CN114758614B - Display driving circuit and brightness compensation method thereof - Google Patents
Display driving circuit and brightness compensation method thereof Download PDFInfo
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- 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
- G09G3/22—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 using controlled light sources
- G09G3/30—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 using controlled light sources using electroluminescent panels
- G09G3/32—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 using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
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- 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
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- 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
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Abstract
A display driving circuit and a method for compensating brightness thereof are used for controlling a display panel. The display driving circuit includes a memory and a processor. The display panel includes a plurality of pixel circuits forming a plurality of partitions. Each partition includes a portion of the plurality of pixel circuits. The memory is used for storing a plurality of compensation data of a plurality of partitions. The processor is used for reading a plurality of compensation data to compensate the brightness of a plurality of subareas respectively, and the voltage correction quantity represented by different compensation data is positively related to the voltage drop of different subareas. The processor is also used for calculating the global load according to the gray scale values of the pixel circuits; calculating local load according to gray scale values of partial pixel circuits of a first partition of the plurality of partitions; and according to the global load and the local load, the original slope of the control signal received by the first partition is adjusted to be the adjusted slope so as to control the luminous time length of the first partition.
Description
Technical Field
The present disclosure relates to a brightness control technology of a display device, and more particularly, to a display driving circuit capable of avoiding brightness error compensation and a brightness compensation method thereof.
Background
A sub-millimeter Light Emitting Diode (Mini Light-Emitting Diode) refers to a Light Emitting Diode having a die size of about 100 microns, while a Micro Light Emitting Diode (Micro Light-Emitting Diode) is a Light Emitting Diode having a die size of less than 50 microns. When the submillimeter light-emitting diode and the micro light-emitting diode are applied to a display, the driving current is larger when the submillimeter light-emitting diode and the micro light-emitting diode emit light, so that the voltage drop (IR drop) generated by the system impedance is larger, and the driving current is different among different pixels, so that the light-emitting brightness of the display is uneven.
The conventional brightness test and correction process of the display panel before shipment writes compensation data into the memory to compensate for brightness non-uniformity of the display panel due to voltage drop. However, as the current drawn by the display panel is different, the voltage drop across different blocks will also vary. Therefore, the fixed compensation data may cause overcompensation or undercompensation, i.e. some areas of the display panel are too bright or some areas are too dark.
Disclosure of Invention
The present disclosure provides a display driving circuit for controlling a display panel. The display panel includes a plurality of pixel circuits forming a plurality of partitions. Each partition includes a plurality of pixel circuits and a portion of the pixel circuits. The display driving circuit includes a memory and a processor. The memory is used for storing a plurality of compensation data of a plurality of partitions. The processor is used for reading the plurality of compensation data to respectively compensate the brightness of the plurality of partitions, and the voltage correction quantity represented by the different compensation data is positively related to the voltage drop of the different partitions. The processor is further used for calculating a global load according to the gray scale values of the pixel circuits; calculating a local load according to gray scale values of partial pixel circuits of a first partition in the plurality of partitions; and according to the global load and the local load, the original slope of the control signal received by the first partition is adjusted to be the adjusted slope so as to control the luminous time length of the first partition.
The present disclosure provides a method for compensating brightness, which is suitable for a display driving circuit. The display driving circuit is used for controlling the display panel. The display panel includes a plurality of pixel circuits forming a plurality of partitions. Each partition includes a portion of the plurality of pixel circuits. The display driving circuit is also used for accessing a plurality of compensation data to respectively compensate the brightness of a plurality of partitions. The voltage correction amounts represented by different compensation data are positively related to voltage drops of different partitions, and the method comprises calculating a global load according to gray scale values of a plurality of pixels; calculating a local load according to gray scale values of partial pixel circuits of a first partition in the plurality of partitions; acquiring the current load current and the heaviest load current of the first partition from a lookup table according to the global load and the local load; calculating a load current difference value according to the present load current and the heaviest load current; and according to the load current difference value, the original slope of the control signal received by the first partition is adjusted to be the adjusted slope so as to control the luminous time length of the first partition.
