CN101866613B

CN101866613B - Scanning type LED display device and method for eliminating forward moving hidden brightness thereof

Info

Publication number: CN101866613B
Application number: CN2009102107712A
Authority: CN
Inventors: 邵寅亮
Original assignee: Beijing Jushu Digital Technology Development Co Ltd
Current assignee: Suzhou Wei You Intellectual Property Operation Co ltd
Priority date: 2007-01-08
Filing date: 2007-01-08
Publication date: 2012-05-23
Anticipated expiration: 2027-01-08
Also published as: CN101866613A

Abstract

The invention relates to a scanning type LED display device and a method for eliminating forward moving hidden brightness thereof, wherein the scanning type LED display device comprises a plurality of row drivers, line drivers, a plurality of line LEDs and a discharging device, wherein the output end of the row drivers is connected with the discharging device. The method for eliminating forward moving hidden brightness comprises the following steps: 1) detecting the row selection signal variation of the time intervals between the row driving time and the line driving time of some row of LEDs of the scanning type LED display device; and 2) setting the discharging time of the discharging device to be smaller than the time intervals, generating a discharging control signal when the row selection signal variation of the scanning type LED display is detected so that electric charges on the output end of the row drivers on the positive electrodes of the front row of LEDs are discharged and connected for eliminating the hidden brightness generated by the front row of LEDs when or before a row of LEDs are lightened.

Description

Scan type LED display unit and eliminate the method for its forward moving hidden brightness

The application is dividing an application of " scan type LED display unit and eliminate the method for its forward moving hidden brightness ", and the applying date of former patented claim is that January 8, application number in 2007 are that 200710000050.X, patent of invention name are called " scan type LED display unit and eliminate the method for its forward moving hidden brightness ".

[technical field]

The present invention relates to a kind of LED display device, relate in particular to a kind of scan type LED display screen; In addition, the invention still further relates to a kind of method of the LED of elimination display device forward moving hidden brightness.

[background technology]

The English of light emitting diode is Light Emitting Diode (LED); Its basic structure is an electroluminescent semiconductor material, places on the leaded shelf, uses epoxy sealing then all around; When it is in the forward duty (two ends add forward voltage); When electric current flowed to negative electrode from the LED anode, semiconductor material will be luminous, and the power of light is relevant with size of current.For many years; LED is playing the part of important role in the FPD field always; And rely on its unique high brightness, high strength, long-life, sliceable use, advantage such as convenient, flexible, make it show, especially in physical culture in the large tracts of land indoor and outdoor; Advertisement, the application in fields such as finance, exhibition, traffic is quite extensive.

Light-emitting diode display is according to showing that control mode can be divided into static state and two kinds of scannings.The static demonstration all controlled separately through hardware each LED in the LED electronic display with exactlying, and all LED while of whole LED display screen is controlled.This mode great advantage is that program design is simple, and the picture flicker free.But there is fatal shortcoming in this design: complicated circuit, and the hardware utilization factor is low, and cost is huge.

And along with the progress of LED manufacturing process, the brightness of LED is significantly improved, and the increasing employing dynamic scan of LED display is realized procedure for displaying at present, and this mode is that LED all on the display screen is divided into the N group, and every group is called delegation.If will show a frame picture, see the data of first row earlier off through line driver, then through the row driver gating and light the LED in first row, after this see the data of second row off, same gating, light the second row LED; Successively that all line scannings are intact, promptly provided the picture of a frame, note lighting and be meant that the LED of delegation is controlled by line driver and row driver simultaneously here.Therefore, the sweep frequency of this display packing is high more, and picture is just stable more; The picture that human eye is looked reaches stable, and sweep frequency is wanted 120 hertz at least, and the standard in Europe is 300 hertz; Make the picture after video camera is taken reach stable effect, sweep frequency then needs higher.

A kind of exemplary scanning type LED display device 90 shown in Figure 19, it comprises the line decoder 91 that receives row selection signal (HSEL).The row selection signal HSEL of this line decoder 91 receiving control systems (not shown) output, and after this row selection signal deciphered, output several rows decoding output (H1A～HnA).Several rows driver 92 corresponding this several rows that receive are deciphered output, then from its output terminal 921, output row signal (H1～Hn), also be driving voltage, be carried in the LED (seeing also label 93 among Figure 19) that positive pole is connected corresponding drive output 921.This row driver 94 is connected with the negative pole of LED, mainly is used for receiving from clock signal C lk, load signal Load, enable signal En and the data-signal Data of this control system output, and whether the LED that controls each row luminous and fluorescent lifetime.Through this row signal and this clock signal C lk, load signal Load, enable signal En and data-signal Data this row driver 94 of control and each line driver 92, thereby whether each LED of may command is luminous, shows the information such as drawing, literal of needs.

