CN100430992C - Output buffer circuit for drive voltage in liquid crystal display drive control chip - Google Patents
Output buffer circuit for drive voltage in liquid crystal display drive control chip Download PDFInfo
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- CN100430992C CN100430992C CNB2006100417068A CN200610041706A CN100430992C CN 100430992 C CN100430992 C CN 100430992C CN B2006100417068 A CNB2006100417068 A CN B2006100417068A CN 200610041706 A CN200610041706 A CN 200610041706A CN 100430992 C CN100430992 C CN 100430992C
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Abstract
The present invention discloses an output buffer circuit for driving voltage in a liquid crystal display drive control chip. A first stage amplifier is a difference transconductance stage circuit composed of MOS tubes (M1 to M5). A second stage amplifier is a common source stage amplifying circuit composed of an MOS tube (M9) and an MOS tube (M10), and a source stage follower of an MOS tube (M8) is added at an output terminal. Because the present invention adopts complementary type push-pull output circuits, one of the MOS tube (M9) and the MOS tube (M8) works at any time, and the other stops. When output voltage is stable, the MOS tube (M8) stops, and static bias current does not follow to the MOS tube (M8) and the static bias current of the MOS tube (M9) is only 0.2% of the static bias current in the prior art, which reduces the static power consumption of circuits; when the MOS tube (M8) stops, the present invention is only composed of two-stage amplifiers and has the advantages of good stability quality of systems, no phase compensation capacitor addition, saved chip areas and simple circuit structure.
Description
Technical field
The present invention relates to a kind of buffer circuit of output voltage, the output buffer of driving voltage in the particularly liquid crystal display drive controlling chip.
Background technology
With reference to Fig. 5～7, voltage VCOM is the extreme driving voltage of the common electrical of TFT-LCD display screen, and voltage VGOFF is the Gate shutoff voltage of non-scan line.Because VCOM voltage periodically changes between VCOMH and VCOML, corresponding VGOFF voltage periodically changes between VGOFFH and VGOFFL.Each pixel cell of TFT-LCD display screen is by thin film transistor (TFT) TFT, liquid crystal equivalent capacity C
LCWith keep capacitor C s to constitute, between the grid of thin film transistor (TFT) TFT and drain electrode, have stray capacitance Cgd in addition.When the capable Gate of N+1 when off state becomes conducting state, the Gate voltage of this row jumps to VGH by VGOFF.Because the capable Gate of N is in off state, therefore the capable Gate voltage jump of N+1 can pass through capable maintenance capacitor C s and the liquid crystal equivalent capacity C of N
LCForm feedback voltage, the extreme driving voltage VCOM of common electrical is raise; Pass through the feedback voltage of the stray capacitance Cgd formation of capable maintenance capacitor C s of N and thin film transistor (TFT) TFT in addition, the Gate shutoff voltage VGOFF of non-scan line is raise.In contrast, the Gate capable as N+1 becomes off state constantly from conducting state, the Gate voltage of this row jumps to VGOFF by VGH, can produce negative feedback voltage equally the Gate shutoff voltage VGOFF of extreme driving voltage VCOM of common electrical and non-scan line is reduced.Because the common electrical of multirow is extreme and Gate to hold be the output terminal that is connected to same VCOM and VGOFF output buffer, this output buffer that just requires these driving voltages has very strong inhibition ability to the interference of these feedback voltages.Usually the measure of taking is, at the external bigger electric capacity of voltage regulation of the output terminal of these output buffers, require output buffer can provide enough pull current and sink current that external electric capacity of voltage regulation is discharged and recharged simultaneously, make output buffer can both play normal voltage-regulation effect at any time, suppress the influence of feedback voltage, thereby keep outputting drive voltage stable.
With reference to Fig. 4, document " Allen P E; Holberg D R, CMOS Analog Circuit Design [M]. (2nd Ed). Beijing: Electronic Industry Press, 2002. " introduced the output buffer of driving voltage in a kind of liquid crystal display drive controlling chip.This circuit is made up of differential transconductance level, high-gain stage and the cascade of output buffer stage third stage amplifier, in order to increase the stability of output buffer, also needs to add phase compensating circuit.In order pull current and sink current to be provided for simultaneously external electric capacity of voltage regulation, the output buffer stage adopts complementary push pull configeration usually, because this output buffer structurally is provided with the parallel output channel that pull current and sink current is provided simultaneously, cause circuit structure complexity, quiescent bias current big, and cause power consumption big, the circuit chip occupying area is relatively large, in addition owing to form by the third stage amplifier cascade, the stability of circuit is relatively poor, needs to add bigger phase compensation electric capacity.
Summary of the invention
In order to overcome prior art output buffer complex structure, poor stability, deficiency that quiescent bias current is big, the invention provides the output buffer of driving voltage in a kind of liquid crystal display drive controlling chip.
