CN101937648A - Ordinary constant flow source driving chip-based method for controlling grey scale display of light-emitting diode (LED) - Google Patents
Ordinary constant flow source driving chip-based method for controlling grey scale display of light-emitting diode (LED) Download PDFInfo
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Abstract
The invention relates to an ordinary constant flow source driving chip-based method for controlling grey scale display of a light-emitting diode (LED). In the method, gray scales, which are scattered in two different refreshing periods and only account for a half of output enabling (OE) subfield time, of an image in the same frame period are integrated into one refreshing period and gray scales which are scattered in four different refreshing periods and only account for a quarter of the OE subfield time are integrated into one refreshing period, namely, gray scales, which are scattered in N different refreshing periods and only account for one Nth of the OE subfield time, in the same frame period are integrated into one refreshing period so as to form a complete OE subfield and make full use of the subfield time. Under the control of a specific algorithm in a control system, an ordinary constant flow source driving chip can meet all requirements and achieve the effects of high refreshing rate, high gray scale, high picture quality, high LED utilization ratio and smooth gray scale transition, so that the raw material cost of LED display equipment is saved. Certain performance of the ordinary constant flow source driving chip controlled by the method is even superior to that of a built-in pulse-width modulation constant flow source driving chip.
Description
One, technical field
The technical field of the invention is that LED shows the field.The LED image display control technology of the band gray scale that especially common constant current source chip for driving drives comprises LED big screen display screen, LED lamp bar, LED lamp decoration etc.
Two, background technology
The control method based on common constant current source chip for driving of main flow is that (the image frame per second based on the PC computing machine commonly used is 60Hz with the source image frame cycle in the industry at present, its frame period is 16.66ms) be divided into some refresh cycles, these refresh cycle sums are exactly the refresh rate of LED display device with the product of source images frame per second.In each refresh cycle, show each GTG successively, thereby high GTG demonstration time of weight longly produces different gray scales according to weight separately.It is fixing to be subject to the source image frame cycle, and this control method can't solve the more and more higher refresh rate that current LED display requires, more and more higher GTG, more and more higher LED utilization factor, more level and smooth gray scale and show the contradiction between these performance requirements.Because higher refresh rate means the fixing source image frame cycle is divided into the more refresh cycle, the shared time of each refresh cycle still less can't show more high gray; Simultaneously, show that more high gray certainly will produce how little OE pulsewidth, thus these little OE pulsewidths some can't be influenced LED display device grayscale transition flatness by the performance of common constant current source chip for driving, influence image quality; Promptly enable by other GTG of middle grade of common constant current source chip for driving performance, its OE weight still is not enough to take a whole OE field time, causes the LED utilization factor to reduce, and the luminance loss is bigger.
Along with the development of LED display industry, its requirement to refresh rate, grey exponent number is more and more higher to satisfy demands such as graceful image quality, live no vision flicker, high LED utilization factor.Though the built-in PWM constant current source chip for driving that occurs on the market can satisfy these requirements preferably at present, thereby LED display device raw materials cost is increased much because the more common constant current source chip for driving of built-in PWM chip for driving cost cost exceeds several times.And the display control unit based on common constant current source chip for driving of current main flow in the industry can't solve the contradiction between high refresh rate, low brightness losses, the high gray.
Three, summary of the invention
The present invention seeks to: propose a kind of method of the control common LED based on common constant current source chip for driving, make its driving LED display device, especially critical natures such as the refresh rate of LED big screen display screen, high gray, GTG transition satisfy the demands simultaneously.
Technical scheme of the present invention is: based on the LED gray scale display control method of common constant current source chip for driving, in the same frame period with image, the gray scale that only accounts for 1/2 OE field time that is dispersed in 2 different refresh cycles is incorporated into a refresh cycle, comprises that also the gray scale that only accounts for 1/4 OE field time that will be dispersed in 4 different refresh cycles is incorporated into a refresh cycle in addition ... the rest may be inferred (that is: the GTGs that only accounts for 1/N OE field time of the N in the same frame period different refresh cycles is incorporated into a refresh cycle make full use of sub-field time to constitute complete OE).
