Background technology
General backlight liquid crystal display module adopts cathode fluorescent tube, and (Cold Cathode Fluorescent Lamp is CCFL) as light emitting source.When the cathode fluorescent tube stable operation, needed power supply is frequency range does not contain the direct current composition greatly about 30~80KHz a string ripple, wherein the stable operation voltage of fluorescent tube is close in constant, and the brightness of fluorescent tube is determined by the lamp current by fluorescent tube.In the application of reality, in the mode of the fixing operating frequency of fluorescent tube because can be than being easier to grasp the noise that is created on the fluorescent tube operating frequency, so general being used.But in the application of large scale liquid crystal display panel, because the quantity of fluorescent tube heightens, therefore the high frequency noise that is produced also heightens thereupon.Because the fluorescent tube two ends are to be high drive (about 1000 volts), therefore electromagnetic interference (EMI) (the Electro-Magnetic Interference that frequency converter and fluorescent tube produced, EMI) to influence that display pannel caused, add the sweep frequency of the operating frequency of frequency converter and gate pole driver when asynchronous, and make display frame the phenomenon of ripples line (waving) occur.Generally speaking, the horizontal stripe of ripples line for moving up and down, and the position that the ripples line is occurred on display panel is relevant with the operating frequency of frequency converter.
Please refer to the 1st figure, the 1st figure is that the polarity of the LCD utilization of the prior art driving voltage that changes fluorescent tube is to improve the synoptic diagram of ripples line.LCD 10 comprises a display panel 12, a frequency converter 14 and a plurality of fluorescent tube 16.Because the ripples line is relevant with the operating frequency of frequency converter, therefore can improve the phenomenon of ripples line by changing field effect.Utilize the polarity that changes 16 of fluorescent tubes, its two electric fields adjacent and that direction is different are subdued mutually, the polarity that fluorescent tube is 16 is arranged and is comprised following three kinds of situations:
One, " ++ ++ ++ ", the field effect maximum.
Two, " ++--++ ", field effect is general.
Three, "+-+-+-", field effect is lower.
Polarity between the fluorescent tube of the 1st figure is arranged as the third situation.The operating frequency that utilizes the polarity that changes between fluorescent tube to arrange and adjust frequency converter improves the phenomenon of ripples line, need to cooperate the visual lighter frequency converter operating frequency of ripples line that adjusts, the effect that makes electric field have to cancel out each other, and then improve the order of severity of ripples line.Yet, different display frame, the severe case of its water ripple phenomenon is also different, can't make the ripples line of all display frames all effectively improve so the mode of the operating frequency of frequency converter is arranged and adjusted to the polarity between the change fluorescent tube.
Please refer to the 2nd figure, the 2nd figure is that the LCD of prior art utilizes synchronizing frequency to improve the synoptic diagram of ripples line.LCD 20 comprises a display panel 22, a frequency converter 24, a plurality of fluorescent tube 26 and a synchronizing circuit 28.The operating frequency of fluorescent tube and the sweep frequency of gate pole driver also can be improved the phenomenon of ripples line synchronously, and be not subject to specific display frame.Synchronizing circuit 28 produces synchronizing frequency Sf according to the sweep frequency of gate pole driver, so frequency converter 24 can be according to the sweep frequency synchronous operating frequency Lf of synchronizing frequency Sf generation with gate pole driver.Yet because the design of synchronizing circuit 28 is complicated, the scope (being the sweep frequency of gate pole driver) of adding synchronizing frequency will be subject to the born frequency zone of frequency converter 24, and significantly reduce the application and the sharing of this framework.
Description of drawings
The 1st figure is that the polarity of the LCD utilization of the prior art driving voltage that changes fluorescent tube is to improve the synoptic diagram of ripples line.
The 2nd figure is that the LCD of prior art utilizes synchronizing frequency to improve the synoptic diagram of ripples line.
The 3rd figure is the synoptic diagram of first embodiment of LCD of the present invention.
The 4th figure to the 6 figure are the synoptic diagram of the installation site of first electric-field sensor of first embodiment and one second electric-field sensor.
The 7th figure is the synoptic diagram of second embodiment of LCD of the present invention.
The 8th figure is the synoptic diagram of installation site of the electric-field sensor of second embodiment.
