JP3635967B2

JP3635967B2 - Driving method of liquid crystal display device

Info

Publication number: JP3635967B2
Application number: JP03294299A
Authority: JP
Inventors: 教充馬場
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 1999-02-10
Filing date: 1999-02-10
Publication date: 2005-04-06
Anticipated expiration: 2019-02-10
Also published as: JP2000231088A

Description

【０００１】
【発明の属する技術分野】
本発明は、液晶表示装置の駆動回路、液晶表示装置の駆動方法及び液晶表示装置を用いた電子機器に関するものである。
【０００２】
【従来の技術】
液晶表示装置において、駆動モードの種類を切換えた時にその駆動モードに必要な駆動電圧も同時に変えるが、電源がインピーダンスを持っているので駆動電圧を切換える時にその時定数により、瞬間的に駆動電圧が切換わらない。徐々にその電圧が変化するので、電圧が変化している途中の表示は正常にはならないので、駆動モードを切換えた時に表示品質が落ちてしまっていた。例えば、特開平１−３１４２９６号で上記方法を使用している。
【０００３】
【発明が解決しようとする課題】
しかしながら、上述した技術のように駆動電圧を切換える時に電源がその電圧に追従しない場合は、表示品質を落としてしまう。
【０００４】
これらの問題点に鑑みて、本発明の目的とするところは、駆動モードを切換えたときに表示品質を落とすことのない液晶表示装置用の駆動回路、駆動方法及びこれを用いた液晶表示装置を提供することを目的とする。
【０００５】
【課題を解決するための手段】
上記課題を解決するため、本発明の請求項１に記載の液晶表示装置の駆動方法は、液晶表示パネルを駆動する駆動タイミング信号を少なくとも２種類以上発生できる駆動制御回路と、前記駆動制御回路で選択された駆動タイミング信号に応じた駆動電圧を発生させる駆動電圧発生回路と、前記駆動制御回路の前記駆動タイミング信号を前記駆動電圧発生回路で出力される電圧に変換して前記液晶表示パネルに駆動信号を与える液晶駆動回路を備えた液晶表示装置の駆動方法において、
（１）前記駆動制御回路で駆動タイミング信号を切換えて、前記駆動電圧発生回路で出力される駆動電圧が切換わった時に、
（２）前記駆動電圧発生回路の出力電圧が安定するまで前記液晶駆動回路を停止することを特徴とする。
【０００６】
また、請求項２に記載の液晶表示装置の駆動方法は、液晶表示パネルを駆動する駆動タイミング信号を少なくとも２種類以上発生できる駆動制御回路と、前記駆動制御回路で選択された駆動タイミング信号に応じた駆動電圧を発生させる駆動電圧発生回路と、前記駆動制御回路の前記駆動タイミング信号を前記駆動電圧発生回路で出力される電圧に変換して前記液晶表示パネルに駆動信号を与える液晶駆動回路を備えた液晶表示装置の駆動方法において、
（１）前記駆動制御回路で駆動タイミング信号を切換える前に、あらかじめ前記駆動電圧発生回路で出力される駆動電圧を切換えておき、
（２）前記駆動電圧発生回路の出力電圧が安定するまで前記液晶駆動回路を停止することを特徴とする。
【０００７】
さらに、請求項３に記載の液晶表示装置の駆動方法は、請求項１に記載の液晶表示装置の駆動方法において、前記駆動電圧発生回路を更に複数個備えたことを特徴とする。
【０００８】
さらに、請求項４に記載の液晶表示装置の駆動方法は、請求項２に記載の液晶表示装置の駆動方法において、前記駆動電圧発生回路を更に複数個備えたことを特徴とする。
【０００９】
【発明の実施の形態】
図面に基づいて、本発明の実施の形態を説明する。
【００１０】
（第１の実施形態）
