CN102496905B - High-voltage open-circuited protection circuit of LCD (Liquid Crystal Display) screen - Google Patents
High-voltage open-circuited protection circuit of LCD (Liquid Crystal Display) screen Download PDFInfo
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- CN102496905B CN102496905B CN201110403627.8A CN201110403627A CN102496905B CN 102496905 B CN102496905 B CN 102496905B CN 201110403627 A CN201110403627 A CN 201110403627A CN 102496905 B CN102496905 B CN 102496905B
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Abstract
The invention discloses a high-voltage open-circuited protection circuit of an LCD (Liquid Crystal Display) screen. The high-voltage open-circuited protection circuit comprises a control chip U1, a high-voltage detection circuit (1), a frequency limiting circuit (2), a delay circuit (3) and a high-voltage bilateral open-circuited rapid protection circuit (4), wherein two paths of high-voltage output ends HV1 and HV2 in the high-voltage detection circuit (1) are connected with a backlight lamp tube on the LCD screen; when any one of the output ends HV1 and the HV2 is open-circuited, the frequency limiting circuit (2) and the delaying circuit (3) are triggered to work, so that the open-circuited high-voltage output end outputs protection voltage with a set size range and controllable hold-up time; and when the output ends HV1 and HV2 are open-circuited simultaneously, the high-voltage bilateral open-circuited rapid protection circuit (4) and the frequency limiting circuit (2) are triggered to work, so that the output ends HV1 and HV2 output limiting voltage, and the LCD screen is protected by auto poweroff. The high voltage open-circuited protection circuit disclosed by the invention has the advantages of greatly-reduced circuit cost, fewer elements and components and no need for control software; meanwhile, the stability, the safety and the reliability of the system are also remarkably improved.
Description
Technical field
The present invention relates to the high-pressure open-circuit protective circuit of video field.
Background technology
Existing open circuit protective circuit, adopts MCU(single-chip microcomputer)+scheme of IC SG3525 controlled.Such circuit shortcoming is: cost is too high, and integrated circuit original paper is too many, and circuit hardware and software is in conjunction with more complicated, fail safe, and reliability is low.
Summary of the invention
The object of the invention is to provide simple in structure; with low cost; safety; reliable and stable LCD screen high-pressure open-circuit protective circuit; meeting while opening single channel high pressure; there is voltage swing, the controlled circuit of holding time, and be in the time opening two-way high pressure, there is the protective circuit that voltage is controlled, can close immediately High voltage output.
A kind of LCD screen high-pressure open-circuit protective circuit provided by the invention, comprise control chip U1, high-voltage detecting circuit (1), frequency limitation circuit (2), delay circuit (3), the rapid protective circuit of the bilateral open circuit of high pressure (4), HV1 in described high-voltage detecting circuit (1), HV2 two-way high-voltage output end connects the backlight lamp tube on LCD screen, work as HV1, when in HV2, any road output is opened a way, trigger rate limiting circuit (2), delay circuit (3) work, make high-voltage output end output prescribed level scope and the controlled protection voltage of holding time of described open circuit, work as HV1, when HV2 two-way output is opened a way, trigger the rapid protective circuit of the bilateral open circuit of high pressure (4) and frequency limitation circuit (2) work simultaneously, make high-voltage output end HV1, HV2 export-restriction voltage, and automatic shutdown protection LCD screen.
Further, the PIN2 pin of described control chip U1 (number 2 pin) rate of connections limiting circuit (2), be the FREQUENCY CONTROL pin of described LCD screen high-pressure open-circuit protective circuit, can change the operating frequency of described LCD screen high-pressure open-circuit protective circuit by changing the resistance to earth of this pin;
The PIN3 pin of described control chip U1 (number 3 pin) is protection pin, and when this pin voltage is greater than 1V, while being less than 2V, driving is closed; Below voltage drops to 0.6V time, drive and can again trigger; The PIN3 pin of described control chip U1 is connected to respectively described delay circuit (3) and the rapid protective circuit of the bilateral open circuit of described high pressure (4).
