CN2916689Y - Backlight protection circuit of liquid crystal display - Google Patents
Backlight protection circuit of liquid crystal display Download PDFInfo
- Publication number
- CN2916689Y CN2916689Y CN 200520119860 CN200520119860U CN2916689Y CN 2916689 Y CN2916689 Y CN 2916689Y CN 200520119860 CN200520119860 CN 200520119860 CN 200520119860 U CN200520119860 U CN 200520119860U CN 2916689 Y CN2916689 Y CN 2916689Y
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- backlight
- liquid crystal
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Abstract
The utility model relates to a backlight protection circuit of liquid crystal display, which comprises a first testing circuit, a second testing circuit , a pulse width adjusting integrated circuit, a control switch, a first input circuit, and a second input circuit. The first and second testing circuits comprise a first and second backlight light tubes and a first and second testing output ends. The first and second testing circuits, when the backlight tubes are cut off, generate a low voltage signal to the first and second testing output ends. The first input circuit comprises a diode, whose anode is taken as the first input end and connected with the first checking output end electrically. The second input circuit comprises an input resistance, whose one end is connected with the current sampling end, and another end is taken as the second input end and connected with the second testing end electrically. The backlight protection circuit is simple in structure and low in 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 advantages such as LCD has gently, approaches, power consumption is little are widely used in fields such as portable DVD player, PDA(Personal Digital Assistant), visual music player, mobile phone and notebook 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 backlight liquid crystal display holding circuit 100.This backlight liquid crystal display 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 first transistor 1331 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 transistor seconds 1332, the 3rd transistor 1333 and the 4th transistor 1334 is connected identical with the grid of this first transistor 1331.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 backlight liquid crystal display 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 backlight liquid crystal display holding circuit structure more complicated of the prior art, cost problem of higher, be necessary to provide a kind of backlight liquid crystal display holding circuit simple in structure, lower-cost.
One backlight liquid crystal display holding circuit comprises one first testing circuit, one 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 gauge tap comprises a first transistor, and the grounded drain of this first transistor, the source electrode of this first transistor are electrically connected to the current sample end of this pulse-width modulation integrated circuit, and the grid of this first transistor is electrically connected to a power supply simultaneously.This gauge tap comprises a first transistor, a transistor seconds and a biasing resistor, the grounded drain of this first transistor, the source electrode of this first transistor is electrically connected to the current sample end of this pulse-width modulation integrated circuit, the grid of this first transistor and the source electrode of this transistor seconds are electrically connected to a power supply simultaneously, the grounded drain of this transistor seconds, the grid of this transistor seconds is by this biasing resistor ground connection.This first input circuit comprises a diode and a divider resistance, the negative pole of this diode is electrically connected to the grid of this transistor seconds by this divider resistance, and the positive pole of this diode is as the first input end of this input circuit and be electrically connected to this and first detect 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 electrically connected to this second detection output terminal.
Compared to prior art, the input circuit in the above-mentioned backlight liquid crystal display holding circuit does not have transistor, only increases a transistor in the gauge tap.Even the increase backlight lamp tube, this backlight liquid crystal display holding circuit need not increase transistor yet.Therefore, this backlight liquid crystal display holding circuit is simple in structure.
[description of drawings]
Fig. 1 is a kind of synoptic diagram of prior art backlight liquid crystal display holding circuit.
Fig. 2 is the synoptic diagram of the utility model backlight liquid crystal display holding circuit first embodiment.
Fig. 3 is the synoptic diagram of the utility model backlight liquid crystal display holding circuit second embodiment.
[embodiment]
Please refer to Fig. 2, is the synoptic diagram of the utility model backlight liquid crystal display holding circuit first embodiment.This backlight liquid crystal display 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, a transistor seconds 272 1 current-limiting resistances 273 and a biasing resistor 274.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, the source electrode of the grid of this first transistor 271 and this transistor seconds 272 is electrically connected to a 5V power supply (pin of pulse-width modulation integrated circuit 250) by this current-limiting resistance 273 simultaneously, the grounded drain of this transistor seconds 272, the grid of this transistor seconds 272 is by these biasing resistor 274 ground connection.
