Background
With the continuous development of display technology, the application of liquid crystal display devices is becoming more and more extensive, and when a liquid crystal display device displays a picture, a processor in the liquid crystal display device generally firstly analyzes a video signal from a video signal source, then outputs a frame frequency signal obtained after analysis to a microcontroller on a backlight driving board in the liquid crystal display device, and simultaneously the processor also outputs a backlight data signal carried by the frame frequency signal to the microcontroller; then the microcontroller carries out frequency multiplication operation on the frame frequency signal to obtain a frame synchronization signal and a synchronous backlight data signal carried by the frame synchronization signal, and the microcontroller outputs the frame synchronization signal and the synchronous backlight data signal to a light emitting diode control chip on a backlight driving board; finally, the led control chip outputs a corresponding Pulse Width Modulation (PWM) signal according to the frame synchronization signal and the synchronous backlight data signal to drive the led unit to emit light.
Referring to fig. 1, when a user watches a video image through a liquid crystal display device, a video signal source of the liquid crystal display device may be changed at any time according to needs, and video signals provided by different video signal sources have different frequencies; in order to avoid the phenomenon of flicker of the video signal provided by the conventional video signal source, which is easily captured by human eyes when different display screens are switched, in the prior art, the microcontroller 3 generally multiplies the frequency of the received frame frequency signal by twice the frequency of the frame frequency signal to obtain a frame synchronization signal with a higher frequency, but the frame frequency signals with different frequencies are switched, so that the frame synchronization signal with a higher frequency generated by the microcontroller 3 is easily disturbed by the frequency disturbance, and thus the PWM signal is disturbed, further the driving signal for driving the light emitting diode unit 5 to emit light with higher brightness is disturbed, and the light emitting diode unit 5 is easily emitted with higher brightness in the working process, thereby bringing discomfort to people.
Referring to fig. 2, a detailed analysis is performed below with reference to a specific example to solve a problem that the light emitting diode unit 5 is prone to emit light with high brightness during the operation process, which is caused by a disorder of the driving signal for driving the light emitting diode unit 5 in the prior art.
The microcontroller 3 receives the 60Hz frame frequency signal Vsync1 and the 50Hz frame frequency signal Vsync1 in sequence, and multiplies the received frame frequency signal Vsync1 by twice the frequency of the frame frequency signal Vsync1 itself to obtain a 120Hz frame synchronization signal Vsync2 and a 100Hz frame synchronization signal Vsync2, as can be seen from fig. 2, after receiving the frame frequency signal Vsync1 corresponding to the point B, the microcontroller 3 multiplies the frequency of the frame frequency signal Vsync1 corresponding to the point B by the frame synchronization signal Vsync2 of 120Hz (corresponding to the point D and the point E in fig. 2); since the frequency of frame frequency signal Vsync1 received by microcontroller 3 is switched from 60Hz to 50Hz at point B, that is, the period of frame frequency signal Vsync1 received by microcontroller 3 after point B is longer, microcontroller 3 cannot receive frame frequency signal Vsync1 corresponding to point C in time after frequency doubling frame frequency signal Vsync1 corresponding to point B to frame synchronization signal Vsync2 corresponding to point D and point E, so that microcontroller 3 outputs frame synchronization signal Vsync2 (corresponding to point F in fig. 2) with the same frequency as frame synchronization signal Vsync2 corresponding to point D and point E by default, and then microcontroller 3 receives frame frequency signal Vsync1 corresponding to point C at 50Hz and frequency doubling frame synchronization signal Vsync2 (corresponding to point G in fig. 2) corresponding to point C.
As can be seen from the above analysis process, during the switching process of the frame frequency signals Vsync1 with different frequencies, the microcontroller 3 may generate an abnormal frame synchronization signal Vsync2 (corresponding to point F in fig. 2), and the led control chip may output a corresponding PWM signal according to the received frame synchronization signal Vsync2, so that after the led control chip receives the frame synchronization signal Vsync2 corresponding to point F, the led control chip correspondingly outputs a PWM signal corresponding to point H, because the led control chip receives the frame synchronization signal Vsync2 corresponding to point G soon, the led control chip immediately outputs a PWM signal corresponding to point G, and the frame synchronization signal Vsync2 corresponding to point F and point G has a higher frequency, so that the led control chip correspondingly outputs a series of high frequency signals corresponding to point I after point H; when the light emitting diode unit 5 is driven to emit light by the PWM signal, the light emitting diode unit 5 emits light with high luminance in the time period from the point H to the point I because the part of the PWM signal corresponding to the point H to the point I has high frequency, so that human eyes perceive the flickering phenomenon of the picture display, which brings discomfort to people watching.
