Display screen ultra-low brightness adjustment transition method based on PWM and PFM

Abstract

The invention provides a display screen ultra-low brightness adjustment transition method based on PWM and PFM, and relates to the technical field of display, and the method comprises the steps: receiving a brightness adjustment instruction sent by a user through an FPGA, recognizing a brightness adjustment range value in the brightness adjustment instruction, matching the brightness adjustment range value with a set brightness range value, and adjusting the brightness adjustment range value according to the brightness adjustment range value; determining a dimming mode corresponding to the brightness adjustment range value; the dimming mode is a PFM (Pulse Frequency Modulation) dimming mode or a PWM (Pulse Width Modulation) dimming mode; and performing brightness data processing on the brightness adjustment range value according to a dimming operation method set in the dimming mode so as to convert brightness data into a corresponding LED driving signal, and adjusting the brightness of the display screen through the LED driving signal. According to the invention, advantages of PWM and PFM can be combined, limitations of the PWM and the PFM are overcome, and brightness adjustment of high brightness precision and wide brightness range of the LED light source is realized.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and in particular to an ultra-low brightness adjustment transition method for a display screen based on PWM and PFM. Background Art

[0002] In modern lighting and display technology, LED light sources have been widely used due to their low power consumption, long life, and rich colors. In many application scenarios such as display devices and lighting systems, LED brightness adjustment control has gradually become a vital functional requirement. Product design has put forward higher and higher requirements on the accuracy and range of brightness control of LED light sources. On the one hand, in the field of professional image display, high-precision brightness adjustment is required, and subtle brightness changes will have a significant impact on the display quality and color of the image. On the other hand, different usage environments also have different requirements for the brightness adjustment range. In a strong light environment, it is necessary to adjust to a higher brightness to ensure a clear display effect, while in a weak light environment, ultra-low brightness control is particularly important. A wide brightness range enables the product to adapt to different usage environments and improve the versatility and practicality of the product. At present, the commonly used LED dimming schemes are pulse width modulation (PWM) and pulse frequency modulation (PFM).

[0003] PWM dimming controls the duty cycle of the brightness output signal by changing the width of the pulse to achieve the purpose of changing the brightness of the display screen. PWM dimming can avoid problems such as inaccurate color rendering and uneven brightness caused by algorithm matching. However, it was found in the product design process that only using pulse width modulation has certain requirements for chip performance. Because the product faces a more severe environment, the minimum brightness in the brightness adjustment range given by some dimming chips cannot meet the actual application needs. Traditional PWM dimming methods often have problems such as insufficient accuracy and poor stability in ultra-low brightness scenarios. For example: According to the data in the manual of the LED control chip used in the actual product, the minimum lighting time ton (min) that supports direct PWM brightness adjustment is 200ns, but the product design requires a minimum duty cycle of 0.0135%. The high-level turn-on time obtained when the frequency is 2000Hz should reach 67.5ns, which is far lower than the minimum value of PWM brightness adjustment. At this time, if PWM dimming is forced to display ultra-low brightness, it will cause the display screen to flicker. In an ultra-low brightness environment, staring at an abnormal display screen for a long time can cause eye fatigue, dry eyes, headaches and other problems, and may also cause unexpected situations such as data recognition errors.

[0004] PFM dimming adjusts the brightness output by changing the pulse frequency, which can avoid the problem of narrow pulse width of PWM dimming at low brightness to a certain extent. However, the frequency variation range of PFM dimming is large, which may cause electromagnetic interference to surrounding electronic equipment. This will become a potential problem in scenarios with high requirements for electromagnetic compatibility. On the other hand, the control of PFM dimming is relatively complex. The pulse frequency corresponding to high brightness is too high. Even a small frequency change may cause a large fluctuation in brightness, making it difficult to accurately control the frequency change to achieve stable brightness adjustment. At high brightness, high-frequency signal processing requires higher clock speeds and more complex logic design, which places extremely high demands on the resources and performance of FPGAs, brings tremendous pressure to the design of FPGAs, and also increases the cost and complexity of the system.

