CN101004894B

CN101004894B - Scan type LED display unit, and method for eliminating latent brightness of previous line

Info

Publication number: CN101004894B
Application number: CN200710000050XA
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: 2006-10-20
Filing date: 2007-01-08
Publication date: 2010-05-19
Anticipated expiration: 2027-01-08
Also published as: CN101004894A

Abstract

A method for eliminating front-line hidden bright of LED display device in scanning type includes detecting variation of line selection signal of said LED display device, generating a discharge control signal to discharge electric charge at output end of line actuator connected with positive pole of a front-line LED for eliminating off hidden bright of said front-line LED when certain LED is lightened up and variation of line selection signal of said LED display device is detected. The LED display device of scanning type applying said method is also disclosed.

Description

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, place on the leaded shelf, use epoxy sealing then, 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 flat pannel display field always, and rely on its unique high brightness, high strength, long-life, sliceable use, advantage such as convenient, flexible, make it show in the large tracts of land indoor and outdoor, especially in physical culture, 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 by 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: the circuit complexity, 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 LED display more and more adopts dynamic scan to realize 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, send the data of first row earlier by line driver, then by the row driver gating and light LED in first row, after this send the data of second row, 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 simultaneously by line driver and row driver control herein.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 gamma 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, is mainly used to receive 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.Control this row driver 94 and each line driver 92 by this row signal and this clock signal C lk, load signal Load, enable signal En and data-signal Data, 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, as 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 as 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 by 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 appearance is latent bright, and 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 severe more.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 is also relevant with emitting led number among the m+1.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 achieving the above object, the invention provides a kind of scan type LED display unit, it comprises: the 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, release electric charge on the output terminal of the line driver that connects previous row LED positive pole, 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 of the line driver that connects previous row LED positive pole, 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:

By 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 disconnected of the line driver of scan type LED display unit among Figure 19.

[embodiment]

The present invention is described in detail below in conjunction with accompanying drawing.

Scan type LED display unit of the present invention is mainly used in information such as the image that shows various peripheral hardwares (as 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 describes in detail.

These several rows LED can arrange in the mode of matrix, and under the bigger situation of display area, this LED can be arranged on some cell boards (as 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, as circuit board, also can be arranged in the display screen of various sizes as required.For convenience of explanation, Figure 1 shows that arranging of partial L ED, therefore be not limited thereto.

In the present embodiment, as shown in Figure 3, for convenience 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 by 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 describes in detail.

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, thus the output of output row decoding 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 by 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 (as 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 that is connected the corresponding row LED on this output terminal 121, the 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
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	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)	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)

HSEL2	HSEL1	HSEL0	The state of H1～H8
HSEL2	HSEL1	HSEL0	The state of H1～H8	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	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, be connected the output terminal 121 of this line driver 12, the negative pole correspondence of the LED on the 122......12n is connected on the row driver 14, 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 is mainly used to receive 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, thereby 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, as 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 allows 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 by this mode of lining by line scan.Therefore, these several rows LED is lighted successively.It should be noted that the described output terminal of lighting the line driver 12 that is meant certain LED of delegation correspondence is loaded is controlled by row driver 14 simultaneously.

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 as k) is lighted, loading on the output terminal of the line driver 12 that its previous row LED (capable as 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 line driver 12 of the capable LED correspondence of k-1 because this line driver 12 economize on electricity itself holds.Because the output terminal of the line driver 12 of the capable LED correspondence of k-1 is connected with this first resistance 1611, and this first resistance 1611 directly is connected with ground, thereby can be rapidly the output terminal of the line driver 12 of the capable LED correspondence of this k-1 be held very fast being released of electric charge (following detailed description) that produces because of economize on electricity, 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 line driver 12 of the capable LED correspondence 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 represents by 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 describes in detail) the used time from Vh (also being on-load voltage Vcc).Thereby can allow this Th less than this time interval easily by 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 column (as the p row) of this reverse-conducting to be easy to generate row.Specifically, after the output terminal of the line driver 12 of the capable LED correspondence of k+1 is loaded, the loading of the output terminal of the line driver 12 of the capable LED correspondence of k this moment is closed, if the signal that this row driver 14 obtains did not allow the LED (label is 132 among Fig. 5) that are in the capable and p of k+1 row luminous originally, but because label is 131 LED reverse-conducting, and form current return (consulting the arrow of dotted line among Fig. 5 and current direction) through this first resistance 1611, 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.