Disclosure of Invention
The invention aims to provide a liquid crystal display device and a backlight control method thereof, which are used for solving the problem that the display screen flicker can be perceived by human eyes due to the uneven brightness of the screen displayed by the liquid crystal display device caused by the change of the frequency of a received video signal.
In order to achieve the above purpose, the invention provides the following technical scheme:
a liquid crystal display device comprises a processor, a microcontroller and a light emitting diode control chip, wherein the processor is electrically connected with the microcontroller; wherein,
the processor is configured to optionally output a plurality of frame rate signals, at least two of the frame rate signals having different frequencies;
the microcontroller is configured to generate a plurality of frame synchronization signals having a first signal frequency that is a common multiple of the frequencies of at least two different ones of the plurality of frame frequency signals;
the light emitting diode control chip is configured to generate a PWM signal at the first signal frequency.
Preferably, the first signal frequency is a least common multiple of frequencies of at least two different frame frequency signals of the plurality of frame frequency signals.
Preferably, the first signal frequency is a least common multiple of frequencies of the plurality of frame frequency signals.
Further, the microcontroller is configured to generate a plurality of frame synchronization signals having the first signal frequency, while the microcontroller correspondingly outputs a plurality of synchronized backlight data signals.
Further, the led control chip controls the frequency of the PWM signal according to the frame synchronization signal, and controls the duty ratio of the PWM signal according to the synchronous backlight data signal.
The invention also provides a backlight control method of a liquid crystal display device, wherein the liquid crystal display device comprises a processor, a microcontroller and a light emitting diode control chip, the processor is electrically connected with the microcontroller, the microcontroller is electrically connected with the light emitting diode control chip, and the backlight control method comprises the following steps:
the processor analyzes the video signals to correspondingly obtain a plurality of frame frequency signals, and the frequency of at least two of the frame frequency signals is different;
the microcontroller performs frequency multiplication operation on the plurality of frame frequency signals according to a first signal frequency to correspondingly obtain a plurality of frame synchronization signals with the first signal frequency, wherein the first signal frequency is a common multiple of the frequencies of at least two frame frequency signals with different frequencies in the plurality of frame frequency signals;
and the light-emitting diode control chip correspondingly generates a PWM signal with a first signal frequency according to the plurality of frame synchronization signals.
Preferably, the first signal frequency is a least common multiple of frequencies of the plurality of frame frequency signals.
Further, the processor obtains a plurality of backlight data signals corresponding to the plurality of frame frequency signals one to one while obtaining the plurality of frame frequency signals; the microcontroller obtains a plurality of synchronous backlight data signals corresponding to the plurality of frame synchronization signals one by one while obtaining the plurality of frame synchronization signals; and the light-emitting diode control chip controls the frequency of the PWM signal according to the frame synchronization signal and controls the duty ratio of the PWM signal according to the synchronous backlight data signal.
Further, the processor comprises a main board and a screen driving board; the main board is used for analyzing the video signals to obtain a plurality of target signals corresponding to the video signals one by one; the screen driving board is used for analyzing the plurality of target signals to obtain a plurality of frame frequency signals and backlight data signals which are in one-to-one correspondence with the plurality of target signals.
Compared with the prior art, the invention has the beneficial effects that:
in the liquid crystal display device provided by the invention, because the frequencies of at least two frame frequency signals in the plurality of frame frequency signals output by the processor are different, and after the microcontroller receives the plurality of frame frequency signals, the plurality of frame frequency signals can be multiplied according to the common multiple of the frequencies of at least two frame frequency signals with different frequencies in the plurality of frame frequency signals, namely, a plurality of frame synchronization signals with first signal frequency are generated, and then the microcontroller outputs the generated plurality of frame synchronization signals to the light emitting diode control chip; under the condition, the plurality of frame synchronizing signals received by the light-emitting diode control chip are signals with stable periods, so that a plurality of PWM signals correspondingly generated by the light-emitting diode control chip according to the plurality of frame synchronizing signals have the same frequency, and then the driving signals for driving the light-emitting diode unit to emit light are generated according to the plurality of PWM signals with the same frequency, so that the driving signals are ensured to be the signals with stable periods, the brightness of the light emitted by the light-emitting diode unit is uniform, the phenomenon that a display picture flickers can be perceived by human eyes can not occur, and the comfortable feeling of people when watching the display picture is met.