図１は、本発明第１の実施形態の液晶表示装置のブロック図である。液晶表示パネル１０１は走査電極と信号電極を有したドットマトリックスで、その間に挟んだ液晶が１８０°以上ねじれ配向したＳＴＮ（スーパーツイストネマチック）で、電荷を印加するとＯＮ（黒）になる液晶表示パネルを使うことを例にとる。液晶駆動回路１０２は、液晶表示パネル１０１の走査電極に電圧を与える走査側駆動回路１０５と信号電極に電圧を与える信号側駆動回路１０６で構成され、走査電極と信号電極の電圧の関係から各ドットの表示が決まる。液晶駆動電圧発生回路１０３は駆動に必要な電圧を発生して、液晶駆動回路１０２に供給する。その電圧は駆動制御回路１０４で制御する。駆動制御回路１０４はＭＰＵ（マイクロプロセッサユニット）等と接続されて、送られてくる表示データを元に駆動タイミング信号を作成して液晶駆動回路１０２に送る。
【００１１】
液晶表示パネル１０１の電極の配線を図２（ａ）で示すが、走査電極が１００本（上から下にＣ１からＣ１００）と信号電極が９６本（左から右にＳ１からＳ９６）が配線される。図２（ｂ）は走査電極が１００本及び信号電極が９６本の全てを使い液晶表示パネル１０１をフル表示している状態である。図２（ｃ）は信号電極９６本とＣ１からＣ１６までの走査電極のみに駆動タイミング信号を与えて表示領域を限定した場合の表示である。走査電極１６本以外の８４本には駆動タイミング信号を与えず常にＯＦＦの状態にする。
【００１２】
図３は走査線１００本すべて使った時の駆動タイミング信号の波形（Ｓ１、Ｃ１からＣ４のみ）であり、これらの駆動タイミング信号は表示データを元に駆動制御回路１０４で作成される。液晶駆動電圧発生回路１０３で液晶を駆動するのに必要な電圧（Ｖ２、Ｖ１、Ｖｃ、ＭＶ１、ＭＶ２）を作成して、液晶駆動回路１０２でレベル変換を行なう。１フレーム内で走査電極の１００本が順次選択されて書き換わる。
【００１３】
次に、ＭＰＵ等からの外部制御により液晶表示パネルの１６本を選択する命令が駆動制御回路１０４に入った場合、液晶表示パネルに加わる駆動タイミング信号が図４になるように駆動制御回路１０４で作成する。１フレームの中で１６本を駆動できる駆動タイミング信号に変換すると、走査電極の選択数によりその駆動電圧が異なるので、液晶駆動電圧発生回路１０３で駆動電圧も変更する。また、表示する走査電極の１６本以外は必ずＯＦＦになるように走査電極の電圧をＶｃに固定して常に液晶をＯＦＦにしておく。表１に液晶材のしきい値電圧が１．０Ｖで、そのしきい値と液晶がＯＦＦの実効電圧値が等しい条件での駆動電圧と選択本数の関係を示す。
【００１４】
【表１】

【００１５】
選択本数が変わっても常に５つの電圧（Ｖ２、Ｖ１、Ｖｃ、ＭＶ１、ＭＶ２）を使用してその電圧を変える前提である。
【００１６】
図５は液晶駆動電圧発生回路１０３内の電圧の作成部を示している。電源５０１を定電圧レギュレータ５０２で駆動に必要な電圧に合せ込む。その電圧は出力電圧調整の制御線で調整されＶ２となり、Ｖ１、ＭＶ２、ＭＶ１はＶ２とＶｃ間の電位差を元にチャージポンプ回路で作成する。電圧の関係は、Ｖ１＝Ｖ２／２、ＭＶ１＝ＭＶ２／２、−Ｖ２＝ＭＶ２、−Ｖ１＝ＭＶ１である。
【００１７】
液晶駆動電圧発生回路１０３で出力電圧を変えた時、液晶駆動電圧発生回路１０３の各電圧の出力インピーダンスが高い場合、駆動電圧を切換えてもすぐに追従しない。そのため、１６本選択に切換えた後、所定の駆動電圧より高くなるので表示の品質が劣化する。この時の液晶駆動電圧発生回路１０３の出力電圧Ｖ２の様子を図６に示す。１、２フレームは１００本選択の１．９２Ｖで３フレーム目から１６本選択に切換えたため１．６３Ｖにするが、電圧がすぐに追いつかずに３フレームの間は電圧が安定しない。この時に表示品質の劣化を防止するために、３フレーム目はＶｃ（０Ｖ）に選択電極および信号電極を固定して、液晶表示パネルに駆動電圧の変化が伝わらないように表示を停止する。選択電極は走査側駆動回路１０５で、信号電極は信号側駆動回路１０６にて制御することで液晶をＯＦＦにする。１００本選択から例えば６４本選択、８０本選択に切換える時も同様にその出力電圧が変わるので、切換える時は一時的に表示を停止させる。