As 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, one 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, wherein this second resistance 1612 the other end be 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 determine 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 rapidly holds very fast being released of electric charge that produces with the output terminal of corresponding row driver 12 because of economize on electricity, has avoided this previous row LED to produce and has concealed bright drawback.And owing to comprise first voltage stabilizing diode 1613 in second discharge circuit, after therefore finishing 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 operating voltage Vh and described LED.When scan type LED display unit adopts when multi-colored led, because the minimum critical trigger voltage difference of every kind of color (as redness, green, blueness etc.) LED, Vled is meant of minimum in the minimum critical trigger voltage of this LED of all kinds herein.

Because this predetermined voltage is less than minimum critical trigger voltage Vled, therefore behind the charge discharging resisting on the output terminal of the line driver 12 of the capable LED correspondence 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 operating voltage Vcc and described 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, release electric charge on the output terminal of the line driver 12 that connects previous row LED positive pole, when this certain LED of delegation lights, produce latent brightly to eliminate this previous row LED, below describe in detail.

As optimal way, electric discharge device 16C receives the rising of the highest row selection signal HSEL0 of described 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 describes in detail.

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, as 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 as 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 describe in detail.

This OR circuit 152 is existing 74HC32 chip in the present embodiment, its the 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 by the 11st pin, control its discharge, will describe in detail below.Certainly, this OR circuit 152 is not limited 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 operating voltage, the other end respectively with the 15th pin, the 7th pin of described 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 by 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).

By adjusting Cx and Rx, make Tcloutx drop to the time T h of Vled greater than the output end voltage of line driver 12, thereby guarantee at Tcloutx in the time, voltage on the capable LED positive pole of k is dropped to Vled or following, 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 describes in detail.Wherein the value of this Th can be calculated by following formula:

Th≈(2×(Vh-Vled)×Cp×R)/(Vh+Vled)

As 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.

As 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 by the 4th resistance 1615.

By 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, (also being on the LED positive pole) also comprises the output terminal discharge to the driver 12 of the LED correspondence 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 operating voltage Vcc, when the respective column of row driver 14 is opened, it will normally luminous that this row LED goes up predetermined luminous LED, and that concealing can not appearred owing to discharge in the output terminal of the line driver 12 of the LED correspondence that moves ahead is bright, 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 by triode Q1, Q2......Q8.Increase the 4th resistance 1615 may command velocities of discharge, the computing formula by above Th as can be known.

Extremely shown in Figure 13 as Fig. 8, be that the example explanation is come the latent bright principle of elimination previous row LED by electric discharge device 16C now: when code translator 11 is exported by the row decoding that decoding produces with the capable LED of k, the line driver 12 of turning off the capable LED correspondence of k, because economize on electricity is held, at the output terminal of the line driver 12 of the capable LED correspondence of k since economize on electricity hold former thereby can produce virtual height voltage (Vh as shown in figure 13).Because in the line driver 12 of turning off the capable LED correspondence 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 by 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 allow triode Q1, Q2......Q8 conducting, allow the electric charge on the output terminal of line driver 12 of the capable LED correspondence of k discharge.By 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 line driver 12 of the capable LED correspondence 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 allows the capable LED of k light, thereby avoid the capable LED of k latent bright.

Therefore, by 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 to 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.