The present disclosure provides a method for compensating brightness, which is suitable for a display driving circuit. The display driving circuit is used for controlling the display panel. The display panel includes a plurality of pixel circuits forming a plurality of partitions. Each partition includes a portion of the plurality of pixel circuits. The display driving circuit is also used for accessing a plurality of compensation data to respectively compensate the brightness of a plurality of partitions. The voltage correction amounts represented by different compensation data are positively related to voltage drops of different partitions, and the method comprises calculating a global load according to gray scale values of a plurality of pixels; calculating a local load according to gray scale values of partial pixel circuits of a first partition in the plurality of partitions; acquiring the current load current and the heaviest load current of the first partition from a lookup table according to the global load and the local load; calculating a load current difference value according to the present load current and the heaviest load current; and adjusting the original frequency of the control signal received by the first partition to be the adjusted frequency according to the load current difference value so as to control the luminous time length of the first partition.
Drawings
FIG. 1A is a simplified functional block diagram of a display panel according to one embodiment of the present disclosure.
Fig. 1B is a simplified circuit diagram of a pixel circuit according to an embodiment of the disclosure.
FIG. 2 is a simplified functional block diagram of a display driving circuit according to an embodiment of the present disclosure.
Fig. 3 is a simplified waveform diagram of signals input to the pixel circuit of fig. 2.
FIG. 4 is a flowchart of a method of compensating brightness according to an embodiment of the disclosure.
Fig. 5 is a simplified waveform diagram of the control signal of the pixel circuit in fig. 2.
FIG. 6 is a flowchart of a method of compensating brightness according to an embodiment of the disclosure.
Fig. 7 is a schematic waveform diagram of a simplified signal input to the pixel circuit.
[ symbolic description ]
Data_v image Data
Data_d display Data
100 display panel
110 display driving circuit
120 source driver
130 gate driver
140 partition
150 pixel circuit
GS, control clock signal
V data Data voltage
V scan Scanning signal
V EM Luminous signal
S11-Sij control signals
151 Transistors, 152, 153
154 pulse width modulation signal generator
155 light-emitting element
V DD First operating voltage
V SS Second operating voltage
I LED Drive current
210 memory
220 processor
Cm_11 to Cm_ij compensation data
V out Output signal
V original Initial voltage value
400 600:
s410, S420, S430, S440, S450, S610, S620, S630, S640, S650 steps
Delta t time difference
T EM_stage Total time length of lighting phase
T EM_original_on Pixel circuit original light emitting time length
T EM_after_on Length of lighting time
Detailed Description
Embodiments of the present disclosure will be described below with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or similar elements or method flows.
FIG. 1A is a simplified functional block diagram of a display panel 100 according to one embodiment of the present disclosure. The display panel 100 includes a plurality of pixel circuits 150 forming a plurality of partitions 140, that is, each partition 140 includes a portion of the pixel circuits 150 of the plurality of pixel circuits 150. The display panel 100 further includes a display driving circuit 110, a source driver 120, and a gate driver 130. The display driving circuit 110 is used for providing display Data data_d to the source driver 120, providing control clock signals GS to the gate driver 130 and providing control signals S11-Sij to the plurality of partitions 140 according to the image Data data_v. In some embodiments, the image Data data_v may come from a Graphics Processor (GPU) or a Central Processing Unit (CPU). The display Data data_d is used to designate gray scale values of the plurality of pixel circuits 150. The source driver 120 is used for providing a plurality of Data voltages V according to the display Data Data_d data (only one of which is shown for simplicity) to a plurality of pixel circuits 150. The gate driver 130 is used for providing a plurality of scan signals V scan (only one of which is shown for simplicity) to the plurality of pixel circuits 150 to drive the plurality of pixel circuits 150 to receive the data voltage V data 。
In one embodiment, the display driving circuit 110 may be implemented by a display driving chip (Display Driver IC, abbreviated as DDIC). In one embodiment, the display driver circuit 110 may be implemented by a timing controller (timing controller, TCON for short), a field programmable gate array (field programmable gate array, FPGA for short), or an application specific integrated circuit (application specific integrated circuit, ASIC for short). The timing controller may be used to control the timing operation of the display panel 100, for example, adjust the frequency of the clock signal GS to control the update rate of the display panel 100 to achieve the power saving function; the timing controller may also process the image Data data_v, such as decoding the image Data data_v, changing a resolution (Scaling) of the image Data data_v, analog-to-digital converting the image Data data_v when the image Data data_v is in an analog form, and the like.