【００１８】
（第２の実施形態）
前記第１の実施形態と同じく図１は、本発明第２の実施形態の液晶表示装置のブロック図である。表示を停止するシーケンスが第１の実施形態と異なるので、その説明をする。
【００１９】
表示本数を１００本から１６本に切換える時に、液晶駆動電圧発生回路１０３で出力電圧も切換えるが、液晶駆動電圧発生回路１０３の各電圧の出力インピーダンスが高い場合、駆動電圧を切換えてもすぐに追従しないので、１６本選択に切換えた後、所定の駆動電圧より高くなるので表示の品質が劣化する。この時の液晶駆動電圧発生回路１０３の出力電圧Ｖ２の様子を図７に示す。１、２、３フレームは１００本選択の１．９２Ｖで４フレーム目から１６本選択の１．６３Ｖに切換える。３フレームは電圧の変化が起きるので表示品質を落とすが、これを防止するために、１６本選択に切換える前にあらかじめ液晶駆動電圧発生回路１０３の出力電圧を切換える。電圧がすぐに追いつかないので、同時に選択電極および信号電極をＶｃに固定して、非表示にする。選択電極は走査側駆動回路１０５で、信号電極は信号側駆動回路１０６にて制御することで液晶をＯＦＦにする。
【００２０】
（第３の実施形態）
図８は、本発明第３の実施形態の液晶表示装置のブロック図である。液晶表示パネル８０１は走査電極と信号電極を有したドットマトリックスで、その間に液晶を挟んだ液晶が１８０°以上ねじれ配向したＳＴＮ（スーパーツイストネマチック）で、電荷を印加するとＯＮ（黒）になる液晶表示パネルを使うことを例にとる。液晶駆動回路８０２は、液晶表示パネル８０１の走査電極に電圧を与える走査側駆動回路８０５と信号電極に電圧を与える信号側駆動回路８０６で構成される。第１の液晶駆動電圧発生回路８０３と第２の液晶駆動電圧発生回路８０７は駆動に必要な電圧を発生して、液晶駆動回路８０２に供給する。その電圧は制御信号により可変できる。駆動制御回路８０４はＭＰＵ（マイクロプロセッサユニット）等と接続されて、送られてくる表示データを元に駆動タイミング信号を作成して液晶駆動回路８０２に送る。
【００２１】
液晶表示パネル８０１に図２（ａ）に示した走査電極（１００本）と信号電極（９６本）とを配置したドットマトリクスタイプの液晶表示パネルを使用して、図２（ｂ）のように走査電極を１００本選択した表示から、図２（ｃ）のように走査電極を１６本選択した表示に切換えた時に、液晶駆動電圧発生回路も第１の液晶駆動電圧発生回路８０３から第２の液晶駆動電圧発生回路８０７に切換わる。切換えた後、第２の液晶駆動電圧発生回路８０７をＯＮさせるので、所定の駆動電圧に達するまで時間がかかり表示の品質が劣化する。この時の第１の液晶駆動電圧発生回路８０３から第２の液晶駆動電圧発生回路８０７に切換えた時の出力電圧Ｖ２の様子を図６に示す。１、２フレームは１００本選択で３フレームから１６本選択に切換えた時に、Ｖ２の電圧も１００本選択の第１の液晶駆動電圧発生回路８０３の１．９２Ｖから３フレームから第２液晶駆動電圧発生回路８０７の１．６３Ｖ切換えるが、電圧がすぐに立上らずに３フレームの間は電圧が安定しない。この時に表示品質の劣化を防止するために、３フレーム目はＶｃ（０Ｖ）に選択電極および信号電極を固定する。選択電極は走査側駆動回路８０５で、信号電極は信号側駆動回路８０６にて制御することで液晶をＯＦＦにする。
【００２２】
また、別のシーケンスとして、１、２、３フレームは１００本選択で４フレームから１６本選択に切換える時に、あらかじめ３フレームから１００本選択の第１の液晶駆動電圧発生回路８０３のＶ２が１．９２Ｖから第２液晶駆動電圧発生回路８０７の１．６３Ｖ切換えるが、電圧がすぐに立上らずに３フレームの間は電圧が安定しない。この時に表示品質の劣化を防止するために３フレームは電圧の変化が起きるので表示品質を落とす、これを防止するために、３フレームは選択電極および信号電極をＶｃに固定して、非表示にする。選択電極は走査側駆動回路１０５で、信号電極は信号側駆動回路１０６にて制御することで液晶をＯＦＦにする。
