CN111341246B - Backlight control method - Google Patents
Backlight control method Download PDFInfo
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- CN111341246B CN111341246B CN201811641156.2A CN201811641156A CN111341246B CN 111341246 B CN111341246 B CN 111341246B CN 201811641156 A CN201811641156 A CN 201811641156A CN 111341246 B CN111341246 B CN 111341246B
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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]
Abstract
The utility model provides a light-emitting unit includes first switch tube, second switch tube, LED chip array and first storage capacitor, the grid of first switch tube is scanning signal input end, the source electrode of first switch tube is data signal input end, the positive electrode of LED chip array is power signal input end, the drain electrode ground connection of second switch tube, and the LED light source is high-voltage light source, promotes its luminous component operating voltage, reduces the consumption of operating current in order to reduce the switch tube of drive LED to reduce whole consumption.
Description
Technical Field
The invention belongs to the technical field of display, and particularly relates to a backlight control method.
Background
Currently, lighting technologies are mostly driven in a static or passive manner. Compared with the conventional technology, the TFT (Thin Film Transistor) backplane can drive the Light Emitting element in an active manner, has the advantages of high contrast, energy saving, and the like, and is commonly used for driving a liquid crystal panel or an OLED (Organic Light-Emitting Diode) panel.
For example, in an active driving circuit of a 2T1C (2 switching transistors +1 capacitor) pixel unit in a display panel, a switching transistor connected in series with an LED often needs to bear a large current, so that the power consumption of the switching transistor is high.
Disclosure of Invention
In view of this, embodiments of the present invention provide a light emitting unit, an assembly, a circuit and a display device, which aim to solve the problem of high power consumption of a switching tube of a pixel unit.
A first aspect of an embodiment of the present invention provides a light emitting unit, including a first switch tube, a second switch tube, an LED light source, and a first storage capacitor, where:
the grid electrode of the first switch tube is a scanning signal input end, the source electrode of the first switch tube is a data signal input end, the drain electrode of the first switch tube is connected with the grid electrode of the second switch tube and the first end of the first storage capacitor, the second end of the first storage capacitor is grounded, the drain electrode of the second switch tube is connected with the negative electrode of the LED light source, the positive electrode of the LED light source is a power signal input end, the source electrode of the second switch tube is grounded, and the LED light source comprises more than two non-high-voltage LED chips connected in series or the LED light source is a high-voltage LED chip.
A second aspect of embodiments of the present invention provides a light emitting assembly, including: the light emitting unit and the packaging body for packaging the light emitting unit are provided;
the package body includes: the device comprises a power supply interface, a scanning line interface, a data line interface and a grounding interface;
the positive electrode of the LED light source is connected with the power interface, the grid electrode of the first switch tube is connected with the scanning line interface, the source electrode of the first switch tube is connected with the first data line interface, and the source electrode of the second switch tube is connected with the grounding interface.
A third aspect of embodiments of the present invention provides a light emitting circuit, including: a power line, a ground line and a plurality of the light-emitting units distributed in an array; wherein, each row of the light-emitting units is provided with a data line, and each column of the light-emitting units is provided with a scanning line;
the grid electrode of the first switch tube of each light-emitting unit is connected with the corresponding scanning line, the source electrode of the first switch tube of each light-emitting unit is connected with the corresponding data line, the positive electrode of the LED light source of each light-emitting unit is connected with the power line, and the source electrode of the second switch tube of each light-emitting unit is connected with the grounding line.
A fourth aspect of an embodiment of the present invention provides a display device, including:
a display panel including a plurality of the light emitting units; and
and the control unit is electrically connected with the display panel, and is used for driving the display panel.
