JP3747680B2 - Liquid crystal display drive circuit, liquid crystal display drive circuit control method, and liquid crystal display device - Google Patents

Description

となる。
よって、２ラインの表示を追加する場合の消費電流は、
１０［μＡ］＋０．０１３［μＡ］×２［ライン］＝１０．０２６［μＡ］
となり、従来の駆動方式と比較してより低消費電力であることが分かる。
【００２２】
［２］ 第２実施形態
次に、第２実施形態として、他のマルチプレクス駆動方式の液晶表示装置を例として説明する。
上記第１実施形態においては、印加電圧として正側あるいは負側の一方の電圧を用いるものであったが、本第２実施形態は印加電圧として、正側印加電圧及び負側印加電圧の双方の電圧を用いる場合の実施形態であり、装置構成は第１実施形態と同様であるので、詳細な説明を省略する。
図６に第２実施形態の走査側駆動回路１５においてコモン電圧を切り換えるコモン電圧切換回路の概要構成を示す。
コモン電圧切換回路１５Ｃは、走査側駆動回路１５内の制御部１５Ａからの制御信号ＳＣに基づいてトランジスタスイッチＴ1〜Ｔ3のいずれかをオン状態として、コモン電極ＣXに第１選択時電圧Ｖ1、非選択時電圧Ｖ5及び第２選択時電圧−Ｖ1のうちいずれか一の電圧をコモン電圧ＶCMNとして選択的に出力するように構成されている。
これらの３つの電圧のうち、選択領域では、第１選択時電圧Ｖ1、非選択時電圧Ｖ5及び第２選択時電圧−Ｖ1のいずれかが予め定められた電圧パターンに従って選択され、非選択領域では、非選択時電圧Ｖ5が選択される。
さらに本発明の特徴である非選択領域においてライン表示を行う場合には、第１選択時電圧Ｖ1あるいは第２選択時電圧−Ｖ1がフレーム単位で交互に選択される。
なお、第１選択時電圧Ｖ1、非選択時電圧Ｖ5及び第２選択時電圧−Ｖ1の電位関係は、以下の通りとなっている。
Ｖ1＞Ｖ5＞−Ｖ1
｜Ｖ1−Ｖ5｜＝｜Ｖ5−（−Ｖ1）｜
【００２３】
［２．１］ 第２実施形態の具体的動作
次に第２実施形態の具体的動作について説明する。この場合において、液晶表示装置１０の概要動作は第１実施形態と同様であるので、その詳細な説明を省略する。
［２．１．１］ 選択領域における画素点灯動作
図７（ａ）に選択領域における画素点灯動作を説明するための波形説明図を示す。図７（ａ）においては、説明の簡略化のため、コモン電極Ｃ１とセグメント電極Ｓ１の交点の画素を構成する液晶層に対する電圧印加状態を示している。
以下の説明においては、
図７（ａ）に示すように、１対のフレーム群を構成する第１フレームにおいては、セグメント電極Ｓ１に対応するタイミングＴC1では、コモン電圧として第１選択時電圧Ｖ1が印加され、その他のタイミングにおいてはコモン電圧として非選択時電圧Ｖ5が印加される。
他方、セグメント電極には、１フレーム期間中データ電圧Ｖ4が印加される。
【００２４】
この結果、タイミングＴC1においては、液晶層に印加される電圧Ｖは、
Ｖ＝Ｖ1−Ｖ4
となり、印加電圧Ｖが所定の液晶層のオン電圧（ＶON）以上となって当該画素が点灯することとなる。
その後、１対のフレーム群を構成する第２フレームにおいては、セグメント電極Ｓ１に対応するタイミングＴC1’では、コモン電圧として第２選択時電圧−Ｖ1が印加され、その他のタイミングにおいてはコモン電圧として非選択時電圧Ｖ4が印加される。
他方、セグメント電極には、１フレーム期間中データ電圧−Ｖ4が印加される。
この結果、タイミングＴC1’においては、液晶層に印加される電圧Ｖは、
Ｖ＝−Ｖ4−（−Ｖ1）
となり、この場合の印加電圧Ｖも所定の液晶層のオン電圧（ＶON）以上となって当該画素が点灯することとなる。
【００２５】
［２．１．２］ 非選択領域における画素非点灯動作
図７（ｂ）に選択領域における画素点灯動作を説明するための波形説明図を示す。図７（ｂ）においても、説明の簡略化のため、コモン電極Ｃ１とセグメント電極Ｓ１の交点の画素を構成する液晶層に対する電圧印加状態を示している。
図７（ｂ）に示すように、非選択領域における画素非点灯動作は、１対のフレーム群を構成する第１フレーム及び第２フレームにおいて、コモン電圧として非選択時電圧Ｖ5が印加される。
他方、セグメント電極には、第１フレーム期間中データ電圧Ｖ4が印加される。
この結果、当該第１フレームにおいて液晶層に印加される電圧Ｖは、
Ｖ＝Ｖ5−Ｖ4
となり、印加電圧Ｖが所定の液晶層のオフ電圧（ＶOFF）以下となって当該画素が非点灯状態となる。
その後、第２フレームにおいては、セグメント電極には、１フレーム期間中データ電圧−Ｖ4が印加される。
この結果、当該第２フレームにおいては、液晶層に印加される電圧Ｖは、
Ｖ＝Ｖ5−（−Ｖ4）
となり、この場合も印加電圧Ｖが所定の液晶層のオフ電圧（ＶOFF）以下となって当該画素が非点灯状態となる。
【００２６】
［２．１．３］ 非選択領域における画素点灯動作
図７（ｃ）に本願の特徴である非選択領域における画素強制点灯動作を説明するための波形説明図を示す。図７（ｃ）においても、説明の簡略化のため、コモン電極Ｃ１とセグメント電極Ｓ１の交点の画素を構成する液晶層に対する電圧印加状態を示している。
図７（ｂ）に示すように、１対のフレーム群を構成する第１フレームにおいては、コモン電圧として第１選択時電圧Ｖ1が印加される。
他方、セグメント電極には、１フレーム期間中データ電圧Ｖ4が印加される。
この結果、当該第１フレームおいて、液晶層に印加される電圧Ｖは、
Ｖ＝Ｖ1−Ｖ4
となり、印加電圧Ｖが所定の液晶層のオン電圧（ＶON）以上となって当該画素が当該第１フレーム期間中常時点灯することとなる。
その後、１対のフレーム群を構成する第２フレームにおいてはコモン電圧として第２選択時電圧−Ｖ1が印加される。
