CN1573893A - Apparatus and method for controlling inverter pulse width modulation frequency in LCD in portable computer - Google Patents
Apparatus and method for controlling inverter pulse width modulation frequency in LCD in portable computer Download PDFInfo
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- CN1573893A CN1573893A CNA2004100474860A CN200410047486A CN1573893A CN 1573893 A CN1573893 A CN 1573893A CN A2004100474860 A CNA2004100474860 A CN A2004100474860A CN 200410047486 A CN200410047486 A CN 200410047486A CN 1573893 A CN1573893 A CN 1573893A
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/3406—Control of illumination source
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/1336—Illuminating devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/70—Lamps with low-pressure unconstricted discharge having a cold pressure < 400 Torr
- H01J61/76—Lamps with low-pressure unconstricted discharge having a cold pressure < 400 Torr having a filling of permanent gas or gases only
- H01J61/78—Lamps with low-pressure unconstricted discharge having a cold pressure < 400 Torr having a filling of permanent gas or gases only with cold cathode; with cathode heated only by discharge, e.g. high-tension lamp for advertising
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
- G09G2330/02—Details of power systems and of start or stop of display operation
- G09G2330/021—Power management, e.g. power saving
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Abstract
Apparatus and methods according to embodiments of the present invention can control an inverter pulse width modulation (PWM) frequency of a liquid crystal display (LCD) in a portable computer or the like. Noise and/or interference caused by a system environment can be detected and one of a plurality of LCD frame frequencies can be selected responsive to the system environment. Interference between a PWM frequency of an inverter can be reduced or prevented by identifying a desired PWM frequency of the inverter adapted to control a brightness of the LCD based on the selected LCD frame frequency or the like, and driving the LCD using the same.
Description
Background of invention
Invention field
The present invention relates to be suitable for controlling in the portable computer apparatus and method such as the display brightness of LCD (LCD).
Background of related
The product that directly LCD is used as display unit comprises desk-top computer and various portable set, such as notebook and PDA(Personal Digital Assistant).Need reduce or the consumption of minimum power such as the portable set of notebook and PDA.
The structure of the schematically illustrated correlation technique portable computer such as notebook of Fig. 1.As shown in Figure 1, notebook comprises CPU (central processing unit) (CPU) 10, Video Controller 11, main frame-PCI bridge 12, storer 13, video-ram 14, Audio Controller 15, LAN controller 16, card bus controller 17, PCI-ISA bridge 18, LCD19, microcomputer (micro computer) 20 and keyboard 21, and they all connect by bus line.
PCI-ISA bridge 18 comprises CMOS-RAM 180.Microcomputer 20 comprises ROM 200, RAM 201 and keyboard controller 203.
As shown in Figure 2, LCD19 in its underpart or top place be provided with light-emitting component 190, such as cold-cathode fluorescence lamp (CCFL).Also comprise the unit that is used to control LCD19 brightness in the notebook.This brightness control unit comprises power supply unit 30 and transducer (inverter) 33.The voltage transitions that power supply unit 30 is used for providing from battery 31 or AC adapter 32 becomes predetermined level, and the voltage of this predetermined level is provided.The voltage transitions that the predetermined level that will provide from power supply unit 30 is provided transducer 33 becomes to have the signal with the synchronous waveform of pwm signal, and the signal after will changing affacts on the CCFL190.
The pwm signal that is input to transducer 33 from microcomputer 20 can be set the fixed frequency that has from 100Hz to 400Hz for, for example is 210Hz.In this case, transducer 33 output has the signal with the waveform of the Frequency Synchronization of 210Hz.Output signal from transducer 33 is applied on the CCFL190 of LCD19, thereby the brightness of LCD19 is remained on specified level.For brilliance control, transducer 33 is regulated in 0 to 100% scope according to required luminance level in the information of institute's selected frequency reception about working time dutycycle (on-time duty).
Therefore, transducer 33 will convert to from the predetermined voltage level of power supply unit 30 to have and the synchronous frequency of the pwm signal of microcomputer 20 output and the signal of working time dutycycle, and resultant signal is outputed to CCFL190 so that the brightness of control LCD19.But, in operation, can disturb the frame frequency of LCD19 from the frequency with the synchronous signal of pwm signal of transducer 33 outputs, thereby on the LCD screen, noise occur.
Therefore, set the PWM frequency of transducer usually according to the frame frequency of LCD.Typically, the PWM frequency setting becomes n times (n doubly) than frame frequency (being vertical synchronization (Vsync) frequency) to exceed 20 to 30Hz.If the difference between PWM frequency and the n times frame frequency is less than 20Hz, the possibility that then occurs noise owing to frequency interferences on LCD will increase.
Noise that frequency interferences causes generate can by expression formula " f=ABS[PWM frequency-(frame frequency xn)] (and n=1 wherein, 2,3,4 ...) and expression.In this expression formula, " f 〉=15 " are corresponding to steady state (SS), and " f＜15 are " corresponding to non-steady state.
