CN1687984A - Liquid crystal display and LED driving circuit thereof - Google Patents
Liquid crystal display and LED driving circuit thereof Download PDFInfo
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- CN1687984A CN1687984A CN 200510076594 CN200510076594A CN1687984A CN 1687984 A CN1687984 A CN 1687984A CN 200510076594 CN200510076594 CN 200510076594 CN 200510076594 A CN200510076594 A CN 200510076594A CN 1687984 A CN1687984 A CN 1687984A
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Abstract
The invention is a liquid crystal display (LCD), comprising a light-emitting diode (LED) drive circuit and a LED module. And the LED module comprises many LEDs, and the LED circuit comprises transformer, rectifier circuit and filter circuit, wherein the transformer outputs an AC voltage, the rectifier circuit and the filter circuit rectify and filter the AC, respectively, and then output the needed DC voltage reference for driving these LEDs.
Description
[technical field]
The invention relates to a kind of LCD, and particularly relevant for a kind of light emitting diode (Light Emitting Diode) driving circuit.
[prior art]
Along with the size of LCD constantly increases, for example large-sized LCD TV, the required brightness that provides of its backlight module also must with increase, just can keep the image quality of picture.Therefore (Light Emitting Diode, on behalf of employed LED quantity, backlight module LED) (hereinafter light emitting diode common name LED) must increase, and just can provide enough brightness to keep the image quality of picture for using light emitting diode.
So, be subject to the framework of traditional led drive circuit, for example DC-to-DC converter (DC to DC converter), power switch and associated electrical part, the for example proof voltage of inductance and diode and anti-electric current restriction, perhaps the lifting/voltage reducing restriction that caused of DC-to-DC converter architectural characteristic all will cause the restricted number of driving LED.So, just must use the LEDs of many group DC-to-DC converter, or reach in the mode of parallel connection LED simultaneously and drive the more purpose of plurality of LEDs with driving some out of the ordinary.But above-mentioned way will have current imbalance and cost problem of higher.So, how to solve the driving LED restricted number made because of the output voltage of DC-to-dc conversion and the problem of current imbalance, and reduce the cost of LED driving circuit, be that industry is badly in need of the problem that solves at present.
[summary of the invention]
In view of this, purpose of the present invention is providing a kind of LCD and LED driving circuit thereof exactly, can solve the problem that the output voltage deficiency of traditional DC-to-DC converter is caused, and the problem of current imbalance when driving many light emitting diodes.
According to purpose of the present invention, a kind of LCD is proposed, it comprise a plurality of light emitting diodes (Light Emitting Diode, LED) and LED driving circuit.These a little light-emitting diodes pipings form the light emitting diode of a series connection at least.Driving circuit system is in order to drive this a little light emitting diodes, and it comprises transformer and rectification circuit.Transformer is in order to output AC voltage.Rectification circuit is in order to receive alternating voltage and to export first DC voltage according to this, to drive this a little light emitting diodes.
According to another object of the present invention, a kind of LCD is proposed, it is to comprise backlight module and LED driving circuit.Backlight module system comprises a plurality of first light emitting diodes and a plurality of second light emitting diode.A little therewith second light emitting diodes of these a little first light emitting diodes required light source when the liquid crystal display displays image to be provided.Driving circuit system is shinny in order to drive these a little first light emitting diodes and those second light emitting diodes, and it comprises transformer, first rectification circuit and second rectification circuit.The secondary side-line of transformer comprises the first coiling group and one second coiling group.The first coiling group is in order to export first alternating voltage.The second coiling group is in order to export second alternating voltage.First rectification circuit is in order to receive first alternating voltage and to export first DC voltage according to this, to drive this a little first light emitting diodes.Second rectification circuit is in order to receive second alternating voltage and to export second DC voltage according to this, to drive this a little second light emitting diodes.
According to a further object of the present invention, a kind of LED driving circuit is proposed, it is in order to drive many light emitting diodes.This driving circuit comprises transformer and rectification circuit.Transformer is in order to output AC voltage.Rectification circuit is in order to receive alternating voltage and to export first DC voltage according to this, to drive this a little light emitting diodes.Wherein, this light emitting diode required light source when the liquid crystal display displays image to be provided.
For above-mentioned purpose of the present invention, feature and advantage can be become apparent, a preferred embodiment cited below particularly, and cooperate appended graphicly, be described in detail below:
[description of drawings]
Fig. 1 is the synoptic diagram of the LCD of first embodiment of the invention.