他方、セグメント電極には、１フレーム期間中データ電圧−Ｖ4が印加される。
この結果、当該第２フレームにおいては、液晶層に印加される電圧Ｖは、
Ｖ＝−Ｖ4−（−Ｖ1）
となり、この場合の印加電圧Ｖも所定の液晶層のオン電圧（ＶON）以上となって当該画素が当該第２フレーム期間中常時点灯することとなる。
【００２７】
［２．２］ 第２実施形態の効果
本第２実施形態によれば、図４（ｂ）に示すような通常駆動の表示に対し、上記３つの態様の表示制御を行うことにより、例えば、上記非選択領域における画素点灯動作を二つのコモン電極について行えば、図４（ｃ）に示すように、液晶表示パネルの表示画面には、２本のラインを引くことができ、デザイン的により好ましいものとなる。
さらにこの場合においても、図４（ａ）に示すような選択領域において、点灯／非点灯制御を行う場合と比較して、図４（ｂ）に示すような非選択領域において点灯制御を行う方式によれば、消費電力を低減することができる。
【００２８】
［３］ 第３実施形態
上記各実施形態は、マルチプレクス方式で液晶を駆動するものであったが、本第３実施形態は、マルチラインスキャン（ＭＬＳ）方式で液晶を駆動する場合の実施形態である。マルチラインスキャン方式は、上記マルチプレクス方式と異なり複数のコモン電極を同時に走査しながら、順次走査していく駆動方式であり、例えば、国際出願ＷＯ９３／１８５０１号公報に詳細が開示されている。
なお、本第３実施形態において、装置構成については、図１の第１実施形態と同様であるものとして説明する。
【００２９】
［３．１］ 選択領域における画素点灯／非点灯動作
次に選択領域における画素点灯／非点灯動作について説明する。
まず、選択領域における画素点灯／非点灯動作の概要について述べる。
このようなマルチラインスキャン方式で、４ラインづつコモン電極を走査する場合の概要駆動波形を図８（ａ）〜（ｄ）に示す。図８（ａ）〜（ｄ）においては、図示の簡略化のため、全コモン電極ＣL（Ｌ＝1，2，3，4，……）のうちコモン電極Ｃ1〜Ｃ4における選択期間の波形を矩形波のように図示しているが、実際には、後述するように、同時に駆動される他のコモン電極（例えば、コモン電極Ｃ2に対するコモン電極Ｃ1、Ｃ3、Ｃ4）の電位状態を考慮した複雑な波形となっている。
また、セグメント電極Ｓ1の波形についても、１フレーム中で変化が無いように図示しているが、実際には、後述するように、同時に走査する４個のコモン電極（上述の例の場合、コモン電極Ｃ1〜Ｃ4）に対応する画素の点灯、非点灯並びにコモン電極の印加電圧波形に対応する複雑な波形となっている。
そして、例えば、コモン電極Ｃ2とセグメント電極Ｓ1により電圧が印加される液晶層は、時間軸上で時々刻々と変化するコモン電極Ｃ1の印加電圧及びセグメント電極Ｓ1の印加電圧の電圧差の積分値（実効電圧）に応じて点灯あるいは非点灯となる。
【００３０】
［３．１．１］ 選択領域における画素点灯／非点灯動作の具体例
次に選択領域における画素点灯／非点灯動作について図１、図１１および図１２を参照して具体的に説明する。
液晶表示装置１０は、図１１に示すように、液晶表示パネル１１には、複数本のコモン電極Ｃ1、Ｃ2、…、ＣLを有する基板と複数本のセグメント電極Ｓ1、Ｓ2、…、ＳMを有する基板との間に液晶層が介在されている。
液晶駆動回路１２の走査側駆動回路１５は、この液晶表示パネル１１を駆動するためにコモン電極Ｃに向けて走査信号を出力し、信号側駆動回路１６は、セグメント電極Ｓに向けてデータ信号を出力する。
次に、上記構成の液晶表示装置１０の駆動動作をより詳細に説明する。
ここでは、複数本のコモン電極Ｃのうち、順次３本の走査電極を同時に選択して図１１に示すような表示を液晶表示パネル１１上に行うようにしたものである。
すなわち、最初の３つのコモン電極Ｃ1，Ｃ2，Ｃ3 を選択期間ｔ1で選択して、これらのコモン電極Ｃ1，Ｃ2，Ｃ3 に図１２（ａ）に示すような走査信号を印加し、同時にセグメント電極Ｓに所定のデータ信号を印加する。
次に、コモン電極Ｃ4，Ｃ5，Ｃ6 を選択して、それらの電極に上記と同様に図１２（ｂ）のような走査信号を印加すると同時にセグメント電極Ｓにデータ信号を印加する。そして、図１１における全てのコモン電極Ｃが選択されるまでを１フレームとして、順次これを繰り返す。
さらに、各走査信号の波形は、選択されるコモン電極Ｃの数をｈとした場合、１個の選択期間ｔ1内の時間Δｔを単位としたパルスパターン数が２^hの波形が用いられる。
【００３１】
例えば、図１２に示すように、３本のコモン電極Ｃを選択した場合に形成される走査信号は、選択期間ｔ1を８個（２³ ＝８）に分けた時間Δｔによって区切られ、始めの時間Δｔのときには、コモン電極Ｃ1がオフ、コモン電極Ｃ2がオフ、コモン電極Ｃ3がオフとなり、次の時間Δｔのときには、コモン電極Ｃ1がオフ、コモン電極Ｃ2がオフ、コモン電極Ｃ3がオンとなり、順次８個の時間Δｔに分けて形成される波形が用いられる。
また、セグメント電極Ｓに印加されるデータ信号は、同時に表示対象となる各ドット（３ライン同時駆動なら３ドット）のオン・オフと、コモン電極Ｃに印加される走査信号の電圧値によって決定される。例えば、同時に選択されるコモン電極Ｃ1，Ｃ2，Ｃ3に印加される走査信号の波形が正のパルスのときをオン、負のパルスのときをオフとし、表示データのオン・オフをパルス毎に対比し、不一致の数に応じてデータ信号を設定するようにしている。
具体的には、図１１におけるコモン電極Ｃ1，Ｃ2，Ｃ3への走査信号の波形において、Ｖ2の電圧を印加するときをオン、ＭＶ2の電圧を印加するときをオフとし、図１１の画素の表示が黒丸印をオン、白丸印をオフとすると、図１１におけるセグメント電極Ｓ1とコモン電極Ｃ1，Ｃ2，Ｃ3との交差する画素の表示は順にオン・オン・オフとなる。これに対してコモン電極Ｃ1，Ｃ2，Ｃ3に印加されるパルスパターンの最初の電圧は、それぞれオフ・オフ・オフである。そして、この両者を順に対比すると不一致の数は２であるから、セグメント電極Ｓ1の最初のパルスパターンには、図１２（ｃ）に示すような電圧Ｖ2が印加される。