But often there is latent bright problem in this scan type LED display unit 90.Specifically, like Figure 19 and shown in Figure 20, each line driver 92 generally all uses chip FDS4953 two-way P-channel field-effect transistor (PEFT) pipe or other chips, is easy to generate economize on electricity appearance problem.Below be that example describes with chip FDS4953 two-way P-channel field-effect transistor (PEFT) pipe.In sweep circuit shown in figure 19; Owing to use this chip FDS4953 two-way P-channel field-effect transistor (PEFT) pipe, after the capable line driver 92 of m is turned off, because the problem that economize on electricity is held; Can store electric charge on the drive output 921 of the line driver 92 that this m is capable; Thereby the positive pole at the capable LED of m produces a virtual height voltage, and the respective column that this virtual height voltage remains to this row driver 94 is always opened, and its life period is Tx.

When m+1 is capable when being lighted, this moment, the correspondence of row driver 94 was classified open mode as.Because the positive pole of the LED that m is capable has virtual height voltage; Therefore the electric charge on the capable LED positive pole of m will discharge through the respective column of row driver 94; The therefore original capable LED that should not work of m; M+1 is capable lighted in, also occur latent brightly, this latent bright time T y is critical the lighting the needed time of voltage Vled from this virtual height voltage to LED.

In addition, the factor of the latent bright degree of influence has two aspects: on the one hand: the smallest point light current of LED.The smallest point light current is more little, and is latent bright more severe.Early stage LED is because brightness is low, and the smallest point light current is bigger, so latent bright problem is not obvious.Yet,, cause latent bright problem to come obvious more approximately recently along with the raising of LED brightness.On the other hand: line-scanning frequency.Line-scanning frequency has determined the number of times that each row is lighted in the unit interval, and line-scanning frequency is high more, and the latent bright number of times of LED per second is just many more for above-mentioned reasons, and the latent bright problem of row will be serious more.

In addition, the latent bright degree of influence also with m+1 in emitting led number relevant.Because emitting led number is many more, current paths is just many more, and the electric current that each path flows through is less, and the velocity ratio of discharge is very fast, therefore causes each conducting LED latent bright not obvious; When only a LED is luminous among the m+1, so fluorescent lifetime is long, thereby causes this LED luminous brighter, occurs stronger latent bright.

When LED display goes out existing latent bright problem, will make should be bright in the display frame LED around have should not be bright LED shinny, thereby influence picture display effect.Along with the reinforcement of LED brightness and the raising of LED screen line-scanning frequency, serious more to the display effect influence of picture.

In view of this, the method that a kind of scan type LED display unit that overcomes above defective is provided and eliminates forward moving hidden brightness becomes the technical task that present urgent need solves.

[summary of the invention]

One object of the present invention is to provide can effectively eliminate forward moving hidden brightness to improve the scan type LED display unit of display effect.

Another object of the present invention is to provide can effectively eliminate the method for forward moving hidden brightness with the elimination forward moving hidden brightness of raising display effect.

For realizing above-mentioned purpose; The present invention provides a kind of scan type LED display unit; It comprises: several rows driver, row driver and several rows LED, wherein the output terminal of each line driver connects the positive pole of corresponding row LED, the output terminal of this row driver be connected this line driver on the corresponding connection of negative pole of LED; Wherein this scan type LED display unit also comprises the electric discharge device that is connected with this several rows output end of driver; Make when certain LED of delegation is lighted or before, the electric charge on the output terminal that connects the anodal line driver of previous row LED of releasing, with eliminate this previous row LED when this certain LED of delegation lights, produces conceal bright.

In addition, the present invention also provides a kind of method of eliminating the scan type LED display unit forward moving hidden brightness, and it may further comprise the steps:

1) variation of the row selection signal of detection scan type LED display unit;

2) when the variation of the row selection signal that detects this scan type LED display unit; Produce a discharge control signal; Make when certain LED of delegation is lighted or before; Release electric charge on the output terminal that connects the anodal line driver of previous row LED, with eliminate this previous row LED when this certain LED of delegation lights, produces conceal bright.

Compared with prior art, the output terminal of each line driver of scan type LED display unit of the present invention is connected with electric discharge device, thereby can effectively eliminate the scan type LED display unit forward moving hidden brightness to improve its display effect.

In addition, compared with prior art, the method that the present invention eliminates the scan type LED display unit forward moving hidden brightness comprises following characterization step:

Through said method, can effectively eliminate the scan type LED display unit forward moving hidden brightness to improve its display effect.

[description of drawings]

Fig. 1 is the partial circuit principle sketch of first embodiment of the invention scan type LED display unit.

Fig. 2 is the circuit theory sketch of line decoder among Fig. 1.

Fig. 3 is the circuit theory sketch of the invention first embodiment electric discharge device.

Fig. 4 is the invention first embodiment electric discharge device sequential synoptic diagram of electric charge on this output terminal of releasing after loading on the driver output end is closed of being expert at.

Fig. 5 produces the latent bright circuit theory sketch of row.

Fig. 6 is the circuit theory sketch of the invention second embodiment electric discharge device.

Fig. 7 is the invention second embodiment electric discharge device sequential synoptic diagram of electric charge on this output terminal of releasing after loading on the driver output end is closed of being expert at.

Fig. 8 is the partial circuit principle sketch of invention the 3rd embodiment scan type LED display unit.

