CN105120566B - The constant current driving device and its driving method of automatic equalization LED cross luma degree - Google Patents

The constant current driving device and its driving method of automatic equalization LED cross luma degree Download PDF

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Publication number
CN105120566B
CN105120566B CN201510562008.1A CN201510562008A CN105120566B CN 105120566 B CN105120566 B CN 105120566B CN 201510562008 A CN201510562008 A CN 201510562008A CN 105120566 B CN105120566 B CN 105120566B
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module
led string
led
number
voltage
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CN201510562008.1A
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CN105120566A (en
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麦炎全
徐春燕
陈小雨
陈博
邓迅升
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深圳市晟碟半导体有限公司
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00Energy efficient lighting technologies
    • Y02B20/40Control techniques providing energy savings
    • Y02B20/42Control techniques providing energy savings based on timing means or schedule

Abstract

The invention discloses a kind of constant current driving device and its driving method of automatic equalization LED cross luma degree, wherein, the drive device includes rectification module, N number of LED string, N number of switch module, tail current source module, detection module and luminance proportion control module.By luminance proportion control module, within a commutation cycle, receive once over-pressed signal and just light a LED string, after n times overvoltage signal is continuously received, N number of LED string is all lighted;Under-voltage signal is received once, just extinguishes a LED string, after the under-voltage signal of n times is continuously received, N number of LED string all extinguishes;Within a commutation cycle, the duration that each LED string is lighted is different;Within N number of commutation cycle, the total time that each LED string is lighted is identical.Thus, the brightness of each LED string and service life are also just identical, realize the purpose of automatic equalization LED cross luma degree.

Description

The constant current driving device and its driving method of automatic equalization LED cross luma degree

Technical field

The present invention relates to field of LED illumination, the constant current driving device of more particularly to a kind of automatic equalization LED cross luma degree and Its driving method.

Background technology

As shown in figure 1, the structured flowchart for conventional linear constant current driving system.The lower section of LED string 1~4 connects one respectively Individual constant-current source to ground.Raised in voltage and decline process, the illuminating state of LED 1~LED of string string 4 can change therewith.Such as figure It is the oscillogram of conventional linear constant current driving system shown in 2.From figure 2 it can be seen that LED 1~LED of string string 4 is Sequential illumination, inside the cycle of each rectifier bridge output, the lighting time of LED string 1 is most long, LED 2~LED of string The lighting time of string 4 is sequentially reduced, and the brightness for ultimately resulting in LED string 1 to LED string 4 is exported in the cycle in a rectifier bridge It is sequentially reduced.Different according to the quantity of each LED string, each LED string luminance difference is different, common LED1 ~ LED4 by The configuration of identical quantity lamp bead, LED1 and LED4 luminance difference can reach 3:1.Simultaneously as when each LED string is averagely lighted Between(Power or brightness)Difference, the light decay of each LED string can be caused different, LED1 light decays can it is faster than LED4 a lot, it is so whole The life-span of individual LED lamp can be limited to the LED1 light decay life-span.

LED lamp such as bulb lamp, fluorescent tube etc. driven using conventional linear constant current, due to the luminosity of LED lamp bead(By Above-mentioned lighting time difference causes)It is inconsistent, when nearer apart from light fixture(Such as 0.5m ~ 0.6m), human eye can see easily very much Out some lamp beads are partially dark in light fixture, overall to feel that light fixture has hot spot.Especially for this application of fluorescent tube, LED bead string Capable is arranged on fluorescent tube, and hot spot meeting caused by LED lamp bead brightness is inconsistent is it is obvious that had a strong impact on the vision effect of light fixture Fruit, in addition to client cause light fixture damage impression.

Thus prior art could be improved and improve.

The content of the invention

In view of in place of above-mentioned the deficiencies in the prior art, it is an object of the invention to provide a kind of automatic equalization LED cross luma The constant current driving device and its driving method of degree, make lighting time and the power all same of each LED string, it is balanced each The brightness of LED string, improve the service life of LED lamp.

