CN100443994C - Backlight open circuit protection circuit - Google Patents
Backlight open circuit protection circuit Download PDFInfo
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- CN100443994C CN100443994C CNB2005100353930A CN200510035393A CN100443994C CN 100443994 C CN100443994 C CN 100443994C CN B2005100353930 A CNB2005100353930 A CN B2005100353930A CN 200510035393 A CN200510035393 A CN 200510035393A CN 100443994 C CN100443994 C CN 100443994C
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- backlight open
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Abstract
The present invention relates to a backlight open circuit protection circuit which comprises at least two backlight open circuit detecting circuit, an input circuit, a pulse width modulation integrated circuit and a control switch, wherein the input circuit comprises at least two diodes, at least two voltage-dividing resistors, a second transistor and a bias resistor, positive electrodes of the diodes are electrically connected to a grid electrode of the second transistor, and a drain electrode of the second transistor is earthed; a source electrode of the second transistor is used as an output terminal of the input circuit, and negative electrodes of the diodes are used as multiple input terminals of the input circuit after respectively connected to one voltage-dividing resistor in series. When any one backlight open circuit detecting circuit detects that a backlight lamp tube is open circuit, a low-voltage signal is generated, and the low-voltage signal passes through the input circuit to open the control switch so as to downward pull an electric current sampling terminal of the pulse width modulation circuit to low voltage to stop the pulse width modulation integrated circuit from working. The backlight open circuit protection circuit of the present invention has simpler structure.
Description
[technical field]
The present invention relates to a kind of backlight open circuit protection circuit, particularly a kind of backlight liquid crystal display open loop protection circuit that is used for.
[background technology]
Therefore characteristics such as LCD has frivolous, and low power consumption and radiation are few are widely used in fields such as monitor, LCD TV, 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 open circuit protection circuit that it is quit work.
Please refer to Fig. 1, be a kind of synoptic diagram of prior art backlight open circuit protection circuit 100.This backlight open circuit protection 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 the output terminal 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 the positive pole of this diode 131 is as an input end of this input circuit 130.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 this current sample end 151 was drawn to low-voltage, this pulse-width modulation integrated circuit 150 quit 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 the source electrode of the 4th transistor 1334 by drop-down be low-voltage, so the 5th transistor 171 is closed.
When any backlight open detection circuit 110 detects backlight lamp tube 111 for 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 a high voltage; then the 5th transistor 171 is opened; drawn and be low-voltage so be connected this current sample end 151 on the 5th transistor 171 source electrodes, this pulse-width modulation integrated circuit 150 quits work, and realizes the backlight open-circuit defencive function.
In this backlight open circuit protection 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.
[summary of the invention]
In order to solve backlight open circuit protection circuit texture ratio of the prior art, be necessary to provide a kind of backlight open circuit protection circuit simple in structure than complicated problems.
The disclosed a kind of backlight open circuit protection circuit of better embodiment of the present invention comprises at least two backlight open detection circuit; one input circuit; an one pulse-width modulation integrated circuit and a gauge tap; this backlight open detection circuit comprises that a backlight lamp tube and detects output terminal; this input circuit comprises at least two diodes; at least two divider resistances; one transistor seconds; one biasing resistor; the positive pole of these two diodes and this two transistorized grid all are electrically connected to a power supply by this biasing resistor; the grounded drain of this transistor seconds; the source electrode of this transistor seconds is the output terminal of this input circuit; and be electrically connected to this power supply by a current-limiting resistance; the negative pole of these two diodes is connected respectively behind the divider resistance as a plurality of input ends of this input circuit; each input end all is electrically connected to this detection output terminal; this pulse-width modulation integrated circuit comprises a current sample end; when this current sample end is drawn to low-voltage; this pulse-width modulation integrated circuit quits work; this gauge tap comprises a first transistor; 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, and the grid of this first transistor is electrically connected to the output terminal of this power supply and this input circuit simultaneously.
Compared to prior art; input circuit in the above-mentioned backlight open circuit protection circuit only comprises two transistors; and the input circuit in the prior art backlight open circuit protection circuit comprises four transistors, and therefore, the gauge tap of backlight open circuit protection circuit of the present invention is more simple in structure than prior art.
[description of drawings]
Fig. 1 is the circuit diagram of the backlight open circuit protection circuit of prior art.
