CN1302688C - backlight control unit - Google Patents
backlight control unit Download PDFInfo
- Publication number
- CN1302688C CN1302688C CNB02120022XA CN02120022A CN1302688C CN 1302688 C CN1302688 C CN 1302688C CN B02120022X A CNB02120022X A CN B02120022XA CN 02120022 A CN02120022 A CN 02120022A CN 1302688 C CN1302688 C CN 1302688C
- Authority
- CN
- China
- Prior art keywords
- coupled
- resistance
- differential amplifier
- backlight
- pulse wave
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 230000003287 optical effect Effects 0.000 claims description 9
- 239000004973 liquid crystal related substance Substances 0.000 abstract description 4
- 230000008859 change Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- CJOBVZJTOIVNNF-UHFFFAOYSA-N cadmium sulfide Chemical compound [Cd]=S CJOBVZJTOIVNNF-UHFFFAOYSA-N 0.000 description 5
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 5
- 239000003990 capacitor Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Images
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection
Landscapes
- Liquid Crystal Display Device Control (AREA)
- Liquid Crystal (AREA)
Abstract
A backlight control device is suitable for a liquid crystal display, the liquid crystal display has a backlight device, the backlight control device includes: a photosensitive transistor for sensing the background brightness; a control circuit for generating a signal for controlling the backlight device according to the phototransistor so that the backlight device adjusts the brightness according to the corresponding background brightness; the control circuit comprises a control voltage generating circuit, a control voltage generating circuit and a control circuit, wherein the control voltage generating circuit is coupled with the photosensitive transistor and generates a control voltage according to the induced photocurrent of the light sensing component; a pulse modulation circuit, which performs pulse modulation on the modulation clock signal according to the received control voltage and generates a corresponding pulse modulation signal; and the backlight driving circuit is coupled with the pulse wave modulation circuit and controls the backlight device according to the pulse wave modulation signal so as to adjust the brightness of the liquid crystal display.
Description
(1) technical field
The present invention is relevant for a kind of backlight control apparatus, particularly a kind of backlight control apparatus that adopts photistor induction background luminance.
(2) background technology
Generally need display unit backlight, LCD or the like for example, mostly be to use in portable electronic installation, as notebook (notebook), electronic dictionary (electronic dictionary) and personal digital assistant (personal digital agent, PDA) etc.When action need display unit backlight, external light source tends to directly have influence on the visual level of comfort of user.Therefore, described portable electronic equipment must provide suitable light modulation mechanism, so that can adjust power backlight at any time.
Known backlight dimming mechanism mainly contains two kinds, and a kind of is manual type (manual), and another kind is that cadmium sulphide photoconductive cell is as the backlight control apparatus assembly.
The manual type user can flexibly adjust the backlight of display unit by button on the specific keyboard that light-control knob or device disposed.Yet this kind conventional approaches has two shortcomings.First, because LCD mostly is to use in portable electronic product, so usually be in different operating environment (different background light), even in operating process, promptly be in mobile state, when for example in the vehicles that move, using these portable electronic installations.Therefore, the user must often carry out light modulation, even the job in hand that may also need to stop when operation is carried out light modulation.Like this, certainly, can cause the inconvenience in the use.The second, the user may be for fear of frequent adjustment operation backlight, and back light is fixed on the stronger scale.This practice no doubt can reach certain effect of saving operation, but can extend out another problem that is the problem of electrical source consumption.General portable electronic equipment is because therefore its characteristic movably mostly uses the source of battery as supply of electric power.Also therefore economizing on electricity often, portable electronic produces considerable problem.If consumed too many unnecessary electric power in order to economize trouble, obviously be not the suitable practice.
Cadmium sulphide photoconductive cell is to utilize cadmium sulphide photoconductive cell to change resistance value according to background luminance as the backlight control apparatus assembly, resistance value according to corresponding background luminance, produce a pulse wave signal corresponding to resistance value, microprocessor produces a pulse wave width modulation signal according to the frequency of pulse wave signal, and backlight drive circuit is according to pulse wave modulating signal control brightness of backlight.But cadmium sulphide photoconductive cell is in the photobehavior instability of high brightness, and correctly sensing background luminance, so backlight can't be adjusted to suitable brightness.
