Low gray scale quality enhancement driving system for LED display

Abstract

This invention belongs to the field of display devices and provides a low grayscale image quality enhancement driving system for LED displays, including a timing control unit, a grayscale discrimination unit, a boundary calibration unit, a light emission duration data generation unit, a light emission amplitude data generation unit, a pixel driving array, and a light emission control unit. The boundary calibration unit determines the peak current holding boundary duration and the corresponding grayscale switching based on the current response of the light emission unit under different duration control states. The grayscale discrimination unit then divides the target grayscale data into a variable-duration grayscale subdomain and a variable-amplitude grayscale subdomain. In the variable-duration grayscale subdomain, the grayscale is expressed by changing the light emission duration while maintaining the light emission current amplitude. In the variable-amplitude grayscale subdomain, the light emission duration is maintained at the peak current holding boundary duration, and the low grayscale is expressed by adjusting the light emission current amplitude, thereby generating the corresponding cumulative light emission. This invention can improve the brightness control stability and image quality performance in low grayscale areas.

Description

Technical Field

[0001] This invention relates to the field of display devices, and more particularly to a low grayscale image quality enhancement driving system for LED displays. Background Technology

[0002] LED display technology, with its high brightness, high contrast, fast response speed, and high reliability, has been widely used in high-end displays, micro-displays, and large-size displays. As display resolution and grayscale performance requirements increase, the impact of pixel-level driving precision on image quality becomes increasingly significant. Existing display driving methods typically express different grayscale levels by changing the emission time or driving current. Emission time modulation (EPDM) is beneficial for maintaining a relatively stable current state of the light-emitting unit over a large grayscale range, thereby reducing chromatic shift caused by changes in current density. However, in low grayscale regions, to achieve lower brightness, the emission time needs to be compressed to a shorter range. At this point, factors such as thin-film transistor switching speed, current driving capability, data line load, and differences in components within the panel can affect the current of the light-emitting unit, making it difficult to reach a stable state in time. This causes the actual light emission to deviate from the ideal smooth relationship. Consequently, low grayscale displays are prone to problems such as sudden brightness changes, compression of dark areas, decreased grayscale resolution, and localized image distortion, making it difficult to meet the requirements of high-quality LED displays for dark detail and stable image output. Summary of the Invention

[0003] In view of the above technical problems, the present invention provides a low grayscale image quality enhancement driving system for LED displays, which solves the problems that existing LED displays are prone to grayscale jumps, brightness error amplification and loss of image details when expressing low grayscale due to short light emission time, insufficient current build-up, data transmission disturbances and device differences, thereby improving the brightness control stability and image quality performance in low grayscale areas.

[0004] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.

[0005] According to one aspect of the present invention, a low grayscale image quality enhancement driving system for LED displays is disclosed, applied to a display panel including light-emitting units. The driving system includes a timing control unit, a grayscale discrimination unit, a boundary calibration unit, a light emission duration data generation unit, a light emission amplitude data generation unit, a pixel driving array, and a light emission control unit. The boundary calibration unit is used to determine the peak current holding boundary duration based on the current response of the light-emitting units under different duration control states, and to form a switching grayscale corresponding to the peak current holding boundary duration. The grayscale discrimination unit is used to receive target grayscale data and divide the target grayscale data into a variable duration grayscale subdomain and a variable amplitude grayscale subdomain according to the switching grayscale. The timing control unit is used to generate a duration writing timing, an amplitude writing timing, a ramp scan control signal, and a light emission enable signal, and to make the duration writing timing act on the pixel driving array before or adjacent to the amplitude writing timing, wherein: When the target grayscale data belongs to the variable duration grayscale subdomain, the emission duration data generation unit generates duration control data that changes with the target grayscale data, the emission amplitude data generation unit generates amplitude control data for maintaining the emission current amplitude, and the pixel driving array determines the emission duration based on the duration control data and maintains the emission current amplitude based on the amplitude control data. When the target grayscale data belongs to the variable amplitude grayscale subdomain, the emission duration data generation unit fixes the duration control data to the boundary duration data corresponding to the peak current holding boundary duration, the emission amplitude data generation unit generates amplitude control data that changes with the target grayscale data, the pixel driving array maintains the emission duration at the peak current holding boundary duration according to the boundary duration data, and adjusts the emission current amplitude according to the amplitude control data; The light emission control unit is used to cause the light emission units within the same frame to generate a cumulative light emission amount corresponding to the target grayscale data according to the light emission duration and the light emission current amplitude during the light emission period of the display frame.

[0006] Furthermore, the boundary calibration unit includes a response acquisition subunit, a boundary recognition subunit, and a boundary storage subunit. The response acquisition subunit is used to apply a series of duration trial data and reference amplitude data to the detection pixel, representative pixel, or partition pixel during the calibration phase, and to acquire the luminous current rising state, peak hold state, and off state of the luminous unit. The boundary recognition subunit is used to determine the peak current hold boundary duration between a duration control state in which the luminous current can reach the target peak and remain stable and a duration control state in which the luminous current decreases as the luminous duration shortens. The boundary storage subunit is used to store the peak current hold boundary duration and the switching grayscale according to the display panel, display partition, or pixel row and column.

[0007] Furthermore, the pixel driving array includes a duration write switch, an amplitude write switch, a duration control driving device, an amplitude current driving device, an emission enable switch, a duration storage capacitor, and an amplitude storage capacitor, each corresponding to a display pixel. The duration write switch is controlled by the duration write timing to write the duration control data into the duration storage capacitor. The amplitude write switch is controlled by the amplitude write timing to write the amplitude control data into the amplitude storage capacitor. The control terminal of the duration control driving device is connected to the duration storage capacitor and changes the conduction time through the ramp scan control signal. The amplitude current driving device determines the current amplitude through the emission unit based on the amplitude control data held by the amplitude storage capacitor. The emission enable switch is controlled by the emission enable signal to allow or prohibit the emission unit from accessing the driving current path.