Fig. 2 is the synoptic diagram of the disclosed a kind of backlight open circuit protection circuit of the present invention's one better embodiment.
[embodiment]
Please refer to Fig. 2, be the synoptic diagram of the disclosed a kind of backlight open circuit protection circuit 200 of the present invention's one better embodiment.This backlight open circuit protection circuit 200 comprises a plurality of backlight open detection circuit 210, an input circuit 230, a pulse-width modulation integrated circuit 250 and a gauge tap 270.This backlight open detection circuit 210 comprises that a backlight lamp tube 211 and detects output terminal 212.This input circuit 230 comprises a plurality of diodes 231, a plurality of divider resistances 232, one transistor seconds 233, one biasing resistor 234, the grid of the positive pole of these a plurality of diodes 231 and this transistor seconds 233 all is electrically connected to a power supply (pin of pulse-width modulation integrated circuit 250) by this biasing resistor 234, the grounded drain of this transistor seconds 233, the source electrode of this transistor seconds 233 is electrically connected to this power supply, the source electrode of this transistor seconds 233 is the output terminal of this input circuit 230, the negative pole of these a plurality of diodes 231 is connected a divider resistance 232 respectively afterwards as a plurality of input ends of this input circuit 230, and each input end of input circuit 230 all is electrically connected to this detection output terminal 212.This pulse-width modulation integrated circuit 250 comprises a current sample end 251, and when this current sample end 251 was drawn to low-voltage, this pulse-width modulation integrated circuit 250 quit work.This gauge tap 270 comprises a first transistor 271 and a current-limiting resistance 272, 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 source electrode of the grid of this first transistor 271 and this transistor seconds 233 is electrically connected to this power supply by this current-limiting resistance 272 simultaneously.
The model of this diode 231 is SN4148 in the present embodiment, the resistance of this resistance 232 is greater than 8K, preferred values is 10K, the resistance of this resistance 234 is 6.8K, the first and second transistorized models are 2N7002, can certainly select other alternative NPN or PNP transistor for use, the model of this pulse-width modulation integrated circuit is OZ9910G, and this backlight lamp tube 211 is a cold cathode ray tube.
During operate as normal, a plurality of high voltage signals of a plurality of detection output terminals 212 outputs of these a plurality of backlight open detection circuit 210.These a plurality of high voltage signals make this transistor seconds 233 open through these divider resistances 232 and diode 231, then the grid of this first transistor 271 by drop-down be low-voltage, so this first transistor 271 is closed.
When backlight 211 pipes damage; when any backlight open detection circuit 210 detects backlight lamp tube 211 for open circuit; this detects output terminal 212 and produces a low voltage signal; this low voltage signal makes this transistor seconds 233 close through this divider resistance 232 and diode 231; because it is high voltage that the grid of this first transistor 271 is electrically connected to a power supply; therefore this first transistor 271 is opened; so being connected this current sample end 251 on these the first transistor 271 source electrodes is drawn and is low-voltage; this pulse-width modulation integrated circuit 250 quits work, and realizes the backlight open-circuit defencive function.
Compared to prior art, the input electricity in the above-mentioned backlight open circuit protection circuit The road only comprises two transistors, even and this backlight open-circuit protection of increase backlight lamp tube Input circuit in the circuit need not increase number of transistors yet. Therefore, the present invention The gauge tap of backlight open circuit protection circuit more simple in structure than prior art.
Claims (8)
1. backlight open circuit protection circuit comprises:
At least two backlight open detection circuit, this backlight open detection circuit comprise that a backlight lamp tube and detects output terminal;
One input circuit comprises a plurality of input ends and an output terminal;
One pulse-width modulation integrated circuit, it comprises a current sample end, when this current sample end was drawn to low-voltage, this pulse-width modulation integrated circuit quit work;
One gauge tap, this gauge tap comprises a first transistor, 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 the output terminal of a power supply and this input circuit simultaneously;
It is characterized in that: this input circuit comprises at least two diodes, at least two divider resistances, one transistor seconds, one biasing resistor, the positive pole of these two diodes and the grid of this transistor seconds all are electrically connected to this power supply by this biasing resistor, the grounded drain of this transistor seconds, the source electrode of this transistor seconds is electrically connected to this power supply by a current-limiting resistance, the source electrode of this transistor seconds is the output terminal of this input circuit, it is electrically connected to this power supply, the negative pole of these two diodes is connected respectively behind the divider resistance as an input end of this input circuit, and each input end all is electrically connected to one and detects output terminal.
