Patent Publication Number: US-11037529-B2

Title: Methods and storage media for dimming a display screen

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 16/328,735 filed on Feb. 27, 2019, which is a 35 USC § 371 U.S. national stage filing of International Patent Application No. PCT/CN2018/086764 filed on May 14, 2018, and claiming priority under the Paris Convention to Chinese Patent Application No. CN 201710524423.7 filed on Jun. 30, 2017, all of which are incorporated herein by reference for all that they teach and disclose without exclusion of any portion thereof. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the technology field of display, and more particularly, to methods, and storage media for dimming a display screen. 
     BACKGROUND 
     In some specific application fields (e.g., display screens for cockpits, aeronautical equipment, handheld devices and the like), display screens are desired to have a good dimming performance, so as to be able to be watched comfortably either in daytime or at night. However, since the traditional dimming technologies may reduce the display quality during the process of dimming, the problem that how to mitigate impacts on the display quality while dimming is very desired to be solved. 
     SUMMARY 
     In view of above, it is needed to provide methods and storage media for dimming a display screen in regard with the problem that how to mitigate impacts on the display quality while dimming 
     Provided is a method for dimming a display screen, including: acquiring a parameter value of the display screen to be adjusted, the parameter value corresponding to a brightness of the display screen; comparing the parameter value to a first set threshold and a second set threshold respectively; when the parameter value is equal to or greater than the first set threshold, entering a first phase, and performing dimming on the display screen, under a one-pulse condition, via both emission dimming mode and source dimming mode, or source dimming mode, to adjust duty ratio of PWM (Pulse Width Modulation) to a first duty ratio, wherein the duty ratio of PWM refers to a ratio of efficiency level in a frame to be displayed by the display screen; when the parameter value is less than the first set threshold, and is equal to or greater than the second set threshold, entering a second phase, and performing dimming on the display screen, under a multi-pulse condition, via both emission dimming mode and source dimming mode, or source dimming mode, to adjust duty ratio of PWM to a second duty ratio; and when the parameter value is less than the second set threshold, entering a third phase, and performing dimming on the display screen, under another multi-pulse condition, via emission dimming mode, to adjust duty ratio of PWM to a third duty ratio, wherein the second set threshold is less than the first set threshold, and the second duty ratio is less than the first duty ratio, the third duty ratio is less than the second duty ratio. 
     Under the multi-pulse condition, the duty ratio of PWM is changed one by one in sequence, along with sequentially happenings of pulses in the multi-pulse condition. By such a dimming method, the brightness can be adjusted into more accurate volume. It would be more stable to emit light. 
     After acquiring a parameter value of the display screen to be adjusted, the parameter value will be compared with a set threshold to obtain a comparison result, and a corresponding dimming mode will be determined according to the comparison result to perform dimming on the display screen according to the method, apparatus, storage medium and electronic device for dimming a display screen as described above. Since various dimming modes have different performances with different brightnesses, if only one dimming mode is determined for dimming, the display quality may be reduced with the brightness with which the one dimming mode does not perform good. Therefore, the above method for dimming a display screen that determines a dimming mode according to a comparison result may overcome the deficiency caused by determining only one dimming mode, and may further mitigate impacts on the display quality while dimming. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purpose of illustrating the technical solutions of the embodiments of the present disclosure or of the prior art more explicitly, the accompanying drawings to be used necessarily for the description of the embodiments or the prior art will be briefly described below. Apparently, the accompanying drawings described below are part of the embodiments of the disclosure only, and accompanying drawings of the other embodiments may further be acquired based on these accompanying drawings herein without creative efforts to those of ordinary skill in the art. 
         FIG. 1  is a flow diagram of the method for dimming a display screen provided by an implementation. 
         FIG. 2  is a specific flow diagram of one of the embodiments of the method for dimming a display screen of the implementation shown in  FIG. 1 . 
         FIG. 3  is a circuit diagram of one of the embodiments of the pixel driving module involved in the implementation shown in  FIG. 1 . 
         FIG. 4  is a flow diagram of another embodiment of the method for dimming a display screen of the implementation shown in  FIG. 1 . 
         FIG. 5  is a block diagram of the apparatus for dimming a display screen provided in another implementation. 
