EP4310826A1 - Procédé de réglage de luminosité pour module de rétroéclairage et dispositif associé - Google Patents

Procédé de réglage de luminosité pour module de rétroéclairage et dispositif associé Download PDF

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Publication number
EP4310826A1
EP4310826A1 EP22791075.9A EP22791075A EP4310826A1 EP 4310826 A1 EP4310826 A1 EP 4310826A1 EP 22791075 A EP22791075 A EP 22791075A EP 4310826 A1 EP4310826 A1 EP 4310826A1
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EP
European Patent Office
Prior art keywords
channel
brightness
backlight module
operating current
gain
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP22791075.9A
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German (de)
English (en)
Inventor
Shixiong ZHANG
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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Publication of EP4310826A1 publication Critical patent/EP4310826A1/fr
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2077—Display of intermediate tones by a combination of two or more gradation control methods
    • G09G3/2081—Display of intermediate tones by a combination of two or more gradation control methods with combination of amplitude modulation and time modulation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G09G3/3413—Details of control of colour illumination sources
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/32—Pulse-control circuits
    • H05B45/325—Pulse-width modulation [PWM]
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0271—Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/0633—Adjustment of display parameters for control of overall brightness by amplitude modulation of the brightness of the illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/064—Adjustment of display parameters for control of overall brightness by time modulation of the brightness of the illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/0646—Modulation of illumination source brightness and image signal correlated to each other
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2360/00—Aspects of the architecture of display systems
    • G09G2360/16—Calculation or use of calculated indices related to luminance levels in display data

Definitions

  • This application relates to the field of area dimming technologies, and in particular, to a method for adjusting brightness of a backlight module and a related apparatus.
  • a liquid crystal display (Liquid Crystal Display, LCD) has advantages of a small size, low power consumption, and no radiation. Therefore, the liquid crystal display occupies an important position in the market.
  • the liquid crystal display includes a liquid crystal display panel and a backlight module.
  • the backlight module may provide a backlight source for the liquid crystal display panel, so that the liquid crystal display can implement image display.
  • the backlight module may be divided into a plurality of light emitting areas, and at least one light source is disposed in each light emitting area.
  • the light source may be a light emitting diode (light emitting diode, LED).
  • An operating current of the light source in each light emitting area may be precisely controlled by using a driver chip, to implement area dimming.
  • brightness linearity of a light source in a backlight module is poor.
  • Embodiments of this application provide a method for adjusting brightness of a backlight module and a related apparatus, to improve brightness linearity of a light source in the backlight module.
  • an embodiment of this application provides a method for adjusting brightness of a backlight module.
  • the backlight module may include at least two light sources and at least one driver chip.
  • the backlight module is divided into at least two light emitting areas, and at least one light source is disposed in each light emitting area.
  • the driver chip includes at least one channel, and the channel is configured to provide an operating current for the light source in the at least one light emitting area.
  • the brightness adjustment method may be applied to the driver chip.
  • the brightness adjustment method may include: obtaining a brightness gray-scale value of the light emitting area corresponding to each channel; and determining, based on the brightness gray-scale value corresponding to each channel and a preset threshold, a dimming mode corresponding to each channel, and determining, based on a correspondence between an operating current and a brightness gray-scale value of the channel in different dimming modes, an amplitude and a duty cycle of the operating current output by each channel, where when the brightness gray-scale value corresponding to the channel is less than the preset threshold, the dimming mode corresponding to the channel is a current dimming mode, the duty cycle of the operating current output by the channel remains unchanged, and the amplitude of the operating current output by the channel is positively correlated with the brightness gray-scale value; or when the brightness gray-scale value corresponding to the channel is greater than the preset threshold, the dimming mode corresponding to the channel is a pulse width modulation (pulse width modulation,
  • the dimming mode corresponding to each channel may be determined based on the obtained brightness gray-scale value corresponding to each channel and the preset threshold, and the amplitude and the duty cycle of the operating current output by each channel may be determined based on the correspondence between the operating current and the brightness gray-scale value of each channel in different dimming modes, so that area dimming of the backlight module can be implemented.
  • the dimming mode corresponding to the channel is the current adjustment mode.
  • the current adjustment mode is used in a low gray scale, the duty cycle of the operating current remains unchanged, and brightness of the backlight module is adjusted by changing the amplitude of the operating current.
  • the dimming mode corresponding to the channel is the PWM dimming mode.
  • the PWM dimming mode is used in a high gray scale scenario, the amplitude of the operating current remains unchanged, and brightness of the backlight module is adjusted by changing the duty cycle of the operating current.
  • the brightness linearity of the backlight module in the high gray scale is high.
  • color stability of the backlight module can also be ensured by using the PWM dimming mode in the high gray scale. Therefore, according to the brightness adjustment method provided in this embodiment of this application, the brightness linearity of the backlight module in a full gray scale can be high.