(3) summary of the invention
Main purpose of the present invention is to provide a kind of backlight control apparatus of display, its adjustment circuit backlight can be automatically external environment when using adjust needed size backlight; On the other hand, also can avoid cadmium sulphide photoconductive cell photoinduction characteristic when high brightness instability and can't respond to background luminance really and suitably regulate backlight.
According to above-mentioned purpose, backlight control apparatus of the present invention is applicable to a LCD, and described LCD has a back lighting device, described backlight control apparatus comprises: optical sensing subassembly, and it produces corresponding photoelectric current in order to the background luminance of the described LCD of sensing; The control voltage generation circuit, it is coupled to described optical sensing subassembly, produces the control voltage of a correspondence according to the photoelectric current of described optical sensing subassembly; One pulse wave modulation circuit is coupled to described control voltage generation circuit and receives a modulation clock signal, and it carries out a pulse wave modulation according to described control voltage to described modulation clock signal, and produces the pulse wave modulating signal of a correspondence; And a backlight drive circuit, being coupled to described pulse wave modulation circuit, it controls described back lighting device according to described pulse wave modulating signal, uses and adjusts described device brightness; Be characterized in: described control voltage generation circuit comprises: one first resistance, and its first end is coupled to described photistor; Second end that one second resistance, its first end are coupled to described the first transistor with, and described second resistance, second end is coupled to a voltage source; One the 3rd resistance, its first end are coupled to described first resistance, first end; One the 4th resistance, its first end are coupled to described the 3rd resistance second end, and described the 4th resistance second end is coupled to described voltage source; One differential amplifier; Its non-inverting input is coupled to described the 3rd resistance second end; One the 5th resistance, its first end are coupled to described first resistance, second end, and described the 5th resistance second end is coupled to described differential amplifier end of oppisite phase; And one the 6th resistance, its first end is coupled to described differential amplifier end of oppisite phase, and described the 6th resistance second end is coupled to described differential amplifier output; And described pulse wave modulation circuit is a pulse width modulation circuit, and described pulse width modulation circuit comprises: one first differential amplifier, and its inverting input is coupled to control voltage, and output is coupled to the pulse wave width modulation signal; One electric capacity, its first end is coupled to the non-inverting input of described first differential amplifier; One second differential amplifier, its inverting input are coupled to described electric capacity second end, and the non-inverting input of described second differential amplifier is coupled to a voltage source, and described differential amplifier output is coupled to the non-inverting input of described first differential amplifier; One first resistance, its first end is coupled to the output of described second differential amplifier; One the 3rd differential amplifier, its non-inverting input are coupled to second end of described first resistance; One second resistance, its first end is coupled to the non-inverting input of described the 3rd differential amplifier, and second end of described second resistance is coupled to the output of described the 3rd differential amplifier; And one the 3rd resistance, its first end is coupled to the output of described the 3rd differential amplifier, and second end of described the 3rd resistance is coupled to the inverting input of described second differential amplifier.
Optical sensing subassembly of the present invention can be a photistor, in order to the sensing background luminance; Control circuit can produce the signal of control back lighting device according to photistor, makes back lighting device adjust brightness according to corresponding background luminance; Wherein control circuit comprises a control voltage generation circuit, is coupled to photistor, and it produces a control voltage according to the induction light electric current of optical sensing subassembly; One pulse wave modulation circuit carries out the pulse wave modulation according to received control voltage to the modulation clock signal, and produces corresponding pulse wave modulating signal; Backlight drive circuit is coupled to described pulse wave modulation circuit, and it controls described back lighting device according to described pulse wave modulating signal, uses and adjusts described LCD brightness.
For further specifying purpose of the present invention, design feature and effect, the present invention is described in detail below with reference to accompanying drawing.
(4) description of drawings
Fig. 1 is the functional block diagram of automatic brightness control device in expression a preferred embodiment of the present invention.
