CN103093727B - Backlight control signal method of adjustment and device - Google Patents

Abstract

The invention discloses a method and device for adjusting a backlight control signal. The method comprises: obtaining the frequency of the scanning signal and the screen parameters of the liquid crystal display; determining the frequency of the current PWM signal according to the frequency of the scanning signal; The screen parameters of the display screen determine the high-level part and low-level part of the current PWM signal, as well as the trigger time of the rising edge of the current PWM signal; when the trigger time of the rising edge of the current PWM signal arrives, a PWM signal period is triggered The rising edge of the internal PWM signal, and output the PWM signal according to the frequency, high level part and low level part of the current PWM signal. The present invention avoids the phase shift between the PWM signal and the scanning signal due to the frequency mismatch between the two, or the pinch pressure change at both ends of the liquid crystal caused by the polarity reversal of the PWM signal on the liquid crystal glass of the liquid crystal display, effectively avoiding the liquid crystal display Scrolling water ripples appear on the screen. <!--1-->

Description

Backlight control signal adjustment method and device

technical field

The invention relates to the field of liquid crystal technology, in particular to a backlight control signal adjustment method and device.

Background technique

Currently, LCD TVs on the market have become the mainstream and are growing at a high speed. Most of the LCD screens of LCD TVs use LED or cold-cathode lamps as the backlight. The LCD TV uses a PWM signal with a fixed frequency to control the switch of the backlight of the LCD screen from the counting control register. By adjusting this PWM duty cycle to adjust the brightness of the backlight. The system main board of the LCD TV provides a scan signal Vsync to the LCD screen to scan the screen images. The frequency of the scan signal is not a fixed value and is related to the input Vsync signal. When the frequency f _PWM of the PWM signal used to control the backlight of the LCD screen given by the counting control register does not match the frequency f _VSYNC of the scanning signal provided by the system board, there is a phase shift between the two, causing rolling water to appear on the LCD screen. Ripple phenomenon. Even if there is no phase correlation and frequency correlation between the PWM pulse and Vsync, since the signal on the liquid crystal glass of the LCD screen itself is reversed in polarity, the clamping pressure at both ends of the liquid crystal will change slightly, which will also cause the overall screen to scroll. Moiré occurs. The appearance of the rolling water ripple seriously affects the viewer's visual effect, and has a bad influence on the viewer's vision.

Contents of the invention

The main purpose of the present invention is to provide a backlight control signal adjustment method and device that can effectively avoid the interference of rolling water ripples.

The present invention proposes a method for adjusting a backlight control signal, comprising the steps of:

Obtain the frequency of the scanning signal and the screen parameters of the LCD screen;

Determine the frequency of the current PWM signal according to the frequency of the scanning signal;

According to the screen parameters of the liquid crystal display, determine the high-level part and the low-level part of the current PWM signal, and the trigger moment of the rising edge of the current PWM signal;

When the trigger moment of the rising edge of the current PWM signal arrives, trigger the rising edge of the PWM signal within one PWM signal period, and output the PWM signal according to the frequency, high level part and low level part of the current PWM signal.

Preferably, the step of determining the high-level part and low-level part of the current PWM signal and the trigger moment of the rising edge of the current PWM signal according to the screen parameters of the liquid crystal display specifically includes:

According to the screen parameters of the LCD screen, the number of scanning buses Vtotal is obtained;

According to the preset frequency multiplication coefficient PreScale and the number of scanning buses Vtotal, the number of scanning lines M=Vtotal÷PreScale of the scanning signal in one PWM signal cycle is obtained;

According to the preset duty ratio coefficient duty and the number M of scanning lines of the scanning signal in one PWM signal cycle, the number of high-level scanning lines N1=M×duty and the number of low-level scanning lines N2=M×( 1-duty), the number of high-level scanning lines N1 corresponds to the high-level part of the current PWM signal within one PWM signal period, and the number of low-level scanning lines N2 corresponds to the current PWM signal within one PWM signal period. low level part;

The moment when the scan signal arrives at the (i-1)×M+1th scan line is determined as the trigger moment for triggering the rising edge of the PWM signal in the i-th PWM signal cycle.

Preferably, the step of determining the frequency of the current PWM signal according to the frequency of the scanning signal specifically includes:

According to the preset frequency multiplication coefficient PreScale and the frequency f _VSYNC of the scanning signal, the frequency f _PWM =PreScale×f _VSYNC of the PWM signal is obtained.