According to the light emitting unit, the light emitting assembly, the circuit and the display device, the light emitting component of the light emitting unit is provided with the plurality of LED chips or the high-voltage LED chips which are connected in series, so that the working voltage of the light emitting component is improved, the working current is reduced, the power consumption of the switch tube for driving the LED is reduced, and the overall power consumption is reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic circuit diagram of a light emitting unit according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an energy storage capacitor in a light emitting unit according to an embodiment of the present invention;
fig. 3 is a schematic circuit diagram of a light emitting unit according to a first embodiment of the invention;
FIG. 4 is an I-V curve of a resistor not connected in series in a conventional switch tube for driving a common non-high voltage LED chip and an I-V curve of a resistor R1 connected in series in a switch tube M2 of the light emitting unit shown in FIG. 1;
fig. 5 is a graph of the relationship between the output voltage of the driver of the light emitting unit and the LED brightness according to the present invention;
fig. 6 is a schematic circuit diagram of a light emitting unit according to a second and third embodiments of the present invention;
fig. 7 is a schematic structural view of a medium-high voltage LED chip of the light emitting unit shown in fig. 6;
fig. 8 is a schematic circuit diagram of a light emitting unit according to a fourth embodiment of the invention;
FIG. 9 is an I-V curve of a resistor connected in series between a switching tube for driving a normal non-high voltage LED chip and an I-V curve of a resistor R1 connected in series between a switching tube M2 for driving a normal non-high voltage LED chip in the light emitting unit shown in FIG. 1;
FIG. 10 is an I-V curve of a resistor not connected in series with a switching tube for driving a high voltage LED chip and an I-V curve of a resistor R1 connected in series with a switching tube M2 for driving a high voltage LED chip in the light emitting unit shown in FIG. 1;
fig. 11 is a schematic structural diagram of a light emitting device according to an embodiment of the present invention;
fig. 12 is a schematic structural diagram of a light emitting device according to another embodiment of the present invention;
FIG. 13 is an exemplary circuit schematic of a lighting circuit provided in accordance with one embodiment of the present invention;
fig. 14 is a schematic structural diagram of a display device according to an embodiment of the invention;
FIG. 15 is a flowchart illustrating steps of a backlight control method according to an embodiment of the invention;
fig. 16 is a flowchart illustrating a detailed implementation of a backlight control method according to another embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, the technical solutions in the embodiments of the present invention will be clearly described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terms "comprises" and "comprising," and any variations thereof, in the description and claims of this invention and the above-described drawings are intended to cover non-exclusive inclusions. For example, a process, method, or system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus. Furthermore, the terms "first," "second," and "third," etc. are used to distinguish between different objects and are not used to describe a particular order.
The discrete electronic component in the embodiment of the present invention refers to an electronic component that functions as an independent circuit and constitutes a basic unit of a circuit, for example, a resistor, a capacitor, an inductor, an electromechanical element (a connector, a switch, a relay, or the like), an electroacoustic device, an optoelectronic device, a sensitive component, a display device, a piezoelectric device, or the like.
Referring to fig. 1, the light emitting unit 10 of the present invention includes a first switch tube M1, a second switch tube M2, an LED chip (light source) D1, and a storage capacitor C1.
The grid electrode of the first switch tube M1 is a scanning signal input end; the source electrode of the first switch tube M1 is a data signal input end; the drain of the first switching tube M1 is connected to the gate of the second switching tube M2 and the first end of the storage capacitor C1, the source of the second switching tube M2 is connected to the negative electrode of the LED light source D1, and the positive electrode of the LED light source D1 is the power signal input end; the drain of the second switch transistor M2 and the second terminal of the storage capacitor C1 are grounded.
In one embodiment, the first switch M1 is fabricated on a Thin Film Transistor (TFT) backplane, and the second switch M2 is soldered on the TFT backplane. The connecting wires of the light emitting unit 10 are also fabricated on the TFT backplane, and the second switching tube M2 is a discrete component, that is, a pad of the second switching tube M2 is disposed on the TFT backplane and used for soldering the second switching tube M2.
In one embodiment, the TFT backplane is further provided with a pad for soldering the LED chip D1, and the LED chip D1 is soldered directly on the TFT backplane.
In one embodiment, the first switching tube M1 and the second switching tube M2 are MOS tubes, and the MOS tubes fabricated in the TFT backplane cannot bear the current required by the LED chip, and the LED chip is driven by using separate MOS tubes. More specifically, the first switching tube M1 and the second switching tube M2 are both N-type MOS tubes, and then the source of the N-type MOS tube is used as the drain of the switching tube, and the gate of the N-type MOS tube is used as the gate of the switching tube.
Referring to fig. 2, in one embodiment, the printed circuit board on which the light emitting unit 10 is disposed includes a first printed circuit board layer 21 and a second printed circuit board layer 22, wherein the first printed circuit board layer 21 is disposed with a first metal electrode 11, and the second printed circuit board layer 22 is disposed with a second metal electrode 12. Specifically, the first metal electrodes 11 correspond to the second metal electrodes 12 one by one, and are disposed opposite to each other to form a storage capacitor C1 with the light emitting unit 10; the first metal electrode 11 is connected to the ground of the light emitting cell 10 as the first terminal of the storage capacitor C1, and the second metal electrode 12 is connected to the ground of the storage capacitor C1 as the second terminal. In other embodiments, when the printed circuit board is a single-layer circuit board, the first printed circuit board layer 21 and the second printed circuit board layer 22 are respectively used as the front surface and the back surface of the printed circuit board, i.e. the first metal electrode 11 and the second metal electrode 12 are respectively disposed on the front surface and the back surface of the printed circuit board.
