CN101998725A - Drive circuit of light-emitting diode - Google Patents
Drive circuit of light-emitting diode Download PDFInfo
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- CN101998725A CN101998725A CN2009101663307A CN200910166330A CN101998725A CN 101998725 A CN101998725 A CN 101998725A CN 2009101663307 A CN2009101663307 A CN 2009101663307A CN 200910166330 A CN200910166330 A CN 200910166330A CN 101998725 A CN101998725 A CN 101998725A
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Abstract
The invention discloses a drive circuit of a light-emitting diode, comprising a voltage adjustment unit, a switch unit and a control unit, wherein the control unit is electrically connected between the voltage adjustment unit and the switch unit; the voltage adjustment unit is used for outputting a drive voltage to one end of each of multiple loading units, and the switch unit is used for electrically connecting with the other end of each of the multiple loading units; and when the switch unit electrically connects one light-emitting diode string of the loading unit to a current source, the voltage adjustment unit adjusts the value of the driving voltage so as to correspond to the connected light-emitting diode string, thus improving the driving problem caused by electrical property difference of the light-emitting diodes.
Description
Technical field
The invention relates to a kind of light-emitting diode (Light Emitting Diode, drive circuit LED), and particularly relevant for the drive circuit of LED-backlit.
Background technology
Liquid crystal or plasma display panel have been used on the display screen of consumption electronic products such as mobile phone, mobile computer, personal computer and PDA(Personal Digital Assistant) in large quantities.Yet,, therefore need dispose a backlight in the panel rear to provide liquid crystal panel needed display light source because the panel itself of liquid crystal or plasma display panel does not have luminous function.Backlight in the market have flat florescent lamp, cold-cathode fluorescence lamp (Cold Cathode Fluorescent Lamp, CCFL) and light-emitting diode or the like.Wherein, light-emitting diode because of have little, the no thermal radiation of volume, advantage such as power consumption is low, the life-span is long and reaction speed is good, and can solve very many problems that flat florescent lamp and cold-cathode fluorescence lamp were difficult to overcome in the past, thereby be the backlight that is expected present stage.
In module backlight; usually can comprise many by a plurality of LED formed LED string of connecting; aspect the driving of LED string; typically use identical voltage and drive all LED in the module backlight; (Pulse Width Modulation, PWM) signal is adjusted the luminous intensity of LED out of the ordinary utilizing pulse wave width modulation then.Yet, because the difference of material processing procedure, the therefore required voltage difference to some extent when conducting (lighting) of the indivedual LED strings in the module backlight, thereby cause the difference of three kinds of coloured light intensity of RGB easily, and influence the quality of white light.In addition, also can cause the problem of power consumption to produce if use higher driving voltage to drive all LED strings.
Summary of the invention
The invention provides a kind of drive circuit of light-emitting diode, can adjust its driving voltage, make drive circuit, and reach better white light effect and reduce power consumption applicable to LED with different conducting voltage according to the electrical property difference of LED or LED string.
Hold above-mentionedly, the present invention proposes a kind of drive circuit, is used to drive a plurality of load units, and each above-mentioned load unit comprises at least one light-emitting diode, and above-mentioned drive circuit comprises a voltage-adjusting unit, a switch element and a control unit.Voltage-adjusting unit is in order to export a driving voltage to one of above-mentioned load unit end, and switch element is electrically connected between the other end and a current source of above-mentioned load unit, in order to selectivity one of above-mentioned load unit is electrically connected to above-mentioned current source.Control unit is electrically connected at above-mentioned voltage-adjusting unit and above-mentioned switch element, wherein first control signal exported according to control unit of voltage-adjusting unit is adjusted driving voltage, and the above-mentioned load unit of the second control signal selectivity conducting that switch element is exported according to control unit one with above-mentioned current source.
Wherein, when switch element was electrically connected to above-mentioned current source with one first load unit in the above-mentioned load unit, the magnitude of voltage that voltage-adjusting unit can be adjusted driving voltage was with corresponding to above-mentioned first load unit.
In an embodiment of the present invention, wherein when switch element is electrically connected to above-mentioned current source with one second load unit in the above-mentioned load unit, the magnitude of voltage that above-mentioned voltage-adjusting unit is adjusted above-mentioned driving voltage is with corresponding to above-mentioned second load unit.
