KR20010054194A - Circuit for providing a common voltage to a liquid crystal display - Google Patents

Circuit for providing a common voltage to a liquid crystal display Download PDF

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Publication number
KR20010054194A
KR20010054194A KR1019990054872A KR19990054872A KR20010054194A KR 20010054194 A KR20010054194 A KR 20010054194A KR 1019990054872 A KR1019990054872 A KR 1019990054872A KR 19990054872 A KR19990054872 A KR 19990054872A KR 20010054194 A KR20010054194 A KR 20010054194A
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South Korea
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common voltage
transistor
voltage
resistor
base
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KR1019990054872A
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Korean (ko)
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이광수
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윤종용
삼성전자 주식회사
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Priority to KR1019990054872A priority Critical patent/KR20010054194A/en
Publication of KR20010054194A publication Critical patent/KR20010054194A/en

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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
    • G09G3/36—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 using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3696—Generation of voltages supplied to electrode drivers
    • 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
    • G09G3/36—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 using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix

Abstract

PURPOSE: A circuit for generating common voltage is provided to maintain certain level of common voltage corresponding to the change of common voltage without using variable resistor. CONSTITUTION: A circuit for generating common voltage has the first transistor(T1), the first resistor(R1) and a zener diode(zd). The first transistor(T1) is an NPN transistor whose collector is connected to an input voltage(V1) terminal and the emitter is connected to the common voltage substrate. The first resistor(R1) has two ends. One end is connected to the collector of the first transistor and the other end is connected to the base. The zener diode(zd) has a cathode coupled to the connection point among the resistor, the base and an anode coupled to ground.

Description

공통 전압 발생 회로{CIRCUIT FOR PROVIDING A COMMON VOLTAGE TO A LIQUID CRYSTAL DISPLAY}CIRCUIT FOR PROVIDING A COMMON VOLTAGE TO A LIQUID CRYSTAL DISPLAY}

본 발명은 액정 표시 장치(liquid crystal display; LCD) 구동 회로에 관한 것으로서, 특히 가변 저항을 사용하지 않는 공통 전압 발생 회로에 관한 것이다.BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to liquid crystal display (LCD) driving circuits, and more particularly to a common voltage generating circuit that does not use a variable resistor.

박막 트랜지스터 액정 표시 장치(TFT LCD)의 구동에는 그 방식에 따라 저전압 구동과 고전압 구동이 있으며, 이 두 방식에 따라 패널에 인가해주는 공통 전압의 파형도 달라진다.There are low voltage driving and high voltage driving according to the method of driving the thin film transistor liquid crystal display (TFT LCD), and the waveform of the common voltage applied to the panel varies according to the two methods.

고전압 구동 방식에서는 직류 레벨의 공통 전압을 패널에 인가해주며, 이 인가된 공통 전압과 데이터 전압과의 차이 전압에 의해 액정이 동작함으로써 화상이 화면에 디스플레이된다.In the high voltage driving method, a common voltage of a DC level is applied to the panel, and the image is displayed on the screen by operating the liquid crystal by the difference voltage between the applied common voltage and the data voltage.

고전압 구동 방식에서 사용되는 공통 전압은 일반적으로 도 1에 도시된 바와같은 저항 분할 방식에 의해 생성되는데, 이때, LCD 패널의 공통 전압 저항이 일정하지 않으므로 가변 저항(R2)을 조절하여 그 레벨을 조절한다.The common voltage used in the high voltage driving method is generally generated by the resistance dividing method as shown in FIG. 1. In this case, since the common voltage resistance of the LCD panel is not constant, the level is adjusted by adjusting the variable resistor R2. do.

그러나, 가변 저항이 장착된 제품의 화질을 검사할 경우 생산 라인에서 가변 저항을 조절하게 되는데, 이때 가변 저항을 조절하는 행위에 따른 시간적 손실과 가변 저항 조절시 조절봉에 의한 패널의 깨짐 현상이 발생하는 문제점이 있다.However, when checking the image quality of the product equipped with the variable resistor, the variable resistor is adjusted in the production line. At this time, the loss of time due to the action of adjusting the variable resistor and the cracking of the panel due to the adjusting rod when the variable resistor is adjusted are generated. There is a problem.

따라서, 본 발명은 종래의 문제점을 해결하기 위한 것으로, 가변 저항을 사용하지 않는 공통 전압 발생 회로를 제공한다.Accordingly, the present invention is to solve the conventional problems, and provides a common voltage generation circuit that does not use a variable resistor.

도1은 종래의 공통 전압 발생 회로를 간략화한 도면이다.1 is a simplified diagram of a conventional common voltage generation circuit.

