CN102201207B - Method and device for eliminating bias voltage of source driving device of liquid crystal display (LCD) - Google Patents
Method and device for eliminating bias voltage of source driving device of liquid crystal display (LCD) Download PDFInfo
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- CN102201207B CN102201207B CN 201010141287 CN201010141287A CN102201207B CN 102201207 B CN102201207 B CN 102201207B CN 201010141287 CN201010141287 CN 201010141287 CN 201010141287 A CN201010141287 A CN 201010141287A CN 102201207 B CN102201207 B CN 102201207B
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- driving device
- signal
- isolating switch
- source electrode
- electrode driving
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- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
Abstract
The invention relates to a method used for a liquid crystal display (LCD) to eliminate a bias voltage of a source driving device. The source driving device comprises at least one circuit breaker. The method comprises the following steps: measuring the equivalent load resistor and equivalent load capacitor of a panel of the LCD relative to the source driving device; calculating the lowest effective frequency of the at least one circuit breaker according to the equivalent load resistor and the equivalent load capacitor; and adjusting at least one switch frequency of the at least one circuit breaker according to the lowest effective frequency so as to carry out low-pass filtering on signals output by the source driving device by virtue of the panel and further eliminate the bias voltage.
Description
Technical field
The present invention relates to a kind ofly eliminate method and the device of the bias voltage of source electrode driving device for liquid crystal indicator, relate in particular to a kind of panel by liquid crystal indicator, bias voltage is carried out method and the device of low-pass filtering.
Background technology
Liquid crystal indicator (Liquid Crystal Display, LCD) have that external form is frivolous, power consumption is few and a characteristic such as radiationless pollution, replace gradually traditional cathode-ray tube (CRT) (Cathode Ray Tube, CRT) display, and be widely used on the information products such as notebook, personal digital assistant (PersonalDigital Assistant, PDA), flat-surface television or mobile phone.The principle of work of liquid crystal indicator is to utilize liquid crystal molecule under different ordered states, light had different polarizations or refraction effect, therefore can control via the liquid crystal molecule of different ordered states the amount of penetrating of light, further produce the output light of varying strength, and the red, green, blue of different GTG intensity.
In order to control the arrangement of liquid crystal molecule corresponding to each pixel in the liquid crystal indicator, liquid crystal indicator comprises source electrode driving device usually, is used for applying control voltage in pixel, with light penetration amount and the GTG intensity of controlling this pixel.Please refer to Fig. 1, Fig. 1 is the synoptic diagram of known source electrode driving device 10.Source electrode driving device 10 is used for driving the pixel of panel 100 lastrows (column) of liquid crystal indicator, for example the pixel P1 among Fig. 1, P2 ..., PN.Source electrode driving device 10 includes receiving end 102, the first isolating switch (chopper) 104, gain operational amplifier 106, the second isolating switch 108, output operational amplifier 110 and low-pass filter 112.Receiving end 102 is used for receiving chrominance signal clr according to the presentation content of wish demonstration.The first isolating switch 104 is used for according to the first switching signal SW1 of external control circuit generation, and whether control exports chrominance signal clr to gain operational amplifier 106.Gain operational amplifier 106 is used for amplifying the clr chrominance signal that the first isolating switch 104 is exported, to produce gain amplifier signal CLR.Similarly, the second isolating switch 108 is used for according to second switch signal SW2, and whether control exports gain amplifier signal CLR to output operational amplifier 110.Output operational amplifier 110 is used for according to gain amplifier signal CLR, output source drive signal V_S.At last, 112 pairs of source drive signals of low-pass filter V_S carries out low-pass filtering, does not mate the bias voltage that produces because of assembly to eliminate source drive signal V_S.
In simple terms, source electrode driving device 10 is amplified to correct driving voltage level by gain operational amplifier 106 with chrominance signal clr, and by output operational amplifier 110 provide the buffering and better output impedance, with according to sweep signal scan_1, scan_2 ..., scan_N, sequentially correctly drive pixel P1, P2 ..., PN.Yet, in order to eliminate the bias voltage of source drive signal V_S, must use large-scale circuit area to realize low-pass filter 112, significantly, do not meet economic benefit.
Therefore, such as how more economical method, the bias voltage of eliminating the source drive signal has become the effort target of industry member.
Summary of the invention
Therefore, fundamental purpose of the present invention namely is to provide a kind of method and device of bias voltage of the source electrode driving device that is used for eliminating liquid crystal indicator.