[0008] Furthermore, in the display frame, the timing control unit first turns on the duration write switch in scan order, and writes and holds the duration control data in the duration storage capacitor while the ramp scan control signal holds the reference potential; the timing control unit then turns on the amplitude write switch in scan order, and writes and holds the amplitude control data in the amplitude storage capacitor; after writing is completed, the timing control unit turns on the light emission period through the light emission enable signal, and causes the ramp scan control signal to act on the duration control driving device according to a predetermined trend, so that each display pixel enters a unified light emission control process after completing data holding.

[0009] Furthermore, during the emission period, the ramp scan control signal causes the control terminal potential of the duration control driver to change continuously or segmentally; when the effective bias between the control terminal and the output terminal of the duration control driver reaches the conduction condition, the duration control driver applies a power supply potential to the intermediate control node; the intermediate control node is connected to the control terminal of the amplitude current driver, and the power supply potential causes the amplitude current driver to switch to a cutoff state or a current limiting state, thereby determining the emission end time of the emission unit; within the variable amplitude grayscale subdomain, the boundary duration data fixes the emission end time at a position corresponding to the peak current holding boundary duration, and the amplitude control data changes the conduction capability of the amplitude current driver to form different cumulative emission amounts.

[0010] Furthermore, the duration write switch, the amplitude write switch, the duration control driver, the amplitude current driver, and the light emission enable switch are formed by the same active matrix thin-film transistor backplane. The active matrix thin-film transistor backplane is a polycrystalline semiconductor thin-film transistor backplane, an oxide thin-film transistor backplane, or an equivalent active matrix thin-film transistor backplane. The duration storage capacitor and the amplitude storage capacitor retain the duration control data and the amplitude control data respectively after writing, and cooperate with the ramp scan control signal and the light emission enable signal during the light emission period to complete the grayscale representation of the display frame. Furthermore, the driving system also includes a grayscale mapping unit, which is used to establish a duration mapping relationship and an amplitude mapping relationship based on the monotonic correspondence between the target grayscale data, the emission duration, the emission current amplitude, and the cumulative emission amount, respectively. The duration mapping relationship is used to maintain the emission current amplitude at the same amplitude reference within the variable duration grayscale subdomain, and to make the emission duration change with the target grayscale data. The amplitude mapping relationship is used to maintain the emission duration as the peak current holding boundary duration within the variable amplitude grayscale subdomain, and to make the emission current amplitude change with the target grayscale data. The grayscale mapping unit is also used to perform continuous calibration of the duration mapping relationship and the amplitude mapping relationship at the grayscale switching point to avoid unexpected brightness jumps between adjacent grayscale levels.

[0011] Furthermore, the emission amplitude data generation unit configures the data adjustment range corresponding to the low grayscale expression within the variable amplitude grayscale subdomain to be wider than the data adjustment range when only duration control is used, and the grayscale discrimination unit prohibits further compression of the emission duration when the target grayscale data is lower than the switching grayscale; the pixel driving array changes the emission current amplitude within the peak current holding boundary duration, so that the amplitude control data disturbance caused by data line parasitic impedance, data source transmission distortion, emission unit difference and thin film transistor threshold drift is smaller than the cumulative emission disturbance when only duration control is used.

[0012] Furthermore, the variable duration grayscale subdomain corresponds to the medium grayscale region and the high grayscale region, and the variable amplitude grayscale subdomain corresponds to the low grayscale region; the grayscale discrimination unit restricts the active adjustment of the emission current amplitude to the low grayscale region, and makes the medium grayscale region and the high grayscale region adopt the emission duration adjustment mode to maintain the current stability, so as to suppress the color shift caused by the change in current density in the grayscale region with high visual sensitivity, and expand the low grayscale brightness control margin in the grayscale region with low visual sensitivity.

[0013] The technical solution disclosed herein has the following beneficial effects: By differentiating the target grayscale areas and employing matching light-emitting control strategies in different grayscale areas, the display panel can maintain a relatively stable light-emitting current state in the mid-to-high grayscale areas, while avoiding insufficient current build-up caused by simply compressing the light-emitting time in the low grayscale areas. By converting the low grayscale expression into current amplitude adjustment based on the effective light-emitting time, the data adjustment margin corresponding to the low grayscale can be expanded, reducing the impact of data line load, signal transmission deviation, light-emitting unit differences, and thin-film transistor characteristic drift on the cumulative light emission, making the brightness change between adjacent low grayscales smoother. Therefore, this disclosure can improve the grayscale resolution and dark detail performance in the low grayscale areas, suppress brightness jumps and image distortion, while taking into account the color stability in the mid-to-high grayscale areas, thereby improving the image quality consistency and driving reliability of the LED display panel across the entire grayscale range. Attached Figure Description

[0014] Figure 1 This is a structural block diagram of a low grayscale image quality enhancement driving system for LED displays, as described in an embodiment of this specification. Figure 2 This is a circuit schematic diagram of the pixel driving array in the embodiments of this specification. Detailed Implementation