In order to achieve the above object, this invention takes following technical scheme:

A kind of constant current driving device of automatic equalization LED cross luma degree, including

Rectification module, for carrying out rectification to the alternating current of outside input and being powered to LED string group;

LED string group, including N number of LED string, it is connected in series between N number of LED string;

It is N number of to be used to control the switch module that LED string is lighted and extinguished, switch module one LED of corresponding control String;

Tail current source module, for the constant current hold for controlling electric current in LED string, making LED string;

Detection module, for the voltage in detecting real-time tail current source module, when the voltage in tail current source module is higher than During first threshold voltage, output overvoltage signal to luminance proportion control module;When the voltage in tail current source module is less than second During threshold voltage, under-voltage signal is exported to luminance proportion control module;

Luminance proportion control module, within a commutation cycle, when receiving once over-pressed signal, making a switch Module lights corresponding LED string, after the luminance proportion control module continuously receives n times overvoltage signal, passes through N number of switch Module, light all LED strings;When receiving once under-voltage signal, make LED string corresponding to a switch module extinguishing, institute State after luminance proportion control module continuously receives the under-voltage signal of n times, by N number of switch module, extinguish all LED strings;Make Obtaining within a commutation cycle, the duration that each LED string is lighted is different, and within N number of commutation cycle, each LED The total time that lamp string is lighted is identical;

Wherein, N is the positive integer more than or equal to 2.

In the constant current driving device of described automatic equalization LED cross luma degree, the linear constant current drive device also includes N It is individual to be used to the voltage of detection module output carrying out level shift, make the voltage shifts that detection module exports to the electricity of switch module The level shift module in domain, the corresponding switch module of a level shift module are pressed, the luminance proportion control module passes through N Individual level shift module connects N number of switch module.

In the constant current driving device of described automatic equalization LED cross luma degree, break-make that the switch module passes through itself Lighting and extinguish come LED string corresponding to controlling;The positive pole of LED string corresponding to the input connection of the switch module, The negative pole of LED string corresponding to the output end connection of the switch module, electricity corresponding to the control terminal connection of the switch module The output end of translational shifting module.

In the constant current driving device of described automatic equalization LED cross luma degree, the switch module include first resistor and First metal-oxide-semiconductor;The source electrode of first metal-oxide-semiconductor is the input of switch module, connects the positive pole of corresponding LED string, also passes through First resistor connects the grid of the first metal-oxide-semiconductor, and the drain electrode of first metal-oxide-semiconductor is the output end of switch module, the corresponding LED of connection The negative pole of lamp string, the grid of first metal-oxide-semiconductor is the control terminal of switch module, the output of level shift module corresponding to connection End.

In the constant current driving device of described automatic equalization LED cross luma degree, the level shift module includes the second electricity Resistance and the second metal-oxide-semiconductor, the grid of second metal-oxide-semiconductor is the input of level shift module, connection luminance proportion control module Corresponding output end, second metal-oxide-semiconductor drain electrode for level shift module output end, connection corresponding to switch module control End processed, the source electrode of second metal-oxide-semiconductor are grounded by second resistance.

In the constant current driving device of described automatic equalization LED cross luma degree, the tail current source module includes the first electricity Source, operational amplifier, 3rd resistor and the 3rd metal-oxide-semiconductor;3rd metal-oxide-semiconductor drain electrode for tail current source module input, The negative pole of LED string group is connected, the inverting input of the source electrode concatenation operation amplifier of the 3rd metal-oxide-semiconductor, also passes through the 3rd Resistance eutral grounding, the negative pole of first power supply are the output end of tail current source module, and the negative pole ground connection of first power supply is described The normal phase input end of the positive pole concatenation operation amplifier of first power supply, the output end of the operational amplifier connect the 3rd metal-oxide-semiconductor Grid.

In the constant current driving device of described automatic equalization LED cross luma degree, the detection module includes the 4th resistance, the Five resistance, the 6th resistance, first comparator, the second comparator and second source;One end of 4th resistance is detection module Input, connect the input of tail current source module and the negative pole of LED string group, the other end connection the of the 4th resistance The positive input of the normal phase input end of one comparator, one end that the 6th resistance is also connected by the 5th resistance and the second comparator End;6th resistance eutral grounding, the inverting input and the second comparator of the positive pole connection first comparator of the second source Inverting input, the second source negative pole ground connection;The output of the output end of the first comparator and the second comparator Hold the output end for detection module, connect the input of luminance proportion control module.

In the constant current driving device of described automatic equalization LED cross luma degree, the N is 4.