The present invention discloses and a kind ofly eliminates the method for the bias voltage of source electrode driving device for liquid crystal indicator, and this source electrode driving device comprises at least one isolating switch.The method includes the panel of measuring this liquid crystal indicator with respect to equivalent load resistance and the equivalent load capacitance of this source electrode driving device; According to this equivalence pull-up resistor and this equivalence load capacitance, calculate the minimum effective frequency of this at least one isolating switch; And according to this minimum effective frequency, adjust at least one switching frequency of this at least one isolating switch, carry out low-pass filtering with the signal of this source electrode driving device being exported by this panel, and then eliminate this bias voltage.
The present invention also discloses a kind of source electrode driving device, is used for liquid crystal indicator output source drive signal to panel.This source electrode driving device includes receiving end, is used for receiving chrominance signal; Output terminal is coupled to this panel, is used for exporting this source drive signal; The first isolating switch is used for according to the first switching signal, this chrominance signal that this receiving end of control output receives; Gain circuitry is used for amplifying this chrominance signal that this first isolating switch is exported, to produce the gain amplifier signal; The second isolating switch is used for according to the second switch signal, this gain amplifier signal that this gain circuitry of control output produces; And output circuit, be used for according to this gain amplifier signal, export this source drive signal to this panel.
Cooperate detailed description and claims of following diagram, embodiment at this, with on address other purpose of the present invention and advantage and be specified in after.
Description of drawings
Fig. 1 is the synoptic diagram of known source electrode driving device.
Fig. 2 is the synoptic diagram of the flow process of the embodiment of the invention.
Fig. 3 A and Fig. 3 B are for when source electrode driving device is connected on the panel pixel, and panel is with respect to the synoptic diagram of the equivalent electrical circuit of source electrode driving device.
Fig. 4 is the synoptic diagram of the source electrode driving device of the embodiment of the invention.
Fig. 5 be Fig. 4 source electrode driving device internal signal the time become synoptic diagram.
Wherein, description of reference numerals is as follows:
Clr chrominance signal CLR gain amplifier signal
CLD_E equivalent load capacitance RLD_E load equivalent resistance
P1, P2, PN, PM pixel PIX cross-pressure
LPF1 low-pass filter scan_1, scan_2, scan_N, scan_M sweep
Retouch signal
SW1 the first switching signal SW2 second switch signal
T1, T2, T3 period TH threshold value
V_S source drive signal VOS offset voltage
V1, V2 voltage levvl
10,40 source electrode driving devices 100,400 panels
102,402 receiving ends 104,404 first isolating switchs
106 gain operational amplifiers 108,408 second isolating switchs
110 output operational amplifiers, 112 low-pass filters
20 flow processs 200,202,204,206,208 steps
300 panels coiling load, 302 pixel loads
406 gain circuitries, 410 output circuits
Embodiment
Please refer to Fig. 2, Fig. 2 is the synoptic diagram of the flow process 20 of the embodiment of the invention.Flow process 20 is used in liquid crystal indicator (Liquid Crystal Display, LCD), the bias voltage of the source drive signal that the elimination source electrode driving device is exported.Wherein, source electrode driving device comprises at least one isolating switch (chopper).Flow process 20 includes the following step:
Step 200: beginning.
Step 202: measure the panel of liquid crystal indicator with respect to equivalent load resistance and the equivalent load capacitance of source electrode driving device.
Step 204: according to equivalent load resistance and equivalent load capacitance, calculate the minimum effective frequency of isolating switch.
Step 206: according to minimum effective frequency, adjust at least one switching frequency of at least one isolating switch, carry out low-pass filtering with the source drive signal of source electrode driving device being exported by panel, and then eliminate bias voltage.
Step 208: finish.
Because the equivalent electrical circuit of the panel of liquid crystal indicator can be considered low-pass filter, flow process 20 is measured equivalent load resistance and the equivalent load capacitance of panel, with cut-off (cut-off) frequency of calculating this low-pass filter, namely above-mentioned minimum effective frequency.Thus, just can adjust the switching frequency of isolating switch according to minimum effective frequency, and then eliminate the bias voltage of source drive signal by panel.
Specifically, please refer to Fig. 3 A, Fig. 3 A is for when source electrode driving device is connected on the panel pixel, and panel is with respect to the schematic equivalent circuit of source electrode driving device.According to the circuitry principle, in Fig. 3 A, panel coiling (routing line) load 300 and pixel load 302 can be merged into the load equivalent resistance R
LD_EAnd equivalent load capacitance C
LD_E, shown in Fig. 3 B.Therefore, the cutoff frequency of the low-pass filter of Fig. 3 B, namely minimum effective frequency f
LVCan be expressed as f
LV=1/ (2 * R
LD_E* C
LD_E).