[0015] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this disclosure more comprehensive and complete, and to fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure may be practiced with one or more of the specific details omitted, or other methods, components, apparatus, steps, etc., may be employed. In other instances, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0016] Furthermore, the accompanying drawings are merely illustrative of this disclosure. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0017] In one implementation, such as Figure 1 As shown, this specification provides a low grayscale image quality enhancement driving system for LED displays, applied to a display panel containing a light-emitting unit 90. The driving system includes a timing control unit 10, a grayscale discrimination unit 20, a boundary calibration unit 30, a light emission duration data generation unit 40, a light emission amplitude data generation unit 50, a pixel driving array 60, and a light emission control unit 70. The boundary calibration unit 30 is used to determine the peak current holding boundary duration based on the current response of the light-emitting unit 90 under different duration control states, and to form a switching grayscale corresponding to the peak current holding boundary duration. The grayscale discrimination unit 20 is used to receive target grayscale data and divide the target grayscale data into a variable duration grayscale subdomain and a variable amplitude grayscale subdomain according to the switching grayscale. The timing control unit 10 is used to generate a duration writing timing, an amplitude writing timing, a ramp scan control signal, and a light emission enable signal, and to make the duration writing timing act on the pixel driving array 60 before or adjacent to the amplitude writing timing, wherein: When the target grayscale data belongs to the variable duration grayscale subdomain, the emission duration data generation unit 40 generates duration control data that changes with the target grayscale data, the emission amplitude data generation unit 50 generates amplitude control data to maintain the emission current amplitude, and the pixel driving array 60 determines the emission duration based on the duration control data and maintains the emission current amplitude based on the amplitude control data. When the target grayscale data belongs to the variable amplitude grayscale subdomain, the emission duration data generation unit 40 fixes the duration control data to the boundary duration data corresponding to the peak current holding boundary duration, the emission amplitude data generation unit 50 generates amplitude control data that changes with the target grayscale data, and the pixel driving array 60 maintains the emission duration at the peak current holding boundary duration according to the boundary duration data, and adjusts the emission current amplitude according to the amplitude control data. The light emission control unit 70 is used to cause the light emission units 90 in the same frame to generate a cumulative light emission amount corresponding to the target grayscale data according to the light emission duration and light emission current amplitude during the light emission period of the display frame.

[0018] As a supplement, the boundary calibration unit 30 includes a response acquisition subunit, a boundary recognition subunit, and a boundary storage subunit. The response acquisition subunit is used to apply a series of duration trial data and reference amplitude data to the detection pixel, representative pixel, or partition pixel during the calibration phase, and to acquire the light emission current rising state, peak hold state, and off state of the light emission unit 90. The boundary recognition subunit is used to determine the peak current hold boundary duration between the duration control state in which the light emission current can reach the target peak and remain stable and the duration control state in which the light emission current decreases as the light emission duration shortens. The boundary storage subunit is used to store the peak current hold boundary duration and the grayscale switching according to the display panel, display partition, or pixel row and column.

[0019] In this embodiment, the light-emitting unit 90 can be a micro LED light-emitting unit 90 or other LED light-emitting units 90 whose light emission is controlled by pixel driving current. The target grayscale data is used to represent the grayscale level required to be expressed by the corresponding pixel or display area in the current display frame. The peak current holding boundary duration is denoted as tp, which represents the shortest light emission duration during which the driving current of the light-emitting unit 90 can rise to the target peak and maintain relative stability when using light emission duration modulation. When the light emission duration is greater than or equal to tp, the current of the light-emitting unit 90 can remain near the target peak, and the grayscale is mainly expressed by the change in light emission duration. When the light emission duration is less than tp, affected by pixel driving capability and switching response speed, the current of the light-emitting unit 90 will decrease as the light emission duration shortens, causing a sudden change in the actual cumulative light emission relative to the ideal grayscale relationship. Therefore, the grayscale corresponding to tp is used as the switching grayscale.

[0020] The variable-duration grayscale subdomain can be understood as a grayscale range where the emission duration is not shorter than the peak current holding boundary duration. Within this grayscale range, the emission amplitude data generation unit 50 can output reference amplitude data to keep the emission current amplitude near a relatively stable target peak; the emission duration data generation unit 40 outputs different duration control data according to the target grayscale data, so that the emission unit 90 has different emission durations within the same display frame. Therefore, in medium or high grayscale displays, brightness differences can be expressed by changing the emission time, and the emission wavelength shift or color shift caused by changes in current amplitude can be reduced.

[0021] The variable amplitude grayscale subdomain can be understood as the range of lower grayscale levels below the switching grayscale level. Within this grayscale range, if the emission duration is further compressed, the current of the emission unit 90 will be turned off before it is fully established, which can easily cause the brightness change between low grayscale levels to be too abrupt. To address this, the emission duration data generation unit 40 fixes the duration control data to the boundary duration data corresponding to tp, so that the emission time that allows the current to be effectively established is still retained when displaying low grayscale levels; the emission amplitude data generation unit 50 changes the amplitude control data according to the target grayscale data, so that the emission current amplitude decreases as the target grayscale level decreases, thereby expressing the difference in low grayscale levels through the change in current amplitude.

[0022] During the calibration phase of the boundary calibration unit 30, the detection pixel, representative pixel, or pixel within the display partition in the display panel can be selected as the calibration object. Under the condition that the reference amplitude data remains unchanged, different duration trial data are applied sequentially. The response acquisition subunit acquires the current response state of the light-emitting unit 90 under each duration trial data. The current response state includes at least whether the current rise phase can reach the target peak value, whether it can maintain stability after reaching the target peak value, and whether the light emission can end during the turn-off phase. Based on the acquisition results, the boundary recognition subunit compares the duration control state where the light emission current can reach and maintain the target peak value with the duration control state where the light emission current decreases as the light emission duration shortens, and determines tp from the critical position between the two.

[0023] The boundary storage subunit can store the peak current holding time and grayscale switching according to the entire screen, partitions, or pixel rows / columns. When different display partitions or different pixel rows / columns have different current responses due to data line load, device characteristics, or manufacturing deviations, the corresponding tp and grayscale switching can be stored separately, allowing the grayscale discrimination unit 20 to call the boundary data matching the current position in subsequent display frames. Thus, the driving system can determine the low grayscale control method based on the display panel's own current build-up capability, rather than using fixed empirical switching conditions for all pixels.