Fig. 9 is the circuit theory sketch of the steady state trigger of charge/discharge control circuit among Fig. 8.

Figure 10 is the circuit theory sketch of the OR circuit of charge/discharge control circuit among Fig. 8.

Figure 11 is the circuit theory sketch of invention the 3rd embodiment electric discharge device.

Figure 12 is the signal sequence synoptic diagram of invention the 3rd embodiment scan type LED display unit circuit.

Figure 13 is invention the 3rd embodiment electric discharge device sequential synoptic diagram of electric charge on this output terminal of releasing after loading on the driver output end is closed of being expert at.

Figure 14 is the partial circuit principle sketch of invention the 4th embodiment scan type LED display unit.

Figure 15 is the circuit theory sketch of line decoder among Figure 14.

Figure 16 is the circuit theory sketch of invention the 4th embodiment electric discharge device.

Figure 17 is the signal sequence synoptic diagram of invention the 4th embodiment scan type LED display unit circuit.

Figure 18 is invention the 4th embodiment electric discharge device sequential synoptic diagram of electric charge on this output terminal of releasing after loading on the driver output end is closed of being expert at.

Figure 19 is the partial circuit principle sketch of existing scan type LED display unit.

Figure 20 is the output terminal sequential synoptic diagram that electric charge discharges on this output terminal after loading is closed or broken off of the line driver of scan type LED display unit among Figure 19.

[embodiment]

Below in conjunction with accompanying drawing the present invention is elaborated.

Scan type LED display unit of the present invention is mainly used in information such as the image that shows various peripheral hardwares (like computer, player, off-line system etc.) and pass over, literal, but is not limited thereto.

As shown in Figure 1; First embodiment of the invention scan type LED display unit 10 mainly comprises line decoder 11, line driver 12, several rows LED (seeing also label 13 among Fig. 1), row driver 14, cascade circuit (not shown) and electric discharge device 16A etc., below specifies.

These several rows LED can arrange with the mode of matrix, and under the bigger situation of display area, this LED can be arranged on some cell boards (like circuit board), is combined into a big display screen then; Under the less situation of display screen, also can directly be arranged in a substrate, like circuit board, also can be arranged in the display screen of various sizes as required.For the ease of explanation, shown in Figure 1 is arranging of partial L ED, therefore is not limited thereto.

In the present embodiment, as shown in Figure 3, for the ease of explanation, adopt eight row LED, omitted column drive circuit; This code translator 11 is existing 74HC138 chip (as shown in Figure 2), but is not limited thereto, and according to the line number of LED, also can adopt the code translator of other models.This 74HC138 chip receives row selection signal HSEL0, HSEL1, HSEL2 through the 1st pin, the 2nd pin and the 3rd pin; Then it is deciphered; From the 15th pin, the 14th pin ... the 7th pin produces row decoding output H1A, H2A......H8A; Its signal sequence can be consulted Figure 12, below specifies.

As shown in Figure 1; Each row decoding output connects with a corresponding line driver 12; This line driver 12 is used for row selection signal HSEL0, HSEL1, the HSEL2 of receiving control system (not shown) output, and this control system can be the plain full-color control system of real image of Shenzhen Linsn Technology Development Co., Ltd. etc.This 74HC138 chip will be deciphered this row selection signal HSEL0, HSEL1, HSEL2, thereby the output row decoding is exported H1A, H2A......H8A, and this is a prior art, needn't give unnecessary details at this.

This line driver 12 is existing FDS4953 chip (seeing also label 129 among Fig. 3) in the present embodiment, but is not limited thereto, and also can form this line driver through triode or metal-oxide-semiconductor.

As shown in Figure 3, two row decodings of each FDS4953 chip may command output to the output terminal of two corresponding line drivers 12.This FDS4953 chip is equivalent to switch; Control work voltage VCC (like 5 volts or 3 volts etc.) is carried in output terminal 121, the 122......128 of corresponding row FDS4953; Thereby the driving voltage of loading is provided for the positive pole be connected the last corresponding row LED of this output terminal 121,122......128; Also promptly from each output terminal 121,122......128 output row signal H1, H2......H8, specifically output situation sees also following table and Figure 12.

HSEL2	HSEL1	HSEL0	The state of H1～H8
				0	0	0	H1 is high (1), and all the other are low (0)
0	0	1	H2 is high (1), and all the other are low (0)
				0	1	0	H3 is high (1), and all the other are low (0)
0	1	1	H4 is high (1), and all the other are low (0)
				1	0	0	H5 is high (1), and all the other are low (0)
1	0	1	H6 is high (1), and all the other are low (0)
				1	1	0	H7 is high (1), and all the other are low (0)
1	1	1	H8 is high (1), and all the other are low (0)

As shown in Figure 1, the negative pole correspondence that is connected the last LED of output terminal 121, the 122......12n of this line driver 12 is connected on the row driver 14, and it is luminous that this row driver 14 and this each line driver 12 are controlled LED jointly, comes information such as displayed image, literal.Specifically; This row driver 14 mainly is used for receiving clock signal C lk, load signal Load, enable signal En and the data-signal Data of this control system output; Drive the LED of delegation that is loaded by corresponding row driver 12, and control that it is luminous, to show the picture of expection.In the present embodiment, this row driver 14 is the MBI5026 chip, also can be ZQ9722, the ZQ9729 chip of Beijing Zhongqing Micro-digit Equipment Development Co., Ltd; Under the more situation of LED column number, but this chip of cascade, thus may command is than the LED of multiple row; Control the luminous of LED, and control the length of its fluorescent lifetime, thereby realize higher gray shade scale; This is a prior art, needn't give unnecessary details at this.Certainly, this row driver 14 also is not limited thereto.