That is to say that by the switching manipulation of isolating switch, source electrode driving device can make the oscillation frequency of bias voltage follow the switching frequency of (follow) isolating switch.Thus, when switching frequency during greater than minimum effective frequency, panel (low-pass filter) can be by carrying out low-pass filtering to the source drive signal, and the oscillation-damped frequency is higher than the bias voltage of cutoff frequency.In other words, the switching frequency of isolating switch must be more than or equal to minimum effective frequency.
Implementation about flow process 20 please refer to Fig. 4, and Fig. 4 is the synoptic diagram of the source electrode driving device 40 of the embodiment of the invention.Source electrode driving device 40 is used for liquid crystal indicator output source drive signal V_S to panel 400, be used for according to sweep signal scan_1, scan_2 ..., scan_M, sequentially drive panel 400 lastrows (column) pixel P1, P2 ..., PM.Source electrode driving device 40 includes receiving end 402, the first isolating switch 404, gain circuitry 406, the second isolating switch 408 and output circuit 410.Receiving end 402 is used for receiving chrominance signal clr according to the presentation content of wish demonstration.The first isolating switch 404 is used for according to the first switching signal SW1 of external control circuit generation, and whether control exports chrominance signal clr to gain circuitry 406.Then, gain circuitry 406 amplifies the clr chrominance signal that the first isolating switch 404 is exported, to produce gain amplifier signal CLR.Similarly, the second isolating switch 408 is used for according to second switch signal SW2, and whether control exports gain amplifier signal CLR to output circuit 410.At last, output circuit 410 is used for according to gain amplifier signal CLR, and output source drive signal V_S is to panel 400.
In simple terms, compare with known source electrode driving device 10, source electrode driving device 40 is by the switching frequency of modulation the first isolating switch 404 and the second isolating switch 408, so that panel 400 has the function (low-pass filtering) of the bias voltage of eliminating source drive signal V_S, and then omit the low-pass filter 112 in the source electrode driving device 10.Thus, the side circuit area of source electrode driving device 40 can reduce significantly, and then reaches the purpose that reduces manufacturing cost.
Specifically, please refer to Fig. 5, Fig. 5 be source electrode driving device 40 internal signal the time become synoptic diagram.In Fig. 5, period T1, T2, T3 ... represent that respectively source drive signal V_S is used for driving pixel P1, P2, P3 ... period.There is offset voltage VOS in the impact of the non-ideal factor such as be subjected to that assembly does not mate among the source drive voltage V_S, cause source drive voltage V_S to vibrate near desirable voltage levvl V1, V2.Yet when source electrode driving device 40 was connected to arbitrary pixel on the panel 400, for source electrode driving device 40, the load effect of panel 400 can be considered low-pass filter LPF1, as shown in Figure 4.Thus, after carrying out low-pass filtering through panel 400, the offset voltage VOS composition among the source drive voltage V_S is removed, so that the cross-pressure PIX at pixel two ends can level off to desirable voltage levvl V1, V2, as shown in Figure 5.
The explanation of source electrode driving device 40 correlative details, for example the restriction of isolating switch 404,408 switching frequency can with reference to aforementioned explanation to flow process 20, be not repeated herein.In addition, preferably, the first isolating switch 404 and the second isolating switch 408 determine according to the level of source drive signal V_S whether starting switch operates.That is to say that the first isolating switch 404 and the second isolating switch 408 only during greater than threshold T H, are carried out switching manipulation, as shown in Figure 5 at the absolute value of source drive signal V_S.Certainly, this area has common practise person can implement different control modes according to the actual requirements, does not for example interrupt the switching manipulation of the first isolating switch 404 and the second isolating switch 408 fully.
In known technology, source electrode driving device 10 is eliminated the bias voltage of source drive signal V_S by low-pass filter 112.Therefore, must use a large amount of circuit layout area to realize low-pass filter 112.In comparison, the present invention adjusts isolating switch 404,408 switching frequency, so that the oscillation frequency of offset voltage VOS can be followed switching frequency.Thus, only isolating switch 404,408 switching frequency must be controlled on the cutoff frequency (minimum effective frequency) of panel 400 (low-pass filter), just can eliminate offset voltage VOS to the impact of source drive signal V_S, and then reduce the manufacturing cost of source electrode driving device by omitting low-pass filter 112.
In sum, the present invention is considered as low-pass filter with the panel of liquid crystal indicator, and the frequency control operation that collocation is corresponding can be used to replace the low-pass filter in the source electrode driving device, and then reduces the manufacturing cost of source electrode driving device.
The above only is the preferred embodiments of the present invention, and all equalizations of doing according to claim of the present invention change and modify, and all should belong to covering scope of the present invention.