[0024] Within a display frame, the timing control unit 10 generates duration write timing and amplitude write timing sequentially or adjacently, ensuring that duration control data and amplitude control data are written to the pixel drive array 60 before the start of the emission period. Subsequently, the timing control unit 10 limits the emission period through an emission enable signal and determines the emission end time in conjunction with the duration control data through a ramp scan control signal. During the emission period, the emission control unit 70 causes the corresponding emission unit 90 to generate a cumulative emission amount according to the determined emission duration and emission current amplitude. The cumulative emission amount corresponds to the target grayscale data. In this way, in the variable duration grayscale subdomain, the cumulative emission amount is mainly determined by the emission duration; in the variable amplitude grayscale subdomain, the cumulative emission amount is mainly determined by the emission current amplitude, thereby avoiding the compression of the grayscale expression range in low grayscale areas due to excessively short emission time.

[0025] In one embodiment, the pixel driving array 60 includes a duration write switch, an amplitude write switch, a duration control driving device, an amplitude current driving device, an emission enable switch, a duration storage capacitor, and an amplitude storage capacitor, all configured corresponding to the display pixels. The duration write switch is controlled by the duration write timing sequence to write duration control data into the duration storage capacitor. The amplitude write switch is controlled by the amplitude write timing sequence to write amplitude control data into the amplitude storage capacitor. The control terminal of the duration control driving device is connected to the duration storage capacitor and changes the conduction time through a ramp scan control signal. The amplitude current driving device determines the current amplitude through the emission unit 90 based on the amplitude control data held by the amplitude storage capacitor. The emission enable switch is controlled by an emission enable signal to allow or disable the emission unit 90 from accessing the driving current path.

[0026] The duration write switch, amplitude write switch, duration control driver, amplitude current driver, and light emission enable switch are formed by the same active matrix thin-film transistor backplane. The active matrix thin-film transistor backplane is a polycrystalline semiconductor thin-film transistor backplane, an oxide thin-film transistor backplane, or an equivalent active matrix thin-film transistor backplane. The duration storage capacitor and amplitude storage capacitor retain the duration control data and amplitude control data after writing, respectively, and cooperate with the ramp scan control signal and the light emission enable signal during the light emission period to complete the grayscale representation of the display frame.

[0027] Specifically, such as Figure 2 As shown, the pixel driving array 60 can employ a pixel driving structure consisting of five thin-film transistors and two storage capacitors. Specifically, Q1 corresponds to the duration write switch, Q2 corresponds to the amplitude write switch, Q3 corresponds to the duration control driving device, Q5 corresponds to the amplitude current driving device, Q4 corresponds to the light emission enable switch, C1 corresponds to the duration storage capacitor, and C2 corresponds to the amplitude storage capacitor. The light emission unit 90 is D1, which is connected in the light emission driving path formed by Q4, Q5, and the power supply terminal.

[0028] The control terminal of Q1 receives the duration write timing sequence, S1. Under the control of S1, Q1 writes the duration control data into C1. The duration control data is V1. C1 is used to hold V1 after the write is completed and to apply V1 to node A. Node A is associated with the control terminal of Q3; therefore, V1 held by C1 can serve as the potential basis for controlling the turn-on time of Q3. The ramp scan control signal is S2. S2, in conjunction with C1, changes the effective potential state of the control terminal of Q3, allowing the turn-on time of Q3 to vary with different V1 values.

[0029] The control terminal of Q2 receives the amplitude write timing, which is S3. Under the control of S3, Q2 writes the amplitude control data to C2. The amplitude control data is V2. C2 is used to hold V2 after the write is completed and to apply V2 to node B. Node B is associated with the control terminal of Q5. Therefore, V2 held by C2 can serve as the potential basis for determining the conduction capability of Q5. Q5 is connected in series in the drive current path of D1. Changes in the conduction capability of Q5 will change the amplitude of the drive current through D1.

[0030] Q3 can act as a driver related to the emission duration. Its control terminal receives V1 held by C1 through node A and is affected by changes in S2. S2 is a scanning signal used to change the effective bias of the Q3 control terminal during emission control. The conduction state of Q3 is related to its gate-source voltage V_GS and threshold voltage V_TH. When the effective bias reaches the conduction condition, Q3 controls the potential of node B. Here, V_GS represents the voltage between the Q3 control terminal and the source terminal, and V_TH represents the threshold voltage required for Q3 to transition from cutoff to conduction. Through this structure, V1 is not directly used as the current amplitude control quantity of D1, but rather forms the basis for emission duration control through the cooperation of nodes A, C1, S2, and Q3.

[0031] Q4 acts as an illumination enable switch, receiving an illumination enable signal (EMI) at its control terminal. Q4 is positioned between the power supply terminal VDD and the drive current path of D1, allowing or disabling D1 from accessing the drive current path. VDD is the drive power supply terminal, and VSS is a low-potential terminal or a reference potential terminal. When Q4 is turned on under EMI control, the drive current path of D1 is formed; when Q4 is turned off under EMI control, the illumination path of D1 is closed. Therefore, Q4 does not independently determine the grayscale value, but rather limits whether the pixel circuit is in an illumination-enabled state.

[0032] In this pixel structure, V1 and V2 enter the pixel via different write channels. V1 is written through Q1 and held at C1, primarily controlling the duration of emission; V2 is written through Q2 and held at C2, primarily controlling the amplitude of the emission current. For the variable-duration grayscale subdomain, V1 can be a variable that changes with the grayscale, while V2 can remain as the baseline amplitude data. For the variable-amplitude grayscale subdomain, V1 can be fixed as the boundary duration data corresponding to tp, while V2 can be used as a variable that changes with the grayscale. tp represents the peak current holding boundary duration corresponding to when the emission current begins to fail to maintain its peak state.

[0033] The duration write switch Q1, amplitude write switch Q2, duration control driver Q3, amplitude current driver Q5, and light-emitting enable switch Q4 can be formed on the same active matrix thin-film transistor backplane. The active matrix thin-film transistor backplane can be a polycrystalline semiconductor thin-film transistor backplane, such as a low-temperature polycrystalline silicon (LTPS) thin-film transistor backplane, or an oxide (OPS) thin-film transistor backplane, or other thin-film transistor backplanes capable of active addressing. Due to the high mobility and good stability of LPS thin-film transistors, they are suitable for the pixel drive array 60 of high-brightness LED display panels.

