CN101951712B - LED display, LED drive circuit and output circuit of LED drive circuit - Google Patents
LED display, LED drive circuit and output circuit of LED drive circuit Download PDFInfo
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Abstract
The invention discloses an LED drive circuit and an output circuit therein. The LED drive circuit comprises a control module, a register block, a plurality of output driving modules and corresponding output circuits, wherein the control module determines whether a current mode is a first working mode or a second working mode; the register block receives control data input by a data input end; and each output driving module drives a corresponding output circuit. When the current mode is the second working mode, the control data comprises adjustment-mode data, current data and channel address data; when the adjustment-mode data is single-path adjustment, the corresponding output driving module is enabled according to the channel address data; and the enabled output driving module independently adjusts the output current of the corresponding output circuit according to the current data. Thus, the output current difference value existing between channels can be greatly reduced and even eliminated, and meanwhile, inconsistency in brightness and chrominance caused by the inconsistency in optical characteristic of the LED can also be reduced or eliminated.
Description
Technical field
The present invention relates to the LED application, especially relate to a kind of light-emitting diode display, led drive circuit and output circuit thereof.
Background technology
LED(Light Emitting Diode, light-emitting diode) because the life-span is long, response speed is fast, volume is little, power consumption is little, the reliability high has been widely used in the fields such as backlight, illumination, electronic equipment, display screen and automobile.Drive circuit is the important component part of LED product, and the performance of drive circuit will directly have influence on the performances such as life-span, power consumption and reliability of LED product.Usually, because LED is the semiconductor device of characteristic sensitivity, have again negative temperature characteristic, therefore when LED is used as display floater, lighting apparatus or backlight, need to adopt constant current to drive to LED.
LED product (such as light-emitting diode display etc.) all comprises the led array that is comprised of some LED and usually for some drive circuits of driving LED array, wherein each drive circuit includes a plurality of passages (such as 4,8 or 16), and each passage of described drive circuit can provide constant drive current for one or more LED.Be the brightness of each LED and consistency or the uniformity of colourity in the assurance led array, each passage of each drive circuit need to provide accurately consistent constant output current.At present, the interchannel of the drive circuit of main flow (bit-to-bit) electric current difference generally all in ± 3%, and between sheet (chip-to-chip) electric current difference generally all in ± 6%.Precision for the constant output current that guarantees led drive circuit, not only need to carry out meticulous design and layout at design link, also need higher manufacturing process to reduce as much as possible fabrication error, this will increase substantially production and the design cost of led drive circuit.
The fiducial value of one reference current as output current generally need to be provided in led drive circuit inside, and therefore described reference current will directly affect the precision of output current.The precision of described reference current depends on an outer meeting resistance of described led drive circuit.For the consistency of the output current that guarantees the different LED drive circuit, need to be with the resistance difference control of the outer meeting resistance of each led drive circuit within the specific limits.Like this, improve the requirement to outer meeting resistance, also increased the cost of outer meeting resistance.
In addition, the consistency of the brightness of each LED and colourity or uniformity are not only relevant with the consistency of the output current of led drive circuit in the led array, and be also relevant with the consistency of the optical characteristics (such as luminous flux) of each LED.By way of example, if the output current of each passage of each drive circuit strict conformance all also and certain consistent with colourity once the brightness that guarantees surely each LED, also needs to consider at this moment the consistency of the optical characteristics (such as luminous flux) of each LED.For satisfy more and more higher application demand, just need to adopt higher, stricter production technology can produce the LED that satisfies the demand.Like this, to the conforming strict demand of LED cause the rate of finished products of LED low, cost is high.And the cost proportion of the cost of LED in the LED product occupies very large ratio, and it is high that the cost increase of LED certainly will be arrived the cost that causes some LED products.
Therefore, be necessary to propose a kind of improved technical scheme and overcome the problems referred to above.
Summary of the invention
One of the technical problem to be solved in the present invention is to provide a kind of led drive circuit, and it can provide accurately adjustable output current.
Two of the technical problem to be solved in the present invention is to provide a kind of output circuit, and it can utilize simple structure that accurately adjustable output current is provided.
Three of the technical problem to be solved in the present invention is to provide a kind of light-emitting diode display, and its led drive circuit can provide accurately adjustable output current.
In order to address the above problem, according to an aspect of the present invention, the invention provides a kind of output circuit, it comprises: the reference current determining unit with control end and offset side, its control signal according to control end is selected one between the first reference current and the second reference current, and produce a bias voltage according to selected reference current and exported by described offset side, wherein the first reference current is less than the second reference current; Some current drives pipes, its source electrode is connected to each other, its drain electrode is connected to each other, and the grid of each current drives pipe links to each other with described offset side by a switching circuit, controls the turn-on and turn-off of corresponding current driving tube by the turn-on and turn-off of controlling each switching circuit; And efferent duct, its source electrode links to each other with the drain electrode of described current drives pipe, and its drain electrode is as the output of output circuit, and its grid is controlled the turn-on and turn-off of described efferent duct.
