding to a first area of ​​a display panel; a second pixel circuit configured to drive a second plurality of LED elements corresponding to a second area of ​​the display panel; and a panel driver including a current source connected in parallel to the first pixel circuit and the second pixel circuit, and configured to provide a reference current to the first pixel circuit and the second pixel circuit based on the current source. The first pixel circuit is configured to: obtain a reference voltage based on the reference current and store the reference voltage in a first sampling period of the charging period, and drive the first plurality of LED elements based on first brightness data representing brightness corresponding to the first area in the display period. The second pixel circuit is configured to: obtain a reference voltage based on the reference current and store the reference voltage in a second sampling period of the charging period, and drive the second plurality of LED elements based on second brightness data representing brightness corresponding to the second area in the display period.

[0009] According to one aspect of an example embodiment, a method for driving a backlight device to provide illumination to a display panel includes: generating a reference current using a current source in a first period of a frame period; obtaining a reference voltage based on the reference current in a time-division method using N (N is a positive integer) pixel circuits that share a current source in the first period, and storing the reference voltage in each of the N pixel circuits; obtaining N brightness data corresponding to N areas of an image displayed on the display panel, respectively, in a second period of the frame period; and driving an LED element during a light-emission time corresponding to the N brightness data using the reference voltage stored in the N pixel circuits in a third period of the frame period.

[0010] According to one aspect of an exemplary embodiment, a backlight driver includes: a first pixel circuit configured to drive a first plurality of light emitting diode (LED) elements corresponding to a first area of ​​a display panel; a second pixel circuit configured to drive a second plurality of LED elements corresponding to a second area of ​​the display panel; and a panel driver including a current source connected in parallel with the first pixel circuit and the second pixel circuit, and configured to provide a reference current to the first pixel circuit and the second pixel circuit based on the current source. The first pixel circuit is configured to obtain a reference voltage based on the reference current and store the reference voltage according to a first write signal provided from the panel driver, and to drive the first plurality of LED elements based on first brightness data indicating brightness corresponding to the first area, and the second pixel circuit is configured to obtain a reference voltage based on the reference current and store the reference voltage according to a second write signal provided from the panel driver, and to drive the second plurality of LED elements based on second brightness data indicating brightness corresponding to the second area. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Example embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0012] Figure 1 is a block diagram illustrating a display device according to an example embodiment;

[0013] Figure 2 is a diagram illustrating a display panel and a backlight unit according to an example embodiment;

[0014] Figure 3 is a block diagram illustrating a backlight driver according to an example embodiment;

[0015] Figure 4 is a diagram illustrating an operation of a backlight driver per frame period according to an exemplary embodiment;

[0016] Figure 5 is a diagram showing a pixel circuit according to an example embodiment;

[0017] Fig. 6A and Figure 6B is a diagram showing a current-voltage conversion circuit according to an example embodiment;

[0018] Fig. 7A , Figure 7B and Figure 7C is a diagram showing a sample-and-hold circuit according to an example embodiment;

[0019] Fig. 8A is a diagram illustrating a current writing (CW) operation to which a pulse width modulation (PWM) method is applied according to an example embodiment; Figure 8Bis a diagram showing a modified example embodiment;

[0020] Fig. 9 is a diagram illustrating a CW operation to which a pulse amplitude modulation (PAM) method and a PWM method are applied according to an example embodiment;

[0021] Fig. 10A , Fig. 10B and Fig. 10C is a diagram illustrating an operation of a backlight driver per frame period according to an exemplary embodiment;

[0022] Fig.11 is a diagram illustrating an operation of a pixel circuit per frame period according to an example embodiment;

[0023] Fig.12 is a block diagram illustrating a backlight driver according to an example embodiment;

[0024] Fig.13 is a block diagram illustrating a backlight driver according to an example embodiment;

[0025] Fig.14 is a diagram showing each frame period according to an example embodiment. Fig.13 A diagram of the operation of a backlight driver;

[0026] Fig.15 is a flowchart illustrating a method of driving a backlight device according to an example embodiment;

[0027] Fig.16 is a diagram illustrating a backlight device according to an example embodiment;

[0028] Fig.17 is a diagram illustrating a backlight device according to an example embodiment;

[0029] Fig.18 is a diagram illustrating a display device according to an example embodiment; and

[0030] Fig.19 is a diagram illustrating a display device according to an example embodiment. DETAILED DESCRIPTION

[0031] Figure 1 is a block diagram illustrating a display apparatus 1000 according to an example embodiment.

[0032] refer to Figure 1, the display device 1000 may include a timing controller 1100, a source driver 1200, a gate driver 1300, a display panel 1400, a backlight unit 1500, and a backlight driver 1600. In some example embodiments, a configuration including the timing controller 1100, the source driver 1200, the gate driver 1300, and the backlight driver 1600 may be referred to as a display driver. In some example embodiments, a configuration including the backlight unit 1500 and the backlight driver 1600 may be referred to as a backlight device 1700. In some example embodiments, the display device 1000 may further include components such as a voltage generator that generates various voltages required to drive the display device 1000 and a memory that stores data.

[0033] The display device 1000 may be mounted on an electronic device having an image display function. For example, the electronic device may include a smartphone, a tablet personal computer (PC), a portable multimedia player (PMP), a camera, a wearable device, a television, a digital video disc (DVD) player, a refrigerator, an air conditioner, an air purifier, a set-top box, a robot, a drone, various medical devices, a navigation device, a global positioning system receiver, a vehicle device, furniture, or various measuring devices.

[0034] The timing controller 1100 may control the overall operation of the display device 1000. For example, the timing controller 1100 may control the source driver 1200 and the gate driver 1300 so that the image data IDT received from the external device is displayed on the display panel 1400.

[0035] Specifically, the timing controller 1100 may generate pixel data RGB_DT in a format corresponding to the interface specification of the source driver 1200 based on the image data IDT received from the outside, and may output the pixel data RGB_DT to the source driver 1200. For example, the pixel data RGB_DT may include a red component RED, a blue component BLUE, and a green component GREEN of each pixel constituting an image. In addition, the timing controller 1100 may generate various control signals CTRL1 and CTRL2 for controlling the timing of the source driver 1200 and the gate driver 1300, respectively. The timing controller 1100 may output a first control signal CTRL1 to the source driver 1200, and output a second control signal CTRL2 to the gate driver 1300.

[0036] In addition, the timing controller 1100 may generate brightness data LDT indicating brightness of the image based on the image data IDT, and output the generated brightness data LDT to the backlight driver 1600. The brightness data LDT may be generated for each frame. In some example embodiments, the timing controller 1100 may reflect the generated brightness data LDT to the pixel data RGB_DT.

[0037] The source driver 1200 may convert the pixel data RGB_DT received from the timing controller 1100 into a plurality of image signals, for example, a plurality of data voltages, and output the plurality of data voltages to the display panel 1400 through the plurality of source lines SL1 to SLm. The gate driver 1300 may be connected to the plurality of gate lines GL1 to GLn of the display panel 1400, and may sequentially drive the plurality of gate lines GL1 to GLn of the display panel 1400.

[0038] The display panel 1400 is a display on which an actual image is displayed, and may be a display device that receives an electrically transmitted image signal and displays a 2D image, such as an organic light emitting diode (OLED) display, a thin film transistor-liquid crystal display (TFT-LCD), a field emission display, a plasma display panel (PDP), etc. However, example embodiments are not limited thereto, and the display panel 1400 may be implemented as another type of flat panel display or a flexible display panel. Hereinafter, the display panel 1400 will be described as a TFT-LCD implemented as an element that does not emit light itself.

[0039] The display panel 1400 may include a plurality of gate lines GL1 to GLn, a plurality of source lines SL1 to SLm disposed in a direction intersecting the plurality of gate lines GL1 to GLn, and a plurality of pixels PX arranged in regions where the plurality of gate lines GL1 to GLn and the plurality of source lines SL1 to SLm intersect.

[0040] The backlight unit 1500 may be disposed on the rear surface of the display panel 1400 to provide additional illumination to improve the contrast of the display panel 1400. To this end, the backlight unit 1500 may include a plurality of light emitting diode (LED) elements that emit light under the control of the backlight driver 1600. The plurality of LED elements may be divided into a plurality of dimming groups corresponding to a plurality of regions of the display panel 1400, and the number of LED elements included in each of the plurality of dimming groups may be the same or different, respectively. Each of the plurality of LED elements may be implemented as a blue LED element or a white LED element, but example embodiments are not limited thereto, and each of the plurality of LED elements may be implemented as various LED elements, such as a red LED element and a green LED element.

[0041] The backlight driver 1600 may drive the plurality of LED elements of the backlight unit 1500 by using a local dimming method. Specifically, the backlight driver 1600 may control the plurality of LED elements so that the plurality of dimming groups of the backlight unit 1500 emit light at separate brightnesses. In some example embodiments, the backlight driver 1600 may control the plurality of LED elements using brightness data LDT received from the timing controller 1100 so that the plurality of dimming groups emit light at separate brightnesses.