In the present embodiment, the storage capacitor C1 is separated and disposed in the printed circuit board, thereby avoiding a capacitor having a large volume and reducing the volume of the light emitting unit 10. Of course, the storage capacitance C1 may be implemented using a capacitor regardless of the volume of the light emitting cell 10.
As an embodiment of the present invention, the first metal electrode 11 and the second metal electrode 12 are both metal copper sheets. In this embodiment, the area of the metal copper sheet can be set according to the user's requirement, and the capacitance of the storage capacitor is changed by changing the corresponding areas of the two oppositely-arranged metal copper sheets.
As an embodiment of the present invention, an insulating dielectric is provided between the first metal electrode 11 and the second metal electrode 12. In the present embodiment, the capacitance C of the storage capacitor C1 is ∈ S/4 π kd, where ∈ is the dielectric constant, k is the constant of the electrostatic force, S is the area of the two plates facing each other, and d is the distance between the first metal electrode 11 and the second metal electrode 12. Specifically, the distance between the first metal electrode 11 and the second metal electrode 12 is adjusted by adjusting the thickness of the insulating dielectric, so as to achieve the purpose of changing the capacitance of the storage capacitor C1 as required.
In an embodiment, referring to fig. 3, in the embodiment, a resistor R1 is added to the light emitting unit and is connected in series with the second switching tube M2 of the LED chip D1, and the drain of the second switching tube M2 is grounded through the resistor R1, so that the current-voltage curve of the second switching tube M2 becomes more gradual, and for the same current variation range, the corresponding new voltage control range becomes larger, and modulation with higher precision can be realized, thereby improving the gray scale control capability of the LED.
In this embodiment, the LED chip D1 is a Mini-LED chip, which is a display screen that uses precision devices and precision packaging to realize sub-millimeter pixel particles, so the Mini-LED is also called a sub-millimeter light emitting diode, and the Mini-LED has a higher integration level and can realize a smaller dot pitch of one millimeter or less.
Specifically, when a 2T1C circuit is built, a series resistor R1 is added to the drain of the second switch tube M2. Referring to fig. 3, at this time, the resistor R1 and the second switch M2 are regarded as a new switch M2'. Then the I-V curve of the new switch tube M2' is more suitable for enhancing the accuracy of the circuit for LED gray scale control, as shown in FIG. 4, making VgsIs the gate-source voltage, V, of the second switch transistor M2gs'is the voltage between the gate and the source of the new switch transistor M2', and there is a physical relationship Vgs’＝Vgs+Ids*R1，IdsFor the current flowing through the drain to source of the switch M2', R1Is the resistance of resistor R1. The I-V curve of the conventional switch tube without increasing the series resistance is shown as a curve A1, and the I-V curve of the new switch tube M2' with increasing the series resistance R1 is shown as a curve A2. Due to Ids*R1Due to the existence of this term, the curve a2 becomes more gradual than the curve a1, and the voltage range of the corresponding new adjustment gray scale becomes larger for the same current variation range, so that modulation with higher precision can be realized.
As shown in fig. 5, a curve B11 shows the voltage V of the data signal output by the driver of the light emitting cell shown in fig. 1dataThe relationship between the luminance B of the LED and the luminance B of the LED shows that the driver voltage corresponding to the LED luminance adjustable region B1-B3 is basically in a low current region, the luminance of the LED luminance adjustable region is also low, and the region with high luminance has a very steep curve due to the corresponding large current region, poor adjustability and a large error. On the other hand, the discrete component (the switching tube M2) has a high dispersion of the threshold voltage Vth, which brings a part of errors, and the deviation of the LED brightness caused by the voltage error is more sensitive in the large current region than in the small current region.
Curve B12 shows the voltage V output by the driver of the lighting unit shown in fig. 3dataAnd the LED brightness B; for the light-emitting units of the series resistors, the driver voltage corresponding to the LED brightness adjustable region B2-B4 spans in a small current region and a large current region, the LED brightness adjustable region is large, the brightness of the light-emitting unit can be changed from low to high, the adjustability is good, and the error is low. On the other hand, the discrete device (new switching tube M2') has a relatively low dispersion of the threshold voltage Vth, and thus has a small error, and the LED luminance deviation caused by the dispersion is relatively low in sensitivity in both a large current region and a small current region.
