CN200950192Y - Backlight protective circuit for LCD - Google Patents
Backlight protective circuit for LCD Download PDFInfo
- Publication number
- CN200950192Y CN200950192Y CN 200520120230 CN200520120230U CN200950192Y CN 200950192 Y CN200950192 Y CN 200950192Y CN 200520120230 CN200520120230 CN 200520120230 CN 200520120230 U CN200520120230 U CN 200520120230U CN 200950192 Y CN200950192 Y CN 200950192Y
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- transistor
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- lcd backlight
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- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
Abstract
The utility model relates to a LCD backlight protection circuit, comprising a first testing circuit, a second testing circuit, a pulse-width modulation integrated circuit, a control switch, a first input circuit and a second input circuit. The first and second testing circuits respectively comprise a first and second backlight strip-lamps and a first and secondary test output ends. When the first and second test circuits detect that the backlight strip-lamp is an open circuit, the first and second circuits respectively generate a low voltage signal to the first and second test output ends. The first input circuit comprises a diode and a transistor, the cathode of the diode is connected to the grid electrode of the transistor, and the anode of the diode is taken as a first input end and connected to the first test output end. The second input circuit comprises an input resistance, one end of the input resistance is connected to the current sampling end, and the other end of the input resistance is taken as a second input end and connected to the second test output end. The LCD backlight protection circuit is characterized in a simple structure and low cost.
Description
[technical field]
The utility model relates to a kind of backlight protection circuit, particularly a kind of backlight liquid crystal display holding circuit that is used for.
[background technology]
Therefore characteristics such as that LCD has is frivolous, low power consumption and radiation are few are widely used in fields such as mobile computer, mobile phone and portable computer.Because the liquid crystal molecule itself in the LCD is not luminous; therefore LCD needs to show by the luminous image of realizing of a module backlight; common module backlight comprises the pulse-width modulation integrated circuit of a plurality of backlight lamp tubes and these a plurality of backlight lamp tube working currents of adjusting; when a backlight lamp tube job occurs unexpected; when causing the output load open circuit of this pulse-width modulation integrated circuit, this pulse-width modulation integrated circuit needs a backlight protection circuit that it is quit work.
Please refer to Fig. 1, is a kind of synoptic diagram of prior art LCD backlight holding circuit 100.This LCD backlight holding circuit 100 comprises four backlight open detection circuit 110, an input circuit 130, a pulse-width modulation integrated circuit 150 and a gauge tap 170.
This backlight open detection circuit 110 comprises that a backlight lamp tube 111 and detects output terminal 112.
This input circuit 130 comprises four diodes 131, four biasing resistors 132, four filter capacitors 135, a first transistor 1331, a transistor seconds 1332, one the 3rd transistor 1333, one the 4th transistor 1334 and four biasing resistors 132.The grounded drain of this first transistor 1331, the source electrode of this first transistor 1331 is electrically connected to the drain electrode of this transistor seconds 1332, the source electrode of this transistor seconds 1332 is electrically connected to the drain electrode of the 3rd transistor 1333, the source electrode of the 3rd transistor 1333 is electrically connected to the drain electrode of the 4th transistor 1334, and the source electrode of the 4th transistor 1334 is output terminals of this input circuit 130.The grid of the 4th transistor 1334 is by a biasing resistor 132 and a filter capacitor 135 ground connection in parallel, and the negative electricity of a diode 131 is connected to the grid of this first transistor 1331, and it is an input end of this input circuit 130 that the positive pole of this diode 131 is done.The grid syndeton of this first transistor 1331, transistor seconds 1332 and the 3rd transistor 1333 is connected identical with the grid of the 4th transistor 1334.The positive pole of these four diodes 131 is respectively as four input ends of this input circuit 130.
This pulse-width modulation integrated circuit 150 comprises a current sample end 151, and when pulling into low-voltage under these current sample end 151 quilts, this pulse-width modulation integrated circuit 150 quits work.
This gauge tap 170 comprises one the 5th transistor 171 and a current-limiting resistance 172, the grounded drain of the 5th transistor 171, the source electrode of the 5th transistor 171 is electrically connected to the grid of current sample end 151, the five transistors 171 of this pulse-width modulation integrated circuit 150 and the source electrode of the 4th transistor 1334 is electrically connected to a power supply (pin of pulse-width modulation integrated circuit 150) by this current-limiting resistance 172 simultaneously.
During operate as normal, the detection output terminal 112 of these four backlight open detection circuit 110 is all exported four high voltage signals.These four high voltage signals make this first transistor 1331, transistor seconds 1332, the 3rd transistor 1333 and the 4th transistor 1334 all open through these four diodes 131, then pull into low-voltage under the source electrode of the 4th transistor 1334 quilt, so the 5th transistor 171 is closed.