In an embodiment of the present invention, wherein above-mentioned switch element is electrically connected to above-mentioned current source with above-mentioned load unit more in regular turn, and the magnitude of voltage that above-mentioned voltage-adjusting unit is then adjusted above-mentioned driving voltage in regular turn is with corresponding to one of the above-mentioned load unit that is electrically connected or above-mentioned load unit.
In an embodiment of the present invention, above-mentioned switch element comprises a plurality of switches and a switch control unit, wherein above-mentioned switch is electrically connected at respectively between above-mentioned load unit and the above-mentioned current source, above-mentioned switch control unit is electrically connected at above-mentioned switch respectively, and according to above-mentioned second control signal with the above-mentioned switch of selectivity conducting.
In an embodiment of the present invention, wherein above-mentioned switch comprises N transistor npn npn or P transistor npn npn.
In an embodiment of the present invention, wherein above-mentioned voltage-adjusting unit comprises a booster circuit or a reduction voltage circuit.
In an embodiment of the present invention, wherein above-mentioned load unit comprises a light emitting diode string at least, and above-mentioned light emitting diode string comprises a plurality of first light-emitting diodes that are one another in series.
In an embodiment of the present invention, wherein above-mentioned current source is a constant current source.
The present invention drives LED or LED string in the module backlight because of adopting adjustable driving voltage, therefore can provide suitable driving voltage according to the electrical property difference of LED or LED string, improves LED driving problems that electrical property difference causes by this and reduces power consumption when driving.In addition, when application technological means of the present invention drives the LED of three kinds of coloured light of RGB, can make its luminous intensity more even, reach better white light effect.
For above-mentioned feature and advantage of the present invention can be become apparent, preferred embodiment cited below particularly, and cooperate appended graphicly, be described in detail below.
Description of drawings
Fig. 1 is drive circuit figure according to an embodiment of the invention.
Fig. 2 is the driving voltage and the current relationship figure of load unit according to an embodiment of the invention.
Embodiment
Fig. 1 is drive circuit figure according to an embodiment of the invention, and Fig. 1 comprises that drive circuit and LED go here and there formed load unit 152,154,156.Drive circuit comprises voltage-adjusting unit 110, control unit 120, switch element 130 and current source 140, and wherein switch element 130 comprises switch control unit 132 and switch 134,135 and 136.134,135,136 on switch can utilize transistor to form, for example be the bipolar junction transistor of NPN, PNP (Bipolar Junction Transistor, be called for short BJT) or NMOS (Nchannel metal oxide semiconductor transistor, be called for short NMOS) PMOS transistors such as (Pchannel metalo xide semiconductor transistor are called for short PMOS).152,154,156 of load units for example are the LED strings in the module backlight.
When switch control unit 132 actuating switchs 134, the magnitude of voltage that 110 of voltage-adjusting units can be adjusted driving voltage VOUT is with corresponding to load unit 152.The rest may be inferred, and when switch control unit 132 actuating switchs 135, the magnitude of voltage that 110 of voltage-adjusting units can be adjusted driving voltage VOUT is with corresponding to load unit 154.When switch control unit 132 actuating switchs 136, the magnitude of voltage that 110 of voltage-adjusting units can be adjusted driving voltage VOUT is with corresponding to load unit 156.When load unit 152,154,156 receives the driving voltage VOUT that is enough to its inner LED string of conducting, promptly can produce the conducting electric current, its inner LED promptly can produce corresponding luminous intensity (light luminance).
Owing to the string of the LED in the load unit 152-156 may produce different conducting voltage (lighting the required voltage of LED string) because of processing procedure difference, therefore can preestablish the magnitude of voltage of corresponding driving voltage VOUT, and cooperation switch control unit 132, make corresponding load unit 152-156 obtain suitable driving voltage VOUT respectively driving, and lighted in the sequential of correspondence.
The magnitude of voltage that control unit 120 is mainly used to controlling and driving voltage VOUT changes and the conducting sequential of switch 134,135,136, makes the driving voltage VOUT can be along with being switched on to the load unit 152,154 of current source 140 or 156 and corresponding its magnitude of voltage of adjusting.In other words, control unit 120 mainly is the work schedule that is used for controlling voltage-adjusting unit 110 and switch control unit 132, comes the corresponding LED string of lighting in the load unit 152,154,156 with corresponding actuating switch 134,135,136 with adjustment driving voltage VOUT.