Claims (4)
1. one kind is used for the method that liquid crystal indicator is eliminated the bias voltage of source electrode driving device, and this source electrode driving device comprises at least one isolating switch, it is characterized in that, the method includes:
Measure the panel of this liquid crystal indicator with respect to equivalent load resistance and the equivalent load capacitance of this source electrode driving device;
According to this equivalence pull-up resistor and this equivalence load capacitance, calculate the minimum effective frequency of this at least one isolating switch; And
According to this minimum effective frequency, adjust at least one switching frequency of this at least one isolating switch, carry out low-pass filtering with the signal of this source electrode driving device being exported by this panel, and then eliminate this bias voltage;
Wherein according to this minimum effective frequency, the step of adjusting this at least one switching frequency of this at least one isolating switch is to adjust this at least one switching frequency, so that this at least one switching frequency is more than or equal to this minimum effective frequency.
2. the method for claim 1 is characterized in that, this minimum effective frequency f
LV=1/ (2 * R
LD_E* C
LD_E), f wherein
LVRepresent this minimum effective frequency, R
LD_ERepresent this equivalence pull-up resistor, and C
LD_ERepresent this equivalence load capacitance.
3. a source electrode driving device is used for liquid crystal indicator output source drive signal to panel, it is characterized in that this source electrode driving device includes:
Receiving end is used for receiving chrominance signal;
Output terminal is coupled to this panel, is used for exporting this source drive signal;
The first isolating switch is used for according to the first switching signal, this chrominance signal that this receiving end of control output receives;
Gain circuitry is used for amplifying this chrominance signal that this first isolating switch is exported, to produce the gain amplifier signal;
The second isolating switch is used for according to the second switch signal, this gain amplifier signal that this gain circuitry of control output produces; And
Output circuit is used for according to this gain amplifier signal, exports this source drive signal to this panel;
Wherein the switching frequency of this first switching signal and this second switch signal is more than or equal to minimum row effect frequency, and this minimum effective frequency is f
LV=1/ (2 * R
LD_E* C
LD_E), f wherein
LVRepresent this minimum effective frequency, R
LD_EThe equivalent load resistance that represents this liquid crystal indicator, and C
LD_EThe equivalent load capacitance that represents this liquid crystal indicator.
4. source electrode driving device as claimed in claim 3 is characterized in that, this first isolating switch and this second isolating switch also are coupled to this source drive signal, is used for absolute value at this source drive signal during greater than a threshold value, carries out switching manipulation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201010141287 CN102201207B (en) | 2010-03-25 | 2010-03-25 | Method and device for eliminating bias voltage of source driving device of liquid crystal display (LCD) |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201010141287 CN102201207B (en) | 2010-03-25 | 2010-03-25 | Method and device for eliminating bias voltage of source driving device of liquid crystal display (LCD) |
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| Publication Number | Publication Date |
|---|---|
| CN102201207A CN102201207A (en) | 2011-09-28 |
| CN102201207B true CN102201207B (en) | 2013-01-02 |
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| CN 201010141287 Expired - Fee Related CN102201207B (en) | 2010-03-25 | 2010-03-25 | Method and device for eliminating bias voltage of source driving device of liquid crystal display (LCD) |
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| CN110728950B (en) * | 2018-07-16 | 2021-10-08 | 联咏科技股份有限公司 | Source driver |
| US20200152115A1 (en) * | 2018-11-08 | 2020-05-14 | Novatek Microelectronics Corp. | Source driver and related selector |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1855211A (en) * | 2005-04-27 | 2006-11-01 | 日本电气株式会社 | Active matric display device and its drive method |
| CN101042937A (en) * | 2007-04-24 | 2007-09-26 | 友达光电股份有限公司 | Displacement register capable of reducing voltage bias effective voltage |
| CN101359440A (en) * | 2007-07-31 | 2009-02-04 | 奇美电子股份有限公司 | Compensating circuit for improving threshold voltage off set and process thereof |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3813463B2 (en) * | 2000-07-24 | 2006-08-23 | シャープ株式会社 | Drive circuit for liquid crystal display device, liquid crystal display device using the same, and electronic equipment using the liquid crystal display device |
-
2010
- 2010-03-25 CN CN 201010141287 patent/CN102201207B/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1855211A (en) * | 2005-04-27 | 2006-11-01 | 日本电气株式会社 | Active matric display device and its drive method |
| CN101042937A (en) * | 2007-04-24 | 2007-09-26 | 友达光电股份有限公司 | Displacement register capable of reducing voltage bias effective voltage |
| CN101359440A (en) * | 2007-07-31 | 2009-02-04 | 奇美电子股份有限公司 | Compensating circuit for improving threshold voltage off set and process thereof |
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| CN102201207A (en) | 2011-09-28 |
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