【００３２】
このように、図１２においては、不一致の数が０のときはＭＶ2、１のときはＭＶ1、２のときはＶ1、３のときはＶ2のパルス電圧を印加するようにしている。なお、Ｖ1とＶ2の電圧比は、Ｖ1：Ｖ2＝１：２となるように設定されている。また、コモン電極Ｃ1，Ｃ2，Ｃ3に印加される電圧の２番目のパルスパターンは、それぞれオフ・オフ・オンであり、画素の表示はオン・オン・オフと順に対比すると、全てが不一致であり不一致数は３であるから、セグメント電極Ｓ1の２番目のパルスには電圧Ｖ2が印加される。同様にして、３番目のパルスにはＶ1、４番目のパルスにはＭＶ1が印加され、以下ＭＶ2，Ｖ1，ＭＶ1，ＭＶ1の順で印加されている。
さらに、次のコモン電極Ｃ4〜Ｃ6が選択され、そのコモン電極Ｃ4〜Ｃ6に図１２（ｂ）に示す電圧が印加されるときには、その各コモン電極Ｃ4〜Ｃ6と信号電極との交差する画素のオン・オフ表示と、前記コモン電極Ｃ4〜Ｃ6への印加電圧の各パルスパターンのオン・オフとの不一致に応じた電圧レベルのデータ信号が、図１２（ｃ）のように印加される。なお、図１２（ｄ）はコモン電極Ｃ1とセグメント電極Ｓ1とが交差する画素に印加される波形、即ちコモン電極Ｃ1に印加される走査信号とセグメント電極Ｓ1に印加されるデータ信号との合成波形である。
このように、順次複数本の走査電極を同時に選択して駆動するマルチラインスキャン方式では、オン／オフ比を実現した上で、駆動電圧を低く抑えることができるのである。
【００３３】
［３．２］ 非選択時コモン電圧切換回路の概要構成
図９に走査側駆動回路１５における非選択時のコモン電圧を切り換える非選択時コモン電圧切換回路の概要構成図を示す。
非選択時コモン電圧切換回路１５Ｄは、走査側駆動回路１５内の制御部１５Ａからの制御信号ＳＣに基づいてトランジスタスイッチＴ1〜Ｔ3のいずれかをオン状態として、コモン電極ＣXに非選択時電圧ＶC、第１選択時電圧Ｖ2、第２選択時電圧ＭＶ2を選択的にコモン電圧ＶCMNとして出力するように構成されている。これらの３つの電圧のうち、選択領域では、第１選択時電圧Ｖ2、非選択時電圧ＶC及び第２選択時電圧ＭＶ2のいずれかが予め定められた電圧パターンに従って選択され、非選択領域では、非選択時電圧ＶCが選択される。
さらに本発明の特徴である非選択領域においてライン表示を行う場合には、第１選択時電圧Ｖ2あるいは第２選択時電圧ＭＶ2が１／２フレーム単位で交互に選択される。なお、１／２フレーム単位としているのは、制御が容易で、消費電力が少ない（周波数が低いため）であるが、これに限る必要はなく、１／４フレーム単位、１／８フレーム単位、……等の１／２ⁿフレーム単位で交互に選択するように構成することが可能である。
この場合において、第１選択時電圧Ｖ2、非選択時電圧ＶC及び第２選択時電圧ＭＶ2並びに電圧Ｖ1及び電圧ＭＶ1の電位関係は、以下の通りとなっている。
Ｖ1＝Ｖ2／２
ＭＶ1＝ＭＶ2／２
Ｖ2＞ＶC＞ＭＶ2
｜Ｖ2−ＶC｜＝｜ＶC−ＭＶ2｜
【００３４】
［３．３］ 第３実施形態の具体的動作
次に第３実施形態の具体的動作について説明する。この場合において、液晶表示装置１０の概要動作は第１実施形態と同様であるので、その詳細な説明を省略する。
また、以下の説明においては、説明の簡略化のため、コモン電極Ｃ１とセグメント電極Ｓ１の交点の画素を構成する液晶層に対する電圧印加状態を中心として説明する。
【００３５】
［３．３．１］ 非選択領域における画素非点灯動作
上述したように、セグメント電極Ｓ1の波形は、同時に走査するコモン電極Ｃ1〜Ｃ4に対応する画素の点灯、非点灯並びにコモン電極の印加電圧波形に対応する複雑な波形となっている。
従って、予測される全てのセグメント電極Ｓ1の波形に対し、コモン電極Ｃ1との間の実効電圧（＝積分実効電圧）がオン電圧を超えないようにすればよい。
このため、非選択領域における画素非点灯動作は、図９（ａ）に示すように、１対のフレーム群を構成する第１フレーム及び第２フレームにおいて、コモン電圧として非選択時電圧ＶCが印加される。
他方、セグメント電極Ｓ1には、同時に走査するコモン電極Ｃ1〜Ｃ4に対応する画素の点灯、非点灯並びにコモン電極の印加電圧波形に対応する波形に基づく電圧（図１０（ａ）では、その平均電圧としてＶ1を図示している。）が印加される。
【００３６】
この結果、当該第１フレームにおいて液晶層に印加される電圧Ｖは、
Ｖ≒Ｖ1−ＶC
となり、印加電圧Ｖは所定の液晶層のオフ電圧（ＶOFF）以下となって当該画素が非点灯状態となる。
その後、第２フレームにおいては、セグメント電極には、同時に走査するコモン電極Ｃ1〜Ｃ4に対応する画素の点灯、非点灯並びにコモン電極の印加電圧波形に対応する波形に基づく電圧（図１０（ａ）では、その平均電圧としてＭＶ1を図示している。）が印加される。
この結果、当該第１フレームにおいて液晶層に印加される電圧Ｖは、
Ｖ≒ＶC−ＭＶ1
となり、印加電圧Ｖは所定の液晶層のオフ電圧（ＶOFF）以下となって当該画素が非点灯状態となる。
【００３７】
［３．３．２］ 非選択領域における画素点灯動作
図１０（ｂ）に本願の特徴である非選択領域における画素強制点灯動作を説明するための波形説明図を示す。図１０（ｂ）においても、説明の簡略化のため、コモン電極Ｃ１とセグメント電極Ｓ１の交点の画素を構成する液晶層に対する電圧印加状態を示している。
図１０（ｂ）に示すように、１対のフレーム群を構成する第１フレームの前半においては、コモン電圧として第２選択時電圧ＭＶ2が印加され、後半においては、、コモン電圧として第１選択時電圧Ｖ2が印加される。