[0005] Therefore, currently, neither PWM dimming nor PFM dimming can simultaneously meet the requirements of LED light sources for high brightness accuracy and wide brightness range. Therefore, a new brightness adjustment method is needed that can combine the advantages of PWM and PFM and overcome the limitations of both to achieve high brightness accuracy and wide brightness range brightness adjustment for LED light sources. Summary of the invention

[0006] In order to simultaneously meet the requirements of LED light sources for high brightness accuracy and wide brightness range, the embodiment of the present application provides a method for ultra-low brightness adjustment transition of a display screen based on PWM and PFM to achieve the adjustment transition between ultra-low brightness and normal brightness of the display screen. This hybrid dimming mechanism combines the advantages of both PWM and PFM modulation methods. In high-brightness areas, PWM dimming is mainly used to ensure high dimming accuracy and fast response. In ultra-low brightness areas, PFM dimming adjusts the brightness output by changing the pulse frequency, improves the stability and reliability of dimming, and solves the flicker problem of LED light sources at ultra-low brightness.

[0007] The embodiment of the present application provides the following technical solution: a display screen ultra-low brightness adjustment transition method based on PWM and PFM, comprising:

[0008] Receiving a brightness adjustment instruction sent by a user through the FPGA, identifying a brightness adjustment range value in the brightness adjustment instruction, matching the brightness adjustment range value with a set brightness range value, and determining a dimming mode corresponding to the brightness adjustment range value; the dimming mode is a PFM dimming mode or a PWM dimming mode;

[0009] The brightness adjustment range value is subjected to brightness data processing according to the dimming operation method set in the dimming mode to convert the brightness data into a corresponding LED driving signal, and the brightness of the display screen is adjusted by the LED driving signal.

[0010] According to an embodiment of the present application, the LED driving signal includes a duty cycle and a signal frequency, so that the brightness of the display screen is adjusted to a specified brightness value in the brightness adjustment range value through the duty cycle and the signal frequency.

[0011] According to an embodiment of the present application, if the brightness adjustment range value is an ultra-low brightness range, the corresponding dimming mode is determined to be a PFM dimming mode, and the dimming operation method set in the PFM dimming mode is to maintain a high level on time t H The input brightness data is converted into the corresponding LED driving signal by fixing or adjusting the frequency f.

[0012] According to an embodiment of the present application, if the brightness adjustment range value is a normal brightness range, the corresponding dimming mode is determined to be a PWM dimming mode, and the dimming operation method set in the PWM dimming mode is to keep the frequency f fixed and adjust the high level opening time t H The input brightness data is converted into the corresponding LED driving signal.

[0013] According to an embodiment of the present application, the set brightness range value is 0-685.2cd / m 2 , where 0 represents the minimum brightness of the display, 685.2cd / m 2 Indicates the maximum brightness of the display.

[0014] According to an embodiment of the present application, the ultra-low brightness range is 0-2.29 cd / m 2 The normal brightness range is 10.69-685.2cd / m 2 .

[0015] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0016] The ultra-low brightness adjustment transition method of the display screen described in the embodiment of the present invention has the advantage of adding a PFM brightness adjustment mode under ultra-low brightness compared with the existing PWM brightness adjustment scheme under the condition of wide brightness adjustment range and low precision. By combining the two dimming schemes of PWM and PFM, the stroboscopic problem encountered in ultra-low brightness under the single PWM dimming mode is avoided, and the stability of the output brightness is ensured.

[0017] The ultra-low brightness adjustment transition method for a display screen described in an embodiment of the present invention has the advantage that, compared with simple PFM dimming, it avoids the problem of uneven brightness change caused by coarse dimming accuracy at high brightness in a single PFM dimming mode, and at the same time reduces electromagnetic interference to a certain extent, thereby improving the electromagnetic compatibility of the system.

[0018] The ultra-low brightness adjustment transition method of the display screen described in the embodiment of the present invention has the advantage that the dimming solution based on FPGA is highly flexible and programmable. Because the high-level on time is fixed in the PFM dimming mode, the frequency f can be flexibly adjusted according to different application scenarios and project requirements to achieve the ultra-low brightness range.

[0019] The ultra-low brightness adjustment transition method for a display screen described in the embodiment of the present invention has the advantage that the two dimming modes do not jump during the switching process, and the LED output drive signal is more stable. Whether in the high brightness area or the ultra-low brightness area, the flicker phenomenon can be greatly reduced, providing a more comfortable viewing experience and reducing visual fatigue.