Fig. 2 is the circuit diagram of control voltage generation circuit in expression a preferred embodiment of the present invention.
Fig. 3 is the circuit diagram of pulse width modulation circuit in expression a preferred embodiment of the present invention.
Fig. 4 is the signal waveform schematic diagram of pulse width modulation circuit in expression a preferred embodiment of the present invention.
Fig. 5 is a photistor photobehavior schematic diagram in expression a preferred embodiment of the present invention.
Fig. 6 is the circuit diagram of backlight drive circuit in expression a preferred embodiment of the present invention.
(5) embodiment
Backlight control apparatus of the present invention mainly is to utilize photistor as the brightness sensing component, with the background luminance of sensing LCD, produces a pulse wave modulating signal according to the brightness sensed result again and controls brightness backlight.Therefore, this device can be according to the background luminance state, and backlight liquid crystal display brightness is adjusted on continuity ground, makes it present harmony between the two, that is when background luminance improves, can flexibly reduce backlight illumination; When background luminance reduced, the backlight illumination that also can flexibly raise was to reduce its power consumption.Following conjunction with figs. illustrates the detailed content of a preferred embodiment of the present invention.
Fig. 1 is the functional block diagram of automatic brightness control device in expression a preferred embodiment of the present invention.As shown in the figure, automatic brightness control device comprises control voltage generation circuit 100, pulse width modulation circuit 200, backlight drive circuit 300 and backlight 400, is used for flexibly controlling backlight 400 according to the state that installs the place background luminance.
Control potential circuit 200 comprises photistor 10, resistance R 1, resistance R 2 and the resistance R 3, R4, R5, R6 and the differential amplifier 20 that constitute the brightness detecting circuit, as shown in Figure 2.Resistance R 1, R2 and photistor 10 are the relation of series connection, and are coupled between voltage source V CC and the earth terminal.
If R3/R4=R5/R6
V1＝R3/R4·VR1 (1)
According to the relation shown in (1) formula, when the brightness impression voltage drop VR1 of resistance R 1 changed, control voltage V1 also can be along with change.Therefore, the magnitude of voltage of control voltage V1 is comprising the state information of LCD background luminance.
Pulse width modulation circuit 200 comprises differential amplifier 26, resistance R 35 and capacitor C 1, differential amplifier 24, resistance R 25, resistance R 30, and differential amplifier 22, as shown in Figure 3.The effect of pulse width modulation circuit 200 is according to the magnitude of voltage of control voltage V1, carries out pulse wave width modulation (pulse width modulation) for triangular signal VA, produces a pulse wave width modulation signal V2.In the present embodiment, differential amplifier the 22,24, the 26th utilizes 741 IC to constitute, and resistance R 25, R30, R35 and capacitor C 1 then are its circuit perimeter component.Yet for person skilled in the art scholar,, can also constitute pulse wave modulation circuit 4 in the present embodiment by other IC assembly or circuit as long as can carry out pulse wave width modulation according to control voltage V2.
In pulse width modulation circuit 200, differential amplifier 26, resistance R 35, capacitor C 1 are formed an integrator.Differential amplifier 24, resistance R 25, resistance R 30 are formed a Schmidt trigger circuit (Schmitttrigger).The integrator output signal feeds back to Schmidt trigger circuit, produces a triangular signal VA.Differential amplifier 22 is comparators, and it is in order to reception triangular signal VA and control voltage V1, and output pulse wave width modulation signal V2.The action of pulse width modulation circuit 200 can be described below.At first, receive control voltage V1, and receive the triangular signal VA that treats modulation from control voltage generation circuit 100.Then utilize the magnitude of voltage of control voltage V1, with triangular signal VA relatively, make the width of each pulse wave among the pulse wave width modulation signal V2 all corresponding to the magnitude of voltage of control voltage V1, just the luminance state of background.