In addition, the cascade circuit that do not draw in the drawings, this cascade circuit is generally the 74HC245 chip, also is not limited thereto, like 74HCT245,74ACT245,74LS245.This cascade circuit is mainly used in and distributes various data, signal to control this row driver 14 and this each line driver 12, and this is a prior art, needn't give unnecessary details at this.

During use, this code translator 11 lets the output terminal 121 of line driver 12,122......12n load successively.After the positive pole of each row LED was loaded, it is luminous that corresponding row driver will be controlled among this row LED those LED, and those are not luminous, show information such as predetermined image, literal through this mode of lining by line scan.Therefore, these several rows LED is lighted successively.It should be noted that the said output terminal of lighting the line driver 12 that is meant that certain LED of delegation is corresponding is loaded simultaneously by row driver 14 controls.

In this first embodiment, as shown in Figure 1, this electric discharge device 16A comprises some first discharge circuits 161 that are connected with output terminal 121, the 122......12n of corresponding row driver 12 respectively.

As shown in figures 1 and 3, this first discharge circuit 161 comprises first resistance 1611, and these first resistance, 1,611 one ends are connected the output terminal of corresponding line driver 12, other end ground connection.Therefore; When the LED of certain delegation (capable like k) is lighted; Loading on the output terminal of the line driver 12 that its previous row LED (capable like k-1, just the LED of delegation that lighted of adjacent last time) is corresponding is closed (or capable signal at stop of the output terminal of this this line driver 12).But, thereby after the loading on the capable LED of k-1 is switched off, some electric charges are arranged at the output terminal of the corresponding line driver 12 of the capable LED of k-1 because this line driver 12 economize on electricity itself holds.Because the output terminal of the line driver 12 that the capable LED of k-1 is corresponding is connected with this first resistance 1611; And this first resistance 1611 directly is connected with ground; Thereby the electric charge that the output terminal of line driver 12 that can be rapidly that the capable LED of this k-1 is corresponding produces because of the economize on electricity appearance is released very soon (following detailed description); Therefore when the capable LED of k is lighted, avoid the capable LED of k-1 to produce latent bright drawback, thereby improved the display effect of LED display.

Because when the capable LED of k is lighted in the process, generally be that the drive output 121 of the corresponding line driver 12 of the capable LED of k loads earlier, row driver 14 just begins to drive the LED of respective column then.And the time interval between this loading and row driving beginning is shorter.As shown in Figure 4, Th discharge time of this first resistance 1611 is littler than this time interval.Wherein this Th representes through this first resistance 1611 this electric charge of releasing; Thereby make the voltage of output terminal of this line driver 12 drop to the critical driving minimum voltage of LED Vled (Vled is meant one minimum the minimum critical trigger voltage of this LED of all kinds, below specifies) the used time from Vh (also being on-load voltage Vcc).Thereby can let this Th less than this time interval easily through the resistance value of regulating first resistance 1611.

Although the electric discharge device 16A among first embodiment can reach the effect of eliminating forward moving hidden brightness preferably, there is certain defective in it: owing to increase by first resistance 1611, thus increase the power consumption of display system.As shown in Figure 5, in addition, as a LED among the capable LED of k (label is 131 among Fig. 5) during because of the breakdown reverse-conducting of other factors, thereby it is latent bright to cause the LED of the LED place row (like the p row) of this reverse-conducting to be easy to generate row.Specifically; After the output terminal of the corresponding line driver 12 of the capable LED of k+1 is loaded; The loading of the output terminal of the line driver 12 that the capable LED of k this moment is corresponding is closed; To be in the capable LED (label is 132 among Fig. 5) with p row of k+1 luminous if the signal that this row driver 14 obtains was not allowed originally, but because label is 131 LED reverse-conducting, and form current return through this first resistance 1611 (consulting the arrow of dotted line among Fig. 5 and current direction); Thereby make that label is that 132 LED is luminous, cause the latent bright generation of row.The latent bright generation of these row mainly due to: have the LED of reverse-conducting to exist; Simultaneously on-load voltage and reverse-conducting LED are expert at difference between the voltage on the output terminal of corresponding line driver 12 greater than Vled.

Fig. 6 and second embodiment of the invention shown in Figure 7, therefore different electric discharge devices that are with first embodiment of second embodiment wherein omit other elements, among second embodiment with first embodiment in components identical use identical label, needn't give unnecessary details at this.