The value of the resistor R1 may be 2 x 10 depending on the operating current of the LED and the voltage range needed to control the gray scale- 3Ohm to 5 x 107Ohm. In the case of Mini-lighting, the resistance R1 may preferably take the value 2 x 100Ohm to 2 x 103Ohm。
In one embodiment, referring to fig. 6, in the embodiment, the LED light source 13 in the light emitting unit 10 includes more than two non-high voltage LED chips D1-Dm connected in series or the LED light source 13 is a high voltage LED chip. The working voltage of the light emitting part of the LED driving circuit is improved, the working current is reduced, the power consumption of a switch tube for driving the LED is reduced, and therefore the overall power consumption is reduced.
The working voltage of a common (non-high voltage) single LED chip is about 2V-3V, while the working voltage V of the MOS tube commonly applied to dynamic backlightdsApproximately 2-4V. Therefore, in the series circuit of the LED light source 13 and the switching tube M2, more than 50% of the power is consumed by the MOS tube. In contrast, in this embodiment, the operating voltage of the LED light source 13 is increased to reduce the power consumption of the switching tube driving the LED light source 13, so as to improve the energy efficiency of the whole circuit. In this embodiment, the operating voltage of the LED light source 13 is in the range of 6V to 300V. In order to keep the brightness of the LED light source 13 constant, the total power thereof should be approximately equivalent to the original non-high voltage case, and thus the current needs to be smaller than the original.
The embodiment of the invention provides two schemes for increasing the working voltage of the LED light source 13 to reduce the power consumption of the switching tube, and both schemes can be regarded as that the LED light source 13 adopts a high-voltage chip. Firstly, referring to fig. 6, m identical common non-high voltage LED chips D1-Dm are connected in series to form an LED light source 13, and the entire LED light source 13 is connected to a light emitting unit 10, where the operating voltage of the LED light source 13 is m times of the original operating voltage, and the current is also reduced to 1/m compared with a single common non-high voltage LED chip. Both schemes can improve the working voltage of the LED light source 13 while keeping the other performances (wavelength, total brightness, ESD, etc.) except the current intensity unchanged. Secondly, the LED Light source 13 increases the operating voltage of a high voltage LED (high voltage Light Emitting diode) chip with the same wavelength, for example, the high voltage LED chip to 18V, and the peak current is decreased to 2 mA. The high-voltage LED chip in the embodiment of the invention refers to that the working voltage V is more than 1.5 × hc/λ e, h is a Planck constant, c is the light speed, λ is the light-emitting wavelength of the LED chip, and e is the electronic quantity.
Referring to fig. 7, in the chip manufacturing stage of the high-voltage LED chip, the whole chip may be etched into m LED sub-chips with almost the same area, and the deposited metal is used to connect the sub-chips end to end, so as to connect the sub-chips in series, and finally lead out the positive electrode and the negative electrode. Each LED sub-chip is equivalent to a single common non-high voltage LED chip, and the brightness and the operating current of each LED sub-chip should be substantially equivalent, optionally, each LED sub-chip has the same area and similar structure.
Referring to fig. 8, in a still further embodiment, the LED light source 13 in the light emitting unit 10 includes more than two non-high voltage LED chips D1-Dm connected in series, or the LED light source 13 is a high voltage LED chip, and a resistor R1 is added to be connected in series with the second switching tube M2 for driving the LED light source 13, and the drain of the second switching tube M2 is grounded through the resistor R1, so that the current-voltage curve of the second switching tube M2 becomes more gradual, and for the same current variation range, the corresponding new voltage control range becomes larger, and higher-precision modulation can be implemented, so as to improve the gray scale control capability of the LED and reduce the power consumption of the second switching tube M2.
In practical applications, the current starts from 0 to its peak value, and the corresponding voltage ranges from the turn-on voltage to the peak voltage.As shown in FIG. 9, curve A3 shows the I of a switch tube driving a normal non-high voltage LED chip without a series resistords-VgsThe curve, the voltage range of which controls the gray scale is small. In FIG. 10, curve A5 shows the I of the switch tube driving the high voltage LED chip without the series resistords-VgsThe curve shows that the range of visible current is smaller, the voltage range for adjusting the gray scale is smaller, and the requirement for accurately controlling the gray scale is difficult to meet. And as in fig. 10, curve a6 is I of the series resistor and the switching tube for driving the high voltage LED chip according to the embodiment of the present inventionds-VgsIt can be seen that even after the current range is reduced, the voltage range thereof is still larger than that of the curve a3 in fig. 9, enabling more precise control of the gradation.