When any backlight open detection circuit 110 detects backlight lamp tube 111 are whens open circuit, the detection output terminal 112 of this backlight open detection circuit 110 produces a low voltage signal, this low voltage signal makes this make one of this first transistor 1331, transistor seconds 1332, the 3rd transistor 1333 and the 4th transistor 1334 close through this diode 131, because the source electrode of the grid of the 5th transistor 171 and the 4th transistor 1334 is electrically connected to a power supply by this current-limiting resistance 172 simultaneously.Therefore the grid of the 5th transistor 171 is high voltages; then the 5th transistor 171 is opened; so be connected under these current sample end 151 quilts on the 5th transistor 171 source electrodes and pull into low-voltage, this pulse-width modulation integrated circuit 150 quits work, and realizes the backlight open-circuit defencive function.
In this LCD backlight holding circuit 100; this input circuit 130 comprises 1331,1332,1333,1,334 four transistors of first, second, third, fourth transistor; the structure more complicated; when if the backlight lamp tube that adopts increases; the transistor that this input circuit 130 comprises also needs corresponding increase, further increases cost.
[utility model content]
In order to solve LCD backlight holding circuit structure more complicated of the prior art, cost problem of higher, be necessary to provide a kind of LCD backlight holding circuit simple in structure, lower-cost.
A kind of LCD backlight holding circuit comprises first testing circuit, second testing circuit, a pulse-width modulation integrated circuit, a gauge tap, one first input circuit and one second input circuit.This first testing circuit comprises that one first backlight lamp tube and one first detects output terminal.This second testing circuit comprises that one second backlight lamp tube and one second detects output terminal.It is that open circuit the time produces a low voltage signal respectively and detects output terminal to this first, second that this first, second testing circuit detects backlight lamp tube.This pulse-width modulation integrated circuit comprises a current sample end, and when pulling into low-voltage under this current sample end quilt, this pulse-width modulation integrated circuit quits work.This first input circuit comprises a diode, a biasing resistor, a filter capacitor, a transistor, this transistor drain ground connection, this transistorized source electrode is electrically connected to this current sample end via this gauge tap, this transistorized source electrode also is electrically connected to a power supply, this transistorized grid is by this biasing resistor and this filter capacitor ground connection in parallel, the negative electricity of this diode is connected to the grid of this transistor seconds, and the positive pole of this diode is as first input end and be connected to this first detection output terminal.This second input circuit comprises an input resistance, and an end of this input resistance is connected to this current sample end, and the other end of this input resistance is as second input end and be connected to this second detection output terminal.
Compared to prior art, when adopting the fluorescent tube of same quantity, the input circuit in the above-mentioned LCD backlight holding circuit only comprises half transistor of fluorescent tube quantity.Therefore, this LCD backlight holding circuit is simple in structure, and cost is lower.
[description of drawings]
Fig. 1 is a kind of synoptic diagram of prior art LCD backlight holding circuit.
Fig. 2 is the synoptic diagram of the utility model LCD backlight holding circuit first embodiment.
Fig. 3 is the synoptic diagram of the utility model LCD backlight holding circuit second embodiment.
[embodiment]
Please refer to Fig. 2, is the synoptic diagram of the utility model LCD backlight holding circuit first embodiment.This LCD backlight holding circuit 200 comprises first testing circuit 210, second testing circuit 220, a pulse-width modulation integrated circuit 250, a gauge tap 270, one first input circuit 230 and one second input circuit 240.
This first testing circuit 210 comprises that one first backlight lamp tube 211 and one first detects output terminal 212, and when this first testing circuit 210 detected this first backlight lamp tube 211 and is open circuit, it first detected output terminal 212 and produce a low voltage signal.
This second testing circuit 220 comprises that one second backlight lamp tube 221 and one second detects output terminal 222, and when this second testing circuit 220 detected this second backlight lamp tube 221 and is open circuit, it detected output terminal 222 and produces a low voltage signal.
This pulse-width modulation integrated circuit 250 comprises a current sample end 251, and when pulling into low-voltage under these current sample end 251 quilts, this pulse-width modulation integrated circuit 250 quits work.
This gauge tap 270 comprises a first transistor 271, the grounded drain of this first transistor 271, the source electrode of this first transistor 271 is electrically connected to the current sample end 251 of this pulse-width modulation integrated circuit 250, and the grid of this first transistor 271 is that the current-limiting resistance 272 of 100K Ω is electrically connected to a 5V power supply (one of pulse-width modulation integrated circuit 250 pin) by a resistance.