  • the duty cycle of the operating current output by the channel is determined in the following manner: When the dimming mode corresponding to the channel is the current dimming mode, the duty cycle of the operating current output by the channel is a ratio of the preset threshold to a maximum gray-scale value of the backlight module; or when the dimming mode corresponding to the channel is the PWM dimming mode, the duty cycle of the operating current output by the channel is a ratio of the brightness gray-scale value corresponding to the channel to a maximum gray-scale value of the backlight module.
  • the duty cycle of the operating current is in a linear relationship with the brightness gray-scale value.
  • the corresponding brightness gray-scale value is the maximum gray-scale value of the backlight module. Therefore, the duty cycle of the operating current output by the channel is the ratio of the brightness gray-scale value corresponding to the channel to the maximum gray-scale value of the backlight module.
  • the maximum gray-scale value of the backlight module may be set based on a light emitting capability of the backlight module. For example, currently, the maximum gray-scale value of the backlight module is 4095, and a specific value of the maximum gray-scale value of the backlight module is not limited herein.
  • the duty cycle of the operating current In the current dimming mode, the duty cycle of the operating current remains unchanged with a change of the brightness gray-scale value. Therefore, in the current dimming mode, the duty cycle of the operating current is a duty cycle corresponding to the preset threshold Th. In other words, the duty cycle of the operating current output by the channel is the ratio of the preset threshold to the maximum gray-scale value of the backlight module.
  • the amplitude of the operating current output by the channel is determined in the following manner: determining, based on the brightness gray-scale value and the dimming mode that correspond to the channel, a hybrid dimming current gain corresponding to the channel; and determining, based on the determined hybrid dimming current gain corresponding to the channel, and a preset reference current and a preset global current gain that correspond to the driver chip, the amplitude of the operating current output by the channel.
  • the amplitude of the operating current increases with an increase of the brightness gray-scale value.
  • the amplitude of the operating current is a fixed value. In other words, in different dimming modes, a correspondence between the amplitude of the operating current and the brightness gray-scale value is different. Therefore, in this embodiment of this application, a parameter of the hybrid dimming current gain is used to distinguish the correspondence between the amplitude of the operating current and the brightness gray-scale value in different dimming modes.
  • the hybrid dimming current gain is related to the brightness gray-scale value and the dimming mode that correspond to the channel.
  • the hybrid dimming current gain is determined in the following manner: When the dimming mode corresponding to the channel is the current dimming mode, the hybrid dimming current gain is a ratio of the brightness gray-scale value to the preset threshold; or when the dimming mode corresponding to the channel is the PWM dimming mode, the hybrid dimming current gain is 1.
  • a local current gain corresponding to each channel is set to adjust the brightness of different light emitting areas.
  • the determining, based on the determined hybrid dimming current gain corresponding to the channel, and a preset reference current and a preset global current gain of the driver chip, the amplitude of the operating current output by the channel may include: determining, based on the determined hybrid dimming current gain corresponding to the channel, the preset reference current and the preset global current gain corresponding to the driver chip, and the preset local current gain corresponding to the channel, the amplitude of the operating current output by the channel. Local current gains corresponding to different channels may be different.
  • the local current gain corresponding to the channel may be set, so that the amplitude of the operating current output by the channel floats in a specific range, for example, may float in a range of ⁇ S%, where S>0.
  • the local current gain is in a range of 0 to (2 p -1), p is a quantity of bits occupied by the local current gain, and p is a positive integer.
  • a value of p may be determined based on a specification of the driver chip. For example, p may be 6. Certainly, p may alternatively be another value. This is not limited herein.
  • a plurality of registers corresponding to each channel may be disposed in the driver chip, and the local current gain corresponding to each channel is stored in a corresponding register.
  • the local current gain corresponding to each channel is set, so that brightness uniformity of the light emitting areas in the backlight module can be improved, so that in a scenario in which the liquid crystal display displays a pure-color image or a large dynamic video, uniformity of a display image is good, and a display effect is improved.
  • the local current gain corresponding to each channel may be determined by using a method for calibrating brightness uniformity of a backlight module.
  • the method for calibrating brightness uniformity may be executed in a test process before the backlight module is delivered from a factory, and the brightness calibration method may be executed in an external test device.
  • the method for calibrating brightness uniformity of a backlight module in this embodiment of this application may include: setting the local current gain corresponding to each channel to a same initial value, and powering on the backlight module, to light each light source in the backlight module; collecting brightness of each light emitting area in the backlight module; determining whether brightness uniformity of the backlight module is greater than a first threshold, and if the brightness uniformity of the backlight module is greater than the first threshold, adjusting the local current gain corresponding to each channel, or if the brightness uniformity of the backlight module is not greater than the first threshold, discarding the backlight module whose brightness uniformity is less than the first threshold; after the local current gain corresponding to each channel is adjusted, powering on the backlight module again, to light each light source in the backlight module; collecting the brightness of each light emitting area in the backlight module; and determining whether the brightness uniformity of the backlight module is greater than a second threshold, where the second threshold is greater than the first threshold, and if the brightness uniformity of the backlight module
  • an adjusted local current gain corresponding to each channel is solidified into a non-volatile memory in the driver chip.
