A kind of system of eliminating LED scan screen demonstration ghost
Technical field
The utility model relates generally to LED and shows field, relates in particular to the system that a kind of LED of elimination scan screen shows ghost.
Background technology
In demonstration field, be widely used LED scan screen at present, its basic implementation is to realize line scanning by controlling fast successively the break-make of a plurality of PMOS pipes, and reaches cost-saving object by the shared constant-current source channel of each row.
Fig. 1 shows a kind of traditional LED scan screen display system, and it mainly comprises power module 1, LED array 2, a plurality of constant-current drive circuit 3, a plurality of switching tube 4, decoding scheme 5 and master controller 6.Power module 1 provides DC input voitage VCC to come to LED array 2 and constant-current drive circuit 3 power supplies.LED array 2 is comprised of the capable N row of M LED, and wherein each LED comprises anode and negative electrode.The switching tube 4 of LED display adopts PMOS pipe conventionally, and it comprises source electrode, drain and gate.The source electrode of each switching tube 4 meets input voltage VCC, and drain electrode connects the anode of a line LED, thereby control inputs voltage VCC powers to a line LED.Each constant-current drive circuit 3 comprises the constant current source 302 of communication and control module 301 and several passages, the negative electrode that wherein constant current source 302 of each passage is connected to a row LED is to be used for providing a steady current to a row LED, opening and shutting off of constant current source 302 controlled by communication and control module 301, and the size of the steady current that constant current source 302 provides and opening time dutycycle determine the brightness of LED jointly.
Master controller 6 is responsible for providing coded signal CODE to decoding scheme 5, in order to select the current a line LED that wants demonstration.Decoding scheme 5 comprise coding input end with received encoded signal CODE and several decoding output terminals so that decoding output signal DECODE1~DECODEm to be provided respectively, each decoding output terminal is connected to the grid of a switching tube 4, in order to control the break-make between each row LED and input voltage VCC.Under the control of the coded signal CODE providing at master controller 6, it is effective that decoding scheme 5 only has an output signal at any time, this has just determined to only have at any time a switching tube 4 is conductings, to only have a line LED being connected with the switching tube 4 of this conducting be to be communicated with input voltage VCC and be that effectively all the other each row LED are invalid.Master controller 6 also by data signal line and control signal wire (comprising enable signal line, clock cable and latch signal line) and each constant-current drive circuit 3 communicate by letter and control module 301 communicates, to control the opening time dutycycle of each constant current source 302, thereby control the brightness of each LED in current effective a line LED.Between each constant-current drive circuit 3, pass through data signal line cascade, and be subject to the control signal line traffic control of master controller 6, to carry out data transmission and working state control.
In practice, because the area of switching tube 4 is generally larger, therefore there is larger stray capacitance.When certain switching tube 4 conducting, its drain voltage approaches input voltage VCC; Be expert at while switching, this switching tube 4 need to be turn-offed so that a line LED that this switching tube 4 connects is invalid, and next switching tube 4 is opened to show next line LED.Yet, existence due to the stray capacitance of switching tube 4, the drain voltage of the switching tube 4 being just turned off still remains on and approaches input voltage VCC, need to have a discharge path charge discharging resisting in stray capacitance could be fallen, thereby the drain voltage of switching tube 4 is fallen.If not waiting its drain voltage falls, the data that just will show by next line LED are opened each constant current source 302,, because the negative electrode of the LED of different rows is all received same group of constant current source, the drain electrode electric charge of the switching tube 4 being just turned off will be released to by the former a line LED that should be disabled being connected with it in constant current source of opening; If constant current source 302 negligible amounts of now opening, the electric charge of switching tube 4 drain electrodes that are turned off can concentrate the LED by minority to release, may make these originally be disabled and should not show the glimmer (being referred to as ghost here) that eyes can obviously be felt by bright LED, this ghost can affect picture display effect.
The refresh rate of LED display is higher, thereby row switching rate is also higher, in the unit interval, is subject to the impact of switching tube 4 spurious charges also can be larger, and ghost also can be more obvious.And along with the continuous lifting of LED display technique, more and more higher to the requirement of refresh rate, ghost how to eliminate dynamic demonstration has been very real and a can not be ignored problem easily and effectively.
The principle that shows ghost according to above generation, the key of known elimination ghost is to be expert at while switching, the spurious charge of switching tube 4 to be released, this area at present existing shadow scheme that disappears mostly utilizes discrete device to build discharge module.