This first input circuit 230 comprises a diode 231, a biasing resistor 232, a filter capacitor 233, a transistor seconds 234.The grounded drain of this transistor seconds 234, the source electrode of this transistor seconds 234 is electrically connected to the grid of this first transistor 271, and the grid of transistor seconds 234 is by these biasing resistor 232 and these filter capacitor 233 ground connection in parallel.The negative electricity of this diode 231 is connected to the grid of this transistor seconds 234, and the positive pole of this diode 231 is as first input end and be connected to this first detection output terminal 212.
This second input circuit 240 comprises an input resistance 241, and an end of this input resistance 241 is connected to this current sample end 251, and its other end is as second input end and be connected to this second detection input end 222.
This diode 231 is that the employing model is the diode of S N4148 in the present embodiment.The resistance value of this input resistance is 3.9K Ω.The resistance value of this biasing resistor is 1M Ω.This first and second transistor is that the employing model is the transistor of 2N 7002, can certainly select the transistor of other alternative NPN or positive-negative-positive for use.This pulse-width modulation integrated circuit is that the employing model is the integrated circuit of OZ9910G.This backlight lamp tube the 211, the 221st, cold cathode ray tube.
During operate as normal, two of these two testing circuits 210,220 are detected output terminal 212,222 equal output HIGH voltage signals.A high voltage signal makes this transistor seconds 234 open by this diode 231, then pull into low-voltage under the grid of this first transistor 271 quilt, so this first transistor 271 is closed.Another high voltage signal offers this current sample end 251 of this pulse-width modulation integrated circuit 250 by this second input circuit 240.
When first testing circuit 210 detects backlight lamp tube 211 are whens open circuit, and this detects output terminal 212 and produces a low voltage signal.This low voltage signal can make this transistor seconds 234 close by this diode 231; because the grid of this first transistor 271 is electrically connected to a high-tension power supply; therefore this first transistor 271 is opened; so be connected under these current sample end 251 quilts on these the first transistor 271 source electrodes and pull into low-voltage; this pulse-width modulation integrated circuit 250 quits work, and realizes the backlight open-circuit defencive function.
When second testing circuit 220 detects backlight lamp tube 221 are whens open circuit, and this detects output terminal 222 and produces a low voltage signal.This low voltage signal directly pulls into low-voltage 251 times with the current sample end of this pulse-width modulation integrated circuit 250 by this second input circuit 240, and this pulse-width modulation integrated circuit 250 is quit work, and realizes the backlight open-circuit defencive function.
Compared to prior art, when adopting the backlight lamp tube of same quantity, the input circuit 230 in this LCD backlight holding circuit 200 only comprises half transistor 234 of backlight lamp tube 211,221 quantity.Therefore, this LCD backlight holding circuit 200 is simple in structure, and cost is lower.
Please refer to Fig. 3, is the synoptic diagram of the utility model LCD backlight holding circuit second embodiment.This LCD backlight holding circuit 300 comprises first testing circuit 310, second testing circuit 320, three testing circuit 380, the 4th testing circuit 390, a pulse-width modulation integrated circuit 350, a gauge tap 370, one first input circuit 330 and one second input circuit 340.
This first testing circuit 310 comprises that one first backlight lamp tube 311 and one first detects output terminal 312, and when this first testing circuit 310 detected this first backlight lamp tube 311 and is open circuit, it first detected output terminal 312 and produce a low voltage signal.
This second testing circuit 320 comprises that one second backlight lamp tube 321 and one second detects output terminal 322, and when this second testing circuit 320 detected this second backlight lamp tube 321 and is open circuit, it second detected output terminal 322 and produce a low voltage signal.
This three testing circuit 380 comprises that one the 3rd backlight lamp tube 381 and the 3rd detects output terminal 382, and when this three testing circuit 380 detected the 3rd backlight lamp tube 381 and is open circuit, it the 3rd detected output terminal 382 and produce a low voltage signal.
The 4th testing circuit 390 comprises when one the 4th backlight lamp tube 391 and the 4th detects output terminal 392, the four testing circuits 390 and detects the 4th backlight lamp tube 391 and be open circuit, and it the 4th detects output terminal 392 and produce a low voltage signal.
This pulse-width modulation integrated circuit 350 comprises a current sample end 351, and when pulling into low-voltage under these current sample end 351 quilts, this pulse-width modulation integrated circuit 350 quits work.
This gauge tap 370 comprises a first transistor 371, the grounded drain of this first transistor 371, the source electrode of this first transistor 371 is electrically connected to the current sample end 351 of this pulse-width modulation integrated circuit 350, and the grid of this first transistor 371 is electrically connected to a 5V power supply (one of pulse-width modulation integrated circuit 350 pin) by a current-limiting resistance 372.