Preferably, after the step of determining the high-level part and low-level part of the current PWM signal and the trigger moment of the rising edge of the current PWM signal according to the screen parameters of the liquid crystal display screen, the step further includes:

Within a preset time, detect whether the frequency of the scanning signal is within a preset frequency threshold range of the scanning signal, and whether the frequency of the current PWM signal is within the preset frequency threshold range of the PWM signal;

When the frequency of the scanning signal exceeds the preset scanning signal frequency threshold range, or when the frequency of the current PWM signal exceeds the preset PWM signal frequency threshold range, the trigger moment of the rising edge of the previous PWM signal is used as the current PWM signal The trigger time of the rising edge of the previous PWM signal is the frequency of the current PWM signal, the high level part of the previous PWM signal is the high level part of the current PWM signal, and the low level part of the previous PWM signal is Part of it is used as the low level part of the current PWM signal.

The present invention also proposes a backlight control signal adjustment device, including:

An acquisition module, configured to acquire the frequency of the scanning signal and the screen parameters of the liquid crystal display;

The generation module is used to determine the frequency of the current PWM signal according to the frequency of the scanning signal; and determine the high-level part and the low-level part of the current PWM signal and the current PWM signal according to the screen parameters of the liquid crystal display. The trigger moment of the rising edge;

The trigger module is used to trigger the rising edge of the PWM signal within one PWM signal cycle when the trigger moment of the rising edge of the current PWM signal arrives, and output the PWM signal.

Preferably, the generating module is specifically used for:

According to the screen parameters of the LCD screen, the number of scanning buses Vtotal is obtained;

According to the preset frequency multiplication coefficient PreScale and the number of scanning buses Vtotal, the number of scanning lines M=Vtotal÷PreScale of the scanning signal in one PWM signal cycle is obtained;

According to the preset duty ratio coefficient duty and the number M of scanning lines of the scanning signal in one PWM signal cycle, the number of high-level scanning lines N1=M×duty and the number of low-level scanning lines N2=M×( 1-duty), the number of high-level scanning lines N1 corresponds to the high-level part of the current PWM signal within one PWM signal period, and the number of low-level scanning lines N2 corresponds to the current PWM signal within one PWM signal period. low level part;

The moment when the scan signal arrives at the (i-1)×M+1th scan line is determined as the trigger moment for triggering the rising edge of the PWM signal in the i-th PWM signal cycle.

Preferably, the generating module is also specifically used for:

According to the preset frequency multiplication coefficient PreScale and the frequency f _VSYNC of the scanning signal, the frequency f _PWM =PreScale×f _VSYNC of the PWM signal is obtained.

Preferably, the backlight control signal adjustment device further includes a protection module for:

Within a preset time, detect whether the frequency of the scanning signal is within a preset frequency threshold range of the scanning signal, and whether the frequency of the current PWM signal is within the preset frequency threshold range of the PWM signal;

When the frequency of the scanning signal exceeds the preset scanning signal frequency threshold range, or when the frequency of the current PWM signal exceeds the preset PWM signal frequency threshold range, the trigger moment of the rising edge of the previous PWM signal is used as the current PWM signal The trigger time of the rising edge of the previous PWM signal is the frequency of the current PWM signal, the high level part of the previous PWM signal is the high level part of the current PWM signal, and the low level part of the previous PWM signal is Part of it is used as the low level part of the current PWM signal.

The present invention adjusts the output of the PWM signal according to the frequency of the scanning signal and the screen parameters of the liquid crystal display, avoiding the phase shift between the PWM signal and the frequency of the scanning signal caused by the mismatch between the two or the PWM signal on the liquid crystal glass of the liquid crystal display. Above all, the clamping pressure at both ends of the liquid crystal changes due to polarity reversal, which effectively avoids the phenomenon of rolling water ripples on the liquid crystal display.

Description of drawings

FIG. 1 is a flowchart of a first embodiment of a method for adjusting a backlight control signal of the present invention;

FIG. 2 is a flowchart of a second embodiment of the method for adjusting a backlight control signal of the present invention;

FIG. 3 is a flow chart of a third embodiment of the backlight control signal adjustment method of the present invention;

FIG. 4 is a flow chart of a fourth embodiment of the backlight control signal adjustment method of the present invention;

5 is a schematic structural diagram of the first embodiment of the backlight control signal adjustment device of the present invention;

FIG. 6 is a schematic structural diagram of a second embodiment of the backlight control signal adjusting device of the present invention.