The molar behavior of above-mentioned control voltage generation circuit 100, pulse width modulation circuit 200 and backlight drive circuit 300 and being described below.When background luminance changed, the collected current of photistor 10 also can be along with change, and the change direction be generally forward, i.e. brightness rising collected current rises, and brightness descends then that collected current descends.Because collected current changes, make the control voltage V1 of output also change thereupon.After the process processing of pulse width modulation circuit 200, the pulse bandwidth among the pulse wave width modulation signal V2 also can be along with change.Utilize the switch motion of transistor Q3 at last, can adjust the brightness of backlight 400.
Certainly, those of ordinary skill in the art will be appreciated that, above embodiment is used for illustrating the present invention, and be not to be used as limitation of the invention, as long as in connotation scope of the present invention, all will drop in the scope of claims of the present invention variation, the modification of the above embodiment.
Claims (2)
1. a backlight control apparatus is applicable to a LCD, and described LCD has a back lighting device, and described backlight control apparatus comprises:
Optical sensing subassembly, it produces corresponding photoelectric current in order to the background luminance of the described LCD of sensing;
The control voltage generation circuit, it is coupled to described optical sensing subassembly, produces the control voltage of a correspondence according to the photoelectric current of described optical sensing subassembly;
One pulse wave modulation circuit is coupled to described control voltage generation circuit and receives a modulation clock signal, and it carries out a pulse wave modulation according to described control voltage to described modulation clock signal, and produces the pulse wave modulating signal of a correspondence; And
One backlight drive circuit is coupled to described pulse wave modulation circuit, and it controls described back lighting device according to described pulse wave modulating signal, uses and adjusts described device brightness;
It is characterized in that:
Described control voltage generation circuit comprises:
One first resistance, its first end is coupled to described photistor;
Second end that one second resistance, its first end are coupled to described the first transistor with, and described second resistance, second end is coupled to a voltage source;
One the 3rd resistance, its first end are coupled to described first resistance, first end;
One the 4th resistance, its first end are coupled to described the 3rd resistance second end, and described the 4th resistance second end is coupled to described voltage source;
One differential amplifier; Its non-inverting input is coupled to described the 3rd resistance second end;
One the 5th resistance, its first end are coupled to described first resistance, second end, and described the 5th resistance second end is coupled to described differential amplifier end of oppisite phase; And
One the 6th resistance, its first end is coupled to described differential amplifier end of oppisite phase, and described the 6th resistance second end is coupled to described differential amplifier output; And
Described pulse wave modulation circuit is a pulse width modulation circuit, and described pulse width modulation circuit comprises:
One first differential amplifier, its inverting input is coupled to control voltage, and output is coupled to the pulse wave width modulation signal;
One electric capacity, its first end is coupled to the non-inverting input of described first differential amplifier;
One second differential amplifier, its inverting input are coupled to described electric capacity second end, and the non-inverting input of described second differential amplifier is coupled to a voltage source, and described differential amplifier output is coupled to the non-inverting input of described first differential amplifier;
One first resistance, its first end is coupled to the output of described second differential amplifier;
One the 3rd differential amplifier, its non-inverting input are coupled to second end of described first resistance;
One second resistance, its first end is coupled to the non-inverting input of described the 3rd differential amplifier, and second end of described second resistance is coupled to the output of described the 3rd differential amplifier; And
One the 3rd resistance, its first end is coupled to the output of described the 3rd differential amplifier, and second end of described the 3rd resistance is coupled to the inverting input of described second differential amplifier.