The plurality of partitions 140 are arranged in a matrix having i rows and j columns, i.e., a total of i x j partitions 140, where i and j are positive integers. The control signals S11 to Sij are respectively transmitted to the i×j partitions 140, and the index in each index of the control signals S11 to Sij represents the corresponding partition 140. For example, the control signal S11 is sent to all the pixel circuits 150 in the partition 140 located in the upper left corner of fig. 1A; the control signal Sij is sent to all the pixel circuits 150 in the partition 140 located in the lower right corner of fig. 1A, and so on.
Fig. 1B is a simplified circuit diagram of a pixel circuit 150 according to an embodiment of the disclosure. Fig. 1B shows the pixel circuits 150 in the partitions 140 receiving the control signals Sij, and it is understood that the pixel circuits 150 in different partitions 140 may have the same circuit structure but receive different control signals. The pixel circuit 150 includes transistors 151, 152, and 153, a Pulse Width Modulation (PWM) signal generator 154, and a light emitting element 155. A control terminal of the transistor 151 is for receiving a scan signal V scan A first end for receiving a data voltage V data The second terminal is coupled to the PWM signal generator 154. The control terminal of the transistor 152 receives the light-emitting signal V EM A first end for receiving a first operating voltage V DD The second terminal is coupled to the first terminal of the transistor 153, in which the light-emitting signal V EM May be generated by the gate drive circuit 130 or an additional gate drive circuit. The control terminal of the transistor 153 receives the output signal V output by the PWM signal generator 154 out The first terminal is coupled to the second terminal of the transistor 152, and the second terminal is coupled to the first terminal of the light emitting element 155.
In the present embodiment, the control signals S11 to Sij are ramp signals. The PWM signal generator 154 is for receiving the control signal Sij and for generating a data voltage V according to the slope of the control signal Sij data Determining an output signal V out In which the output signal V out For turning on transistor T153. Therefore, the light emitting time of the pixel circuit 150 is related to the slope of the control signal Sij and the data voltage V data Is of the magnitude of (and) the output signal V out Is a pulse width of (a) a pulse width of (b).
FIG. 2 is a simplified functional block diagram of the display driving circuit 110 according to one embodiment of the present disclosure. The display driving circuit 110 includes a memory210 and a processor 220. The memory 210 is used for storing a plurality of compensation data cm_11 to cm_ij of the plurality of partitions 140, and an index in each index of the compensation data cm_11 to cm_ij represents the partition 140 corresponding thereto. The processor 220 is used for reading the plurality of compensation data cm_11 to cm_ij to compensate the brightness of the plurality of partitions 140 respectively. For example, the processor 220 may adjust the display Data data_d according to the compensation Data cm_11 so that a plurality of Data voltages V are provided to the upper left corner region 140 of fig. 1A data Has a common voltage correction. For another example, the processor 220 may adjust the display Data data_d according to the compensation Data Cm_ij so that a plurality of Data voltages V are provided to the lower right corner partition 140 of FIG. 1A data With another common voltage modifier.
