CN101604507B - LCD and backlight unit brightness automatic constant circuit thereof - Google Patents
LCD and backlight unit brightness automatic constant circuit thereof Download PDFInfo
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- CN101604507B CN101604507B CN2008100678264A CN200810067826A CN101604507B CN 101604507 B CN101604507 B CN 101604507B CN 2008100678264 A CN2008100678264 A CN 2008100678264A CN 200810067826 A CN200810067826 A CN 200810067826A CN 101604507 B CN101604507 B CN 101604507B
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Abstract
The invention relates to a liquid crystal display (LCD) and a backlight unit brightness automatic constant circuit thereof. The backlight unit brightness automatic constant circuit comprises a brightness setting circuit, a brightness detection circuit, a comparison circuit and a brightness control circuit, wherein the first input end of the comparison circuit is connected with the brightness detection circuit; the second input end of the comparison circuit is connected with the brightness setting circuit; and the output end of the comparison circuit is connected with the brightness control circuit which is connected with a backlight unit. The LCD can rapidly reach the set brightness after startup, maintains the constant brightness during the working process and effectively ensures the display picture quality for a long time because of the adopted backlight unit brightness automatic constant circuit which is also provided with a temperature detection and comprehension circuit for overcoming the temperature drift influence of an electronic circuit. Accordingly, the invention can better satisfy the user needs and be beneficial to the improvement of the working efficiency and quality of users.
Description
Technical field
The present invention relates to LCD, more particularly, relate to a kind of LCD with backlight unit brightness automatic constant circuit.
Background technology
The backlight liquid crystal display unit comprises luminotron, like cold cathode fluorescent tube (CCFL), light emitting diode (LED) etc.Usually the brightness regulation of display screen is to import the brightness signalization manually, increases or reduce the supply current of luminotron through control circuit, makes display screen reach required brightness.But because the characteristics of luminescence of luminotron is variation and unsettled, the brightness meeting is difference with the variation of temperature and service time, need after brightness changes, carry out manual adjustments once more.Defective on this performance, not too big for general application influence, but for the application of special industry, but possibly can not put up with.For example, when display is used for medical diagnosis, because brightness fluctuation, will influence picture display effect, the diagnosis to the doctor brings harmful effect possibly, sometimes even possibly cause mistaken diagnosis.
In addition, when start just or when energy saver mode is got back to normal manipulation mode, display brightness can't reach the brightness of setting at once. and usually need be through just reaching the brightness of setting after 10～30 minutes.In this brightness did not reach time of normal brightness of setting, display was that uncomfortable cooperation diagnosis is used.In order to increase work efficiency, the user hopes just can meet the requirements of brightness behind the display starting at once, rather than etc. last tens of minutes.
Summary of the invention
The technical matters that the present invention will solve is, brightness and the farm labourer that can not reach setting after the LCD start to prior art very soon makes the defective that brightness changes after the time, and a kind of backlight unit brightness automatic constant circuit is provided.
A kind of LCD with backlight unit brightness automatic constant circuit also is provided in addition.
The technical solution adopted for the present invention to solve the technical problems is: construct a kind of backlight unit brightness automatic constant circuit, comprise that the intednsity circuit and the brightness that link to each other with back light unit are provided with circuit; Also comprise;
Be used to detect the luminance detection circuit of back light unit luminosity;
Be used for comparator circuit that detected luminance signal and brightness settings are compared;
Wherein, the first input end of said comparator circuit links to each other with said luminance detection circuit, second input end is provided with circuit with said brightness and links to each other, and the output terminal of said comparator circuit links to each other with said intednsity circuit.
In backlight unit brightness automatic constant circuit of the present invention, also comprise the temperature sensing circuit that is used for the testing environment temperature, its output terminal is connected in first or second input end of said comparator circuit.
In backlight unit brightness automatic constant circuit of the present invention; Said intednsity circuit comprises control chip; Be connected with amplifying circuit between the output terminal of said comparator circuit and the said intednsity circuit, be used for the error signal of said comparator circuit output is carried out the matching processing and amplifying.