[0034] With the above configuration, both duration data holding paths and amplitude data holding paths are present within the same display pixel. C1 and C2 respectively handle the holding functions of V1 and V2, enabling the pixel driving array 60 to simultaneously possess emission duration control and emission current amplitude control capabilities within the same active matrix backplane. This structure provides a hardware foundation for using different driving variables for different grayscale regions and avoids insufficient data adjustment range caused by relying solely on a single path to express low grayscale levels.

[0035] In one embodiment, during a display frame, the timing control unit 10 first turns on the duration write switch in the scan sequence, and writes and holds the duration control data in the duration storage capacitor while the ramp scan control signal holds the reference potential; the timing control unit 10 then turns on the amplitude write switch in the scan sequence, and writes and holds the amplitude control data in the amplitude storage capacitor; after the writing is completed, the timing control unit 10 turns on the light emission period through the light emission enable signal, and causes the ramp scan control signal to act on the duration control driving device according to a predetermined trend, so that each display pixel enters a unified light emission control process after completing data holding.

[0036] During the emission period, the ramp scan control signal causes the control terminal potential of the duration control driver to change continuously or segmentally. When the effective bias between the control terminal and the output terminal of the duration control driver reaches the conduction condition, the duration control driver applies a power supply potential to the intermediate control node. The intermediate control node is connected to the control terminal of the amplitude current driver, and the power supply potential causes the amplitude current driver to switch to the cutoff state or the current limiting state, thereby determining the emission end time of the emission unit 90. In the variable amplitude grayscale subdomain, the boundary duration data fixes the emission end time at the position corresponding to the peak current holding boundary duration, and the amplitude control data changes the conduction capability of the amplitude current driver to form different cumulative emission amounts.

[0037] In this embodiment, the display frame may sequentially include a duration data writing stage, an amplitude data writing stage, and an emission stage. The duration writing switch is implemented by Q1, the amplitude writing switch by Q2, the duration control driver by Q3, the emission enable switch by Q4, the amplitude current driver by Q5, the duration storage capacitor by C1, and the amplitude storage capacitor by C2. The duration writing timing is S1, the amplitude writing timing is S3, the ramp scan control signal is S2, and the emission enable signal is EMI.

[0038] At the beginning of each display frame, the timing control unit 10 first controls Q1 to turn on via S1, causing the duration control data V1 to be written to C1. At this time, S2 remains at the reference potential, so that the writing process does not change the light emission control state. After Q1 is turned off, C1 holds V1 and acts on the control terminal of Q3 through node A. V1 is used to determine the turn-on time of Q3 in the subsequent light emission stage, and therefore corresponds to the control data of the light emission duration.

[0039] After the duration control data is written, the timing control unit 10 controls Q2 to turn on via S3, causing the amplitude control data V2 to be written to C2. C2 holds V2 after Q2 is turned off and acts on the control terminal of Q5 through node B. V2 is used to determine the conduction capability of Q5, and therefore corresponds to the emission current amplitude control data through D1. Thus, before entering the emission stage, the same display pixel has already completed the holding of both the emission duration control amount and the emission amplitude control amount.

[0040] During the light-emitting stage, the timing control unit 10 controls Q4 to enter a light-emitting state via EMI control, forming a conductable light-emitting drive path between VDD, Q4, Q5, D1, and VSS. Simultaneously, the potential of S2 acts on Q3 according to a predetermined trend, and together with V1 held by C1, changes the effective control state of node A on Q3. As S2 changes, the gate-source voltage V_GS of Q3 gradually approaches its threshold voltage V_TH, when V_TH is satisfied... GS >V THWhen the conduction condition is met, Q3 turns on and applies the power supply potential to node B.

[0041] Node B is an intermediate control node and is connected to the control terminal of Q5. When Q3 applies VDD to node B, the potential at the control terminal of Q5 changes, causing Q5 to switch from a state that allows drive current to flow to a cutoff state or a current-limiting state. The light-emitting current of D1 is then cut off or significantly suppressed, thus determining the end time of light emission for that display pixel in the current display frame. Therefore, the earlier Q3 turns on, the shorter the light emission duration of D1; the later Q3 turns on, the longer the light emission duration of D1.

[0042] Within the variable-duration grayscale subdomain, V1 changes with the target grayscale data, and S2 acts on each display pixel with the same changing trend during the emission phase, causing Q3 corresponding to different pixels or different grayscales to meet the conduction condition at different times, thus forming different emission termination times. At the same time, V2 can remain as the reference amplitude data, allowing Q5 to provide a relatively stable emission current amplitude during the emission duration. Therefore, D1 mainly expresses the corresponding grayscale through the change in the emission duration.

[0043] Within the variable amplitude grayscale subdomain, V1 is fixed to the boundary duration data corresponding to the peak current holding boundary duration tp, causing Q3 to conduct at the moment corresponding to tp, thus fixing the end time of D1's emission at the position of the peak current holding boundary duration. At this time, V2 changes with the target grayscale data, and the conduction capability of Q5 is controlled through node B, allowing D1 to have different emission current amplitudes within the same emission duration. Therefore, low grayscale display no longer relies on continuously shortening the emission time, but rather forms different cumulative emission amounts by changing the current amplitude while retaining the effective emission time.

[0044] Through the aforementioned display frame timing, V1 and V2 are written and held respectively before the start of the light emission phase. The light emission phase is uniformly activated by EMI, and the end time of light emission is determined by the coordination of S2, V1, C1, and Q3. The amplitude of the light emission current is determined by the coordination of V2, C2, and Q5. This timing control method enables each display pixel to enter a unified light emission control process after completing data holding, and allows for the switching and coordination of light emission duration control and light emission current amplitude control within the same pixel driver array 60.