As shown in figure 16, this discharge selecting arrangement is 138 code translators, realize by 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 respectively, HSEL1, HSEL2, then it is 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 by second voltage stabilizing diode 18, the row decoding output terminal of its chips 74HC156 and the row decoding output terminal of described 74HC138 chip stagger one, also promptly when the output terminal of the line driver 12 of the capable LED correspondence of the row decoding output terminal of described 74HC138 chip seed selection k, the output terminal of the line driver 12 of the capable LED correspondence of k-1 before the row decoding output terminal of this chip 74HC156 is then chosen seeds, so that realization is discharged to the electric charge on the output terminal of the line driver 12 of the LED correspondence that moves ahead, below describe in detail.Wherein the length fibrous root of Th is determined 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 by 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 by electric discharge device 16D with the capable LED of k equally: when described 74HC138 chip is exported by the row decoding that row selection signal HSEL0, HSEL1, HSEL2 decoding are produced, load the output terminal of the line driver 12 of the capable LED correspondence of k+1, and turn off loading on the output terminal of line driver 12 of the capable LED correspondence of k, because economize on electricity is held, at the output terminal of the line driver 12 of the capable LED correspondence 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 line driver 12 of the capable LED correspondence of k; And in the line driver 12 of turning off the capable LED correspondence of k, as described in the 3rd embodiment, this charge/discharge control circuit 15 produces CLOUTX as discharge control signal, control the corresponding row decoding output terminal of electric charge by this chip 74HC156 of output terminal of the line driver 12 of the capable LED correspondence of this k, introduce ground connection from the 8th pin.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 allows the capable LED of k light, thereby avoid the capable LED of k latent bright.

For the output terminal of the line driver 12 of keeping the capable LED correspondence 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.

As 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 will reload (as Figure 17 and Figure 18) behind the line output row signal delay Tcloutx, just when being in enabled state, forbids this enable signal this row decoding output, 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 of implementing 10, 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 of the line driver 12 that connects previous row LED positive pole, 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 by the superimposed pulse signal behind the exclusive disjunction as this discharge control signal CLOUTX.

And, step 2) also comprise the step of control described 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 forbids this row decoding output when this enable signal is in enabled state.

As optimal way, this discharge control signal CLOUTX only selects and the output terminal of line driver 12 of controlling the previous row LED correspondence 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 described LED, and poor greater than the minimum critical trigger voltage Vled of operating voltage Vcc (or Vh) and described LED.

Although by 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 technical field personnel understand.

Claims

1. scan type LED display unit, it comprises the several rows driver, row driver and several rows LED, it connects the positive pole of corresponding row LED towards the output terminal of each line driver, 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 line decoder, and the electric discharge device that is connected with this several rows output end of driver, this line decoder is deciphered row selection signal, and forming several rows decoding output, the output terminal of this several rows decoding connects with the input end of corresponding line driver respectively; Described electric discharge device also receives the rising of the highest row selection signal of this row selection signal medium frequency and the variation of decline, and according to the variation of this row selection signal, make when certain LED of delegation is lighted or before, release electric charge on the output terminal of the line driver that connects previous row LED positive pole, with eliminate this previous row LED when this certain LED of delegation lights, produces conceal bright.

2. scan type LED display unit as claimed in claim 1, it is characterized in that: described electric discharge device comprises charge/discharge control circuit and discharge circuit, this charge/discharge control circuit receives the rising of the highest row selection signal of described row selection signal medium frequency and the variation of decline, the output discharge control signal is controlled this discharge circuit discharge.

3. scan type LED display unit as claimed in claim 2, it is characterized in that: described discharge circuit comprises the some triodes that are connected with the corresponding row output end of driver respectively, the base stage of each triode receives described discharge control signal, grounded emitter, collector connects the corresponding row output end of driver.

4. scan type LED display unit as claimed in claim 3 is characterized in that: the collector of described triode is connected to described corresponding row output end of driver by resistance.

5. scan type LED display unit as claimed in claim 2, it is characterized in that: described discharge circuit comprises the discharge selecting arrangement, this discharge selecting arrangement has some discharges control output end, this discharge control output end connects with the output terminal of corresponding line driver respectively, this discharge selecting arrangement is deciphered described row selection signal, brings in the output of the line driver of the previous row LED correspondence of selecting the selected LED of delegation that will load of described line decoder and discharges; This discharge selecting arrangement receives described discharge control signal simultaneously, and the electric charge of controlling on the output terminal of this selecteed line driver discharges.