The realization of the purpose of the present invention, functional characteristics and advantages will be further described in conjunction with the embodiments and with reference to the accompanying drawings.

Detailed ways

It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in FIG. 1 , FIG. 1 is a flowchart of a first embodiment of a method for adjusting a backlight control signal of the present invention. The method for adjusting the backlight control signal mentioned in this embodiment includes:

Step S10, obtaining the frequency of the scanning signal and the screen parameters of the liquid crystal display;

The method of this embodiment is implemented and executed by the system mainboard of the liquid crystal display. Wherein, the system main board is connected with the liquid crystal display, and the scanning signal is generated by the system main board, and the screen parameters can be directly stored in the memory of the system main board, or obtained from the system main board to the liquid crystal display.

Step S20, determine the frequency of the current PWM signal according to the frequency of the scanning signal;

In order to avoid the phase shift between the PWM signal and the scanning signal due to the frequency mismatch between the two, this embodiment determines the frequency of the current PWM signal according to the frequency of the scanning signal, which is beneficial to avoid rolling water on the LCD screen. ripple phenomenon.

Step S30, according to the screen parameters of the liquid crystal display, determine the high-level part and the low-level part of the current PWM signal, and the trigger moment of the rising edge of the current PWM signal;

In order to avoid the polarity reversal of the PWM signal on the liquid crystal glass of the liquid crystal display, resulting in changes in the clamping pressure at both ends of the liquid crystal, this embodiment determines the high-level part and low-level part of the current PWM signal according to the screen parameters of the liquid crystal display. The level part and the trigger time of the rising edge of the current PWM signal further avoid the occurrence of rolling water ripples.

Step S40, when the trigger moment of the rising edge of the current PWM signal arrives, trigger the rising edge of the PWM signal within one PWM signal period, and output the PWM signal according to the frequency, high level part and low level part of the current PWM signal .

The PWM signal in this embodiment is generated by the system mainboard of the liquid crystal display and output to the backlight constant current board of the liquid crystal display to control the brightness of the backlight. The present invention avoids the problem of TV flickering caused by the sudden change of the backlight duty ratio during the switching process of the TV system by the PWM signal generated by the counting control register. At the same time, this embodiment adjusts the output of the PWM signal according to the frequency of the scanning signal and the screen parameters of the liquid crystal display to avoid phase shift between the PWM signal and the frequency of the scanning signal caused by the frequency mismatch between the two or the PWM signal on the liquid crystal display. On the liquid crystal glass, due to the polarity reversal, the clamping pressure at both ends of the liquid crystal changes, which effectively avoids the phenomenon of rolling water ripples on the liquid crystal display.

As shown in FIG. 2 , FIG. 2 is a flow chart of a second embodiment of the backlight control signal adjustment method of the present invention. In this embodiment, on the basis of the embodiment shown in FIG. 1 , step S20 is described in detail, and step S20 specifically includes:

Step S21 , according to the preset frequency multiplication factor PreScale and the frequency f _VSYNC of the scanning signal, the frequency f _PWM =PreScale×f _VSYNC of the PWM signal is obtained.

The preset frequency multiplication coefficient PreScale in this embodiment is a natural number, for example, f _VSYNC =60 Hz, PreScale = 2, f _PWM =2×60=120 Hz. In this embodiment, the frequency of the current PWM signal is determined according to the frequency of the scanning signal, which can ensure a stable frequency relationship between the PWM signal and the scanning signal, and avoid the phase difference between the PWM signal and the scanning signal due to the frequency mismatch between the two. It is beneficial to avoid the phenomenon of scrolling water ripples on the LCD screen.

As shown in FIG. 3 , FIG. 3 is a flow chart of a third embodiment of the backlight control signal adjustment method of the present invention. In this embodiment, on the basis of the embodiment shown in FIG. 1 , step S30 is described in detail, and step S30 specifically includes:

Step S31, according to the screen parameters of the liquid crystal display, obtain the number of scanning buses Vtotal;

According to the screen parameters of the liquid crystal display, the system mainboard of the present embodiment can know the number of vertical buses Vtotal for image scanning, for example, Vtotal is 1125 lines.