Fig. 2 is another routine synoptic diagram of LCD.
Fig. 3 is the synoptic diagram of the LCD of second embodiment of the invention.
[embodiment]
The invention provides a kind of LCD and LED driving circuit thereof, can solve under the large scale liquid crystal display, problem that the output voltage deficiency of traditional DC-to-DC converter is caused and the problem of current imbalance when driving many light emitting diodes.
First embodiment
Please refer to Fig. 1, it is the synoptic diagram of the LCD of first embodiment of the invention.LCD 100 comprises LED driving circuit 102 and light-emitting diode (LED) module 104.This light-emitting diode (LED) module 104 for example has N LEDs (1) ~ LED (N), and N is a positive integer.LED driving circuit 102 comprises transformer 106, rectification circuit 108 and filtering circuit 110.This N LEDs is for example for producing the light emitting diode of white light, and it is used for backlight module and is electrically connected to each other in the mode of serial or parallel connection.Wherein, being painted by example with the series connection, is serial or parallel connection but do not limit these a little LED electric connection mode to each other in present embodiment, and does not also limit glow color or the quantity of LED.For example during N=60, these 60 LEDs (1) ~ (60) can be divided into two strings, after promptly 30 LEDs (1) ~ (30) are electrically connected to each other with series system again with other 30 LED (31) ~ LED (60) parallel connections that are connected with series system equally.
Above-mentioned backlight module required light source (backlight module is not plotted among Fig. 1) when LCD 100 show images to be provided.Transformer 106 is in order to output AC voltage AC.Rectification circuit 108 and filtering circuit 110 are exported and are driven the luminous required DC voltage position standard of this N LEDs in order to after alternating voltage AC rectification and the filtering.
In other words, alternating voltage AC converts the first DC voltage DC1 to through rectification circuit 108.This rectification circuit 108 can for entirely/semibridge system rectification framework or other circuit pattern.So, the kenel that in present embodiment, does not limit rectification circuit 108 why, as long as can according to this alternating voltage AC be converted to DC voltage (the first direct current DC1).This first DC voltage DC1 produces the second more smooth-going DC voltage DC2 of potential change again via after filtering circuit 110 filtering.It is luminous that this second direct current DC2 will drive this N LEDs according to this.Filtering circuit 110 for example comprises a series connection inductance L capacitor C in parallel with (inductance L and capacitor C are not plotted among Fig. 1).
Because traditional DC-to-DC converter (DC to DC converter), stepup transformer (Boost converter) for example, because of the restriction of electronic package with the architectural characteristic of itself, its DC voltage position standard of exporting has certain limitation and can't be too high.Therefore, under traditional practice, must take to allow LED electrically connect in parallel in order to drive more LED.So, the mode that electrically connects in parallel will cause the uneven problem of luminosity of every string LED.Perhaps, to drive under the shape condition of more LED corresponding to large-sized LCD, must take by the LED of more groups of stepup transformers with driving some out of the ordinary, so this kind practice also can cause the uneven problem of LED luminosity to each other of respectively organizing stepup transformer and being driven.
And the present invention's design will provide the more LED quantity required DC voltage position standard of alternating voltage AC to drive corresponding to desire of high voltage level compared with under above-mentioned traditional practice.That is, utilize the lifting/voltage reducing characteristic of transformer 106 and the combination of rectification circuit 108 and filtering circuit 110, will no longer be subject to the limit of boosting of stepup transformer (Boost converter).So, when the size of LCD constantly increases, to such an extent as to when the quantity of LED must increase, can produce the required DC voltage position standard of these a little LED of driving, the second promptly above-mentioned DC voltage DC2 by the lifting/voltage reducing characteristic of transformer 106 and the combination of rectification circuit 108 and filtering circuit 110.In other words, these a little LED will no longer be subject to the restriction of the output voltage position standard of stepup transformer (Boost converter), and the LED of the greater number of can connecting is to reach required brightness.And, make the luminosity that makes these a little LED more even by the electric connection mode of series connection.
In sum, present embodiment not only can solve the problem of driving voltage deficiency and current imbalance when driving plurality of LEDs more.More because, one group of LED quantity that LED driving circuit 102 is driven, promptly comparable many group LED that DC-to-DC converter drove are more.So, use of the usage quantity minimizing of the LED driving circuit 102 of present embodiment because of the usage quantity and the control IC thereof of DC-to-DC converter, can reduce the manufacturing cost of LED driving circuit 102.