2. backlight control apparatus as claimed in claim 1 is characterized in that, described optical sensing subassembly is a photistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB02120022XA CN1302688C (en) | 2002-05-15 | 2002-05-15 | backlight control unit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB02120022XA CN1302688C (en) | 2002-05-15 | 2002-05-15 | backlight control unit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1459997A CN1459997A (en) | 2003-12-03 |
| CN1302688C true CN1302688C (en) | 2007-02-28 |
Family
ID=29426920
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB02120022XA Expired - Fee Related CN1302688C (en) | 2002-05-15 | 2002-05-15 | backlight control unit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1302688C (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7675501B2 (en) | 2003-12-17 | 2010-03-09 | Samsung Electronics Co., Ltd. | Liquid crystal display apparatus with light sensor |
| US20060108519A1 (en) * | 2004-11-24 | 2006-05-25 | Au Optronics Corporation | Enhanced flat-panel display photosensing apparatus and method thereof |
| CN100337151C (en) * | 2005-01-28 | 2007-09-12 | 广辉电子股份有限公司 | Control module and control method of backlight module and liquid crystal display applied thereto |
| CN100414355C (en) * | 2005-06-14 | 2008-08-27 | 群康科技(深圳)有限公司 | Backlight on control circuit |
| CN100527205C (en) * | 2006-03-20 | 2009-08-12 | 广达电脑股份有限公司 | Brightness adjustment device and method thereof |
| CN103354689B (en) * | 2013-08-02 | 2015-06-17 | 张掖市华光太阳能有限公司 | Driving power device for LED lamp dimming |
| CN112788809A (en) * | 2019-10-23 | 2021-05-11 | 致伸科技股份有限公司 | Light brightness adjusting device |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5272327A (en) * | 1992-05-26 | 1993-12-21 | Compaq Computer Corporation | Constant brightness liquid crystal display backlight control system |
| JPH10111487A (en) * | 1996-10-07 | 1998-04-28 | Yokogawa Electric Corp | LCD backlight drive circuit |
| CN2453468Y (en) * | 2000-12-06 | 2001-10-10 | 国碁电子股份有限公司 | LCD backlight module |
| JP2002057920A (en) * | 2000-08-07 | 2002-02-22 | Hitachi Ltd | Video cameras and electronic still cameras |
-
2002
- 2002-05-15 CN CNB02120022XA patent/CN1302688C/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5272327A (en) * | 1992-05-26 | 1993-12-21 | Compaq Computer Corporation | Constant brightness liquid crystal display backlight control system |
| JPH10111487A (en) * | 1996-10-07 | 1998-04-28 | Yokogawa Electric Corp | LCD backlight drive circuit |
| JP2002057920A (en) * | 2000-08-07 | 2002-02-22 | Hitachi Ltd | Video cameras and electronic still cameras |
| CN2453468Y (en) * | 2000-12-06 | 2001-10-10 | 国碁电子股份有限公司 | LCD backlight module |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1459997A (en) | 2003-12-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7855515B2 (en) | High-voltage high-power constant current LED driver device | |
| CN1041655C (en) | Back-lit circuit for LCD | |
| KR100360931B1 (en) | Control circuit and method for piezoelectric transformer | |
| KR101945909B1 (en) | Led backlight drive circuit and liquid crystal display | |
| US8018425B2 (en) | Driving apparatus of light emitting diode and liquid crystal display using the same | |
| US20080136771A1 (en) | Backlight control circuit with primary and secondary switch units | |
| TW201031270A (en) | Inverter for liquid crystal display | |
| US20100194285A1 (en) | Light source driving apparatus and light source apparatus having the same | |
| CN1638597A (en) | Single-stage backlight inverter and method for driving the same | |
| CN111445869A (en) | A brightness control device and its control method, and a display panel | |
| US8624522B2 (en) | Backlight control circuit | |
| CN201122422Y (en) | LCD device | |
| CN1302688C (en) | backlight control unit | |
| CN107396483B (en) | power conversion device | |
| CN203134330U (en) | LED display screen backlight brightness adjusting circuit and LED television | |
| CN1719960A (en) | Discharge lamp lighting apparatus for lighting multiple discharge lamps | |
| CN110545598B (en) | A control circuit and control method for equipment power supply | |
| CN1215639C (en) | Adjustable brightness power conversion circuit suitable for display device backlight module | |
| CN201118796Y (en) | Under voltage protection circuit | |
| CN2838200Y (en) | Boosting white LED drive | |
| CN103517504A (en) | Light emitting diode driving apparatus | |
| CN101242694B (en) | Brightness control circuit and backlight control module | |
| CN1717144A (en) | Cold-cathode fluorescence lamp digital drive system | |
| CN1126974C (en) | Device and method for adjusting backlight of display device | |
| CN210202130U (en) | Dimming mobile induction device compatible with LED driver |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20070228 |