6. scan type LED display unit as claimed in claim 5, it is characterized in that: described discharge control output end is connected to the output terminal of corresponding line driver respectively by stable-pressure device, this stable-pressure device will maintain predetermined voltage to the voltage on should the output terminal of line driver after releasing, this predetermined voltage is less than the minimum critical trigger voltage of described LED, and poor greater than the minimum critical trigger voltage of operating voltage and described LED.

7. scan type LED display unit as claimed in claim 5 is characterized in that: described discharge selecting arrangement is 74HC156.

8. scan type LED display unit as claimed in claim 6 is characterized in that: described stable-pressure device is a voltage stabilizing diode, and the positive pole of this voltage stabilizing diode connects with the output terminal of corresponding line driver, negative pole and corresponding discharge control output end connection.

9. as each described scan type LED display unit in the claim 2 to 8, it is characterized in that: described discharge control signal is also controlled described line decoder as enable signal, forbids described row decoding output when this enable signal is in enabled state.

10. as each described scan type LED display unit in the claim 2 to 8, it is characterized in that: described charge/discharge control circuit comprises steady state trigger, timing circuit and OR circuit; This steady state trigger detects the rising of the highest row selection signal of described row selection signal medium frequency and descend to change, and output rising pulse and falling pulse are to this OR circuit; This OR circuit should the rising pulse and falling pulse carry out passing to described discharge circuit as this discharge control signal behind the exclusive disjunction; This timing circuit is connected with this steady state trigger, and controls the time of this rising pulse and falling pulse respectively.

11. scan type LED display unit as claimed in claim 10 is characterized in that: described steady state trigger comprises monostalbe trigger 74HC123,74HCT123,74ACT123 or 74LS123 chip.

12. scan type LED display unit as claimed in claim 10, it is characterized in that: described timing circuit comprises resistance and electric capacity, one end of this resistance is connected with operating voltage, and the other end is connected with electric capacity with described steady state trigger respectively, the other end ground connection of this electric capacity.

13. scan type LED display unit as claimed in claim 10 is characterized in that: described OR circuit comprises 74HC32,74HCT32,74ACT32 or 74LS32 chip.

14. a method of eliminating the scan type LED display unit forward moving hidden brightness 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 of the line driver that connects previous row LED positive pole, with eliminate this previous row LED when this certain LED of delegation lights, produces conceal bright;

Wherein, the rising that is changed to the highest row selection signal of frequency of described row selection signal and the variation that descends;

Wherein, this discharge control signal is to produce like this: when the row selection signal that detects this scan type LED display unit changes, produce rising pulse and falling pulse, this rising pulse and falling pulse by the superimposed pulse signal behind the exclusive disjunction as this discharge control signal.

15. the method for elimination scan type LED display unit forward moving hidden brightness as claimed in claim 14 is characterized in that: step 2) also comprise the step of control described rising pulse and falling pulse output time length.

16. the method as each described elimination scan type LED display unit forward moving hidden brightness in the claim 14 to 15 is characterized in that, also comprises step: row selection signal is deciphered, and formed several rows decoding output; And described discharge control signal is forbidden described row decoding output as the enable signal of row selection signal output when this enable signal is in enabled state.

17. the method as each described elimination scan type LED display unit forward moving hidden brightness in the claim 14 to 15 is characterized in that: described discharge control signal is only selected and the output terminal of line driver of controlling the previous row LED correspondence of the selected LED of delegation that will load of line decoder is released.

18. the method as each described elimination scan type LED display unit forward moving hidden brightness in the claim 14 to 15 is characterized in that: described discharge control signal is controlled the output terminal of the line driver of all row LED correspondences simultaneously and is released.

19. method as each described elimination scan type LED display unit forward moving hidden brightness in the claim 14 to 15, it is characterized in that: the voltage of the output terminal of the line driver of described connection previous row LED positive pole maintains predetermined voltage after releasing, this predetermined voltage is less than the minimum critical trigger voltage of described LED, and poor greater than the minimum critical trigger voltage of operating voltage and described LED.