【００２３】
本発明は、小型情報機器等の電子機器の液晶表示装置として使用することで、例えば１日２４時間液晶表示する場合において、選択本数が少ない表示ほど消費電流も少ないので、選択本数が少ない表示を多用することにより低消費電流になり、電池駆動の電子機器ではその寿命を延ばすことができる。
【００２４】
実施例では選択本数を１００本と１６本の切換えを例にしたが、任意の選択本数を選択できる。
【００２５】
図２（ｃ）は選択電極数１６本の表示例でＣ１からＣ１６まで選択信号を与え、Ｃ１７からＣ１００までＶｃを与えているが、選択信号を与える位置は自由に変更できる。連続的に選択する位置を変えることで、表示のスクロールや表示位置を瞬時に移動することが可能である。
【００２６】
実施例では、駆動電圧が高い方向から低い方向に切換える場合を例にしたが、逆に低い方向から高い方向に切換えた場合も同様に、液晶表示パネルの電極に加える駆動タイミング信号を停止することで、表示品質の低下を防げる。
【００２７】
実施例では、フレームに同期して駆動タイミング信号の停止を行ったが、特にフレームに同期させることなく、駆動電圧が不安定な時にその電圧を液晶表示パネルに印可しなければ、同様の効果が得られる。
【００２８】
実施例では、駆動タイミング信号を停止する時に、走査電極および信号電極の両者をＶｃに固定したが、走査電極のみをＶｃに固定しても同様の効果が得られる。
【００２９】
【発明の効果】
以上述べたように本発明によれば、連続的に駆動方式を切換える時に駆動電圧発生回路の出力電圧が所定の電圧に達するまでは、駆動波形を一時的に停止させて、表示品質を一定にすることができる。
【００３０】
また、液晶表示パネルを部分的に使う駆動方式を多用することで、消費電流を押さえることができる。
【００３１】
例えば電源に電池を使い、常時液晶表示する上記構成を有する電子機器において、複数の駆動タイミング信号を使うアプリケーションの場合、一方の駆動タイミング信号で液晶表示パネル全体を使い、表示される情報量が多い、住所録、地図、スケジュール、メモ、カレンダー等を表示して、他方の駆動タイミング信号で液晶表示パネルを部分的に表示して、表示される情報量の少ない時計、日付等を表示する。部分的に表示する駆動方法は消費電流が少ないので、一種類の駆動タイミング信号で常に液晶表示パネル全体を表示させる電子機器よりも電池の寿命を長くすることができる。また、駆動電圧発生回路が単数であれば省スペースで実現できる。さらに表示品質を低下させずに駆動タイミング信号を切換えることができる。
【図面の簡単な説明】
【図１】本発明第１および第２の形態の液晶表示装置のブロック図である。
【図２】（ａ）は液晶表示パネルの電極配置である。
（ｂ）は（ａ）の走査電極を１００本選択した表示例である。
（ｃ）は（ａ）の走査電極を１６本選択した表示例である。
【図３】図２（ｂ）を駆動するタイミング信号である。
【図４】図２（ｃ）を駆動するタイミング信号である。
【図５】電圧発生回路の構成図の一例である。
【図６】電圧発生回路の電圧を可変した時のＶ２の波形である。
【図７】電圧発生回路の電圧を可変した時のＶ２の波形である。
【図８】本発明第３の形態例の液晶表示装置のブロック図である。
【図９】電圧発生回路の電圧を可変した時のＶ２の波形である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a driving circuit for a liquid crystal display device, a driving method for the liquid crystal display device, and an electronic apparatus using the liquid crystal display device.