[0042] Figure 2 1 is a diagram showing a display panel 1400 and a backlight unit 1500 according to an example embodiment. Specifically, Figure 2 It is shown Figure 1 FIG. 1 is a diagram of a display panel 1400 and a backlight unit 1500 .

[0043] The display panel 1400 may be divided into a plurality of regions arranged in m rows and n columns (i.e., m×n arrangement (m and n are positive integers)), and the backlight unit 1500 may be further divided into a plurality of dimming groups arranged in m×n arrangement corresponding to the plurality of regions, respectively. Figure 2 , the display panel 1400 may be divided into a plurality of regions arranged in 4×4, and the backlight unit 1500 may be divided into a plurality of dimming groups arranged in 4×4. In other words, the display panel 1400 may be divided into the first region to the sixteenth region, and the backlight unit 1500 may be divided into the first dimming group to the sixteenth dimming group corresponding to the first region to the sixteenth region, respectively. The m×n arrangement of the plurality of dimming groups is not limited to the above example, and various m×n arrangements may be applied.

[0044] The backlight driver 1600 may confirm the brightness of the image displayed on each of the plurality of regions of the display panel 1400 based on the received brightness data LDT. In addition, the backlight driver 1600 may drive the backlight unit 1500 to emit light at a brightness corresponding to the brightness of the plurality of regions for each dimming group. The brightness data LDT may include a plurality of levels indicating the degree of brightness of the image.

[0045] For example, the backlight driver 1600 may determine the brightness of the image displayed on the first area of ​​the display panel 1400 based on the brightness data LDT, and may control the LED elements included in the first dimming group of the backlight unit 1500 to emit light at a brightness corresponding to the determined brightness. Figure 5 A detailed description of a method of driving the backlight unit 1500 based on the brightness data LDT of the backlight driver 1600 is described.

[0046] exist Figure 1 and Figure 2, it is described that the backlight driver 1600 receives the brightness data LDT and drives the backlight unit 1500 using the received brightness data LDT, but example embodiments are not limited thereto. For example, the backlight driver 1600 may be implemented to receive the image data IDT or the pixel data RGB_DT from the timing controller 1100, calculate the brightness of a plurality of regions of the display panel 1400 using the received image data IDT or the pixel data RGB_DT, and drive the backlight unit 1500 based on the calculated brightness.

[0047] Figure 3 1 is a block diagram showing a backlight driver 1600 according to an example embodiment. Specifically, Figure 3 It is shown Figure 1 FIG. 16 is a diagram of a backlight driver 1600 .

[0048] refer to Figure 3 , the backlight driver 1600 may include a panel driver 100 that provides power and a pixel circuit group 200 that drives a plurality of LED elements of the backlight unit 1500 based on the power provided. The pixel circuit group 200 may include M (M is a positive integer) pixel circuits (ICs) 210_1, 210_2 ... and 210_M. Each of the pixel circuits 210_1, 210_2 ... and 210_M may drive an LED element included in at least one of the plurality of dimming groups of the backlight unit 1500, or some LED elements included in any one of the dimming groups. That is, each of the pixel circuits 210_1, 210_2 ... and 210_M may correspond to at least some of the plurality of regions of the display panel 1400. The number of LED elements driven by the pixel circuits 210_1, 210_2 ... and 210_M, respectively, may be the same or different.

[0049] The panel driver 100 and the pixel circuit group 200 may repeatedly perform a current storage operation for driving an LED element, a storage operation of brightness data LDT corresponding to the brightness of the LED element to be driven, and a driving operation of the LED element for each frame period, which is a time allocated to each frame. Hereinafter, the above operations performed within the frame period will be described in detail.

[0050] The panel driver 100 may provide the reference current to the pixel circuit group 200 by using a time division method. Specifically, the panel driver 100 may provide the reference current to the pixel circuit group 200 only in the first period of the frame period. In addition, the panel driver 100 may include a pixel driver 110 and a current write (CW) controller 120. The pixel driver 110 may include a current source 112 and a current source controller 114, and the current source controller 114 may control the current source 112 to provide the reference current in the first period. In an example embodiment, the current source controller 114 may control the amplitude of the reference current or control the duty cycle of the reference current. This will be described later. Fig. 8A and Figure 8B This is described in detail.

[0051] Because the pixel driver 110 is connected in parallel to the pixel circuits 210_1, 210_2 ... and 210_M through a common line, the reference current provided from the current source 112 can be provided in parallel in the pixel circuits 210_1, 210_2 ... and 210_M. That is, the pixel circuits 210_1, 210_2 ... and 210_M can share the current source 112. In addition, the pixel circuits 210_1, 210_2 ... and 210_M can copy and store the provided reference current. In the following, for ease of description, the operation of providing a reference current and copying and storing the provided reference current is referred to as a CW operation. The name of the operation is not limited to the above example, and may be referred to as a charging operation.

[0052] The CW controller 120 may output a write signal WRITE<1:M> indicating the execution time of the CW operation in response to the supply of the reference current. The write signal WRITE<1:M> may be provided by M lines connecting the CW controller 120 and each of the pixel circuits 210_1, 210_2, ..., and 210_M. For example, the write signal WRITE<1:M> <1> The write signal WRITE may be provided to the first pixel circuit 210_1 through the first line. <2> The second pixel circuit 210_2 may be provided with a write signal WRITE through the second line. <m>The reference current may be provided to the Mth pixel circuit 210_M through the Mth line. The pixel circuits 210_1, 210_2, . . . and 210_M may copy and store the reference current according to the write signal WRITE<1:M>, and drive the LED element based on the stored reference current.

[0053] Because the pixel driver 110 is connected in parallel with the pixel circuits 210_1, 210_2 ... and 210_M, when the pixel circuits 210_1, 210_2 ... and 210_M simultaneously copy the current, the amplitude of the current reaching each of the pixel circuits 210_1, 210_2 ... and 210_M may be reduced to 1 / M, so that the amplitude of the copied current may be insufficient. Therefore, the CW controller 120 may generate a write signal WRITE<1:M> so that the execution time of the CW operation of the pixel circuits 210_1, 210_2 ... and 210_M is different from each other. For example, the CW controller 120 may generate a write signal WRITE<1:M> so that the execution time of the CW operation of the second pixel circuit 210_2 is arranged after the execution time of the CW operation of the first pixel circuit 210_1. Since the pixel driver 110 may provide the reference current to the pixel circuits 210_1 , 210_2 . . . , and 210_M only in the first period, all execution times of the CW operations of the pixel circuits 210_1 , 210_2 . . . , and 210_M may be within the first period.

[0054] The pixel circuits 210_1, 210_2 ... and 210_M may perform a CW operation of copying and storing a reference current in a first period of a frame period. In addition, the pixel circuits 210_1, 210_2 ... and 210_M may store corresponding brightness data LDT in a second period of a frame period. Here, the brightness data LDT represents the brightness of an image displayed on a partial area of ​​the display panel 1400 corresponding to each of the pixel circuits 210_1, 210_2 ... and 210_M. For example, the brightness data LDT of the first pixel circuit 210_1 represents the brightness of an image displayed on a partial area (e.g., the first area) of the display panel 1400 corresponding to the first pixel circuit 210_1.

[0055] In some example embodiments, the brightness data LDT may be implemented by using a pulse width modulation (PWM) method. That is, the brightness data LDT may be implemented in the form of a pulse having a width corresponding to the brightness of the image. Hereinafter, for ease of explanation, it is described that the brightness data LDT is implemented by using a PWM method, and operations such as receiving and storing the brightness data LDT from the timing controller 1100 are referred to as LDR operations.

[0056] In addition, the pixel circuits 210_1, 210_2 ... and 210_M can drive the LED element in the third period of the frame period using the reference current stored in the first period of the frame period. In this regard, the pixel circuits 210_1, 210_2 ... and 210_M can drive the LED element with a brightness corresponding to the stored brightness data LDT. For example, the first pixel circuit 210_1 can drive the LED element to emit light during the light emitting (LE) time corresponding to the brightness data LDT of the first pixel circuit 210_1. As the brightness of the image displayed on the display panel 1400 increases, additional illumination of the backlight unit 1500 is required. Therefore, as the brightness data LDT shows a higher brightness, the pixel circuits 210_1, 210_2 ... and 210_M can drive the LED element for a longer LE time. In the following, for ease of description, the operation of driving the LED element is referred to as LE operation.

[0057] In this way, the backlight driver 1600 may include pixel circuits 210_1, 210_2, ..., and 210_M configured to share the current source 112, and may drive a plurality of LED elements based on one pixel driver, thereby reducing components, which may reduce the size of the backlight driver 1600 and reduce manufacturing costs. In addition, since the backlight driver 1600 provides current only in the first period of the frame period, power consumption may be reduced.

[0058] Figure 4 is a diagram illustrating the operation of the backlight driver 1600 per frame period according to an exemplary embodiment. Specifically, Figure 4 is a graph showing the period of each frame. Figure 3 FIG. 16 is a diagram of the operation of the backlight driver 1600 .