A kind of driving method of constant current driving device using above-mentioned automatic equalization LED cross luma degree, including:

Voltage in detecting real-time tail current source module, when the voltage in tail current source module is higher than first threshold voltage When, output overvoltage signal to luminance proportion control module;It is defeated when the voltage in tail current source module is less than second threshold voltage Go out under-voltage signal to luminance proportion control module;

Luminance proportion control module is within a commutation cycle, when receiving once over-pressed signal, makes a switch module LED string, after the luminance proportion control module continuously receives n times overvoltage signal, passes through N number of switching molding corresponding to lighting Block, light all LED strings;When receiving once under-voltage signal, make LED string corresponding to a switch module extinguishing, it is described After luminance proportion control module continuously receives the under-voltage signal of n times, by N number of switch module, extinguish all LED strings;So that Within a commutation cycle, the duration that each LED string is lighted is different, and within N number of commutation cycle, each LED The total time that string is lighted is identical.

Compared to prior art, the constant current driving device of automatic equalization LED cross luma degree provided by the invention and its driving Method, by the voltage in detection module detecting real-time tail current source module, and output overvoltage or under-voltage signal are to luminance proportion Control module;Luminance proportion control module is within a commutation cycle, when receiving once over-pressed signal, makes a switch module LED string, after the luminance proportion control module continuously receives n times overvoltage signal, passes through N number of switching molding corresponding to lighting Block, light all LED strings;When receiving once under-voltage signal, make LED string corresponding to a switch module extinguishing, it is described After luminance proportion control module continuously receives the under-voltage signal of n times, by N number of switch module, extinguish all LED strings;So that Within a commutation cycle, the duration that each LED string is lighted is different;And within N number of commutation cycle, each LED The total time that lamp string is lighted is identical;Because luminance proportion control module ensure that N number of LED string is lighted within N number of commutation cycle Total time be all identical, therefore each power of the LED string within N number of commutation cycle is also identical, certainly, each LED The brightness of lamp string and service life are also just identical, realize the purpose of automatic equalization LED cross luma degree.

Brief description of the drawings

Fig. 1 is the structured flowchart of existing linear constant current drive system.

Fig. 2 is the oscillogram of existing linear constant current drive system.

Fig. 3 is the structured flowchart of the constant current driving device of automatic equalization LED cross luma degree provided by the invention.

Fig. 4 is the oscillogram of the constant current driving device of automatic equalization LED cross luma degree provided by the invention.

Fig. 5 is the circuit of switch module in the constant current driving device of automatic equalization LED cross luma degree provided by the invention Figure.

Fig. 6 is the electricity of level shift module in the constant current driving device of automatic equalization LED cross luma degree provided by the invention Lu Tu.

Fig. 7 is the electricity of tail current source module in the constant current driving device of automatic equalization LED cross luma degree provided by the invention Lu Tu.

Fig. 8 is the circuit of detection module in the constant current driving device of automatic equalization LED cross luma degree provided by the invention Figure.

Fig. 9 is the structure of another embodiment in the constant current driving device of automatic equalization LED cross luma degree provided by the invention Block diagram.

Figure 10 is the method stream of the driving method of the constant current driving device of automatic equalization LED cross luma degree provided by the invention Cheng Tu.

Embodiment

The present invention provides a kind of constant current driving device and its driving method of automatic equalization LED cross luma degree.To make this hair Bright purpose, technical scheme and effect are clearer, clear and definite, and the embodiment that develops simultaneously referring to the drawings is to of the invention further detailed Explanation.It should be appreciated that specific embodiment described herein is not intended to limit the present invention only to explain the present invention.

The constant current driving device of automatic equalization LED cross luma degree provided by the invention, modules therein can use more Kind connected mode, as shown in figure 3, being the preferred embodiment of the present invention.

The constant current driving device of automatic equalization LED cross luma degree provided by the invention, including rectification module 10, LED string Group 20, tail current source module 30, detection module 40, luminance proportion control module 50 and it is N number of be used for control LED string to light and put out The switch module 70 to go out, wherein, switch module one LED string of corresponding control.

The rectification module 10, for carrying out rectification to the alternating current of outside input and being powered to LED string group 20;It is excellent Choosing, the rectification module 10 is rectifier bridge.

The LED string group 20, including N number of LED string, it is connected in series between N number of LED string.

The tail current source module 30, for the constant current hold for controlling electric current in LED string, making LED string.