         FIG. 6  shows a duty ratio of PWM changes along with sequentially happenings of pulses in the multi-pulse condition. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     To facilitate understanding the present disclosure, it will be described hereinafter more thoroughly in reference with the relative accompanying drawings. The preferred embodiments of the present disclosure are provided in the accompanying drawings. However, the present disclosure may be implemented in various forms, and not limited in the embodiments described herein. In contrast, the objective of providing these embodiments is to understand the disclosed description of the present disclosure more thoroughly. 
     All technical and scientific terms as used herein have the same meaning as commonly understood by those skilled in the art, unless those defined otherwise in context. The terms as used herein in the description of the present disclosure are for the purpose of describing particular embodiments only, and are not intended to be limiting of the present disclosure. The term “and/or” as used herein includes arbitrary and all combinations of one or more of the associated listed items. 
     One implementation provides a method for dimming a display screen, which may be performed by a peripheral drive chip for controlling the display screen. Specifically, the display screen may drive a pixel by a thin-film transistor. Specifically, the display screen, for example, includes a pixel matrix, a row driving module and a column driving module. The pixel matrix includes a plurality of pixel driving modules and a plurality of pixels, each of which is controlled by one of the pixel driving modules. The row driving module sends a scanning signal to each of the pixel driving modules via a row (scanning) address bus. The column driving module sends a data signal to each of the pixel driving modules via a column (data) address bus. The peripheral drive chip, which is responsible for processing and transmitting data, sending control signals and the like functions of the whole display screen, is electrically connected to the row driving module and the column driving module respectively. The peripheral drive chip is consisted of, e.g., a single-chip microcomputer (or FPGA) and a peripheral module. 
     In reference with  FIG. 1 , the method for dimming a display screen provided in the present implementation includes the following steps. 
     At step S 100 , a parameter value of the display screen to be adjusted is acquired. In such a context, the parameter value has a correspondence with a brightness of the display screen. 
     In such a context, the parameter value of the display screen to be adjusted implies that it is expected to adjust the parameter of the display screen to the parameter value. The fact that the parameter value has a correspondence with a brightness of the display screen implies that the parameter value will change in turn if the brightness is changing The parameter value is for example a brightness value, a voltage value, a current value, or a gray scale. The parameter value may be set by a user via an interactive interface of the device provided with the display screen, and the parameter value set by the user is sent to the peripheral drive chip by the CPU of the device after the user setting is accomplished. Alternatively, the parameter value to be adjusted may also be generated automatically by the CPU or the peripheral drive chip (i.e., having an automatic dimming functionality). For example, it is assumed that the parameter value is a brightness value, it is possible then to provide a light sensor configured to detect an external light intensity. The CPU or the peripheral drive chip generates a brightness value suitable for the user to watch according to the light intensity value detected by the light sensor, and this brightness value serves as the brightness value to be adjusted. 
     At step S 200 , the parameter value is compared with a set threshold to obtain a comparison result, and a corresponding dimming mode is determined according to the comparison result to perform dimming on the display screen. 
     At this step, a different dimming mode may be determined when the comparison result is different. For example, when the parameter values falls within different ranges, a dimming mode having a better dimming performance than that within the other ranges is determined to perform the dimming By way of example, it is assumed that the impact of the first dimming mode on the display quality with a parameter value within a first range is less than the impact of the first dimming mode on the display quality with a parameter value within a second range, while the impact of the second dimming mode on the display quality with the parameter value within the second range described above is less than the impact of the second dimming mode on the display quality with the parameter value within the first range described above. Thereby, if it is determined that a parameter value falls in the first range, the first dimming mode described above is then used to perform dimming, while if it is determined that the parameter value falls in the second range, the second dimming mode is then used to perform dimming, so that the display quality can be improved while dimming. 
     Since various dimming modes have different performances with different brightnesses, if only one dimming mode is determined for dimming, the display quality may be reduced with the brightness with which the one dimming mode does not perform good. Therefore, the above method for dimming a display screen that determines a dimming mode according to a comparison result may overcome the deficiency caused by determining only one dimming mode, and may further mitigate impacts on the display quality while dimming 
     In one of the embodiments, the display screen described above drives a pixel by a thin-film transistor (TFT). Furthermore, the step S 200  as described above includes the following steps in reference with  FIG. 2 . 