도2는 이 발명의 실시예에 따른 공통 전압 발생 회로의 회로도이다.2 is a circuit diagram of a common voltage generating circuit according to an embodiment of the present invention.

도3은 도2를 간략화한 등가 회로도이다.FIG. 3 is an equivalent circuit diagram of FIG. 2 simplified.

상기한 기술적 과제를 달성하기 위한 본 발명에 따른 공통 전압 발생 회로는,The common voltage generation circuit according to the present invention for achieving the above technical problem,

입력 전압단에 컬렉터(collector)가 연결되고 이미터(emitter)가 LCD 패널의 공통 전압 기판에 연결된 제1 트랜지스터, 상기 제1 트랜지스터의 베이스와 컬렉터 사이에 연결된 제1 저항, 및 상기 제1 트랜지스터의 베이스에 캐소드(cathode)가 연결되고 애노드(anode)가 접지된 제너 다이오드로 이루어진다.A first transistor connected to a collector and an emitter connected to a common voltage substrate of an LCD panel, a first resistor connected between a base and a collector of the first transistor, and a first transistor of an input voltage terminal. It is composed of a Zener diode with a cathode connected to the base and an anode grounded.

여기서, 상기 제1 트랜지스터는 NPN 트랜지스터인 것이 바람직하다.Here, the first transistor is preferably an NPN transistor.

이하, 첨부한 도면을 참조로 이 발명의 실시예에 따른 공통 전압 발생 회로를 설명한다.Hereinafter, a common voltage generating circuit according to an embodiment of the present invention will be described with reference to the accompanying drawings.

도2는 이 발명의 실시예에 따른 공통 전압 발생 회로의 회로도이다.2 is a circuit diagram of a common voltage generating circuit according to an embodiment of the present invention.

도2에 도시되어 있듯이, 이 발명의 실시예에 따른 공통 전압 발생 회로는,As shown in Fig. 2, the common voltage generation circuit according to the embodiment of the present invention,

입력 전압(VI)단에 컬렉터가 연결되고 공통 전압 기판에 이미터가 연결되어 공통 전압(Vcom)을 공통 기판에 인가하는 NPN 트랜지스터(T1),NPN transistor (T1) for applying a common voltage (Vcom) to the common substrate, the collector is connected to the input voltage (VI) terminal, the emitter is connected to the common voltage substrate,

트랜지스터(T1)의 컬렉터에 일단이 연결되고 타단이 베이스에 연결된 저항(R1),A resistor R1 having one end connected to the collector of the transistor T1 and the other end connected to the base,

저항(R1)과 트랜지스터(T1)의 베이스의 접점에 캐소드가 연결되고 그라운드(ground)에 애노드가 연결된 제너 다이오드(zd)로 이루어진다.A cathode is connected to the contact of the resistor R1 and the base of the transistor T1 and a zener diode zd is connected to the anode of the ground.

여기서, NPN 트랜지스터(T1)의 컬렉터로 인가되는 입력 전압은 일정한 레벨을 가진 전압으로, 이 입력 전압(VI)은 저항(R1)과 NPN 트랜지스터(T1)에 의해 소정 레벨로 낮아진 공통 전압(Vcom)이 되어 LCD 패널의 공통 전압 기판에 인가된다.Here, the input voltage applied to the collector of the NPN transistor T1 is a voltage having a constant level, and the input voltage VI is the common voltage Vcom lowered to a predetermined level by the resistor R1 and the NPN transistor T1. This is applied to the common voltage substrate of the LCD panel.

저항(R1)은 입력 전압(VI)을 분압시키기 위한 것으로, 저항(R1)에 의해 분압된 전압이 트랜지스터(T1)의 베이스에 형성되도록 한다.The resistor R1 is for dividing the input voltage VI, so that the voltage divided by the resistor R1 is formed at the base of the transistor T1.

제너 다이오드(zd)는 트랜지스터(T1)의 베이스 전압이 공통 전압(Vcom)보다 높도록 하고, 트랜지스터(T1)의 파손을 방지하기 위한 것이다.The zener diode zd is intended to allow the base voltage of the transistor T1 to be higher than the common voltage Vcom and to prevent breakage of the transistor T1.

NPN 트랜지스터(T1)는 일반적으로 이미터-베이스 접합이 순방향으로 바이어스(bias)되고, 컬렉터-베이스 접합이 역방향으로 바이어스될 때 도통되어 컬렉터를 통해 인가되는 전류가 이미터로 나아가게 된다.NPN transistor T1 is generally biased when the emitter-base junction is biased in the forward direction, and is conducted when the collector-base junction is biased in the reverse direction so that the current applied through the collector is directed to the emitter.