The detection module 40, the voltage of the module in parallel with detection module 40 for detecting real-time, when with detection module When voltage in 40 modules in parallel is higher than first threshold voltage Vth1, output overvoltage signal to luminance proportion control module 50; When the voltage in the module in parallel with detection module 40 is less than second threshold voltage Vth2, under-voltage signal is exported to luminance proportion Control module 50.In the present embodiment, the module in parallel with detection module 40 is tail current source module 30.Therefore the detection module 40 are specifically used for the voltage in detecting real-time tail current source module 30, when the voltage in tail current source module 30 is higher than first threshold During voltage Vth1, output overvoltage signal to luminance proportion control module 50;When the voltage in tail current source module 30 is less than second During threshold voltage vt h2, under-voltage signal is exported to luminance proportion control module 50.First threshold voltage Vth1 setting causes tail Voltage in current source module 30 serves the effect of overvoltage protection not over first threshold voltage Vth1;Second Threshold electricity Pressure Vth2 setting causes the voltage in tail current source module 30 to be not less than second threshold voltage Vth2, serves low-voltage variation Effect;It follows that the present invention can be by the voltage stabilization of tail current source module 30 in first threshold voltage Vth1 and the second threshold Between threshold voltage Vth2.

The luminance proportion control module 50, within a commutation cycle, when receiving once over-pressed signal, making one Individual switch module 70 is disconnected to light corresponding LED string, and the luminance proportion control module 50 continuously receives n times overvoltage letter After number, pass through N number of switch module 70(Disconnect all switch modules 70), light all LED strings;Receive once under-voltage letter Number when, open a switch module 70 and continuously received with LED string corresponding to extinguishing, the luminance proportion control module 50 After n times are under-voltage signal, pass through N number of switch module 70(Open all switch modules 70), extinguish all LED strings;So that In one commutation cycle, the duration that each LED string is lighted is different, i.e., the fluorescent lifetime of each LED string is different;And Within N number of commutation cycle, the total time that each LED string is lighted is identical, i.e., each LED string luminous total time is identical. Further, within a commutation cycle, the LED string lighted at first finally extinguishes, second LED string inverse lighted Two extinguishings, by that analogy;Certainly, each commutation cycle is not always the case, so, each by adjusting within N number of commutation cycle What LED string was lighted in the commutation cycle puts in order(Fully intermeshing), make what N number of LED string lighted within N number of commutation cycle Total time phase.Because luminance proportion control module 50 ensure that total time that N number of LED string lights within N number of commutation cycle all It is identical, therefore each power of the LED string within N number of commutation cycle is also identical, certainly, the brightness of each LED string It is also just identical with service life, the purpose of automatic equalization LED cross luma degree is realized, improves the service life of light fixture.

Wherein, N is the positive integer more than or equal to 2, and the optimal value of the N is 3 and 4.

The rectification module 10 passes through the input of the connection detection module 40 of LED string group 20 and tail current source module 30 Input, the input of the output end connection luminance proportion control module 50 of the detection module 40, the tail current source module 30 output head grounding;N number of output end of the luminance proportion control module 50 connects N number of LED by N number of switch module 70 String.

Please continue to refer to Fig. 3, in the constant current driving device of automatic equalization LED cross luma degree provided by the invention, the N is excellent Elect 4 as, i.e. the LED string group 20 includes four LED strings, respectively the first LED string 210, the second LED string 220, 3rd LED string 230 and the 4th LED string 240, the lamp bead quantity in each LED string can be with identical also different, according to tool Depending on body situation.