Therefore, when the frame frequency (being the Vsync frequency) of LCD was 60Hz, suitable PWM frequency range was as follows:
(60*1)+20～30=80～90; (60*2)+20～30=140～150; (60*3)+20～30=200～210; (60*4)+20～30=260～270; (60*5)+20～30=320～330; And (60*6)+20～30=380～390.The center frequency value of these frequencies (be 90Hz, 150Hz, 210Hz, 270Hz ...) can be as the optimum setting value of PWM frequency.Particularly, 210Hz or 270Hz are used as the PWM frequency.For the centre frequency of 270Hz, for the LCD of 60Hz frame frequency, 255Hz can think to stablize the PWM frequency range to the frequency range of 285Hz.When using the LCD of single fixedly Vsync signal, for example in the situation of the Vsync frequency that only allows 60Hz for (or homotype) of the same race portable computer LCD, can set its PWM frequency according to aforesaid way.
But for example the correlation technique apparatus and method of controlling LCD brightness have various shortcomings being used in the portable computer.In the homotype portable computer, use Different L CD and these LCD use in the situation such as 50Hz, 56Hz and the different Vsync frequencies of 60Hz (or 45Hz, 57Hz and 60Hz), be difficult to or can not be that all LCD select PWM frequencies.As a result, in a specific LCD, can produce noise.For example, in the PWM fixed-frequency in the situation of 210Hz with the Vsync frequency that satisfies 60Hz, because the difference between the PWM frequency of the multiple of Vsync frequency and 210Hz corresponding to 10 or 14Hz (f＜20), uses the LCD of 50Hz or 56HzVsync frequency will be owing to the frequency interferences generted noise.Therefore, when the notebook of correlation technique is configured to control the LCD frame frequency, because the interference that the frame frequency of LCD and being used to is controlled between the PWM frequency of LCD brightness will produce deterioration of image quality.
Above reference is combined in this, and it is suitable for the instruction of additional or optional details, characteristics and/or technical background.
Summary of the invention
One object of the present invention is to solve the problems referred to above and/or shortcoming at least, and advantage described below at least is provided.
Another object of the present invention is to provide a kind of apparatus and method that are used for control change device PWM frequency, and it is suitable for controlling the brightness of the LCD relevant with the LCD frame frequency.
Another object of the present invention is to provide a kind of apparatus and method that are used for control change device PWM frequency, and it is suitable for controlling the brightness of middle LCD such as portable computer, and it can set the specify transformations device PWM frequency that causes less frequency interferences.
Another object of the present invention is to provide a kind of apparatus and method that are used for control change device PWM frequency, and it is suitable for controlling the brightness of LCD, even allow LCD to use various frame frequencies also can use single inverter with selected or best PWM frequency drives LCD.
Another object of the present invention is to provide a kind of apparatus and method that are used for control change device PWM frequency, and it is suitable for by automatically the PWM frequency being adjusted to the selected brightness of controlling LCD of a plurality of frequencies, and this frequency causes less frequency interferences.
Another object of the present invention is to provide a kind of apparatus and method that are used for control change device PWM frequency, it is suitable for controlling the brightness of LCD in the portable computer, and the vertical synchronizing frequency that it comprises in can the expanded display recognition data (EDID) with LCD is set the specify transformations device PWM frequency that causes less frequency interferences.
Another object of the present invention is to provide a kind of PWM frequency that is used for controlling various types of LCD that the homotype portable computer uses, and it can drive each light-emitting component of LCD with single inverter with assigned frequency.
In order to realize above-mentioned purpose and advantage in whole or in part at least, a kind of device that is used to control width modulation (PWM) frequency of LCD (LCD) is provided, it comprises control module, is used for according to the LCD frame frequency of system environments change LCD and according to the LCD frame frequency output information that changes; The PWM converting unit is used for the pwm signal according to the information generation LCD transducer that receives from described control module; And driver element, being used for converting input voltage to signal, the waveform of described signal is synchronous with the pwm signal that receives from the PWM converting unit.
In order at least further to realize above-mentioned purpose and advantage in whole or in part, a kind of method that is used to control width modulation (PWM) frequency of LCD (LCD) is provided, it comprises the frame frequency of discerning LCD, and according to the frame frequency output PWM information that identifies; And generate pwm signal according to the brilliance control information of PWM information and LCD lamp.
In order at least further to realize above-mentioned purpose and advantage in whole or in part, a kind of device that is used to control inverter pulse width modulation (PWM) frequency of LCD (LCD) is provided, and it comprises: be used for according to system environments select LCD a plurality of different frame frequencies each and according to the controller of the selected frame frequency output PWM information of LCD lamp and the PWM converter that is used for generating pwm signal according to PWM information.
To in description, set forth other advantage of the present invention, purpose and characteristics, and can by to following content check or those skilled in the art are understood in the present technique field by being learnt from the practice of the present invention to make.Objects and advantages of the present invention can realize as particularly pointing out in the appended claims and obtain.
Summary of drawings
To be described in detail with reference to the attached drawings the present invention, wherein identical label is represented components identical, wherein:
Fig. 1 is the block diagram that the portable computer configuration of correlation technique is shown;
Fig. 2 is the block diagram that LCD brightness controlling device in the portable computer of correlation technique is shown;
Fig. 3 is the block diagram that illustrates according to the preferred embodiment of the device of control brightness in the display of portable computer of the present invention;
Figure 4 and 5 are synoptic diagram, with the form of showing exemplary expanded display recognition data (EDID) are shown;
Fig. 6 is a process flow diagram, and the preferred embodiment of the method for the transducer PWM frequency of control LCD in portable computer is shown according to the present invention;
Fig. 7 is the diagram that the table of the exemplary values that can be used for Fig. 3 device is shown;
Fig. 8 is the block diagram that another preferred embodiment of the device of control brightness in the display of portable computer is shown according to the present invention;
Fig. 9 is the circuit diagram that the preferred embodiment of the PWM converter that comprises in Fig. 8 device is shown; And
Figure 10 is the oscillogram from the signal of each element output of Fig. 8 device; And
Figure 11 is the diagram that the table of the exemplary values that can be used by Fig. 8 device is shown.