  • the driver chip each time the driver chip is powered on, parameters such as the global current gain and the local current gain corresponding to each channel are directly invoked.
  • the driver chip only needs to obtain a brightness gray-scale value sent by a controller, to control each channel to output the operating current.
  • a control manner is simple.
  • the adjusting the local current gain corresponding to each channel includes: using an average brightness value of the light emitting areas in the backlight module as a target brightness value, and adjusting, based on the target brightness value, the local current gain corresponding to each channel.
  • the average brightness value of the light emitting areas is used as the target brightness value.
  • the local current gain may be adjusted in a range of ⁇ S%, and an adjustment range of the local current gain may be narrowed, to reduce an amplitude change of the operating current, and avoid an excessively large color and brightness change of the light emitting area caused by an excessively large amplitude change of the operating current.
  • an embodiment of this application further provides a driver chip.
  • the driver chip includes at least one channel, and the channel is configured to provide an operating current for a light source in at least one light emitting area of a backlight module.
  • the driver chip provided in this embodiment of this application may further include a memory and a processor.
  • the memory stores program instructions.
  • the processor is configured to invoke the program instructions stored in the memory, and execute the procedure of the foregoing brightness adjustment method based on an obtained program. Details are not described herein again.
  • an embodiment of this application further provides a backlight module.
  • the backlight module includes at least two light emitting areas, a backlight board, at least two light sources fastened on the backlight board, and the foregoing driver chip. At least one light source is disposed in each light emitting area.
  • the driver chip is electrically connected to the backlight board, the driver chip includes at least one channel, and the channel is configured to provide an operating current for the light source in the at least one light emitting area.
  • an embodiment of this application further provides a display apparatus.
  • the display apparatus includes a liquid crystal display panel and the foregoing backlight module, and the backlight module is located on a light inlet side of the liquid crystal display panel.
  • an embodiment of this application further provides a storage medium.
  • the storage medium stores computer-executable instructions, and the computer-executable instruction are used to enable a computer to perform the foregoing brightness adjustment method.
  • a backlight module is mainly used in a liquid crystal display. Because a liquid crystal display panel does not emit light, the backlight module needs to be disposed on a light inlet side of the liquid crystal display panel, to provide a backlight source for the liquid crystal display panel, so that the liquid crystal display implements image display.
  • the backlight module is usually divided into at least two light emitting areas, and at least one light source is disposed in each light emitting area. Brightness of each light emitting area in the backlight module may be adjusted based on a to-be-displayed image, so that a brighter area in the displayed image has higher brightness, and a darker area has lower brightness. In this way, the display contrast of the liquid crystal display is high.
  • FIG. 1 is a schematic diagram of a relationship between an operating current and brightness of duty cycle dimming.
  • a horizontal coordinate represents brightness
  • a vertical coordinate represents an operating current of a light source
  • a pulse width of the operating current represents a duty cycle of the operating current.
  • an amplitude of the operating current is constant, and brightness of the light source is adjusted by changing the duty cycle of the operating current.
  • a lower duty cycle of the operating current indicates lower brightness, and a higher duty cycle of the operating current indicates higher brightness.
  • the backlight module is dimming in a duty cycle dimming manner, so that the amplitude of the operating current of the light source can be constant, and color consistency of light sources is good.
  • FIG. 2 is a schematic diagram of impact of rise time and fall time of an operating current on a pulse waveform.
  • (1) in FIG. 2 is an ideal pulse waveform of the operating current.
  • a square wave is used as an example in the figure.
  • (2 ) in FIG. 2 is an actual pulse waveform of the operating current. Due to impact of the rise time Tr and the fall time Tf of the operating current, the actual pulse waveform of (2) in FIG. 2 becomes a trapezoid. It can be obviously seen from comparison between (1) and (2) in FIG.
  • the rise time Tr and the fall time Tf of the operating current affect the pulse width of the operating current, so that the duty cycle of the operating current is reduced, thereby affecting the brightness of the light source, and causing poor brightness linearity of the light source.
  • the pulse width of the operating current is narrower in a low gray scale, and the rise time Tr and the fall time Tf of the operating current have more obvious impact on the pulse width, so that brightness linearity of the light source in the low gray scale is worse.
  • the rise time Tr and the fall time Tf of the operating current cannot be avoided due to impact of a physical wiring, a parasitic capacitance, a driving capability of a driver chip, and the like in the backlight module.