他方、セグメント電極には、同時に走査するコモン電極Ｃ1〜Ｃ4に対応する画素の点灯、非点灯並びにコモン電極の印加電圧波形に対応する波形に基づく電圧（図１０（ｂ）では、その平均電圧としてＶ1を図示している。）が印加される。
【００３８】
この結果、当該第１フレームの前半において、液晶層に印加される電圧Ｖは、
Ｖ≒Ｖ1−ＭＶ2
となり、単位時間（＝１フレーム）当たりの実効電圧である印加電圧Ｖが所定の液晶層のオン電圧（ＶON）以上となって当該画素が当該第１フレームの前半期間中常時点灯することとなる。
また、当該第１フレームの後半において、液晶層に印加される電圧Ｖは、
Ｖ≒ＭＶ1−Ｖ1
となり、単位時間（＝１フレーム）当たりの実効電圧である印加電圧Ｖが所定の液晶層のオン電圧（ＶON）以上となって当該画素が当該第１フレームの後半期間中常時非点灯状態となる。
さらに、図１０（ｂ）に示すように、１対のフレーム群を構成する第２フレームの前半においては、コモン電圧として第２選択時電圧ＭＶ2が印加され、後半においては、コモン電圧として第１選択時電圧Ｖ2が印加される。
他方、セグメント電極には、同時に走査するコモン電極Ｃ1〜Ｃ4に対応する画素の点灯、非点灯並びにコモン電極の印加電圧波形に対応する波形に基づく電圧（図１０（ｂ）では、その平均電圧としてＶ1を図示している。）が印加される。
【００３９】
この結果、当該第１フレームの前半において、液晶層に印加される電圧Ｖは、
Ｖ≒Ｖ1−ＭＶ2
となり、単位時間（＝１フレーム）当たりの実効電圧である印加電圧Ｖが所定の液晶層のオン電圧（ＶON）以上となって当該画素が当該第２フレームの前半期間中常時点灯することとなる。
また、当該第１フレームの後半において、液晶層に印加される電圧Ｖは、
Ｖ≒ＭＶ1−Ｖ1
となり、単位時間（＝１フレーム）当たりの実効電圧である印加電圧Ｖが所定の液晶層のオン電圧（ＶON）以上となって当該画素が当該第２フレームの後半期間中常時非点灯状態となる。
これらの結果、上記一対のフレーム群をユーザが視認すると、残像効果により当該コモン電極に対応するラインが液晶表示パネル１１上に表示されることとなる。
【００４０】
［３．４］ 第３実施形態の効果
本第３実施形態によれば、図４（ｂ）に示したような通常駆動の表示に対し、上記３つの態様の表示制御を行うことにより、例えば、上記非選択領域における画素点灯動作を二つのコモン電極について行えば、図４（ｃ）に示したように、液晶表示パネルの表示画面には、２本のラインを引くことができ、デザイン的により好ましいものとなる。
さらにこの場合においても、図４（ａ）に示すような選択領域において、点灯／非点灯制御を行う場合と比較して、図４（ｂ）に示すような非選択領域において点灯制御を行う方式によれば、消費電力を低減することができる。
【００４１】
［４］ 実施形態の効果
以上の説明のように各実施形態によれば、部分駆動を行う場合においても、消費電力を不必要に増加させることなく、表示画面のデザインの自由度が向上し、ユーザにとってより好ましい画面表示を行うことが可能となる。
さらに非選択領域における強制的な画素点灯動作を行わない場合と比較して、消費電力があまり変わらないので、部分駆動の恩恵を受け、電池駆動の情報機器などにおいて、長時間の駆動が可能となる。
【００４２】
【発明の効果】
以上の説明のように、本発明によれば、非選択状態にある画素に対応する走査電極に印加する電圧を当該画素の実効印加電圧が当該画素のオン電圧を超過するように設定するので、選択した走査電極に沿った画素を消費電力をあまり増大させることなく点灯状態とすることができる。
従って、消費電力を低減しつつ、より柔軟でデザイン的に好ましい表示画面を表示することが可能となる。
【図面の簡単な説明】
【図１】実施形態の液晶表示装置の要部概要構成ブロック図である。
【図２】第１実施形態のコモン電圧切換回路の概要構成図である。
【図３】第１実施形態の動作説明タイミングチャートである。
【図４】実施形態の画面表示例の説明図である。
【図５】各画素のオン電圧及びオフ電圧の説明図である。
【図６】第２実施形態のコモン電圧切換回路の概要構成図である。
【図７】第２実施形態の動作説明タイミングチャートである。
【図８】第３実施形態の動作説明タイミングチャート（その１）である。
【図９】第３実施形態の非選択時コモン電圧切換回路の概要構成図である。
【図１０】第３実施形態の動作説明タイミングチャート（その２）である。
【図１１】第３実施形態の具体的動作説明図である。
【図１２】第３実施形態の具体的動作説明タイミングチャートである。
【符号の説明】
１０…液晶表示装置
１１…液晶表示パネル
１２…液晶駆動回路
１３…液晶駆動電圧発生回路
１４…駆動制御回路
１５…走査側駆動回路
１５Ｂ、１５Ｃ…選択時コモン電圧切換回路
１５Ｄ…非選択時コモン電圧切換回路
１６…信号側駆動回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display driving circuit, a liquid crystal display driving circuit control method, and a liquid crystal display device, and in particular, a partial driving display in which a part of a scanning line unit in a display area of a liquid crystal display screen is in an undriven state. The present invention relates to a liquid crystal display driving circuit, a liquid crystal display driving circuit control method, and a liquid crystal display device.