Like Fig. 1 and shown in Figure 6; In this second embodiment; Electric discharge device 16B comprises second discharge circuit (not label) that is connected with output terminal 121, the 122......12n of corresponding row driver 12 respectively; This second discharge circuit comprises second resistance 1612 and first stable-pressure device of series connection, and an end of this second resistance 1612 is connected with the output terminal of corresponding row driver 12, and the other end is connected with this first stable-pressure device; The other end ground connection of this first stable-pressure device.

This first stable-pressure device is first voltage stabilizing diode 1613 in the present embodiment, and wherein the other end of this second resistance 1612 is to be connected with the positive pole of this first voltage stabilizing diode 1613; The minus earth of this first voltage stabilizing diode 1613.

The discharge principle of this second discharge circuit and first discharge circuit 161 are basic identical, and just the time of Th need confirm that other are identical according to this second resistance 1612 and first stable-pressure device at this moment, needn't give unnecessary details at this.Therefore second discharge circuit equally also can be released the output terminal of corresponding row driver 12 because of the electric charge that the economize on electricity appearance produces rapidly very soon, has avoided this previous row LED to produce latent bright drawback.And owing to comprise first voltage stabilizing diode 1613 in second discharge circuit, after therefore accomplishing when releasing, this first voltage stabilizing diode 1613 is kept a stable predetermined voltage Vp because of its characteristic at positive pole.

As shown in Figure 7, this predetermined voltage Vp is less than the minimum critical trigger voltage Vled of this LED, and poor greater than the minimum critical trigger voltage Vled of WV Vh and said LED.When scan type LED display unit adopts when multi-colored led, because the minimum critical trigger voltage of every kind of color (like redness, green, blueness etc.) LED difference, Vled is meant of minimum in the minimum critical trigger voltage of this LED of all kinds here.

Because this predetermined voltage is less than minimum critical trigger voltage Vled; Therefore behind the charge discharging resisting on the output terminal of the corresponding line driver 12 of the capable LED of k; The voltage of the output terminal of this line driver 12 maintains predetermined voltage Vp at this moment; This Vp is not enough to drive any LED among the capable LED of k, thereby can avoid effectively that the capable LED of this k produces latent bright in that k+1 is capable when lighting.In addition; Because this predetermined voltage is poor greater than the minimum critical trigger voltage Vled's of WV Vcc and said LED; Even the existence of reverse-conducting LED is arranged; On-load voltage and reverse-conducting LED are expert at difference between the voltage on the output terminal of corresponding line driver 12 less than Vled, thereby can effectively avoid being listed as latent bright generation, thereby further improve the display effect of LED display.

Fig. 8 is to third embodiment of the invention shown in Figure 13, different electric discharge devices that are of the 3rd embodiment wherein with first, second embodiment, among the 3rd embodiment with preceding two embodiment in the identical label of components identical use, needn't give unnecessary details at this.

In the present embodiment; This electric discharge device 16C receives the variation of this row selection signal HSEL; And according to the variation of this row selection signal, when guaranteeing that certain LED of delegation is lighted or before, the electric charge on the output terminal that connects the anodal line driver 12 of previous row LED of releasing; When this certain LED of delegation lights, produce latent brightly to eliminate this previous row LED, below specify.

As optimal way, electric discharge device 16C receives the rising of the highest row selection signal HSEL0 of said row selection signal medium frequency and the variation of decline.In the present embodiment, this electric discharge device 16C comprises charge/discharge control circuit 15 and the 3rd discharge circuit 163.Wherein this charge/discharge control circuit 163 receives the rising of the highest row selection signal HSEL0 of this row selection signal medium frequency and the variation of decline, and output discharge control signal CLOUTX controls 163 discharges of the 3rd discharge circuit, below specifies.

In the present embodiment, this charge/discharge control circuit 15 comprises steady state trigger 151, OR circuit 152 and timing circuit.Wherein this steady state trigger 151 is existing monostalbe trigger 74HC123 chip in the present embodiment, is not limited thereto certainly, like trigger flip-flop etc. or 74HCT123,74ACT123,74LS2123.This steady state trigger 151 is mainly used in the variation that detects this row selection signal HSEL.In the present embodiment, the 2nd pin, the 9th pin of this steady state trigger 151 are connected to HSEL0, also are the highest row selection signal HSEL0 of frequency.

To shown in Figure 12,, produce a high level pulse CLUP like Fig. 9 from the 5th pin of steady state trigger 151 as HSEL0 during by low uprising; As HSEL0 during, produce a high level pulse CLDOWN from the 13rd pin of steady state trigger 151 by high step-down.High level pulse CLUP, CLDOWN from the 5th pin and the 13rd pin of this steady state trigger 151 comes out are transported to this OR circuit 152, carry out exclusive disjunction, below specify.

This OR circuit 152 is existing 74HC32 chip in the present embodiment; Its 13rd pin and the 12nd pin are used for receiving the 5th pin of this steady state trigger 151 and high level pulse CLUP, the CLDOWN that the 13rd pin comes out respectively, carry out exclusive disjunction then, with the high level pulse CLOUTX that superposes after the computing; As discharge control signal; Be delivered to the 3rd discharge circuit through the 11st pin, control its discharge, will specify below.Certainly, this OR circuit 152 does not limit to this 74HC32 chip, can be other circuit of realizing exclusive disjunction yet and realizes.