It should be noted that, with reference to fig. 8, in the technical scheme that the switching tube series resistor for driving the LED chip and the LED chip adopt the high-voltage chip, although a certain power is consumed by the series resistor, the total efficiency is still improved compared with the case that the series resistor and the LED chip do not adopt the common non-high-voltage chip. Here exemplified. For example, the voltage of a common non-high-voltage chip is 3V, the peak current is 12mA, the voltage of a high-voltage chip is 18V, the peak current is 2mA, the turn-on voltage of an MOS transistor is 2V, the intrinsic resistance of a turn-on region is 25Ohm, and the magnitude of a series resistance is 475 Ohm. Table one depicts the comparison of electrical parameters for these two cases. It can be seen that the voltage controllable range of the scheme of adopting the high-voltage chip by the LED chip is 3.3 times that of the scheme of adopting the non-high-voltage common chip, and the efficiency is 29.1 percent higher than that of adopting the non-high-voltage common chip, thereby not only improving the working voltage of the LED chip and reducing the energy consumption, but also keeping better gray control capability.
Table one: comparison of electrical parameters of non-high voltage LED scheme and high voltage LED scheme
Referring to fig. 11, a light emitting device according to an embodiment of the present invention includes the light emitting unit 10 according to any of the above embodiments and a package 40 for packaging the light emitting unit 10; the package 40 includes a power interface 41, a scan line interface 43, a data line interface 44, and a ground interface 42.
The positive electrode of the LED chip D1 is connected to the power interface 41 as the power source terminal of the light emitting unit 10, the gate of the first switch tube M1 is connected to the scan line interface 43 as the scan signal input terminal of the light emitting unit 10, the source of the first switch tube M1 is connected to the data line interface 44 as the data signal input terminal of the light emitting unit 10, and the source of the second switch tube M2 is connected to the ground interface 42 as the ground terminal of the light emitting unit 10.
Further, if the resistor R1 is further included, the source of the second switch M2 is connected to the first terminal of the resistor R1, and the second terminal of the resistor R1 is connected to the ground interface 42 as the ground terminal of the light emitting unit 10.
In the present embodiment, the number of pads on the printed circuit board is reduced by packaging the light emitting unit 10 in the package body 40. When the printed circuit board is welded, the more the bonding pads are, the more complex the wiring in the printed circuit board is, the more difficult the design is, and the higher the cost is, because the connection of the electronic components of the light-emitting unit 10 is fixed, the light-emitting unit 10 is packaged in the packaging body 40 to form a liquid crystal backlight source with a driving function, so that the purpose of adopting a built-in driving circuit to replace an external driving chip and a flat cable is achieved, each LED light source is controlled independently under the condition of not increasing the wiring density of the printed circuit board greatly, and the complexity of the driving circuit is not increased.
In one embodiment, the color of the LED chip D1 can be set according to the user's needs, the number of contacts of the light emitting unit 10 composed of discrete devices can be reduced from 8 to 4 by packaging the LED chip D1, the first switch tube M1 and the second switch tube M2, and the user can directly solder the packaged light emitting assembly onto the printed circuit board according to the needs, thereby simplifying the wiring design of the printed circuit board.
Referring to fig. 12, as another embodiment of the present invention, the package 40 further includes a capacitor interface 45, the capacitor interface 54 is connected to the drain of the first switch M1, in this embodiment, the storage capacitor C1 is externally disposed on the package 40, and the first end of the storage capacitor C1 is connected to the capacitor interface 45. The storage capacitor C1 is separated and arranged in the printed circuit board, so that a capacitor with large volume is avoided, and the volume of the light-emitting component is reduced.
Referring to fig. 13, a light emitting circuit according to an embodiment of the present invention includes a power line, a ground line, and a plurality of light emitting units 10 distributed in an array according to the above embodiments. Wherein, one data line is disposed for each row of light emitting cells 10, and one scanning line is disposed for each column of light emitting cells 10.
The gate of the first switching tube M1 of each light emitting cell 10 is connected to a corresponding scan line, the source of the first switching tube M1 of each light emitting cell 10 is connected to a corresponding data line, the positive electrode of the LED chip D1 of each light emitting cell 10 is connected to a power supply line, and the source of the second switching tube M2 of each light emitting cell 10 is connected to a ground line. Further, if the resistor R1 is included, the source of the second switch tube M2 is connected to the ground line through the resistor R1.
Referring to fig. 10 and 13, a light emitting circuit according to another embodiment of the present invention includes a power line, a ground line, and a plurality of light emitting elements arranged in an array as described in the above embodiments. Wherein, each row of light emitting components is provided with a data line, and each column of light emitting components is provided with a scanning line.
The scan line interface 43 of each light emitting assembly is connected to a corresponding scan line, the data line interface 44 of each light emitting assembly is connected to a corresponding data line, the power interface 41 of each light emitting assembly is connected to a power line, and the ground interface 42 of each light emitting assembly is connected to a ground line.