도2에서 보면, 입력 전압(VI)은 공통 전압(Vcom)보다 높음을 알 수 있다. 이는 공통 전압(Vcc)이 저항(R1)과 트랜지스터(T1)에 의한 분압 전압이 되기 때문이다. 그리고, 트랜지스터(T1)의 컬렉터 전압(VI)은 베이스 전압(Vz)보다 높고, 트랜지스터(T1)의 베이스 전압(Vz)은 트랜지스터(T1)의 이미터 전압(Vcom)보다 높다.2, it can be seen that the input voltage VI is higher than the common voltage Vcom. This is because the common voltage Vcc becomes the divided voltage by the resistor R1 and the transistor T1. The collector voltage VI of the transistor T1 is higher than the base voltage Vz, and the base voltage Vz of the transistor T1 is higher than the emitter voltage Vcom of the transistor T1.

그러므로, 트랜지스터(T1)는 턴 온 상태를 유지하고 있다.Therefore, the transistor T1 is kept turned on.

그런데, 공통 전압(Vcom)이 인가되는 공통 전압 기판의 저항 즉, 공통 전압 저항은 제품에 따라 그 값이 다르다. 결국, 이미터를 통해 인가되는 공통 전압(Vcom)은 일정한 레벨을 가질 경우 제품마다 레벨 차가 발생하게 된다.However, the resistance of the common voltage substrate to which the common voltage Vcom is applied, that is, the common voltage resistance, varies depending on the product. As a result, when the common voltage Vcom applied through the emitter has a constant level, a level difference occurs for each product.

그러나, 상기와 같은 공통 전압 저항에 의해 레벨 차는 공통 전압 레벨에 따른 트랜지스터(T1)의 턴 온 전위 변화 즉, 트랜지스터의 전도 레벨의 변화에 의해 보상된다.However, with the common voltage resistance as described above, the level difference is compensated by the change in the turn-on potential of the transistor T1 according to the common voltage level, that is, the change in the conduction level of the transistor.

이러한 트랜지스터의 전도 레벨 변화를 도3을 참조로 설명한다.The change in conduction level of such a transistor will be described with reference to FIG.

도3은 도2를 간략화한 등가 회로도이다. 도3에서, 가변 저항으로 표기된 저항(RT)은 저항(R1)과 트랜지스터의 저항 성분을 나타낸다. 그리고, 저항(RL)은 공통 전압 저항이며, VL은 공통 전압 저항에 의해 가변된 공통 전압이다. 이하, VL을 공통 전압이라 칭한다.FIG. 3 is an equivalent circuit diagram of FIG. 2 simplified. In Fig. 3, a resistor RT denoted as a variable resistor represents a resistor R1 and a resistance component of the transistor. The resistor RL is a common voltage resistor, and VL is a common voltage varied by the common voltage resistor. Hereinafter, VL is called a common voltage.

따라서, 공통 전압(VL)은 다음의 수학식1과 같이 나타낼 수 있다.Therefore, the common voltage VL may be expressed as Equation 1 below.

여기서, 입력 전압(VI)이 일정하므로, 공통 전압 저항(RL)이 변할 때 공통 전압(VL)을 일정하게 유지시키기 위해서는 저항(RT)이 공통 전압 저항(RL)에 비례하는 방향으로 변하여 공통 전압(VL)을 보상하여야 한다.Here, since the input voltage VI is constant, in order to keep the common voltage VL constant when the common voltage resistance RL changes, the resistor RT changes in a direction proportional to the common voltage resistance RL and thus the common voltage. (VL) must be compensated.

본 발명은 이하와 같이 상기 수학식에 따른 보상을 수행한다.The present invention performs the compensation according to the above equation as follows.

우선, 도2에서 이미터와 베이스의 전압을 VBE라고 하면, 베이스-이미터 전압(VBE)은 제너 다이오드(zd)의 전압(VZ)과 공통 전압(VL)의 차이이므로, 공통 전압(VL)은 VZ - VBE이다. 제너 전압(VZ) 즉 베이스 전압은 항상 일정하다.First, when the voltages of the emitter and the base are VBE in FIG. 2, since the base-emitter voltage VBE is a difference between the voltage VZ of the zener diode zd and the common voltage VL, the common voltage VL Is VZ-VBE. Zener voltage VZ, i.e., the base voltage, is always constant.

만약, 공통 전압 기판의 저항값이 다른 제품에 비해 높다면, 공통 전압 기판에서의 공통 전압(VL)은 레벨이 높아지게 된다.If the resistance value of the common voltage substrate is higher than other products, the common voltage VL of the common voltage substrate is increased.