[0059] refer to Figure 4 , the backlight driver 1600 may operate in units of frame periods T_FRAME. For example, the backlight driver 1600 may first perform a CW operation in a frame period corresponding to the first frame FRAME 1. In this case, the CW operation may be sequentially performed for each of the pixel circuits 210_1, 210_2, ..., and 210_M included in the backlight driver 1600. That is, Figure 3 As shown, when the backlight driver 1600 includes M pixel circuits 210_1, 210_2, ..., and 210_M, the backlight driver 1600 may perform a CW operation WRITE on the first pixel circuit 210_1. <1> Then, the CW operation WRITE of the second pixel circuit 210_2 is performed. <2> In the above manner, the backlight driver 1600 can complete the CW operation WRITE of the Mth pixel circuit 210_M. <m>In this way, the period in which the CW operation is performed may be referred to as a first period. However, example embodiments are not limited thereto, and the first period may be referred to as a charging period or another name.

[0060] In addition, when the CW operation is completed, the backlight driver 1600 may perform an LDR operation. That is, each of the M pixel circuits 210_1, 210_2 ... and 210_M may receive and store brightness data LDT representing the brightness of an image displayed on a partial area of ​​the display panel 1400 from the timing controller 1100. In this way, the period in which the LDR operation is performed may be referred to as a second period. However, example embodiments are not limited thereto, and the second period may be referred to as a data reading period or another name.

[0061] In addition, when the LDR operation is completed, the backlight driver 1600 may perform an LE operation. That is, each of the M pixel circuits 210_1, 210_2 ... and 210_M may be driven so that the LED element emits light during the LE time corresponding to the brightness data LDT of the backlight unit 1500. The period in which the LE operation is performed may be referred to as a third period. However, example embodiments are not limited thereto, and the third period may be referred to as an LE period or another name.

[0062] In some example embodiments, the backlight driver 1600 may repeat the CW operation, the LDR operation, and the LE operation for each frame period. Figure 4 , the backlight driver 1600 may perform the CW operation, the LDR operation, and the LE operation in a frame period regarding the first frame FRAME 1. In addition, the backlight driver 1600 may perform the CW operation, the LDR operation, and the LE operation in a frame period regarding the second frame FRAME 2.

[0063] Figure 5 is a diagram illustrating a pixel circuit 210 according to example embodiments.

[0064] Figure 5 The pixel circuit 210 may correspond to Figure 3 Any one of the pixel circuits 210_1, 210_2, ... and 210_M. Figure 5 , the pixel circuit 210 may include a current-voltage conversion circuit 220, a sample-and-hold circuit 230, an LED driver group 240, a switch circuit 250, and a data storage 260. In some example embodiments, the data storage 260 may include a switch controller 261 and a memory 263.

[0065] In the first period of the frame period, the current-voltage conversion circuit 220 and the sample-and-hold circuit 230 may perform a CW operation of converting the reference current I_REF into a voltage and storing the converted voltage. In the second period of the frame period, the data storage 260 may perform an LDR operation. In the third period of the frame period, the sample-and-hold circuit 230, the LED driver group 240, the switch circuit 250, and the data storage 260 may perform an LE operation to drive the LED element. Hereinafter, the structure and operation of the components of the pixel circuit 210 will be described in detail.

[0066] The pixel circuit 210 may be connected to a pixel driver ( Figure 3 The current source 112 of the pixel circuit 210 may be provided by the current source controller 114. The current source 112 may output a reference current I_REF under the control of the current source controller 114. In addition, the reference current I_REF may be input to the current-voltage conversion circuit 220 of the pixel circuit 210. The reference current I_REF may be provided during a first period of a frame period in which a CW operation is performed.

[0067] The current-voltage conversion circuit 220 may receive a reference current I_REF from the current source 112 connected to the pixel circuit 210, convert the input reference current I_REF into a voltage, and output the converted voltage to the sample-and-hold circuit 230. For example, the reference current I_REF may be a reference current I_REF. Figure 5 The current-voltage conversion circuit 220 may include a first transistor M1 having a drain terminal connected to the current source 112 and a gate terminal connected to the drain terminal, and a first resistor R1 having one end connected to the source terminal of the first transistor M1 and the other end connected to the ground. The gate terminal of the first transistor M1 may be connected to the sample-and-hold circuit 230.

[0068] In some example embodiments, the current-to-voltage conversion circuit 220 may be configured to receive a voltage from a CW controller ( Figure 3 120) receives a write signal WRITE and selectively converts the reference current I_REF into a voltage according to the write signal WRITE. Figure 5 , the current-voltage conversion circuit 220 may further include a switch SW1 that is disposed on a line connecting the current source 112 and the first transistor M1 and is driven according to a write signal WRITE. The write signal WRITE may be implemented as a signal having an effective level in a first period of a frame period at an execution time of a CW operation assigned to the pixel circuit 210. Accordingly, when the write signal WRITE has an effective level, the switch SW1 is closed so that the reference current I_REF may be input to the current-voltage conversion circuit 220. The execution time of the CW operation assigned to the pixel circuit 210 may be referred to as a sampling period, etc.

[0069] The sample and hold circuit 230 can sample and store the voltage converted by the current-voltage conversion circuit 220. Figure 5 , the sample and hold circuit 230 may include a second switch SW2 for sampling a voltage and a first capacitor C1 for holding (ie, storing) the voltage. In addition, the sample and hold circuit 230 may include a low pass filter (LPF) to remove noise. However, example embodiments are not limited thereto, and the LPF may be omitted.

[0070] The sample-and-hold circuit 230 may selectively sample the converted voltage according to the write signal WRITE received from the CW controller 120. In other words, the sample-and-hold circuit 230 may sample and store the converted voltage during the first period of the frame period, during the execution time of the CW operation allocated to the pixel circuit 210. For example, referring to Figure 5 , when the write signal WRITE indicates that the CW operation is to be performed, the second switch SW2 is closed so that the converted voltage can be sampled. In addition, the sampled voltage can be stored by the first capacitor C1 and can be maintained when the second switch SW2 is opened. In addition, the sample and hold circuit 230 can output the voltage maintained (i.e., stored) in the third period of the frame period in which the LE operation is performed.

[0071] The LED driver group 240 may drive the LED elements of the backlight unit 1500 based on the voltage provided from the sample and hold circuit 230. Specifically, the LED driver group 240 may drive the LED elements in the third period of the frame period in which the LE operation is performed. In some example embodiments, the LED driver group 240 may include K (K is a positive integer) LED drivers 240_1, 240_2... and 240_K, and the K LED drivers 240_1, 240_2... and 240_K drive the K LED elements LED_1, LED_2... and LED_K of the backlight unit 1500, respectively. The K LED drivers 240_1, 240_2... and 240_K may be connected in parallel to the sample and hold circuit 230. For example, referring to Figure 5 Each of the K LED drivers 240_1, 240_2... and 240_K may include a second transistor M2 and a second resistor R2, the second transistor M2 having a gate terminal connected to the sample and hold circuit 230 and a drain terminal connected to the LED element, and the second resistor R2 having one end connected to the source terminal of the second transistor M2 and the other end connected to the ground.

[0072] The switch circuit 250 may be disposed between the LED driver group 240 and the K LED elements LED_1, LED_2, ..., and LED_K. In some examples, the switch circuit 250 may include K switches SW3_1, SW3_2, ..., and SW3_K disposed between the K LED drivers 240_1, 240_2, ..., and 240_K and the K LED elements LED_1, LED_2, ..., and LED_K. According to the control of the switch controller 261, the K switches SW3_1, SW3_2, ..., and SW3_K of the switch circuit 250 may be opened and closed (i.e., opened or closed).

[0073] The data storage 260 may receive an enable signal EN and selectively perform an LDR operation according to the enable signal EN. The enable signal EN may be implemented as a signal having an active level in a second period of a frame period and may be generated by the panel driver 100 or the timing controller 1100. When the enable signal EN has an active level, the data storage 260 may perform an LDR operation.

[0074] Specifically, the switch controller 261 of the data storage 260 may receive the brightness data LDT directly from the timing controller 1100 in response to the enable signal EN in the second period of the frame period, or may read the brightness data LDT stored in the memory 263. The memory 263 may receive and store the brightness data LDT from the timing controller 1100. In addition, the switch controller 261 may control the switch circuit 250 based on the brightness data LDT obtained in the third period of the frame period in which the LE operation is performed.

[0075] In some example embodiments, the switch controller 261 may control the K switches SW3_1, SW3_2 ... and SW3_K of the switch circuit 250 to be closed (i.e., operated) during the LE time corresponding to the brightness data LDT. In some example embodiments, when the brightness data LDT is implemented by using a PWM method, the switch circuit 250 may control the K switches SW3_1, SW3_2 ... and SW3_K to be closed during the LE time corresponding to the width of the pulse of the brightness data LDT. For example, the switch circuit 250 may control the K switches SW3_1, SW3_2 ... and SW3_K to be closed for a longer LE time as the width of the pulse of the brightness data LDT increases.

[0076] In some example embodiments, the switch controller 261 may be implemented in various forms, such as a central processing unit (CPU), a processor, a microprocessor, an application processor (AP), a microcontroller unit (MCU), a microcomputer, or a mini computer.