Detailed Description
To further explain the liquid crystal display device and the backlight control method thereof provided by the embodiments of the present invention, the following detailed description is made with reference to the accompanying drawings.
Referring to fig. 1, a liquid crystal display device according to an embodiment of the present invention includes a processor, a microcontroller 3, and a light emitting diode control chip 4, wherein the processor is electrically connected to the microcontroller 3, and the microcontroller 3 is electrically connected to the light emitting diode control chip 4; wherein the processor is configured to optionally output a plurality of Vsync signals 1 and to transmit a plurality of Vsync signals 1 to the microcontroller 3, and at least two of the plurality of Vsync signals 1 have different frequencies from each other, such that the frequency of each of the plurality of Vsync signals Vsync1 is different; specifically, the frequencies of the video signals sent by different video signal sources are not exactly the same, and when the processor receives a plurality of video signals with non-exactly the same frequencies, the frequencies of the plurality of frame frequency signals Vsync1 that correspond to the analyzed frequencies are not exactly the same.
The microcontroller 3 is configured to generate a plurality of frame synchronization signals Vsync2 having a first signal frequency that is a common multiple of frequencies of at least two frame frequency signals Vsync1 of different frequencies among the plurality of frame frequency signals Vsync1, and transmit the plurality of frame synchronization signals Vsync2 to the light emitting diode control chip 4; in more detail, after receiving the frame frequency signals Vsync1 with different frequencies, the microcontroller 3 may perform a frequency doubling operation on the frame frequency signals Vsync1 according to a common multiple of the frequencies of at least two frame frequency signals Vsync1 with different frequencies in the frame frequency signals Vsync1 to obtain a plurality of frame synchronization signals Vsync2 with the first signal frequency, and then the microcontroller 3 transmits the frame synchronization signals Vsync2 to the led control chip 4.
The led control chip 4 is configured to generate a plurality of PWM signals of the same frequency at the first signal frequency. Further, the led control chip 4 is capable of generating a plurality of PWM signals having the same frequency at the first signal frequency according to the plurality of frame synchronization signals Vsync2 after receiving the plurality of frame synchronization signals Vsync2 having the first signal frequency, and generating a driving signal according to the PWM signals to drive the led unit 5 functioning as a backlight in the liquid crystal display device to emit light.
In the liquid crystal display device provided by the embodiment of the invention, because at least two of the frame frequency signals Vsync1 in the plurality of frame frequency signals Vsync1 output by the processor have different frequencies, and after receiving the plurality of frame frequency signals Vsync1, the microcontroller 3 can multiply the frequency of the plurality of frame frequency signals Vsync1 by a common multiple of the frequencies of at least two frame frequency signals Vsync1 with different frequencies in the plurality of frame frequency signals Vsync1, that is, generate a plurality of frame synchronization signals Vsync2 with a first signal frequency, and then the microcontroller 3 outputs the generated plurality of frame synchronization signals Vsync2 to the light emitting diode control chip 4; in this case, the plurality of frame synchronization signals Vsync2 received by the led control chip 4 are signals with a stable period, so that the plurality of PWM signals generated by the led control chip 4 according to the plurality of frame synchronization signals Vsync2 have the same frequency, and then the driving signal for driving the led unit 5 to emit light is generated according to the plurality of PWM signals with the same frequency, which ensures that the driving signal is a signal with a stable period, so that the luminance brightness emitted by the led unit 5 is uniform, the phenomenon of flicker of the display image perceived by human eyes does not occur, and the comfort of people viewing the display image is satisfied.