Also referring to Fig. 4, Vac is the waveform of rectifier bridge output voltage, and VLED1, VLED2, VLED3 and VLED4 distinguish For the voltage waveform of the first LED string 210, the second LED string 220, the 3rd LED string 230 and the 4th LED string 240.First When the individual commutation cycle starts(When rectifier bridge starts power supply), four LED strings are extinguished by corresponding switch module 70.With output Voltage Vac is stepped up, and the voltage increase in tail current source module 30, detection module 40 is detected in tail current source module 30 Voltage is higher than first threshold voltage Vth1, output overvoltage signal to luminance proportion control module 50;Luminance proportion control module 50 First LED string 210 is lighted by switch module 70.First LED string 210 is lighted, by the voltage in tail current source module 30 It is pulled down to below first threshold voltage Vth1, will not temporarily lights other LED strings again.Because output voltage Vac is constantly in Ascent stage, the voltage in tail current source module 30 exceed first threshold voltage Vth1, luminance proportion control module 50 second Second LED string 220 is lighted by switch module 70.Second LED string 220 is lighted, because partial pressure acts on, by tail current source mould Voltage pull-down on block 30 will not temporarily light other LED strings again to below first threshold voltage Vth1.After short time, Voltage third time in tail current source module 30 exceedes first threshold voltage Vth1, and luminance proportion control module 50 passes through switching molding Block 70 lights the 3rd LED string 230.3rd LED string 230 is lighted the voltage pull-down in tail current source module 30 to first Below threshold voltage vt h1, other LED strings will not be temporarily lighted again.After short time, the voltage in tail current source module 30 Exceed first threshold voltage Vth1 4th time, luminance proportion control module 50 lights the 4th LED string by switch module 70 240.Thus, all lighted in the output voltage ascent stage of first commutation cycle, four LED strings.When first rectification The output voltage in cycle enters the decline stage, and the voltage in tail current source module 30 is less than second threshold voltage Vth2 for the first time, After luminance proportion control module 50 receives under-voltage signal, the 4th LED string 240 is controlled to extinguish by switch module 70, i.e., at first The LED light group 210 lighted finally is extinguished, and the LED light group 240 lighted at the latest is extinguished at first so that within first commutation cycle The size of the fluorescent lifetime of four LED strings is:The LED strings 230 of first LED string, 210 220 > of > the second LED strings the 3rd The LED strings 240 of > the 4th.Due to ensure in four commutation cycles, the first LED string 210, the second LED string the 220, the 3rd LED string 230 is identical with the luminous total time of the 4th LED string 240, therefore within second commutation cycle, in luminance proportion control Under the control of molding block 50, the size of the fluorescent lifetime of four LED strings is:The LED strings 230 of second LED string, 220 > the 3rd The first LEDs of the > string 210 of the 4th LED strings of > 240.By that analogy, in four commutation cycles, lighting for four LED strings is suitable Sequence meets fully intermeshing.Finally, only need four commutation cycles that the fluorescent lifetime of four LED strings can be made identical, realize automatic The purpose of balanced LED cross luma degree.Because the time of commutation cycle is extremely short, even four even more commutation cycles fold Add, its time is also extremely short, therefore the constant current driving device of automatic equalization LED cross luma degree provided by the invention makes each LED The fluorescent lifetime of lamp string is all identical, and luminosity and power are also just identical, improve the luminescent quality and service life of light fixture.

Please continue to refer to Fig. 3, in the constant current driving device of described automatic equalization LED cross luma degree, in addition to N number of it is used for The voltage that detection module 40 exports is subjected to level shift, makes the voltage shifts that detection module 40 exports to the electricity of switch module 70 The level shift module 60 in domain, the corresponding switch module 70 of a level shift module 60 are pressed, the luminance proportion controls mould Block 50 connects N number of switch module 70 by N number of level shift module 60.Because luminance proportion control module 50 can be according to detection mould The output of block 40 carrys out controlling switch module 70, and the ground reference of detection module 40 and tail current source module 30 is rectification module 10 negative sense output, its ground reference is different from the ground reference of switch module 70, so needing detection module 40 Output carries out level shift.By the level shift module 60, make control of the luminance proportion control module 50 to switch module 70 System is more accurate, further increases the luminous equilibrium degree of LED string.

Further, the switch module 70 is controlled the extinguishing of corresponding LED string by the break-make of itself and lighted; The positive pole of LED string corresponding to the input connection of the switch module 70, the output end connection of the switch module 70 are corresponding LED string negative pole, the switch module control terminal connection corresponding to level shift module 60 output end.Work as switching molding Block 70 is off(Disconnect)During state, LED string is in illuminating state;Opened when switch module 70 is in(Closure)State When, LED string is in(Close)The state of extinguishing.The lighting and extinguish progress to LED string by the way of path and short circuit Control, simple and practical, the circuit without complexity can be completed.

Referring to Fig. 5, the switch module 70 includes first resistor R1 and the first metal-oxide-semiconductor Q1;The first metal-oxide-semiconductor Q1's Source electrode is the input of switch module 70, connects the positive pole of corresponding LED string, also passes through first resistor R1 the first metal-oxide-semiconductors of connection Q1 grid, the drain electrode of the first metal-oxide-semiconductor Q1 is the output end of switch module 70, connects the negative pole of corresponding LED string, described First metal-oxide-semiconductor Q1 grid for switch module 70 control terminal, connection corresponding to level shift module 60 output end.

Referring to Fig. 6, the level shift module 60 includes second resistance R2 and the second metal-oxide-semiconductor Q2, second metal-oxide-semiconductor Q2 grid is the input of level shift module 60, output end corresponding to connection luminance proportion control module 50, described second Metal-oxide-semiconductor Q2 drain electrode for level shift module 60 output end, connection corresponding to switch module 70 control terminal, described second Metal-oxide-semiconductor Q2 source electrode is grounded by second resistance R2.