This first input circuit 230 comprises a diode 231, a current-limiting resistance 232, a filter capacitor 233 and a divider resistance 234, the negative pole of this diode 231 is electrically connected to the grid of this transistor seconds 272 by this divider resistance 234, simultaneously, the negative pole of this diode 231 is by this current-limiting resistance 232 and filter capacitor 233 ground connection in parallel with it.The positive pole of this diode 231 is as the first input end of this input circuit 230 and be electrically connected to this and first detect 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 electrically connected to this second detection input end 222.
This diode 231 is that the employing model is the diode of SN4148 in the present embodiment.The resistance value of this input resistance is 3.9K.This first and second transistorized model is Q2N3904, can certainly select other alternative NPN or PNP transistor for use, and the model of this pulse-width modulation integrated circuit is OZ9910G, this backlight lamp tube the 211, the 221st, cold cathode ray tube.
During operate as normal, two of this two testing circuit 210,220 detects output terminal 212,222 equal output HIGH voltage signals, about 1.6V.Suitably select the resistance of this divider resistance 234 and this biasing resistor 274, make this high voltage signal drive these transistor seconds 272 saturation conductions 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 is applied to 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 the detection output terminal 212 of this testing circuit 210 produces a low voltage signal, about 0.067V.This low voltage signal can close this transistor seconds 272 by this diode 231; because the grid of this first transistor 271 is electrically connected to a 5V 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, about 0.067V.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.
Input circuit 230 in this backlight liquid crystal display holding circuit 200 does not have transistor, only increases a transistor in the gauge tap 270.Even and increasing backlight lamp tube, this backlight liquid crystal display holding circuit 200 need not increase transistor yet.Therefore, this backlight liquid crystal display holding circuit 200 is simple in structure, and cost is lower.
Please refer to Fig. 3, is the synoptic diagram of the utility model backlight liquid crystal display holding circuit second embodiment.This backlight liquid crystal display 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, a transistor seconds 372 1 current-limiting resistances 373 and a biasing resistor 374.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, the source electrode of the grid of this first transistor 371 and this transistor seconds 372 is electrically connected to a 5V power supply (pin of pulse-width modulation integrated circuit 350) by this current-limiting resistance 373 simultaneously, the grounded drain of this transistor seconds 372, the grid of this transistor seconds 372 is by these biasing resistor 374 ground connection.
This first input circuit 330 comprises two diodes 331, two current-limiting resistances 332, two filter capacitors 333 and two divider resistances 334.The negative pole of each diode 331 is electrically connected to the grid of this transistor seconds 372 by a divider resistance 334, and simultaneously, the negative pole of each diode 331 is by a current-limiting resistance 332 and a filter capacitor 333 ground connection in parallel with it.The positive pole of a 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, about 1.6V.Suitably select the resistance value of this divider resistance 334 and this biasing resistor 374, as: this divider resistance 334 is 10K Ω, this biasing resistor 374 is 1.5K Ω, this current-limiting resistance 332 is 1M Ω, make this two high voltages signal drive these transistor seconds 372 conductings by this diode 331, then pull into low-voltage under the grid of this first transistor 371 quilt, so this first transistor 371 is closed.Two high voltage signals of these detection output terminal 382,392 outputs are provided to 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 close this transistor seconds 372 by this diode 331, because the grid of this first transistor 371 is electrically connected to a 5V 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.
In addition; testing circuit 210,220,310,320,380,390 in the above-mentioned backlight liquid crystal display holding circuit 200,300 can also detect the state of backlight lamp tube 211,221,311,321,381,391 shorted to earths, and produces a low-voltage signal respectively to detecting output terminal 212,222,312,322,382,392.