As shown in Figure 9, in order to control the time of the 3rd discharge circuit 163 discharges, this charge/discharge control circuit 15 is equipped with timing circuit.In the present embodiment; This timing circuit comprises the 3rd resistance 1614 and capacitor C 1, C2; One end of the 3rd resistance 1614 is connected with WV; The other end respectively with the 15th pin, the 7th pin of said steady state trigger 15, this other end also with capacitor C 1, C2 is connected simultaneously, the other end ground connection of this capacitor C 1, C2.In an embodiment, the appearance of resistance that can be through regulating the 3rd resistance 1614 and capacitor C 1, C2 is worth controls discharge time.Specifically, discharge time, Tcloutx=0.64 * Cx * (wherein Tcloutx was discharge time to Rx; Cx is the appearance value of capacitor C 1, C2; Rx is the resistance of the 3rd resistance 1614).

Through adjustment Cx and Rx; Make Tcloutx drop to the time T h of Vled, thereby guarantee at Tcloutx in the time, the voltage on the capable LED positive pole of k is dropped to Vled or following greater than the output end voltage of line driver 12; Avoid when k+1 is capable when lighting; Also be the respective column of row driver 14 when opening, the capable LED of k sends latent bright, below specifies.Wherein the value of this Th can be calculated through following formula:

Th≈(2×(Vh-Vled)×Cp×R)/(Vh+Vled)

Like Fig. 8 and shown in Figure 13, in this formula: Vh is the voltage of the output terminal of line driver 12 when loading; As previously mentioned, Vled is meant one minimum in the minimum critical trigger voltage of this LED of all kinds; Cp is that the economize on electricity of line driver 12 is held; R is the resistance value of the 3rd resistance 1614.

Shown in figure 11, the structure of all the 3rd discharge circuits 163 is identical, below only one of them is elaborated.The 3rd discharge circuit 163 is the output terminals that are connected corresponding line driver 12, is used to discharge electric charge.The 3rd discharge circuit 163 of the top comprises triode Q1 and the 4th resistance 1615 among Figure 11, and wherein the base stage a of this triode Q1 is connected with the 11st pin of this OR circuit 152, obtains high level pulse signal CLOUTX; The emitter e ground connection of this triode Q1; The collector b of this triode Q1 is connected to the output terminal of corresponding row driver 12 through the 4th resistance 1615.

Through this structure; When the 11st pin that receives this OR circuit 152 when a base stage connects the high level pulse signal CLOUTX (also being discharge control signal) transmit; All triode Q1, Q2......Q8 are with conducting; The output of all line drivers 12 is in discharge condition, and (also being on the LED positive pole) also comprises the output terminal discharge to the corresponding driver 12 of LED that moves ahead because the unnecessary electric charge that produces is held in economize on electricity on the output terminal that is not loaded thereby can discharge.

Because the positive pole of the capable LED that is loaded has WV Vcc; When the respective column of row driver 14 is opened; It will be normally luminous that this row LED goes up predetermined luminous LED, and the output terminal of the corresponding line driver 12 of LED that moves ahead is latent bright owing to not occurred by discharge, thereby improve image quality greatly.

It should be noted that the 4th resistance 1615 is selectable, when not having the 4th resistance 1615, only can realize above discharging function equally through triode Q1, Q2......Q8.Increase the 4th resistance 1615 may command velocities of discharge, can know through the computing formula of above Th.

Extremely shown in Figure 13 like Fig. 8; Existing is that the example explanation is come the latent bright principle of elimination previous row LED through electric discharge device 16C with the capable LED of k: when code translator 11 is exported through the row decoding that decoding produces; Turn off the corresponding line driver 12 of the capable LED of k; Because economize on electricity is held, at the output terminal of the corresponding line driver 12 of the capable LED of k since economize on electricity hold former thereby can produce virtual height voltage (Vh shown in figure 13).Because when turning off the corresponding line driver 12 of the capable LED of k; This charge/discharge control circuit 15 also detects the variation of row selection signal; Also promptly detect the variation that the highest row selection signal HSEL0 of frequency rises or descends, thereby produce high level pulse CLUP, CLDOWN.This high level pulse CLUP, CLDOWN produce the high level pulse CLOUTX that is produced by high level pulse CLUP, CLDOWN stack through OR circuit 152, as discharge control signal.This high level pulse CLOUTX will be delivered to the base stage a of triode Q1, Q2......Q8, thereby let triode Q1, Q2......Q8 conducting, let the electric charge on the output terminal of the corresponding line driver 12 of the capable LED of k discharge.Through regulating this Cx and Rx, make Tcloutx drop to the time T h of Vled, thereby make discharge time of triode Q1, Q2......Q8 greater than the time that virtual height voltage Vh is put into Vled greater than the output end voltage of the corresponding line driver 12 of the capable LED of k.Therefore,, there is not electric charge on the positive pole of the capable LED of k when k+1 is capable when lighting, or less than the critical charge amount that lets the capable LED of k light, thereby avoid the capable LED of k latent bright.