Step S32, according to the preset frequency multiplication coefficient PreScale and the number of scanning buses Vtotal, the number of scanning lines M=Vtotal÷PreScale of the scanning signal in one PWM signal period is obtained;

According to the preset multiplication coefficient PreScale of the system motherboard, the cycle of scanning the M line will generate a PWM waveform is calculated. Wherein, the preset frequency multiplication coefficient PreScale is generally greater than or equal to 2, and the calculation result of M is a rounded integer. For example, PreScale=2, Vtotal=1125 lines, M=1125÷2=563 lines, that is, every 563 lines scan signal is a PWM period.

Step S33, according to the preset duty ratio coefficient duty and the number M of scanning lines of the scanning signal in one PWM signal period, the number of high-level scanning lines N1=M×duty and the number of low-level scanning lines N2=M× (1-duty), the number of high-level scanning lines N1 corresponds to the high-level part of the current PWM signal within a PWM signal period, and the number of low-level scanning lines N2 corresponds to the low-level of the current PWM signal within a PWM signal period part;

The calculation results of the number N1 of high-level scanning lines and the number N2 of low-level scanning lines are rounded integers. For example, duty=30%, N1=563×30%=169 lines, N2=563×(1-30%)=394 lines, that is, in the scanning time of 563 lines, 169 lines are at high level during the scanning time, The scanning time of the other 394 lines is low level. Determine the high-level part and low-level part of the current PWM signal according to the screen parameters of the liquid crystal display, which can avoid the pinch pressure change at both ends of the liquid crystal caused by the polarity reversal of the PWM signal on the liquid crystal glass of the liquid crystal display.

Step S34, determining the moment when the scan signal arrives at the (i-1)×M+1th scan line as the trigger moment for triggering the rising edge of the PWM signal in the i-th PWM signal period.

Align the rising edge of the PWM signal and the rising edge of the scanning signal within one PWM signal cycle to ensure a stable phase relationship between the PWM signal and the scanning signal, further avoiding the occurrence of rolling water ripples.

As shown in FIG. 4 , FIG. 4 is a flow chart of a fourth embodiment of the method for adjusting the backlight control signal of the present invention. On the basis of the embodiment shown in Figure 1, this embodiment adds the step of frequency protection, that is, after step S30, it also includes:

Step S51, within the preset time, detect whether the frequency f _VSYNC of the scanning signal is within the preset frequency threshold range of the scanning signal f _MIN-VSYNC ≤ f _VSYNC ≤ f _MAX-VSYNC , and whether the frequency f _PWM of the current PWM signal is within the preset frequency threshold Within the set PWM signal frequency threshold range f _MIN-PWM ≤ f _PWM ≤ f _MAX-PWM ; if yes, execute step S40; if no, execute step S52;

Step S52, when the frequency f _VSYNC of the scanning signal exceeds the preset scanning signal frequency threshold range f _VSYNC < f _MIN-VSYNC or f _VSYNC > f _MAX-VSYNC , or the frequency f _PWM of the current PWM signal exceeds the preset PWM signal When the frequency threshold range f _PWM < f _MIN-PWM or f _VSYNC > f _MAX-PWM , the trigger time of the rising edge of the previous PWM signal is taken as the trigger time of the rising edge of the current PWM signal, and the frequency of the previous PWM signal is taken as For the frequency of the current PWM signal, the high level part of the previous PWM signal is taken as the high level part of the current PWM signal, and the low level part of the previous PWM signal is taken as the low level part of the current PWM signal.

This embodiment takes into account the following situation. When the scanning signal is unstable, the frequency of the scanning signal will change instantaneously. At this time, if the frequency of the PWM signal is adjusted with the frequency of the unstable scanning signal, rolling water ripples will easily occur. Interference, in order to avoid the above situation, when the scanning signal is unstable, keep the PWM signal according to the frequency and phase of the PWM signal output normally last time, wait until the frequency of the scanning signal is stable, and then adjust the frequency and phase of the PWM signal according to the stable scanning signal The phase further avoids the occurrence of rolling water ripples.