Claims (10)
1. backlight liquid crystal display 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 first input circuit, this input circuit comprise a diode and a divider resistance, and the positive pole of this diode is as the first input end of this input circuit and be electrically connected to this and first detect output terminal;
One gauge tap;
It is characterized in that: this backlight protection circuit further comprises one second input circuit, it 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 electrically connected to this second detection output terminal;
This gauge tap comprises a first transistor, a transistor seconds and a biasing resistor, the grounded drain of this first transistor, the source electrode of this first transistor is electrically connected to the current sample end of this pulse-width modulation integrated circuit, the grid of this first transistor and the source electrode of this transistor seconds are electrically connected to a power supply simultaneously, the grounded drain of this transistor seconds, the grid of this transistor seconds is by this biasing resistor ground connection and be electrically connected to the negative pole of this diode by this divider resistance.
2. backlight liquid crystal display holding circuit as claimed in claim 1 is characterized in that: this backlight liquid crystal display 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, it comprises a diode and a divider resistance, the negative pole of this diode is electrically connected to the grid of this transistor seconds by this divider resistance, and the positive pole of this diode is as the 3rd input end of this input circuit and be electrically connected to the 3rd and detect output terminal; 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 electrically connected to the 4th detection output terminal.
3. backlight liquid crystal display holding circuit as claimed in claim 1 or 2 is characterized in that: the negative pole of this diode is by electric capacity and a current-limiting resistance ground connection in parallel with it.
4. backlight liquid crystal display holding circuit as claimed in claim 1 or 2 is characterized in that: further comprise a current-limiting resistance, the grid of this first transistor and the source electrode of transistor seconds all are electrically connected to this power supply by this current-limiting resistance.
5. backlight liquid crystal display holding circuit as claimed in claim 4 is characterized in that: the resistance value of this current-limiting resistance is 100K Ω.
6. backlight liquid crystal display holding circuit as claimed in claim 1 or 2 is characterized in that: this power supply is the direct supply of a 5V.
7. backlight liquid crystal display holding circuit as claimed in claim 1 or 2 is characterized in that: this first and second transistor is a NPN transistor.
8. backlight liquid crystal display holding circuit as claimed in claim 1 or 2 is characterized in that: this first and second transistor is a PNP transistor.
9. backlight liquid crystal display holding circuit as claimed in claim 1 or 2 is characterized in that: the resistance value of this input resistance is 3.9K Ω.
10. backlight liquid crystal display holding circuit as claimed in claim 1 or 2 is characterized in that: the resistance value of this divider resistance is 10K Ω, and the resistance value of this biasing resistor is 1.5K Ω.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200520119860 CN2916689Y (en) | 2005-12-02 | 2005-12-02 | Backlight protection circuit of liquid crystal display |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200520119860 CN2916689Y (en) | 2005-12-02 | 2005-12-02 | Backlight protection circuit of liquid crystal display |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN2916689Y true CN2916689Y (en) | 2007-06-27 |
Family
ID=38187605
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 200520119860 Expired - Fee Related CN2916689Y (en) | 2005-12-02 | 2005-12-02 | Backlight protection circuit of liquid crystal display |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN2916689Y (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101572987B (en) * | 2008-04-28 | 2012-10-24 | 群康科技(深圳)有限公司 | Backlight short circuit protection circuit |
| TWI386889B (en) * | 2007-12-21 | 2013-02-21 | Chimei Innolux Corp | Backlight open-load protection circuit |
| CN114999408A (en) * | 2022-06-17 | 2022-09-02 | 深圳市华星光电半导体显示技术有限公司 | Switch control circuit and backlight drive board |
-
2005
- 2005-12-02 CN CN 200520119860 patent/CN2916689Y/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI386889B (en) * | 2007-12-21 | 2013-02-21 | Chimei Innolux Corp | Backlight open-load protection circuit |
| CN101572987B (en) * | 2008-04-28 | 2012-10-24 | 群康科技(深圳)有限公司 | Backlight short circuit protection circuit |
| CN114999408A (en) * | 2022-06-17 | 2022-09-02 | 深圳市华星光电半导体显示技术有限公司 | Switch control circuit and backlight drive board |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20070627 Termination date: 20141202 |
|
| EXPY | Termination of patent right or utility model |