[0077] Fig. 6A and Figure 6B 2 is a diagram showing current-voltage conversion circuits 220a and 226b according to an example embodiment. Specifically, Fig. 6A and Figure 6B It is shown Figure 5 FIG. 2 is a diagram of an example of a current-to-voltage conversion circuit 220 .

[0078] Figure 5 The pixel circuit 210 can use one write signal WRITE to simultaneously control the first switch SW1 of the current-voltage conversion circuit 220 and the second switch SW2 of the sample-and-hold circuit 230. Since the above structure can be implemented by simply connecting the first switch SW1 to the second switch SW2, the pixel circuit 210 can correspond to the simplest circuit.

[0079] In order to stably sample the reference current I_REF, it may be advantageous to have the first switch SW1 and the second switch SW2 drive timings different from each other. Specifically, because the supply of the reference current I_REF must be continuously maintained while sampling the voltage converted from the reference current I_REF, the time when the first switch SW1 changes from closed to open may be implemented to be after the time when the second switch SW2 changes from closed to open. Fig. 6A and Figure 6B Describing the pixel circuits 210 a and 210 b , the pixel circuits 210 a and 210 b are implemented such that the driving timings of the first switch SW1 and the second switch SW2 are different from each other.

[0080] refer to Fig. 6A , the pixel circuit 210a can receive a first write signal WRITE and a second write signal WRITE_D. Here, the first write signal WRITE is Figure 5 Furthermore, the second write signal WRITE_D has a first level which is an active level simultaneously with the first write signal WRITE, but becomes a second level which is an inactive level at a later time than the first write signal WRITE.

[0081] Similar to Figure 5 In an exemplary embodiment, the first write signal WRITE is used to control the operation of the second switch SW2 of the sample and hold circuit 230. Figure 5 In contrast to the example embodiment of FIG. 2 , the current-voltage conversion circuit 220 a may operate based on the second write signal WRITE_D. Therefore, the first switch SW1 and the second switch SW2 are closed at the same time, but after the second switch SW2 is opened, the first switch SW1 may be opened (ie, become open).

[0082] refer to Fig. 6A , it is described and illustrated that the second write signal WRITE_D has a valid level at the same time as the first write signal WRITE, but example embodiments are not limited thereto. For example, the second write signal WRITE_D may be implemented to have a valid level at a later time than the first write signal WRITE.

[0083] Instead of the example embodiment of separately receiving the first write signal WRITE and the second write signal WRITE_D, the example embodiment of generating the second write signal WRITE_D using the first write signal WRITE may also be implemented. Figure 6B , the current-voltage conversion circuit 220b may include a delay element DE that generates a delay relative to the signal. According to example embodiments, for example, the delay element DE may be implemented as an analog element or a digital element such as a shift register, and may be implemented as a combination of an analog element and a digital element.

[0084] The current-voltage conversion circuit 220b may receive the first write signal WRITE and delay the first write signal WRITE using the delay element DE to generate a second write signal WRITE_D. In addition, the current-voltage conversion circuit 220b may drive the first switch SW1 based on the generated second write signal WRITE_D.

[0085] Fig. 7A , Figure 7B and Figure 7C is a diagram showing sample-and-hold circuits 230a and 230b according to an example embodiment. Specifically, Fig. 7A , Figure 7B and Figure 7C It is shown Figure 5 FIG. 2 is a diagram of a modified example of the sample-and-hold circuit 230 .

[0086] Figure 5 The sample-and-hold circuit 230 can sample a voltage using the second switch SW2 and store and discharge the voltage using the first capacitor C1. Since the above structure stores a voltage using only the first capacitor C1, the sample-and-hold circuit 230 can correspond to the simplest circuit.

[0087] In the process of supplying or stopping the supply of current to the LED element through the sample and hold circuit 230, the drain voltage of the second transistor M2 included in the LED driver group 240 may change. The voltage change of the second transistor M2 may also affect the voltage stored in the first capacitor C1. Therefore, in order to stabilize the voltage stored in the first capacitor C1, an analog buffer may be further included. Fig. 7A , Figure 7B and Figure 7C Sample-and-hold circuits 230a and 230b are described as including analog buffers.

[0088] Fig. 7A A sample-and-hold circuit according to an example embodiment is shown. Fig. 7A The sample and hold circuit 230a may include a second switch SW2, a first capacitor C1, a first OPAMP OP1, a third switch SW3, and a fourth switch SW4. The sample and hold circuit 230a may further include a low pass filter LPF configured as the second capacitor C2, but example embodiments are not limited thereto and the low pass filter LPF may be omitted.

[0089] Similar to Figure 5 The sampling and holding circuit 230 of the second switch SW2 can sample the voltage converted by the current-voltage conversion circuit 220, and the first capacitor C1 can store the sampled voltage. One end of the second switch SW2 can be connected to the current-voltage conversion circuit 220, and the other end can be connected to one end of the first capacitor C1. In addition, the (-) terminal of the first OPAMP OP1 can be connected to the other end of the first capacitor C1 and one end of the third switch SW3, the (+) terminal of the first OPAMP OP1 can be grounded, and the output terminal of the first OPAMP OP1 can be connected to the other end of the third switch SW3 and one end of the fourth switch SW4. The other end of the fourth switch SW4 can be connected to the node between the second switch SW2 and the first capacitor C1. The third switch SW3 and the fourth switch SW4 operate oppositely to each other, so that the first capacitor C1 can maintain the voltage.

[0090] Figure 7B A sample-and-hold circuit according to an example embodiment is shown. Figure 7B , the sampling and holding circuit 230b may include a second OPAMP OP2, and may be implemented to change the connection relationship between the input terminals of the second OPAMP OP2 based on a specific frequency fMOD, and also change the connection relationship between its output terminals based on the specific frequency fMOD. Accordingly, low-frequency noise with a large amplitude such as flicker noise can be effectively removed. The sampling and holding circuit 230b may also include a low-pass filter LPF, which includes a second capacitor C2 and a third resistor R3, but example embodiments are not limited thereto, and the low-pass filter LPF may be omitted.

[0091] Figure 7C It specifically shows Figure 7B The circuit diagram of the sample and hold circuit 230b is shown in FIG. Figure 7C , the second OPAMP OP2 of the sample and hold circuit 230b may include switches SW5, SW8, SW11, and SW12 operated according to the first switch control signal SC1, switches SW6, SW7, SW9, and SW10 operated according to the second switch control signal SC2, a plurality of transistors M3, M4, M5, and M6, and a current source I3. The first switch control signal SC1 and the second switch control signal SC2 have a period corresponding to the inverse of the specific frequency fMOD, and have levels opposite to each other.

[0092] The pixel circuit 210 may further include a sample-and-hold controller capable of controlling the sample-and-hold circuits 230a and 230b. The sample-and-hold controller may control the first OPAMP OP1, the third switch SW3, and the fourth switch SW4 of the sample-and-hold circuit 230a, or the second OPAMP OP2 of the sample-and-hold circuit 230b. In some example embodiments, the sample-and-hold controller may be implemented in various forms, such as a central processing unit (CPU), a processor, a microprocessor, an application processor (AP), a microcontroller unit (MCU), a microcomputer, or a minicomputer.

[0093] In addition to the sample-and-hold circuits 230, 230a, and 230b according to the above-described exemplary embodiments, circuits having various forms may also be applied. For example, a circuit to which a semi-virtual switch is added may be applied. In addition, in addition to the exemplary embodiments in which the low-pass filter LPF is configured as a capacitor or a resistor and a capacitor, a circuit including an active element may also be applied.

[0094] In addition, refer to Figure 5 , Fig. 7A and Figure 7B , it is described that one pixel circuit 210 may include one sampling and holding circuit 230, 230a or 230b, but one pixel circuit 210 may include multiple sampling and holding circuits 230, 230a and 230b, and the multiple sampling and holding circuits 230, 230a and 230b may be implemented to provide voltages to K LED elements LED_1, LED_2, ... and LED_K. For example, when n sampling and holding circuits 230, 230a and 230b are included, each of the sampling and holding circuits 230, 230a and 230b may be implemented to provide voltages to K / n LED elements.

[0095] In another example embodiment, one pixel circuit 210 may include one sample-and-hold circuit 230a or 230b, but the sample-and-hold circuits 230a and 230b may include a plurality of analog buffers OPAMP OP1 and OP2. That is, the sample-and-hold circuits 230a and 230b include only one first capacitor C1 storing the converted voltage, but may include a plurality of analog buffers OP1 and OP2 connected to the first capacitor C1. The plurality of analog buffers OP1 and OP2 may be implemented to provide voltages to K LED elements LED_1, LED_2, ..., and LED_K.

[0096] Fig. 8A and Figure 8B is a diagram illustrating a CW operation according to an example embodiment.

[0097] The panel driver 100 may drive the LED elements of the backlight unit 1500 by supplying current to the pixel circuit group 200 in various ways. The current supply method may include a pulse amplitude modulation (PAM) method that changes the amplitude of the current, a PWM method that changes the output duty ratio of the current, and a hybrid method that simultaneously applies the PAM method and the PWM method.