As shown in FIG. 5 , FIG. 5 is a schematic structural view of the first embodiment of the backlight control signal adjusting device of the present invention. The backlight control signal adjustment device mentioned in this embodiment includes:

Obtaining module 10, for obtaining the frequency of scan signal and the screen parameter of liquid crystal display;

The generation module 20 is used to determine the frequency of the current PWM signal according to the frequency of the scanning signal; determine the high level part and the low level part of the current PWM signal and the rising edge of the current PWM signal according to the screen parameters of the liquid crystal display. trigger moment;

The trigger module 30 is configured to trigger the rising edge of the PWM signal within one PWM signal cycle when the trigger moment of the rising edge of the current PWM signal arrives, and according to the frequency, high level part and low level part of the current PWM signal, Output PWM signal.

This unit is located on the system board of the LCD monitor. Wherein, the system main board is connected with the liquid crystal display, and the scanning signal is generated by the system main board, and the screen parameters can be directly stored in the memory of the system main board, or obtained from the system main board to the liquid crystal display. In order to avoid the phase shift between the PWM signal and the scanning signal due to the frequency mismatch between the two, this embodiment determines the frequency of the current PWM signal according to the frequency of the scanning signal, which is beneficial to avoid rolling water on the LCD screen. ripple phenomenon. In order to avoid the polarity reversal of the PWM signal on the liquid crystal glass of the liquid crystal display, resulting in changes in the clamping pressure at both ends of the liquid crystal, this embodiment determines the high-level part and low-level part of the current PWM signal according to the screen parameters of the liquid crystal display. The level part and the trigger time of the rising edge of the current PWM signal further avoid the occurrence of rolling water ripples. The PWM signal in this embodiment is generated by the system mainboard of the liquid crystal display and output to the backlight constant current board of the liquid crystal display to control the brightness of the backlight. The present invention avoids the problem of TV flickering caused by the sudden change of the backlight duty ratio during the switching process of the TV system by the PWM signal generated by the counting control register. At the same time, this embodiment adjusts the output of the PWM signal according to the frequency of the scanning signal and the screen parameters of the liquid crystal display to avoid phase shift between the PWM signal and the frequency of the scanning signal caused by the frequency mismatch between the two or the PWM signal on the liquid crystal display. On the liquid crystal glass, due to the polarity reversal, the clamping pressure at both ends of the liquid crystal changes, which effectively avoids the phenomenon of rolling water ripples on the liquid crystal display.

The generation module 20 of the embodiment of the present invention is specifically used for:

According to the preset frequency multiplication coefficient PreScale and the frequency f _VSYNC of the scanning signal, the frequency f _PWM =PreScale×f _VSYNC of the PWM signal is obtained.

The preset frequency multiplication coefficient PreScale in this embodiment is a natural number, for example, f _VSYNC =60 Hz, PreScale = 2, f _PWM =2×60=120 Hz. In this embodiment, the frequency of the current PWM signal is determined according to the frequency of the scanning signal, which can ensure a stable frequency relationship between the PWM signal and the scanning signal, and avoid the phase difference between the PWM signal and the scanning signal due to the frequency mismatch between the two. It is beneficial to avoid the phenomenon of scrolling water ripples on the LCD screen.

The generation module 20 of the embodiment of the present invention is also specifically used for:

According to the screen parameters of the LCD screen, the number of scanning buses Vtotal is obtained;

According to the preset frequency multiplication coefficient PreScale and the number of scanning buses Vtotal, the number of scanning lines M=Vtotal÷PreScale of the scanning signal in one PWM signal period is obtained;

According to the preset duty cycle coefficient duty and the scanning line number M of the scanning signal in one PWM signal cycle, the number of high-level scanning lines N1=M×duty and the number of low-level scanning lines N2=M×(1- duty), the number of high-level scanning lines N1 corresponds to the high-level part of the current PWM signal in a PWM signal cycle, and the number of low-level scanning lines N2 corresponds to the low-level part of the current PWM signal in a PWM signal cycle;

The moment when the scan signal arrives at the (i-1)×M+1th scan line is determined as the trigger moment for triggering the rising edge of the PWM signal in the i-th PWM signal cycle.