  • the backlight module may be used in a liquid crystal display apparatus.
  • the backlight module is disposed on a light inlet side of a liquid crystal display panel, to provide a backlight source for the liquid crystal display panel, so that the liquid crystal display apparatus can implement image display.
  • orientation or location relationships indicated by terms “center”, “above”, “below”, “left”, “right”, “vertical”, “horizontal”, “inner”, “outer”, and the like are orientation or location relationships based on the accompanying drawings, and are merely intended for conveniently describing this application and simplifying descriptions, rather than indicating or implying that an apparatus or an element in question needs to have a specific orientation or needs to be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on this application.
  • terms “first” and “second” are merely used for a purpose of description, and cannot be construed as an indication or implication of relative importance.
  • mount should be understood in a broad sense.
  • the terms may indicate a fastened connection, a detachable connection, or an integral connection; may be a mechanical connection or an electrical connection; or may be direct interconnection, indirect interconnection through an intermediate medium, or communication between the interior of two elements.
  • An ordinary person skilled in the art may understand specific meanings of the foregoing terms in this application based on a specific situation.
  • FIG. 3 is a schematic diagram of a structure of a backlight module according to an embodiment of this application.
  • the backlight module may be a direct type backlight module.
  • the backlight module may include at least one backlight board 101, at least two light sources 102, at least one driver chip 103, and at least one controller 104.
  • the backlight module may include one backlight board 101, or the backlight module may include at least two backlight boards 101 that are spliced with each other.
  • Each light source 102 in the backlight module is fastened on the backlight board 101, the backlight module is divided into at least two light emitting areas C, and at least one light source 102 is disposed in each light emitting area C.
  • the light source 102 may be a micro light emitting diode (mini LED). Certainly, the light source 102 may alternatively be another type of light emitting component. This is not limited herein.
  • the light emitting areas C in the backlight module may be evenly distributed, or may be unevenly distributed.
  • the light emitting areas C in the backlight module may be divided according to an actual requirement. This is not limited herein.
  • a box in an upper left corner in FIG. 3 is a partial enlarged schematic diagram of a light emitting area C. When a plurality of light sources 102 are disposed in the light emitting area C, the plurality of light sources 102 may be electrically connected in a multi-serial multi-parallel manner.
  • Driver chips 103 in the backlight module are electrically connected to the backlight board 101, the driver chips 103 are sequentially connected in series, and the controller 104 is electrically connected to the driver chips 103.
  • the driver chip 103 includes at least one channel, for example, CH1, CH2, ..., and CHn in the figure. In this embodiment of this application, the channel may be an output port of the driver chip 103, and each channel corresponds to at least one light emitting area C.
  • the controller 104 is configured to provide a brightness gray-scale value required by each light emitting area C for the driver chip 103, and the channel is configured to provide an operating current for a light source 102 in a corresponding light emitting area C. In this way, the driver chip 103 precisely controls the operating current of the light source 102 in each light emitting area C, to implement area dimming.
  • FIG. 4 is a schematic flowchart of a method for adjusting brightness of a backlight module according to an embodiment of this application. The method may be applied to the system architecture shown in FIG. 3 . As shown in FIG. 4 , the brightness adjustment method provided in this embodiment of this application may be applied to any driver chip shown in FIG. 3 , and specifically includes:
  • the dimming mode corresponding to each channel may be determined based on the obtained brightness gray-scale value corresponding to each channel and the preset threshold, and the amplitude and the duty cycle of the operating current output by each channel may be determined based on the correspondence between the operating current and the brightness gray-scale value of each channel in different dimming modes, so that area dimming of the backlight module can be implemented.
  • the dimming mode corresponding to the channel is the current adjustment mode.
  • the current adjustment mode is used in a low gray scale, the duty cycle of the operating current remains unchanged, and brightness of the backlight module is adjusted by changing the amplitude of the operating current.
  • the dimming mode corresponding to the channel is the PWM dimming mode.
  • the PWM dimming mode is used in a high gray scale scenario, the amplitude of the operating current remains unchanged, and brightness of the backlight module is adjusted by changing the duty cycle of the operating current.
  • the brightness linearity of the backlight module in the high gray scale is high.
  • color stability of the backlight module can also be ensured by using the PWM dimming mode in the high gray scale. Therefore, according to the brightness adjustment method provided in this embodiment of this application, the brightness linearity of the backlight module in a full gray scale can be high.
  • step S201 the brightness gray-scale value of the light emitting area C corresponding to each channel obtained by the driver chip 103 is determined based on a display gray-scale value of each area in a to-be-displayed image of a screen.
  • the controller 104 may determine, based on the to-be-displayed image of the screen, a brightness gray-scale value required by a light emitting area corresponding to each channel, and send the determined brightness gray-scale value corresponding to each channel to a corresponding driver chip 103.