Embodiment
Embodiment according to transducer PWM frequency control apparatus of the present invention and method can be applied on the portable computer.For example, can be applied on the notebook with configuration shown in Figure 3 according to embodiments of the invention.The LCD of notebook has EEPROM, and it is a nonvolatile memory.EEPROM can store the expanded display recognition data (EDID) that is used for LCD.
Shown in Figure 4 and 5, exemplary EDID comprises the information about the Displaying timer scope restriction (display timing range limit) that comprises the LCD frame frequency.As shown in Figure 5, the minimum or lower frame frequency of " minimum frame/field rate (frame/field rate) of representing with Hz " preferred expression, and " largest frames/field rate of representing with Hz " preferred expression maximum or higher frame frequency.The LCD frame frequency that comprises in the Displaying timer scope restricted information can be represented by minimum shown in Figure 5 and maximum frame rate.But, the invention is not restricted to this.Perhaps, the LCD frame frequency can be by the difference expression between average frame frequency (for example, the mean value between minimum and the maximum frame rate) and minimum or maximum frame rate and the frequency averaging value.In the former situation, can from minimum and maximum frame rate, derive according to institute's choosing method and specify frame frequency or best frame frequency.In the latter's situation, can select appointment frame frequency or the best frame frequency of frequency averaging value as LCD.
As shown in Figure 3, the microcomputer 20a of the notebook of the application embodiment of the invention preferably has the relevant function of above-mentioned microcomputer 20.In addition, according to LCD frame frequency such as vertical synchronizing frequency, the PWM frequency of the preferred control change device of microcomputer 20a, this frequency adaptation is in the brightness of control LCD.
For example, suppose LCD, and these LCD are installed on the notebook of homotype with three Vsync frequencies that contain 50Hz, 56Hz and 60Hz.In this case, the Vsync frequency that comprises in the EDID that writes down among the EEPROM of LCD can be with the parameter of PWM frequency that acts on control LCD.
Can use expression formula " PWM frequency=Vsync*n-m " or expression formula " PWM frequency=Vsync*n+m " to realize less or do not have the setting of the required or best PWM frequency of frequency interferences substantially.As an example, (for example be set at 4 and 30 respectively in the value of using expression formula " PWM frequency=Vsync*n-m " and n and m, n=4 and m=30) situation in, when " Vsync=50Hz " the best PWM frequency of LCD be 170Hz (for example, PWM=50*4-30=170), when " Vsync=56Hz " the best PWM frequency of LCD be 190Hz (for example, PWM=56*4-30=190), and when " Vsync=60Hz " the best PWM frequency of LCD be 210Hz (for example, PWM=60*4-30=210).
The information that obtains according to said process is determined by PWM generative circuit (for example, microcomputer 20a) preferably or offers the PWM generative circuit that it then produces the pwm signal of different frequency according to each Vsync frequency of LCD.Like this, the PWM generative circuit can be to transducer 33 output pwm signals, derivation for 170 is worth this pwm signal and is controlled as 170Hz, and the derivation for 190 is worth this pwm signal and is controlled as 190Hz, perhaps is worth this pwm signal for 210 derivation and is controlled as 210Hz.Transducer 33 can be applied to a final output light-emitting component 190 of LCD, and wherein final output is synchronous with the pwm signal that has according to the frequency of the Vsync signal controlling of each LCD.
As mentioned above, can in microcomputer 20a, determine pwm signal.But, because this definite can carrying out in other place (such as transducer (for example, transducer 33) or primary processor) in portable computer the invention is not restricted to this.
Fig. 6 is the method that illustrates according to the transducer PWM frequency of middle control LCD such as portable computer of the present invention.To describe method shown in Figure 6 and apply it in the portable computer of Fig. 3.But, the invention is not restricted to this.
As shown in Figure 6, after process began, when current operator scheme was set to PWM frequency control pattern (piece S10), microcomputer 20a can search the Vsync frequency information (piece S11) of EDID to comprise among the identification EDID.The expression formula " PWM frequency=Vsync*n-m " of can for example using microcomputer 20a derives from the appointment PWM frequency (piece S12) of transducer, and is the selected or best PWM frequency (piece S13) of transducer with the PWM frequency setting that derives from.After this, microcomputer 20 can discharge PWM frequency control pattern (piece S14).This PWM frequency control operation can realize by other component devices that docks with microcomputer 20a.
In addition, microcomputer 20a can store designated value, such as upgrading the exemplary tabulation that the PWM frequency is exported in relevant appointment with LCD shown in Figure 7.In this case, can use the correlation of storage to derive from PWM frequency (for example, Fig. 7 of exemplary) (piece S12).In addition, can be by such as other parts management of the portable computer of transducer (for example transducer 33) and/or store stored value.
As mentioned above, the embodiment that controls the apparatus and method of LCD transducer PWM frequency according to the present invention has various advantages.Can reduce or stop because the noise that the interference between the PWM frequency of the vertical synchronizing frequency of LCD and transducer causes generates according to embodiments of the invention.