2. backlight open circuit protection circuit as claimed in claim 1 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.
3. backlight open circuit protection circuit as claimed in claim 1 is characterized in that: this first and second transistor is a NPN transistor.
4. backlight open circuit protection circuit as claimed in claim 1 is characterized in that: this first and second transistor is a PNP transistor.
5. backlight open circuit protection circuit as claimed in claim 1 is characterized in that: this first and second transistorized model is 2N7002.
6. backlight open circuit protection circuit as claimed in claim 1 is characterized in that: the model of this diode is SN4148.
7. backlight open circuit protection circuit as claimed in claim 5 is characterized in that: the resistance value of this divider resistance is greater than 8K, and the resistance value of this biasing resistor is 6.8K.
8. backlight open circuit protection circuit as claimed in claim 5 is characterized in that: the resistance value of this divider resistance is 10K, and the resistance value of this biasing resistor is 6.8K.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100353930A CN100443994C (en) | 2005-06-17 | 2005-06-17 | Backlight open circuit protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100353930A CN100443994C (en) | 2005-06-17 | 2005-06-17 | Backlight open circuit protection circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1881038A CN1881038A (en) | 2006-12-20 |
| CN100443994C true CN100443994C (en) | 2008-12-17 |
Family
ID=37519292
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2005100353930A Expired - Fee Related CN100443994C (en) | 2005-06-17 | 2005-06-17 | Backlight open circuit protection circuit |
Country Status (1)
| Country | Link |
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| CN (1) | CN100443994C (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1953632B (en) * | 2005-10-20 | 2010-12-08 | 鸿富锦精密工业（深圳）有限公司 | Opening protective circuit |
| CN101231412B (en) * | 2007-01-26 | 2011-12-07 | 群康科技(深圳)有限公司 | Backlight tube open circuit and short-circuit protection circuit |
| CN101399007B (en) * | 2007-09-28 | 2011-09-28 | 群康科技(深圳)有限公司 | Backlight open-circuit protective circuit |
| CN101409048B (en) * | 2007-10-10 | 2010-09-29 | 群康科技(深圳)有限公司 | Backlight 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 |
| CN102496905B (en) * | 2011-12-07 | 2014-10-22 | 广州视源电子科技股份有限公司 | High-voltage open-circuit protection circuit of LCD screen |
| KR101974218B1 (en) * | 2012-05-04 | 2019-05-02 | 매그나칩 반도체 유한회사 | Led driver apparatus |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6118221A (en) * | 1997-10-16 | 2000-09-12 | Tokin Corporation | Cold-cathode tube lighting circuit with protection circuit for piezoelectric transformer |
| CN1338813A (en) * | 2000-08-15 | 2002-03-06 | 株式会社村田制作所 | High voltage power supply with light emitting discharge tube for protection circuit and fault protecting circuits |
| CN1398503A (en) * | 2000-09-08 | 2003-02-19 | 皇家菲利浦电子有限公司 | System for overvoltage protection during pulse width modualtion dimming of LCD |
| CN1515940A (en) * | 2002-11-20 | 2004-07-28 | ���ǵ�����ʽ���� | Lamp driver anjd back light assemlby and liquid crystal display device containing it |
-
2005
- 2005-06-17 CN CNB2005100353930A patent/CN100443994C/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6118221A (en) * | 1997-10-16 | 2000-09-12 | Tokin Corporation | Cold-cathode tube lighting circuit with protection circuit for piezoelectric transformer |
| CN1338813A (en) * | 2000-08-15 | 2002-03-06 | 株式会社村田制作所 | High voltage power supply with light emitting discharge tube for protection circuit and fault protecting circuits |
| CN1398503A (en) * | 2000-09-08 | 2003-02-19 | 皇家菲利浦电子有限公司 | System for overvoltage protection during pulse width modualtion dimming of LCD |
| CN1515940A (en) * | 2002-11-20 | 2004-07-28 | ���ǵ�����ʽ���� | Lamp driver anjd back light assemlby and liquid crystal display device containing it |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1881038A (en) | 2006-12-20 |
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Granted publication date: 20081217 Termination date: 20170617 |
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| CF01 | Termination of patent right due to non-payment of annual fee |