[0098] Since the panel driver 100 supplies the reference current to the pixel circuit 210 only in the first period of the frame period, the panel driver 100 can be basically operated by the PWM method. In this way, since the reference current is not supplied in the entire frame period, current consumption can be reduced.

[0099] According to an example embodiment, the panel driver 100 can further reduce current consumption. Specifically, the panel driver 100 does not provide a reference current for each frame period, but provides a reference current for each preset number of frame periods, thereby further reducing the amount of current consumption. In other words, the panel driver 100 can perform a CW operation at a period corresponding to a preset number of frame periods (hereinafter, referred to as a CW period). At this point, when a reference current of sufficient magnitude is stored through one CW operation, the LED element can emit light during multiple frame periods using the stored reference current.

[0100] For example, refer to Fig. 8A , the panel driver 100 may be implemented to provide a reference current in a CW period T_CW corresponding to three frame periods. The panel driver 100 may provide the reference current I_REF to the pixel circuit 210 in the frame period of the first frame FRAME1. In addition, the panel driver 100 may omit the provision of the reference current I_REF in the frame periods of the second frame FRAME 2 and the third frame FRAME 3. In addition, the panel driver 100 may provide the reference current I_REF to the pixel circuit 210 again in the frame period of the fourth frame FRAME 4. In addition, when providing the reference current I_REF, the panel driver 100 may also provide a write signal indicating the execution time of the CW operation. The pixel circuit 210 may perform a CW operation storing the reference current I_REF provided in the frame period corresponding to the first frame FRAME 1 and the fourth frame FRAME 4 according to the write signal.

[0101] The CW period T_CW may be set based on the capacitance of the first capacitor C1 of the sample and hold circuit 230 , the magnitude of the leakage current of the second switch SW2 , and the temperature variation characteristics of the second transistor M2 of the LED driving group 240 .

[0102] According to example embodiments, the pixel circuit 210 may be divided into a plurality of groups, and frame periods during which the plurality of groups perform a CW operation may be set to be different from each other.

[0103] For example, refer to Figure 8B , the pixel circuit 210 can be divided into three groups. In addition, among the three groups, the first group GROUP 1 can perform a CW operation in the first frame FRAME 1, the second group GROUP 2 can perform a CW operation in the second frame FRAME 2, and the third group GROUP 3 can perform a CW operation in the third frame FRAME 3. In addition, the three groups can repeat the CW operation for each CW period T_CW. The panel driver 100 can provide a write signal indicating the execution time of the CW operation for each of the three groups.

[0104] Fig. 9 is a diagram illustrating a CW operation according to an example embodiment, in which a PAM method and a PWM method are applied.

[0105] In some example embodiments, in order to further improve the contrast of the image displayed on the display panel 1400, the panel driver 100 may provide current by a hybrid method in which the PAM method is additionally applied to the PWM method. For example, in the case where the brightness of the image displayed on the display panel 1400 is very high, when the panel driver 100 increases the amplitude of the reference current according to the PAM method, the LED elements of the backlight unit 1500 may also provide brighter illumination, and accordingly, the contrast may be improved.

[0106] When the reference current is provided by the hybrid method, the panel driver 100 may receive the brightness data LDT from the timing controller 1100, determine the magnitude of the reference current based on the received brightness data LDT, and provide the reference current having the determined magnitude to the pixel circuit 210. Since the brightness data LDT may be generated for each frame, the panel driver 100 may change the magnitude of the reference current for each frame period.

[0107] For example, refer to Fig. 9 , the panel driver 100 may receive the first brightness data of the first frame FRAME1, determine the amplitude of the current based on the received first brightness data, and provide the reference current I_REF1 having the determined amplitude to the pixel circuit 210. In addition, the pixel circuit 210 may perform a CW operation of storing the provided reference current I_REF1. In addition, the panel driver 100 may receive the second brightness data of the second frame FRAME 2, determine the amplitude of the current based on the received second brightness data, and provide the reference current I_REF2 having the determined amplitude to the pixel circuit 210. In addition, the pixel circuit 210 may perform a CW operation of storing the provided reference current I_REF2.

[0108] In the above example, it is described that the panel driver 100 receives the brightness data LDT from the timing controller 1100 and determines the amplitude of the reference current based on the brightness data LDT, but example embodiments are not limited thereto. For example, the panel driver 100 may be implemented to receive the image data IDT or the pixel RGB_DT and determine the amplitude of the reference current based on the received image data IDT or the pixel RGB_DT.

[0109] Fig. 10A , Fig. 10B and Fig. 10C is a diagram illustrating an operation of a backlight driver 1600 per frame period according to an exemplary embodiment.

[0110] refer to Fig. 10A , as above Figure 4 As described above, the backlight driver 1600 may operate in the first method M1, that is, first perform the CW operation, then perform the LDR operation, and finally perform the LE operation.

[0111] The CW operation and the LDR operation can be performed independently of each other. Accordingly, the CW operation can be implemented to be performed later than the LDR operation. Fig. 10A , the backlight driver 1600 may operate in the second method M2, ie, first perform the LDR operation, then perform the CW operation, and finally perform the LE operation.

[0112] Alternatively, CW operation can be implemented to be performed simultaneously with LDR operation. Fig. 10A , the backlight driver 1600 may operate in a third method M3, ie, perform the CW operation and the LDR operation simultaneously, and finally perform the LE operation.

[0113] Alternatively, CW operation may be implemented to be performed simultaneously with LE operation. Fig. 10A , the backlight driver 1600 may operate in the fourth method M4, ie, perform the LDR operation and then simultaneously perform the CW operation and the LE operation.

[0114] According to an example embodiment, the backlight driver 1600 may operate in a manner that omits CW operation or LDR operation. For example, the panel driver 100 may not provide a reference current for each frame period, but may be implemented to provide a reference current for each preset number of frame periods. In this case, the backlight driver 1600 may omit CW operation in some frame periods.

[0115] For example, refer to Fig. 10B , backlight driver 1600 can sequentially perform CW operation, LDR operation and LE operation in the first frame FRAME 1. In addition, backlight driver 1600 can omit CW operation in the second frame FRAME 2, and sequentially perform LDR operation and LE operation. In this regard, in the period allocated to the existing CW operation, backlight driver 1600 may not perform a separate operation. However, example embodiments are not limited thereto, and backlight driver 1600 can perform LDR operation earlier and perform LE operation for a longer time in the above-mentioned period. Backlight driver 1600 can operate in the same manner as the second frame FRAME 2 until CW operation is necessary. As described above, backlight driver 1600 can operate in the fifth method M5, wherein CW operation is omitted in some frame periods.

[0116] As another example, when consecutive frames have the same brightness, the backlight driver 1600 may omit the LDR operation in some frame periods. For example, when the brightness of the previous frame is the same as the brightness of the current frame, because the brightness data LDT of the previous frame is also the same as the brightness data of the current frame, the timing controller 1100 may omit the transmission of the brightness data LDT to the backlight driver 1600. In this case, the backlight driver 1600 may latch and reuse the brightness data LDT of the previous frame.

[0117] For example, refer to Fig. 10C , the backlight driver 1600 may sequentially perform a CW operation, an LDR operation, and an LE operation in the first frame FRAME 1. In addition, the backlight driver 1600 may perform a CW operation in the second frame FRAME 2, latch the brightness data LDT of the first frame FRAME 1 (instead of the LDR operation), and perform an LE operation. As described above, the backlight driver 1600 may operate in the sixth method M6, in which the LDR operation is omitted in some frame periods.

[0118] refer to Fig. 10B and Fig. 10C , the fifth method M5 and the sixth method M6 are shown and described as performing the LDR operation after performing the CW operation, but the example embodiments are not limited thereto. For example, the fifth method M5 and the sixth method M6 may also change the arrangement of the CW operation and the LDR operation like the first method M1 to the fourth method M4.

[0119] In addition, the first method M1 to the fifth method M5 can be applied regardless of the current supply method (for example, the PWM method and the hybrid method). That is, in each of the first method M1, the second method M2, the third method M3, the fourth method M4, and the fifth method M5, a CW operation can be performed by supplying a current of a certain amplitude in a time division method according to the PWM method or by supplying a current with amplitude variation for each frame period according to the hybrid method.

[0120] Fig.11 is a diagram illustrating an operation of the pixel circuit 210 during a frame period according to an example embodiment.

[0121] As above reference Figure 1 to Figure 1 0, the backlight driver 1600 may perform the CW operation in the first period of the frame period, perform the LDR operation in the second period of the frame period, and perform the LE operation in the third period of the frame period. Since the CW operation is performed by sequentially supplying current to each of the pixel circuits 210, each of the pixel circuits 210 may wait for the remaining time except the execution time of the CW of the corresponding pixel circuit 210 in the first period.

[0122] According to an example embodiment, the backlight driver 1600 may be implemented to have a separate period in which a CW operation, an LDR operation, and an LE operation are performed on each of the pixel circuits 210. For example, the backlight driver 1600 may sequentially provide current to each of the pixel circuits 210, and each of the pixel circuits 210 may perform the following operations immediately after the CW operation is completed. The pixel circuits 210 may be implemented to perform the above operations in the same period (e.g., a frame period T_FRAME).