Fig. 8 is a block diagram, and the device of control brightness in the display of portable computer in accordance with another embodiment of the present invention is shown.The device of Fig. 8 can be controlled the transducer PWM frequency of LCD.
The device that is used for control change device PWM frequency can comprise refresh rate controller 200, and it is programmed to change alternatively the frame frequency of LCD.Controller 200 can be included in and be used in the part of operating system managing video signal.When changing the frame frequency of LCD, controller 200 can output to brightness controller 230 with the information about the frame frequency that changed.
As shown in Figure 8, LCD220 can be the display unit that uses in notebook, PDA, desk-top computer or the like.LCD220 shows various vision signals under the control of Video Controller 210.Video Controller 210 can be adjusted the frame frequency (for example from 60Hz to 57Hz, 45Hz or the like) of LCD220 under the control of refresh rate controller 200.
Equally, according to the frame frequency of the variation of LCD, the device that is used for control change device PWM frequency can comprise the device that is used for control change device PWM frequency, and this transducer PWM frequency will be imported into the LCD lamp 260 that preferably is contained among the LCD220.LCD lamp 260 is light-emitting component preferably, and it is fit to luminous so that the brightness of control LCD220.Therefore, the brightness of LCD 220 changes according to the brightness of LCD lamp 260.
In order to control the brightness of LCD lamp 260, can preferably brightness controller 230 be arranged on the device that is used for control change device PWM frequency shown in Figure 8.Brightness controller 230 can receive the frame frequency of brilliance control information and LCD220 from refresh rate controller 200, exports the PWM information that obtains according to the PWM frequency computation part based on described frame frequency with brilliance control information subsequently.For example, microcomputer or SMSC microprocessor can be used for brightness controller 230.
Like this, the control of the LCD lamp 260 among Fig. 8 embodiment is not carried out in the refresh rate controller 200 of main control unit preferably, and carries out in brightness controller 230.This control configuration of preferred employing can be equipped with the controller that separates that is used for controlling respectively peripheral unit (such as display unit and keyboard) because comprise most computing machines of notebook.But brightness controller and refresh rate controller can be realized with single controller, for example only aspect the control of LCD lamp.
Preferably, must set PWM information makes the output of PWM converter corresponding to selection or the best PWM frequency of importing PWM information.The variable range of pwm signal is set in the situation of 150 to 300Hz scope in an embodiment, and the PWM converter can be suitable for producing the PWM frequency change of every 0.01V 0.5Hz of PWM information.Subsequently, can form PWM information and export the numerical range to the 3V between the 3V such as 0V.But, the invention is not restricted to this.
Brightness controller 230 can output to PWM converter 240 with brilliance control information and PWM information.PWM converter 240 can output to pwm signal transducer 250 or the like, and this pwm signal has corresponding to the PWM frequency of PWM information change with corresponding to the working time dutycycle of brilliance control information.Transducer 250 preferably offers supply voltage the pwm signal Switching power voltage of 260 whiles of LCD lamp according to frequency change.
At the embodiment that is used for controlling transducer PWM frequency shown in Figure 8, PWM converter 240 separates with transducer 250.But PWM converter 240 can be configured to be included in the transducer 250.Can be combined in by configuration in the circuit of transducer 250 and realize this configuration PWM converter 240.
As shown in Figure 9, embodiment according to PWM converter 240 of the present invention will be described now.As shown in Figure 9, will the PWM converter be described and this PWM converter can be used as PWM converter 240 with reference to PWM converter 240.But, the invention is not restricted to this.
In the circuit arrangement of the PWM of Fig. 9 converter, be suitable for the level shift circuit that input voltage improves required level can be coupled to the input end of input PWM information.Level shift circuit can comprise NPN transistor Q1, PNP transistor Q2 and be coupled to transistor Q1 and the resistor R 1 of each end of Q2, R2, R3 and R4.Capacitor C1 can arrive node P, i.e. the output terminal of level shift circuit.Oscillator also can be coupled to node P.
According to the PWM converter embodiment of Fig. 9, the PWM information that is input to the input end of level shift circuit can improve the required voltage level, thereby uses in the signal processing operations of oscillator.PWM information is being input in the situation of node P, it can be directly used in the signal processing operations of oscillator.
Can comprise OP amplifier U1 and resistor R 12, R13 and R14 via the oscillator that resistor R 5 is coupled to node P, they are used for the voltage of dispensing applications to the input end of OP amplifier U1.OP amplifier U1 can have the output terminal that is coupled to PNP transistor Q3 via resistor R 9.OP amplifier U1 can also have via resistor R 5 and is coupled to node P and is coupled to the conversion end of ground capacitor C2.Resistor R 6 can be coupling between the conversion end and transistor Q3 of OP amplifier U1.
Oscillator preferably is fit to produce the oscillation frequency according to the PWM information change.Transistor Q3 can be used for forming discharge loop (discharge loop) and is used for when the sawtooth wave of oscillator generation drops to low level the charging voltage of capacitor C2 being reduced fast.
The PWM information that is applied to node P can be input to the input end of OP amplifier U2.OP amplifier U2 can receive brilliance control information at its another input end.Brilliance control information can be input to OP amplifier U2 via the resistor R 18 that is used for voltage distribution and R20, grounding resistor R21 and capacitor C20.OP amplifier U2 is preferably used as comparer.