Fig. 2 shows the system that a kind of existing elimination LED scan screen shows ghost.Compare with the LED scan screen display system of Fig. 1, the system of Fig. 2 increased a plurality of with NMOS pipe the discharge module 7 as switching tube.The drain electrode of the NMOS pipe in each discharge module 7 is connected to the anode drain electrode of respective switch pipe 4 (and be connected to) of a line LED as output terminal, the grid of this NMOS pipe is controlled by the shadow control line that disappears of master controller 6 as the shadow control end that disappears, and the source electrode of this NMOS pipe is earth terminal.When the shadow control end that disappears (being NMOS tube grid) of discharge module 7 receives the high level being sent by master controller 6 and disappears shadow control signal, this NMOS pipe conducting, produce an electric current of (the drain electrode of this NMOS pipe is to earth terminal) from output terminal to ground wire, thereby the spurious charge on switching tube 4 is discharged; When the shadow control end that disappears (being NMOS tube grid) of discharge module 7 receives the low level of being sent by master controller 6 and disappears shadow control signal, this NMOS pipe cut-off, from output terminal to ground wire, the electric current of (this NMOS pipe drain electrode is to earth terminal) is 0.
This system shown in Fig. 2 can be controlled the conducting of nmos switch pipe by the shadow control end that disappears and reach the regular hour, in the handoff procedure of being expert at, with the short period, the electric charge of power end PMOS switching tube 4 drain electrodes is released by the nmos switch pipe in discharge module 7.But find in actual applications, the method very easily causes overshoot, has both affected the shadow effect that disappears, and can cause again diode reverse voltage too high, affects reliability, and reduces the serviceable life of LED.For example, because needs increase new type of device (, discharge module 7), handling of goods and materials when LED display is produced makes troubles simultaneously.At present, mostly there is similar problem in the existing shadow scheme that disappears in LED display field.
The technical matters of the LED scan screen ghost existing for prior art, the utility model is intended to propose the system that a kind of effective elimination LED dynamically shows ghost.
Utility model content
The technical problems to be solved in the utility model is to eliminate LED scan screen ghost.The utility model proposes the system that a kind of LED of elimination dynamically shows ghost, utilize constant-current drive circuit to build discharge module, can eliminate fast in the short period of time ghost, improve the display effect of LED display, can not cause again overshoot effect LED reliability.
In one embodiment, provide a kind of LED of elimination scan screen to show the system of ghost, having comprised: power module, for input voltage is provided; LED array, wherein said LED array comprises the capable N row of M LED, wherein M and N are respectively positive integer; M switching tube, wherein each switching tube is connected between described power module and a line LED of described LED array, a described M switching tube in turn conducting to scan every a line LED of described LED array; The first constant-current drive circuit, it comprises N the constant current source of a row LED who is connected to respectively described LED array, each LED that described N constant current source in wherein said the first constant-current drive circuit is respectively in a line LED being just scanned provides steady current; And second constant-current drive circuit, it comprises M the constant current source of a line LED that is connected to respectively described LED array, described M constant current source in wherein said the second constant-current drive circuit is for discharging to eliminate demonstration ghost to the described switching tube turn-offing.
In one embodiment, this elimination LED scan screen shows that the system of ghost also comprises master controller, it is coupled to a described M switching tube via coded data line, and on described coded data line, send the capable switching of LED coded data control a described M switching tube in turn conducting to scan every a line LED of described LED array.
In one embodiment, this elimination LED scan screen shows that the system of ghost also comprises decoding scheme, the input end of described decoding scheme is coupled to described coded data line to receive the capable switching of described LED coded data, and described decoding scheme comprises that M output terminal is to be coupled respectively to a described M switching tube, thereby produce M decoding output to control respectively the turn-on and turn-off of a described M switching tube.
In one embodiment, described master controller is coupled to described the first constant-current drive circuit via data signal line and control signal wire, described master controller sends data-signal and on described control signal wire, sends the opening time dutycycle that control signal is controlled described N constant current source in described the first constant-current drive circuit on described data signal line, described master controller is also coupled to described the second constant-current drive circuit via the shadow control line that disappears, and on the described shadow control line that disappears, send described M the constant current source that the shadow control signal that disappears controls in described the second constant-current drive circuit corresponding switching tube is discharged.