In backlight unit brightness automatic constant circuit of the present invention; Said back light unit comprises cathode fluorescent tube; Said intednsity circuit also comprises field effect transistor and transformer; The grid of wherein said field effect transistor links to each other with the output port of said control chip, drain electrode links to each other with power supply, source electrode links to each other with the elementary winding of transformer, and said cathode fluorescent tube links to each other with Secondary winding of transformer; The output signal of said control chip is a square wave driving signal, and its dutycycle changes with the variation of the error signal amplitude that receives.
In backlight unit brightness automatic constant circuit of the present invention; Said comparator circuit comprises first operational amplifier, and the first input end of said comparator circuit is that second input end of the inverting input of first operational amplifier, said comparator circuit is the in-phase input end of first operational amplifier; Be connected with feedback compensation electric capacity between the inverting input of said first operational amplifier and the output terminal.
In backlight unit brightness automatic constant circuit of the present invention, said amplifying circuit comprises second operational amplifier.
The present invention also constructs a kind of LCD, and comprise LCDs, be arranged at the back light unit at the display screen back side, and backlight unit brightness automatic constant circuit; Said backlight unit brightness automatic constant circuit comprises:
The brightness that is used to be provided with display brightness is provided with circuit;
Be used to detect the luminance detection circuit of back light unit luminosity;
Be used for comparator circuit that detected luminance signal and brightness settings are compared;
Be used to control the intednsity circuit of back light unit luminosity;
Wherein, The first input end of said comparator circuit links to each other with said luminance detection circuit, second input end is provided with circuit with said brightness and links to each other; The output terminal of said comparator circuit links to each other with said intednsity circuit, and said intednsity circuit links to each other with back light unit.
In LCD of the present invention, said backlight unit brightness automatic constant circuit also comprises the temperature sensing circuit that is used for the testing environment temperature, and its output terminal is connected in first or second input end of said comparator circuit.
In LCD of the present invention; Said intednsity circuit comprises control chip; Be connected with amplifying circuit between the output terminal of said comparator circuit and the said intednsity circuit, be used for the error signal of said comparator circuit output is carried out the matching processing and amplifying.
In LCD of the present invention; Said back light unit comprises cathode fluorescent tube; Said intednsity circuit also comprises field effect transistor and transformer; The grid of wherein said field effect transistor links to each other with the output port of said control chip, drain electrode links to each other with power supply, source electrode links to each other with the elementary winding of transformer, and said cathode fluorescent tube links to each other with Secondary winding of transformer; The output signal of said control chip is a square wave driving signal, and its dutycycle changes with the variation of the error signal amplitude that receives.
The backlight unit brightness automatic constant circuit of embodiment of the present invention and LCD; Has following beneficial effect: owing to adopted backlight unit brightness automatic constant circuit; LCD is reached after start very soon set brightness and keep constant luminance in the course of the work, guarantee the display frame quality for a long time effectively.
In addition, because backlight unit brightness automatic constant circuit also has temperature detection and compensating circuit, overcome the influence that the electronic circuit temperature is floated.
Therefore, embodiment of the present invention can be met consumers' demand better, helps improving user's work efficiency and quality.
Description of drawings
To combine accompanying drawing and embodiment that the present invention is described further below, in the accompanying drawing:
Fig. 1 is the LCDs of prior art and the schematic block diagram of intednsity circuit thereof;
Fig. 2 is the LCDs of prior art and the structural representation of intednsity circuit thereof;
Fig. 3 is the block diagram of LCDs and intednsity circuit thereof according to an embodiment of the invention;
Fig. 4 is the block diagram of LCDs and intednsity circuit thereof according to another embodiment of the present invention;
Fig. 5 is the circuit theory diagrams of LCDs and intednsity circuit thereof according to an embodiment of the invention;
Fig. 6 is a liquid crystal display assembly structure scheme of installation according to an embodiment of the invention;
Fig. 7 is the comparison diagram of LCDs brightness-time curve of the present invention and prior art LCDs brightness-time curve.