Primary clustering symbol description in the accompanying drawing:
10,20,30,40 LCD
12,22,32,42 display panels
14,24,34,44 frequency converters
16,26,36,46 fluorescent tubes
28 synchronizing circuits
341,441 comparers
342,442 microcontrollers
381 first electric-field sensors
382 second electric-field sensors
48 electric-field sensors
S1 first magnitude of voltage
S2 second magnitude of voltage
The Sref reference voltage
The Sout output voltage
Embodiment
In the middle of instructions and claim, used some vocabulary to censure specific assembly.The person with usual knowledge in their respective areas should understand, and same assembly may be called with different nouns by manufacturer.This instructions and follow-up claim are not used as distinguishing the mode of assembly with the difference of title, but the benchmark that is used as distinguishing with the difference of assembly on function.Be to be an open term mentioned " comprising " in the middle of instructions and the follow-up request item in the whole text, so should be construed to " comprise but be not limited to ".In addition, " electric connection " speech is to comprise any indirect means that are electrically connected that directly reach at this.Therefore, be electrically connected at one second device, then represent this first device can be directly connected in this second device, or be connected to this second device indirectly through other device or connection means if describe one first device in the literary composition.
Please refer to the 3rd figure, the 3rd figure is the synoptic diagram of first embodiment of LCD of the present invention.LCD 30 comprises a display panel 32, a frequency converter 34, a plurality of fluorescent tube 36, one first electric-field sensor 381 and one second electric-field sensor 382.Frequency converter 34 comprises a comparer 341 and a microcontroller 342.Comparer 341 is used for the magnitude of voltage S2 that magnitude of voltage S1 that comparison first electric-field sensor 381 sensed and second electric-field sensor 382 are sensed.Microcontroller 342 can be adjusted the operating frequency of frequency converter 34 according to the output voltage Sout of comparer 341.The reason that LCD produces water ripple phenomenon comprises the electric field interference that liquid crystal is subjected to the driving voltage of fluorescent tube, and the sweep frequency of the operating frequency of fluorescent tube and gate pole driver is asynchronous, therefore, in the present embodiment, LCD 30 utilizes two electric-field sensors 381,382 to detect in the LCD highfield and weak electric field respectively, whether adjust the operating frequency of frequency converter 34 according to the highfield and the electric field difference decision of weak electric field again, and then improve the water ripple phenomenon of LCD 30.
Please refer to the 4th figure to the 6 figure, the 4th figure to the 6 figure are the synoptic diagram of the installation site of first electric-field sensor 381 of first embodiment and one second electric-field sensor 382.The polarity of the driving voltage of fluorescent tube 36 is arranged and is comprised following three kinds of situations:
One, shown in the 4th figure, " ++ ++ ++ ", the field effect maximum.
Two, shown in the 5th figure, " ++--++ ", field effect is general.
Three, shown in the 6th figure, "+-+-+-", field effect is lower.
Can influence electric field level because the polarity of the driving voltage of fluorescent tube 36 is arranged, the position of above-mentioned three kinds of situations produced highfield reaches weak electric field is all inequality.In the 4th figure, the arrangement mode of " ++ ++ ++ ", the position of highfield is directly over the fluorescent tube 36, just the installation site of first electric-field sensor 381, the position of weak electric field is the middle of any two fluorescent tubes 36, just the installation site of second electric-field sensor 382.In the 5th figure, the arrangement mode of " ++--++ ", the position of highfield is directly over the fluorescent tube 36, the installation site of first electric-field sensor 381 just, the position of weak electric field is adjacent and the middle of opposite two fluorescent tubes 36 of polarity, just the installation site of second electric-field sensor 382.In the 6th figure, "+-+-+-" arrangement mode, the position of highfield is directly over the fluorescent tube 36, the installation site of first electric-field sensor 381 just, the position of weak electric field is adjacent and the middle of opposite two fluorescent tubes 36 of polarity, just the installation site of second electric-field sensor 382.
When first electric-field sensor 381 and second electric-field sensor 382 are arranged decision behind the installation site on the display panel 32 according to the polarity of the driving voltage of fluorescent tube 36, first electric-field sensor 381 and second electric-field sensor 382 change into numerical value with the electric field intensity of sensing and are transmitted back to frequency converter 34, and this two numerical value is delivered to microcontroller 342 after relatively and feedback judgement.The operational frequency range of supposing frequency converter 34 is Δ f=fmax-fmin.When output voltage Sout during greater than a predetermined value A (Sout=|S1-S2|>A), microcontroller 342 will be adjusted the operating frequency of microcontroller 342, and the operating frequency that microcontroller 342 is adjusted frequency converters 34 can comprise for three stages:
Stage 1: in operational frequency range Δ f, adjusting frequency makes output voltage Sout less than predetermined value A.
Stage 2: scan operation frequency range Δ f, select in less than the respective frequencies of predetermined value A output voltage Sout to be hour pairing frequency at output voltage Sout.
Stage 3:, then select output voltage Sout to be hour pairing frequency if can't find and make the frequency of output voltage Sout in the operational frequency range Δ f less than predetermined value A.