[0045] In one embodiment, the driving system further includes a grayscale mapping unit 80. The grayscale mapping unit 80 is used to establish a duration mapping relationship and an amplitude mapping relationship based on the monotonic correspondence between the target grayscale data, the emission duration, the emission current amplitude, and the cumulative emission amount. The duration mapping relationship is used to maintain the emission current amplitude at the same amplitude reference in the variable duration grayscale subdomain and to make the emission duration change with the target grayscale data. The amplitude mapping relationship is used to keep the emission duration at the peak current holding boundary duration in the variable amplitude grayscale subdomain and to make the emission current amplitude change with the target grayscale data. The grayscale mapping unit 80 is also used to perform continuous calibration of the duration mapping relationship and the amplitude mapping relationship at the grayscale switching point to avoid unexpected brightness jumps between adjacent grayscale levels.

[0046] The emission amplitude data generation unit 50 configures the data adjustment range corresponding to the low gray level expression in the variable amplitude gray level subdomain to be wider than the data adjustment range when only duration control is used, and the gray level discrimination unit 20 prohibits further compression of the emission duration when the target gray level data is lower than the switching gray level; the pixel driving array 60 changes the emission current amplitude within the peak current holding boundary time, so that the amplitude control data disturbance caused by data line parasitic impedance, data source transmission distortion, light emission unit 90 difference and thin film transistor threshold drift is smaller than the cumulative emission disturbance when only duration control is used.

[0047] In this embodiment, the grayscale mapping unit 80 is used to convert the target grayscale data into duration control data and amplitude control data that can be executed by the pixel driving array 60. For each display pixel, the brightness formed by the light-emitting unit 90D1 within a display frame mainly depends on the amount of light emitted by its luminous current accumulated over time, and the accumulated amount of light emitted can be expressed as: ; in, This indicates the cumulative luminance of D1 within the current display frame. Indicates the duration of light emission. This represents the driving current of D1 as it changes over time during emission. The higher the target grayscale data, the greater the required cumulative emission amount; the lower the target grayscale data, the smaller the required cumulative emission amount. Therefore, the grayscale mapping unit can establish a duration mapping relationship with emission duration as the main variable and an amplitude mapping relationship with emission current amplitude as the main variable, based on the monotonic correspondence between the target grayscale data and the cumulative emission amount.

[0048] Within the variable-duration grayscale subdomain, the grayscale mapping unit 80 maintains the amplitude control data V2 in the data state corresponding to the reference amplitude, enabling Q5 to provide a relatively stable driving current amplitude during emission. Simultaneously, the grayscale mapping unit 80 causes the duration control data V1 to change with the target grayscale data, causing Q3 to reach the conduction condition at different times under the action of S2, thereby altering the emission termination time of D1. Thus, within this grayscale subdomain, the grayscale is primarily expressed through changes in the emission duration, maintaining a relatively stable current state in medium and high grayscale displays.

[0049] Within the variable amplitude grayscale subdomain, the grayscale mapping unit 80 maintains V1 at the boundary duration data corresponding to the peak current holding boundary duration tp, keeping the emission duration of D1 near tp and preventing it from further shortening with the target grayscale. Simultaneously, the grayscale mapping unit 80 causes V2 to vary with the target grayscale data, thereby altering the conduction capability of Q5 and the emission current amplitude of D1. Therefore, in low grayscale display, D1 no longer relies on further compressing the emission duration to reduce the cumulative emission amount. Instead, while retaining the emission time sufficient to effectively establish the current, different low grayscale brightness levels are achieved by changing the current amplitude.

[0050] Near the grayscale switching point, the grayscale mapping unit 80 performs continuity calibration on the duration mapping relationship and the amplitude mapping relationship, ensuring that the cumulative luminous amount corresponding to the end of the variable duration grayscale subdomain and the cumulative luminous amount corresponding to the beginning of the variable amplitude grayscale subdomain remain continuous or approximately continuous. This continuity calibration can be achieved by adjusting the changes in V1 corresponding to the boundary duration data, V2 corresponding to the reference amplitude data, and V2 at the beginning of the low grayscale, preventing sudden brightness changes between adjacent grayscale levels due to the control variable switching from luminous duration to luminous current amplitude.

[0051] In the low grayscale region, if grayscale is expressed solely by shortening the emission duration, the driving current of D1 will decrease simultaneously due to insufficient settling time. This leads to a compression of the data adjustment range corresponding to the target grayscale, and minute data disturbances caused by data line load, data source output deviation, device fluctuations, or thin-film transistor threshold drift will be amplified into significant cumulative emission error. With this implementation, the grayscale discrimination unit 20 prohibits further compression of the emission duration when the target grayscale data is lower than the switching grayscale, and the emission amplitude data generation unit 50 adjusts V2 within the emission time corresponding to tp, making the data adjustment range corresponding to the low grayscale expression wider than the data adjustment range when only duration control is used.

[0052] Since the emission duration of D1 in the low grayscale subdomain is maintained near tp, and the conduction capability of Q5 is adjusted by V2, the same data perturbation no longer corresponds to a sharp brightness change under extremely short emission time, but rather to a current amplitude change over a wider amplitude adjustment range. Thus, the perturbations to V2 caused by parasitic impedance of the data line, data source transmission distortion, individual differences in D1, and the thin-film transistor threshold drift from Q1 to Q5 are converted into smaller cumulative emission perturbations compared to using only duration control. This improves the stability of low grayscale representation and reduces dark grayscale distortion.

[0053] In one embodiment, the variable duration grayscale subdomain corresponds to the medium grayscale region and the high grayscale region, and the variable amplitude grayscale subdomain corresponds to the low grayscale region. The grayscale discrimination unit 20 restricts the active adjustment of the emission current amplitude to the low grayscale region, and makes the medium grayscale region and the high grayscale region adopt the emission duration adjustment mode to keep the current stable, so as to suppress the color shift caused by the change in current density in the grayscale region with high visual sensitivity, and expand the low grayscale brightness control margin in the grayscale region with low visual sensitivity.