Embodiment
Fig. 1 is the schematic block diagram of traditional LCDs and intednsity circuit thereof.As shown in Figure 1, LCDs 10 has back light unit 101, and the user can be provided with circuit 30 through brightness and set its required brightness of display screen, and this brightness settings signal will be exported to control circuit 20.Control circuit 20 is according to the brightness settings signal that receives, and output corresponding driving signal is given back light unit 101, and its luminosity is controlled at setting value.Usually back light unit 101 is luminotrons, like cold cathode fluorescent tube (CCFL), light emitting diode (LED) etc.
Fig. 2 is the structural representation of an instance of traditional LCDs and intednsity circuit thereof, and wherein back light unit 101 is the CCFL luminotron.As shown in Figure 2, backlight liquid crystal display unit 101 is driven by external circuit.The control signal of Va for being provided with through the brightness of display user interface scalable.The user can reach the purpose of adjusting brightness through regulating this voltage Va.VCC is that circuit provides power supply.Control chip 102 comes the certain square wave driving signal of output duty cycle according to voltage Va, promotes metal-oxide-semiconductor Q and transformer T, and it is luminous to drive back light unit.
Design of the present invention is a kind of circuit that can make the luminosity automatic constant of back light unit of structure, can consist of the following components: a. detects back light unit and sends the luminance detection circuit of the brightness of light; The temperature sensing circuit of the environment temperature around when b. testing circuit is worked; C. the reference value with brightness detected value and user's setting compares, in addition temperature detection value comparator circuit by way of compensation; D. control circuit.According to specific embodiments, also optionally increase amplifying circuit, be used for the error signal of relatively circuit output is carried out the matching processing and amplifying.
Fig. 3 is the block diagram of LCDs and intednsity circuit thereof according to an embodiment of the invention.This embodiment compares with the backlight unit brightness control circuit of traditional LCDs shown in Figure 1, has increased luminance detection circuit 40 and comparator circuit 50.Luminance detection circuit 40 comprises the light sensing chip, and it sends into comparator circuit 50 after can the light signal from back light unit 101 being converted to corresponding electric signal.Comparator circuit 50 also receives the output that brightness is provided with circuit 30; And the signal that the signal of the representative real-time luminosity of luminance detection circuit 40 output and brightness are provided with the representative brightness settings that circuit 30 exports compared, compare result signal sends to control circuit 20.The compare result signal that control circuit 20 bases receive changes the size of the curtage of supplying with back light unit 101, thereby the luminosity of back light unit 101 is controlled at the brightness range of setting.
Fig. 4 is the block diagram of LCDs and intednsity circuit thereof according to another embodiment of the present invention.Compare with the embodiment of Fig. 3, increased temperature sensing circuit 60, the environment temperature around being used to monitor.Temperature sensing circuit 60 comprises a TEMP chip, and it sends into comparator circuit 50 after can the temperature signal from environment being converted to corresponding electric signal.Comparator circuit 50 is with the signal of the representative environment temperature of temperature sensing circuit 60 output signal by way of compensation; After the signal overall treatment of representative brightness settings that circuit 30 outputs are set with the signal of the representative real-time luminosity of luminance detection circuit 40 output and brightness, will compare/the result signal sends to control circuit 20.Comparison/result signal change that control circuit 20 bases receive is supplied with the size of the curtage of back light unit 101, thereby the luminosity of back light unit 101 is controlled at the brightness range of setting.
As preferably, in the backlight unit brightness automatic constant circuit of the present invention, between comparator circuit 50 and the control circuit 20, also can increase amplifying circuit, be used for the error signal of relatively circuit output is carried out the matching processing and amplifying.
What deserves to be mentioned is that comparator circuit 50 can adopt operational amplifier to realize, also can adopt other IC chip to realize.When adopting operational amplifier to realize comparator circuit, the output terminal of luminance detection circuit 40 and brightness are provided with the output terminal of circuit 30 can an input end in the same way that connect operational amplifier, and another connects the reverse input end of operational amplifier.And the output terminal of temperature sensing circuit 60 both can connect the input end in the same way of operational amplifier, also the reverse input end of optionally connected operational amplifier.
