Method for ultralow brightness adjustment transition of display screen based on PWM and pfm

Abstract

The present invention relates to the technical field of display. Provided is a method for ultralow brightness adjustment transition of a display screen based on PWM and PFM. The method comprises: by means of an FPGA, receiving a brightness adjustment instruction sent by a user, 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, wherein the dimming mode is either a PFM dimming mode or a PWM dimming mode; and on the basis of a dimming operation method set in the dimming mode, performing brightness data processing on the brightness adjustment range value, so as to convert brightness data into a corresponding LED driving signal, and adjusting the brightness of a display screen by means of the LED driving signal. The present invention can combine the advantages of PWM and PFM while overcoming the limitations of PWM and PFM, thereby achieving high-precision and wide-range brightness adjustment for LED light sources.

Description

A Transitional Method for Ultra-Low Brightness Adjustment of Display Screens Based on PWM and PFM Technical Field

[0001] This invention relates to the field of display technology, and specifically to a method for adjusting ultra-low brightness of a display screen based on PWM and PFM. Background Technology

[0002] In modern lighting and display technologies, LED light sources are widely used due to their low power consumption, long lifespan, and rich colors. In many display devices and lighting systems, LED brightness adjustment and control has gradually become a crucial functional requirement. Product design places increasingly higher demands on the precision and range of LED light source brightness control. On the one hand, in professional image display fields, high-precision brightness adjustment is required, as even subtle brightness changes can significantly impact image display quality and color. On the other hand, different usage environments have different requirements for the brightness adjustment range. In strong light environments, higher brightness is needed to ensure clear display, while in low light environments, ultra-low brightness control is particularly important. A wide brightness range allows products to adapt to different usage environments, improving their versatility and practicality. Currently, commonly used LED dimming solutions include Pulse Width Modulation (PWM) and Pulse Frequency Modulation (PFM).

[0003] PWM dimming controls the duty cycle of the brightness output signal by changing the pulse width, thereby altering the brightness of the display screen. PWM dimming avoids problems such as inaccurate color rendering and uneven brightness caused by algorithm matching. However, during product design, it was found that using pulse width modulation alone places certain demands on chip performance. Due to the increasingly severe environments faced by products, the minimum brightness within the brightness adjustment range provided by some dimming chips cannot meet the needs of practical applications. Traditional PWM dimming methods often suffer from insufficient accuracy and poor stability in ultra-low brightness scenarios. For example, according to the datasheet of the LED control chip used in actual products, the minimum on-time (ton) for direct PWM brightness adjustment is 200ns, but the product design requires a minimum duty cycle of 0.0135%. At a frequency of 2000Hz, the high-level on-time should reach 67.5ns, far below the minimum value for PWM brightness adjustment. If PWM dimming is forced to display ultra-low brightness in this situation, it will cause screen flickering. In ultra-low brightness environments, prolonged viewing of abnormally displayed screens can cause eye fatigue, dry eyes, headaches, and may also lead to unexpected situations such as data recognition errors.

[0004] PFM dimming adjusts brightness output by changing the pulse frequency, which to some extent avoids the problems caused by the narrow pulse width of PWM dimming at low brightness. However, the wide frequency variation range of PFM dimming may cause electromagnetic interference to surrounding electronic devices, posing a potential problem in scenarios with high electromagnetic compatibility requirements. On the other hand, PFM dimming control is relatively complex. High brightness corresponds to excessively high pulse frequencies, and even small frequency changes can lead to significant brightness fluctuations, making it difficult to precisely control frequency changes to achieve stable brightness adjustment. High-brightness, high-frequency signal processing requires higher clock speeds and more complex logic designs, placing extremely high demands on FPGA resources and performance, putting immense pressure on FPGA design, and increasing system cost and complexity.

[0005] Therefore, neither PWM dimming nor PFM dimming alone can simultaneously meet the requirements of LED light sources for high brightness accuracy and a wide brightness range. Thus, a new brightness adjustment method is needed that combines the advantages of PWM and PFM while overcoming their limitations, achieving high brightness accuracy and a wide brightness range for LED light sources. Summary of the Invention

[0006] To simultaneously meet the requirements of LED light sources for high brightness accuracy and a wide brightness range, this application provides a method for adjusting and transitioning ultra-low brightness of a display screen based on PWM and PFM, enabling a smooth transition between ultra-low brightness and normal brightness. This hybrid dimming mechanism combines the advantages of both PWM and PFM modulation methods. In the high-brightness region, PWM dimming is primarily used to ensure high dimming accuracy and fast response. In the ultra-low brightness region, PFM dimming adjusts the brightness output by changing the pulse frequency, improving the stability and reliability of dimming and addressing the flicker problem of LED light sources at ultra-low brightness.