  • the to-be-displayed image of the screen is an image in which a central area is bright and a surrounding area is dark, a brightness gray-scale value required by a light emitting area corresponding to the central area is high, and a brightness gray-scale value required by a light emitting area corresponding to the surrounding area is low.
  • the backlight module may perform brightness adjustment based on the to-be-displayed image of the screen, so that in a displayed image after brightness adjustment, a brighter area has higher brightness, and a darker area has lower brightness. In this way, a display contrast is improved.
  • the display gray-scale value of the to-be-displayed image is different from the brightness gray-scale value of the backlight module.
  • the display gray-scale value of the to-be-displayed image is usually in a range of 0 to 255, and when the brightness gray-scale value occupies 12 bits, the brightness gray-scale value of the backlight module is usually in a range of 0 to 4095.
  • the controller 104 may convert the display gray-scale value of the to-be-displayed image into the brightness gray-scale value required by each light emitting area in the backlight module based on a correspondence between the display gray-scale value of the to-be-displayed image and the brightness gray-scale value of the backlight module.
  • a specific value of the preset threshold Th may be determined based on an actual requirement. For example, a critical value at which brightness linearity of the backlight module in the related technology significantly decreases may be used as the preset threshold Th.
  • the preset threshold Th may be 128.
  • the preset threshold may also be another value. This is not limited herein.
  • FIG. 6 is a schematic diagram of another relationship between an operating current and a brightness gray-scale value according to an embodiment of this application.
  • a horizontal coordinate represents a brightness gray-scale value
  • a vertical coordinate represents an operating current.
  • a curve L1 in the figure represents a curve of a relationship between a duty cycle of an operating current and a brightness gray-scale value.
  • the duty cycle of the operating current is a fixed value.
  • the duty cycle of the operating current is positively correlated with the brightness gray-scale value. In other words, the duty cycle of the operating current increases with an increase of the brightness gray-scale value.
  • a curve L2 represents a curve of a relationship between an amplitude of an operating current and a brightness gray-scale value.
  • the amplitude of the operating current is positively correlated with the brightness gray-scale value.
  • the amplitude of the operating current increases with an increase of the brightness gray-scale value.
  • the amplitude of the operating current is a fixed value.
  • a duty cycle of the operating current output by the channel may be determined in the following manner:
  • the duty cycle of the operating current is in a linear relationship with the brightness gray-scale value.
  • the corresponding brightness gray-scale value is the maximum gray-scale value of the backlight module. Therefore, it can be obtained based on the curve L1 that the duty cycle of the operating current output by the channel is the ratio of the brightness gray-scale value corresponding to the channel to the maximum gray-scale value of the backlight module.
  • the maximum gray-scale value of the backlight module may be set based on a light emitting capability of the backlight module.
  • the maximum gray-scale value of the backlight module is 4095, and a specific value of the maximum gray-scale value of the backlight module is not limited herein.
  • the duty cycle of the operating current remains unchanged with a change of the brightness gray-scale value. Therefore, in the current dimming mode, the duty cycle of the operating current is a duty cycle corresponding to the preset threshold Th.
  • the duty cycle of the operating current output by the channel is the ratio of the preset threshold to the maximum gray-scale value of the backlight module.
  • the amplitude of the operating current output by the channel may be determined in the following manner:
  • the amplitude of the operating current increases with an increase of the brightness gray-scale value.
  • the amplitude of the operating current is a fixed value. In other words, in different dimming modes, a correspondence between the amplitude of the operating current and the brightness gray-scale value is different. Therefore, in this embodiment of this application, a parameter of the hybrid dimming current gain is used to distinguish the correspondence between the amplitude of the operating current and the brightness gray-scale value in different dimming modes.
  • the hybrid dimming current gain is related to the brightness gray-scale value and the dimming mode that correspond to the channel.
  • FIG. 7 is a schematic diagram of controlling an operating current according to an embodiment of this application.
  • a reference current I ref corresponding to a driver chip may be understood as a current source of the driver chip.
  • the reference current I ref may be set by using an external resistor of the driver chip.
  • the current source may be set in another manner.
  • the current source may be adjusted by using an internal parameter of the chip, or an externally provided current source may be used.
  • a specific setting manner of the current source is not limited herein.
  • the global current gain Gain 1 is a global variable. In other words, values of the global current gain Gain 1 corresponding to channels in the driver chip are the same.
  • a meaning of the global current gain Gain 1 is to amplify the reference current I ref , to adjust overall brightness of the backlight module.
  • a value of the global current gain Gain 1 is greater than 1.
  • the global current gain Gain 1 is 1000, it indicates that the reference current I ref is amplified by 1000 times.
  • the meaning of the global current gain Gaini may alternatively be to reduce the reference current I ref .
  • the value of the global current gain Gaini may alternatively be less than 1. This is not limited herein.