In one embodiment, described the first constant-current drive circuit comprises that being coupled to first of described data signal line and described control signal wire communicates by letter and control module, and described the first communication and control module are controlled the opening time dutycycle of described N constant current source in described the first constant-current drive circuit according to described data-signal and described control signal.
In one embodiment, described the first constant-current drive circuit is the constant-current drive circuit of a plurality of cascades, the constant-current drive circuit of each cascade comprises described first communication and control module and is coupled to this first communicates by letter and several constant current sources of control module, each constant current source is connected to a row LED of described LED array, described in each, the opening time dutycycle of be connected several constant current sources is controlled in the first communication according to described data-signal and described control signal with control module, to be respectively the ordered series of numbers LED of described LED array, provides steady current.
In one embodiment, described the second constant-current drive circuit comprises second communication and the control module that is connected to a described M constant current source, shadow control line, described data signal line and described control signal wire disappear described in described second communication and control module are coupled to, for disappear described in basis shadow control signal, described data-signal and described control signal, control the unlatching of described M constant current source of described the second constant-current drive circuit, with the switching tube that is associated at a line LED, close to have no progeny this switching tube is discharged to eliminate demonstration ghost.
In another embodiment, described the second constant-current drive circuit comprises second communication and the control module that is connected to a described M constant current source, shadow control line, described power module and described control signal wire disappear described in described second communication and control module are coupled to, the unlatching of described M the constant current source that the input voltage providing for the shadow control signal that disappears described in basis, described power module and described control signal are controlled described the second constant-current drive circuit, to discharge to eliminate demonstration ghost to a described M switching tube simultaneously.
In one embodiment, the described control signal wire that is coupled to described second communication and control module can comprise clock cable and latch signal line, thereby the described control signal that is coupled to described second communication and control module is included in the clock signal of transmitting on described clock cable and the latch signal transmitting on described latch signal line.
In one embodiment, be coupled to described the first communication and the described control signal wire of control module and can comprise enable signal line, clock cable and latch signal line, thereby be coupled to described first, communicate by letter and latch signal that the described control signal of control module is included in the enable signal transmitting on described enable signal line, the clock signal of transmitting on described clock cable and transmits on described latch signal line.
In one embodiment, a described M switching tube is connected to respectively the anode of a line LED of described LED array, described N constant current source in described the first constant-current drive circuit is connected to respectively the negative electrode of a row LED of described LED array, and described M constant current source in described the second constant-current drive circuit is connected to respectively the anode of a line LED of described LED array.
In the utility model, this elimination LED scan screen shows that the system of ghost comprises that the switching tube that M constant current source is associated with each row LED to LED array discharges the spurious charge of releasing, thereby can eliminate efficiently demonstration ghost.
Accompanying drawing explanation
Below in conjunction with accompanying drawing, the utility model is described in further detail, wherein:
Fig. 1 shows a kind of structural drawing of traditional LED scan screen display system;
Fig. 2 shows the structural drawing that a kind of existing elimination LED scan screen shows the system of ghost;
Fig. 3 shows the structural drawing of the system of ghost according to the elimination LED scan screen of an embodiment of the utility model;
Fig. 4 shows the structural drawing of the system of ghost according to the elimination LED scan screen of another embodiment of the utility model.
Embodiment
Below in conjunction with accompanying drawing, some exemplary embodiment of the present utility model is described in detail, but protection domain of the present utility model is not limited to accompanying drawing and embodiment described below.
Fig. 3 shows the structural drawing of the system of ghost according to the elimination LED scan screen of an embodiment of the utility model.This system can comprise power module 1, LED array 2, a M switching tube 4, the first constant-current drive circuit 3-1 and the second constant-current drive circuit 3-2.In addition, this system also can comprise master controller 6 and decoding scheme 5.
Power module 1 can be direct supply, for providing input voltage VCC to come to LED array 2 and constant-current drive circuit 3 power supplies.LED array 2 can comprise the capable N row of M LED, and wherein M and N are respectively positive integer.Each LED comprises anode and negative electrode, the anodic bonding of a line LED of LED array 2 together, and LED array 2 one row LED negative electrode link together.By controlling gray scale and the brightness of each LED of this LED array 2, just can realize displaying contents and display effect.Each switching tube 4 in M switching tube 4 is connected between power module 1 and a line LED of LED array 2, this M switching tube 4 in turn conducting for example, with every a line LED of scanning (, open or conducting) LED array 2.Switching tube 4 can adopt PMOS pipe, and it comprises source electrode, drain and gate.At switching tube 4, adopt in the example of PMOS pipe, the source electrode of this M switching tube 4 is connected to power module 1, the drain electrode of each switching tube 4 is connected to the anode of a line LED in LED array 2, thereby by the turn-on and turn-off of this M switching tube 4, come control inputs voltage VCC to power to a line LED, realize the switching between each row LED in LED array 2.