Further, the current ratio of the first reference current and the second reference current is 1:M, wherein 1.5≤M≤4.5.
Further, bias voltage on the described offset side drives each current drives pipe makes it produce output current, and drives the current ratio that ratio that each current drives pipe output current that produces and the bias voltage that produces according to the second reference current drive the output current that the corresponding current driving tube produces equals the first reference current and the second reference current according to the bias voltage that the first reference current produces.
Further, the ratio of the breadth length ratio of each current drives pipe is respectively: 2
0: 2
1: ...: 2
Y-3: 2
Y-2: X, wherein X satisfies: 2
0+ 2
1+ ... + 2
Y-3+ 2
Y-2Less than M*X and 2
0+ 2
1+ ... + 2
Y-3+ 2
Y-2And the every rank electric current adjusting range the when difference between the M*X is less than or equal to the second reference current, the number of the described current drives pipe of Y.
Further, be that the control signal of the control signal of the switching circuit that connects of the current drives pipe of X and reference current determining unit is according to determining with 1 digit current data with relative breadth length ratio.According to Y digit current data described output circuit is carried out the output current adjustment, wherein determine that according to 1 in the Y digit current data with relative breadth length ratio be the control signal of switching circuit of current drives pipe connection of X and the control signal of reference current determining unit, control the turn-on and turn-off of other each switching circuit according to all the other Y bit data.
According to an aspect of the present invention, the invention provides a kind of led drive circuit, it comprises: control module, determine that current is the first mode of operation or the second mode of operation; The register group, the control data of receive data input input; Some output driver modules and corresponding output circuit, each output driver module drives corresponding output circuit, and each output circuit provides output current by the output of correspondence.When the first mode of operation, each output driver module starts or stops corresponding output circuit according to the corresponding data in the control data in the register group, when the second mode of operation, described control data include the adjustment modes data, current data and channel address data, when the adjustment modes data are adjusted for unification, each output driver module is according to the unified output current of adjusting each output circuit of described current data, when the adjustment modes data are the single channel adjustment, the output driver module corresponding according to described channel address data enable, the output driver module that this enables are adjusted separately the output current of corresponding output circuit according to described current data.
Further, described control data are the N position, and described output driver module and output circuit also are N, and wherein N is natural number.
Further, described led drive circuit also comprises the reference current module, and described reference current module provides the first reference current and the second reference current, and wherein the first reference current is less than the second reference current.Each output circuit comprises: the reference current determining unit with control end and offset side, its control signal according to control end is selected one between the first reference current and the second reference current, and produce a bias voltage according to selected reference current and exported by described offset side, wherein the first reference current is less than the second reference current; Some current drives pipes, its source electrode is connected to each other, its drain electrode is connected to each other, and the grid of each current drives pipe links to each other with described offset side by a switching circuit, controls the turn-on and turn-off of corresponding current driving tube by the turn-on and turn-off of controlling each switching circuit; And efferent duct, its source electrode links to each other with the drain electrode of described current drives pipe, and its drain electrode is as the output of output circuit, and its grid is controlled the turn-on and turn-off of described efferent duct.Each output driver module starts or stops corresponding output circuit according to the corresponding data in the control data in the register group and is: each output driving circuit is controlled the turn-on and turn-off of the efferent duct of corresponding output circuit according to correspondence 1 bit data in the control of the N position in register group data; Each output driver module according to the unified output current of adjusting each output circuit of described current data is: each output driver module sends control signal according to the control end of 1 determining unit of the reference current to correspondence in described current data and with an on-off circuit of corresponding output circuit, described reference current determining unit is selected one according to described control signal between the first reference current and the second reference current, each output driver module is according to the turn-on and turn-off of the rest switch circuit in the corresponding output circuit of all the other controls in described current data; The output current that the output driver module that this enables is adjusted separately corresponding output circuit according to described current data is: the output driver module that this enables sends control signal according to the control end of 1 determining unit of the reference current to correspondence in described current data and with an on-off circuit of corresponding output circuit, described reference current determining unit is selected one according to described control signal between the first reference current and the second reference current, the output driver module that this enables is according to the turn-on and turn-off of the rest switch circuit in the output circuit of all the other the control correspondences in described current data.
Further, each output driver module is stored described current data before the output current of adjusting output circuit according to described current data.
Further, the register group includes N bit shift register, N position output register and N order of the bit register, the serial data of described shift register receive data input input, after latch enable signal comes into force, N bit data in the latch shift register, and when being the first mode of operation, export described N bit data to described output register current, when being the second mode of operation, export described N bit data to described command register current.
Compared with prior art, the led drive circuit among the present invention can provide the single channel of the output current of each current output channels to adjust function and/or the unified function of adjusting.Utilize the unified function of adjusting that the output current of each current output channels is unified to adjust, can greatly reduce even eliminate the output current difference that exists between drive circuit chip, utilizing single channel to adjust function adjusts separately the output current of each current output channels, the output current difference that each interchannel exists can be greatly reduced even eliminate, brightness that the inconsistency of the optical characteristics (such as luminous flux) owing to LED causes and the inconsistency of colourity can also be reduced or eliminate simultaneously.Output circuit among the present invention produces output current based on two kinds of reference currents that vary in size, and has expanded like this adjusting range of output current, and has more met human eye brightness law of perception.