     At step S 210 , a first dimming mode is adopted to perform the dimming on the display screen when it is determined that the brightness corresponding to the parameter value is less than the set threshold. A voltage of a data signal received by a pixel driving module in the display screen is not changed during a process of the dimming in the first dimming mode. 
     In such a context, the set threshold is for example between 70 nits and 90 nits. Optionally, the set threshold is 80 nits. One of the pixel driving modules is shown as in  FIG. 3 . In this pixel driving module, included are a TFT T 1 , a TFT T 2 , a TFT T 3 , a capacitor C 1  and a pixel D 1 . In such a context, a gate and a drain of the TFT T 1  are connected respectively to the row address bus and the column address bus. Furthermore, the signals received by the gate and the drain of the TFT T 1  correspond to the scanning signal (Vscan) and the data signal (Vdata). In the embodiment shown in  FIG. 3 , thus the voltage of the data signal received by the drain of the TFT T 1  is not changed during the process of the dimming, but the dimming is performed by changing input signals from other devices in the pixel driving module in the first dimming mode. 
     If the dimming is performed by changing the voltage of the data signal during the process of the dimming, the lower the brightness value to be adjusted is, the higher the voltage of the data signal is required to be. In such a context, it will increase the difference in characteristics of the TFTs, resulting in occurring the phenomenon of uneven brightness in the row direction of the screen. In this embodiment, thus when the brightness corresponding to the parameter value to be adjusted is less than the set threshold, the adopted first dimming mode then performs the dimming not by changing the voltage of the data signal, but in other manners, so as to avoid occurring the phenomenon of uneven brightness in the row direction of the screen resulted from the increase of the difference in characteristics of the TFTs. 
     In one of the embodiments, the step S 200  further includes adopting the second dimming mode, when it is determined that the parameter value is not less than the set threshold. In such a context, the step S 200  described above specifically includes the following steps in combination with the step S 210  of the embodiment in reference with  FIG. 4  as described above. 
     At step S 211 , it is determined whether the brightness corresponding to the parameter value is less than the set threshold. If it is positive, the step S 212  is performed. If it is negative, the step S 213  is performed. 
     At step S 212 , the first dimming mode is adopted. 
     At step S 213 , the second dimming mode is adopted. In such a context, the dimming is performed by adjusting the voltage of the data signal in the second dimming mode. 
     In this embodiment, thus when it is desired to be adjusted to a high brightness or a low brightness, different dimming modes are adopted respectively, i.e., the second dimming mode is adopted when it is desired to be adjusted to the high brightness, and the first dimming mode is adopted when it is desired to be adjusted to the low brightness. 
     In such a context, the second dimming mode is for example a source dimming mode. As shown in  FIG. 3 , the expression of current of the pixel D 1  is
 
 I   oled   =k ( VDD−V data) 2    (1),
 
wherein I oled  is the current of the pixel D 1 , and k is a coefficient. As known from the formula (1), since the voltage between the power supply VDD and the data signal (Vdata) plays a decisive role to the current of the pixel D 1 , adjusting the data signal (Vdata) means adjusting the current of the pixel D 1  while on the premise that the power supply VDD is unchanged, so as to achieve brightness adjustment. If it is desired to adjust the brightness to be higher, it is required then to reduce the voltage of the data signal (Vdata) If it is desired to adjust the brightness to be lower, it is required then to increase the voltage of the data signal (Vdata).
 
     In view of this, it is required to reduce the voltage of the data signal (Vdata) when it is desired to adjust the brightness to be higher in respect with the second dimming mode. When the voltage of the data signal (Vdata) is sufficiently low, the difference in characteristics of the TFTs is small enough to be ignored. It is required to increase the voltage of the data signal (Vdata) when it is desired to adjust the brightness to be lower, and the lower the brightness value to be adjusted, the higher the voltage of the data signal (Vdata) is required. When the data signal (Vdata) is sufficiently high, the difference in characteristics of the TFTs is so large that the phenomenon of uneven brightness in the row direction of the screen and color spots may occur. Therefore, if continuing to adopt the second dimming mode when it is desired to adjust the brightness lower, the display quality will be affected. In view of the situations described above, if it is desired to adjust the brightness corresponding to the parameter value to be lower than the set threshold in this embodiment, the second dimming mode is switched to the first dimming mode, so as to avoid the phenomenon of uneven brightness in the row direction. 