This first input circuit 330 comprises two diodes 331, two biasing resistors 332, two filter capacitors 333, a transistor seconds 334 and one the 3rd transistors 336.The grounded drain of the 3rd transistor 336, the source electrode of the 3rd transistor 336 is electrically connected to the drain electrode of this transistor seconds 334, and the source electrode of this transistor seconds 334 is electrically connected to the grid of this first transistor 371.By a biasing resistor 332 and a filter capacitor 333 ground connection in parallel, the grid of this second, third transistor 334,336 is electrically connected the negative pole of a diode 331 respectively to the grid of second, third transistor 334,336 respectively.The positive pole of one diode 331 is as first input end and be electrically connected to this first detection output terminal 312, and the positive pole of another diode 331 is as the 3rd input end and be electrically connected to this second detection output terminal 322.
This second input circuit 340 comprises two input resistances 341,342, and an end of this input resistance 341 is connected to this current sample end 351, and the other end of this input resistance 341 is as the 3rd input end and be electrically connected to the 3rd detection input end 382.One end of this input resistance 342 is connected to this current sample end 351, and the other end of this input resistance 342 is as four-input terminal and be electrically connected to the 4th detection input end 392.
During operate as normal, four of this four testing circuit 310,320,380,390 are detected output terminal 312,322,382,392 equal output HIGH voltage signals.Two high voltage signals make this second, third transistor 334,336 open by this diode 231, then pull into low-voltage under the grid of this first transistor 371 quilt, so this first transistor 371 are closed.Other two high voltage signals offer this current sample end 351 of this pulse-width modulation integrated circuit 350 by this second input circuit 340.
When first, second testing circuit 310,320 detects backlight lamp tube the 311, the 321st, during open circuit, this detection output terminal 312,322 produces a low voltage signal respectively.This low voltage signal can make this transistor seconds 334 or the 3rd transistor 336 close by this diode 331, because the grid of this first transistor 371 is electrically connected to a high-tension power supply, therefore this first transistor 371 is opened, so be connected under these current sample end 351 quilts on these the first transistor 371 source electrodes and pull into low-voltage, this pulse-width modulation integrated circuit 350 quits work.
When the 3rd, the 4th testing circuit 380,390 detects backlight lamp tube the 381, the 391st, during open circuit, this detection output terminal 382,392 produces a low voltage signal respectively.This low voltage signal directly pulls into low-voltage 351 times with the current sample end of this pulse-width modulation integrated circuit 350 by this second input circuit 340, and this pulse-width modulation integrated circuit 350 is quit work, and realizes the backlight open-circuit defencive function.
Compared to prior art, when adopting the backlight lamp tube of same quantity, the input circuit 330 in this LCD backlight holding circuit 300 only comprises half transistor 334,336 of backlight lamp tube 311,321,381,391 quantity.Therefore, LCD backlight holding circuit of the present utility model 300 is simple in structure, and cost is lower.
Claims (10)
1. LCD backlight holding circuit comprises:
One first testing circuit, it comprises that one first backlight lamp tube and one first detects output terminal, this testing circuit detects and produces a low voltage signal when backlight lamp tube is open circuit to this first detection output terminal;
One second testing circuit, it comprises that one second backlight lamp tube and one second detects output terminal, this testing circuit detects and produces a low voltage signal when backlight lamp tube is open circuit to this second detection output terminal;
One pulse-width modulation integrated circuit, it comprises a current sample end, when pulling into low-voltage under this current sample end quilt, this pulse-width modulation integrated circuit quits work;
One gauge tap;
One first input circuit, this first input circuit comprises a diode, a biasing resistor, a filter capacitor, a transistor, this transistor drain ground connection, this transistorized source electrode is electrically connected to this current sample end via this gauge tap, this transistorized source electrode also is electrically connected to a power supply, this transistorized grid is by this biasing resistor and this filter capacitor ground connection in parallel, the negative electricity of this diode is connected to the grid of this transistor seconds, and the positive pole of this diode is as first input end and be connected to this first detection output terminal;
It is characterized in that: this LCD backlight holding circuit further comprises one second input circuit; this second input circuit comprises an input resistance; one end of this input resistance is connected to this current sample end, and the other end of this input resistance is as second input end and be connected to this second detection output terminal.