The present invention solves the problems of the technologies described above the technical scheme that is adopted: the output buffer of driving voltage in a kind of liquid crystal display drive controlling chip, comprise differential transconductance level, output buffer stage and biasing circuit, output buffer for driving voltage VGOFFH, the differential transconductance level circuit formed by metal-oxide-semiconductor M1～M5 of first order amplifier wherein, the common-source stage amplifying circuit that second level amplifier is made up of metal-oxide-semiconductor M9 and metal-oxide-semiconductor M10; Output buffer for driving voltage VGOFFL, wherein first order amplifier is managed the differential transconductance level circuit that M1～M5 forms by PMOS, the common-source stage amplifying circuit that second level amplifier is made up of metal-oxide-semiconductor M9 and metal-oxide-semiconductor M10, it is characterized in that: the metal-oxide-semiconductor M8 source follower that also comprises output terminal, the unsteady biasing circuit that this source follower is made of metal-oxide-semiconductor M6 and metal-oxide-semiconductor M7 provides unsteady bias voltage V2, the common-source stage amplifying circuit that constitutes by metal-oxide-semiconductor M9 and metal-oxide-semiconductor M10 and form the complementary push-pull output circuit structure jointly by the source follower that metal-oxide-semiconductor M8 constitutes, metal-oxide-semiconductor M8 provides the path of releasing for output terminal feedback voltage, metal-oxide-semiconductor M9 and metal-oxide-semiconductor M8 provide pull current and sink current to load respectively, have only a pipe work among metal-oxide-semiconductor M9 and the metal-oxide-semiconductor M8 at any time, another pipe ends.
The invention has the beneficial effects as follows: because the present invention has adopted complementary push-pull output circuit, have only a pipe work among metal-oxide-semiconductor M9 and the metal-oxide-semiconductor M8 at any time, another ends, and quiescent bias current is smaller.1) when output voltage stabilization, metal-oxide-semiconductor M8 ends, and does not have quiescent bias current to flow through metal-oxide-semiconductor M8, and the quiescent bias current of metal-oxide-semiconductor M9 has only 0.2% of prior art quiescent bias current, and has reduced the quiescent dissipation of circuit; 2) when metal-oxide-semiconductor M8 ended, output buffer only was made up of two-stage amplifier, and the stability of system is good, does not need to add phase compensation electric capacity, has saved area of chip, and circuit structure is simple; 3) when output end voltage is subjected to the interference of feedback voltage, bigger pull current and sink current can instantaneously be provided, make output voltage can return to stationary value rapidly.
The present invention is further described below in conjunction with drawings and Examples.
Description of drawings
Fig. 1 is the output buffer block diagram of driving voltage in the liquid crystal display drive controlling chip of the present invention
Fig. 2 is the output buffer figure of driving voltage VGOFFH in the liquid crystal display drive controlling chip of the present invention
Fig. 3 is the output buffer figure of driving voltage VGOFFL in the liquid crystal display drive controlling chip of the present invention
Fig. 4 is the output buffer block diagram of driving voltage in the prior art liquid crystal display drive controlling chip
Fig. 5 is the connection layout of driving voltage VCOM and driving voltage Vgoff and TFT-LCD display screen in the liquid crystal display drive controlling chip
Fig. 6 is the oscillogram of driving voltage VCOM and driving voltage Vgoff in the liquid crystal display drive controlling chip
Fig. 7 is the equivalent electrical circuit of the adjacent two row pixels of TFT-LCD
Embodiment
With reference to Fig. 1～3, the output buffer of driving voltage provided by the invention comprises differential transconductance level and output buffer stage two-stage amplifier, adds biasing circuit.
The output voltage V 1 of differential transconductance level directly is added to the input end of common-source stage amplifying circuit, and the output terminal of the output terminal of common-source stage amplifying circuit and source follower links together, as the output terminal of output buffer.The output voltage V 1 of differential transconductance level is added in the unsteady biasing circuit of source follower simultaneously, produces the input end that the bias voltage V2 that floats is added to source follower.Biasing circuit provides fixing dc offset voltage VBIAS for differential transconductance level and output buffer stage.
The structure and the principle of work of the output buffer of four driving voltage VGOFFH, VGOFFL, VCOMH, VCOML are closely similar, are example explanation the present invention with the output buffer of driving voltage VGOFFH at first here.The present invention adopts low-power consumption Design of Simulating Circuits thought, be circuit when being in steady state (SS) quiescent bias current smaller, but moment provides bigger drive current when fluctuation appears in output voltage, regulates output voltage by negative feedback, makes it return to stationary value as early as possible.