About other purposes of the present invention, feature and advantage are described in detail in embodiment below in conjunction with accompanying drawing.
[description of drawings]
In conjunction with reaching with reference to the accompanying drawings ensuing detailed description, the present invention will be more readily understood, structure member corresponding to same Reference numeral wherein, wherein:
Fig. 1 is the led drive circuit structural representation block diagram in one embodiment among the present invention;
Fig. 2 is each signal sequence in one embodiment the schematic diagram of led drive circuit when the first mode of operation among the present invention;
Fig. 3 is each signal sequence in one embodiment the schematic diagram of led drive circuit when the second mode of operation among the present invention;
Fig. 4 is the command format exemplary plot in one embodiment that 16 digit currents among the present invention are adjusted data;
Fig. 5 is the output module circuit diagram in one embodiment among the present invention; With
Fig. 6 is 7 digit current data of the output module among Fig. 5 and the curve synoptic diagram of current gain.
[embodiment]
For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the present invention is further detailed explanation below in conjunction with the drawings and specific embodiments.
Detailed description of the present invention mainly presents by program, step, logical block, process or other symbolistic descriptions, the running of the technical scheme among its direct or indirect simulation the present invention.Affiliated those of skill in the art use herein these descriptions and statement essential to the work that the others skilled in the art in the affiliated field effectively introduce them.
Alleged " embodiment " or " embodiment " refer to that special characteristic, structure or the characteristic relevant with described embodiment can be contained at least one implementation of the present invention at least herein.Different local in this manual " in one embodiment " that occur also nonessentially all refer to same embodiment, must not be yet with other embodiment mutually exclusive separately or select embodiment.In addition, represent the sequence of modules in method, flow chart or the functional block diagram of one or more embodiment and revocablely refer to any particular order, also be not construed as limiting the invention.
See also shown in Figure 1, it is the led drive circuit 100 structural representation block diagram in one embodiment among the present invention, and described led drive circuit 100 comprises that control module 110, several output driver modules 120, several output modules 130(also can be called output circuit), reference current module 140 and register group 150.
Described control module 110 can receive the latch enable signal (latch enable signal) of input LE input and the output enable control signal (output enable control signal) of input OE input.Described led drive circuit 100 has two kinds of mode of operations, is respectively the first mode of operation and the second mode of operation, and wherein the first mode of operation also can be called the current drives pattern, and the second mode of operation also can be called the electric current adjustment modes.Described control module 110 can enter the first mode of operation or enter the second mode of operation according to latch enable signal LE judgement is current.
In one embodiment, described register group 150 includes shift register 151, output register 152 and command register 153.Shift register 151, output register 152 and command register 153 can be the N bit register, and wherein N can be 4,8,16,32 or other natural number.Described shift register 151 can receive according to the clock signal of input CLK input the serial data of input SDI input, after described latch enable signal LE comes into force, latch the N bit data in it, and current when being the first mode of operation, export described N bit data to described output register 152 as the output enable data,, export described N bit data to described command register 153 and adjust data as electric current when being the second mode of operation current.In other embodiments, also output register 152 and command register 153 can be carried out multiplexingly, perhaps shift register 151, output register 152 and command register 153 be carried out multiplexingly, certainly other distressed structure can also be arranged.
Described reference current module 140 links to each other with an outer meeting resistance via input REXT, it can provide accurate reference current for output module 130, the size of described reference current is determined by described outer meeting resistance, it can provide size two kinds of reference currents simultaneously, their current ratio is 1:M, and 1.5≤M≤4.5 wherein are such as M=2,3,4,1.5 or 2.5 etc., little reference current also can be called as the first reference current, and large reference current also can be called as the second reference current.
In one embodiment, described output driver module 120 includes N, be respectively first output driver module 121, second output driver module 122 ... with N output driver module 123, described output module 130 also comprises N, be respectively the first output module 131, the second output module 132 ... with N output module 133, wherein each output driver module is used for driving a corresponding output module, and corresponding output driver module and output module form a current output channels.Therefore, also described led drive circuit 100 includes N current output channels.
Each output module provides accurate output current by the output OUT of correspondence, and wherein said output current is based on described reference current and produces.When described led drive circuit 100 was used for driving LED, each output OUT can connect one or more LED.Like this, each current output channels can provide accurate output current to the LED that connects.When the first mode of operation, each output driver module starts (enabling) or stops output module corresponding to (disable) according to 1 bit data of output register 152 interior correspondences, wherein when starting an output module, this output module can provide output current to its output, when stopping this output module, this output module then stops to provide output current to its output.At this moment, the N bit data in the output register 152 is used as respectively the output enable signal of N corresponding output channel.When the second mode of operation, each output driver module can be adjusted the output current value that data are adjusted output module according to the electric current in the command register 153.