2. as the LCD backlight holding circuit of claim 1, it is characterized in that: this LCD backlight holding circuit further comprises:
One three testing circuit, it comprises that one the 3rd backlight lamp tube and the 3rd detects output terminal, this testing circuit detects and produces a low voltage signal when backlight lamp tube is open circuit to the 3rd detection output terminal;
One the 4th testing circuit, it comprises that one the 4th backlight lamp tube and the 4th detects output terminal, this testing circuit detects and produces a low voltage signal when backlight lamp tube is open circuit to the 4th detection output terminal;
One the 3rd input circuit, the 3rd input circuit comprises a diode, a biasing resistor, a filter capacitor and another transistor, this another transistorized grid passes through this biasing resistor and this filter capacitor ground connection in parallel, the negative electricity of this diode is connected to the grid of this first transistor, the positive pole of this diode is as the 3rd input end and be connected to the 3rd and detect output terminal, and the transistor drain of this first input circuit is successively by this another transistorized source electrode and grounded drain; And
One the 4th input circuit, it comprises an input resistance, and an end of this input resistance is connected to this current sample end, and the other end of this input resistance is as four-input terminal and be connected to the 4th detection output terminal.
3. as claim 1 or 2 s' LCD backlight holding circuit; it is characterized in that: this gauge tap is a switching transistor; the grounded drain of this switching transistor; the source electrode of this switching transistor is electrically connected to the current sample end of this pulse-width modulation integrated circuit, and the grid of this switching transistor is electrically connected to the transistorized source electrode of this first input circuit.
4. as the LCD backlight holding circuit of claim 3, it is characterized in that: this LCD backlight holding circuit further comprises a current-limiting resistance, and the grid of this switching transistor is electrically connected to this power supply by this current-limiting resistance.
5. as the LCD backlight holding circuit of claim 3, it is characterized in that: the resistance value of this current-limiting resistance is 100K Ω.
6. as claim 1 or 2 s' LCD backlight holding circuit, it is characterized in that: this supply voltage is the direct supply of a 5V.
7. as claim 1 or 2 s' LCD backlight holding circuit, it is characterized in that: this first and second transistor is a NPN transistor.
8. as claim 1 or 2 s' LCD backlight holding circuit, it is characterized in that: this first and second transistor is a PNP transistor.
9. as claim 1 or 2 s' LCD backlight holding circuit, it is characterized in that: the resistance value of this input resistance is 3.9K Ω.
10. as claim 1 or 2 s' LCD backlight holding circuit, it is characterized in that: the resistance value of this biasing resistor is 1M Ω.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200520120230 CN200950192Y (en) | 2005-12-08 | 2005-12-08 | Backlight protective circuit for LCD |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200520120230 CN200950192Y (en) | 2005-12-08 | 2005-12-08 | Backlight protective circuit for LCD |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN200950192Y true CN200950192Y (en) | 2007-09-19 |
Family
ID=38892734
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 200520120230 Expired - Lifetime CN200950192Y (en) | 2005-12-08 | 2005-12-08 | Backlight protective circuit for LCD |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN200950192Y (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101409048B (en) * | 2007-10-10 | 2010-09-29 | 群康科技(深圳)有限公司 | Backlight protection circuit |
| CN101969732A (en) * | 2010-08-17 | 2011-02-09 | 友达光电股份有限公司 | Protection circuit for backlight module of liquid crystal display |
| TWI386889B (en) * | 2007-12-21 | 2013-02-21 | Chimei Innolux Corp | Backlight open-load protection circuit |
| CN103383839A (en) * | 2012-05-04 | 2013-11-06 | 美格纳半导体有限公司 | Light emitting diode driver apparatus |
-
2005
- 2005-12-08 CN CN 200520120230 patent/CN200950192Y/en not_active Expired - Lifetime
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101409048B (en) * | 2007-10-10 | 2010-09-29 | 群康科技(深圳)有限公司 | Backlight protection circuit |
| US8018701B2 (en) | 2007-10-10 | 2011-09-13 | Innocom Technology (Shenzhen) Co., Ltd. | Backlight control circuit with protecting circuit |
| TWI386889B (en) * | 2007-12-21 | 2013-02-21 | Chimei Innolux Corp | Backlight open-load protection circuit |
| CN101969732A (en) * | 2010-08-17 | 2011-02-09 | 友达光电股份有限公司 | Protection circuit for backlight module of liquid crystal display |
| CN101969732B (en) * | 2010-08-17 | 2014-04-30 | 友达光电股份有限公司 | Protection circuit for backlight module of liquid crystal display |
| CN103383839A (en) * | 2012-05-04 | 2013-11-06 | 美格纳半导体有限公司 | Light emitting diode driver apparatus |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| AV01 | Patent right actively abandoned |
Effective date of abandoning: 20090311 |
|
| C25 | Abandonment of patent right or utility model to avoid double patenting |