[0020] The ultra-low brightness adjustment transition method for a display screen described in an embodiment of the present invention has the advantage that the PWM and PFM hybrid dimming mode enables the FPGA to achieve a larger and more extreme dimming range under the chip performance index requirements, which can save more energy costs and reduce the iterative development time between different chip applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the internal design of FPGA in the ultra-low brightness adjustment transition method of the display screen based on PWM and PFM in an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of LED driving signals in a display screen ultra-low brightness adjustment transition method based on PWM and PFM according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0025] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0026] like Figure 1 As shown, an embodiment of the present invention provides a display screen ultra-low brightness adjustment transition method based on PWM and PFM, comprising:

[0027] Receiving a brightness adjustment instruction sent by a user through the FPGA, identifying a brightness adjustment range value in the brightness adjustment instruction, matching the brightness adjustment range value with a set brightness range value, and determining a dimming mode corresponding to the brightness adjustment range value; the dimming mode is a PFM dimming mode or a PWM dimming mode;

[0028] The brightness adjustment range value is subjected to brightness data processing according to the dimming operation method set in the dimming mode to convert the brightness data into a corresponding LED driving signal, and the brightness of the display screen is adjusted by the LED driving signal.

[0029] The ultra-low brightness adjustment transition method of the display screen based on PWM and PFM in the embodiment of the present invention is a dimming mechanism combining pulse width modulation mode (PWM) and pulse frequency modulation mode (PFM) based on FPGA for ultra-low brightness. In this method, after receiving the brightness adjustment instruction sent by the user, the FPGA identifies the brightness adjustment range in the brightness adjustment instruction and switches to the corresponding dimming mode, and adjusts the brightness of the display screen through dimming operation processing to match the brightness required by the dimming instruction, ensuring that the brightness of the display screen can achieve a smooth change within the full brightness range, and improving the display effect of the display screen under ultra-low brightness.

[0030] In this embodiment, the LED driving signal includes a duty cycle and a signal frequency, so that the brightness of the display screen is adjusted to a specified brightness value within the brightness adjustment range through the duty cycle and the signal frequency.

[0031] In specific implementation, if the brightness adjustment range value is an ultra-low brightness range, the corresponding dimming mode is determined to be a PFM dimming mode, and the dimming operation method set in the PFM dimming mode is to maintain a high level on time t H The input brightness data is converted into the corresponding LED driving signal by fixing and adjusting the frequency f. If the brightness adjustment range value is within the normal brightness range, the corresponding dimming mode is determined to be the PWM dimming mode. The dimming operation method set in the PWM dimming mode is to keep the frequency f fixed and adjust the high level opening time t H The input brightness data is converted into the corresponding LED driving signal.

[0032] In specific implementation, the set brightness range is 0-685.2cd / m 2 , where 0 represents the minimum brightness of the display, 685.2cd / m 2 Indicates the maximum brightness of the display. The ultra-low brightness range is 0-2.29cd / m 2 The normal brightness range is 10.69-685.2cd / m 2 .

[0033] In order to further explain the purpose, technical solutions and advantages of the embodiments of the present invention, the specific implementation of the present invention will be described in detail below. The following description will be combined with the accompanying drawings and examples. The method specifically includes:

[0034] (1) Define the range of brightness values ​​that FPGA can accept as 0-685.2cd / m 2 , 0 means the lowest brightness of the display, 685.2cd / m 2 Indicates the maximum brightness of the display. The user sends a brightness command to the FPGA, and the FPGA performs corresponding processing after receiving the command to achieve autonomous adjustment of the display brightness.

[0035] (2) Set a segmented dimming curve function. The FPGA first performs logical judgment based on the input brightness command and enters the dimming mode under the corresponding conditions. The FPGA adjusts the brightness of the display screen by controlling the LED drive signal. Figure 2 As shown, Figure 2 The following is a schematic diagram of the LED drive signal waveform. The LED drive signal is mainly composed of two elements: duty cycle and signal frequency. The specific definitions are as follows:

[0036]

[0037]

[0038] Among them, t H is the high level turn-on time, tL It is the low level duration.

[0039] FPGA sets the duty cycle and frequency of the LED drive signal according to the input brightness command, so that the display brightness switches to the specified brightness value. The implementation process flow is as follows: Figure 1 shown.