[0002]
[Prior art]
In a liquid crystal display device, when the type of drive mode is switched, the drive voltage required for the drive mode is also changed at the same time. However, since the power supply has impedance, the drive voltage is switched instantaneously according to the time constant when the drive voltage is switched. I don't know. Since the voltage gradually changes, the display while the voltage is changing does not become normal, and the display quality has deteriorated when the drive mode is switched. For example, the above method is used in JP-A-1-314296.
[0003]
[Problems to be solved by the invention]
However, if the power source does not follow the voltage when the drive voltage is switched as in the above-described technique, the display quality is degraded.
[0004]
In view of these problems, an object of the present invention is to provide a driving circuit, a driving method, and a liquid crystal display device using the driving circuit for a liquid crystal display device that do not deteriorate display quality when the driving mode is switched. The purpose is to provide.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, a driving method of a liquid crystal display device according to claim 1 of the present invention includes a drive control circuit capable of generating at least two types of drive timing signals for driving a liquid crystal display panel, and the drive control circuit. A driving voltage generating circuit for generating a driving voltage according to the selected driving timing signal; and driving the liquid crystal display panel by converting the driving timing signal of the driving control circuit into a voltage output from the driving voltage generating circuit. In a driving method of a liquid crystal display device including a liquid crystal driving circuit for giving a signal,
(1) When the drive timing signal is switched by the drive control circuit and the drive voltage output by the drive voltage generation circuit is switched,
(2) The liquid crystal driving circuit is stopped until the output voltage of the driving voltage generating circuit is stabilized.
[0006]
According to a second aspect of the present invention, there is provided a driving method for a liquid crystal display device according to a driving control circuit capable of generating at least two types of driving timing signals for driving a liquid crystal display panel, and a driving timing signal selected by the driving control circuit. A driving voltage generating circuit for generating a driving voltage; and a liquid crystal driving circuit for converting the driving timing signal of the driving control circuit into a voltage output from the driving voltage generating circuit and supplying the driving signal to the liquid crystal display panel. In the driving method of the liquid crystal display device,
(1) Before the drive timing signal is switched by the drive control circuit, the drive voltage output by the drive voltage generation circuit is switched in advance.
(2) The liquid crystal driving circuit is stopped until the output voltage of the driving voltage generating circuit is stabilized.
[0007]
Furthermore, a driving method for a liquid crystal display device according to a third aspect of the invention is the driving method for a liquid crystal display device according to the first aspect, further comprising a plurality of the driving voltage generation circuits.
[0008]
Furthermore, a method for driving a liquid crystal display device according to a fourth aspect of the present invention is the method for driving a liquid crystal display device according to the second aspect, further comprising a plurality of the drive voltage generation circuits.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0010]
(First embodiment)
FIG. 1 is a block diagram of a liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display panel 101 is a dot matrix having scanning electrodes and signal electrodes, and the liquid crystal sandwiched between them is STN (super twisted nematic) in which the liquid crystal sandwiched between them is 180 ° or more, and turns on (black) when a charge is applied. Take the example of using. The liquid crystal driving circuit 102 includes a scanning side driving circuit 105 that applies a voltage to the scanning electrodes of the liquid crystal display panel 101 and a signal side driving circuit 106 that applies a voltage to the signal electrodes. Is displayed. The liquid crystal driving voltage generation circuit 103 generates a voltage necessary for driving and supplies it to the liquid crystal driving circuit 102. The voltage is controlled by the drive control circuit 104. The drive control circuit 104 is connected to an MPU (microprocessor unit) or the like, creates a drive timing signal based on the display data sent, and sends it to the liquid crystal drive circuit 102.
[0011]
The wiring of the electrodes of the liquid crystal display panel 101 is shown in FIG. 2A, and 100 scanning electrodes (C1 to C100 from the top to the bottom) and 96 signal electrodes (S1 to S96 from the left to the right) are wired. The FIG. 2B shows a state in which the liquid crystal display panel 101 is fully displayed using all 100 scanning electrodes and 96 signal electrodes. FIG. 2C shows a display when the display area is limited by giving drive timing signals only to 96 signal electrodes and the scanning electrodes C1 to C16. A drive timing signal is not applied to 84 electrodes other than the 16 scan electrodes, and is always turned off.