Referring to Fig. 7, the tail current source module 30 include the first power supply V1, operational amplifier U1,3rd resistor R3 and 3rd metal-oxide-semiconductor Q3;The drain electrode of the 3rd metal-oxide-semiconductor Q3 is the input of tail current source module 30, connects the negative of LED string group 20 Pole, the source electrode concatenation operation amplifier U1 of the 3rd metal-oxide-semiconductor Q3 inverting input, also it is grounded by 3rd resistor R3, institute The negative pole for stating the first power supply V1 is the output end of tail current source module 30, and the negative pole of the first power supply V1 is grounded, described first Power supply V1 positive pole concatenation operation amplifier U1 normal phase input end, the output end of the operational amplifier U1 connect the 3rd MOS Pipe Q3 grid.

Referring to Fig. 8, the detection module 40 compares including the 4th resistance R4, the 5th resistance R5, the 6th resistance R6, first Device U2, the second comparator U3 and second source V2;Input, connection tail of the one end of the 4th resistance R4 for detection module 40 The input of current source module 30 and the negative pole of LED string group 20, the other end connection first comparator of the 4th resistance R4 U2 normal phase input end, also inputted by the resistance R6 of the 5th resistance R5 connections the 6th one end and the second comparator U2 positive End;The 6th resistance R6 ground connection, the positive pole connection first comparator U2 of second source V2 inverting input and second Comparator U3 inverting input, the negative pole ground connection of the second source V2;The output end and second of the first comparator U2 Comparator U3 output end is the output end of detection module 40, the input of connection luminance proportion control module 50.That is, when first When comparator U2 exports low level, the low level is under-voltage signal, and when the second comparator U3 exports high level, the high level is Over-pressed signal.Specifically, the voltage of the second source V2 outputs is 1.2V.The 4th resistance R4, the 5th resistance R5 and The ratio of six resistance R6 resistances is:25:4:1.It is arranged such, is in order to ensure the voltage that the input of detection module 40 inputs is less than During 6V, detection module 40 exports under-voltage signal, when the voltage of the input input of detection module 40 is more than 36V, detection module 40 Output overvoltage signal.In the present embodiment, the 4th resistance R4, the 5th resistance R5 and the 6th resistance R6 resistance are respectively 1M Europe, 160K Europe and 40K Europe.

In another embodiment of the invention, the structural frames of the constant current driving device of the automatic equalization LED cross luma degree Figure as shown in figure 9, in parallel with detection module is LED string group 20 and tail current source module 30, therefore, the detection module 40 is examined What is surveyed is the output voltage of rectifier bridge 10, that is, LED string group 20 and the voltage sum of tail current source module 30, i.e. the inspection The output voltage of the detecting real-time rectifier bridge 10 of module 40 is surveyed, when the output voltage of rectifier bridge is between first threshold and Second Threshold When(When the output voltage of rectifier bridge is higher than first threshold), output status signal 1 arrives luminance proportion control module;When rectifier bridge When output voltage is between Second Threshold and the 3rd threshold value(When the output voltage of rectifier bridge is higher than Second Threshold), output state letter Numbers 2 arrive luminance proportion control module;When the output voltage of rectifier bridge is between the 3rd threshold value and the 4th threshold value(Rectifier bridge it is defeated When going out voltage and being higher than three threshold values), output status signal 3 arrives luminance proportion control module;When the output voltage of rectifier bridge is higher than During four threshold values, output status signal 4 arrives luminance proportion control module;……;When the output voltage of rectifier bridge is higher than N threshold values When, output status signal N to luminance proportion control module;Wherein, first threshold<Second Threshold<3rd threshold value<4th threshold value <……<N threshold values.

The size of the threshold value is:The VF voltages of LED string group 20 and the minimum of tail current source module 30 it With.That is, when the commutation cycle just starts, the neither one LED string of LED string group 20 is lit, and first threshold is tail current source mould The minimum of block 30.After the output voltage of rectifier bridge exceedes first threshold, luminance proportion control module 50 lights one LED string, first threshold are the VF voltages of LED string group 20(The VF voltages for the LED string lighted)With tail current source module 30 Minimum sum.…….After more than the N-1 threshold value of the output voltage of rectifier bridge, luminance proportion control module 50 N-1 LED string is lighted, N-1 LED string is now shared and is lit, N-1 threshold values are the VF voltages of LED string group 20(N- The VF voltages of 1 LED string lighted)With the minimum sum of tail current source module 30.The output voltage of rectifier bridge After n-th threshold value, all LED strings are lit.The like, when rectifier bridge output voltage declines, close LED string Flow be also such.Because other operation principles in embodiment illustrated in fig. 9 are identical with a upper embodiment(Luminance proportion controls The control of module 50, correspondingly make over-pressed signal and under-voltage signal into each status signal), will not be repeated here.