The voltage correction represented by the different compensation data is positively correlated to the voltage drop (IR drop) of the different partitions 140. The voltage drop refers to the first operating voltage V DD (or second operating voltage V) SS ) When the voltage is transmitted to the power line, the voltage is reduced (or increased) by the impedance of the power line. In some embodiments, the lower partition 140 in fig. 1A has a greater voltage drop. For example, the voltage drop of the partition 140 corresponding to the compensation data cm_ij is greater than the voltage drop of the partition 140 corresponding to the compensation data cm_1j, so that the voltage correction amount represented by the compensation data cm_ij is greater than the voltage correction amount represented by the compensation data cm_1j, and so on, thereby eliminating the uneven brightness (mura) phenomenon of the display panel 100. However, the disclosure is not limited thereto, and the voltage drop of each partition 140 may be different according to the actual arrangement of the power lines.
In some embodiments, the brightness test and correction process before the display panel 100 leaves the factory writes the compensation data Cm_11-Cm_ij into the memory 210. However, as the current drawn by the display panel 100 varies, the voltage drop across the block 140 varies. Therefore, the fixed compensation data Cm_11-Cm_ij may cause overcompensation or undercompensation, i.e. the brightness of the block 140 is too bright or too dark. Accordingly, the present disclosure provides two methods 400 and 600 of compensating brightness to improve this problem, and the methods 400 and 600 of compensating brightness will be described in the following paragraphs with reference to fig. 4 and 6. To facilitate understanding of the brightness compensation method 400, the control signals provided by the display panel 100 to the pixel circuit 150 of fig. 2 and the operation of the pixel circuit 150 of fig. 2 are described below with reference to fig. 3.
Fig. 3 is a simplified waveform diagram of signals input to the pixel circuit 150 of fig. 2. In the embodiment of fig. 3, transistors 151, 152, and 153 are P-type transistors. The operation of the pixel circuit 150 in a frame can be divided into three phases, namely a reset phase, a scan phase and a light-emitting phase T EM_Stage . In fig. 3, the waveform of the control signal Sij indicated by the dotted line is a preset waveform of the control signal Sij, and the waveform indicated by the solid line is a waveform adjusted by the brightness compensation method 400, and the control signal Sij actually output to the pixel circuit 150 has the waveform indicated by the dotted line.
Referring to fig. 2 and 3, in the reset phase, the data signal V with the voltage correction is applied data The PWM signal generator 154 is inputted.
In the scanning phase, the pixel circuit 150 can detect and compensate the variation of the threshold voltage of the transistor 153 to make the driving current I generated by the transistor 153 LED The magnitude is not affected by the threshold voltage of the transistor 153. Methods for compensating for threshold voltage variations are well known to those skilled in the art, and thus, the description thereof will be omitted herein.
In the light-emitting stage, the control signal Sij will be from the initial voltage value V original Start falling, and when the control signal Sij falls below the data voltage V data The PWM signal generator 154 generates the output signal V out Having pulses to turn on transistor 153 to generate drive current I LED . As can be seen from fig. 3, the waveform of the control signal Sij is adjusted to make the output signal V out The pulse width of the pixel circuit 150 is reduced by a time difference Δt. The above-mentioned problems of overcompensation or undercompensation can be improved by adjusting the slope of the control signal Sij to control the time difference Δt. The following describes the step of adjusting the slope of the control signal Sij in detail with the method 400 of brightness compensation in fig. 4.
FIG. 4 is a flow chart of a method 400 of compensating brightness according to one embodiment of the present disclosure. The method 400 will be described below in conjunction with fig. 2-4. The method 400 adjusts the slope of a control signal (e.g., the control signal Sij, as illustrated below) to avoid overcompensation or undercompensation of the block 140 corresponding to the control signal. However, the method 400 may be performed multiple times to adjust the slope of all of the control signals S11-Sij. Any combination of the features of method 400, or other methods described herein, may be implemented by a plurality of instructions stored in a non-transitory computer readable medium or the aforementioned memory 210. These instructions, when executed, cause processor 220 to perform part or all of any of the methods described above. It should be understood that any of the methods described herein may include more or fewer steps than shown in the flowcharts, and that the steps in the methods may be performed in any suitable order.