When output voltage Sout is less than or equal to predetermined value A, (Sout=|S1-S2|≤A), microcontroller 342 will be adjusted the operating frequency of microcontroller 342, and the operating frequency that microcontroller 342 is adjusted frequency converter 34 can comprise the two-stage:
Stage 1: keep present operating frequency.
Stage 2: timing scan operational frequency range Δ f, select in less than the respective frequencies of predetermined value A output voltage Sout to be hour pairing frequency at output voltage Sout.
Because the size of predetermined value A is directly proportional with the order of severity of water ripple phenomenon (when predetermined value A=0, promptly not having water ripple phenomenon), so predetermined value A=0 can be considered as standard.It is all different that each stage that microcontroller 342 is adjusted the operating frequency of frequency converters 34 is improved the situation of ripples line, but the range of definition of predetermined value A is not to exceed average electric field value ± 5%.
Please refer to the 7th figure, the 7th figure is the synoptic diagram of second embodiment of LCD of the present invention.LCD 40 comprises a display panel 42, a frequency converter 44, a plurality of fluorescent tube 46 and an electric-field sensor 48.Frequency converter 44 comprises a comparer 441 and a microcontroller 442.Comparer 441 is used for a magnitude of voltage S and the reference voltage Sref that comparison electric-field sensor 48 is sensed.Microcontroller 442 can be adjusted the operating frequency of frequency converter 44 according to the output voltage Sout of comparer 441.In the present embodiment, LCD 40 utilizes single electric-field sensor 48 to detect the highfield of LCD 40, the position of usually highfield is the most serious and visibility point of water ripple phenomenon, whether microcontroller 442 adjusts the operating frequency of frequency converter 44 according to highfield decision, and then improves water ripple phenomenon.
Please refer to the 8th figure, the 8th figure is the synoptic diagram of installation site of the electric-field sensor 48 of second embodiment.In the present embodiment, electric-field sensor 48 is installed on the position of highfield, just directly over the fluorescent tube 46.The operational frequency range of supposing frequency converter 44 is Δ f=fmax-fmin.The output voltage Sout of comparer 441 is during greater than a predetermined value B (Sout=|S1-Sref|>B), microcontroller 442 will be adjusted the operating frequency of microcontroller 442, and the operating frequency that microcontroller 442 is adjusted frequency converters 44 can comprise for three stages:
Stage 1: in operational frequency range Δ f, adjusting frequency makes output voltage Sout less than predetermined value B.
Stage 2: scan operation frequency range Δ f, select in less than the respective frequencies of predetermined value B output voltage Sout to be hour pairing frequency at output voltage Sout.
Stage 3:, then select output voltage Sout to be hour pairing frequency if can't find and make the frequency of output voltage Sout in the operational frequency range Δ f less than predetermined value B.
When output voltage Sout is less than or equal to this predetermined value B, (Sout=|S1-Sref|≤B), microcontroller 442 will be adjusted the operating frequency of microcontroller 442, and the operating frequency that microcontroller 442 is adjusted frequency converter 44 can comprise the two-stage:
Stage 1: keep present operating frequency.
Stage 2: timing scan operational frequency range Δ f, select in less than the respective frequencies of predetermined value B output voltage Sout to be hour pairing frequency at output voltage Sout.
Because the size of predetermined value B is directly proportional with the order of severity of water ripple phenomenon (when predetermined value B=0, promptly not having water ripple phenomenon), so predetermined value B=0 can be considered as standard.It is all different that each stage that microcontroller 442 is adjusted the operating frequency of frequency converters 44 is improved the situation of ripples line, but the range of definition of predetermined value B is not to exceed average electric field value ± 5%.
Compared to prior art, the present invention does not need to cooperate and visually adjusts the slightest frequency converter operating frequency of ripples line, and the corresponding different operating frequency of different pictures, and water ripple phenomenon is all effectively improved.In addition, the present invention also need not complex circuit design and can improve water ripple phenomenon.
In sum, LCD of the present invention comprises a display panel, a plurality of fluorescent tube, an electric-field sensor and a frequency converter.This electric-field sensor is used for electric field that this a plurality of fluorescent tube of sensing produced to produce a magnitude of voltage.This frequency converter is electrically connected at this a plurality of fluorescent tubes, is used for producing a driving voltage to drive these a plurality of fluorescent tubes.This frequency converter can be adjusted the operating frequency of this driving voltage according to this magnitude of voltage.Therefore, this LCD can effectively be improved the phenomenon of ripples line.
The above only is preferred embodiment of the present invention, and all equalizations of being done according to the present patent application claim change and modify, and all should belong to covering scope of the present invention.