Referring to fig. 14, a display device 100 according to an embodiment of the invention includes a display panel 101 and a control unit 102. The display panel 101 includes a plurality of the above-described light emitting units 10; the control unit 102 is electrically connected to the display panel 101 and is configured to drive the display panel 101.
In one embodiment, the control Unit 102 may be implemented by a general-purpose Integrated Circuit, such as a Central Processing Unit (CPU), or an Application Specific Integrated Circuit (ASIC).
In one embodiment, the display panel 101 includes a pixel array composed of rows of pixels and columns of pixels.
Fig. 15 shows a flow of steps of a backlight control method according to the present invention, and for convenience of description, only the parts related to the present embodiment are shown, which are detailed as follows:
the backlight control method is used for a liquid crystal screen, the liquid crystal screen comprises a backlight unit and a display panel, and the backlight control method comprises the following steps:
s101, acquiring preset display brightness, and judging the strength relation between the preset display brightness and a dimming threshold;
in an embodiment, the dimming threshold is set to be a product of a maximum backlight transmittance and a preset light emitting luminance, where the maximum backlight transmittance is a maximum value of backlight transmittances in a plurality of backlight lattices provided for the display panel. In the display panel, a plurality of pixels (light emitting units) are provided, and each pixel is provided with a backlight transmittance, so that a plurality of backlight transmittances appear. A maximum value is selected among the plurality of backlight transmittances, i.e., defined as a maximum backlight transmittance.
S102, setting the brightness of the backlight unit according to the strength relation between preset display brightness and a dimming threshold;
because the brightness of the backlight unit is set according to the strength relation between the preset display brightness and the dimming threshold, the brightness of the backlight unit can be flexibly adjusted, namely dynamically changed. Specifically, when the preset display brightness is stronger than the dimming threshold, the light-emitting brightness of the backlight unit is a fixed value, and the screen adopts the same display mode as the traditional static backlight; when the preset display brightness is weaker than the dimming threshold, the light emitting brightness of the backlight unit changes in real time with the change of the preset display brightness, and then the screen should adopt a dynamic backlight algorithm. Referring to fig. 3, 4 and 5, the situation where the preset display brightness is stronger than the dimming threshold corresponds to the voltage V of the MOS transistor M2data0-V ofT1、VT2-Vmax static backlight area. Meanwhile, the case where the preset display brightness is weaker than the dimming threshold corresponds to the voltage V of the MOS transistor M2dataV ofT1-VT2In the static backlight area, due to the adoption of a dynamic backlight algorithm, the brightness of the backlight unit is flexibly adjusted, the gray scale adjustment precision is greatly improved, and the problem that the gray scale of an MOS tube in the static backlight area is difficult to control is solved.
And S103, setting the backlight transmittance of the display panel according to the preset display brightness and the set light emitting brightness.
Specifically, after the luminance of the backlight unit is set, the backlight transmittance of the display panel is obtained, and the two are in an inverse proportional relationship. In this embodiment, the quotient obtained by dividing the preset display brightness value by the set brightness value is used to obtain the backlight transmittance of the display panel and set the backlight transmittance, which is specifically obtained by the following formula:
T＝L/B
wherein, T is the backlight transmittance of the display panel, L is the preset display brightness, and B is the set brightness.
Because the brightness of the backlight unit can be flexibly adjusted, the backlight transmissivity of the display panel is correspondingly changed along with the brightness of the backlight unit, the effect of stronger flexibility of the control method is achieved, the contrast of a screen is improved, and the user experience is stronger.
In an embodiment, the setting and the operation principle of the static backlight area and the dynamic backlight area are described with reference to fig. 3 to 9:
when dynamic dimming is performed by the circuit structures of fig. 3, 6 and 7, taking the circuit structure of fig. 3 as an example, it can be seen from the Ids-Vgs relationship curve a2 of the discrete MOS transistor M2 of fig. 4 that the IV curve has a large dynamic resistance when the current is small and large, that is, the variation range of Vgs is large in the process of Ids variation; conversely, when the current magnitude is in the middle region, the dynamic resistance is smaller. The brightness and driving voltage of the backlight unit are combined with FIG. 5 (FIG. 5 adopts V)dataIs shown, and VdataEquivalent to Vgs in fig. 4), a driving voltage is used to drive the above dynamic backlight liquid crystal panel, and the curve model is divided into a static backlight region and a dynamic backlight region according to the slope magnitude of the curve,that is, when the slope of the curve is greater than a first preset angle value or less than a second preset angle value, dividing the corresponding region into the static backlight region; when the slope of the curve is between a first preset angle value and a second preset angle value, dividing a corresponding region into the dynamic backlight region, and correspondingly acquiring the gray-scale value of the luminous brightness in the dynamic backlight region according to the change of the driving voltage. The light emission luminance corresponding to the boundary point between the static backlight region and the dynamic backlight region is set to a preset light emission luminance (fig. 5 adopts B)T1、BT2Representation).