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

[0008] The FPGA receives brightness adjustment commands sent by the user, identifies the brightness adjustment range value in the brightness adjustment command, matches the brightness adjustment range value with the set brightness range value, and determines the dimming mode corresponding to the brightness adjustment range value; the dimming mode is either PFM dimming mode or PWM dimming mode.

[0009] The brightness adjustment range value is processed according to the dimming calculation 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 one embodiment of this application, the LED driving signal includes a duty cycle and a signal frequency, so as to adjust the brightness of the display screen to a specified brightness value within the brightness adjustment range value through the duty cycle and the signal frequency.

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

[0012] According to one embodiment of this application, if the brightness adjustment range value is within the normal brightness range, then the corresponding dimming mode is determined to be a PWM dimming mode. The dimming calculation method set in the PWM dimming mode is to keep the frequency f fixed and adjust the high-level on-time t. H The input brightness data is converted into the corresponding LED driving signal in this way.

[0013] According to one embodiment of this application, the set brightness range value is 0-685.2 cd / m². 2 Where 0 represents the minimum brightness of the display screen, 685.2 cd / m². 2 This indicates the maximum brightness of the display screen.

[0014] According to one embodiment of this application, the ultra-low brightness range is 0-2.29 cd / m². 2 The normal brightness range is 10.69-685.2 cd / m². 2 .

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

[0016] The ultra-low brightness adjustment transition method for displays described in this invention has the advantage of adding a PFM brightness adjustment mode for ultra-low brightness, compared to existing PWM brightness adjustment schemes, while maintaining a wide brightness adjustment range and low precision. By combining PWM and PFM dimming schemes, the flicker problem encountered in ultra-low brightness under single PWM dimming mode is avoided, ensuring the stability of output brightness.

[0017] The ultra-low brightness adjustment transition method for the display screen described in this embodiment of the invention has the advantage of avoiding the problem of uneven brightness change caused by excessively coarse dimming precision when the brightness is high in the single PFM dimming mode, compared with simple PFM dimming. At the same time, it reduces electromagnetic interference to a certain extent and improves the electromagnetic compatibility of the system.

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

[0019] The ultra-low brightness adjustment transition method for displays described in this invention has the advantage of not abruptly switching between the two dimming modes, resulting in a more stable LED output drive signal. Whether in high-brightness or ultra-low-brightness areas, it significantly reduces flicker, providing a more comfortable viewing experience and reducing eye strain.

[0020] The ultra-low brightness adjustment transition method for displays described in this invention has the advantage that the hybrid dimming mode of PWM and PFM enables the FPGA to achieve a larger and more extreme dimming range under the chip performance requirements, which can save more energy costs and reduce the iterative development time between different chip applications. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

[0024] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0025] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] As shown in Figure 1, this embodiment of the invention provides a method for adjusting ultra-low brightness of a display screen based on PWM and PFM, including:

[0027] The FPGA receives brightness adjustment commands sent by the user, identifies the brightness adjustment range value in the brightness adjustment command, matches the brightness adjustment range value with the set brightness range value, and determines the dimming mode corresponding to the brightness adjustment range value; the dimming mode is either PFM dimming mode or PWM dimming mode.

[0028] The brightness adjustment range value is processed according to the dimming calculation 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 for displays based on PWM and PFM, as described in this invention, is a dimming mechanism combining FPGA-based pulse width modulation (PWM) and pulse frequency modulation (PFM) for ultra-low brightness conditions. Upon receiving a brightness adjustment command from the user, the FPGA identifies the brightness adjustment range in the command and switches to the corresponding dimming mode. Dimming calculations are then performed to adjust the display brightness, ensuring it matches the brightness required by the dimming command. This guarantees a smooth transition across the entire brightness range and improves the display effect under ultra-low brightness conditions.

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

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

[0032] In specific implementation, the set brightness range is 0-685.2 cd / m². 2 Where 0 represents the minimum brightness of the display screen, 685.2 cd / m². 2 This indicates the maximum brightness of the display screen. The ultra-low brightness range is 0-2.29 cd / m². 2 The normal brightness range is 10.69-685.2 cd / m². 2 .