[0002]
[Prior art]
A multiplex driving method is known as a driving method for a conventional liquid crystal display device.
In this multiplex drive system, a common electrode (= scanning electrode) and a segment electrode (= signal electrode) are crossed in a matrix, and the intersection is formed as one pixel to form a screen, and the common electrode is sequentially arranged for each scanning line. This is a method of performing image display by scanning.
In a liquid crystal display device employing this multiplex drive method, a full-screen drive display mode in which display is performed using all the pixels of the liquid crystal screen, and a desired scan electrode (all of the pixels on the liquid crystal screen to reduce power consumption) A partial drive display mode is known in which a display area corresponding to a scanning line) is always set as a non-selected area, and display is performed using only pixels corresponding to other remaining display areas.
[0003]
More specifically, as shown in FIG. 4A, in a liquid crystal display screen having a display area where the number of display pixels of the liquid crystal panel is 100 × 96 dots (the number of dots in the scanning line direction × the number of dots in the data line direction) In the full screen drive display mode, the entire display area of 100 × 96 dots is used for display as a selection area, and in the partial drive display mode, a display area of 48 × 96 dots is used as a selection area for display. In this case, as shown in FIG. 4B, the 48 × 96 dot display area which is the selection area is changed into a plurality of display areas such as a 12 × 96 dot display area and a 36 × 96 dot display area. It is also possible to divide.
[0004]
[Problems to be solved by the invention]
In the above conventional liquid crystal display device, although power consumption can be reduced, there are many areas not used for display, which is not preferable in terms of design.
However, if the display is performed with the non-selected area reduced, the power consumption will increase, resulting in falling over at the end.
Accordingly, an object of the present invention is to provide a liquid crystal display device capable of displaying a more flexible and design-friendly display screen while reducing power consumption, and a method for controlling the liquid crystal display device.
[0005]
[Means for Solving the Problems]
  In order to solve the above-described problem, the configuration according to claim 1 is driven by applying a voltage to the liquid crystal layer constituting the liquid crystal display panel via the scan electrode and the signal electrode, and a part of all the scan electrodes. In a liquid crystal display driving circuit capable of causing a pixel corresponding to a scan electrode to be in a non-selected state and a pixel corresponding to the remaining scan electrode to be in a selected state and performing various displays using the selected pixel. Of the scanning electrodes, according to instructions fromSome moreA scan electrode is selected, and a predetermined predetermined value is set so that the effective voltage applied to the liquid crystal layer of the pixel corresponding to the selected scan electrode exceeds the ON voltage of the pixel.ChoiceApply voltage to the selected scan electrodeOn the other hand, a predetermined non-selection voltage that is set in advance so that the effective voltage applied to the liquid crystal layer of the corresponding pixel is equal to or lower than the off-voltage of the pixel is applied to the scanning electrodes other than the part of the scanning electrodes.A forced lighting voltage applying means is provided.
[0006]
  According to a second aspect of the present invention, the liquid crystal layer constituting the liquid crystal display panel is driven by applying a voltage to the liquid crystal layer via the scan electrode and the signal electrode, and pixels corresponding to a part of the scan electrodes among all the scan electrodes are provided. In a liquid crystal display driving circuit that can be in a non-selected state, select pixels corresponding to the remaining scanning electrodes, and perform various displays using the pixels in the selected state. Of the scanning electrodes,Some moreA scan electrode is selected, and a predetermined predetermined value is set so that an integral effective voltage applied within a unit time for a pixel corresponding to the selected scan electrode exceeds an ON voltage of the pixel.ChoiceApply voltage to the selected scan electrodeOn the other hand, for the scanning electrodes other than the part of the scanning electrodes, a predetermined non-selection voltage determined in advance so that the integrated effective voltage applied to the corresponding pixel within a unit time is equal to or lower than the off-voltage of the pixel. ApplyA forced lighting voltage applying means is provided.
[0007]
According to a third aspect of the present invention, in the configuration according to the first aspect, the forced lighting voltage applying unit is configured so that a sign of a voltage difference of the predetermined voltage with respect to a predetermined reference voltage is inverted every frame. It is characterized by applying a voltage of.
[0008]
According to a fourth aspect of the present invention, in the configuration of the second aspect, the forced lighting voltage applying unit inverts the sign of the voltage difference of the predetermined voltage with respect to a predetermined reference voltage at a predetermined timing within one frame. The predetermined voltage is applied as described above.
[0009]
  According to the fifth aspect of the present invention, the liquid crystal layer constituting the liquid crystal display panel is driven by applying a voltage to the liquid crystal layer via the scan electrode and the signal electrode, and pixels corresponding to a part of the scan electrodes among all the scan electrodes are provided. In a control method of a liquid crystal display driving circuit that can be in a non-selected state, select pixels corresponding to the remaining scan electrodes, and perform various displays using the pixels in the selected state, according to an instruction from the outside Among the partial scan electrodes,Some moreA scan electrode is selected, and a predetermined predetermined value is set so that the effective voltage applied to the liquid crystal layer of the pixel corresponding to the selected scan electrode exceeds the ON voltage of the pixel.ChoiceApply voltage to the selected scan electrodeOn the other hand, a predetermined non-selection voltage that is set in advance so that the effective voltage applied to the liquid crystal layer of the corresponding pixel is equal to or lower than the off-voltage of the pixel is applied to the scanning electrodes other than the part of the scanning electrodes.A forced lighting voltage application step is provided.