Therefore, the light-emitting brightness is controlled by the driving voltage in the static backlight area with a steep curve close to the maximum current and the static backlight area with a close to zero current, the errors are large, and the light-emitting brightness deviation caused by the errors brought by the driving voltage is more sensitive in the static backlight area than in the dynamic backlight area, namely when the driving voltage changes a little in the static backlight area, the light-emitting brightness can be greatly changed. From the above analysis, it can be seen that the error is large when the luminance B of the LED is controlled in the static backlight region, and the accuracy is relatively high when the control is implemented in the dynamic backlight region. Therefore, the driving voltage corresponding to the boundary of the static backlight area and the dynamic backlight area is defined as VT1、VT2I.e. when the Vgs voltage is at VT1-VT2In the meantime, the dynamic resistance of the MOS transistor M2 is large, so that the current can be accurately controlled, and the corresponding luminous brightness is BT1、BT2. On the contrary, when the Vgs voltage is less than VT1Or greater than VT2In time, the dynamic resistance of the MOS transistor M2 is small, and the current cannot be accurately controlled.
Therefore, the static backlight area and the dynamic backlight area are set, and different display control methods are respectively adopted for the static backlight area and the dynamic backlight area:
in the static backlight area, the display mode of the traditional static backlight is adopted as long as the driving voltage is less than VT1Or greater than VT2The light emission luminance is set to a fixed value, for example, the light emission is performedThe brightness is fixed to correspond to B in FIG. 5T1And Bmax;
in the dynamic backlight area, a display mode of dynamic backlight is adopted, namely, the driving voltage VT1-VT2In between, the gray-scale value of the luminance is correspondingly obtained according to the change of the driving voltage, for example: when the driving voltage is VT1at-V7, the brightness of the light is BT1-B7; … … when the driving voltage is V8, the brightness of the light is Bx; when the driving voltage is VT2When it is, the luminance is BT2. Therefore, in the dynamic backlight area, the light emitting brightness can be flexibly adjusted, namely dynamically changed.
The static backlight area corresponds to a case where the preset display luminance is stronger than the dimming threshold, and the dynamic backlight area corresponds to a case where the preset display luminance is weaker than the dimming threshold.
Further, referring to fig. 5, compared to the conventional dynamic backlight area: driving voltage at VT1-VxAnd static backlight area: driving voltage at Vx-Vmax. After the MOS transistor M2 is serially connected with the resistor, the range of the dynamic backlight area is widened to be at the driving voltage V based on the control mode of the backlight control method to the static backlight area and the dynamic backlight areaT1-VT2Between the slave drive voltage at VxExtending to VT2The light-emitting brightness of the display device can be flexibly adjusted in a wider range. But also in the conventional dynamic backlight area (driving voltage at V in fig. 5)T1-VxIn range) is more gradual, resulting in higher adjustment accuracy.
As an embodiment of the present invention, the control method is a coordinated dimming method between an LCD (Liquid Crystal Display) panel and an LED backlight array, and solves a problem that a discrete MOS transistor is difficult to control a gray scale in a static backlight area. Meanwhile, in a dynamic backlight area, a dynamic dimming mode is adopted, wherein the dynamic dimming mode refers to that the LCD array and the backlight LED array are used for controlling the gray scale at the same time, the mode can overcome the defect of backlight light leakage of a liquid crystal screen, and the contrast of the screen is improved.
Fig. 16 shows a specific implementation flow of a backlight control method according to the present invention, and for convenience of description, only the relevant portions of the embodiment are shown, which are detailed as follows:
as an embodiment of the present invention, the step S102 further includes the following steps:
s1021, when the preset display brightness is higher than the dimming threshold, setting the brightness to be first brightness;
in one embodiment, the first light-emitting brightness is a maximum value of light-emitting brightness of a plurality of backlight lattices provided for the backlight unit. In the backlight unit, a plurality of backlight lattices are provided, and each backlight lattice is provided with a corresponding light-emission luminance, and thus, a plurality of light-emission luminances appear. The maximum value is selected among a plurality of light emission luminances, i.e., defined as a first light emission luminance, i.e., corresponding to B in fig. 5T1And Bmax.
And S1022, when the preset display brightness is weaker than the dimming threshold, setting the brightness to be a second brightness, and regulating and controlling the pixel gray level.