[0033] To more thoroughly illustrate the objectives, technical solutions, and advantages of the embodiments of the present invention, the specific implementation methods of the present invention will be described in detail below. The following description and explanation will be provided in conjunction with the accompanying drawings and examples. This method specifically includes:

[0034] (1) Define the range of luminance values ​​that the FPGA can receive as 0-685.2 cd / m². 2 0 indicates the minimum brightness of the display screen, 685.2 cd / m². 2 This represents the maximum brightness of the display screen. Users send brightness commands to the FPGA, which then processes the commands to autonomously adjust the screen brightness.

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

[0036] Among them, t H t represents the high-level on-time. L The duration of the low level.

[0037] The FPGA sets the duty cycle and frequency of the LED drive signal according to the input brightness command, so that the brightness of the display screen switches to the specified brightness value. The implementation process is shown in Figure 1.

[0038] (3) If the brightness is detected to be in the ultra-low brightness range, the FPGA performs PFM dimming calculation and maintains the high level for the duration t. H The input brightness quality data is converted into a corresponding LED drive signal by fixing and adjusting the frequency f. If the brightness is detected to be within the normal range, the FPGA performs PWM dimming calculations. Based on a pre-set calculation formula, the frequency f is kept fixed while the high-level on-time t is adjusted. H This method converts the input brightness quality data into corresponding LED driving signals. An example of the correspondence is shown in Table 1 below:

[0039] Table 1. Correspondence between LED driving signals and brightness command values

[0040] (4) In low-brightness conditions, the PFM brightness adjustment scheme is selected: When the brightness command is 0, the LED drive signal is always low, and the LED is not lit. When the brightness value is 0.34 cd / m², the LED brightness adjustment scheme is selected. 2 At this time, the LED drive signal frequency is 90Hz, corresponding to an output duty cycle of 0.0135%. When the brightness value is 1.15 cd / m²... 2 The LED driver signal frequency is 250Hz, corresponding to an output duty cycle of 0.0375%, and the brightness value is 2.29 cd / m². 2 At this time, the LED drive signal frequency is 500Hz, corresponding to an output duty cycle of 0.075%. Within the normal brightness adjustment range, the brightness value is 10.69-685.2 cd / m². 2 Even at this time, the PWM brightness adjustment scheme is still chosen to achieve the display brightness adjustment. The adjusted display maintains a brightness of 0.34-2.29 cd / m² at ultra-low brightness levels. 2 Normal brightness is 10.69-685.2 cd / m². 2 The display is normal at all times, and there is no discomfort to the human eye. There is no obvious flickering or jumping when adjusting the display brightness.

[0041] (5) The FPGA outputs the corresponding LED driving signal to the LED control chip to complete the driving process.

[0042] This invention, through the design of an ultra-low brightness adjustment method for a display screen, enables the product to meet the requirements of normal display under high brightness and high precision conditions. The conformity of the product design has been proven through corresponding type tests, achieving high brightness precision and wide brightness range adjustment of LED light sources.

[0043] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for adjusting ultra-low brightness of a display screen based on PWM and PFM, characterized in that, include: The FPGA receives brightness adjustment commands sent by the user, identifies the brightness adjustment range value in the brightness adjustment command, matches the brightness adjustment range value with the set brightness range value, and determines the dimming mode corresponding to the brightness adjustment range value; the dimming mode is either PFM dimming mode or PWM dimming mode. The brightness adjustment range value is processed according to the dimming calculation 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 ultra-low brightness adjustment transition method for a display screen based on PWM and PFM according to claim 1, characterized in that, The LED driving signal includes a duty cycle and a signal frequency, which are used to adjust the brightness of the display screen to a specified brightness value within the brightness adjustment range.

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

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

5. The ultra-low brightness adjustment transition method for a display screen based on PWM and PFM according to claim 4, characterized in that, The set brightness range is 0-685.2 cd / m². 2 Where 0 represents the minimum brightness of the display screen, 685.2 cd / m². 2 This indicates the maximum brightness of the display screen.

6. The ultra-low brightness adjustment transition method for a display screen based on PWM and PFM according to claim 5, characterized in that, The ultra-low brightness range is 0-2.29 cd / m². 2 The normal brightness range is 10.69-685.2 cd / m². 2 .

Images