In the time that this pin voltage is more than or equal to 2V, driving is closed, and circuit is locked, and automatic shutdown protection LCD screen.Even if voltage drops to below 0.6V, drive also do not trigger, only have when the power supply of control chip U1 resets again just can de-preservation.
Further, described high-voltage detecting circuit (1) comprises capacitor C 7, C14, resistance R 27, R26, two diode D8; Capacitor C 7, resistance R 26, resistance R 27, capacitor C 14 are connected successively, capacitor C 7 one end are HV1, capacitor C 14 one end are HV2, tie point ground connection between resistance R 26, R27, the positive pole of first diode D8 connects tie point between capacitor C 7, resistance R 26, negative pole connects frequency limitation circuit (2) and delay circuit (3), and the positive pole of second diode D8 connects tie point between capacitor C 14, resistance R 27, and negative pole connects frequency limitation circuit (2) and delay circuit (3).
Further, the RC charging delay circuit that described delay circuit (3) is made up of resistance R 25, R24 and capacitor C 13.
LCD screen high-pressure open-circuit protective circuit of the present invention; both the list open circuit that had met LCD screen running parameter demand is held time and voltage; again can be in the time that LCD shields the actual two ends of backlight lamp tube open circuit; limiting voltage in certain voltage and rapidly shutdown, has been prevented to open circuit voltage is too high high-tension transformer to be punctured or on fire.Described circuit cost reduces greatly, and structure is simplified, and components and parts are few, there is no single-chip microcomputer, does not need to control software.The stability of simultaneity factor, fail safe, reliability also significantly improves.
Brief description of the drawings
Fig. 1 is the LCD screen high-pressure open-circuit protective circuit structural representation that the embodiment of the present invention provides.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, the present invention is described in further detail.
As shown in Figure 1, a kind of LCD screen high-pressure open-circuit protective circuit that the embodiment of the present invention provides, comprise control chip U1 (such as model is UCC25600), high-voltage detecting circuit (1), frequency limitation circuit (2), delay circuit (3), the rapid protective circuit of the bilateral open circuit of high pressure (4), HV1 in described high-voltage detecting circuit (1), HV2 two-way high-voltage output end connects the backlight lamp tube on LCD screen, work as HV1, when in HV2, any road output is opened a way, trigger rate limiting circuit (2), delay circuit (3) work, make high-voltage output end output prescribed level scope and the controlled protection voltage of holding time of described open circuit, work as HV1, when HV2 two-way output is opened a way, trigger the rapid protective circuit of the bilateral open circuit of high pressure (4) and frequency limitation circuit (2) work simultaneously, make high-voltage output end HV1, HV2 export-restriction voltage, and automatic shutdown protection LCD screen.
The PIN2 pin rate of connections limiting circuit (2) of described control chip U1, be the FREQUENCY CONTROL pin of described LCD screen high-pressure open-circuit protective circuit, can change the operating frequency of described LCD screen high-pressure open-circuit protective circuit by changing the resistance to earth of this pin;
The PIN3 pin of described control chip U1 is protection pin, and when this pin voltage is greater than 1V, while being less than 2V, driving is closed; Below voltage drops to 0.6V time, drive and can again trigger.
In the time that this pin voltage is more than or equal to 2V, driving is closed, and circuit is locked, and automatic shutdown protection LCD screen.Even if voltage drops to below 0.6V, drive also do not trigger, only have when the power supply of control chip U1 resets again just can de-preservation.
Described high-voltage detecting circuit (1) comprises capacitor C 7, C14, resistance R 27, R26, two diode D8; Capacitor C 7, resistance R 26, resistance R 27, capacitor C 14 are connected successively, capacitor C 7 one end are HV1, capacitor C 14 one end are HV2, tie point ground connection between resistance R 26, R27, the positive pole of first diode D8 connects tie point between capacitor C 7, resistance R 26, negative pole connects frequency limitation circuit (2) and delay circuit (3), and the positive pole of second diode D8 connects tie point between capacitor C 14, resistance R 27, and negative pole connects frequency limitation circuit (2) and delay circuit (3).
Further, the RC charging delay circuit that described delay circuit (3) is made up of resistance R 25, R24 and capacitor C 13.