[0012]
FIG. 3 shows waveforms of drive timing signals when only 100 scanning lines are used (S1, C1 to C4 only). These drive timing signals are generated by the drive control circuit 104 based on display data. Voltages (V2, V1, Vc, MV1, and MV2) necessary for driving the liquid crystal are generated by the liquid crystal drive voltage generation circuit 103, and level conversion is performed by the liquid crystal drive circuit 102. In one frame, 100 scanning electrodes are sequentially selected and rewritten.
[0013]
Next, when an instruction for selecting 16 liquid crystal display panels from the MPU or the like is input to the drive control circuit 104, a drive timing signal applied to the liquid crystal display panel is generated by the drive control circuit 104 as shown in FIG. create. When converted into drive timing signals that can drive 16 lines in one frame, the drive voltage varies depending on the number of scan electrodes selected, so the liquid crystal drive voltage generation circuit 103 also changes the drive voltage. Further, the voltage of the scanning electrode is fixed at Vc so that all but 16 scanning electrodes to be displayed are always turned off, and the liquid crystal is always turned off. Table 1 shows the relationship between the drive voltage and the number of selections under the condition that the threshold voltage of the liquid crystal material is 1.0 V and the threshold voltage is equal to the effective voltage value when the liquid crystal is OFF.
[0014]
[Table 1]

[0015]
Even if the selection number changes, it is a premise that five voltages (V2, V1, Vc, MV1, and MV2) are always used to change the voltage.
[0016]
FIG. 5 shows a voltage generator in the liquid crystal drive voltage generation circuit 103. The power source 501 is adjusted to a voltage required for driving by the constant voltage regulator 502. The voltage is adjusted to V2 by the output voltage adjustment control line, and V1, MV2, and MV1 are generated by the charge pump circuit based on the potential difference between V2 and Vc. The voltage relationships are V1 = V2 / 2, MV1 = MV2 / 2, −V2 = MV2, and −V1 = MV1.
[0017]
When the output voltage is changed by the liquid crystal drive voltage generation circuit 103, if the output impedance of each voltage of the liquid crystal drive voltage generation circuit 103 is high, even if the drive voltage is switched, it does not follow immediately. Therefore, after switching to the selection of 16 lines, the display quality deteriorates because it becomes higher than a predetermined drive voltage. The state of the output voltage V2 of the liquid crystal drive voltage generation circuit 103 at this time is shown in FIG. The 1st and 2nd frames are 1.92V with 100 selections, and since the 3rd frame is switched to 16th selection with 1.63V, the voltage does not catch up immediately, and the voltage is not stable for 3 frames. At this time, in order to prevent the display quality from deteriorating, the selection electrode and the signal electrode are fixed to Vc (0 V) in the third frame, and the display is stopped so that the change of the driving voltage is not transmitted to the liquid crystal display panel. The selection electrode is controlled by the scanning side driving circuit 105 and the signal electrode is controlled by the signal side driving circuit 106 to turn off the liquid crystal. When switching from 100 selection to 64 selection or 80 selection, for example, the output voltage changes in the same manner. Therefore, the display is temporarily stopped when switching.
[0018]
(Second Embodiment)
As in the first embodiment, FIG. 1 is a block diagram of a liquid crystal display device according to a second embodiment of the present invention. The sequence for stopping the display is different from that in the first embodiment, and will be described.
[0019]
When the number of displays is switched from 100 to 16, the output voltage is also switched by the liquid crystal drive voltage generation circuit 103. However, if the output impedance of each voltage of the liquid crystal drive voltage generation circuit 103 is high, it immediately follows even if the drive voltage is switched. Therefore, after switching to the selection of 16 lines, the display quality deteriorates because the voltage becomes higher than a predetermined drive voltage. The state of the output voltage V2 of the liquid crystal drive voltage generation circuit 103 at this time is shown in FIG. The first, second and third frames are switched to 1.92V with 100 lines selected and switched to 1.63V with 16 lines selected from the fourth frame. In 3 frames, since the voltage changes, the display quality is deteriorated. In order to prevent this, the output voltage of the liquid crystal drive voltage generation circuit 103 is switched in advance before switching to the selection of 16 lines. Since the voltage cannot catch up immediately, the selection electrode and the signal electrode are fixed to Vc at the same time and are not displayed. The selection electrode is controlled by the scanning side driving circuit 105 and the signal electrode is controlled by the signal side driving circuit 106 to turn off the liquid crystal.