If one based on common constant current source chip for driving and use the LED display of traditional gradation control method, its grey exponent number is 8 (8bits), be R, G, B respectively has 256 gray scales, and (expressible color is 256 x, 256 x 256=16,777,216 looks), if the sub-field time of GTG is T, and its high gray time is 8T, the 8bits GTG time is respectively 8T so, 4T, 2T, T, T, T, T, T (total GTG time is 19T in the refresh cycle), and its effective OE time is respectively 8T, 4T, 2T, T, T/2, T/4, T/8, T/16 (the OE calendar time is (16-1/16) T in the refresh cycle).If the frame period is that F is (if the image frame per second is 60Hz, F=16.666ms then), the refresh cycle number is F/ (19T) so, refresh rate is about 1s/ (19T), minimum OE pulsewidth is T/16, the LED utilization factor is about (16-1/16) T/ (19T)=83.88%, and the luminance loss is about (1-83.88%)=16.12%.
In like manner, when requiring grey exponent number to be 16 (16bits), be R, G, B respectively has 65536 gray scales, and (expressible color is 65536x65536x65536=281,474,976,710,656 looks), the 16bits GTG time is respectively 8T, 4T, 2T, T, T, T, T, T, T, T, T, T, T, T, T, T (total GTG time is 28T in the refresh cycle), and its effective OE time is respectively 8T, 4T, 2T, T, T/2, T/4, T/8, T/16, T/32, T/64, T/128, T/256, T/512, T/1024, T/2048, T/4096 (the OE calendar time is (16-1/4096) T in the refresh cycle), refresh cycle is counted R=F/ (27T) so, refresh rate is about 1s/ (27T), minimum OE pulsewidth is T/4096, the LED utilization factor is about (16-1/4096) T/ (27T)=59.26%, and the luminance loss is about (1-59.26%)=40.74%.
This shows, classic method control is based on the LED display of common constant current source chip for driving, the ash exponent number is high more, its refresh rate is low more, the LED utilization factor is low more, and the luminance loss is high more, and minimum OE pulsewidth is more little so that can't be showed by the LED chip for driving, thereby cause grayscale transition unsmooth, adverse effect such as image quality is not good enough.And under equal conditions, the present invention can make above-mentioned each performance parameter roughly satisfy following formula:
During the 8bits GTG: the refresh cycle counts R and satisfies: 15R+even (R/2)+even (R/4)+even (R/8)+even (R/16)=F/T; (wherein, even () function is the function that rounds up, and promptly decimal place is advanced 1 processing).Minimum OE pulsewidth is: (R% 16) T, (wherein, % is for getting surplus meeting); The LED utilization factor is: ((16-1/16) RT/F) * 100%;
The luminance loss is: 100%-((16-1/16) RT/F) * 100%;
During the 16bits GTG:
Refresh cycle counts R and satisfies: 15R+even (R/2)+even (R/4)+even (R/8)+even (R/16)+even (R/32)+even (R/64)+even (R/128)+even (R/256)+even (R/512)+even (R/1024)+even (R/2048)+even (R/4096)=F/T;
Wherein, even () function is the function that rounds up, and promptly decimal place is advanced 1 processing).
Minimum OE pulsewidth is: (R% 4096) T, (wherein, % is for getting surplus meeting);
The LED utilization factor is: ((16-1/4096) RT/F) * 100%;
The luminance loss is: 100%-((16-1/4096) RT/F) * 100%;
Sub-field time T is by LED display addressing number and the decision of data clock frequency/period, as the addressing number is 512, the data clock frequency is 12.5MHz (cycle is 80ns), and so sub-field time T=128x80ns=10.24us can draw the following table of comparisons for 1/4 scan screen:
This shows, the V-PWM technology is to the comprehensive lifting of these critical natures of LED display, thereby can realize high refresh rate, high LED utilization factor, low brightness losses and can be promoted image quality (current common constant current source chip for driving can show other minimum OE pulsewidth of 35ns level, as MBI5036 etc.) fully by the minimum OE pulsewidth that common constant current source is obtained the chip performance.