The output buffer of driving voltage VGOFFH, the differential transconductance level circuit formed by metal-oxide-semiconductor M1～M5 of first order amplifier wherein, the common-source stage amplifying circuit that second level amplifier then is made up of metal-oxide-semiconductor M9 and metal-oxide-semiconductor M10 is to obtain higher gain and bigger voltage swing.The voltage negative feedback makes two stage amplifer form a unity gain amplifier.In order to improve the stability of output voltage, at the external bigger stable electric capacity Cout of output terminal, the value of this electric capacity is about 100 times of load capacitance normally.In addition, supply voltage VDD=0V, Vss=-15V.
In the amplifier of the second level, because metal-oxide-semiconductor M9 is large-sized PMOS pipe, it is as the driving tube of common-source stage amplifier, therefore has the bigger electric current fan-out capability of drawing.But because the bias current of metal-oxide-semiconductor M10 is less, the filling current capacity is more weak.In order to strengthen the filling current capacity of output circuit, increased the source follower of forming by large-sized metal-oxide-semiconductor M8 in addition at output terminal, the unsteady biasing circuit that is made of metal-oxide-semiconductor M6 and metal-oxide-semiconductor M7 provides unsteady bias voltage V2 for metal-oxide-semiconductor M8.The common-source stage amplifier that constitutes by metal-oxide-semiconductor M9 and formed the complementary push-pull output circuit structure like this by the source follower that metal-oxide-semiconductor M8 constitutes.But, be not subjected to the interference of feedback voltage when the output terminal of output circuit, be that output voltage V out is when stablizing, adjust the size of metal-oxide-semiconductor M6 and metal-oxide-semiconductor M7, making the bias voltage V2 of metal-oxide-semiconductor M8 be slightly larger than the threshold voltage of output voltage V out and metal-oxide-semiconductor M8 | VTH|'s is poor, guarantees that metal-oxide-semiconductor M8 is in cut-off state.For example: if output voltage V out=-8V, the threshold voltage of metal-oxide-semiconductor M8 | VTH|=0.7V, then bias voltage V2 should be greater than-7.3V.
The principle of work of whole output buffer is as follows: when output voltage stabilization, output voltage and input voltage approximately equal are owing to have the precision that very high open-loop gain has guaranteed output voltage.When output voltage V out reduces owing to the interference of negative feedback voltage, promptly when the Gate of next line voltage when VGH switches to VGOFF, negative feedback voltage appears, because the degenerative effect of voltage reduces voltage V1, the corresponding increase of the electric current of metal-oxide-semiconductor M9, circuit output this moment draws electric current to give external electric capacity of voltage regulation charging, and output voltage V out is raise, and output voltage V out returns to stationary value rapidly; In contrast, when output voltage V out raises owing to the interference of positive feedback voltage, positive feedback voltage appears when the Gate of next line voltage promptly when VGOFF switches to VGH, voltage V2 reduces, metal-oxide-semiconductor M8 conducting, output circuit provides the filling electric current, forms the discharge loop of external electric capacity of voltage regulation, output voltage V out is reduced also return to stationary value rapidly.Circuit did not provide and drew electric current because degenerative effect raises voltage V1, and metal-oxide-semiconductor M9 ends this moment.As output voltage V out during near normal stationary value, voltage V2 raises, and metal-oxide-semiconductor M8 ends.Therefore, the complementary push-pull formula output circuit that is made of metal-oxide-semiconductor M9 and metal-oxide-semiconductor M8 provides pull current and sink current for respectively external electric capacity of voltage regulation, and when positive and negative feedback voltage disturbance appearred in output terminal, output voltage can return to stationary value rapidly.
Output buffer with reference to driving voltage VGOFFL among Fig. 3.The difference of the output buffer of the output buffer of driving voltage VGOFFL and driving voltage VGOFFH is, input stage adopts the differential transconductance level circuit that is made of the PMOS pipe, so corresponding biasing circuit pipe and metal-oxide-semiconductor M8 are opposite with polarity in the VGOFFH output buffer.
The output buffer structure of the output buffer of driving voltage VCOML and VGOFFH is identical, is the supply voltage difference, VDD=5V in the output buffer of VCOMH, VSS=0V.
The output buffer structure of the output buffer of driving voltage VCOML and VGOFFL is identical, is the supply voltage difference, VDD=5V in the output buffer of VCOML, VSS=-3V.