In an embodiment as shown in Figure 3, this system comprises the constant-current drive circuit 3-1 of a plurality of cascades, and the constant-current drive circuit 3-1 of these a plurality of cascades can be collectively referred to as the first constant-current drive circuit 3-1.The constant-current drive circuit 3-1 of each cascade comprises the first communication and control module 301 and a plurality of constant current source 302, to be respectively the multiple row LED of LED array 2, provides steady current.The constant current of each cascade drives electric 3-1 altogether can comprise and is connected to respectively N the constant current source 302 that one of LED array 2 is listed as LED, with each LED being respectively in a line LED being just scanned, provides steady current.For example, each constant current source 302 is connected to respectively the negative electrode of a row LED of LED array 2.Each first communication and control module 301 are for controlling the opening time dutycycle of this N constant current source 302, and the size of the steady current that wherein constant current source 302 provides and opening time dutycycle determine the brightness of LED jointly.It will be appreciated by those skilled in the art that; the constant-current drive circuit 3-1 of these a plurality of cascades can integrally be embodied as single the first constant-current drive circuit 3-1; and utilize single the first communication and control module 301 to control this N constant current source 302, and do not depart from protection domain of the present utility model.
M the constant current source 304 that the second constant-current drive circuit 3-2 can comprise second communication and control module 303 and be connected to respectively a line LED of LED array 2.For example, this M constant current source 304 is connected to respectively the anode (being also connected to corresponding switching tube 4) of a line LED of LED array 2.Each constant current source 304, as the discharge module of every a line LED, for the switching tube 4 turn-offing is discharged to the spurious charge of releasing, shows ghost thereby eliminate.Second communication and control module 303 are controlled the opening time (that is, discharge time) of constant current source 304.
Master controller 6 on coded data line, send the capable switching of LED coded data CODE(its in order to select the current a line LED that shows of wanting) control M switching tube 4 conducting in turn, to scan every a line LED of LED array 2.In one embodiment, decoding scheme 5 can receive the capable switching of the LED coded data CODE that master controller 6 sends and produce M decoding output DECODE1~DECODEm, to control respectively the turn-on and turn-off of M switching tube 4.It is that effectively making to only have at most at any time a switching tube 4 is conductings that decoding scheme 5 only has at most decoding output DECODE1~DECODEm at any time, and other switching tubes 4 turn-off, and realizes the line scanning to LED array 2.
Master controller 6 also can send data-signal (gradation data) and on control signal wire, send control signal and control the opening time dutycycle of N constant current source 302 in the first constant-current drive circuit 3-1 and on the shadow control line that disappears, send 304 pairs of corresponding switching tubes 4 of M constant current source that the shadow control signal that disappears controls in the second constant-current drive circuit 3-2 and discharge on data signal line.In one embodiment, control signal comprises enable signal En, clock signal C lk and latch signal Lat.
In the cascade structure that comprises a plurality of the first constant-current drive circuit 3-1 as shown in Figure 3, each first communication and control module 301 and second communication and control module 303 all comprise enable signal input end En, clock signal input terminal Clk, latch signal input end Lat, data input pin Din and data output end Dout.Each first communication is connected with enable signal line, clock cable, the latch signal line of master controller 6 respectively with enable signal input end En, clock signal input terminal Clk, the latch signal input end Lat of control module 301, enable signal En, the clock signal C lk and the latch signal Lat that to receive respectively master controller 6, send, thereby the ON time dutycycle of each LED in a line LED that control is scanned respectively.Bits of data signal for each LED in a line LED in the data-signal sending due to master controller 6 may be different, therefore each first communication and control module 301 can correspondingly be controlled the ON time dutycycle of the LED being associated, and each LED in a line LED that makes to be scanned has different gray scales and brightness.
The clock signal input terminal Clk of the second communication of the second constant-current drive circuit 3-2 and control module 303, latch signal input end Lat can be connected with clock cable, the latch signal line of master controller 6 respectively, the clock signal C lk and the latch signal Lat that to receive respectively master controller 6, send, and the enable signal input end En of second communication and control module 303 can be connected with the shadow control line that disappears of master controller 6, the switching tube 4 being associated is discharged under the control in the shadow control signal that disappears.