Therefore, through this electric discharge device 16C, scan type LED display unit of the present invention also can be eliminated the interference of forward moving hidden brightness fully, and the display frame display quality is provided.But third embodiment of the invention and first is implemented also to have same defective, needn't give unnecessary details at this.

Figure 14 is to fourth embodiment of the invention shown in Figure 180, and wherein the 4th embodiment is similar with the 3rd embodiment, but another kind of the 3rd discharge circuit is provided, among the 4th embodiment with first three embodiment in the identical label of components identical use, needn't give unnecessary details at this.

In the present embodiment, electric discharge device 16D comprises this another kind the 3rd discharge circuit 163 ' and charge/discharge control circuit 15, and wherein this charge/discharge control circuit 15 is identical with the 3rd embodiment, needn't give unnecessary details at this.

The 3rd discharge circuit 163 ' in the present embodiment comprises discharge selecting arrangement and some second stable-pressure devices; This second stable-pressure device is identical with first stable-pressure device among second embodiment; Be second voltage stabilizing diode 18, its principle of work is identical with first voltage stabilizing diode 1613, needn't give unnecessary details at this.

Shown in figure 16; This discharge selecting arrangement is 138 code translators; Realize through chip 74HC156 (label is 17 among Figure 16); Its principle of work is: this chip 74HC156 the 13rd pin, 3 pin and 1 pin receive row selection signal HSEL0, HSEL1, HSEL2 respectively, then it are deciphered, from the 4th pin, the 5th pin ... the 12nd pin produces the row decoding output terminal; Each row decoding output terminal is connected with the output terminal of corresponding row driver 12 through second voltage stabilizing diode 18; The row decoding output terminal of its chips 74HC156 and the row decoding output terminal of said 74HC138 chip stagger one, also promptly when the output terminal of the corresponding line driver 12 of the capable LED of the row decoding output terminal of said 74HC138 chip seed selection k, and the output terminal of the line driver 12 that the capable LED of k-1 was corresponding before the row decoding output terminal of this chip 74HC156 was then chosen seeds; So that realize the electric charge on the output terminal of the corresponding line driver 12 of LED that moves ahead is discharged, below specify.Wherein the length fibrous root of Th is confirmed according to the performance of this discharge selecting arrangement own.

The discharge control signal CLOUTX that this charge/discharge control circuit 15 produces passes to chip 74HC156 through the 2nd pin and 14 pin, and as its enable signal, thereby this chip of may command 74HC156 discharges.

Be that the example explanation is come the latent bright principle of elimination previous row LED through electric discharge device 16D with the capable LED of k equally: when said 74HC138 chip is exported through the row decoding that row selection signal HSEL0, HSEL1, HSEL2 decoding are produced; Load the output terminal of the corresponding line driver 12 of the capable LED of k+1; And turn off the loading on the output terminal of the corresponding line driver 12 of the capable LED of k; Because economize on electricity is held, at the output terminal of the corresponding line driver 12 of the capable LED of k since economize on electricity hold former thereby can produce virtual height voltage.This chip 74HC156 also exports the row decoding that row selection signal HSEL0, HSEL1, HSEL2 decoding produce simultaneously, selects the output terminal of the corresponding line driver 12 of the capable LED of k; And when turning off the corresponding line driver 12 of the capable LED of k; Of the 3rd embodiment; This charge/discharge control circuit 15 produces CLOUTX as discharge control signal; Control the electric charge of the output terminal of the corresponding line driver 12 of the capable LED of this k and decipher output terminal, introduce ground connection from the 8th pin through the corresponding row of this chip 74HC156.Therefore,, there is not electric charge on the positive pole of the capable LED of k when k+1 is capable when lighting, or less than the critical charge amount that lets the capable LED of k light, thereby avoid the capable LED of k latent bright.

For the output terminal of keeping the corresponding line driver 12 of the capable LED of k is kept certain voltage after releasing; It is latent bright to eliminate the row that cause because of damage LED reverse-conducting; Second voltage stabilizing diode 18 that the output terminal of the line driver 12 corresponding with the capable LED of this k connects; This second voltage stabilizing diode 18 identical with the principle of first voltage stabilizing diode 18 among second embodiment (consulting Figure 18) needn't be given unnecessary details at this.

Like Figure 14 and shown in Figure 15; In order to ensure further effectively eliminating the latent bright problem of row; This discharge control signal CLOUTX is also as the enable signal of 74HC138 (label is 11 ' among Figure 15); Thereby with reloading (like Figure 17 and Figure 18) behind the line output row signal delay Tcloutx, just, forbids this enable signal the output of this row decoding when being in enabled, the pressure reduction thereby the output terminal and the reverse-conducting LED that further dwindle the driver 12 of loading are expert between the output terminal of corresponding driver 12; Thereby further suppress the latent bright generation of row, improve display quality.And this method also can be used for above the 3rd embodiment.