In addition, the alternating voltage that above-mentioned transformer 106 is received can by the direct current voltage process power switch switching generation that is provided in the LCD 100 or directly by civil power, for example AC110 provides.Why the alternating voltage source that received of limiting transformer 106 does not drive the required alternating voltage AC of these a little LED as long as can produce according to this in present embodiment.And under the capacity permission of transformer 106, transformer 106 more can have many group second siding rings.Every group of second siding ring is for example via after separately the rectification and filtering circuit, to drive corresponding LED modules.Please refer to Fig. 2, it is another routine synoptic diagram of LCD.LCD 100 more can comprise two light-emitting diode (LED) modules, is respectively first light-emitting diode (LED) module 104 (1) and second light-emitting diode (LED) module 104 (2).First light-emitting diode (LED) module 104 (1) has many LED that electrically connect with series system respectively with second light-emitting diode (LED) module 104 (2).The secondary side of transformer 106 comprises the first coiling group 202 and the second coiling group 204.The first siding ring 200 of transformer 106 for example receives the AC110 volt.The second siding ring aspect, the first coiling group 202 is in order to export the first alternating voltage AC1.The second coiling group 204 is in order to export the second alternating voltage AC2.The first alternating voltage AC1 drives first light-emitting diode (LED) module 104 (1) according to this via behind first rectification circuit 108 (1) and first filtering circuit 110 (1).First filtering circuit 110 (1) for example is made up of first inductance L 1 and first capacitor C 1, and second filtering circuit 110 (2) for example is made up of second inductance L 2 and second capacitor C 2.In like manner, drive the type of drive of second light-emitting diode (LED) module 104 (2) in this just no longer stating more.But what need pay special attention to is, when the LED quantity of second light-emitting diode (LED) module 104 (2) and first light-emitting diode (LED) module 104 (1) is identical, have identical in fact coiling number and all be around on the identical iron core by the first coiling group 202 and the second coiling group 204, make the drive current of second light-emitting diode (LED) module 104 (2) and the drive current of first light-emitting diode (LED) module 104 (1) will reach balance, promptly two light-emitting diode (LED) modules 104 (1) are more average with 104 (2) luminosity.
Second embodiment
Except that this, the white light of backlight module more can produce by the light emitting diode mixed light of RGB (RGB) three looks.Transformer more can provide the required alternating voltage of led module that drives these three groups of different colours.Please refer to Fig. 3, it is the synoptic diagram of the LCD of second embodiment of the invention.LCD 100 ' similarly comprises LED driving circuit 102 ' and three groups of light-emitting diode (LED) modules 104 '.Three groups of light-emitting diode (LED) modules 104 ' are respectively first light-emitting diode (LED) module 104 ' (1), second light-emitting diode (LED) module 104 ' (2) and the 3rd light-emitting diode (LED) module 104 ' (3).First light-emitting diode (LED) module 104 ' (1) has a plurality of first LEDs 1, for example is the light emitting diode of ruddiness.Second light-emitting diode (LED) module 104 ' (2) has a plurality of second LEDs 2, for example is the light emitting diode of green glow.The 3rd light-emitting diode (LED) module 104 ' (3) has a plurality of the 3rd LEDs 3, for example is the light emitting diode of blue light.Wherein, these a little first LEDs 1, second LED 2 and the 3rd LED 3 can be looked its luminous intensity or actual design demand, and distinctly have identical or different number.
LED driving circuit 102 ' more comprises three rectification circuits 108 ' and filtering circuit 110 ', is respectively first rectification circuit 108 ' (1), second rectification circuit 108 ' (2) and the 3rd rectification circuit 108 ' (3) and first filtering circuit 110 ' (1), second filtering circuit 110 ' (2) and the 3rd filtering circuit 110 ' (3).The secondary side of transformer 106 ' comprises the first coiling group 202 ', the second coiling group 204 ' and the 3rd coiling group 206 '.The first siding ring 200 ' of transformer 106 ' for example receives the AC110 volt.The first coiling group 202 ' is in order to export the first alternating voltage AC1 '.The second coiling group 204 ' is in order to export the second alternating voltage AC2 '.The 3rd coiling group 206 ' is in order to export the 3rd alternating voltage AC3 '.