[0054] In this embodiment, the grayscale discrimination unit 20 can divide the target grayscale data into a low grayscale region, a medium grayscale region, and a high grayscale region. The low grayscale region corresponds to the strain amplitude grayscale subdomain, while the medium and high grayscale regions correspond to the strain duration grayscale subdomains. The division can be based on the switching grayscale corresponding to the peak current holding boundary duration tp. When the target grayscale data is lower than the switching grayscale, it enters the low grayscale region; when the target grayscale data is not lower than the switching grayscale, it enters the medium or high grayscale region.

[0055] In the mid-grayscale and high-grayscale regions, the emission duration of the light-emitting unit 90D1 is longer than or not shorter than tp. The driving current of D1 can reach the target peak and remain relatively stable. Therefore, the grayscale discrimination unit 20 causes the emission amplitude data generation unit 50 to output the reference amplitude data, and causes the emission duration data generation unit 40 to change V1 according to the target grayscale data. Thus, Q5 provides a relatively stable current amplitude during the emission period, and D1 mainly expresses different grayscale levels through the change in emission duration. Since the LED emission wavelength is easily affected by changes in driving current density, maintaining a stable current amplitude in the mid-grayscale and high-grayscale regions can reduce wavelength and color shifts caused by changes in current density, resulting in better color consistency in the grayscale regions with high visual sensitivity.

[0056] In the low grayscale region, if the grayscale is still expressed by simply shortening the emission duration, the driving current of D1 may be turned off before reaching a stable peak value, causing both the emission duration and driving current to decrease simultaneously, resulting in excessively drastic changes in the cumulative emission amount between low grayscale levels. Therefore, when the target grayscale data is lower than the switching grayscale, the grayscale discrimination unit 20 actively adjusts the emission current amplitude within the low grayscale region and fixes V1 to the boundary duration data corresponding to tp, ensuring that D1 maintains an emission duration sufficient to establish an effective current during low grayscale display.

[0057] In the low grayscale region, the emission amplitude data generation unit 50 changes V2 according to the target grayscale data, and Q5 changes its own conduction capability according to V2, thereby adjusting the emission current amplitude through D1. In other words, the low grayscale is no longer expressed by further compressing the emission time of D1, but rather by varying the current amplitude within the emission duration corresponding to tp to form different brightness levels. Since the human eye is less sensitive to brightness and chromaticity changes in the low grayscale region than in the medium and high grayscale regions, concentrating the current amplitude variation in the low grayscale region can both expand the brightness control margin in the low grayscale region and avoid introducing significant chromaticity shifts in the medium and high grayscale regions.

[0058] By employing the aforementioned grayscale region allocation method, the driving system prioritizes ensuring stable luminous current in the mid- and high-grayscale regions to suppress chromatic shift caused by changes in current density. In the low-grayscale region, it prioritizes preventing further compression of the luminous time and expands the low-brightness expression range by adjusting the current amplitude. This approach balances color stability in the mid- and high-grayscale regions with brightness resolution in the low-grayscale regions, improving the LED display panel's performance in terms of dark detail, grayscale continuity, and overall image quality consistency.

[0059] This invention differentiates the target grayscale region and employs matching light-emitting control strategies in different grayscale regions. This allows the display panel to maintain a relatively stable light-emitting current state in the mid-to-high grayscale regions, while avoiding insufficient current build-up caused by simply compressing the light-emitting time in the low grayscale regions. By converting the low grayscale expression into current amplitude adjustment based on the effective light-emitting time, the data adjustment margin corresponding to the low grayscale can be expanded, reducing the impact of data line load, signal transmission deviation, 90° difference of light-emitting units, and thin-film transistor characteristic drift on the cumulative light emission, making the brightness change between adjacent low grayscales smoother. Therefore, this invention improves the grayscale resolution and dark detail performance in the low grayscale region, suppresses brightness jumps and image distortion, while also maintaining color stability in the mid-to-high grayscale regions, thereby improving the image quality consistency and driving reliability of the LED display panel across the entire grayscale range.

[0060] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

Claims

1. A low grayscale image quality enhancement driving system for LED displays, applied to a display panel containing light-emitting units, characterized in that, The driving system includes a timing control unit, a grayscale discrimination unit, a boundary calibration unit, a light emission duration data generation unit, a light emission amplitude data generation unit, a pixel driving array, and a light emission control unit. The boundary calibration unit determines the peak current holding boundary duration based on the current response of the light emission unit under different duration control states, and forms a switching grayscale corresponding to the peak current holding boundary duration. The grayscale discrimination unit receives target grayscale data and divides the target grayscale data into a variable duration grayscale subdomain and a variable amplitude grayscale subdomain based on the switching grayscale. The timing control unit generates a duration write timing sequence, an amplitude write timing sequence, a ramp scan control signal, and a light emission enable signal, and applies the duration write timing sequence to the pixel driving array before or adjacent to the amplitude write timing sequence. When the target grayscale data belongs to the variable duration grayscale subdomain, the emission duration data generation unit generates duration control data that changes with the target grayscale data, the emission amplitude data generation unit generates amplitude control data for maintaining the emission current amplitude, and the pixel driving array determines the emission duration based on the duration control data and maintains the emission current amplitude based on the amplitude control data. When the target grayscale data belongs to the variable amplitude grayscale subdomain, the emission duration data generation unit fixes the duration control data to the boundary duration data corresponding to the peak current holding boundary duration, the emission amplitude data generation unit generates amplitude control data that changes with the target grayscale data, the pixel driving array maintains the emission duration at the peak current holding boundary duration according to the boundary duration data, and adjusts the emission current amplitude according to the amplitude control data; The light emission control unit is used to cause the light emission units within the same frame to generate a cumulative light emission amount corresponding to the target grayscale data according to the light emission duration and the light emission current amplitude during the light emission period of the display frame.