In the frequency doubling operation performed by the microcontroller 3 according to the above embodiment, it is preferable that the first signal frequency of the plurality of frame synchronization signals Vsync2 is a least common multiple of the frequencies of at least two frame frequency signals Vsync1 with different frequencies in the plurality of frame frequency signals Vsync1, that is, the microcontroller 3 performs the frequency doubling operation on the plurality of frame frequency signals Vsync1 according to the least common multiple of the frequencies of at least two frame frequency signals Vsync1 with different frequencies in the plurality of frame frequency signals Vsync 1. More preferably, the plurality of frame synchronization signals Vsync2 have a first signal frequency that is the least common multiple of the frequencies of the plurality of frame frequency signals Vsync1, i.e., the microcontroller 3 multiplies the plurality of frame frequency signals Vsync1 by the least common multiple of the frequencies of the plurality of frame frequency signals Vsync 1. Since the led control chip 4 generates a plurality of PWM signals of the same frequency at the first signal frequency according to the received frame synchronization signals Vsync2, and the frequency of the PWM signals is used to control the light emitting frequency of the led unit 5 in the lcd device, that is, when the frequency of the PWM signals is higher, the light emitting frequency of the led unit 5 is higher, which has an influence on the service life of the led unit 5; and the multiple frame frequency signals Vsync1 are frequency-doubled according to the least common multiple of the frequencies of the multiple frame frequency signals Vsync1, so that the frequencies of the multiple frame synchronization signals Vsync2 are reduced to the maximum extent on the premise of ensuring that the multiple frame synchronization signals Vsync2 have the same frequency, thereby reducing the frequency of the PWM signal and enabling the light-emitting diode unit 5 to have longer service life. The common multiple obtaining method mentioned in the above embodiments is various, and a specific method is given below to describe the common multiple obtaining in detail.
Referring to fig. 3, the method for obtaining the common multiple includes the following steps:
step 101, extracting time corresponding to each rising edge in a plurality of frame frequency signals Vsync 1; specifically, each of the frame frequency signals Vsync1 and Vsync1 includes several rising edges, and the time corresponding to each of the rising edges of the frame frequency signals Vsync1 is extracted.
Step 102, counting the time interval between two adjacent rising edges; in more detail, the time interval between every two adjacent rising edges is counted according to the time corresponding to each rising edge extracted in step 101, so as to obtain the period corresponding to each frame frequency signal Vsync1 in the plurality of frame frequency signals Vsync1, and thus obtain the frequency corresponding to each frame frequency signal Vsync1 in the plurality of frame frequency signals Vsync 1.
103, obtaining a frequency corresponding to each frame frequency signal Vsync1 in a plurality of frame frequency signals Vsync1 according to a plurality of time intervals, and obtaining a common multiple according to a frequency corresponding to each frame frequency signal Vsync1 in a plurality of frame frequency signals Vsync 1; further, a common multiple is calculated according to the frequency corresponding to each frame frequency signal Vsync1 in the plurality of frame frequency signals Vsync1 obtained in step 102, and preferably, the common multiple is the smallest common multiple; and then, frequency multiplication is carried out on the multiple frame frequency signals Vsync1 according to the least common multiple.
Notably, the microcontroller 3 is configured to generate a plurality of frame synchronization signals Vsync2 with the first signal frequency, while the microcontroller 3 correspondingly outputs a plurality of synchronized backlight data signals SDI2 to the led control chip 4; the plurality of synchronous backlight data signals SDI2 are carried by the plurality of frame synchronization signals Vsync2 in a one-to-one correspondence; the frame synchronization signals Vsync2 correspond to identification signals, that is, when the synchronization backlight data signal SDI2 is extracted, the required synchronization backlight data signal SDI2 can be accurately found and extracted only by finding the identification signal corresponding to the synchronization backlight data signal SDI 2.
Further, when the light emitting diode control chip 4 generates a plurality of PWM signals of the same frequency at the first signal frequency, the light emitting diode control chip 4 controls the frequency of the PWM signals according to the frame sync signal Vsync2 while controlling the duty ratio of the PWM signals according to the synchronized backlight data signal SDI 2. More specifically, the frequency of the PWM signal is controlled by the frame synchronization signal Vsync2, and the frequency of the PWM signal is used to control the light emission frequency of the light emitting diode unit 5 serving as a backlight in the liquid crystal display device, so that the light emission frequency of the light emitting diode unit 5 is synchronized with the refresh operation of the screen to be displayed by the liquid crystal display device; the duty cycle of the PWM signal is controlled by the synchronized backlight data signal SDI2, and the duty cycle of the PWM signal affects the brightness of the light emitted by the led unit 5, so that the led unit 5 can emit light with different brightness according to the requirements of the displayed video image.