As above-mentioned operating principle, rectification circuit 108 ' and filtering circuit 110 ' are in order to after corresponding alternating voltage AC1 ' ~ AC3 ' rectification and the filtering, and output drives corresponding light-emitting diode (LED) module 104 ' luminous required DC voltage position standard.That is to say that each coiling group 202 ', 204 ' and 206 ' produces corresponding alternating voltage AC1 ' ~ AC3 ' corresponding to the required DC voltage position standard of each light-emitting diode (LED) module 104 ' (1) ~ 104 ' (3).For example corresponding to the quantity of first LED 1, produce the corresponding first required alternating voltage AC1 ' of these a little first LEDs 1 that drives by the first coiling group 202 '.
Identical with first embodiment, by the lifting/voltage reducing characteristic of transformer 106 ' and the combination of rectification circuit 108 ' and filtering circuit 110 ', to no longer be subject to the limit of boosting of stepup transformer (Boostconverter), and producing the required DC voltage position standard of LED quantity that desire drives, the mode that every string LED can be connected electrically connects.Mode by series connection electrically connects, and will make that the luminosity of each light-emitting diode (LED) module 104 ' (1) ~ 104 ' (3) is more even.
Utilize LCD of the present invention or LED driving circuit, on reality is used, the visual actual design demand or the luminous intensity of light emitting diode itself, even and can be used to drive several, hundreds of LED of dozens of; And these LED electrical relation to each other can be series connection or a plurality of series LED parallel with one another.
The LED driving circuit 102 ' of present embodiment in addition, under the design architecture that uses DC-to-DC converter, also can reduce the required control IC of DC-to-DC converter and the usage quantity of related electronic components, reach the manufacturing cost that reduces LED driving circuit 102 '.
Disclosed LCD of the above embodiment of the present invention and LED driving circuit thereof solve under the large scale liquid crystal display, the problem of the output voltage deficiency of DC-to-DC converter, and more can reduce the manufacturing cost of led drive circuit.
In sum; though the present invention discloses as above with many preferred embodiments; right its is not in order to limit the present invention; anyly have the knack of this skill person; without departing from the spirit and scope of the present invention; when can being used for a variety of modifications and variations, so protection scope of the present invention is as the criterion when looking accompanying the claim person of defining.
Claims (15)
1. LCD is to comprise:
A plurality of light emitting diodes (Light Emitting Diode, LED), those light-emitting diodes pipings form the light emitting diode of a series connection at least; And
One drive circuit is in order to driving those light emitting diodes, and this driving circuit comprises:
One transformer is in order to export an alternating voltage; And
One rectification circuit is in order to receive this alternating voltage and to export one first DC voltage according to this, to drive those light emitting diodes.
2. LCD according to claim 1 is characterized in that, this driving circuit more comprises:
One filtering circuit is in order to receive this first DC voltage and to export one second DC voltage according to this, to drive those light emitting diodes.
3. LCD according to claim 1 is characterized in that, those light-emitting diodes pipings form a plurality of series connection light emitting diodes parallel with one another.
4. LCD is to comprise:
One backlight module is to comprise:
A plurality of first light emitting diodes and a plurality of second light emitting diode, those first light emitting diodes and those second light emitting diodes required light source when this liquid crystal display displays image to be provided; And
One drive circuit is in order to driving those first light emitting diodes and those second light emitting diodes are shinny, and this driving circuit comprises:
One transformer, the secondary side-line of this transformer comprises:
One first coiling group and one second coiling group, this first coiling group is in order to export one first alternating voltage, and this second coiling group is in order to export one second alternating voltage;
One first rectification circuit is in order to receive this first alternating voltage and to export one first DC voltage according to this, to drive those first light emitting diodes; And
One second rectification circuit is in order to receive this second alternating voltage and to export one second DC voltage according to this, to drive those second light emitting diodes.
5. LCD according to claim 4 is characterized in that, this driving circuit more comprises:
One first filtering circuit is in order to receive this first DC voltage and to export one the 3rd DC voltage according to this, to drive those first light emitting diodes; And
One second filtering circuit is in order to receive this second DC voltage and to export one the 4th DC voltage according to this, to drive those second light emitting diodes.
6. LCD according to claim 4 is characterized in that, this backlight module more comprises a plurality of the 3rd light emitting diodes, those the 3rd light emitting diodes required light source when this liquid crystal display displays image to be provided.