Fig. 5 is the circuit theory diagrams of LCDs and intednsity circuit thereof according to an embodiment of the invention.In the present embodiment, back light unit 101 is the CCFL luminotron.Luminance detection circuit comprises light sensing chip 106 and resistance R 1.Temperature sensing circuit comprises TEMP chip 103 and resistance R 2.Va is the brightness control signal that brightness is provided with circuit 30 outputs.Comparator circuit 50 comprises first operational amplifier 104 and capacitor C 1.Amplifying circuit comprises second operational amplifier 105 and resistance R 4, R5, R6, R7 and R8.Intednsity circuit 20 comprises control chip 102, metal-oxide-semiconductor Q and transformer T.
Its principle of work is: light sensing chip 106 is measured the brightness that back light unit 101 produces, and converts electric signal to, is delivered to the reverse input end of first operational amplifier 104 through resistance R 1.Brightness control signal Va is delivered to the input end in the same way of first operational amplifier 104 through R3.The temperature of TEMP chip 103 monitoring of environmental, signal also is delivered to the input end in the same way of first operational amplifier 104 through resistance R 2 by way of compensation.First operational amplifier 104 can produce an error signal.C1 is a feedback compensation electric capacity in addition.
Second operational amplifier 105 is formed reverse amplification circuit with resistance R 4/R5/R6/R7/R8.Produce the level that is adapted to control chip 102 after the processing of this grade of error signal process, after handling through control chip 106, output square wave driving signal driving transformer.The dutycycle of square wave driving signal changes with the variation of the received error signal amplitude of control chip 106, thereby can change lamp current to regulate output brightness.When display brightness did not reach setting brightness, error signal can increase the fluorescent tube drive current; And surpass when setting brightness, error signal can reduce the fluorescent tube drive current, so reaches the constant of brightness.Adjustment process need not people's intervention, and circuit is accomplished automatically fast.
As in a kind of embodiment, the TEMP chip also can be connected to the reverse input end of first operational amplifier 104 through resistance R 2.
Compare with the backlight unit brightness regulating circuit of traditional LCDs shown in Figure 2; The circuit of circuit in the backlight unit brightness automatic constant circuit of the present invention shown in Figure 5 in the frame of broken lines for increasing, this circuit production is placed on position among Fig. 6 after becoming circuit board in kind.It is connected through cable with other circuit boards.External circuit offers its power Vcc and control signal Va, it output signal to control chip 102.
Fig. 6 is the structural representation of this position of circuit platelet in LCD.Wherein:
100: preceding frame;
110: liquid crystal display;
120: liquid crystal display appears the aperture of light;
130: the support of permanent circuit platelet (on the stuck-at-50);
140: circuit platelet (optical sensor and temperature sensor are installed on this plate);
150: big fixed head (with 110 be fixed together, put the big plate of main control on it);
160: bonnet
Fig. 7 is the comparison diagram of LCDs brightness-time curve of the present invention and prior art LCDs brightness-time curve.Among Fig. 7, what draw with solid line is the curve of back light unit luminous intensity in the conventional liquid crystal, and its stability depends primarily on the characteristic (its characteristics of luminescence and time coordinate are the fluctuation relation) of fluorescent tube in the back light unit.What with dashed lines drew is the luminosity curve that the present invention has increased the display of brightness constancy circuit, and its brightness no longer relies on fluorescent tube, can not only fast and stable, and can be consistent for a long time, read the requirement of sheet and other purposes to meet medical treatment.In one embodiment, adopted the display of backlight unit brightness automatic constant circuit of the present invention, start or when energy saver mode was got back to normal manipulation mode, brightness of display screen can reach the brightness of setting in 20～30 seconds.