[0040] (3) If the brightness is detected to be in the ultra-low brightness range, the FPGA performs PFM dimming operation and maintains a high level on time t H The input brightness quality data is converted into the corresponding LED drive signal by fixing and adjusting the frequency f; if it is recognized that the brightness is within the normal brightness range, the FPGA performs PWM dimming operation and adjusts the high-level opening time t according to the pre-set calculation formula by keeping the frequency f fixed. H The input brightness quality data is converted into the corresponding LED driving signal. The corresponding relationship is shown in Table 1 below:

[0041] Table 1 Correspondence between LED drive signal and brightness command value

[0042]

[0043] (4) In the case of low brightness, choose to use the PFM brightness adjustment solution: When the brightness command is 0, the LED drive signal is always low and the LED is not lit. When the brightness value is 0.34cd / m 2 When the LED drive signal frequency is 90Hz, the corresponding output duty cycle is 0.0135%. When the brightness value is 1.15cd / m 2 The frequency of the LED drive signal is 250Hz, corresponding to an output duty cycle of 0.0375%. When the brightness value is 2.29cd / m 2 When the LED drive signal frequency is 500Hz, the corresponding output duty cycle is 0.075%. In the normal brightness adjustment range, the brightness value is 10.69-685.2cd / m 2 When the display screen is set to 0.34-2.29cd / m, the PWM brightness adjustment scheme is still used to adjust the display screen brightness. 2 , Normal brightness 10.69-685.2cd / m 2 The display is normal at all times, and the human eye does not feel uncomfortable. There is no obvious jump or flicker when adjusting the display brightness.

[0044] (5) FPGA outputs the corresponding LED driving signal to the LED control chip to complete the driving process.

[0045] The embodiment of the present invention designs an ultra-low brightness adjustment method for a display screen so that the product meets the requirements for normal display under high brightness range and high precision requirements, and proves the compliance of the product design through corresponding type tests, thereby achieving brightness adjustment of the LED light source with high brightness precision and a wide brightness range.

[0046] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A display screen ultra-low brightness adjustment transition method based on PWM and PFM, characterized in that: include: Receiving a brightness adjustment instruction sent by a user through the FPGA, identifying a brightness adjustment range value in the brightness adjustment instruction, matching the brightness adjustment range value with a set brightness range value, and determining a dimming mode corresponding to the brightness adjustment range value; the dimming mode is a PFM dimming mode or a PWM dimming mode; The brightness adjustment range value is subjected to brightness data processing according to the dimming operation method set in the dimming mode to convert the brightness data into a corresponding LED driving signal, and the brightness of the display screen is adjusted by the LED driving signal.

2. The display screen ultra-low brightness adjustment transition method based on PWM and PFM according to claim 1 is characterized in that: The LED driving signal includes a duty cycle and a signal frequency, so that the brightness of the display screen is adjusted to a specified brightness value in the brightness adjustment range through the duty cycle and the signal frequency.

3. The display screen ultra-low brightness adjustment transition method based on PWM and PFM according to claim 1 is characterized in that: If the brightness adjustment range value is an ultra-low brightness range, the corresponding dimming mode is determined to be a PFM dimming mode. The dimming operation method set in the PFM dimming mode is to maintain a high level on time t H The input brightness data is converted into the corresponding LED driving signal by fixing or adjusting the frequency f.

4. The display screen ultra-low brightness adjustment transition method based on PWM and PFM according to claim 3 is characterized in that: If the brightness adjustment range value is within the normal brightness range, the corresponding dimming mode is determined to be the PWM dimming mode. The dimming operation method set in the PWM dimming mode is to keep the frequency f fixed and adjust the high level opening time t H The input brightness data is converted into the corresponding LED driving signal.

5. The display screen ultra-low brightness adjustment transition method based on PWM and PFM according to claim 4 is characterized in that: The set brightness range is 0-685.2cd / m 2 , where 0 represents the minimum brightness of the display, 685.2cd / m 2 Indicates the maximum brightness of the display.

6. The display screen ultra-low brightness adjustment transition method based on PWM and PFM according to claim 5, characterized in that: The ultra-low brightness range is 0-2.29cd / m 2 The normal brightness range is 10.69-685.2cd / m 2 .

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