Fig. 2 is each signal sequence in one embodiment the schematic diagram of led drive circuit 100 when the first mode of operation among the present invention, wherein N=16 in this example.See also shown in Figure 2, when 100 operation of described led drive circuit, in the data of the rising edge sampling input SDI of clock signal clk input, each clock sampling 1 bit data, 16 clock sampling 16 bit data are to shift register 151.Afterwards, described latch enable signal LE is high level by low transition first, through after about clock cycle, be low level by the high level saltus step again, this moment, described latch enable signal LE came into force, 16 bit data in the latch shift register 151, described control circuit 110 is judged current first mode of operation that is according to the lasting time (such as less than 2 cycles) of the high level of described latch enable signal LE simultaneously, and exports described N bit data to described output register 152 as the output enable data.After this, when the output enable control signal of input OE input was effective, each output driver module started or stoped corresponding output module according to 1 bit data of output register 152 interior correspondences, such as can start with 1 representative, 0 representative stop.In other embodiments, the time that described control circuit 110 also can continue according to the low level of described latch enable signal LE goes to judge to be the first mode of operation or the second mode of operation, can certainly judge it is the first mode of operation or the second mode of operation according to other signals rather than latch enable signal.
When described led drive circuit 100 is applied to driving LED, each output OUT can connect one or more LED, and when an output module started, the LED that connects this output module opened (bright), when this output module stopped, the LED that connects this output module closed (going out).Under the first mode of operation, constantly input 16 output enable data to output register 152 by input SDI and shift register 151 with preset frequency, thereby can control the ceaselessly light on and off of LED that each current output channels connects.Because the light on and off switching frequency of LED is higher than the perception of human eye, so the light on and off that human eye can not perceive LED switch, and only can perceive the variation of the brightness of LED.At this moment, just can regulate the brightness of LED by the duty ratio of control LED.
Fig. 3 is each signal sequence in one embodiment the schematic diagram of led drive circuit 100 when the second mode of operation among the present invention, wherein N=16 in this example.See also shown in Figure 3, when described led drive circuit 100 operation, data in the rising edge sampling input SDI of clock signal clk input, each clock sampling 1 bit data, 16 clock sampling 16 bit data are to shift register 151, simultaneously described latch enable signal LE is high level by low transition first, through after about 4 clock cycle, be low level by the high level saltus step again, this moment, described latch enable signal LE came into force, 16 bit data in the latch shift register 151, described control circuit 110 is judged current second mode of operation that is according to the lasting time (such as greater than 2 cycles) of the high level of described latch enable signal LE simultaneously, and exports described 16 bit data to described command register 153 as electric current adjustment data.
Fig. 4 is the command format exemplary plot in one embodiment that 16 digit currents among the present invention are adjusted data.See also shown in Figure 4ly, D, E, F three bit data are checking data, and C is default position, and DA0-DA6 seven bit data are current data, can realize 2 of output current
7=128 contrasts are whole, 7,8,9 and the A four figures according to being channel address, can support 2
4=16 current output channels.B is that the electric current adjustment modes is selected the position, if B is 0, it then is the single channel adjustment modes, this moment control module 110 according to channel address 7,8,9 and A enable the output driver module of its corresponding current output channels, this output driver module can storaging current data DA0-DA6 and is adjusted separately accordingly the output current of corresponding output module.If B is 1, then be unified adjustment modes, this moment, control module 110 enabled the output driver module of all current output channels, each output driver module storaging current data DA0-DA6 and the unified output current of adjusting the output module of each passage accordingly, channel address 7,8,9 and A invalid.Like this, under the second mode of operation, just can utilize single channel to adjust function the output current of each current output channels is adjusted separately, utilize the unified function of adjusting that the output current of each current output channels is unified to adjust.
An advantage of the present invention or characteristics are: described led drive circuit 100 can provide the single channel of the output current of each current output channels to adjust function and/or the unified function of adjusting.Utilize the unified function of adjusting that the output current of each current output channels is unified to adjust, can greatly reduce the output current difference that exists between drive circuit chip, can increase substantially like this brightness of LED of the LED product (such as light-emitting diode display) that has adopted the led drive circuit among the present invention and consistency or the uniformity of colourity, simultaneously also can reduce or eliminate the output current difference between the drive circuit chip that the inconsistency owing to outer meeting resistance causes, thereby can reduce the conforming requirement to outer meeting resistance.Utilizing single channel to adjust function adjusts separately the output current of each current output channels, can greatly reduce even eliminate the output current difference that each interchannel exists, can further improve like this brightness of LED of the LED product (such as light-emitting diode display) that has adopted the led drive circuit among the present invention and consistency or the uniformity of colourity, simultaneously can also reduce or eliminate brightness that the inconsistency of the optical characteristics (such as luminous flux) owing to LED causes and the inconsistency of colourity, thereby can reduce the consistency requirement of the optical characteristics (such as luminous flux) to LED, and then reduce the cost of LED.