[0010]
  According to a sixth aspect of the present invention, the liquid crystal layer constituting the liquid crystal display panel is driven by applying a voltage to the liquid crystal layer via the scan electrode and the signal electrode, and pixels corresponding to some of the scan electrodes among all the scan electrodes are provided. In a control method of a liquid crystal display driving circuit that can be in a non-selected state, select pixels corresponding to the remaining scan electrodes, and perform various displays using the pixels in the selected state, according to an instruction from the outside Among the partial scan electrodes,Some moreA scan electrode is selected, and a predetermined predetermined value is set so that an integral effective voltage applied within a unit time for a pixel corresponding to the selected scan electrode exceeds an ON voltage of the pixel.ChoiceApply voltage to the selected scan electrodeOn the other hand, for the scanning electrodes other than the part of the scanning electrodes, a predetermined non-selection voltage determined in advance so that the integrated effective voltage applied to the corresponding pixel within a unit time is equal to or lower than the off-voltage of the pixel. ApplyA forced lighting voltage application step is provided.
[0011]
According to a seventh aspect of the present invention, there is provided a liquid crystal display panel having scanning electrodes and signal electrodes, and a liquid crystal display driving circuit according to the first or second aspect.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic block diagram of a liquid crystal display device.
The liquid crystal display device 10 is roughly classified into a liquid crystal display panel 11 that displays various images, a liquid crystal drive circuit 12 that actually drives the liquid crystal display panel 11, and the liquid crystal drive circuit 12 that actually drives the liquid crystal display panel 11. A liquid crystal drive voltage generation circuit 13 for generating a drive voltage used for the purpose, and a drive control circuit 14 for controlling the liquid crystal drive circuit 12 and the liquid crystal drive voltage generation circuit based on display data and control data for various controls input from the outside. And is configured.
The liquid crystal driving circuit 12 includes a scanning side driving circuit 15 that drives L scanning electrodes (common electrodes) CL (L = 1, 2, 3, 4,...; See FIG. 11) of the liquid crystal display panel 11, and a liquid crystal. And a signal-side drive circuit 16 for driving M signal electrodes (segment electrodes) SM (M = 1, 2, 3, 4,...; See FIG. 11) of the display panel 11.
In the following description, the number of scanning lines of the liquid crystal display panel is 100 lines (number of common electrodes = 100; L = 1 to 100), and the number of signal lines is 96 lines (number of segment electrodes = 96; M = 1 to 96). The case will be described as an example.
Further, when the liquid crystal display panel 11 is partially driven, the common voltage applied to the scan electrodes corresponding to the non-selected regions is fixed to a predetermined voltage set in advance.
[0013]
[1] First embodiment
First, as a first embodiment, a multiplex drive type liquid crystal display device will be described as an example.
FIG. 2 shows a common voltage switching circuit for switching the common voltage in the scanning side drive circuit 15 of the first embodiment.15BThe outline structure of is shown.
The common voltage switching circuit 15B turns on one of the transistor switches T1 to T4 based on a control signal SC from the control unit 15A in the scanning side drive circuit 15 to turn on the common electrode CL (L = 1, 2, 3,. 4... Are selectively selected as a common voltage VCMN from among the first selection voltage V0, the first non-selection voltage V4, the second selection voltage V5 and the second non-selection voltage V1. It is configured to output.
Among these four voltages, any one of the first selection voltage V0, the first non-selection voltage V4, the second selection voltage V5, and the second non-selection voltage V1 is predetermined in the selected region. The first non-selection voltage V4 or the second non-selection voltage V1 is alternately selected in units of frames in the non-selection area.
Further, when line display is performed in the non-selected region, which is a feature of the present invention, the first selection voltage V0 or the second selection voltage V5 is alternately selected in units of frames.
The potential relationship among the first selection voltage V0, the first non-selection voltage V4, the second selection voltage V5, and the second non-selection voltage V1 is as follows.
V0> V1> V4> V5
| V0−V4 | = | V1−V5 |
| V0−V1 | = | V4−V5 |
[0014]
[1.1] Operation of the first embodiment
Next, the operation of the first embodiment will be described.
The drive control circuit 14 of the liquid crystal display device 10 includes a liquid crystal drive circuit 12 and a liquid crystal drive voltage generation circuit 13 based on display data and various control data input from an external personal computer or a control device of a portable information device. To control.
As a result, the liquid crystal drive voltage generation circuit 13 generates a drive voltage used by the liquid crystal drive circuit 12 to actually drive the liquid crystal display panel 11 and supplies the drive voltage to the liquid crystal drive circuit 12.
On the other hand, the liquid crystal drive circuit 12 controls the scanning side drive circuit 15 and the signal based on the drive voltage used to actually drive the liquid crystal display panel 11 supplied from the liquid crystal drive voltage generation circuit 13 under the control of the drive control circuit 14. The side drive circuit 16 drives the liquid crystal display panel 11.
[0015]
[1.2] Specific operation of the first embodiment
Next, a specific operation will be described with reference to FIG.
[1.2.1] Pixel lighting operation in selected area
FIG. 3A is a waveform explanatory diagram for explaining the pixel lighting operation in the selected region. FIG. 3A shows a voltage application state with respect to the liquid crystal layer constituting the pixel at the intersection of the common electrode C1 and the segment electrode S1 for the sake of simplicity.
As shown in FIG. 3A, in the first frame constituting a pair of frame groups, at the timing TC1 corresponding to the segment electrode S1, the first selection voltage V0 is applied as the common voltage, and the other timings. The first non-selection voltage V4 is applied as a common voltage.
On the other hand, the data voltage V3 is applied to the segment electrodes during one frame period.
As a result, at the timing TC1, the voltage V applied to the liquid crystal layer is
V = V0−V3
Thus, the applied voltage V becomes equal to or higher than a predetermined liquid crystal layer ON voltage (VON; see FIG. 5), and the pixel is lit. The ON voltage VON in this case is an integrated effective voltage (average voltage) applied to each liquid crystal layer (the same applies hereinafter).