  • the global current gain Gaini may be stored in a register inside the driver chip.
  • the global current gain Gaini may occupy m bits, and m is a positive integer.
  • a size of a position occupied by the global current gain Gaini may be set based on an actual requirement. This is not limited herein.
  • Gain 3 in the figure represents a hybrid dimming current gain. Because different channels may correspond to different brightness gray-scale values and different dimming modes, different channels may correspond to different hybrid dimming current gains Gain 3 .
  • the amplitude I ch of the operating current output by the channel may be determined, and the amplitude I ch of the operating current output by the channel is in a range of 0 to I max , where I max is a maximum amplitude value of the operating current.
  • the maximum amplitude value I max of the operating current output by the channel may be determined based on a performance parameter of the light source, to prevent the light source from being burnt due to an excessively large amplitude I ch of the operating current.
  • the foregoing hybrid dimming current gain may be determined in the following manner:
  • the amplitude of the operating current is in a linear relationship with the brightness gray-scale value
  • the amplitude of the operating current is a fixed value.
  • values of the foregoing hybrid dimming current gain are different in different dimming modes.
  • the hybrid dimming current gain is a ratio of the brightness gray-scale value to the preset threshold. In this way, the amplitude of the operating current may be in a linear relationship with the brightness gray-scale value.
  • the hybrid dimming current gain is a fixed value 1, so that the amplitude of the operating current can be a fixed value. Therefore, in this embodiment of this application, the parameter of the hybrid dimming current gain is set, so that the amplitude of the operating current output by the channel meets a trend shown by the curve S2 in FIG. 6 .
  • a local current gain corresponding to each channel is set to adjust the brightness of different light emitting areas.
  • the determining, based on the determined hybrid dimming current gain corresponding to the channel, and a preset reference current and a preset global current gain of the driver chip, the amplitude of the operating current output by the channel may include the following.
  • the amplitude of the operating current output by the channel is determined based on the determined hybrid dimming current gain Gain 3 corresponding to the channel, the preset reference current I ref and global current gain Gaini corresponding to the driver chip, and the preset local current gain Gain 2 corresponding to the channel.
  • Local current gains Gain 2 corresponding to different channels may be different. Therefore, a local current gain Gain 2 corresponding to a channel may be set, so that the amplitude I ch of the operating current output by the channel floats in a specific range, for example, may float in a range of ⁇ S%, where S>0.
  • the local current gain Gain 2 is in a range of 0 to (2 p -1), p is a quantity of bits occupied by the local current gain Gain 2 , and p is a positive integer.
  • a value of p may be determined based on a specification of the driver chip. For example, p may be 6. Certainly, p may alternatively be another value. This is not limited herein.
  • a plurality of registers corresponding to each channel may be disposed in the driver chip, and the local current gain Gain 2 corresponding to each channel is stored in a corresponding register.
  • a value range of the local current gain Gain 2 is 0 to (2 p -1), and may correspond to an adjustment range of the amplitude of the operating current: 1-S% to 1+S%.
  • the local current gain Gain 2 corresponding to each channel may be determined based on a brightness difference between different light emitting areas.
  • the local current gain corresponding to each channel is set, so that brightness uniformity of the light emitting areas in the backlight module can be improved, so that in a scenario in which the liquid crystal display displays a pure-color image or a large dynamic video, uniformity of a display image is good, and a display effect is improved.
  • FIG. 8 is a schematic diagram of a control architecture of an operating current according to an embodiment of this application.
  • Both the reference current I ref and the global current gain Gaini are preset global variables.
  • a reference current I ref corresponding to each channel is the same, and a global current Gaini corresponding to each channel is the same.
  • the local current gain Gain 2 is a local adjustment variable used to adjust brightness of different light emitting areas, and may be determined based on a brightness difference between different light emitting areas. Therefore, local current gains Gain 2 corresponding to different channels may be different.
  • the hybrid dimming current gain Gain 3 is used to distinguish different dimming modes, and is determined by a brightness gray-scale value corresponding to a channel and a preset threshold. Therefore, hybrid dimming current gains Gain 3 corresponding to different channels may also be different. Amplitudes Ich 1 , Ich 2 ..., Ich n of operating currents of channels may be determined based on the reference current I ref , the global current gain Gain 1 , the local current gain Gain 2 , and the hybrid dimming current gain Gain 3 .
  • FIG. 9 is a schematic diagram of an operating principle of the processor according to an embodiment of this application.
  • the processor 1031 obtains a brightness gray-scale value required by a light emitting area corresponding to each channel, the processor 1031 invokes a global current gain Gain 1 stored in a register and a local current gain Gain 2 corresponding to each channel, and the processor 1031 determines a dimming mode corresponding to each channel based on the brightness gray-scale value corresponding to each channel and the preset threshold, to determine a hybrid dimming current gain Gain 3 corresponding to each channel. Then, the processor 1031 determines and outputs a duty cycle and an amplitude of an operating current corresponding to each channel.