In one embodiment, if 1 LED of each channels drive, the inconsistency of the optical characteristics (such as luminous flux) of 16 LED that led drive circuit 100 drives is higher, that is to say, these 16 LED use same output current to drive, and their brightness and colourity also difference are larger.In the debug process to the LED product, led drive circuit 100 can be switched to the second mode of operation, eliminate the inconsistency of the optical characteristics of 16 LED by the output current of independent each current output channels of fine setting, last so that the brightness of these 16 LED and colourity keep higher consistency, however the output current of each current output channels may have larger difference at this moment.Because the single channel of led drive circuit is adjusted function, thereby can greatly reduce the coherence request of the optical characteristics (such as luminous flux) to LED, and the highest part of cost is exactly LED in LED product, like this so that adopt the LED product of the led drive circuit among the present invention to make the cost decrease when guaranteeing application quality.
Usually, for the brightness of the LED that guarantees to drive and the consistency of colourity, need the difference value of output current of each current output channels of led drive circuit the smaller the better.Yet, single channel in the led drive circuit among the present invention is adjusted function, then broken this thinking set traditionally, the target that its single channel is adjusted function can not be with the output current of each current output channels adjust more consistent, and can be the brightness of LED that each current output channels is driven and colourity adjust more consistent, this adjustment may be with the larger inconsistency with the optical characteristics that remedies LED of the difference value adjustment of the output current of each current output channels.
In other embodiments, N also can be 4,8,32 or other numeral, current data under same the second mode of operation also can change 5,6,8,9 or other digit order number into by 7, single channel also can only be set under the second mode of operation adjust function or the unified function of adjusting, can also change arbitrarily the figure place of checking data.
Fig. 5 is that the output module 500(among the present invention also can be referred to as output circuit) in one embodiment circuit diagram, the current data of still adjusting in the data take electric current in this embodiment is introduced as 7 as example, and described output module 500 can be as the output module in each current output channels of led drive circuit.Described output module 500 includes current drives pipe M1-M7, efferent duct M8 and reference current determining unit 510.
Described reference current determining unit 510 has control end and offset side, and its control signal according to control end is selected in the first reference current and the second reference current, and produces a bias voltage according to selected reference current and exported by described offset side.The control signal of described control end can be for 1 in the 7 digit current data, such as highest order.When concrete the application, highest order is 1, then shows selected the second reference current, and described bias voltage produces according to the second reference current, and highest order is 0, then shows selected the first reference current, and described bias voltage produces according to the first reference current.
The source electrode of each among the current drives pipe M1-M7 is connected to each other and ground connection, and drain electrode all is connected to each other, and grid all links to each other with described offset side by a switching circuit.Bias voltage on the described offset side drives each current drives pipe M1-M7 makes it produce output current, and drive the current ratio that ratio that each current drives pipe M1-M7 output current that produces and the bias voltage that produces according to the second reference current drive the output current that corresponding current driving tube M1-M7 produces equals the first reference current and the second reference current according to the bias voltage that the first reference current produces, be 1:M.
The ratio of the breadth length ratio of current drives pipe M1-M7 is respectively 1:2:4:8:16:32:X, and the current ratio of current flowing driving tube M1-M7 is respectively 1:2:4:8:16:32:X equally like this.The control end of the switching circuit that current drives pipe M1-M6 is corresponding links to each other with the output driver module, described output driver module is according to the turn-on and turn-off of other 6 these switching circuits of control in the 7 digit current data, thereby control the turn-on and turn-off of each current drives pipe M1-M6, and then realization is whole to 64 contrasts of the output current of output module 500.The control end of the switching circuit that current drives pipe M7 is corresponding links to each other with the output driver module, and described output driver module is controlled the turn-on and turn-off of this switching circuit according to that 1 bit data that is used for definite reference current in the 7 digit current data.Like this, can realize 128 contrasts of the output current of output module 500 whole according to 7 digit current data.The output current of current drives pipe M1 is every rank electric current adjusting ranges.
For fear of the large jump of appearance between the maximum output current of the minimum output current of the output module 500 when the large reference current output module 500 during with little reference current, the relative breadth length ratio X of current drives pipe M7 needs well-designed, as a general design consideration can allow X satisfy 1+2+4+8+16+32 less than M*X and 1+2+4+8+16+32 near M*X.For instance, if M=2, X can be 32 so, if M=3, X can be 22 so, if M=4, X can be 16 so.Every rank electric current adjusting range when in one embodiment, 1+2+4+8+16+32 refers to that near M*X between the two difference is less than or equal to large reference current.
When led drive circuit is the second mode of operation, the output driver module in can memory command register 153 7 digit current data and control accordingly the conducting of current drives pipe M1-M7 of output module 500 or the selection of shutoff and reference current.Can store in advance 7 digit current data of acquiescence in each output driver module, such as being 1010010, in output current adjustment process subsequently, can it be covered with 7 up-to-date digit current data.The below enumerates some examples of adjusting output current according to current data, if 7 digit current data are 0111000, because highest order is 0, then select the first reference current, controlling simultaneously current drives pipe M7 turn-offs, rear 6 decimal number is 56, then can be with current drives pipe M4-M6 conducting, if 7 digit current data are 0111100, because highest order is 0, then select the first reference current, control simultaneously current drives pipe M7 and turn-off, rear 6 decimal number is 60, then can be with current drives pipe M3-M6 conducting, if 7 digit current data are 1010110, because highest order is 1, then selected the second reference current is controlled current drives pipe M7 conducting simultaneously, rear 6 decimal number is 22, then can be with current drives pipe M2, M3 and M5 conducting.When specific implementation, can be with the switching circuit of each the respectively corresponding current drives pipe in 7 bit data, last corresponding current driving tube M1 wherein, penultimate corresponding current driving tube M2, by that analogy, the 6th corresponding current driving tube M6, highest order is used for controlling simultaneously current drives pipe M7 and reference current determining unit 510.