Like this, can't almost do not existed by the minimum pulsewidth OE of the low GTG of common constant current source chip for driving performance, grayscale transition is more level and smooth, and image quality is better.And the almost whole maximum usings in all OE fields, the LED utilization factor also just significantly improves, and the luminance loss significantly reduces, and the time that remains out after integrating simultaneously can continue to distribute the more refresh cycle, thus also just significantly raising of refresh rate.
Useful result of the present invention: solved the contradiction between many critical natures that the insurmountable LED display device of traditional main flow control method based on common constant current source chip for driving requires.Be based on the every performance requirement of common constant current source chip for driving LED display device and all be met, avoid using the constant current source chip for driving of expensive built-in PWM, thereby save the raw materials cost of LED display device.And the present invention adopts special algorithm to control common constant current source chip for driving from the control system aspect also to satisfy above-mentioned all requirements, reach high refresh rate simultaneously, high gray high image quality, high LED utilization factor, grayscale transition are level and smooth, thereby save the raw materials cost of LED display device.On some performance, by the common constant current source chip for driving of the present invention's control even above built-in PWM constant current source chip for driving.
Four, description of drawings
Fig. 1 is a common LED constant current source chip for driving frame diagram
Fig. 2 is the LED constant current source chip for driving frame diagram of built-in PWM
(traditional) of Fig. 3 current main-stream is based on the control timing figure of common constant current source LED chip for driving
Fig. 3-the 1st, the control timing partial enlarged drawing of common constant current source LED chip for driving among Fig. 3
Fig. 4 the present invention (V-PWM) is based on the control timing figure of common constant current source LED chip for driving
Five, embodiment
In the prior art source image frame cycle (the image frame per second based on the PC computing machine commonly used is 60Hz, and its frame period is 16.66ms) is divided into some refresh cycles, these refresh cycle sums are exactly the refresh rate of LED display device with the product of source images frame per second.In each refresh cycle, show each GTG successively, longly produce different gray scales thereby the high GTG of weight shows the time according to weight separately.And the present invention is based on FPGA design, its image transmissions, picture frame buffer memory, gray scale take place, OE integration etc. realizes by fpga logic between the different refresh cycle.
Consider from the whole source image frame cycle, because the view data that the different refresh cycles show in the same frame period is identical, the low GTG OE of those vacant one whole OE field times in the different refresh cycles can be integrated, be incorporated into a refresh cycle as the GTG that only accounts for 1/2 OE field time that will be dispersed in 2 different refresh cycles, the GTG that only accounts for 1/4 OE field time that is dispersed in 4 different refresh cycles is integrated (promptly entirely also) to a refresh cycle ... and the like (that is: the GTGs that only accounts for 1/N OE field time of the N in the same frame period different refresh cycles is incorporated into a refresh cycle (can in first refresh cycle) make full use of sub-field time) to constitute complete OE.Like this, can't almost do not existed by the minimum pulsewidth OE of the low GTG of common constant current source chip for driving performance, grayscale transition is more level and smooth, and image quality is better.And the almost whole maximum usings in all OE fields, the LED utilization factor also just significantly improves, and the luminance loss significantly reduces, and the time that remains out after integrating simultaneously can continue to distribute the more refresh cycle, thus also just significantly raising of refresh rate.The product that the present invention is based on the DBT-Q2009 of Depuda Electronic Tech Co., Ltd., Nanjing platform realizes that other software platform also can be realized the inventive method certainly.
Fig. 3-1 (the control timing partial enlarged drawing based on common constant current source LED chip for driving of current main-stream)
DCLK/OE/LE among Fig. 3-1 is corresponding with signal of the same name among Fig. 1; DR/DG/DB is the RGB data, and is corresponding with SDI among Fig. 1; The A/B signal is a row selection signal, and the B signal is one high and one low promptly to be finished a refresh cycle; OE one a low height promptly shows a bit GTG; Can find out among the figure that the grey exponent number that each refresh cycle finishes is identical, a large amount of low imperfect OE field times of GTG are by vacant, cause refresh rate to improve, the LED utilization factor can't improve, the luminance loss can't reduce, simultaneously, and can't be more by the little OE pulsewidth of common constant current source LED chip for driving response, cause grayscale transition unsmooth, image quality is not good.