     Specifically, the dimming is performed by adjusting the illumination period of the pixel in each frame in the first dimming mode. Optionally, the first dimming mode is an EM (Emission) dimming mode. In such a context, the brightness of the pixel may be reduced by reducing the illumination period of each frame. For example, if the PWM (Pulse Width Modulation) signal is used to control the illumination period of the pixel, the illumination period of each frame may be then reduced by reducing the duty ratio of an active level (e.g., a low level) in the PWM signal, so as to reduce the brightness of the pixel. In such a context, the pixel illuminates only with the active level. 
     The working principle of the first dimming mode described above will be then illustrated in reference with  FIG. 3  as an example. If the first dimming mode is adopted, it is only required to adjust the duty ratio of the Vpwm signal applied to the gate of the TFT T 3 , but without changing the data signal (Vdata), to change the illumination period of the pixel D 1  in each frame, such that the brightness of the pixel D 1  may be adjusted. 
     Furthermore, if the dimming is performed by adjusting the duty ratio of the PWM in the first dimming mode, the dimming frequency is then fixed, where the phenomenon of photo screen rolling may occur under high brightness conditions. In this embodiment, thus if the parameter value to be adjusted is higher than the set threshold, the second dimming mode is adopted so as to avoid occurring the deficiency of the photo screen rolling described above, which further improves the display quality. 
     In a specific embodiment, the dimming process includes following phases. 
     A parameter value of the display screen to be adjusted is acquired, the parameter value corresponding to a brightness of the display screen. 
     The parameter value is compared to a first set threshold and a second set threshold respectively. 
     When the parameter value is equal to or greater than the first set threshold, it is in a first phase. In the first phase, the dimming process includes performing dimming on the display screen, via both emission dimming mode and source dimming mode, or the source dimming mode, under a one-pulse condition, to adjust duty ratio of PWM (Pulse Width Modulation) to a first duty ratio. 
     When the parameter value is less than the first set threshold, and is equal to or greater than the second set threshold, it is in a second phase. In the second phase, the dimming process includes performing dimming on the display screen, via both emission dimming mode and source dimming mode, or the source dimming mode, under a multi-pulse condition, to adjust the duty ratio of PWM to a second duty ratio. 
     The second set threshold is less than the first set threshold, and the second duty ratio is less than the first duty ratio. In the second phase, as shown in  FIG. 6 , the duty ratio of PWM under the multi-pulse condition is changed one by one in sequence, along with sequentially happenings of pulses in the multi-pulse condition. 
     When the parameter value is less than the second set threshold, it is in a third phase. In the third phase, the dimming process includes performing dimming on the display screen via the emission dimming mode, under another multi-pulse condition, to adjust the duty ratio of PWM to a third duty ratio less than the second duty ratio. In the third phase, as shown in  FIG. 6 , the duty ratio of PWM under the another multi-pulse condition is changed one by one in sequence, along with sequentially happenings of pulses in the another multi-pulse condition. 
     Under the multi-pulse condition, the duty ratio of PWM is changed one by one in sequence, along with sequentially happenings of pulses in the multi-pulse condition. By such dimming process, the brightness can be adjusted into more accurate volume. It would be more stable to emit light. 
     Optionally, the first set threshold ranges between 350 nits and 380 nits, and the second set threshold ranges between 200 nits and 240 nits. 
     Optionally, the first duty ratio is greater than 90%, and the second duty ratio is greater than 80%. 
     Optionally, the third duty ratio ranges between substantially 1% and substantially 88%. 
     Under the above volume condition, display uniformity can be improved, and brightness can be adjusted to a suitable state. The quality of displaying can be improved. 
     The duty ratio of PWM refers to a ratio of efficiency level in a frame to be displayed by the display screen. The display screen emits under the efficiency level. The efficiency level can be low level, or high level. 
     In the emission dimming mode, brightness is adjusted by adjusting the duty ratio of PWM. 
     In the source dimming mode, brightness is adjusted by adjusting data voltage. 
     Multi-pulse in the above multi-pulse condition refers to four pulses, eight pulses, sixteen pulses, or other integral multiples of four pulses happened in a frame. 