The electric current I of the driving voltage VOUT and the load unit 152,154,156 of flowing through
152, I
154, I
156Between relation then please refer to Fig. 2, Fig. 2 is according to the driving voltage of the load unit of present embodiment and current relationship figure.In the present embodiment, suppose switch 134,135,136 respectively among time T 1, T2, the T3 by switch control unit 132 conductings.Owing to driving voltage VOUT can adjust along with the conducting sequential of switch 134,135,136.Therefore, the magnitude of voltage of driving voltage VOUT in time T 1, T2, T3 is respectively V1, V2, V3.When switch 134,135,136 conductings in regular turn, its corresponding load unit 152,154,156 promptly can produce the conducting electric current I in regular turn
152, I
154, I
156
As shown in Figure 2, load unit 152,154,156 receives different driving voltage VOUT respectively at time T 1, T2, T3, its conducting electric current I
152, I
154, I
156Current value be respectively I
R, I
G, I
BThe luminous intensity of the LED string in the load unit 152,154,156 is then by the conducting electric current I
152, I
154, I
156The magnitude of current determine.When the conducting electric current I
152, I
154, I
156When being zero, the corresponding LED string of expression is not lighted (conducting).Current value I during conducting
R, I
G, I
BThen the current value that is set by current source 140 is decided, and 140 of current sources are constant current source in the present embodiment, so current value I
R, I
G, I
BCan equate in fact.
When load unit 152,154,156 is represented the LED of three kinds of coloured light of RGB respectively,, then may produce the problem that differs luminous intensity inequality or start-up time, and then influence the white light quality of module backlight if use identical driving voltage VOUT to drive.Therefore, present embodiment adopts the driving voltage VOUT of adjustable to come driving LED, improves the backlight control problem that is caused because of the difference of LED own by this, also avoids because of using too high driving voltage to cause the problem of power dissipation simultaneously.
In addition, it should be noted that the load unit among Fig. 1 is not restricted to three, each load unit also can comprise a plurality of LED strings, and its indivedual LED strings also can be made up of one or more LED, and present embodiment is not limited.The magnitude of voltage of driving voltage VOUT does not exceed with voltage V1, V2, V3 yet, can be according to the design requirement adjustment.Moreover, voltage-adjusting unit 110 also is not restricted to one group with switch control unit 132 each load units that drive, also can drive many group load units simultaneously according to design requirement, its drive pattern is then as above-mentioned, equally can be according to different load output different driving voltage, the present technique field has knows the knowledgeable usually, knowing by inference easily via behind this example open, does not add tired stating at this.
In sum, the present invention utilizes adjustable driving voltage to come the driving LED string, and adjusts corresponding driving voltage according to the electrical property difference of indivedual LED strings, solves the driving problems that is caused because of LED conducting voltage difference by this.
Though the present invention with preferred embodiment openly as above; right its is not in order to limit the present invention; have in the technical field under any and know the knowledgeable usually; without departing from the spirit and scope of the present invention; when can doing a little change and retouching, so protection scope of the present invention is as the criterion when looking aforesaid the claim scope person of defining.
Claims (8)
1. the drive circuit of a light-emitting diode is used to drive a plurality of load units, it is characterized in that, each those load unit comprises at least one light-emitting diode, and the drive circuit of this light-emitting diode comprises:
One voltage-adjusting unit is in order to export the end of a driving voltage to those load units;
One switch element is electrically connected at respectively between the other end and a current source of those load units, in order to one in those load units are electrically connected to this current source; And
One control unit, be electrically connected at this voltage-adjusting unit and this switch element, wherein one first control signal exported according to this control unit of this voltage-adjusting unit is adjusted this driving voltage, one second those load units of control signal selectivity conducting that this switch element is exported according to this control unit one with this current source;
Wherein, when this switch element was electrically connected to this current source with one first load unit in those load units, the magnitude of voltage that this voltage-adjusting unit is adjusted this driving voltage was with corresponding to this first load unit.
2. as the drive circuit of claim 1 a described light-emitting diode, it is characterized in that, when this switch element was electrically connected to this current source with one second load unit in those load units, the magnitude of voltage that this voltage-adjusting unit is adjusted this driving voltage was with corresponding to this second load unit.
3. the drive circuit of light-emitting diode as claimed in claim 1, it is characterized in that, this switch element also is electrically connected to this current source with those load units in regular turn, and the magnitude of voltage that this voltage-adjusting unit is then adjusted this driving voltage in regular turn is with corresponding to one of those load units that electrically connected or those load units.