Use description to the operation of device embodiment of the brightness of control chart 8 displays (for example transducer PWM frequency of LCD).Portable set such as notebook and PDA can adopt a kind of method, and wherein according to the environment of the system that uses LCD, the frame frequency of LCD is variable.But, in the process that changes the LCD frame frequency, may have problems and shortcoming.In an embodiment according to the present invention, relevant with this LCD Frame-rate Control, correspondingly control is used to control the transducer PWM frequency of LCD lamp brightness.Preferably, can control automatically or directly control change device PWM frequency with the bucking-out system environment.
According to embodiments of the invention, at first the system environments of LCD220 is used in identification.For the identification of system environments, determine system interference or noise whether influence the LCD frame frequency or with its interaction.System noise can comprise the interference of any frequency generator, electronic unit or connecting interface or the like in power adapters, the portable computer.For example, the device that is used to control brightness can detect whether be coupled AC power supplies or battery as power supply.Preferably, portable computer, for example microcomputer 20a can the recognition system environment, will send to CPU10 via bus about the information of the system environments discerned subsequently.
At the frame frequency of determining under current system environments, to regulate LCD220 (for example, reduce system interference or noise) situation in, refresh rate controller 200 can control of video controller 210 so that change the frame frequency (for example, from 60Hz to 57Hz or from 57Hz to 45Hz) of LCD220.Refresh rate controller 200 can output to brightness controller 230 with monochrome information with the frame frequency that changes.
Brightness controller 230 can calculate the PWM frequency that will not disturb frame frequency according to the frame frequency that slave controller 200 receives, and handle the PWM frequency of being calculated so that produce PWM information (for example, dc voltage level or working time duty cycle control signal specific or institute's selected frequency).The PWM information that brightness controller 230 produces can output to PWM converter 240.The monochrome information that brightness controller 230 preferred process slave controllers 200 receive, related with the PWM frequency of calculating, thereby keeping constant working time dutycycle, it produces brilliance control information (for example, the working time duty cycle control signal of dc voltage level or characteristic frequency).The brilliance control information that produces from brightness controller 230 can output to PWM converter 240.
PWM converter 240 can produce pwm signal (for example, reference sync signal), and it is required and makes transducer 250 produce the signal that is used to drive LCD lamp 260.The embodiment of Fig. 9 PWM converter can be used as PWM converter 240.But, the invention is not restricted to this.Pwm signal (for example, reference sync signal) can have by the frequency of determining from the pwm signal of brightness controller 230 outputs with by the working time dutycycle of determining from the brightness control signal of brightness controller 230 outputs.
In the embodiment of Fig. 9, the PWM converter can receiving inputted signal A and B output signal is outputed to transducer 250.As shown in Figure 9, input signal B can improve predetermined level by level shift circuit, is applied to subsequently on the node P.Oscillator can produce the oscillator signal that has according to being applied to the oscillation frequency of the signal change on the node P.Can be at the non-conversion end place of OP amplifier U2 reception oscillator signal and at the receiving inputted signal A of its conversion end place.OP amplifier U2 can compare two signals that receive mutually so that the output comparative result.
Thereby can design PWM converter 240 signal that OP amplifier U1 output has the frequency that changes between 150Hz and 300Hz when input signal B has 0 to 3V voltage level.In this case, output signal frequency has the variation range of 150Hz, thereby for the variation of 0.01V among the input signal B and change 0.5Hz.Like this, become 150Hz, become 151Hz for 0.02V for the input signal B output signal frequency of 0V, become 152Hz for 0.04V, ..., become 200Hz for 1V, become 201Hz for 1.02V, ..., become 250Hz for 2V, become 251Hz for 2.02V ..., become 299Hz for 251Hz, and become 300Hz for 3V.
In addition, be changed to 57Hz or when 57Hz changes to 45Hz from 60Hz at the frame frequency of LCD220, can following selection that is used for brilliance control or the best PWM frequency of determining can not disturb frame frequency:
For 60Hz,
{(60×1)+(60/2)}＝90，{(60×2)+(60/2)}＝150，
{(60×3)+(60/2)}＝210，{(60×4)+(60/2)}＝270，
{(60×5)+(60/2)}＝330，...
For 57Hz,
{(57×1+(57/2)}＝85.5，{(57×2)+(57/2)}＝142.5，
{(57×3)+(57/2)}＝199.5，{(57×4)+(57/2)}＝256.5，
{(57×5)+(57/2)}＝313.5，...
For 45Hz,
{(45×1)+(45/2)}＝67.5，{(45×2)+(45/2)}＝112.5，
{(45×3)+(45/2)}＝157.5，{(45×4)+(45/2)}＝202.5，
{(45×5)+(45/2)}＝247.5，...
Because the variation range of PWM frequency can be set in 150Hz between the 300Hz, for the frame frequency of 60Hz, selectable optimum frequency can be 270Hz in frequency range, is 256.5Hz for 57Hz, and is 202.5Hz for 45Hz.