The drain electrode of described efferent duct M8 links to each other with output OUT, and source electrode links to each other with the drain electrode of current drives pipe M1-M7.The grid of described efferent duct M8 links to each other with the output driver module as the switch control end of described efferent duct M8.When the first mode of operation, the output driver module can be controlled according to 1 of the correspondence of the output enable data in the output register 152 conducting or the shutoff of efferent duct M8, thereby control the starting or stoping of output module 500 exported driver module this moment according to the conducting of having stored the current drives pipe M1-M7 that in the inner current data controls output module 500 or the selection of shutoff and reference current.
Fig. 6 is 7 digit current data of the output module 500 among Fig. 5 and the curve synoptic diagram of current gain, and wherein said current gain is actual output current value and the ratio of giving tacit consent to output current value, and this moment, described acquiescence output current value was 1010010, M=2.Usually, the default value of the output module of each current output channels of each led drive circuit is consistent, when Using Defaults the consistency of the brightness that can not guarantee external LED and colourity, the output current that can enter under the second mode of operation the output module of each current output channels of each led drive circuit carries out separately or unified fine setting.Curve among the figure is formed by two different straight line L1 and L2 linkings of slope, adopt little reference current to carry out the electric current adjustment in the process of straight line L1 always, every rank electric current adjusting range is less, adopt large reference current to carry out the electric current adjustment in the process of straight line L2 always, every rank electric current adjusting range is larger, and the M of every rank electric current adjusting range doubly during for L1.Such design also is to consider following several aspect: 1, when same exponent number is adjusted, can obtain wider adjusting range; 2, at output current hour, because human eye is more responsive to the variation of the optical characteristics (such as luminous flux) of LED, therefore adopt adjustment more by a small margin, when electric current is larger, because human eye to the variation relative insensitivity of the optical characteristics (such as luminous flux) of LED, therefore adopts adjustment by a relatively large margin.
In one embodiment, described current drives pipe M1-M7 and efferent duct M8 are nmos pass transistor.Described efferent duct M8 is high-voltage tube.
In other embodiments, the figure place that electric current is adjusted the current data in the data can also be 6,8 or other figure place, and they all will be as current drives pipe control bit, and wherein 1 (such as highest order) selects the position with the double reference current of doing.For instance, figure place in current data is 6 o'clock, need to be with the current drives pipe M6 deletion of the output module among Fig. 5,6 bit data are controlled respectively current drives pipe M1-M5 and M7, control the double reference current of doing of highest order of current drives pipe M7 and selecting the position, also need to reset the relative breadth length ratio X of current drives pipe M7 this moment, makes it satisfy 1+2+4+8+16 and get final product near M*X less than M*X and 1+2+4+8+16, and can realize 2 of output current this moment
6Contrast is whole.Again for instance, figure place in current data is 8 o'clock, need to increase by a current drives pipe M9 in the output module in Fig. 5, the drain electrode of current drives pipe M9 links to each other with the drain electrode of current drives pipe M1-M7, source electrode links to each other with the source electrode of current drives pipe M1-M7, grid links to each other with described offset side by switching circuit, current drives pipe M9 is 64:1 with the ratio of the breadth length ratio of current drives pipe M1,8 bit data are controlled respectively current drives pipe M1-M7 and M9, control the double reference current of doing of highest order of current drives pipe M7 and selecting the position, equally also need to reset the relative breadth length ratio X of current drives pipe M7 this moment, and it satisfies 1+2+4+8+16+32+64 and gets final product near M*X less than M*X and 1+2+4+8+16+32+64.
In general, the ratio of the breadth length ratio of current drives pipe M1-M7 satisfies: 2
0: 2
1: 2
2: 2
3: 2
4: 2
5: X.If the number of current drives pipe is Y, the ratio of the breadth length ratio of these current drives pipes is respectively: 2
0: 2
1: ...: 2
Y-3: 2
Y-2: X, wherein X satisfies: 2
0+ 2
1+ ... + 2
Y-3+ 2
Y-2Less than M*X and 2
0+ 2
1+ ... + 2
Y-3+ 2
Y-2And the every rank electric current adjusting range the when difference between the M*X is less than or equal to the second reference current.
Another characteristics of the present invention or advantage are: for output module provides two kinds of reference currents that vary in size, and when the minimum output current of output module is greater than little reference current during large reference current output module maximum output current and every rank electric current adjusting range of output module when the difference between the maximum output current of output module is less than or equal to large reference current when the minimum output current of output module and little reference current during large reference current, expand like this adjusting range of output current, and more met human eye brightness law of perception.