2. The low gray scale quality enhancement driving system for LED display according to claim 1, characterized in that, The boundary calibration unit includes a response acquisition subunit, a boundary recognition subunit, and a boundary storage subunit. The response acquisition subunit is used to apply a series of duration trial data and reference amplitude data to the detection pixel, representative pixel, or partition pixel during the calibration phase, and to acquire the luminous current rising state, peak hold state, and off state of the luminous unit. The boundary recognition subunit is used to determine the peak current hold boundary duration between a duration control state in which the luminous current can reach the target peak and remain stable and a duration control state in which the luminous current decreases as the luminous duration shortens. The boundary storage subunit is used to store the peak current hold boundary duration and the switching grayscale according to the display panel, display partition, or pixel row and column. 3.The low gray scale quality enhancement driving system for LED display of claim 1, wherein, The pixel driving array includes a duration write switch, an amplitude write switch, a duration control driving device, an amplitude current driving device, an emission enable switch, a duration storage capacitor, and an amplitude storage capacitor, each corresponding to a display pixel. The duration write switch is controlled by the duration write timing to write the duration control data into the duration storage capacitor. The amplitude write switch is controlled by the amplitude write timing to write the amplitude control data into the amplitude storage capacitor. The control terminal of the duration control driving device is connected to the duration storage capacitor and changes the conduction time through the ramp scan control signal. The amplitude current driving device determines the current amplitude through the emission unit based on the amplitude control data held by the amplitude storage capacitor. The emission enable switch is controlled by the emission enable signal to allow or prohibit the emission unit from accessing the driving current path.

4. The low gray scale quality enhancement driving system for LED display according to claim 3, characterized in that, In the display frame, the timing control unit first turns on the duration write switch in scan order, and writes and holds the duration control data in the duration storage capacitor while the ramp scan control signal holds the reference potential; the timing control unit then turns on the amplitude write switch in scan order, and writes and holds the amplitude control data in the amplitude storage capacitor; after writing is completed, the timing control unit turns on the light emission period through the light emission enable signal, and causes the ramp scan control signal to act on the duration control driving device according to a predetermined trend, so that each display pixel enters a unified light emission control process after completing data holding.

5. A low grayscale image quality enhancement driving system for LED displays according to claim 3, characterized in that, During the emission period, the ramp scan control signal causes the control terminal potential of the duration control driver to change continuously or segmentally; when the effective bias between the control terminal and the output terminal of the duration control driver reaches the conduction condition, the duration control driver applies a power supply potential to the intermediate control node. The intermediate control node is connected to the control terminal of the amplitude current driving device, and the power supply potential causes the amplitude current driving device to switch to a cutoff state or a current limiting state, thereby determining the end time of the light emission of the light-emitting unit; within the variable amplitude grayscale subdomain, the boundary duration data fixes the end time of the light emission at a position corresponding to the peak current holding boundary duration, and the amplitude control data changes the conduction capability of the amplitude current driving device to form different cumulative light emission amounts.

6. A low grayscale image quality enhancement driving system for LED displays according to claim 3, characterized in that, The duration write switch, the amplitude write switch, the duration control driver, the amplitude current driver, and the light emission enable switch are formed by the same active matrix thin-film transistor backplane. The active matrix thin-film transistor backplane is a polycrystalline semiconductor thin-film transistor backplane, an oxide thin-film transistor backplane, or an equivalent active matrix thin-film transistor backplane. The duration storage capacitor and the amplitude storage capacitor retain the duration control data and the amplitude control data respectively after writing, and cooperate with the ramp scan control signal and the light emission enable signal during the light emission period to complete the grayscale representation of the display frame.

7. A low grayscale image quality enhancement driving system for LED displays according to claim 1, characterized in that, The driving system further includes a grayscale mapping unit, which is used to establish a duration mapping relationship and an amplitude mapping relationship based on the monotonic correspondence between the target grayscale data, the emission duration, the emission current amplitude, and the cumulative emission amount, respectively. The duration mapping relationship is used to maintain the amplitude of the luminous current at the same amplitude reference within the variable duration grayscale subdomain, and to make the luminous duration vary with the target grayscale data. The amplitude mapping relationship is used to maintain the emission duration as the peak current holding boundary duration within the variable amplitude grayscale subdomain, and to make the emission current amplitude change with the target grayscale data; the grayscale mapping unit is also used to continuously calibrate the duration mapping relationship and the amplitude mapping relationship at the grayscale switching point to avoid unexpected brightness jumps between adjacent grayscales.

8. A low grayscale image quality enhancement driving system for LED displays according to claim 7, characterized in that, The emission amplitude data generation unit configures the data adjustment range corresponding to the low gray level expression in the variable amplitude gray level subdomain to be wider than the data adjustment range when only duration control is used, and the gray level discrimination unit prohibits further compression of the emission duration when the target gray level data is lower than the switching gray level. The pixel driving array changes the amplitude of the luminous current within the peak current holding boundary duration, so that the amplitude control data disturbance caused by data line parasitic impedance, data source transmission distortion, light-emitting unit differences, and thin-film transistor threshold drift is smaller than the cumulative luminous amount disturbance when only duration control is used.

9. A low grayscale image quality enhancement driving system for LED displays according to claim 1, characterized in that, The variable duration grayscale subdomain corresponds to the medium grayscale region and the high grayscale region, and the variable amplitude grayscale subdomain corresponds to the low grayscale region. The grayscale discrimination unit restricts the active adjustment of the emission current amplitude to the low grayscale region, and makes the medium grayscale region and the high grayscale region adopt the emission duration adjustment mode that keeps the current stable, so as to suppress the color shift caused by the change in current density in the grayscale region with high visual sensitivity, and expand the low grayscale brightness control margin in the grayscale region with low visual sensitivity.

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