Equally, can calculate and make oscillator export the required input dc voltage level of this best PWM frequency (for example, being 2.4V for the frame frequency of 60Hz, is 2.13V for 57Hz, and be 1.05V for 45Hz).Therefore, input dc voltage level can be corresponding to the PWM information that is input to PWM converter 240.This dc voltage level can directly be exported from brightness controller 230.Perhaps, the dc voltage level can be with the form output of PWM frequency working time duty cycle control signal.In the latter's situation, after carrying out the DC rectification, can use this control signal.Brightness controller 230 can be handled PWM information according to the LCD frame frequency of the change that receives from refresh rate controller 200, and the PWM information that will handle outputs to PWM converter 240.
According to this process, the PWM frequency that can control the frame frequency of LCD and transducer is simultaneously associated with each other.Like this, be in the situation of 60Hz at the frame frequency of LCD display 220, brightness controller 230 can be exported 2.4V as PWM information.PWM converter 240 receives the voltage of 2.4V and exports the pwm signal of 270Hz.Pwm signal is imported into transducer 250, the signal with waveform shown in Figure 10 can be outputed to LCD lamp 260 subsequently, this waveform and synchronous waveform from the pwm signal of PWM converter 240 input.In this case, the value of annoyance level between expression pwm signal and the frame frequency, promptly f is 30 (they being f=30) (for example, 4 times at the PWM of 270Hz frequency and 60Hz are the gap that 30Hz is arranged between the 240Hz).Therefore, this situation satisfies condition " f＞15 ", thus the brightness of control LCD lamp 260 in steady state operation.
In addition, be in the situation of 57Hz at the frame frequency of LCD display 220, brightness controller 230 can be exported 2.13V as PWM information.PWM converter 240 receives the voltage of 2.13V, and can export the pwm signal of 256.5Hz.Pwm signal is imported into transducer 250, the signal with waveform shown in Figure 10 can be outputed to LCD lamp 260, the synchronous waveform of this waveform and pwm signal subsequently.In this case, value f be 28.5 (f=28.5) (for example, the PWM frequency of 256.5Hz and 57Hz 5 times, i.e. 285Hz, between the gap of 28.5Hz is arranged).Therefore, this situation satisfies condition " f＞15 ", thus the brightness of control LCD lamp 260 in steady state operation.
In addition, be in the situation of 45Hz at the frame frequency of LCD display 220, brightness controller 230 can be exported 1.05V as pwm signal.PWM converter 240 receives the voltage of 1.05V and can export the pwm signal of 202.5Hz.Pwm signal is input to transducer 250, the signal with waveform shown in Figure 10 can be outputed to LCD lamp 260, the synchronous waveform of this waveform and pwm signal subsequently.In this case, value f be 22.5 (f=22.5) (for example, 202.5Hz and 45Hz 5 times, i.e. 225Hz, between the gap of 22.5Hz is arranged).Therefore, this situation satisfies condition " f＞15 ", thus the brightness of control LCD lamp 260 in steady state operation.
Perhaps, brightness controller 230 or microcomputer 20a can canned datas, such as the exemplary tabulation of the appointment dc voltage related with the LCD refresh rate, so that select required or best PWM frequency, as shown in figure 11.In this case, can use the associated data (for example Figure 11 of exemplary) of storage to derive selected PWM frequency.In addition, can manage and/or store the value of being stored by other element (such as transducer (transducer 33)) of portable computer.
Therefore, control Fig. 8 devices and methods therefor of the brightness in the display of portable computer according to the present invention and can realize the figure pattern transducer, it is used to detect the frame frequency of the change of LCD, and the PWM frequency of direct or automatic control change device, be suitable for controlling the brightness of LCD, thereby it does not disturb with the frame frequency that changes.Therefore, can be such as the device of the portable computer that comprises LCD according to system environments with variable frame frequency pattern operation LCD.
As mentioned above, the embodiment of apparatus and method that is used to control the transducer PWM frequency of LCD according to the present invention has various advantages.These embodiment can change the transducer PWM frequency that control is used for brilliance control according to the frame frequency of LCD, so that the interference between minimizing or prevention frame frequency and the transducer PWM frequency.Therefore, can reduce or stop the deterioration that produces picture quality among the LCD.In addition, embodiment can be with variable frequency and fixed frequency as transducer PWM frequency, and can provide the PWM frequency to satisfy each characteristic of various LCD and/or system environments when using single inverter.Can in the controller of portable computer or PWM converter, directly or indirectly (for example use the voltage of determining) and determine the PWM frequency.In addition, can be applied in any product that uses LCD, for example such as the portable set of notebook or PDA, desk-top computer or mobile display according to embodiments of the invention.
In this instructions to " this embodiment ", " embodiment ", the referential expression of " example embodiment " etc. is in conjunction with the certain features, structure or the characteristic that are included in the embodiment at least one embodiment of the invention.The description of each paragraph of instructions in everywhere needn't all relate to same embodiment.In addition, when the arbitrary embodiment of contact described certain features, structure or characteristic, they all realized this characteristics, structure or characteristic to get in touch other embodiment in those of skill in the art's the understanding scope in the present technique field.In addition, for the ease of understanding, the ad hoc approach process can be depicted step separately as; But these steps described separately should not be constrained in it is carried out must depend on a definite sequence.That is, some step can be carried out with optional order, while or alternate manner.
Previous embodiment and advantage only be exemplary and unrestricted the present invention.The present technique explanation can be applied on the device of other type easily.It is illustrative that description of the invention is intended to, and does not limit the scope of claims.Many possibilities, modifications and variations are conspicuous for those skilled in the art in the present technique field.In claims, device adds and covers described structure when the function phrase is intended to carry out described function.