The LCD screen high-pressure open-circuit protective circuit course of work of the present invention is specific as follows: high-voltage detecting circuit detects HV1, the crest voltage of HV2 two-way output high pressure, in the time of any road output open circuit, the open circuit other road of voltage ratio, Na road is high, by diode, D8 is sampled, the voltage of sampling is leaded up to resistance R 25, R13 is connected with frequency limitation circuit, work as R13, point pressure handle Q3 conducting of R12, R11 has electric current to pass through, in figure, the operating frequency of LCD screen chip will be drawn high, because circuit working is in the perceptual region of RLC series resonance, inductance plays a major role, in the time that frequency raises, the output voltage of the high-pressure side of described open circuit can be limited within the specific limits.D8 is also by R25 simultaneously, and R24 is connected with C13, R25, and R24 and C13 composition RC charging delay circuit, C13 is connected with the PIN3 of IC, in the time that the voltage of C13 is charged to 1V, arrives the deboost of chip, and LCD screen chip drives is turn-offed, but protection is not locked.When described circuit just reaches Liao Kai mono-road high pressure, what require according to LCD screen running parameter has certain controlled open circuit voltage, and has certain controlled holding time.
When at the actual two ends of LCD screen backlight lamp tube open circuit, this LCD screen high-pressure open-circuit protective circuit can be shut down limiting voltage in certain voltage and rapidly, has prevented from that open circuit voltage is too high high-tension transformer to be punctured or on fire.The rapid protective circuit of open circuit as bilateral in Fig. 1 mesohigh (seeing block diagram 4 circuit), along with VS1, VS2 voltage raises, flow through R20, the electric current of R29 increases, voltage on R20 and R29 also increases, the anode (tie point of D6 and R18) of D6, voltage also raises, in the time reaching certain voltage, pass through R17, R28 dividing potential drop, Q4 conducting, also conducting of Q5 after Q4 conducting, and form controllable silicon latching circuit, after Q5 conducting, 5V voltage passes through Q5, D5, R19 is connected to the PIN3 of IC, PIN3 voltage is approximately 4.3V, when this pin voltage is during higher than 2V, drive immediately and turn-off, and locked.So just reached while opening two-way high pressure, circuit is the function of protection rapidly.
LCD screen high-pressure open-circuit protective circuit of the present invention; both the list open circuit that had met LCD screen running parameter demand is held time and voltage; again can be in the time that LCD shields the actual two ends of backlight lamp tube open circuit; limiting voltage in certain voltage and rapidly shutdown, has been prevented to open circuit voltage is too high high-tension transformer to be punctured or on fire.Described circuit cost reduces greatly, and structure is simplified, and components and parts are few, there is no single-chip microcomputer, does not need to control software.The stability of simultaneity factor, fail safe, reliability also significantly improves.
Claims (2)
1. a LCD screen high-pressure open-circuit protective circuit, it is characterized in that, comprise control chip U1, high-voltage detecting circuit (1), frequency limitation circuit (2), delay circuit (3) and the rapid protective circuit of the bilateral open circuit of high pressure (4), HV1 in described high-voltage detecting circuit (1), HV2 two-way high-voltage output end connects the backlight lamp tube on LCD screen, work as HV1, when in HV2, any road output is opened a way, trigger rate limiting circuit (2), delay circuit (3) work, make high-voltage output end output prescribed level scope and the controlled protection voltage of holding time of described open circuit, work as HV1, when HV2 two-way output is opened a way, trigger the rapid protective circuit of the bilateral open circuit of high pressure (4) and frequency limitation circuit (2) work simultaneously, make high-voltage output end HV1, HV2 export-restriction voltage, and automatic shutdown protection LCD screen,
The PIN2 pin rate of connections limiting circuit (2) of described control chip U1, be the FREQUENCY CONTROL pin of described LCD screen high-pressure open-circuit protective circuit, can change the operating frequency of described LCD screen high-pressure open-circuit protective circuit by changing the resistance to earth of this pin;
The PIN3 pin of described control chip U1 is protection pin, and when this pin voltage is greater than 1V, while being less than 2V, driving is closed; Below voltage drops to 0.6V time, drive and can again trigger; In the time that this pin voltage is more than or equal to 2V, driving is closed, and circuit is locked, and automatic shutdown protection LCD screen; The PIN3 pin of described control chip U1 is connected to respectively described delay circuit (3) and the rapid protective circuit of the bilateral open circuit of described high pressure (4);
Described high-voltage detecting circuit (1) comprises capacitor C 7, capacitor C 14, resistance R 27, resistance R 26 and two diode D8; Described two diode D8 comprise the first diode and the second diode; Capacitor C 7, resistance R 26, resistance R 27, capacitor C 14 are connected successively, capacitor C 7 one end are HV1, capacitor C 14 one end are HV2, tie point ground connection between resistance R 26, resistance R 27, the positive pole of the first diode connects tie point between capacitor C 7, resistance R 26, negative pole connects frequency limitation circuit (2) and delay circuit (3), and the positive pole of the second diode connects tie point between capacitor C 14, resistance R 27, and negative pole connects frequency limitation circuit (2) and delay circuit (3).