  • the local current gain corresponding to each channel may be determined by using a method for calibrating brightness uniformity of a backlight module.
  • the method for calibrating brightness uniformity may be executed in a test process before the backlight module is delivered from a factory, and the brightness calibration method may be executed in an external test device.
  • FIG. 10 is a schematic flowchart of a method for calibrating brightness uniformity of a backlight module according to an embodiment of this application. As shown in FIG. 10 , the method for calibrating brightness uniformity of a backlight module in this embodiment of this application may include the following steps.
  • S301 Set a local current gain corresponding to each channel to a same initial value, for example, the initial value may be 0, and certainly, the initial value may alternatively be another value. This is not limited herein.
  • S302 Power on a backlight module, to light each light source in the backlight module.
  • S303 Collect brightness of each light emitting area in the backlight module.
  • a camera may be used to photograph the backlight module, to identify the brightness of each light emitting area in the backlight module.
  • step S304 Determine whether brightness uniformity of the backlight module is greater than a first threshold a%, where a>0; and if the brightness uniformity of the backlight module is greater than the first threshold a%, perform step S306; or if the brightness uniformity of the backlight module is not greater than the first threshold a%, perform step S305.
  • whether the brightness uniformity of the backlight module can be calibrated by adjusting a local current gain may be determined by determining whether the brightness uniformity of the backlight module is greater than a%. If the brightness uniformity of the backlight module is less than a%, the backlight module may have a disadvantage, and it is difficult to calibrate by adjusting the local current gain.
  • a backlight module whose brightness uniformity is less than a% is discarded, and a local current gain corresponding to a backlight module whose brightness uniformity is greater than a% is adjusted.
  • S305 Discard the backlight module whose brightness uniformity is less than the first threshold a%.
  • S306 Adjust the local current gain corresponding to each channel. Specifically, obtain a brightness average value of light emitting areas in the backlight module, use the brightness average value of the light emitting areas in the backlight module as a target brightness value, adjust the local current gain corresponding to each channel based on the target brightness value, and then write the adjusted local current gain corresponding to each channel into a non-volatile memory inside the driver chip, where the local current gains corresponding to the channels may be different.
  • the average brightness value of the light emitting areas is used as the target brightness value.
  • the local current gain may be adjusted in a range of ⁇ S%, and an adjustment range of the local current gain may be narrowed, to reduce an amplitude change of the operating current, and avoid an excessively large color and brightness change of the light emitting area caused by an excessively large amplitude change of the operating current.
  • S307 Power on the backlight module, to light each light source in the backlight module.
  • S308 Collect the brightness of each light emitting area in the backlight module.
  • the camera may be used to photograph the backlight module, to identify the brightness of each light emitting area in the backlight module.
  • S309 Determine whether the brightness uniformity of the backlight module is greater than a second threshold b%, where the second threshold is greater than the first threshold, that is, b%>a%, for example, b may be 95; and if the brightness uniformity of the backlight module is greater than the second threshold b%, perform step S310; or if the brightness uniformity of the backlight module is not greater than the second threshold b%, return to step S306.
  • whether the backlight module meets a brightness uniformity requirement may be determined by determining whether the brightness uniformity of the backlight module is greater than b%.
  • brightness uniformity calibration of the backlight module is completed. If the brightness uniformity of the backlight module does not meet the brightness uniformity requirement, the local current gain corresponding to each channel continues to be adjusted until the backlight module meets the brightness uniformity requirement.
  • an adjusted local current gain corresponding to each channel is solidified into the non-volatile memory in the driver chip.
  • the driver chip only needs to obtain a brightness gray-scale value sent by a controller, to control each channel to output the operating current.
  • a control manner is simple.
  • FIG. 11(1) to FIG. 11(3) are a schematic diagram of comparison between brightness uniformity of a backlight module before calibration and that of the backlight module after calibration.
  • FIG. 11(1) is brightness data of each light emitting area in the backlight module before calibration
  • FIG. 11(2) is a local current gain corresponding to each channel after adjustment
  • FIG. 11(3) is brightness data of each light emitting area in the backlight module after calibration.
  • the brightness uniformity of the backlight module before calibration is approximately 82.9%, and an area enclosed by a dashed line in the figure is an area with poor brightness uniformity.
  • the brightness uniformity of the backlight module after calibration is approximately 97.2%.
  • FIG. 11(1) to FIG. 11(3) can prove that the brightness adjustment method provided in this embodiment of this application can better improve the brightness uniformity of the backlight module.
  • FIG. 12 is a schematic diagram of comparison between brightness linearity of a backlight module in a related technology and that of a backlight module in an embodiment of this application.