Claims (31)
1. a device that is used to control width modulation (PWM) frequency of LCD (LCD) is characterized in that, comprising:
Control device, it is used for changing according to system environments the LCD frame frequency of LCD, and is used for the information of LCD transducer according to the LCD frame frequency output that changes;
The PWM conversion equipment is used for the pwm signal according to the information generation LCD transducer that receives from described control device; And
Drive unit is used for converting input voltage to its waveform and the synchronous signal of pwm signal that receives from the PWM conversion equipment.
2. device as claimed in claim 1 is characterized in that, the electronic interferences in the detected system environments of described system environments.
3. device as claimed in claim 2 is characterized in that, described detected electronic interferences produces the voltage adapter that offers the alternating voltage of described device certainly or be coupled to described device.
4. device as claimed in claim 3 is characterized in that, described detected electronic interferences produces from the various signals that influence the LCD frame frequency.
5. device as claimed in claim 2 is characterized in that, Video Controller changes refresh rate to compensate detected electronic interferences.
6. device as claimed in claim 1 is characterized in that, described control device comprises:
The refresh rate control device is used to control the LCD frame frequency and exports controlled frame frequency information together with the brilliance control information of LCD lamp; And
Brightness controlling device is used for the control frame frequency information calculations PWM information that basis receives from the refresh rate control device, and exports the PWM information that calculates together with the brilliance control information that the refresh rate controller receives.
7. device as claimed in claim 6 is characterized in that, also comprises:
Video control device is used for outputing to according to the frame frequency information Control that receives from the refresh rate control device vision signal of LCD.
8. device as claimed in claim 6 is characterized in that, described refresh rate control device changes the frame frequency of LCD according to system environments.
9. device as claimed in claim 1 is characterized in that, described information is the value corresponding to the frequency of not disturbing the LCD frame frequency.
10. device as claimed in claim 9 is characterized in that, described information is the value of calculating PWM information and according to estimated rate the PWM information translation that is calculated being obtained by based on frame frequency.
11. device as claimed in claim 10 is characterized in that, described PWM information is to export with the form of DC level.
12. device as claimed in claim 9 is characterized in that, described information is by frame frequency being multiply by 4.5 and the value that income value conversion obtained according to estimated rate.
13. device as claimed in claim 9 is characterized in that, the described PWM conversion equipment information of its value in preset range that conversion is received according to estimated rate, thus pwm signal has the frequency in the scheduled frequency range.
14. device as claimed in claim 13, it is characterized in that, the described pwm signal that is generated by drive unit is based on the brilliance control information that receives from control device and produces, and wherein the PWM conversion equipment is according to the working time dutycycle of the brilliance control information Control pwm signal that receives.
15. device as claimed in claim 1 is characterized in that, described PWM conversion equipment comprises:
Frequency outputting device is used to export the signal that has with the corresponding frequency of information that receives from control device; And
Comparison means, the brilliance control information that is used for relatively receiving from the signal of frequency outputting device output with from control device is so that output pwm signal.
16. device as claimed in claim 15 is characterized in that, described PWM conversion equipment comprises level moving device, and the PWM information that it is used for receiving from control device promotes predetermined level.
17. device as claimed in claim 1 is characterized in that, comprising:
LCD is used for according to the frame frequency display video signal; And
The LCD lamp is used for the back lighting of LCD, and wherein said drive unit is a transducer.
18. device as claimed in claim 17 is characterized in that, described LCD is applied in the portable set.
19. a method that is used to control inverter pulse width modulation (PWM) frequency of LCD (LCD) is characterized in that, comprising:
The frame frequency of identification LCD, and according to the frame frequency output PWM information that identifies; And
Brilliance control information based on described PWM information and LCD lamp generates pwm signal.
20. method as claimed in claim 19 is characterized in that, described identification is selected a frame frequency in a plurality of frame frequencies according to system environments.
21. method as claimed in claim 20 is characterized in that, the electronic interferences in the detected system environments of described system environments, wherein detected electronic interferences be by the AC voltage that offers system or be coupled in the voltage adapter of system one produce.
22. method as claimed in claim 19 is characterized in that, comprises that the input voltage that will receive from power supply converts the signal that has with the synchronous waveform of pwm signal to.
23. method as claimed in claim 22 is characterized in that, described PWM information is corresponding to the value of not disturbing the frequency of frame frequency substantially, and described noiseless frequency is corresponding to a frequency by the converted pwm signal of input voltage.
24. method as claimed in claim 23 is characterized in that, described PWM information is by multiply by frame frequency 4.5 and according to estimated rate income value conversion is obtained, and wherein PWM information is exported with the form of DC level.
25. method as claimed in claim 19 is characterized in that, described generation comprises according to estimated rate changes the PWM information of its value in preset range, the pwm signal that has the frequency in the scheduled frequency range with generation.
26. method as claimed in claim 25 is characterized in that, described brilliance control information is used to control the working time dutycycle of pwm signal.
27. method as claimed in claim 19 is characterized in that, described generation comprises:
PWM information is promoted predetermined level;
Export first signal, this signal has the frequency corresponding to the PWM information that promotes; And
First signal and brilliance control information are compared with output pwm signal.
28. method as claimed in claim 19 is characterized in that, comprises the frame frequency that changes LCD.