이를 수학식1에 적용하면, 공통 전압(VL)이 높으면 베이스-이미터 전압(VBE)은 낮아지게 된다.Applying this to Equation 1, if the common voltage VL is high, the base-emitter voltage VBE is low.

베이스-이미터 전압(VBE)이 낮아진다는 것은 컬렉터를 통해 이미터로 나아가는 전류가 그 만큼 적게 된다는 것을 의미한다. 다시 말해, 이는 공통 전압 기판에 공급되는 전류의 레벨이 낮아지게 되고 그에 따라 높아진 공통 전압(VL)이 일정 레벨로 회복한다는 것임을 알 수 있다.Lower base-emitter voltage (VBE) means less current flows through the collector to the emitter. In other words, it can be seen that the level of the current supplied to the common voltage substrate is lowered and thus the increased common voltage VL recovers to a constant level.

반대로, 공통 전압 기판의 저항값이 다른 제품에 비해 낮다면,공통 전압 기판에서의 공통 전압(VL)은 레벨이 낮아지게 된다.On the contrary, if the resistance value of the common voltage substrate is lower than other products, the common voltage VL in the common voltage substrate is lowered.

이를 수학식1에 적용하여 보면, 베이스-이미터 전압(VBE)은 높아지게 된다. 베이스-이미터 전압(VBE)이 높다는 것은 컬렉터를 통해 이미터로 나아기는 전류가 그 만큼 많아진다는 것을 의미한다. 다시 말해, 이는 공통 전압 기판에 공급되는 전류의 레벨이 높아지고 그에 따라 낮아진 공통 전압(VL)이 일정 레벨로 회복한다는 것을 의미한다.Applying this to Equation 1, the base-emitter voltage VBE becomes high. The high base-emitter voltage (VBE) means that more current flows through the collector to the emitter. In other words, this means that the level of the current supplied to the common voltage substrate is increased and thus the lowered common voltage VL recovers to a constant level.

결국, 본 발명은 가변 저항없이 공통 전압의 변화에 대응하여 공통 전압이 일정 레벨로 유지되도록 한다.As a result, the present invention allows the common voltage to be maintained at a constant level in response to a change in the common voltage without a variable resistor.

이상에서 설명한 바와 같이, 본 발명에 따르면 가변 저항을 사용하지 않고 일정 레벨의 공통 전압을 발생시킬 수 있는 효과가 있다.As described above, according to the present invention, there is an effect that a common level of a predetermined level can be generated without using a variable resistor.

Claims (2)

입력 전압단에 컬렉터가 연결되고 이미터가 LCD 패널의 공통 전압 기판에 연결된 제1 트랜지스터;A first transistor having a collector connected to an input voltage terminal and an emitter connected to a common voltage substrate of the LCD panel; 상기 제1 트랜지스터의 베이스에 일단이 연결되고 컬렉터에 타단이 연결된 제1 저항; 및A first resistor having one end connected to a base of the first transistor and the other end connected to a collector; And 상기 제1 트랜지스터의 베이스와 상기 제1 저항의 접점에 캐소드(cathode)가 연결되고 애노드(anode)가 접지된 제너 다이오드로 이루어진 공통 전압 발생 회로.And a Zener diode having a cathode connected to a base of the first transistor and a contact of the first resistor, and an anode of which is grounded. 제1항에서,In claim 1, 상기 제1 트랜지스터는,The first transistor, NPN형 바이폴라 트랜지스터인 것을 특징으로 하는 공통 전압 발생 회로.An NPN type bipolar transistor is a common voltage generator circuit.
KR1019990054872A 1999-12-03 1999-12-03 Circuit for providing a common voltage to a liquid crystal display KR20010054194A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100463601B1 (en) * 2001-12-24 2004-12-29 엘지.필립스 엘시디 주식회사 Common voltage generation circuit of Liquid Crystal Display Device
CN105489187A (en) * 2016-01-27 2016-04-13 上海天马微电子有限公司 Circuit for generating common voltage for liquid crystal panel and liquid crystal display

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100463601B1 (en) * 2001-12-24 2004-12-29 엘지.필립스 엘시디 주식회사 Common voltage generation circuit of Liquid Crystal Display Device
CN105489187A (en) * 2016-01-27 2016-04-13 上海天马微电子有限公司 Circuit for generating common voltage for liquid crystal panel and liquid crystal display
CN105489187B (en) * 2016-01-27 2018-04-10 上海天马微电子有限公司 Produce the circuit and its liquid crystal display of the common electric voltage for liquid crystal panel

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