According to the structure of the above the 3rd, the 4th scan type LED display unit 10 implemented, the method that the present invention eliminates scan type LED display unit 10 forward moving hidden brightness mainly comprises following step:

1) variation of the row selection signal HSEL of detection scan type LED display unit;

2) when the variation of the row selection signal HSEL that detects this scan type LED display unit; Produce a discharge control signal CLOUTX; Make when certain LED of delegation is lighted or before; Release electric charge on the output terminal that connects the anodal line driver 12 of previous row LED, with eliminate this previous row LED when this certain LED of delegation lights, produces conceal bright.

As optimal way, the rising that is changed to the highest row selection signal HSEL0 of frequency of this row selection signal HSEL and the variation that descends.

In addition; In step 2; This discharge control signal CLOUTX produces like this: when the row selection signal HSEL that detects this scan type LED display unit changes; Produce rising pulse CLUP and falling pulse CLDOW, this rising pulse CLUP and falling pulse CLDOW pass through superimposed pulse signal behind the exclusive disjunction as this discharge control signal CLOUTX.

And, step 2) also comprise the step of control said rising pulse CLUP and falling pulse CLDOW output time length.

As optimal way, this discharge control signal CLOUTX is as the enable signal of row selection signal output, and it is long-time to postpone row decoding output Tcloutx, just when this enable signal is in enabled, forbids this row decoding output.

As optimal way, this discharge control signal CLOUTX only selects and the output terminal of controlling the corresponding line driver 12 of the previous row LED of the line decoder 11 selected LED of delegation that will load is released.

As optimal way; The voltage of the output terminal of the line driver 12 of connection previous row LED maintains predetermined voltage after releasing; This predetermined voltage is less than the minimum critical trigger voltage Vled of said LED, and poor greater than the minimum critical trigger voltage Vled of WV Vcc (or Vh) and said LED.

Although through above embodiment the present invention is disclosed, scope of the present invention is not limited thereto, do not departing under the condition of the present invention design, more than each element can replace with the similar or equivalent element that affiliated person skilled is understood.

Claims

1. scan type LED display unit; It comprises several rows driver, row driver and several rows LED; Wherein the output terminal of each line driver connects the positive pole of corresponding row LED; The output terminal of this row driver be connected this line driver on the corresponding connection of negative pole of LED, it is characterized in that: this scan type LED display unit also comprises the electric discharge device that is connected with this several rows output end of driver, makes when certain LED of delegation is lighted or before; Release electric charge on the output terminal that connects the anodal line driver of previous row LED, with eliminate this previous row LED when this certain LED of delegation lights, produces conceal bright; Wherein, the drive output of the line driver that certain row LED is corresponding loads earlier, and row driver just begins to drive the LED of respective column then, drives the time interval between the beginning for this loading and row, and the discharge time of said electric discharge device is littler than this time interval; Be meant said discharge time through the said electric charge of releasing, thereby make the voltage of output terminal of said line driver drop to the critical used time of driving minimum voltage of LED from loading WV.

2. scan type LED display unit as claimed in claim 1; It is characterized in that: said electric discharge device comprises some second discharge circuits that are connected with the corresponding row output end of driver respectively; Each second discharge circuit comprises second resistance and the stable-pressure device of series connection, and this second resistance, one end connects with the output terminal of corresponding line driver, and the other end is connected with this stable-pressure device; The other end ground connection of this stable-pressure device; And this stable-pressure device is kept predetermined voltage after this is released, and this predetermined voltage is less than the minimum critical trigger voltage of said LED, and poor greater than the minimum critical trigger voltage that loads WV and said LED.

3. scan type LED display unit as claimed in claim 2 is characterized in that: said stable-pressure device is first voltage stabilizing diode, the minus earth of this first voltage stabilizing diode, and the other end of anodal and said second resistance is connected.

4. scan type LED display unit as claimed in claim 1; It is characterized in that: also comprise line decoder; This line decoder is deciphered row selection signal, and forms several rows decoding output, and this several rows decoding output terminal connects with the input end of corresponding line driver respectively.

5. scan type LED display unit as claimed in claim 1; It is characterized in that: the voltage that said electric discharge device connects the output terminal of the anodal line driver of previous row LED maintains predetermined voltage after releasing; This predetermined voltage is less than the minimum critical trigger voltage of said LED, and poor greater than the minimum critical trigger voltage of WV and said LED.

6. eliminate the method for scan type LED display unit forward moving hidden brightness according to claim 1 for one kind, it is characterized in that: may further comprise the steps:

2) when the variation of the row selection signal that detects this scan type LED display unit; Produce a discharge control signal; Make when certain LED of delegation is lighted or before; Release electric charge on the output terminal that connects the anodal line driver of previous row LED, with eliminate this previous row LED when this certain LED of delegation lights, produces conceal bright;

The voltage of the output terminal of the line driver that said connection previous row LED is anodal maintains predetermined voltage after releasing, this predetermined voltage is less than the minimum critical trigger voltage of said LED, and poor greater than the minimum critical trigger voltage of WV and said LED.