Step S410 is to calculate the global load (which can be understood as the average gray level of all the pixel circuits 150 in the display panel 100) according to the gray level of all the pixel circuits 150 in the display panel 100, wherein the global load L g The calculation is as in equation 1:
in formula 1, n pixel Represents the number g of the plurality of pixel circuits 150 i Represents the gray scale value g of each pixel circuit 150 max I is a positive integer representing the maximum gray scale value of the display panel 100.
In one embodiment, the resolution of the display panel 100 is 800×600, (i.e., the number of pixels is 480000), and the gray scale range is 0-255. If the gray scale value of each pixel circuit 150 is 100, the global load L g 39.2%.
Step S420 is to calculate the local load L according to the gray scale values of all the pixel circuits 150 of one partition 140 l (it can be understood that the average gray scale value of all the pixel circuits 150 in the partition 140), wherein the local load L l The calculation is as in formula 2:
in formula 2, n part_pixel Representing the number of pixel circuits 150 in the partition 140, j is a positive integer.
In one embodiment, the number of the pixel circuits 150 in one partition 140 is 1000, the gray scale value of the display panel 100 ranges from 0 to 255, and if the gray scale value of each pixel circuit 150 in the partition 140 is 150, the local load L is l 58.8%.
Step S430 is based on the global load L g And the local load L of a partition 140 l Retrieving the present load current I for the partition 140 from a look-up table present And the heaviest load current I max . In one embodiment, the lookup table may be stored in memory 210 of FIG. 2. Now load current I present It can be understood that the partition 140 now has the drive current I of all the pixel circuits 150 LED Average value of (2). The heaviest load current I max It can be understood that the driving current I of the pixel circuits 150 of the partition 140 is equal to the driving current I of the pixel circuits 150 of the display device 100 when all the pixel circuits 150 display the highest gray level LED 。
Step S440 is based on the present load current L l And the heaviest load current I max The load current difference Δi is calculated as shown in equation 3:
ΔI＝I present -I max formula 3
In step S450, the slope of the control signal Sij is adjusted according to the load current difference Δi, and the relationship between the slope of the control signal Sij before and after adjustment is described by the following formula.
First, after considering the voltage drop of the partition 140, a representative data voltage V of the partition 140 data Can be represented by equation 4, wherein the initial voltage V original Representing the voltage value of the control signal Sij at the beginning of the lighting phase:
V data ＝V original ×L g L l formula 4
Referring back to FIG. 3, when the control signalThe number Sij drops below the data voltage V data When this occurs, the pixel circuit 150 starts to emit light. Therefore, by the similar triangle relationship, when the slope of the control signal Sij is not adjusted, the original light emitting time length of the pixel circuit 150 can be expressed by formula 5:
in the above formula, T EM_original_on Representing the original light emission time length, T, of the pixel circuit 150 EM_stage Representing the total length of time of the light-emitting phase,
as described above, the slope adjustment of the control signal Sij can shorten the light-emitting time of the pixel circuit 150 by a time difference Deltat, which can be obtained by the current I of the load present And the heaviest load current I max The expression is as shown in formula 6:
then, when the slope of the control signal Sij is adjusted, a representative light-emitting time period of all the pixel circuits 150 in the partition 140 can be expressed by equation 7:
therefore, the slope of the control signal Sij before adjustment can be expressed as "equation 8", where slope original The slope before adjustment of the control signal Sij is shown:
the slope of the adjusted control signal S_ij may be expressed as equation 9, where slope represents the slope of the adjusted control signal Sij:
in the whole domain load L g When smaller, the voltage drop of the whole panel is smaller, so that the driving current I flowing through the pixel circuit 150 LED Rising and overcompensation may occur. However, as can be seen from equation 9, the rising drive current I LED The load current difference Δi is increased, so that the slope of the control signal Sij is increased (because the slope of the control signal Sij is negative), and the light emitting time of the pixel circuit 150 is shortened to reduce the brightness thereof, thereby avoiding the overcompensation phenomenon. On the other hand, in the whole domain, load L g When larger, the voltage drop of the whole panel is larger, so that the driving current I flowing through the pixel circuit 150 LED At this time, the load current difference Δi decreases, so that the slope of the control signal Sij is moderately decreased, and the phenomenon of insufficient compensation is avoided. That is, the load current difference Δi and the slope of the control signal Sij are positively correlated.