[0123] For example, refer to Fig.11 , the first pixel circuit 210_1 may be based on the write signal WRITE in the frame period T_FRAME <1> To perform the CW operation. In addition, when the CW operation is completed, the first pixel circuit 210_1 can then perform the LDR operation. In addition, when the LDR operation is completed, the first pixel circuit 210_1 can then perform the LE operation.

[0124] In addition, in the frame period T_FRAME, after the CW operation of the first pixel circuit 210_1 is completed, the second pixel circuit 210_2 may be switched based on the write signal WRITE <2> Perform CW operation. In addition, when the CW operation is completed, the second pixel circuit 210_2 can then perform LDR operation. In addition, when the LDR operation is completed, the first pixel circuit 210_1 can then perform LE operation. The LE operation of the second pixel circuit 210_2 may not be completed within one frame period T_FRAME, but may be performed within the next frame period.

[0125] When operating in this manner, the pixel circuit 210 can perform LE operation for a longer time by utilizing the existing waiting time. Therefore, even if the magnitude of the reference current is not increased, the magnitude of the illumination of the backlight unit 1500 can be increased.

[0126] Fig.12 2 is a block diagram showing a backlight driver 2000 according to an example embodiment. Specifically, Fig.12 It is shown Figure 3 FIG. 1 is a block diagram of a modified example of a backlight driver 1600. Fig.12 In the description of the backlight driver 2000, the Figure 3 Redundant description of backlight driver 1600.

[0127] refer to Fig.12 , the backlight driver 2000 may include a panel driver 300 and a plurality of pixel circuit groups 400_1, 400_2 ... and 400_N. Each of the plurality of pixel circuit groups 400_1, 400_2 ... and 400_N may include M (M is a positive integer) pixel circuits 410_1, 410_2 ... and 410_M, and the pixel circuits 410_1, 410_2 ... and 410_M may drive at least one LED element of the backlight unit 1500. The numbers of LED elements respectively driven by the pixel circuits 410_1, 410_2 ... and 410_M may be the same or different. The pixel circuits 410_1, 410_2 ... and 410_M may correspond to Figure 3 Pixel circuits 210_1, 210_2, ... and 210_M.

[0128] The panel driver 300 may include a plurality of pixel drivers 310_1, 310_2, ..., and 310_N corresponding to the plurality of pixel circuit groups 400_1, 400_2, ..., and 400_N, respectively. For example, the first pixel driver 310_1 may correspond to the first pixel circuit group 400_1, the second pixel driver 310_2 may correspond to the second pixel circuit group 400_2, and the Nth pixel driver 310_N may correspond to the Nth pixel circuit group 400_N.

[0129] The plurality of pixel drivers 310_1, 310_2, ..., and 310_N may include current sources 312_1, 312_2, ..., and 312_N and current source controllers 314_1, 314_2, ..., and 314_N, respectively. The plurality of pixel drivers 310_1, 310_2, ..., and 310_N may provide reference currents to corresponding pixel circuit groups.

[0130] The panel driver 300 may include a CW controller 320. The CW controller 320 may output a write signal WRITE<1:M> indicating an execution time of a CW operation in response to the supply of a reference current. The write signal WRITE<1:M> may be provided through M lines L1 to LM connected to the CW controller 320, and the M lines L1 to LM may be connected in parallel to the pixel circuits 410_1, 410_2 ... and 410_M of the plurality of pixel circuit groups 400_1, 400_2 ... and 400_N. For example, the write signal WRITE<1:M> may be provided through M lines L1 to LM connected to the CW controller 320, and the M lines L1 to LM may be connected in parallel to the pixel circuits 410_1, 410_2 ... and 410_M of the plurality of pixel circuit groups 400_1, 400_2 ... and 400_N. <1> The write signal WRITE may be provided to the first pixel circuit 410_1 of each of the plurality of pixel circuit groups 400_1, 400_2, ... and 400_N through the first line L1. <2> The write signal WRITE may be provided to the second pixel circuit 410_2 of each of the plurality of pixel circuit groups 400_1, 400_2, . . . and 400_N through the second line L2. <m>The Mth pixel circuit 410_M of each of the plurality of pixel circuit groups 400_1 , 400_2 . . . , and 400_N may be provided through the Mth line LM.

[0131] although Fig.12 The backlight driver 2000 with Figure 3 The difference of the backlight driver 1600 is that Fig.12 The backlight driver 2000 includes a plurality of pixel drivers 310_1, 310_2, ..., and 310_N and a plurality of pixel circuit groups 400_1, 400_2, ..., and 400_N, but Fig.12 The backlight driver 2000 can be used with the above Figures 4 to 11 The example embodiments in FIG. 1 operate in substantially the same manner.

[0132] Fig.13 is a block diagram showing a backlight driver 3000 according to an example embodiment. Specifically, Fig.13 It is shown Fig.12 FIG. 2 is a block diagram of a modified example of the backlight driver 2000. Fig.13 In the description of the backlight driver 3000, the Fig.12 Redundant description of the backlight driver 2000.

[0133] refer to Fig.13 , the backlight driver 3000 may include a panel driver 500 and a plurality of pixel circuit groups 600_1, 600_2, ..., and 600_N. The plurality of pixel circuit groups 600_1, 600_2, ..., and 600_N may correspond to Fig.12 The panel driver 500 may include a plurality of pixel circuit groups 400_1, 400_2 ... and 400_N. The panel driver 500 may include a plurality of pixel drivers 510_1, 510_2 ... and 510_N corresponding to the plurality of pixel circuit groups 600_1, 600_2 ... and 600_N, respectively. The plurality of pixel drivers 510_1, 510_2 ... and 510_N may include current sources 512_1, 512_2 ... and 512_N and current source controllers 514_1, 514_2 ... and 514_N, respectively.

[0134] The panel driver 500 may include a CW controller 520. According to an example embodiment, when Fig.12 When the CW controller 320 compares the CW controller 520, the CW controller 520 may additionally output a write signal WRITE <0> That is, the CW controller 520 may output the write signal WRITE<0:M> through M+1 lines L1 to LM+1.

[0135] For example, refer to Fig.12 and Fig.13 , Fig.13 The M+1 lines L1 to LM+1 of the backlight driver 3000 include the lines added to Fig.12 The M lines L1 to LM of the backlight driver 2000 transmit the write signal WRITE <0> The M+1th line LM+1 may be connected to the first pixel circuit 610_1 of each of the plurality of pixel circuit groups 600_1, 600_2, . . . and 600_N.

[0136] In addition, each of the first line L1 to the M-1th line LM-1 transmitting the write signal WRITE<1:M-1> may be additionally connected to one pixel circuit. Fig.12 and Fig.13 , Fig.12 The first line L1 is connected only to the first pixel circuit 410_1, but Fig.13 The first line L1 may be connected not only to the first pixel circuit 610_1 but also to the second pixel circuit 610_2 adjacent to the first pixel circuit 610_1. Fig.13 The second line L2 can be connected not only to the second pixel circuit 610_2, but also to the third pixel circuit adjacent to the second pixel circuit 610_2. Fig.13 The M-1th line LM-1 may be connected not only to the M-1th pixel circuit but also to the M-th pixel circuit 610_M adjacent to the M-1th pixel circuit.

[0137] In short, only one pixel circuit can be connected to transmit the write signal WRITE <0> and WRITE <m>The M+1th line and the Mth line of the pixel circuit 610_1 and the Mth line of the pixel circuit 610_2 can be connected to two adjacent pixel circuits. Accordingly, each of the pixel circuits 610_1, 610_2, ... and 610_M can receive two write signals through two lines.

[0138] According to example embodiments, the CW controller 520 may sequentially generate the write signals WRITE<0:M> to have an active level. In addition, each of the pixel circuits 610_1, 610_2, . . . and 610_M may perform a CW operation based on one write signal and perform an LDR operation based on another write signal.

[0139] For example, refer to Fig.13 , the first pixel circuit 610_1 can be based on the write signal WRITE <0> Perform LDR operation, and based on the write signal WRITE <1> In addition, the second pixel circuit 610_2 can be based on the write signal WRITE <1> Perform LDR operation, and based on the write signal WRITE <2> In addition, the M-th pixel circuit 610_M can be based on the write signal WRITE <m-1>Perform LDR operation, and based on the write signal WRITE <m>However, example embodiments are not limited thereto, and for example, the first pixel circuit 610_1 may be configured to perform a CW operation based on a write signal WRITE <0> Perform CW operation and based on the write signal WRITE <1> Perform LDR operation.

[0140] As described above, the CW controller 520 may be configured to include a write signal WRITE <0> The write signal WRITE<0:M> of the pixel circuits 610_1, 610_2, ... and 610_M sends the execution time of the LDR operation and the CW operation to the pixel circuits 610_1, 610_2, ... and 610_M. Accordingly, the pixel circuits 610_1, 610_2, ... and 610_M do not need to receive the instruction Figure 5 The enable signal EN is not used for the execution time of the LDR operation described in the embodiment, and a line for transmitting the enable signal EN to each of the pixel circuits 610_1, 610_2, . . . and 610_M may be omitted.