Between each first constant-current drive circuit 3-1 and with the second constant-current drive circuit 3-2 between by data signal line cascade: the first communication of first first constant-current drive circuit 3-1 is connected with the data signal line of master controller 6 with the data input pin Din of control module 301, receive the data-signal that master controller 6 sends, and this data-signal is passed to the data input pin Din of the coupled next one first communication and control module 301 by data output end Dout, this data-signal is passed to next the first communication and control module 301 successively, until transfer to the second communication of the second constant-current drive circuit 3-2 and the data input pin Din of control module 303.The data-signal that master controller 6 sends has comprised gradation data and the indication to the constant current source 304 that will discharge that each LED of aligning in a line LED being scanned will be used.In another embodiment, the data signal line of each the first constant-current drive circuit 3-1 and the second constant-current drive circuit 3-2 can not be cascade realize, but make the data input pin Din of the first communication and control module 301, second communication and control module 303 be connected to respectively the data signal line of master controller.
Master controller 6 sends to each first constant-current drive circuit 3-1 of driving LED array 2 using the gradation data of needs demonstration as data-signal, in conjunction with control signal (comprising enable signal, clock signal, latch signal), just can control by the first communication and control module 301 the opening time dutycycle of each constant current source 302, thereby control the brightness of each LED in LED array 2, in conjunction with scanning, switch and realize image demonstration.In one embodiment, master controller 6 is set to the corresponding bits of data signal of the constant current source 304 with needs electric discharges valid data, is set to invalid data with the corresponding bits of data signal of constant current source 304 without electric discharge, and this setting is embedded in to second communication and the control module 303 that passes to the second constant-current drive circuit 3-2 in data-signal by data signal line.In scanning procedure for displaying, when carrying out scan line switching, master controller 6 is set to by the shadow control signal that disappears second communication and the control module 303 that Efficient Concurrency is delivered to the second constant-current drive circuit 3-2, the data-signal receiving in conjunction with second communication and control module 303, make to need the constant current source 304 of electric discharge to be opened, produce one from switching tube 4 through constant current source 304 electric current to ground wire, spurious charge from switching tube 4 through constant current source 304 ground of releasing; At constant current source 304, open and hold time after T, the master controller 6 shadow control signal that will disappear is set to invalidly, and the constant current source 304 of the second constant-current drive circuit 3-2 turn-offs.In the utility model, the spurious charge of utilizing constant current source 304 to release on the switching tube 4 turn-offing can be eliminated demonstration ghost effectively, and discharge time is fast, can not cause overshoot, thereby can not affect reliability and the life-span of LED.
Above-described embodiment can be controlled one by one to the constant current source 304 being connected in series with every a line LED, thereby the switching tube 4 that at every turn can only be associated to a line LED discharges.In other embodiments, can carry out simple change to above-described embodiment.Fig. 4 shows the structural drawing of the system of ghost according to the elimination LED scan screen of another embodiment of the utility model.
With the embodiment comparison shown in Fig. 3, the difference of system shown in Figure 4 is mainly to be connected with input voltage VCC as the data input pin Din of the second constant-current drive circuit 3-2 of discharge module, in the second constant-current drive circuit 3-2, all constant current sources 304 all can be transfused to valid data, when the shadow control signal that disappears is effective, all constant current sources 304 all can conducting, thereby all switching tubes 4 is discharged simultaneously; When the shadow control signal that disappears is invalid, all above-mentioned constant current sources 304 are turned off simultaneously.System shown in Fig. 4 is more simple in circuit structure and control, and can play equally the effect of eliminating ghost.
As mentioned above, the utility model provides a kind of LED of elimination dynamically to show the system of ghost, both improved the display effect of LED display, can not cause again overshoot effect LED reliability, owing to using the second constant-current drive circuit 3-2(, it can be identical with the first constant-current drive circuit 3-1 simultaneously) as discharge module, without for the shadow function that disappears increases new type of device, make troubles can to the management of LED display production material.
The above is described the utility model in conjunction with most preferred embodiment, but the utility model is not limited to the embodiment of above announcement.Any those skilled in the art, in the disclosed technical scope of the utility model, all can carry out suitable change or variation to it, and this change or change and all should be encompassed in protection domain of the present utility model within.