Referring to Fig. 10, the present invention also provides a kind of constant current driving of automatic equalization LED cross luma degree based on shown in Fig. 3 The driving method of device, methods described include:

Voltage on S10, detecting real-time tail current source module, when the voltage in tail current source module is higher than first threshold electricity During pressure, output overvoltage signal to luminance proportion control module;When the voltage in tail current source module is less than second threshold voltage, Under-voltage signal is exported to luminance proportion control module.

S20, luminance proportion control module are within a commutation cycle, when receiving once over-pressed signal, make a switch Module lights corresponding LED string, after the luminance proportion control module continuously receives n times overvoltage signal, passes through N number of switch Module, light all LED strings;When receiving once under-voltage signal, make LED string corresponding to a switch module extinguishing, institute State after luminance proportion control module continuously receives the under-voltage signal of n times, by N number of switch module, extinguish all LED strings;Make Obtaining within a commutation cycle, the duration that each LED string is lighted is different, and within N number of commutation cycle, each LED The total time that lamp string is lighted is identical.

Because the operation principle and feature of the driving method have elaborated in the embodiment shown in fig. 3, herein no longer Repeat.

It is understood that for those of ordinary skills, can be with technique according to the invention scheme and its hair Bright design is subject to equivalent substitution or change, and all these changes or replacement should all belong to the guarantor of appended claims of the invention Protect scope.

Claims (7)