[0141] That is, the backlight driver 3000 can add a transmission write signal WRITE <0> A line for transmitting the enable signal EN to each of the pixel circuits 610_1, 610_2, . . . and 610_M is omitted, so that manufacturing costs can be reduced and power consumption can be reduced.

[0142] According to another example, the write signal WRITE is transmitted <0> The M+1th line LM+1 may be implemented to be connected to all pixel circuits 610_1, 610_2, ... and 610_M. That is, similar to Fig.12 In the backlight driver 2000, each of the M lines L1 to LM transmitting the write signal WRITE<1:M> may be implemented to be connected to one pixel circuit, and only the write signal WRITE<1:M> is transmitted. <0> The M+1th line LM+1 may be implemented to be connected to all pixel circuits 610_1 , 610_2 . . . and 610_M.

[0143] In this case, as mentioned above Fig.12 As described above, the CW controller 520 may generate a write signal WRITE<1:M> indicating the execution time of the CW operation of each of the pixel circuits 610_1, 610_2, ..., and 610_M, and generate a write signal WRITE<1:M> indicating the execution time of the LDR operation of the pixel circuits 610_1, 610_2, ..., and 610_M. <0> That is, the write signal WRITE <0> Can be used as above Figure 5 Accordingly, even in this case, the line that transmits the enable signal EN to each of the pixel circuits 610_1, 610_2, . . . and 610_M may be omitted.

[0144] Fig.14 is a diagram showing each frame period according to an example embodiment. Fig.13 FIG. 3 is a diagram of the operation of the backlight driver 3000 .

[0145] The backlight driver 3000 can also operate in units of frame periods. Fig.14 , the backlight driver 3000 may simultaneously perform the CW operation and the LDR operation in a frame period corresponding to the first frame FRAME 1.

[0146] Specifically, the write signals WRITE<0:M> may be sequentially generated to have an active level, and each of the plurality of pixel circuits 610_1 , 610_2 . . . , and 610_M may sequentially perform a CW operation and an LDR operation according to the corresponding write signal.

[0147] For example, refer to Fig.13 and Fig.14 , the first pixel circuit 610_1 can be configured to receive a write signal WRITE <0> The LDR operation is performed when the write signal WRITE <1> The CW operation is performed when the write signal WRITE has an effective level. <1> The LDR operation is performed when the write signal WRITE <2> Performs CW operation when has a valid level.

[0148] In addition, when the CW operation and the LDR operation of the plurality of pixel circuits 610_1 , 610_2 . . . , and 610_M are completed, the backlight driver 3000 may perform the LE operation.

[0149] When the above Fig.14 The write signal WRITE <0> When connected to all pixel circuits 610_1, 610_2, ... and 610_M, the pixel circuits 610_1, 610_2, ... and 610_M can be connected to all pixel circuits 610_1, 610_2, ... and 610_M at the write signal WRITE <0> The LDR operation is performed when the remaining write signals WRITE<1:M> have a valid level, and the CW operation is performed when the remaining write signals WRITE<1:M> sequentially have a valid level. In addition, when the CW operation of the pixel circuits 610_1, 610_2, . . . and 610_M is completed, the LE operation may be performed.

[0150] As reference Fig.14 The write signal WRITE is shown and described. <0> , write signal WRITE <1> ...and the write signal WRITE <m>The write signals WRITE<0:M> sequentially have valid levels, but example embodiments are not limited thereto and the order in which the write signals WRITE<0:M> have valid levels may be implemented in various ways.

[0151] Fig.15 is a flowchart illustrating a method of driving a backlight device 1700 according to example embodiments. Fig.15 The operation method can be Figure 1 The backlight device 1700 is used to perform.

[0152] refer to Fig.15 In the first period of the frame period, the backlight device 1700 may generate a reference current using a current source (S110). In addition, in the first period, the backlight device 1700 may convert the reference current in a time-division method using N (N is a positive integer) pixel circuits that share the current source, and store the converted reference voltage (S120). Each of the N pixel circuits may include a conversion circuit that converts the reference current into a reference voltage, and a sample-and-hold circuit that samples and stores the reference voltage.

[0153] In addition, in the second period of the frame period, the backlight device 1700 can obtain N brightness data corresponding to the N regions of the image displayed on the display panel respectively (S130). In addition, in the third period of the frame period, the backlight device 1700 can drive the LED element during the LE time corresponding to the N brightness data using the reference voltage stored in the N pixel circuits (S140).

[0154] Fig.16 is a diagram illustrating a backlight device 4000 according to example embodiments.

[0155] The backlight device 4000 may include a backlight unit 4100 and a backlight driver 4200. Figure 2 The backlight unit 1500 described in Fig.16 The backlight unit 4100 may be divided into a plurality of dimming groups, and the backlight driver 4200 may drive the backlight unit 4100 for each of the plurality of dimming groups.

[0156] In some example embodiments, the backlight driver 4200 may include a plurality of panel drivers 4210 and a plurality of pixel circuit groups 4220 to drive the backlight unit 4100 for each of the plurality of dimming groups. The panel drivers 4210 and the pixel circuit groups 4220 may correspond to Figure 3 The panel driver 100 and the pixel circuit group 200 are shown in FIG.

[0157] The backlight unit 4100 may include the same number of multiple panel drivers 4210 and multiple pixel circuit groups 4220. The multiple panel drivers 4210 and the multiple pixel circuit groups 4220 may correspond to the multiple dimming groups, respectively, and may drive the LED elements of the corresponding dimming groups. The multiple panel drivers 4210 and the multiple pixel circuit groups 4220 may be arranged adjacent to the area where the LED elements of the corresponding dimming groups are located.

[0158] For example, refer to Fig.16 , when the backlight unit 4100 is divided into dimming groups arranged in 4×4, the backlight driver 4200 may include 16 panel drivers 4210 and 16 pixel circuit groups 4220. The 16 panel drivers 4210 and the 16 pixel circuit groups 4220 may be disposed adjacent to an area where a corresponding dimming group among the 16 dimming groups is located.

[0159] Fig.17 is a diagram illustrating a backlight device 5000 according to example embodiments.

[0160] The backlight device 5000 may include a backlight unit 5100 and a backlight driver 5200. The backlight driver 5200 may drive a plurality of dimming groups of the backlight unit 5100 for each column. For example, the backlight driver 5200 may include a plurality of panel drivers 5210 and a plurality of pixel circuit groups 5220 corresponding to one or more columns of the plurality of dimming groups of the backlight unit 5100. In some example embodiments, the backlight driver 5200 may be disposed on a non-display portion of the backlight unit 5100, and may drive the LED elements through lines connected to the LED elements of the backlight unit 5100. The panel driver 5210 and the pixel circuit groups 5220 may correspond to the respective Figure 3 The panel driver 100 and the pixel circuit group 200 are shown in FIG.

[0161] For example, refer to Fig.17 , the backlight unit 5100 can be divided into dimming groups arranged in 4×4, and when the dimming groups are divided into 4 columns, the backlight driver 5200 can include 4 panel drivers 5210 and 4 pixel circuit groups 5220 corresponding to the number of columns. The 4 panel drivers 5210 and the 4 pixel circuit groups 5220 can be set in a non-display area adjacent to the corresponding columns among the 4 columns.

[0162] refer to Fig.17 , it is shown and described that the backlight driver 5200 includes a plurality of panel drivers 5210 and a plurality of pixel circuit groups 5220 corresponding to one or more columns of a plurality of dimming groups of the backlight unit 5100, but example embodiments are not limited thereto. For example, in order to drive the backlight driver 5200 for each row of a plurality of dimming groups of the backlight unit 5100, the backlight driver 5200 may include a plurality of panel drivers 5210, and a plurality of pixel circuit groups 5220 corresponding to one or more rows.

[0163] Fig.18 An example of a display device 6000 according to an example embodiment is shown. Fig.18 The display device 6000 is a device including a middle-sized display panel 6400 and can be applied to, for example, a television and a monitor.

[0164] refer to Fig.18 , the display device 6000 may include a timing controller 6100 , a source driver 6200 , a gate driver 6300 , a display panel 6400 , a backlight unit 6500 , and a backlight driver 6600 .

[0165] The timing controller 6100 may include one or more ICs or modules. The timing controller 6100 may communicate with a plurality of source driver ICs (SDICs) and a plurality of gate driver ICs (GDICs) through an interface.

[0166] The timing controller 6100 may generate a control signal for controlling driving timing of a plurality of source driver ICs (SDICs) and a plurality of gate driver ICs (GDICs), and provide the control signal to the plurality of source driver ICs (SDICs) and the plurality of gate driver ICs (GDICs).

[0167] The source driver 6200 may include a plurality of source driver ICs (SDICs), and the plurality of source driver ICs (SDICs) may be mounted on a circuit film (such as a tape carrier package (TCP), a chip on film (COF), a flexible print circuit (FPC), etc.) and attached to the display panel 6400 by using a tape automatic bonding (TAB) method, or may be mounted on a non-display area of ​​the display panel 6400 by using a chip on glass (COG) method.