According to the screen parameters of the liquid crystal display, the system mainboard of the present embodiment can know the number of vertical buses Vtotal for image scanning, for example, Vtotal is 1125 lines. According to the preset multiplication coefficient PreScale of the system motherboard, the cycle of scanning the M line will generate a PWM waveform is calculated. Wherein, the preset frequency multiplication coefficient PreScale is generally greater than or equal to 2, and the calculation result of M is a rounded integer. For example, PreScale=2, Vtotal=1125 lines, M=1125÷2=563 lines, that is, every 563 lines scan signal is a PWM period. The calculation results of the number N1 of high-level scanning lines and the number N2 of low-level scanning lines are rounded integers. For example, duty=30%, N1=563×30%=169 lines, N2=563×(1-30%)=394 lines, that is, in the scanning time of 563 lines, 169 lines are at high level during the scanning time, The scanning time of the other 394 lines is low level. Determine the high-level part and low-level part of the current PWM signal according to the screen parameters of the liquid crystal display, which can avoid the pinch pressure change at both ends of the liquid crystal caused by the polarity reversal of the PWM signal on the liquid crystal glass of the liquid crystal display. Align the rising edge of the PWM signal and the rising edge of the scanning signal within one PWM signal cycle to ensure a stable phase relationship between the PWM signal and the scanning signal, further avoiding the occurrence of rolling water ripples.

As shown in FIG. 6 , FIG. 6 is a schematic structural diagram of a second embodiment of the backlight control signal adjusting device of the present invention. In this embodiment, on the basis of the embodiment shown in Figure 5, a protection module 40 is added for:

Within the preset time, detect whether the frequency of the scanning signal is within the preset frequency threshold range of the scanning signal, and whether the frequency of the current PWM signal is within the preset frequency threshold range of the PWM signal;

When the frequency of the scanning signal exceeds the preset frequency threshold range of the scanning signal, or when the frequency of the current PWM signal exceeds the preset frequency threshold range of the PWM signal, the trigger moment of the rising edge of the previous PWM signal is taken as the rising of the current PWM signal At the triggering moment of the edge, the frequency of the previous PWM signal is taken as the frequency of the current PWM signal, the high level part of the previous PWM signal is taken as the high level part of the current PWM signal, and the low level part of the previous PWM signal is taken as the frequency of the current PWM signal. The low level part of the current PWM signal.

This embodiment takes into account the following situation. When the scanning signal is unstable, the frequency of the scanning signal will change instantaneously. At this time, if the frequency of the PWM signal is adjusted with the frequency of the unstable scanning signal, rolling water ripples will easily occur. Interference, in order to avoid the above situation, when the scanning signal is unstable, keep the PWM signal according to the frequency and phase of the PWM signal output normally last time, wait until the frequency of the scanning signal is stable, and then adjust the frequency and phase of the PWM signal according to the stable scanning signal The phase further avoids the occurrence of rolling water ripples.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description of the present invention and the contents of the accompanying drawings, or directly or indirectly used in other related All technical fields are equally included in the scope of patent protection of the present invention.

Claims (8)