29. method as claimed in claim 28 is characterized in that, changes described frame frequency under only battery-powered system environments.
30. a device that is used to control inverter pulse width modulation (PWM) frequency of LCD (LCD) is characterized in that, comprising:
Controller, be used for according to system environments select LCD a plurality of different frame frequencies each and according to the selected frame frequency output PWM information of LCD lamp; And
The PWM converter is used for generating pwm signal according to PWM information.
31. device as claimed in claim 30, it is characterized in that, comprise a transducer, it is configured to convert input voltage to have with from the synchronous waveform of the pwm signal of PWM converter reception signal, and wherein said pwm signal is based on the brilliance control information of the LCD lamp of slave controller reception.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020030034498 | 2003-05-29 | ||
| KR10-2003-0034498A KR100537680B1 (en) | 2003-05-29 | 2003-05-29 | Apparatus and method controlling invertor pulse width modulation frequency in LCD |
| KR10-2003-0034498 | 2003-05-29 |
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| Publication Number | Publication Date |
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| CN1573893A true CN1573893A (en) | 2005-02-02 |
| CN100367148C CN100367148C (en) | 2008-02-06 |
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| CNB2004100474860A Expired - Fee Related CN100367148C (en) | 2003-05-29 | 2004-05-28 | Apparatus and method for controlling inverter pulse width modulation frequency in LCD in portable computer |
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| KR (1) | KR100537680B1 (en) |
| CN (1) | CN100367148C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103187034A (en) * | 2011-12-31 | 2013-07-03 | 昂宝电子（上海）有限公司 | Signal synchronization system and signal synchronization method for driving light-emitting diodes |
| CN109256098A (en) * | 2018-11-22 | 2019-01-22 | 京东方科技集团股份有限公司 | driving method, driving device and display device |
| CN113823245A (en) * | 2021-09-08 | 2021-12-21 | 富奥汽车零部件股份有限公司 | Display screen brightness control method, control device and readable storage medium |
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| KR100673689B1 (en) * | 2003-03-20 | 2007-01-23 | 엘지전자 주식회사 | Inverter pulse width modulation frequency control device and method in portable computer |
| KR100686036B1 (en) * | 2005-01-19 | 2007-02-23 | 엘지전자 주식회사 | Monitor's noise prevention device |
| KR100743759B1 (en) * | 2005-09-07 | 2007-07-30 | 엘지전자 주식회사 | Apparatus and method for controlling dynamic contrast ratio using autocorrelation function |
| KR101227284B1 (en) * | 2006-01-17 | 2013-02-07 | 엘지전자 주식회사 | Apparatus and Method Controlling Dimming Frequency in LCD |
| KR101243160B1 (en) * | 2006-08-23 | 2013-03-14 | 엘지디스플레이 주식회사 | Inverter driving circuit and method of liquid crystal display |
| KR100826013B1 (en) | 2006-09-27 | 2008-04-28 | 엘지전자 주식회사 | Apparatus and method for improving image quality of image display equipment |
| KR101311671B1 (en) * | 2006-11-30 | 2013-09-25 | 엘지디스플레이 주식회사 | Liquid Crystal Display Module |
| KR101334551B1 (en) | 2007-05-14 | 2013-11-28 | 엘지전자 주식회사 | Display apparatus and method of brightness control the same |
| KR101441955B1 (en) * | 2007-11-15 | 2014-09-18 | 엘지디스플레이 주식회사 | The inverter circuit of the liquid crystal display |
| KR20100020326A (en) | 2008-08-12 | 2010-02-22 | 삼성전자주식회사 | Method of driving light-source, light-source apparatus performing for the method and display apparatus having the light-source apparatus |
| KR101108173B1 (en) * | 2010-04-28 | 2012-02-09 | 삼성모바일디스플레이주식회사 | LCD, its driving device and driving method |
| KR102253677B1 (en) * | 2014-11-04 | 2021-05-21 | 엘지디스플레이 주식회사 | Display Device and Driving Method thereof |
| KR102510648B1 (en) * | 2021-04-28 | 2023-03-16 | 엘지전자 주식회사 | Display device and operating method thereof |
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| US5977942A (en) * | 1996-12-20 | 1999-11-02 | Compaq Computer Corporation | Multiplexed display element sequential color LCD panel |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103187034A (en) * | 2011-12-31 | 2013-07-03 | 昂宝电子（上海）有限公司 | Signal synchronization system and signal synchronization method for driving light-emitting diodes |
| US8947136B2 (en) | 2011-12-31 | 2015-02-03 | On-Bright Electronics (Shanghai) Co., Ltd. | Systems and methods of signal synchronization for driving light emitting diodes |
| CN109256098A (en) * | 2018-11-22 | 2019-01-22 | 京东方科技集团股份有限公司 | driving method, driving device and display device |
| CN109256098B (en) * | 2018-11-22 | 2021-01-26 | 高创(苏州)电子有限公司 | Driving method, driving device and display device |
| CN113823245A (en) * | 2021-09-08 | 2021-12-21 | 富奥汽车零部件股份有限公司 | Display screen brightness control method, control device and readable storage medium |
Also Published As
| Publication number | Publication date |
|---|---|
| KR20040103549A (en) | 2004-12-09 |
| KR100537680B1 (en) | 2005-12-20 |
| CN100367148C (en) | 2008-02-06 |
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