Another characteristics of the present invention or advantage are: the ratio of the breadth length ratio of Y current drives pipe is respectively: 2
0: 2
1: ...: 2
Y-3: 2
Y-2: X, wherein X satisfies: 2
0+ 2
1+ ... + 2
Y-3+ 2
Y-2Less than M*X and 2
0+ 2
1+ ... + 2
Y-3+ 2
Y-2And the every rank electric current adjusting range the when difference between the M*X is less than or equal to the second reference current, thereby utilize minimum driving tube to realize 2 of output current
YContrast is whole, and front 2
Y-1The electric current adjusting range on rank is substantially uniform, rear 2
Y-1The electric current adjusting range on rank is substantially uniform, and front 2
Y-1The electric current adjusting range on rank and rear 2
Y-1The ratio of the electric current adjusting range on rank is the current ratio of big or small reference current, is 1:M.
In another embodiment, each current output channels of the led drive circuit among the present invention can drive a plurality of LED, and such as 4, this moment, each current output channels can adopt time-multiplexed mode that a plurality of LED that connect are thereon driven.At this moment, the output driver module can arrange the current data memory block to store the current data of each LED for each LED, when the second mode of operation, can carry out the electric current adjustment to each LED of each current channel, and can be stored in the output driver module adjusting complete current data, can adjust the brightness of the different LED under the same current output channels like this, with the inconsistency of the optical characteristics that remedies these LED.
When concrete the application, the led drive circuit 100 that proposes among the present invention is particularly suitable for the driving LED display, and described light-emitting diode display comprises the led array that is comprised of some LED.If each current output channels of each led drive circuit 100 can drive 4 LED, each led drive circuit can drive 64 LED like this, and a light-emitting diode display may need tens, up to a hundred or more led drive circuit 100.Each current output channels of different LED drive circuit unified adjusted function can improve brightness between LED corresponding to different LED drive circuit and the inconsistency of colourity, and the single channel of each current output channels of same led drive circuit is adjusted function then can improve brightness between LED corresponding to this led drive circuit and the inconsistency of colourity.Because the electric current of led drive circuit is adjusted function, especially single channel is adjusted function, so that can relax the conforming requirement to the optical characteristics of LED, but can guarantee that equally light-emitting diode display has high-quality image display effect.
Above the present invention has been carried out enough detailed description with certain particularity.Under those of ordinary skill in the field should be appreciated that, the description among the embodiment only is exemplary, under the prerequisite that does not depart from true spirit of the present invention and scope, make change and all should belong to protection scope of the present invention.The present invention's scope required for protection is limited by described claims, rather than limited by the foregoing description among the embodiment.
Claims (11)
1. output circuit, it is characterized in that: it comprises:
Reference current determining unit with control end and offset side, its control signal according to control end is selected one between the first reference current and the second reference current, and produce a bias voltage according to selected reference current and exported by described offset side, wherein the first reference current is less than the second reference current;
Some current drives pipes, its source electrode is connected to each other, its drain electrode is connected to each other, and the grid of each current drives pipe links to each other with described offset side by a switching circuit, controls the turn-on and turn-off of corresponding current driving tube by the turn-on and turn-off of controlling each switching circuit; With
Efferent duct, its source electrode links to each other with the drain electrode of described current drives pipe, and its drain electrode is as the output of output circuit, and its grid is controlled the turn-on and turn-off of described efferent duct.
2. output circuit according to claim 1 is characterized in that, the current ratio of the first reference current and the second reference current is 1:M, wherein 1.5≤M≤4.5.
3. output circuit according to claim 2, it is characterized in that, bias voltage on the described offset side drives each current drives pipe makes it produce output current, and drives the current ratio that ratio that each current drives pipe output current that produces and the bias voltage that produces according to the second reference current drive the output current that the corresponding current driving tube produces equals the first reference current and the second reference current according to the bias voltage that the first reference current produces.
4. output circuit according to claim 2 is characterized in that, the ratio of the breadth length ratio of each current drives pipe is respectively: 2
0: 2
1: ...: 2
Y-3: 2
Y-2: X, wherein X satisfies: 2
0+ 2
1+ ... + 2
Y-3+ 2
Y-2Less than M*X and 2
0+ 2
1+ ... + 2
Y-3+ 2
Y-2And the every rank electric current adjusting range the when difference between the M*X is less than or equal to the second reference current, the number of the described current drives pipe of Y.
5. output circuit according to claim 4 is characterized in that, is that the control signal of the control signal of the switching circuit that connects of the current drives pipe of X and reference current determining unit is according to determining with 1 digit current data with relative breadth length ratio.
6. output circuit according to claim 5, it is characterized in that, according to Y digit current data described output circuit is carried out the output current adjustment, wherein determine that according to 1 in the Y digit current data with relative breadth length ratio be the control signal of switching circuit of current drives pipe connection of X and the control signal of reference current determining unit, control the turn-on and turn-off of other each switching circuit according to all the other Y bit data.