Fig. 5 is a simplified waveform diagram of the control signals of the pixel circuit 150 in fig. 2. In the embodiment of fig. 5, the transistors 151, 152 and 153 are P-type transistors, and the control signals S11 to Sij are clock signals. The operation area of the pixel circuit 150 is divided into three phases, namely a reset phase, a scan phase and a light-emitting phase T EM_Stage . In fig. 5, the waveform of the control signal Sij indicated by a dotted line is a preset waveform of the control signal Sij, and the waveform indicated by a solid line is a waveform adjusted by the method 600 for compensating brightness, and in fact, the control signal Sij output to the pixel circuit 150 has the waveform indicated by the solid line. The operation of the reset phase and the scan phase of fig. 5 is the same as that of fig. 3, and the description thereof is not repeated here.
In the light emitting stage, when the control signal Sij has continuous pulses, the PWM signal generator 154 outputs the signal V out With pulses to turn on the crystalBody tube 153 for generating drive current I LED . As can be seen from fig. 5, the control signal Sij has a predetermined number (e.g. 4) of pulses in the light-emitting stage, and the frequency of the waveform of the adjusted control signal Sij is relatively high, so that the output signal V is generated out The pulse width of the pixel circuit 150 is reduced by a time difference Δt.
In other words, if the frequency of the control signal Sij becomes higher, the light emitting time length of the pixel circuit 150 is shortened, and if the frequency of the control signal Sij becomes lower, the light emitting time length of the pixel circuit 150 is lengthened. The above-mentioned problems of overcompensation or undercompensation can be improved by adjusting the frequency of the control signal Sij to control the time difference Δt. The following describes in detail the steps of adjusting the frequency of the control signal Sij in the method 600 of brightness compensation in fig. 6.
FIG. 6 is a flow chart of a method 600 of compensating for brightness according to one embodiment of the present disclosure. The method 600 improves the phenomenon of overcompensation or undercompensation of the brightness by adjusting the frequency of the control signal Sij. However, the method 600 may be performed multiple times to adjust the slope of all control signals S11-Sij. Any combination of the features of method 600, or other methods described herein, may be implemented by a plurality of instructions stored in a non-transitory computer readable medium or the aforementioned memory 210. These instructions, when executed, cause processor 220 to perform part or all of any of the methods described above. It should be understood that any of the methods described herein may include more or fewer steps than shown in the flowcharts, and that the steps in the methods may be performed in any suitable order.
Step S610 is to calculate the global load L according to the gray scale values of all the pixel circuits 150 in the display panel 100 g The global load is calculated in the same manner as in step S410, and the description thereof is not repeated here.
Step S620 is to calculate the local load according to the gray scale values of all the pixel circuits 150 of one partition 140, wherein the local load is calculated in the same manner as step S420, and the detailed description is omitted herein.
Step S630 is to obtain from the lookup table based on the global load and the local loadCurrent load current I of one partition 140 present And the heaviest load current I max 。
Step S640 is based on the present load current I present And the heaviest load current I max The load current difference Δi is calculated, wherein the load current difference Δi is calculated in the same manner as step S440, and the description thereof is not repeated here.
In step S650, the frequency of the control signal Sij is adjusted according to the load current difference Δi, and the relationship between the frequency of the control signal Sij before and after adjustment will be described by the derivation of the formula.