[0168] The gate driver 6300 may include a plurality of gate driver ICs (GDICs), and the plurality of gate driver ICs (GDICs) may be mounted on a circuit film and attached to the display panel 6400 by using a TAB method, or may be mounted on a non-display region of the display panel 6400 by using a COG method. Alternatively, the gate driver 6300 may be directly formed on a lower substrate of the display panel 6400 by using a gate-driver in panel (GIP) method. The gate driver 6300 may be formed on a non-display region outside a pixel array of the display panel 6400 in which pixels are formed, and may be formed by the same TFT process as the pixels.

[0169] The backlight driver 6600 may correspond to the above reference Figures 1 to 17 One of the backlight drivers 1600, 2000, 3000, 4200 and 5200 described.

[0170] Fig.19 A display device 7000 according to an example embodiment is shown. Fig.19 The display device 7000 is a device including a small display panel 7200 and may be applied to mobile devices or wearable devices such as smartphones and tablet PCs.

[0171] refer to Fig.19 , the display device 7000 may include a display driving circuit 7100, a display panel 7200, and a backlight unit 7300. The display driving circuit 7100 may include one or more ICs, which may be mounted on a circuit film (such as TCP, COF, FPC, etc.) and attached to the display panel 7200 by using a TAB method, or may be mounted on a non-display area (e.g., an area where no image is displayed) of the display panel 7200 by using a COG method.

[0172] The display driving circuit 7100 may include a source driver 7110, a gate driver 7120, a backlight driver 7130, and a timing controller 7140. The backlight driver 7130 may correspond to the above reference 7140. Figures 1 to 17 One of the backlight drivers 1600, 2000, 3000, 4200 and 5200 described.

[0173] Although example embodiments have been shown and described, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.< / m> < / m> < / m> < / m> < / m> < / m>

Claims

1. A backlight device, comprising: A plurality of light emitting diode LED elements are divided into a plurality of dimming groups; a panel driver configured to output a reference current for driving the plurality of LED elements; as well as a plurality of pixel circuits, each of which is connected to the panel driver via a common line and is respectively configured to drive a first plurality of LED elements included in a corresponding dimming group among the plurality of dimming groups, Wherein, each of the plurality of pixel circuits is configured as: In a first period of a frame period, obtaining a reference voltage based on the reference current and storing the reference voltage, In a second period of the frame period, brightness data of an image displayed by a corresponding dimming group is obtained, and In a third period of the frame period, the first plurality of LED elements are driven during a light emitting time corresponding to the brightness data obtained in the second period using the reference voltage stored in the first period.

2. The backlight device according to claim 1, wherein: A first period of the frame period includes a plurality of sampling periods corresponding to the plurality of pixel circuits, respectively, and Each of the plurality of pixel circuits is configured to obtain the reference voltage in a corresponding sampling period among the plurality of sampling periods and store the reference voltage.

3. The backlight device according to claim 2, wherein: The panel driver comprises: a current source configured to output the reference current in a first period of the frame period; and a current writing controller configured to output a plurality of writing signals corresponding to the plurality of pixel circuits, respectively indicating the plurality of sampling periods, and Wherein, each of the plurality of pixel circuits is configured to obtain the reference voltage based on a corresponding write signal among the plurality of write signals.

4. The backlight device according to claim 3, wherein: Each of the plurality of pixel circuits comprises: a conversion circuit configured to obtain the reference voltage by converting the reference current into the reference voltage based on a corresponding write signal; a sample-and-hold circuit configured to store the reference voltage; and The LED driver is configured to respectively drive the first plurality of LED elements using the reference voltage stored by the sample-and-hold circuit.

5. The backlight device according to claim 4, wherein: The conversion circuit includes a delay element configured to delay a corresponding write signal, and The conversion circuit is configured to convert the reference current into the reference voltage based on a delayed write signal provided by the conversion circuit.

6. The backlight device according to claim 4, wherein: The sample-and-hold circuit comprises: a first sample-and-hold circuit; and a second sample-and-hold circuit, and Wherein, the LED driver comprises: a first LED driver configured to drive a first group of LED elements among the first plurality of LED elements based on a reference voltage stored in the first sample-and-hold circuit; and The second LED driver is configured to drive a second group of LED elements among the first plurality of LED elements based on the reference voltage stored in the second sample and hold circuit.

7. The backlight device according to claim 4, wherein: Each of the plurality of pixel circuits includes a switch circuit, wherein the switch circuit includes: a switch configured to connect the first plurality of LED elements to the LED driver; and The switch controller is configured to obtain the brightness data and control the switch circuit to drive the switch according to the light emitting time corresponding to the brightness data.

8. The backlight device according to claim 7, wherein: The brightness data includes pulse width modulation (PWM) data having a width corresponding to the brightness, and The switch controller is configured to drive the first plurality of LED elements during a light emission time corresponding to a width of the PWM data.

9. The backlight device according to claim 1, wherein: The panel driver includes a current source controller configured to control a current source to change the magnitude of the reference current, and The current source controller is configured to select the amplitude of the reference current based on the brightness data, and control the current source to output the reference current of the selected amplitude.

10. The backlight device according to claim 1, wherein: A portion of the first period overlaps with the second period.

11. The backlight device according to claim 1, wherein: A portion of the first time period overlaps with the third time period.

12. The backlight device according to claim 1, wherein: The plurality of pixel circuits are configured as follows: for each of a preset number of frame periods, sequentially obtaining the reference voltage based on the reference current in the first period and storing the reference voltage, and For each frame period, the brightness data is obtained in the second period, and in the third period, the first plurality of LED elements are driven during a light emission time corresponding to the brightness data obtained in the second period.

13. The backlight device according to claim 12, wherein: A first pixel circuit among the plurality of pixel circuits is configured to, for each of the preset number of frame periods relative to a first frame period, sequentially obtain the reference voltage based on the reference current in the first period and store the reference voltage, and Among them, a second pixel circuit among the plurality of pixel circuits is configured to sequentially obtain the reference voltage based on the reference current in the first period and store the reference voltage for each of the preset number of frame periods relative to the second frame period.

14. The backlight device according to claim 1, wherein: The plurality of pixel circuits are configured to omit an operation of obtaining the brightness data in the second period based on brightness data of a previous frame and a current frame having a common value.

15. A backlight driver configured to operate in units of a frame period including a charging period and a display period, the backlight driver comprising: a first pixel circuit configured to drive a first plurality of light emitting diode (LED) elements corresponding to a first region of the display panel; a second pixel circuit configured to drive a second plurality of LED elements corresponding to a second region of the display panel; as well as a panel driver including a current source connected in parallel with the first pixel circuit and the second pixel circuit and configured to provide a reference current to the first pixel circuit and the second pixel circuit based on the current source, Wherein, the first pixel circuit is configured as follows: In a first sampling period of the charging period, obtaining a reference voltage based on the reference current and storing the reference voltage, and In the display period, the first plurality of LED elements are driven based on first brightness data indicating brightness corresponding to the first area, and Wherein, the second pixel circuit is configured as follows: in a second sampling period of the charging period, obtaining the reference voltage based on the reference current and storing the reference voltage, and In the display period, the second plurality of LED elements are driven based on second brightness data indicating brightness corresponding to the second area.

16. The backlight driver according to claim 15, wherein: The panel driver is configured to output a first write signal indicating the first sampling period and a second write signal indicating the second sampling period, The first pixel circuit is configured to obtain the reference voltage based on the reference current according to the first write signal and store the reference voltage, and The second pixel circuit is configured to obtain the reference voltage based on the reference current according to the second write signal and store the reference voltage.

17. The backlight driver according to claim 16, wherein: Each of the first brightness data and the second brightness data includes pulse width modulation (PWM) data indicating a pulse width corresponding to brightness, wherein the first pixel circuit is configured to drive the first plurality of LED elements during a first light emission time corresponding to a first pulse width indicated by the first brightness data, and The second pixel circuit is configured to drive the second plurality of LED elements during a second light emission time corresponding to a second pulse width indicated by the second brightness data.

18. The backlight driver according to claim 15, wherein: The panel driver includes a current source controller configured to control any one or any combination of an amplitude of the reference current and a pulse width of the reference current.

19. The backlight driver according to claim 15, wherein: The first pixel circuit and the second pixel circuit are configured to obtain the reference voltage based on the reference current and store the reference voltage in the display period for each of a preset number of frame periods.

20. A method of driving a backlight device to provide illumination to a display panel, the method comprising: generating a reference current using a current source during a first period of the frame period; In the first period, using N pixel circuits that share the current source to obtain a reference voltage based on the reference current in a time division method, and storing the reference voltage in each of the N pixel circuits, wherein N is a positive integer; In a second period of the frame period, obtaining N brightness data respectively corresponding to N areas of the image displayed on the display panel; and In a third period of the frame period, the LED element is driven during a light emission time corresponding to the N luminance data using the reference voltage stored in the N pixel circuits.

Images