2. LCD shields high-pressure open-circuit protective circuit according to claim 1, it is characterized in that, the RC charging delay circuit that described delay circuit (3) is made up of resistance R 25, resistance R 24 and capacitor C 13.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110403627.8A CN102496905B (en) | 2011-12-07 | 2011-12-07 | High-voltage open-circuited protection circuit of LCD (Liquid Crystal Display) screen |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110403627.8A CN102496905B (en) | 2011-12-07 | 2011-12-07 | High-voltage open-circuited protection circuit of LCD (Liquid Crystal Display) screen |
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| Publication Number | Publication Date |
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| CN102496905A CN102496905A (en) | 2012-06-13 |
| CN102496905B true CN102496905B (en) | 2014-10-22 |
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| CN201110403627.8A Active CN102496905B (en) | 2011-12-07 | 2011-12-07 | High-voltage open-circuited protection circuit of LCD (Liquid Crystal Display) screen |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108418404B (en) * | 2018-03-29 | 2024-01-30 | 深圳茂硕电子科技有限公司 | Circuit capable of controlling intermittent point entering and method thereof |
Citations (3)
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| CN1798468A (en) * | 2004-12-30 | 2006-07-05 | 鸿富锦精密工业（深圳）有限公司 | Lighting circuit with protection of open circuit for gaseous discharge lamp |
| CN1881038A (en) * | 2005-06-17 | 2006-12-20 | 群康科技(深圳)有限公司 | Backlight open circuit protection circuit |
| CN1953632B (en) * | 2005-10-20 | 2010-12-08 | 鸿富锦精密工业（深圳）有限公司 | Opening protective circuit |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100401100B1 (en) * | 2000-11-22 | 2003-10-10 | 삼성전기주식회사 | Back-light inverter of LCD |
| JP2005011681A (en) * | 2003-06-19 | 2005-01-13 | Yokogawa Electric Corp | Cold-cathode tube driving device |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1798468A (en) * | 2004-12-30 | 2006-07-05 | 鸿富锦精密工业（深圳）有限公司 | Lighting circuit with protection of open circuit for gaseous discharge lamp |
| CN1881038A (en) * | 2005-06-17 | 2006-12-20 | 群康科技(深圳)有限公司 | Backlight open circuit protection circuit |
| CN1953632B (en) * | 2005-10-20 | 2010-12-08 | 鸿富锦精密工业（深圳）有限公司 | Opening protective circuit |
Non-Patent Citations (2)
| Title |
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| 基于UCC25600的LLC谐振变换器设计;杨帆等;《电源技术》;20100630;第134卷(第6期);589-591,613 * |
| 杨帆等.基于UCC25600的LLC谐振变换器设计.《电源技术》.2010,第134卷(第6期),589-591,613. |
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Address after: Xue Cheng Ke Zhu Road Guangzhou City, Guangdong province 510663 science No. 192 Applicant after: Guangzhou CVT Electronics Technology Co., Ltd. Address before: Xue Cheng Ke Zhu Road Guangzhou City, Guangdong province 510663 science No. 192 Applicant before: Guangzhou Shiyuan Electronics Technology Co., Ltd. |
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