[0020]
(Third embodiment)
FIG. 8 is a block diagram of a liquid crystal display device according to a third embodiment of the present invention. The liquid crystal display panel 801 is a dot matrix having scanning electrodes and signal electrodes, and is a STN (super twisted nematic) in which the liquid crystal sandwiched between them is twisted by 180 ° or more, and turns on (black) when a charge is applied. Take the example of using a display panel. The liquid crystal driving circuit 802 includes a scanning side driving circuit 805 that applies voltage to the scanning electrodes of the liquid crystal display panel 801 and a signal side driving circuit 806 that supplies voltage to the signal electrodes. The first liquid crystal driving voltage generation circuit 803 and the second liquid crystal driving voltage generation circuit 807 generate a voltage necessary for driving and supplies the voltage to the liquid crystal driving circuit 802. The voltage can be varied by a control signal. The drive control circuit 804 is connected to an MPU (microprocessor unit) or the like, creates a drive timing signal based on the display data sent, and sends it to the liquid crystal drive circuit 802.
[0021]
A dot matrix type liquid crystal display panel in which the scanning electrodes (100 lines) and signal electrodes (96 lines) shown in FIG. 2A are arranged on the liquid crystal display panel 801 is used as shown in FIG. When the display with 100 scan electrodes selected is switched to the display with 16 scan electrodes selected as shown in FIG. 2C, the liquid crystal drive voltage generation circuit also changes from the first liquid crystal drive voltage generation circuit 803 to the second one. Switching to the liquid crystal drive voltage generation circuit 807 is performed. Since the second liquid crystal drive voltage generation circuit 807 is turned on after switching, it takes time until the predetermined drive voltage is reached, and the display quality deteriorates. FIG. 6 shows the state of the output voltage V2 when switching from the first liquid crystal drive voltage generation circuit 803 to the second liquid crystal drive voltage generation circuit 807 at this time. When the 1st and 2nd frames are selected 100 and the 3rd frame is selected to the 16th selection, the voltage V2 is also 1.92V of the 100th selected first liquid crystal drive voltage generation circuit 803 and the second liquid crystal drive voltage from the 3rd frame. The generator circuit 807 switches 1.63 V, but the voltage does not rise immediately, and the voltage is not stable for 3 frames. At this time, in order to prevent display quality deterioration, the selection electrode and the signal electrode are fixed at Vc (0 V) in the third frame. The selection electrode is controlled by the scanning side driving circuit 805 and the signal electrode is controlled by the signal side driving circuit 806 to turn off the liquid crystal.
[0022]
As another sequence, when switching from 100 frames to 1, 2, 3 frames and switching from 4 frames to 16 frames, V2 of the first liquid crystal drive voltage generation circuit 803, which selects 100 frames from 3 frames in advance, is 1. The second liquid crystal driving voltage generation circuit 807 switches from 92 V to 1.63 V, but the voltage does not rise immediately and the voltage is not stable for 3 frames. At this time, in order to prevent the display quality from deteriorating, the voltage changes in the 3 frames, so the display quality is degraded. To prevent this, the 3 frames are not displayed by fixing the selection electrode and the signal electrode to Vc. To do. The selection electrode is controlled by the scanning side driving circuit 105 and the signal electrode is controlled by the signal side driving circuit 106 to turn off the liquid crystal.
[0023]
The present invention can be used as a liquid crystal display device for electronic devices such as small information devices. For example, in the case of performing liquid crystal display for 24 hours a day, a display with a smaller number of selections has a lower current consumption as a display with a smaller number of selections. When used frequently, the current consumption is reduced, and the life of the battery-driven electronic device can be extended.
[0024]
In the embodiment, the number of selected lines is switched between 100 and 16 as an example, but any number can be selected.
[0025]
In FIG. 2C, a selection signal is given from C1 to C16 and Vc is given from C17 to C100 in a display example of 16 selected electrodes, but the position where the selection signal is given can be freely changed. By changing the position of continuous selection, it is possible to instantaneously move the display scroll or the display position.