Claims (1)
1. LCD; It is characterized in that, comprise liquid crystal display (110) and before frame (100) and bonnet (160), and said liquid crystal display be fixed together the big fixed head (150), the circuit platelet (140) that are used to install the big plate of main control and be fixed on said big fixed head (150) _ on be used for fixing the support (130) of said circuit platelet; Be arranged at the back light unit (101) at the display screen back side, and backlight unit brightness automatic constant circuit;
Wherein, said backlight unit brightness automatic constant circuit comprises:
The intednsity circuit (20) and the brightness that link to each other with back light unit (101) are provided with circuit (30); Also comprise: the light sensing chip (106) and first operational amplifier (104) and second operational amplifier (105) that are used to detect the back light unit luminosity; Wherein, The output signal of said smooth sensing chip (106) links to each other through the inverting input that first resistance (R1) is coupled in said first operational amplifier (104), and the output signal that said brightness is provided with circuit (30) is coupled in the normal phase input end of said first operational amplifier (104) through the 3rd resistance (R3); The output terminal of said first operational amplifier (104) is connected in the inverting input of said second operational amplifier (105) through the 7th resistance (R7), and the normal phase input end of said second operational amplifier (105) is connected in node between power supply (Vcc) and the 4th resistance (R4) and the 6th resistance (R6) through the 5th resistance (R5) ground connection through the 6th resistance (R6) and the 4th resistance (R4); The output terminal of said second operational amplifier (105) is connected in said intednsity circuit (20); Be connected with feedback compensation electric capacity (C1) between the inverting input of said first operational amplifier (104) and the output terminal; Be connected with the 8th resistance (R8) between the inverting input of said second operational amplifier (105) and the output terminal;
The TEMP chip (103) that is used for the testing environment temperature, its output signal is coupled in the normal phase input end of said first operational amplifier (104) through second resistance (R2);
Said back light unit (101) comprises cathode fluorescent tube, and said intednsity circuit (20) comprises control chip (102), field effect transistor (Q) and transformer (T); Wherein, The input end of said control chip (102) links to each other with the output terminal of said second operational amplifier (105); The grid of said field effect transistor (Q) links to each other with the output port of said control chip (102), drain electrode links to each other with power supply (Vcc), source electrode links to each other with the elementary winding of transformer (T), and said cathode fluorescent tube links to each other with the secondary winding of transformer (T); The output signal of said control chip (102) is a square wave driving signal, and its dutycycle changes with the variation of the error signal amplitude of said second operational amplifier (105) output that receives;
Wherein, said smooth sensing chip (106), TEMP chip (103), first operational amplifier (104), second operational amplifier (105), first resistance to the, eight resistance and feedback compensation electric capacity (C1) all are arranged on the said circuit platelet (130).
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008100678264A CN101604507B (en) | 2008-06-11 | 2008-06-11 | LCD and backlight unit brightness automatic constant circuit thereof |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2008100678264A CN101604507B (en) | 2008-06-11 | 2008-06-11 | LCD and backlight unit brightness automatic constant circuit thereof |
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| CN101604507A CN101604507A (en) | 2009-12-16 |
| CN101604507B true CN101604507B (en) | 2012-05-02 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020098073A1 (en) * | 2018-11-12 | 2020-05-22 | 惠科股份有限公司 | Backlight adjustment circuit, backlight module and display apparatus |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102122483B (en) * | 2010-12-22 | 2013-08-21 | 利亚德光电股份有限公司 | Method and system for monitoring LED (light-emitting diode) display screen as well as LED display |
| CN102543011A (en) * | 2010-12-29 | 2012-07-04 | 广东中显科技有限公司 | Liquid crystal backlight drive system with adjustable brightness |
| CN108877688A (en) * | 2017-05-12 | 2018-11-23 | 京东方科技集团股份有限公司 | Backlight brightness control method and device |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2020098073A1 (en) * | 2018-11-12 | 2020-05-22 | 惠科股份有限公司 | Backlight adjustment circuit, backlight module and display apparatus |
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Address after: 518055 floor 15, building 6, Hengda fashion Huigu building (east area), Fulong Road, Henglang community, Dalang street, Longhua District, Shenzhen, Guangdong Patentee after: SHENZHEN BEACON DISPLAY TECHNOLOGY Co.,Ltd. Address before: 518057 Guangdong city of Shenzhen province Nanshan District South Road Chinese Development Institute of science and technology incubator building, room 208 Patentee before: SHENZHEN BEACON DISPLAY TECHNOLOGY Co.,Ltd. |
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