The embodiment of the invention also provides a backlight control method of the liquid crystal display device, the liquid crystal display device comprises a processor, a microcontroller 3 and a light emitting diode control chip 4, the processor is electrically connected with the microcontroller 3, and the microcontroller 3 is electrically connected with the light emitting diode control chip 4; the processor analyzes the plurality of video signals to obtain a plurality of frame frequency signals Vsync1 correspondingly, at least two frame frequency signals Vsync1 in the plurality of frame frequency signals Vsync1 have different frequencies, and the processor outputs the plurality of analyzed frame frequency signals Vsync1 to the microcontroller 3.
The microcontroller 3 performs a frequency doubling operation on the plurality of frame frequency signals Vsync1 according to a first signal frequency to correspondingly obtain a plurality of frame synchronization signals Vsync2 with the first signal frequency, the first signal frequency is a common multiple of the frequencies of at least two frame frequency signals Vsync1 with different frequencies in the plurality of frame frequency signals Vsync1, and the microcontroller 3 outputs the plurality of frame synchronization signals Vsync2 with the first signal frequency to the light emitting diode control chip 4.
The light emitting diode control chip 4 correspondingly generates a plurality of PWM signals having the same frequency according to the plurality of frame synchronization signals Vsync 2; the generated PWM signal may be used as a driving signal of the field effect transistor, thereby driving the light emitting diode unit 5 connected to the field effect transistor to emit light.
In the backlight control method of the liquid crystal display device provided in the embodiment of the present invention, because at least two frame frequency signals Vsync1 in the plurality of frame frequency signals Vsync1 output by the processor have different frequencies, and after receiving the plurality of frame frequency signals Vsync1, the microcontroller 3 can double the frequency of the plurality of frame frequency signals Vsync1 according to a common multiple of the frequencies of at least two frame frequency signals Vsync1 with different frequencies in the plurality of frame frequency signals Vsync1, that is, generate a plurality of frame synchronization signals Vsync2 with a first signal frequency, and then the microcontroller 3 outputs the generated plurality of frame synchronization signals Vsync2 to the led control chip 4; in this case, the plurality of frame synchronization signals Vsync2 received by the led control chip 4 are signals with a stable period, so that the plurality of PWM signals generated by the led control chip 4 according to the plurality of frame synchronization signals Vsync2 have the same frequency, and then the driving signal for driving the led unit 5 to emit light is generated according to the plurality of PWM signals with the same frequency, which ensures that the driving signal is a signal with a stable period, so that the luminance brightness emitted by the led unit 5 is uniform, the phenomenon of flicker of the display image perceived by human eyes does not occur, and the comfort of people viewing the display image is satisfied.
Preferably, the common multiple provided by the above embodiments is the least common multiple of the frequencies of the frame frequency signals Vsync1, so that the frequencies of the frame synchronization signals Vsync2 are reduced to the maximum extent on the premise of ensuring that the frame synchronization signals Vsync2 have the same frequency, thereby reducing the frequency of the PWM signals and prolonging the service life of the light emitting diode unit 5.
The processor obtains a plurality of backlight data signals SDI1 corresponding to the plurality of frame frequency signals Vsync1 one by one while obtaining a plurality of frame frequency signals Vsync 1; the plurality of backlight data signals SDI1 are carried by the plurality of frame frequency signals Vsync1 in a one-to-one correspondence; the frame frequency signals Vsync1 correspond to identification signals, that is, when the backlight data signal SDI1 is extracted, only the identification signal corresponding to the frame frequency signals SDI1 needs to be found, and the required backlight data signal SDI1 can be accurately found and extracted.
The microcontroller 3 obtains a plurality of frame synchronization signals Vsync2 and a plurality of synchronous backlight data signals SDI2 corresponding to the plurality of frame synchronization signals Vsync2 one by one; the plurality of synchronous backlight data signals SDI2 are carried by the plurality of frame synchronization signals Vsync2 in a one-to-one correspondence; and the synchronized backlight data signal SDI2 is only changed in frequency compared to the backlight data signal SDI1 while the data controlling the brightness of the light emitted by the led units 5 is not changed.
The light emitting diode control chip 4 controls the frequency of the PWM signal according to the frame sync signal Vsync2, while controlling the duty ratio of the PWM signal according to the synchronized backlight data signal SDI 2.