7. LCD according to claim 6 is characterized in that, the second siding ring of this transformer more comprises one the 3rd coiling group, and the 3rd coiling group is in order to export one the 3rd alternating current, and this driving circuit more comprises:
One the 3rd rectification circuit is in order to receive the 3rd alternating voltage and to export one the 5th DC voltage according to this; And
One the 3rd filtering circuit is in order to receive the 5th DC voltage and to export one the 6th DC voltage according to this, to drive those the 3rd light emitting diodes.
8. LCD according to claim 7 is characterized in that, this first rectification circuit, this second rectification circuit and the 3rd rectification circuit are full-bridge type rectification framework.
9. LCD according to claim 7 is characterized in that, this first rectification circuit, this second rectification circuit and the 3rd rectification circuit are semibridge system rectification framework.
10. LCD according to claim 7, it is characterized in that, those first light emitting diodes have identical color, those second light emitting diodes have same color, those the 3rd light emitting diodes have same color, but those first light emitting diodes, those second light emitting diodes are different with those the 3rd light emitting diodes color to each other.
11. LCD according to claim 7 is characterized in that, those first light emitting diodes, those second light emitting diodes have different numbers with those the 3rd light emitting diodes.
12. a LED driving circuit, in order to drive a plurality of light emitting diodes, this driving circuit comprises:
One transformer is in order to export an alternating voltage; And
One rectification circuit is in order to receive this alternating voltage and to export one first DC voltage according to this, to drive those light emitting diodes;
Wherein, those light emitting diodes required light source when the liquid crystal display displays image to be provided.
13. driving circuit according to claim 12 is characterized in that, this driving circuit more comprises:
One filtering circuit is in order to receive this first DC voltage and to export one second DC voltage according to this, to drive those light emitting diodes.
14. driving circuit according to claim 12 is characterized in that, this rectification circuit is a full-bridge type rectification framework.
15. driving circuit according to claim 12 is characterized in that, this rectification circuit is a semibridge system rectification framework.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510076594 CN1687984A (en) | 2005-06-09 | 2005-06-09 | Liquid crystal display and LED driving circuit thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510076594 CN1687984A (en) | 2005-06-09 | 2005-06-09 | Liquid crystal display and LED driving circuit thereof |
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| CN1687984A true CN1687984A (en) | 2005-10-26 |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101360379A (en) * | 2007-08-03 | 2009-02-04 | 奇美电子股份有限公司 | Light source protection circuit and application thereof in backlight module unit and LCD |
| CN102098853A (en) * | 2011-01-30 | 2011-06-15 | 成都芯源系统有限公司 | Light emitting element driving system, driving control circuit and driving method |
| CN101511136B (en) * | 2008-02-14 | 2013-02-20 | 台达电子工业股份有限公司 | Current balance power supply circuit of multi-group light-emitting diode |
| WO2014082363A1 (en) * | 2012-11-28 | 2014-06-05 | Feng Lin | Led drive circuit and led illumination device |
| CN104160785A (en) * | 2012-12-27 | 2014-11-19 | 冯林 | LED drive circuit and Led illumination device |
-
2005
- 2005-06-09 CN CN 200510076594 patent/CN1687984A/en active Pending
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101360379A (en) * | 2007-08-03 | 2009-02-04 | 奇美电子股份有限公司 | Light source protection circuit and application thereof in backlight module unit and LCD |
| CN101360379B (en) * | 2007-08-03 | 2013-05-08 | 奇美电子股份有限公司 | Light source protection circuit and application thereof in backlight module unit and LCD |
| CN101511136B (en) * | 2008-02-14 | 2013-02-20 | 台达电子工业股份有限公司 | Current balance power supply circuit of multi-group light-emitting diode |
| CN102098853A (en) * | 2011-01-30 | 2011-06-15 | 成都芯源系统有限公司 | Light emitting element driving system, driving control circuit and driving method |
| TWI474753B (en) * | 2011-01-30 | 2015-02-21 | Monolithic Power Systems Inc | Single power stage for led driver and other power supplies |
| CN102098853B (en) * | 2011-01-30 | 2015-04-15 | 成都芯源系统有限公司 | Light emitting element driving system, driving control circuit and driving method |
| WO2014082363A1 (en) * | 2012-11-28 | 2014-06-05 | Feng Lin | Led drive circuit and led illumination device |
| CN104160785A (en) * | 2012-12-27 | 2014-11-19 | 冯林 | LED drive circuit and Led illumination device |
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