The adjusted light-emitting time of the pixel circuit 150 can be obtained by the current I present And the heaviest load current I max Calculation as shown in equation 10:
the frequency of the control signal Sij is inversely proportional to the light emission time length as shown in formula 11:
in formula 11, freq original Representing the frequency of the control signal Sij before adjustment, freq after Representing the adjusted frequency of the control signal Sij.
As can be seen from equation 11, the rising drive current I LED The load current difference Δi is increased, so that the frequency of the control signal Sij is increased, and the light emitting time of the pixel circuit 150 is shortened to reduce the brightness thereof, thereby avoiding the overcompensation phenomenon. On the other hand, in the whole domain, load L g When larger, the voltage drop of the whole panel is larger, so that the driving current I flowing through the pixel circuit 150 LED At this time, the load current difference Δi decreases, so that the frequency of the control signal Sij is moderately decreased, and the phenomenon of insufficient compensation is avoided. That is, the load current difference Δi and the frequency of the control signal Sij are positively correlated.
Fig. 7 is a simplified waveform diagram of the signal input to the pixel circuit 150. The signal waveforms of fig. 7 are applicable to an embodiment in which the transistors 151, 152, and 153 of the pixel circuit 150 are implemented as N-type transistors. Thus, the data voltage V data Control signal Sij, scan signal V scan And a luminous signal V EM Having a waveform that is inverted from the corresponding signal in fig. 4.
In the embodiment of fig. 7, the waveform of the control signal Sij indicated by the solid line is a preset waveform of the control signal Sij, and the waveform indicated by the dotted line is a waveform adjusted by the method 400, and the control signal Sij actually output to the pixel circuit 150 has the waveform indicated by the dotted line. As can be seen from fig. 7, if the current difference Δi increases, the slope of the control signal Sij should decrease (the slope of the control signal Sij is a positive value) to reduce the light emitting time of the pixel circuit 150, and if the current difference Δi decreases, the slope of the control signal Sij should increase. That is, when the method 400 is applied to the pixel circuit 150 fabricated with N-type transistors, the method 400 can adaptively correct such that the current difference Δi is inversely related to the slope of the control signal Sij.
On the other hand, when the method 600 is applied to the pixel circuit 150 fabricated with N-type transistors, the relationship between the current difference Δi and the frequency of the control signal Sij can still be kept positive, so the description is not repeated.
Certain terms are used throughout the description and claims to refer to particular components. However, those of ordinary skill in the art will appreciate that like elements may be referred to by different names. The description and claims do not take the difference in name as a way of distinguishing elements, but rather take the difference in function as a basis for distinguishing elements. In the description and claims, the terms "comprise" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. In addition, "coupled" herein encompasses any direct and indirect connection. Thus, if a first element couples to a second element, that connection may be through an electrical or wireless transmission, optical transmission, etc., directly to the second element, or through other elements or connections indirectly to the second element.
As used herein, the term "and/or" is intended to encompass any combination of one or more of the items listed. In addition, any singular reference is intended to encompass a plural reference unless the specification expressly states otherwise.
The foregoing is only illustrative of the preferred embodiments of the present disclosure, and all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (4)
1. A display driving circuit for controlling a display panel, wherein the display panel includes a plurality of pixel circuits forming a plurality of partitions, each partition including a portion of the pixel circuits, the display driving circuit comprising:
a memory for storing a plurality of compensation data for the plurality of partitions; and
a processor for reading a plurality of compensation data to compensate the brightness of the plurality of partitions respectively, wherein the voltage correction amounts represented by different compensation data are positively related to the voltage drops of different partitions;
wherein the processor is further configured to:
calculating a global load according to the gray scale values of the pixel circuits;
calculating a local load according to the gray scale value of the part of pixel circuits of a first partition in the plurality of partitions; and
adjusting the original slope of the control signal received by the first partition to be an adjusted slope according to the global load and the local load to control the light emitting time length of the first partition,
wherein the global load is obtained by the following equation:
wherein L is g Representing the global load, n pixel Representing the multipleNumber of pixel circuits g i Represents the gray scale value g of each pixel circuit in the display panel max Representing the maximum gray scale value of the display panel, wherein i is a positive integer; and
wherein the local load is derived from the following equation:
wherein L is l Representing the local load, n part_pixel Representing the number of pixel circuits g j Representing the gray scale value of each pixel circuit in the first partition, j is a positive integer,
wherein the adjusted slope of the control signal is obtained from the following equation:
wherein slope is the original Representing the original slope after Represents the adjusted slope, ΔI represents the local load current difference, I present Representing the current of the local load, L g Representing the global load, L l Representing the local load.