The processor provided by the above embodiment may include a motherboard 1 and a screen driving board 2, and may also be only the motherboard 1; when the processor comprises a main board 1 and a screen driving board 2, the main board 1 is used for analyzing a plurality of video signals to obtain a plurality of target signals (the plurality of target signals may be all VBO signals or all LVDS signals) corresponding to the plurality of video signals one to one; the panel driving board 2 is configured to analyze the plurality of target signals to obtain a plurality of frame frequency signals Vsync1 and backlight data signals SDI1 corresponding to the plurality of target signals one to one. When the processor is only the main board 1, the main board 1 needs to have a function of correspondingly analyzing a plurality of video signals into a plurality of frame frequency signals Vsync1 and a backlight data signal SDI 1. The specific configuration of the processor can be selected according to the actual needs, and is not limited in other aspects.
In order to more clearly describe the change of the PWM signal during the switching process of the video signals with different frequencies provided by the embodiment of the present invention, the following preferred embodiments are given:
referring to fig. 4, when the processor sequentially outputs a first frame frequency signal Vsync11 with a frequency of 60Hz and a second frame frequency signal Vsync12 with a frequency of 50Hz, after a frequency doubling operation is performed according to a least common multiple 300 of 50Hz and 60, the frequencies of the obtained first frame synchronization signal Vsync21 and the second frame synchronization signal Vsync22 are both 300Hz, so that the led control chip 4 makes the PWM signals be signals with a stable period when generating the PWM signals according to the first frame synchronization signal Vsync21 and the second frame synchronization signal Vsync22, thereby well ensuring that the driving signals for driving the led unit 5 to emit light are signals with a stable period, and well avoiding the problem that the luminance of the image displayed by the lcd device is not uniform due to the frequency change of the received video signals, and the flicker of the displayed image can be perceived by human eyes.
For example, referring to fig. 1 and 4, the microcontroller 3 is configured to output a first frame sync signal Vsync21 and a second frame sync signal Vsync22 at a fixed frequency of 300 Hz. Specifically, after the microcontroller 3 receives the 60Hz frame frequency signal a0, the microcontroller 3 performs frequency multiplication by 5 times to output 300Hz frame synchronization signals a1, a2, A3, a4 and a5, after the microcontroller 3 receives the 50Hz frame frequency signal B0, although the signal frequency after the frame frequency signal B0 is 50Hz, before the frame frequency signal C0 is not received, the microcontroller 3 performs frequency multiplication on the signal frequency between the previous frames a0 and B0, that is, the microcontroller 3 defaults to the frame frequency signal B0 being 60Hz, the microcontroller 3 outputs the frame synchronization signals B1, B2, B3, B4 and B5 according to the frame frequency signal B0, after the microcontroller 3 outputs the frame synchronization signal B5, the frame synchronization signal B1/300 seconds is passed and is output, but the frame frequency signal C0 is still not received, at this time, the microcontroller outputs a frame synchronization signal B6 again according to the frame frequency signal B0, and then 1/300 seconds are passed, the microcontroller 3 receives the frame frequency signal C0 and outputs synchronous frame frequency signals C1, C2, C3, C4, C5, and C6 according to the frame frequency signal C0. Referring to fig. 4, the frequency between the frame synchronization signal B6 and the frame synchronization signal C1 is completely the same as the frequency of the frame synchronization signal output by the microcontroller 3, so as to ensure the periodic stability of the light-emitting driving signal of the light-emitting diode unit 5, and well avoid the problem that human eyes can perceive the flicker of the displayed image due to the uneven brightness of the image displayed by the liquid crystal display device caused by the change of the frequency of the received video signal.
Referring to fig. 5, when the processor sequentially outputs a first frame frequency signal Vsync11 with a frequency of 50Hz and a second frame frequency signal Vsync12 with a frequency of 60Hz, the microcontroller 3 performs frequency doubling according to the least common multiple 300 of 50Hz and 60, and then outputs a first frame synchronization signal Vsync21 and a second frame synchronization signal Vsync22 with stable periods at 300Hz, and meanwhile, the led control chip 4 also outputs a PWM signal with stable periods, thereby well avoiding the problem that human eyes can perceive flicker of a display screen due to uneven brightness of a screen displayed by the lcd device caused by the change of the frequency of the received video signal.
In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.