4. the drive circuit of light-emitting diode as claimed in claim 1 is characterized in that, this switch element comprises:
A plurality of switches are electrically connected at respectively between those load units and this current source; And
One switch control unit is electrically connected at those switches respectively, and according to this second control signal with those switches of selectivity conducting.
5. the drive circuit of light-emitting diode as claimed in claim 4 is characterized in that, those switches comprise N transistor npn npn or P transistor npn npn.
6. the drive circuit of light-emitting diode as claimed in claim 1 is characterized in that, this voltage-adjusting unit comprises a booster circuit or a reduction voltage circuit.
7. the drive circuit of light-emitting diode as claimed in claim 1 is characterized in that, this load unit comprises a light emitting diode string at least, and this light emitting diode string comprises a plurality of first light-emitting diodes that are one another in series.
8. the drive circuit of light-emitting diode as claimed in claim 1 is characterized in that, this current source is a constant current source.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009101663307A CN101998725A (en) | 2009-08-24 | 2009-08-24 | Drive circuit of light-emitting diode |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009101663307A CN101998725A (en) | 2009-08-24 | 2009-08-24 | Drive circuit of light-emitting diode |
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| CN101998725A true CN101998725A (en) | 2011-03-30 |
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| CN2009101663307A Pending CN101998725A (en) | 2009-08-24 | 2009-08-24 | Drive circuit of light-emitting diode |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102497695A (en) * | 2011-11-18 | 2012-06-13 | 上海晶丰明源半导体有限公司 | LED linear constant current control circuit and LED linear circuit |
| CN106504710A (en) * | 2017-01-04 | 2017-03-15 | 深圳市华星光电技术有限公司 | A kind of LED backlight drive circuit and liquid crystal display |
| CN108461068A (en) * | 2017-02-22 | 2018-08-28 | 瑞轩科技股份有限公司 | Back lighting device and its control method |
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| CN1766963A (en) * | 2004-10-27 | 2006-05-03 | 雅捷科技股份有限公司 | Parallel-connected type light-emitting diode driving device |
| CN101207958A (en) * | 2006-12-18 | 2008-06-25 | 广鹏科技股份有限公司 | Driving circuit and related driving method for providing feedback control and open-circuit protection |
| CN101409044A (en) * | 2007-10-08 | 2009-04-15 | 中华映管股份有限公司 | Backlight component and drive method thereof |
| CN101426312A (en) * | 2007-10-29 | 2009-05-06 | 中华映管股份有限公司 | Backlight device |
| EP2302706A1 (en) * | 2008-07-15 | 2011-03-30 | Sharp Kabushiki Kaisha | Light emitting element driving circuit |
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2009
- 2009-08-24 CN CN2009101663307A patent/CN101998725A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1766963A (en) * | 2004-10-27 | 2006-05-03 | 雅捷科技股份有限公司 | Parallel-connected type light-emitting diode driving device |
| CN101207958A (en) * | 2006-12-18 | 2008-06-25 | 广鹏科技股份有限公司 | Driving circuit and related driving method for providing feedback control and open-circuit protection |
| CN101409044A (en) * | 2007-10-08 | 2009-04-15 | 中华映管股份有限公司 | Backlight component and drive method thereof |
| CN101426312A (en) * | 2007-10-29 | 2009-05-06 | 中华映管股份有限公司 | Backlight device |
| EP2302706A1 (en) * | 2008-07-15 | 2011-03-30 | Sharp Kabushiki Kaisha | Light emitting element driving circuit |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102497695A (en) * | 2011-11-18 | 2012-06-13 | 上海晶丰明源半导体有限公司 | LED linear constant current control circuit and LED linear circuit |
| CN106504710A (en) * | 2017-01-04 | 2017-03-15 | 深圳市华星光电技术有限公司 | A kind of LED backlight drive circuit and liquid crystal display |
| US10446090B2 (en) | 2017-01-04 | 2019-10-15 | Shenzhen China Star Optoelectronics Technology Co., Ltd | LED backlight driving circuit and liquid crystal display |
| CN108461068A (en) * | 2017-02-22 | 2018-08-28 | 瑞轩科技股份有限公司 | Back lighting device and its control method |
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Application publication date: 20110330 |