[0016]
Thereafter, in the second frame constituting the pair of frame groups, the second selection time voltage V5 is applied as the common voltage at the timing TC1 ′ corresponding to the segment electrode S1, and the second voltage is used as the common voltage at other timings. Non-selection voltage V1 is applied.
On the other hand, the data voltage V2 is applied to the segment electrodes during one frame period.
As a result, at timing TC1 ', the voltage V applied to the liquid crystal layer is
V = V2-V5
In this case, the applied voltage V also becomes equal to or higher than the predetermined on-voltage (VON) of the liquid crystal layer, and the pixel is lit.
[0017]
[1.2.2] Pixel non-lighting operation in non-selected area
FIG. 3B is a waveform explanatory diagram for explaining the pixel non-lighting operation in the non-selected region. FIG. 3B also shows a voltage application state with respect to the liquid crystal layer constituting the pixel at the intersection of the common electrode C1 and the segment electrode S1 for the sake of simplicity of explanation.
As shown in FIG. 3B, the first non-selection voltage V4 is applied as the common voltage in the first frame constituting a pair of frame groups.
On the other hand, the data voltage V3 is applied to the segment electrodes during one frame period.
As a result, in the first frame, the voltage V applied to the liquid crystal layer is
V = V4−V3
Thus, the applied voltage V becomes equal to or lower than a predetermined liquid crystal layer off-voltage (VOFF; see FIG. 5), and the pixel is not lit. The off voltage VOFF in this case is an integrated effective voltage (average voltage) applied to each liquid crystal layer (the same applies hereinafter).
Thereafter, in the second frame constituting the pair of frames, the second non-selection voltage V1 is applied as the common voltage.
On the other hand, the data voltage V2 is applied to the segment electrode SM during one frame period.
As a result,The second frame, The voltage V applied to the liquid crystal layer is
V = V1-V2
In this case as well, the applied voltage V becomes equal to or lower than a predetermined liquid crystal layer off-voltage (VOFF), and the pixel is not lit.
[0018]
[1.2.3] Pixel lighting operation in non-selected area
FIG. 3C is a waveform explanatory diagram for explaining the pixel forced lighting operation in the non-selected region, which is a feature of the present application. 3C also shows a voltage application state with respect to the liquid crystal layer constituting the pixel at the intersection of the common electrode C1 and the segment electrode S1 for the sake of simplicity of explanation.
As shown in FIG. 3C, the first selection voltage V0 is applied as a common voltage in the first frame constituting a pair of frame groups.
On the other hand, the data voltage V3 is applied to the segment electrodes during one frame period.
As a result, in the first frame, the voltage V applied to the liquid crystal layer is
V = V0−V3
Thus, the applied voltage V becomes equal to or higher than a predetermined ON voltage (VON) of the liquid crystal layer, and the pixel is always lit during the first frame period.
Thereafter, the second selection time voltage V5 is applied as the common voltage in the second frame constituting the pair of frames.
On the other hand, the data voltage V2 is applied to the segment electrodes during one frame period.
As a result,The second frame, The voltage V applied to the liquid crystal layer is
V = V2-V5
In this case, the applied voltage V is also equal to or higher than a predetermined liquid crystal layer ON voltage (VON), and the pixel is always lit during the second frame period.
[0019]
[1.3] Effects of the first embodiment
By performing the display control of the above three modes for the normal drive display as shown in FIG. 4A, for example, if the pixel lighting operation in the non-selected region is performed for two common electrodes, FIG. As shown in c), two lines (non-selected region forced lighting) can be drawn on the display screen of the liquid crystal display panel, which is more preferable in terms of design.
Further, in this case, in the non-selection area as shown in FIG. 4B, as compared with the case where the lighting / non-lighting control is performed in the selection area as shown in FIG. According to the method for performing the lighting control as shown in FIG. 4, power consumption can be reduced.
[0020]
More specifically, assuming that the current consumption required for driving when assigning 48 lines out of 100 scanning lines of the liquid crystal display panel 11 as a selection region is 10 [μA], display of two lines is performed by normal driving. Current consumption when adding
10 [μA] × 50 [line] / 48 [line] = 10.4 [μA]
It becomes.
On the other hand, the consumption current I required when performing forced lighting as shown in FIG. 4C is as follows.
The consumption current I required for driving one pixel of liquid crystal is assumed that the frame frequency is f, the capacitance of the liquid crystal layer is C, the applied voltage between the common electrode and the segment electrode is VCS, and the number of pixels in the horizontal direction is NPICT. ,
I = f ・ C ・ VCS ・ NPICT
It becomes.
At this time, the capacitance of the liquid crystal layer is different between the capacitance CON when the pixel is lit and the capacitance COFF when the pixel is not lit, and has the following values, for example.
CON = 1.0 [pF]
COFF = 0.6 [pF]
[0021]
So, for example,
f = 60 [Hz]
VCS = 3.8 [V]
Then, in the case of the above example,
NPICT = 96 [pixels]
Therefore, the current ION when the pixel is lit and the current IOFF when the pixel is not lit are as follows.
ION = 0.02 [μA]
IOFF 0.033 [μA]
As a result, in the non-selected region, the difference current ΔI between when the pixel is lit and when the pixel is not lit is

It becomes.
Therefore, the current consumption when adding a 2-line display is
10 [μA] +0.013 [μA] × 2 [line] = 10.026 [μA]
Thus, it can be seen that the power consumption is lower than that of the conventional driving method.
[0022]
[2] Second embodiment
Next, as a second embodiment, another multiplex drive type liquid crystal display device will be described as an example.
In the first embodiment, the positive voltage or the negative voltage is used as the applied voltage. In the second embodiment, both the positive applied voltage and the negative applied voltage are used as applied voltages. In this embodiment, the voltage is used, and the device configuration is the same as that of the first embodiment, and thus detailed description thereof is omitted.
FIG. 6 shows a schematic configuration of a common voltage switching circuit for switching the common voltage in the scanning side drive circuit 15 of the second embodiment.
The common voltage switching circuit 15C turns on one of the transistor switches T1 to T3 based on a control signal SC from the control unit 15A in the scanning side drive circuit 15, and sets the common selection voltage V1 to the common electrode CX. One of the selection voltage V5 and the second selection voltage −V1 is selectively output as the common voltage VCMN.