[0026]
In the embodiment, the case where the drive voltage is switched from the high direction to the low direction is taken as an example, but conversely, the drive timing signal applied to the electrodes of the liquid crystal display panel is also stopped when switching from the low direction to the high direction. In this way, the display quality can be prevented from deteriorating.
[0027]
In the embodiment, the drive timing signal is stopped in synchronization with the frame, but the same effect can be obtained if the drive voltage is not applied to the liquid crystal display panel when the drive voltage is unstable without being particularly synchronized with the frame. can get.
[0028]
In the embodiment, when the drive timing signal is stopped, both the scan electrode and the signal electrode are fixed to Vc. However, the same effect can be obtained by fixing only the scan electrode to Vc.
[0029]
【The invention's effect】
As described above, according to the present invention, when the drive system is continuously switched, the drive waveform is temporarily stopped until the output voltage of the drive voltage generation circuit reaches a predetermined voltage, and the display quality is kept constant. can do.
[0030]
In addition, the current consumption can be suppressed by using a driving system that partially uses the liquid crystal display panel.
[0031]
For example, in an electronic device having the above-described configuration that uses a battery as a power source and constantly displays liquid crystal, in the case of an application that uses a plurality of drive timing signals, the entire liquid crystal display panel is used with one drive timing signal, and the amount of information displayed is large An address book, a map, a schedule, a memo, a calendar, and the like are displayed, and a liquid crystal display panel is partially displayed with the other drive timing signal to display a clock, date, etc. with a small amount of information to be displayed. Since the driving method for partial display consumes less current, the life of the battery can be made longer than an electronic device that always displays the entire liquid crystal display panel with one type of driving timing signal. Further, if there is a single drive voltage generation circuit, it can be realized in a small space. Furthermore, the drive timing signal can be switched without degrading the display quality.
[Brief description of the drawings]
FIG. 1 is a block diagram of a liquid crystal display device according to first and second embodiments of the present invention.
FIG. 2A is an electrode arrangement of a liquid crystal display panel.
(B) is a display example in which 100 scanning electrodes of (a) are selected.
(C) is a display example in which 16 scanning electrodes of (a) are selected.
FIG. 3 is a timing signal for driving FIG.
FIG. 4 is a timing signal for driving FIG.
FIG. 5 is an example of a configuration diagram of a voltage generation circuit.
FIG. 6 is a waveform of V2 when the voltage of the voltage generation circuit is varied.
FIG. 7 is a waveform of V2 when the voltage of the voltage generation circuit is varied.
FIG. 8 is a block diagram of a liquid crystal display device according to a third embodiment of the present invention.
FIG. 9 is a waveform of V2 when the voltage of the voltage generation circuit is varied.

Claims

A drive control circuit capable of generating at least two types of drive timing signals for driving the liquid crystal display panel;
A drive voltage generation circuit for generating a drive voltage according to the drive timing signal selected by the drive control circuit;
In a driving method of a liquid crystal display device including a liquid crystal driving circuit that converts the driving timing signal of the driving control circuit into a voltage output from the driving voltage generation circuit and gives a driving signal to the liquid crystal display panel.
(1) When the drive timing signal is switched by the drive control circuit and the drive voltage output by the drive voltage generation circuit is switched,
(2) A driving method of a liquid crystal display device, wherein the liquid crystal driving circuit is stopped until an output voltage of the driving voltage generating circuit is stabilized.

A drive control circuit capable of generating at least two types of drive timing signals for driving the liquid crystal display panel;
A drive voltage generation circuit for generating a drive voltage according to the drive timing signal selected by the drive control circuit;
In a driving method of a liquid crystal display device including a liquid crystal driving circuit that converts the driving timing signal of the driving control circuit into a voltage output from the driving voltage generation circuit and gives a driving signal to the liquid crystal display panel.
(1) Before the drive timing signal is switched by the drive control circuit, the drive voltage output by the drive voltage generation circuit is switched in advance.
(2) A driving method of a liquid crystal display device, wherein the liquid crystal driving circuit is stopped until an output voltage of the driving voltage generating circuit is stabilized.

The method for driving a liquid crystal display device according to claim 1, further comprising a plurality of the drive voltage generation circuits.

The method for driving a liquid crystal display device according to claim 2, further comprising a plurality of the drive voltage generation circuits.