  • (1) in FIG. 12 is a brightness linearity curve of a backlight module obtained in a related technology by using only a PWM dimming manner.
  • (2) in FIG. 12 is a brightness linearity curve of a backlight module obtained in a hybrid dimming manner in this embodiment of this application.
  • a horizontal coordinate represents a brightness gray-scale value
  • a vertical coordinate represents a brightness value.
  • the brightness linearity of the backlight module is obviously improved.
  • the hybrid dimming manner is used, the brightness linearity of the backlight module is high.
  • a lower right corner is a schematic diagram of a pulse of an operating current according to an embodiment of this application.
  • a dashed line represents an ideal waveform of the operating current
  • a solid line represents an actual waveform of the operating current.
  • duty cycle adjustment is performed in a high gray scale, and the brightness of the backlight module is adjusted by changing the duty cycle of the operating current. In this case, the duty cycle of the operating current is large, and a difference between the actual waveform and the ideal waveform of the operating current is small.
  • an embodiment of this application further provides a driver chip.
  • the driver chip includes at least one channel, and the channel is configured to provide an operating current for a light source in at least one light emitting area of a backlight module.
  • the driver chip provided in this embodiment of this application may further include a memory and a processor.
  • the memory stores program instructions.
  • the processor is configured to invoke the program instructions stored in the memory, and execute the method procedure shown in FIG. 4 or FIG. 10 based on an obtained program. Details are not described herein again.
  • the backlight module may include at least two light emitting areas C, a backlight board 101, at least two light sources 102 fastened on the backlight board 101, and at least one driver chip 103. At least one light source 102 is disposed in each light emitting area C.
  • the driver chips 103 are electrically connected to the backlight board 101.
  • the driver chip 103 includes at least one channel, for example, CH1, CH2, ..., and CHn in the figure. The channel is configured to provide an operating current for the light source 102 in the at least one light emitting area C.
  • an embodiment of this application further provides a display apparatus.
  • the display apparatus includes a liquid crystal display panel and any one of the foregoing backlight modules.
  • the backlight module is located on a light inlet side of the liquid crystal display panel, and provides a backlight source for the liquid crystal display panel, so that the display apparatus implements image display.
  • the display apparatus may be any apparatus having a display function, such as a television, a mobile phone, or a tablet computer.
  • an embodiment of this application further provides a storage medium.
  • the storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to perform any brightness adjustment method shown in FIG. 4 or FIG. 10 .
  • this application may be provided as a method, a system, or a computer program product. Therefore, this application may use a form of a hardware-only embodiment, a software-only embodiment, or an embodiment with a combination of software and hardware. In addition, this application may use a form of a computer program product implemented on one or more computer-usable storage media (including but not limited to a disk memory, a CD-ROM, an optical memory, and the like) that include computer-usable program code.
  • a computer-usable storage media including but not limited to a disk memory, a CD-ROM, an optical memory, and the like
  • These computer program instructions may be stored in a computer-readable memory that can instruct the computer or any other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory generate an artifact that includes an instruction apparatus.
  • the instruction apparatus implements a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.
  • the computer program instructions may alternatively be loaded onto a computer or another programmable data processing device, so that a series of operations and steps are performed on the computer or the another programmable device, to generate computer-implemented processing. Therefore, the instructions executed on the computer or the another programmable device provide steps for implementing a specific function in one or more procedures in the flowcharts and/or in one or more blocks in the block diagrams.
  • a dimming mode corresponding to each channel may be determined based on the obtained brightness gray-scale value corresponding to each channel and the preset threshold, and the amplitude and the duty cycle of the operating current output by each channel may be determined based on the brightness gray-scale value corresponding to each channel and the dimming mode.
  • This implements area dimming of the backlight module.
  • the current adjustment mode is used in a low gray scale, the duty cycle of the operating current remains unchanged, and the amplitude of the operating current is changed to adjust the brightness of the backlight module.
  • the PWM dimming mode is used in a high gray scale, the amplitude of the operating current remains unchanged, and the duty cycle of the operating current is changed to adjust the brightness of the backlight module. Because the rise time and the fall time of the operating current in the high gray scale have small impact on the pulse waveform, the brightness linearity of the backlight module in the high gray scale is high. In addition, color stability of the backlight module can be ensured by using the PWM dimming mode in the high gray scale.
  • the brightness linearity of the backlight module in a full gray scale can be high.
  • the local current gain corresponding to each channel is set, so that brightness uniformity of the light emitting areas in the backlight module can be improved, so that in a scenario in which the liquid crystal display displays a pure-color image or a large dynamic video, uniformity of a display image is good, and a display effect is improved.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Liquid Crystal (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
EP22791075.9A 2021-04-23 2022-04-20 Procédé de réglage de luminosité pour module de rétroéclairage et dispositif associé Pending EP4310826A1 (fr)

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