Claims (1)
1, the output buffer of driving voltage in a kind of liquid crystal display drive controlling chip, comprise differential transconductance level, output buffer stage and biasing circuit, output buffer for driving voltage VGOFFH, the differential transconductance level circuit formed by metal-oxide-semiconductor M1～M5 of first order amplifier wherein, the common-source stage amplifying circuit that second level amplifier is made up of metal-oxide-semiconductor M9 and metal-oxide-semiconductor M10; Output buffer for driving voltage VGOFFL, wherein first order amplifier is managed the differential transconductance level circuit that M1～M5 forms by PMOS, the common-source stage amplifying circuit that second level amplifier is made up of metal-oxide-semiconductor M9 and metal-oxide-semiconductor M10, it is characterized in that: the metal-oxide-semiconductor M8 source follower that also comprises output terminal, the unsteady biasing circuit that this source follower is made of metal-oxide-semiconductor M6 and metal-oxide-semiconductor M7 provides unsteady bias voltage V2, the common-source stage amplifying circuit that constitutes by metal-oxide-semiconductor M9 and metal-oxide-semiconductor M10 and form the complementary push-pull output circuit structure jointly by the source follower that metal-oxide-semiconductor M8 constitutes, metal-oxide-semiconductor M8 provides the path of releasing for output terminal feedback voltage, metal-oxide-semiconductor M9 and metal-oxide-semiconductor M8 provide pull current and sink current to load respectively, have only a pipe work among metal-oxide-semiconductor M9 and the metal-oxide-semiconductor M8 at any time, another pipe ends.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2006100417068A CN100430992C (en) | 2006-01-20 | 2006-01-20 | Output buffer circuit for drive voltage in liquid crystal display drive control chip |
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| CNB2006100417068A CN100430992C (en) | 2006-01-20 | 2006-01-20 | Output buffer circuit for drive voltage in liquid crystal display drive control chip |
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| CN100430992C true CN100430992C (en) | 2008-11-05 |
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Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101441343B (en) * | 2007-11-21 | 2010-09-29 | 联咏科技股份有限公司 | Source pole follower |
| CN101826305B (en) * | 2009-03-02 | 2012-09-05 | 奇景光电股份有限公司 | Drive device and amplifier device with low power consumption and display device |
| CN101662264B (en) * | 2009-07-23 | 2012-10-17 | 复旦大学 | Switch-type operational amplifier with low power consumption and large oscillation range |
| US8508515B2 (en) * | 2009-08-05 | 2013-08-13 | Himax Technologies Limited | Buffering circuit with reduced dynamic power consumption |
| CN101788598A (en) * | 2009-11-25 | 2010-07-28 | 天津南大强芯半导体芯片设计有限公司 | Voltage peak detection circuit and operating method thereof |
| CN101826314B (en) * | 2010-03-10 | 2012-09-05 | 敦泰科技(深圳)有限公司 | Driving method and driving circuit of thin film transistor (TFT) liquid crystal display screen |
| CN103794188A (en) * | 2014-02-10 | 2014-05-14 | 北京京东方显示技术有限公司 | Output buffering circuit, array substrate and display device |
| CN106373534B (en) * | 2015-07-21 | 2021-01-12 | 国民技术股份有限公司 | Segment code liquid crystal and bias voltage generating circuit and method thereof |
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| CN1428756A (en) * | 1994-11-21 | 2003-07-09 | 精工爱普生株式会社 | Analog buffer and liquid crystal display device |
| US6756962B1 (en) * | 2000-02-10 | 2004-06-29 | Hitachi, Ltd. | Image display |
| US20050195145A1 (en) * | 2004-03-08 | 2005-09-08 | Katsuhiko Maki | Data driver, display device, and method for controlling data driver |
| US6946905B2 (en) * | 2001-11-30 | 2005-09-20 | Fujitsu Limited | Offset cancel circuit of voltage follower equipped with operational amplifier |
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2006
- 2006-01-20 CN CNB2006100417068A patent/CN100430992C/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1428756A (en) * | 1994-11-21 | 2003-07-09 | 精工爱普生株式会社 | Analog buffer and liquid crystal display device |
| US6756962B1 (en) * | 2000-02-10 | 2004-06-29 | Hitachi, Ltd. | Image display |
| US6946905B2 (en) * | 2001-11-30 | 2005-09-20 | Fujitsu Limited | Offset cancel circuit of voltage follower equipped with operational amplifier |
| US20050195145A1 (en) * | 2004-03-08 | 2005-09-08 | Katsuhiko Maki | Data driver, display device, and method for controlling data driver |
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Owner name: NORTHWESTERN POLYTECHNICAL UNIVERSITY Free format text: FORMER OWNER: XI'AN NORTHWESTERN POLYTECHNICAL UNIVERSITY TECHNOLOGY INDUSTRY GROUP CO., LTD. Effective date: 20070727 |
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Assignee: New century photoelectric Co., Ltd. Assignor: Northwestern Polytechnical University Contract record no.: 2010330001592 Denomination of invention: Output buffer circuit for drive voltage in liquid crystal display drive control chip Granted publication date: 20081105 License type: Exclusive License Open date: 20060719 Record date: 20100806 |
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