7. led drive circuit, it is characterized in that: it comprises:
Control module determines that current is the first mode of operation or the second mode of operation;
The register group, the control data of receive data input input;
Some output driver modules and corresponding output circuit, each output circuit is the arbitrary described output circuit of claim 1-5, and each output driver module drives corresponding output circuit, and each output circuit provides output current by the output of correspondence,
When the first mode of operation, each output driver module starts or stops corresponding output circuit according to the corresponding data in the control data in the register group, when the second mode of operation, described control data include the adjustment modes data, current data and channel address data, when the adjustment modes data are adjusted for unification, each output driver module is according to the unified output current of adjusting each output circuit of described current data, when the adjustment modes data are the single channel adjustment, the output driver module corresponding according to described channel address data enable, the output driver module that this enables are adjusted separately the output current of corresponding output circuit according to described current data.
8. led drive circuit according to claim 7 is characterized in that, described control data are the N position, and described output driver module and output circuit also are N, and wherein N is natural number.
9. led drive circuit according to claim 8 is characterized in that,
It also comprises: the reference current module, and it provides the first reference current and the second reference current, and wherein the first reference current is less than the second reference current,
Each output driver module starts or stops corresponding output circuit according to the corresponding data in the control data in the register group and is: each output driving circuit is according to the turn-on and turn-off of the efferent duct of output circuit corresponding to the correspondence 1 bit data control in the control of the N position in the register group data;
Each output driver module according to the unified output current of adjusting each output circuit of described current data is: each output driver module sends control signal according to 1 in the described current data to the control end of the reference current determining unit of correspondence and with a switching circuit of corresponding output circuit, described reference current determining unit is selected one according to described control signal between the first reference current and the second reference current, each output driver module is according to the turn-on and turn-off of the rest switch circuit in the corresponding output circuit of all the other controls in the described current data;
The output current that the output driver module that this enables is adjusted separately corresponding output circuit according to described current data is: the output driver module that this enables sends control signal according to the control end of 1 determining unit of the reference current to correspondence in described current data and with an on-off circuit of corresponding output circuit, described reference current determining unit is selected one according to described control signal between the first reference current and the second reference current, the output driver module that this enables is according to the turn-on and turn-off of the rest switch circuit in the output circuit of all the other the control correspondences in described current data.
10. led drive circuit according to claim 9, it is characterized in that, each output driver module is stored described current data before the output current of adjusting output circuit according to described current data, the register group includes the N bit shift register, N position output register and N order of the bit register, the serial data of described shift register receive data input input, after latch enable signal comes into force, N bit data in the latch shift register, and current when being the first mode of operation, export described N bit data to described output register, when being the second mode of operation, export described N bit data to described command register current.
11. a light-emitting diode display, it comprises the led array that is comprised of a plurality of LED and the led drive circuit a plurality of as claimed in claim 9 that drives described led array.
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| CN2010102863869A CN101951712B (en) | 2010-09-19 | 2010-09-19 | LED display, LED drive circuit and output circuit of LED drive circuit |
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| CN101937650B (en) * | 2010-09-19 | 2012-11-21 | 无锡力芯微电子股份有限公司 | LED display, LED drive circuit and output circuit thereof |
| CN102737583B (en) * | 2012-07-09 | 2015-06-17 | 深圳市磊芯半导体有限公司 | LED (Light Emitting Diode) driving constant current channel output driver, cascading system and driving method of LED driving constant current channel output driver and cascading system |
| TWI488164B (en) * | 2012-07-23 | 2015-06-11 | My Semi Inc | Led driver circuit, driver system and driving method thereof |
| TWI753908B (en) * | 2016-05-20 | 2022-02-01 | 日商半導體能源硏究所股份有限公司 | Semiconductor device, display device, and electronic device |
| TWI633531B (en) * | 2017-10-13 | 2018-08-21 | 點晶科技股份有限公司 | Light emitting diode driving circuit and light emitting diode display device |
| WO2023087155A1 (en) * | 2021-11-16 | 2023-05-25 | 京东方科技集团股份有限公司 | Driver circuit, driving method therefor, array substrate, and display apparatus |
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| CN101494036A (en) * | 2008-01-24 | 2009-07-29 | 株式会社日立显示器 | Liquid crystal display device |
| CN201868079U (en) * | 2010-09-19 | 2011-06-15 | 无锡力芯微电子股份有限公司 | LED drive circuit and output circuit therein |
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| JP2009289836A (en) * | 2008-05-27 | 2009-12-10 | Oki Data Corp | Light emitting element array, drive control device, recording head, and image forming device |
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| CN101473458A (en) * | 2006-06-21 | 2009-07-01 | 三美电机株式会社 | Light emitting diode driving circuit |
| CN101494036A (en) * | 2008-01-24 | 2009-07-29 | 株式会社日立显示器 | Liquid crystal display device |
| CN201868079U (en) * | 2010-09-19 | 2011-06-15 | 无锡力芯微电子股份有限公司 | LED drive circuit and output circuit therein |
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