2. The display driver circuit of claim 1, wherein the processor is further configured to:
obtaining the current local load current and the heaviest load current of the first partition from a lookup table according to the global load and the local load, calculating the local load current difference value according to the current local load current and the heaviest load current, and adjusting the slope of the control signal according to the load current difference value.
3. A method of compensating brightness, adapted for use in a display driver circuit for controlling a display panel, the display panel comprising a plurality of pixel circuits forming a plurality of partitions, each partition comprising a portion of the pixel circuits, the display driver circuit further adapted to access a plurality of compensation data for compensating brightness of the plurality of partitions, respectively, the voltage correction represented by different compensation data being positively related to voltage drops of different partitions, the method comprising:
calculating a global load according to the gray scale values of the pixels;
calculating a local load according to the gray scale value of the part of pixel circuits of a first partition in the plurality of partitions;
acquiring the current load current and the heaviest load current of the first partition from a lookup table according to the global load and the local load;
calculating a load current difference value according to the present load current and the heaviest load current; and
adjusting the original slope of the control signal received by the first partition to be the adjusted slope according to the load current difference value to control the luminous time length of the first partition,
wherein the global load is obtained by the following equation:
wherein L is g Representing the global load, n pixel G represents the number of the pixel circuits i Represents the gray scale value g of each pixel circuit in the display panel max Representing the maximum gray scale value of the display panel, wherein i is a positive integer; and
wherein the local load is derived from the following equation:
wherein L is l Representing the local load, n part_pixel Representing the number of pixel circuits g j Representing the gray scale value of each pixel circuit in the first partition, j is a positive integer, wherein the controlThis adjusted slope of the signal is obtained from the following equation:
wherein slope is the original Representing the original slope after Represents the adjusted slope, ΔI represents the local load current difference, I present Representing the current of the local load, L g Representing the global load, L l Representing the local load.
4. A method of compensating brightness for a display driving circuit for controlling a display panel comprising a plurality of pixel circuits forming a plurality of partitions, each partition comprising a portion of the pixel circuits, the display driving circuit further for accessing a plurality of compensation data to compensate for the brightness of the plurality of partitions respectively, and voltage correction amounts represented by different compensation data being positively related to voltage drops of the different partitions, the method comprising:
calculating a global load according to the gray scale values of the pixel circuits;
calculating a local load according to the gray scale value of the part of pixel circuits of a first partition in the plurality of partitions;
acquiring the current load current and the heaviest load current of the first partition from a lookup table according to the global load and the local load;
calculating a load current difference value according to the present load current and the heaviest load current; and
according to the load current difference, the original frequency of the control signal received by the first partition is adjusted to be the adjusted frequency so as to control the light emitting time length of the first partition, wherein the global load is obtained by the following equation:
wherein L is g Representing the global load, n pixel G represents the number of the pixel circuits i Represents the gray scale value g of each pixel circuit in the display panel max Representing the maximum gray scale value of the display panel, wherein i is a positive integer; and
wherein the local load is derived from the following equation:
wherein L is l Representing the local load, n part_pixel Representing the number of pixel circuits g j And a gray scale value j representing each pixel circuit in the first partition, wherein j is a positive integer, and the adjusted frequency of the control signal is obtained by the following equation:
wherein ΔI represents the local load current difference, I present Representing the current local load current, freq original Representing the original frequency, freq after Representing the adjusted frequency.
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