In one embodiment, the second luminance is a square root of a product of the predetermined display luminance and the predetermined luminance and a quotient of the product and the maximum backlight transmittance, which is obtained by the following formula:
B＝sqrt(L*BT/Tmax)
wherein L is the preset display brightness, BTFor presetting the brightness, TmaxSqrt is the square root for maximum backlight transmittance.
Furthermore, under the condition of lower preset display brightness, the brightness of the display panel and the backlight unit can be regulated and controlled simultaneously to regulate and control the gray level of the pixels, so that the problem of light leakage of liquid crystals is avoided, and very low display brightness can be realized.
The specific implementation flow of the backlight control method is as follows:
firstly, acquiring preset display brightness, and judging whether the preset display brightness is stronger than a dimming threshold value; if so, setting the brightness of the backlight unit to be first brightness which is fixed and unchanged; if not, the light-emitting brightness of the backlight unit is set to be a second light-emitting brightness which can be flexibly adjusted; and finally, according to the preset display brightness and the set luminous brightness, the preset display brightness and the set luminous brightness are subjected to division and quotient calculation to obtain the backlight transmittance of the display panel and set.
By the backlight control method, the relationship between the preset display brightness and the dimming threshold is judged by acquiring the preset display brightness; setting the brightness of the backlight unit according to the strength relation between the preset display brightness and the dimming threshold; and further setting the backlight transmittance of the liquid crystal unit according to the preset display brightness and the set light-emitting brightness. Therefore, different luminance and backlight transmittance are correspondingly set according to the strength relation between the preset display brightness and the dimming threshold, and the problem that the gray scale of a static backlight area of the discrete MOS tube is difficult to control is solved; the flexibility of this control mode is stronger, has promoted the contrast of screen, and user's experience feels stronger.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (5)
1. A backlight control method is used for a liquid crystal screen, the liquid crystal screen comprises a backlight unit and a display panel, the display panel comprises a plurality of light-emitting units, the backlight control method is characterized by comprising a first switch tube, a second switch tube, an LED light source and a first storage capacitor, wherein:
the grid electrode of the first switch tube is a scanning signal input end, the source electrode of the first switch tube is a data signal input end, the drain electrode of the first switch tube is connected with the grid electrode of the second switch tube and the first end of the first storage capacitor, the second end of the first storage capacitor is grounded, the drain electrode of the second switch tube is connected with the negative electrode of the LED light source, the positive electrode of the LED light source is a power signal input end, the source electrode of the second switch tube is grounded, and the LED light source comprises more than two non-high-voltage LED chips connected in series or is a high-voltage LED chip;
the backlight control method comprises the following steps:
acquiring preset display brightness, and judging the strength relation between the preset display brightness and a dimming threshold;
setting the brightness of the backlight unit according to the strength relation between preset display brightness and a dimming threshold;
setting the backlight transmittance of the display panel according to the preset display brightness and the set light-emitting brightness;
the setting of the brightness of the backlight unit according to the relationship between the preset display brightness and the dimming threshold value includes:
when the preset display brightness is higher than the dimming threshold, setting the brightness to be first brightness, wherein the first brightness is the maximum value of the brightness of the backlight unit in a plurality of backlight dot matrixes;
when the preset display brightness is weaker than the dimming threshold, the light-emitting brightness is set to be a second light-emitting brightness, and the pixel gray scale is regulated and controlled; the second luminance is a square root of a product of the preset display luminance and the preset luminance and a quotient of the product and the maximum backlight transmittance.
2. The backlight control method of claim 1, wherein the light emitting unit further comprises a resistor, and the source of the second switching tube is grounded through the resistor.
3. The backlight control method of claim 2, wherein the resistance has a value in a range of 2 x 100Ohm to 2 x 103Ohm。
4. The backlight control method of claim 1, wherein the light emitting unit is disposed on a printed circuit board, the printed circuit board including a first printed circuit board layer provided with a first metal electrode and a second printed circuit board layer provided with a second metal electrode, the first metal electrode and the second metal electrode being in one-to-one correspondence and being disposed opposite to each other to form the first storage capacitor; the first metal electrode is used as a first end of the first storage capacitor, and the second metal electrode is used as a second end of the first storage capacitor.
5. The backlight control method of claim 1, wherein the first switching tube is disposed in a thin film transistor backplane, and the second switching tube is soldered to the thin film transistor backplane.
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| CN112908248A (en) * | 2021-03-02 | 2021-06-04 | 深圳市华星光电半导体显示技术有限公司 | Pixel driving circuit and display panel |
| CN113257173A (en) * | 2021-03-29 | 2021-08-13 | 北海惠科光电技术有限公司 | Active light-emitting device, display panel and splicing display device |
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