  1. A kind of 1. constant current driving device of automatic equalization LED cross luma degree, it is characterised in that including
    Rectification module, for carrying out rectification to the alternating current of outside input and being powered to LED string group;
    LED string group, including N number of LED string, it is connected in series between N number of LED string;
    It is N number of to be used to control the switch module that LED string is lighted and extinguished, switch module one LED string of corresponding control;
    Tail current source module, for the constant current hold for controlling electric current in LED string, making LED string;
    Detection module, for the voltage in detecting real-time tail current source module, when the voltage in tail current source module is higher than first During threshold voltage, output overvoltage signal to luminance proportion control module;When the voltage in tail current source module is less than Second Threshold During voltage, under-voltage signal is exported to luminance proportion control module;
    Luminance proportion control module, within a commutation cycle, when receiving once over-pressed signal, making a switch module LED string, after the luminance proportion control module continuously receives n times overvoltage signal, passes through N number of switching molding corresponding to lighting Block, light all LED strings;When receiving once under-voltage signal, make LED string corresponding to a switch module extinguishing, it is described After luminance proportion control module continuously receives the under-voltage signal of n times, by N number of switch module, extinguish all LED strings;So that Within a commutation cycle, the duration that each LED string is lighted is different, and within N number of commutation cycle, each LED The total time that string is lighted is identical;
    Wherein, N is the positive integer more than or equal to 2;
    Within a commutation cycle, the 1st extinguishing reciprocal of the 1st LED string lighted, the LED string inverse that n-th is lighted the N number of extinguishing, putting in order for LED string is adjusted by way of fully intermeshing makes N number of LED string be lighted within N number of commutation cycle Total time it is identical;
    Linear constant current drive device also includes N number of voltage for being used to export detection module and carries out level shift, makes detection module The voltage shifts of output are to the level shift module of the voltage domain of switch module, the corresponding switching molding of level shift module Block, the luminance proportion control module connect N number of switch module by N number of level shift module;
    The tail current source module includes the first power supply, operational amplifier, 3rd resistor and the 3rd metal-oxide-semiconductor;3rd metal-oxide-semiconductor Drain electrode for tail current source module input, connect LED string group negative pole, the source electrode concatenation operation of the 3rd metal-oxide-semiconductor The inverting input of amplifier, also it is grounded by 3rd resistor, the negative pole of first power supply is the output of tail current source module End, the negative pole ground connection of first power supply, the normal phase input end of the positive pole concatenation operation amplifier of first power supply, the fortune The output end for calculating amplifier connects the grid of the 3rd metal-oxide-semiconductor.
  2. 2. the constant current driving device of automatic equalization LED cross luma degree according to claim 1, it is characterised in that described to open Close module and pass through the break-make of itself lighting and extinguish come LED string corresponding to controlling;The input connection of the switch module The positive pole of corresponding LED string, the negative pole of LED string, the switch module corresponding to the output end connection of the switch module Control terminal connection corresponding to level shift module output end.
  3. 3. the constant current driving device of automatic equalization LED cross luma degree according to claim 2, it is characterised in that described to open Closing module includes first resistor and the first metal-oxide-semiconductor;The source electrode of first metal-oxide-semiconductor is the input of switch module, connected correspondingly The positive pole of LED string, the grid that the first metal-oxide-semiconductor is also connected by first resistor, the drain electrode of first metal-oxide-semiconductor is switch module Output end, the negative pole of the corresponding LED string of connection, the grid of first metal-oxide-semiconductor is the control terminal of switch module, connection is corresponding Level shift module output end.
  4. 4. the constant current driving device of automatic equalization LED cross luma degree according to claim 3, it is characterised in that the electricity Translational shifting module includes second resistance and the second metal-oxide-semiconductor, the grid of second metal-oxide-semiconductor for level shift module input, Output end corresponding to luminance proportion control module is connected, the drain electrode of second metal-oxide-semiconductor is the output end of level shift module, connected The control terminal of switch module, the source electrode of second metal-oxide-semiconductor are grounded by second resistance corresponding to connecing.
  5. 5. the constant current driving device of automatic equalization LED cross luma degree according to claim 4, it is characterised in that the inspection Surveying module includes the 4th resistance, the 5th resistance, the 6th resistance, first comparator, the second comparator and second source;Described 4th One end of resistance for detection module input, connect the input of tail current source module and the negative pole of LED string group, described the The normal phase input end of the other end connection first comparator of four resistance, one end and that the 6th resistance is also connected by the 5th resistance The normal phase input end of two comparators;6th resistance eutral grounding, the positive pole of the second source connect the anti-phase of first comparator The inverting input of input and the second comparator, the negative pole ground connection of the second source;The output end of the first comparator Output end with the second comparator is the output end of detection module, the input of connection luminance proportion control module.
  6. 6. the constant current driving device of automatic equalization LED cross luma degree according to claim 5, it is characterised in that the N is 4。
  7. 7. a kind of driving method using the constant current driving device of automatic equalization LED cross luma degree described in claim 1, its feature It is, including:
    Voltage in detecting real-time tail current source module, it is defeated when the voltage in tail current source module is higher than first threshold voltage Go out over-pressed signal to luminance proportion control module;When the voltage in tail current source module is less than second threshold voltage, output is owed Signal is pressed to luminance proportion control module;
    Luminance proportion control module is within a commutation cycle, when receiving once over-pressed signal, lights a switch module Corresponding LED string, after the luminance proportion control module continuously receives n times overvoltage signal, pass through N number of switch module, point Bright all LED strings;When receiving once under-voltage signal, make switch module extinguish corresponding to LED string, the brightness is equal After weighing apparatus control module continuously receives the under-voltage signal of n times, by N number of switch module, extinguish all LED strings;So that at one In commutation cycle, the duration that each LED string is lighted is different, and within N number of commutation cycle, each LED string is lighted Total time it is identical;
    Within a commutation cycle, the 1st extinguishing reciprocal of the 1st LED string lighted, the LED string inverse that n-th is lighted the N number of extinguishing, putting in order for LED string is adjusted by way of fully intermeshing makes N number of LED string be lighted within N number of commutation cycle Total time it is identical;
    The tail current source module includes the first power supply, operational amplifier, 3rd resistor and the 3rd metal-oxide-semiconductor;3rd metal-oxide-semiconductor Drain electrode for tail current source module input, connect LED string group negative pole, the source electrode concatenation operation of the 3rd metal-oxide-semiconductor The inverting input of amplifier, also it is grounded by 3rd resistor, the negative pole of first power supply is the output of tail current source module End, the negative pole ground connection of first power supply, the normal phase input end of the positive pole concatenation operation amplifier of first power supply, the fortune The output end for calculating amplifier connects the grid of the 3rd metal-oxide-semiconductor.
CN201510562008.1A 2015-09-07 2015-09-07 The constant current driving device and its driving method of automatic equalization LED cross luma degree CN105120566B (en)

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