Among the control timing figure that the present invention is based on common constant current source LED chip for driving of Fig. 4, DCLK/OE/LE is corresponding with signal of the same name among Fig. 1; DR/DG/DB is the RGB data, and is corresponding with SDI among Fig. 1; The A/B signal is a row selection signal, and the B signal is one high and one low promptly to be finished a refresh cycle; OE one a low height promptly shows a bit GTG; Can find out among the figure that the grey exponent number that each refresh cycle finishes may be different, because the GTG in this refresh cycle may be merged by other refresh cycle same gray level.But each sub-field time all is fully utilized, and the refresh cycle number increases, and refresh rate is improved, the LED utilization factor improves, and the luminance loss reduces, simultaneously, can't almost do not existed by the little OE pulsewidth of common constant current source LED chip for driving response, from but grayscale transition is level and smooth, strengthen image quality.The embodiment of the invention is incorporated into first refresh cycle to constitute complete OE with the GTG that only accounts for 1/N OE field time of the N in the same frame period different refresh cycles, makes full use of sub-field time.
Claims (2)
1. based on the LED gray scale display control method of common constant current source chip for driving, it is characterized in that the GTG that only accounts for 1/2 OE field time that image is dispersed in 2 different refresh cycles in the same frame period is incorporated into a refresh cycle, the GTG that only accounts for 1/4 OE field time that is dispersed in 4 different refresh cycles is incorporated into a refresh cycle, the GTG that only accounts for 1/N OE field time that is about to N the different refresh cycles in the same frame period is incorporated into a refresh cycle to constitute complete OE, makes full use of sub-field time.
2. the LED gray scale display control method based on common constant current source chip for driving according to claim 1 is characterized in that the GTG that image is only accounted for 1/N OE field time in the same frame period merges to a refresh cycle.
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| CN104050925A (en) * | 2014-06-27 | 2014-09-17 | 深圳市奥拓电子股份有限公司 | Displaying method and device for LED display screen and LED display screen |
| CN104751780A (en) * | 2013-12-31 | 2015-07-01 | 乐金显示有限公司 | Hybrid Driving Manner Organic Light Emitting Diode Display Apparatus |
| CN106373516A (en) * | 2016-10-31 | 2017-02-01 | 北京集创北方科技股份有限公司 | Led display device and driving method thereof |
| CN107068040A (en) * | 2017-02-14 | 2017-08-18 | 江苏利鼎微系统有限公司 | A kind of one of small spacing all-colour LED display module 256 scan method |
| CN111163559A (en) * | 2020-01-17 | 2020-05-15 | 铠强科技(平潭)有限公司 | Data processing circuit and light emitting diode driving circuit |
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| CN107068040A (en) * | 2017-02-14 | 2017-08-18 | 江苏利鼎微系统有限公司 | A kind of one of small spacing all-colour LED display module 256 scan method |
| CN113129808A (en) * | 2019-12-31 | 2021-07-16 | Tcl集团股份有限公司 | Driving method and driving device of LED array and display device |
| CN111163559A (en) * | 2020-01-17 | 2020-05-15 | 铠强科技(平潭)有限公司 | Data processing circuit and light emitting diode driving circuit |
| CN111163559B (en) * | 2020-01-17 | 2022-02-22 | 铠强科技(平潭)有限公司 | Data processing circuit and light emitting diode driving circuit |
| CN111601430A (en) * | 2020-06-15 | 2020-08-28 | 深圳市美矽微半导体有限公司 | LED drive control method and device |
| CN111601430B (en) * | 2020-06-15 | 2022-09-09 | 深圳市美矽微半导体有限公司 | LED drive control method and device |
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