     It is to be illustrated that  FIG. 1 ,  FIG. 2  and  FIG. 4  are the flow schematic diagrams of the method of the embodiments of the present disclosure. It should be understood that although all of the steps in the flow diagrams of  FIG. 1 ,  FIG. 2  and  FIG. 4  are shown sequentially as the indication of the arrows, these steps do not have to be performed in such sequence as indicated by the arrows. Performing these steps does not have any sequential limitation such that these steps may be performed in another sequence, unless it is illustrated explicitly in the context. Further, at least a part of steps of  FIG. 1 ,  FIG. 2  and  FIG. 4  may include multiple sub-steps or stages which may be performed at different times rather have to be accomplished at the same time, which may be performed in turn or alternately with the other steps or at least a part of the sub-steps or stages of the other steps, rather have to be performed sequentially. 
     In another implementation, provided is an apparatus for dimming a display screen in reference with  FIG. 4 , which includes the below components. 
     A parameter value acquisition module  110 , or can be called into parameter value acquisition module, is configured to acquire a parameter value of the display screen to be adjusted. In such a context, the parameter value has a correspondence with a brightness of the display screen. 
     A dimming determination module  120 , or can be called into dimming selection module  120 , is configured to compare the parameter value with a set threshold to obtain a comparison result, and to determine a corresponding dimming mode according to the comparison result to perform dimming on the display screen. 
     In one of the embodiments, the display screen drives a pixel by a thin-film transistor. 
     Furthermore, the dimming determination module  120  includes the following elements. 
     A first dimming determination module, configured to adopt a first dimming mode to perform the dimming on the display screen when it is determined that the brightness corresponding to the parameter value is less than the set threshold. A voltage of a data signal received by a pixel driving module in the display screen is not changed during a process of the dimming in the first dimming mode. 
     In one of the embodiments, the dimming determination module  120  further includes: 
     a second dimming determination module, configured to adopt the second dimming mode when it is determined that the parameter value is not less than the set threshold. The dimming is performed by adjusting the voltage of the data signal in the second dimming mode. 
     In one of the embodiments, the dimming is performed by adjusting an illumination period of a pixel of the display screen in each frame in the first dimming mode. 
     In one of the embodiments, the parameter value is a brightness value. 
     In one of the embodiments, the set threshold is between 1 nit and 500 nits. 
     It should be illustrated that the apparatus for dimming a display screen provided in this implementation corresponds to the method for dimming a display screen of the implementation described above, thus it will not be described repeatedly here. 
     In a further implementation, provided is a storage medium. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), or the like. The storage medium stores a program operable to be executed by a processor to perform the following steps of: 
     acquiring a parameter value of the display screen to be adjusted, wherein the parameter value has a correspondence with a brightness of the display screen; and 
     comparing the parameter value with a set threshold to obtain a comparison result, and determining a corresponding dimming mode according to the comparison result, and performing dimming on the display screen. 
     It is to be illustrated that the steps performed by the processor in this implementation correspond to the method for dimming a display screen of the implementation described above, thus they will not be described here repeatedly. 
     In a still further implementation, provided is an electronic device, such as a mobile phone, computer or the like. The electronic device includes a peripheral drive chip and a display screen. The peripheral drive chip includes a processor and a memory storing a program operable to be executed by a processor to cause the processor to perform the following steps of: 
     acquiring a parameter value of the display screen to be adjusted, wherein the parameter value has a correspondence with a brightness of the display screen; and 
     comparing the parameter value with a set threshold to obtain a comparison result, and determining a corresponding dimming mode according to the comparison result, and performing dimming on the display screen. 
     It is to be illustrated that the steps performed by the processor in this implementation correspond to the method for dimming a display screen of the implementation described above, thus they will not be described here repeatedly. 
     All of the technical features in the embodiments described above can be employed in arbitrary combinations. For purpose of simplifying the description, not all arbitrary combinations of the technical features in the embodiments described above are described. However, as long as such combinations of the technical features are not contradictory, they should be considered as within the scope of the disclosure in the specification. 
     The above embodiments are merely illustrative of several implementations of the disclosure, and the description thereof is more specific and detailed, but should not be deemed as limitations to the scope of the present disclosure. It should be noted that variations and improvements will become apparent to those skilled in the art to which the present disclosure pertains without departing from its scope. Therefore, the scope of the present disclosure is defined by the appended claims