1. A method for adjusting a backlight control signal, comprising the steps of: Obtain the frequency of the scanning signal and the screen parameters of the LCD screen; Determine the frequency of the current PWM signal according to the frequency of the scanning signal; According to the screen parameters of the liquid crystal display, obtain the scanning bus number Vtotal; according to the preset frequency multiplication coefficient PreScale and the scanning bus number Vtotal, obtain the scanning line number M=Vtotal÷PreScale of the scanning signal in a PWM signal period ; Determine the high-level part and low-level part of the current PWM signal and the triggering of the rising edge of the current PWM signal according to the preset duty cycle coefficient duty and the scanning line number M of the scanning signal in one PWM signal cycle time; If within the preset time, it is detected that the frequency of the scanning signal is within the preset scanning signal frequency threshold range, and the frequency of the current PWM signal is within the preset PWM signal frequency threshold range; then at the rising edge of the current PWM signal When the trigger moment arrives, trigger the rising edge of the PWM signal within one PWM signal period, and output the PWM signal according to the frequency, high level part and low level part of the current PWM signal. 2. The backlight control signal adjustment method according to claim 1, characterized in that, according to the screen parameters of the liquid crystal display, determine the high-level part and the low-level part of the current PWM signal and the rise of the current PWM signal The steps at the triggering moment of the edge include: According to the preset duty ratio coefficient duty and the scanning line number M of the scanning signal in one PWM signal period, the number of high-level scanning lines N1=M×duty and the number of low-level scanning lines N2=M×( 1-duty), the number of high-level scanning lines N1 corresponds to the high-level part of the current PWM signal within one PWM signal period, and the number of low-level scanning lines N2 corresponds to the current PWM signal within one PWM signal period. low level part; The moment when the scan signal arrives at the (i-1)×M+1th scan line is determined as the trigger moment for triggering the rising edge of the PWM signal in the i-th PWM signal cycle. 3. The method for adjusting the backlight control signal according to claim 2, wherein the step of determining the frequency of the current PWM signal according to the frequency of the scanning signal specifically comprises: According to the preset frequency multiplication coefficient PreScale and the frequency f _VSYNC of the scanning signal, the frequency f _PWM =PreScale×f _VSYNC of the PWM signal is obtained. 4. The backlight control signal adjustment method according to claim 2 or 3, characterized in that, according to the screen parameters of the liquid crystal display, determine the high level part and the low level part of the current PWM signal, and the current PWM signal After the step of the trigger moment of the rising edge also include: Within a preset time, detect whether the frequency of the scanning signal is within a preset frequency threshold range of the scanning signal, and whether the frequency of the current PWM signal is within the preset frequency threshold range of the PWM signal; When the frequency of the scanning signal exceeds the preset scanning signal frequency threshold range, or when the frequency of the current PWM signal exceeds the preset PWM signal frequency threshold range, the trigger moment of the rising edge of the previous PWM signal is used as the current PWM signal The trigger time of the rising edge of the previous PWM signal is the frequency of the current PWM signal, the high level part of the previous PWM signal is the high level part of the current PWM signal, and the low level part of the previous PWM signal is Part of it is used as the low level part of the current PWM signal. 5. A backlight control signal adjustment device, characterized in that, comprising: An acquisition module, configured to acquire the frequency of the scan signal and the screen parameters of the liquid crystal display; The generation module is used to determine the frequency of the current PWM signal according to the frequency of the scanning signal; according to the screen parameters of the liquid crystal display, obtain the number of scanning buses Vtotal; according to the preset frequency multiplication coefficient PreScale and the number of scanning buses Vtotal, Obtain the number of scan lines M=Vtotal÷PreScale of the scan signal within one PWM signal period; determine the current PWM signal according to the preset duty ratio coefficient duty and the scan line M of the scan signal within one PWM signal period The high-level part and low-level part of , and the trigger moment of the rising edge of the current PWM signal; The trigger module is used to trigger the rising edge of the PWM signal within one PWM signal cycle when the trigger moment of the rising edge of the current PWM signal arrives, and output the PWM signal. 6. The backlight control signal adjustment device according to claim 5, wherein the generating module is specifically used for: According to the preset duty ratio coefficient duty and the scanning line number M of the scanning signal in one PWM signal period, the number of high-level scanning lines N1=M×duty and the number of low-level scanning lines N2=M×( 1-duty), the number of high-level scanning lines N1 corresponds to the high-level part of the current PWM signal within one PWM signal period, and the number of low-level scanning lines N2 corresponds to the current PWM signal within one PWM signal period. low level part; The moment when the scan signal arrives at the (i-1)×M+1th scan line is determined as the trigger moment for triggering the rising edge of the PWM signal in the i-th PWM signal period. 7. The backlight control signal adjustment device according to claim 6, wherein the generating module is further specifically used for: According to the preset frequency multiplication coefficient PreScale and the frequency f _VSYNC of the scanning signal, the frequency f _PWM =PreScale×f _VSYNC of the PWM signal is obtained. 8. The device for adjusting backlight control signals according to claim 6 or 7, further comprising a protection module for: Within a preset time, detect whether the frequency of the scanning signal is within a preset frequency threshold range of the scanning signal, and whether the frequency of the current PWM signal is within the preset frequency threshold range of the PWM signal; When the frequency of the scanning signal exceeds the preset scanning signal frequency threshold range, or when the frequency of the current PWM signal exceeds the preset PWM signal frequency threshold range, the trigger moment of the rising edge of the previous PWM signal is used as the current PWM signal The trigger time of the rising edge of the previous PWM signal is the frequency of the current PWM signal, the high level part of the previous PWM signal is the high level part of the current PWM signal, and the low level part of the previous PWM signal is Part of it is used as the low level part of the current PWM signal.