Among these three voltages, one of the first selection voltage V1, the non-selection voltage V5, and the second selection voltage -V1 is selected according to a predetermined voltage pattern in the selected region, and in the non-selected region The unselected voltage V5 is selected.
Further, when line display is performed in the non-selected region, which is a feature of the present invention, the first selection voltage V1 or the second selection voltage -V1 is alternately selected in units of frames.
The potential relationship among the first selection voltage V1, the non-selection voltage V5, and the second selection voltage -V1 is as follows.
V1> V5> -V1
| V1−V5 | = | V5 − (− V1) |
[0023]
[2.1] Specific operation of the second embodiment
Next, a specific operation of the second embodiment will be described. In this case, the general operation of the liquid crystal display device 10 is the same as that of the first embodiment, and thus detailed description thereof is omitted.
[2.1.1] Pixel lighting operation in selected area
FIG. 7A is a waveform explanatory diagram for explaining the pixel lighting operation in the selected region. FIG. 7A shows a voltage application state with respect to the liquid crystal layer constituting the pixel at the intersection of the common electrode C1 and the segment electrode S1 for the sake of simplicity of explanation.
In the following description:
As shown in FIG. 7A, in the first frame constituting a pair of frame groups, the first selection time voltage V1 is applied as the common voltage at the timing TC1 corresponding to the segment electrode S1, and the other timings. In FIG. 5, the non-selection voltage V5 is applied as a common voltage.
On the other hand, the data voltage V4 is applied to the segment electrodes during one frame period.
[0024]
As a result, at the timing TC1, the voltage V applied to the liquid crystal layer is
V = V1-V4
Thus, the applied voltage V becomes equal to or higher than the ON voltage (VON) of the predetermined liquid crystal layer, and the pixel is turned on.
Thereafter, in the second frame constituting the pair of frame groups, the second selection voltage −V1 is applied as the common voltage at the timing TC1 ′ corresponding to the segment electrode S1, and the common voltage is not used at other timings. When selected, the voltage V4 is applied.
On the other hand, the data voltage -V4 is applied to the segment electrode during one frame period.
As a result, at timing TC1 ', the voltage V applied to the liquid crystal layer is
V = −V4 − (− V1)
In this case, the applied voltage V also becomes equal to or higher than the predetermined on-voltage (VON) of the liquid crystal layer, and the pixel is lit.
[0025]
[2.1.2] Pixel non-lighting operation in non-selected area
FIG. 7B shows a waveform explanatory diagram for explaining the pixel lighting operation in the selected region. FIG. 7B also shows a voltage application state with respect to the liquid crystal layer constituting the pixel at the intersection of the common electrode C1 and the segment electrode S1 for the sake of simplicity.
As shown in FIG. 7B, in the pixel non-lighting operation in the non-selected region, the non-selection voltage V5 is applied as a common voltage in the first frame and the second frame constituting a pair of frame groups.
On the other hand, the data voltage V4 is applied to the segment electrode during the first frame period.
As a result, the voltage V applied to the liquid crystal layer in the first frame is
V = V5−V4
Thus, the applied voltage V becomes equal to or lower than a predetermined liquid crystal layer OFF voltage (VOFF), and the pixel is in a non-lighting state.
Thereafter, in the second frame, the data voltage -V4 is applied to the segment electrode during one frame period.
As a result,The second frame, The voltage V applied to the liquid crystal layer is
V = V5 − (− V4)
In this case as well, the applied voltage V becomes equal to or lower than a predetermined liquid crystal layer off-voltage (VOFF), and the pixel is not lit.
[0026]
[2.1.3] Pixel lighting operation in non-selected area
FIG. 7C is a waveform explanatory diagram for explaining the pixel forced lighting operation in the non-selected region, which is a feature of the present application. FIG. 7C also shows a voltage application state with respect to the liquid crystal layer constituting the pixel at the intersection of the common electrode C1 and the segment electrode S1 for the sake of simplicity of explanation.
As shown in FIG. 7B, the first selection voltage V1 is applied as the common voltage in the first frame constituting the pair of frame groups.
On the other hand, the data voltage V4 is applied to the segment electrodes during one frame period.
As a result, in the first frame, the voltage V applied to the liquid crystal layer is
V = V1-V4
Thus, the applied voltage V becomes equal to or higher than a predetermined ON voltage (VON) of the liquid crystal layer, and the pixel is always lit during the first frame period.
Thereafter, in the second frame constituting the pair of frame groups, the second selection voltage -V1 is applied as the common voltage.
On the other hand, the data voltage -V4 is applied to the segment electrode during one frame period.
As a result,The second frame, The voltage V applied to the liquid crystal layer is
V = −V4 − (− V1)
In this case, the applied voltage V is also equal to or higher than a predetermined liquid crystal layer ON voltage (VON), and the pixel is always lit during the second frame period.
[0027]
[2.2] Effects of the second embodiment
According to the second embodiment, for example, two pixel lighting operations in the non-selected region are performed by performing the display control of the above three modes for the normal drive display as shown in FIG. If the operation is performed for the common electrode, as shown in FIG. 4C, two lines can be drawn on the display screen of the liquid crystal display panel, which is more preferable in terms of design.
Furthermore, in this case, the lighting control is performed in the non-selected area as shown in FIG. 4B, compared with the case where the lighting / non-lighting control is performed in the selected area as shown in FIG. According to this, power consumption can be reduced.
[0028]
[3] Third embodiment
In each of the above embodiments, the liquid crystal is driven by a multiplex method, but the third embodiment is an embodiment in the case of driving a liquid crystal by a multiline scan (MLS) method. Unlike the multiplex method, the multi-line scan method is a driving method that sequentially scans a plurality of common electrodes while simultaneously scanning a plurality of common electrodes. For example, details are disclosed in International Application WO 93/18501.
In the third embodiment, the apparatus configuration is described as being the same as that of the first embodiment of FIG.
[0029]
[3.1] Pixel lighting / non-lighting operation in selected area
Next, the pixel lighting / non-lighting operation in the selected region will be described.
First, the outline of the pixel lighting / non-lighting operation in the selected region will be described.
FIGS. 8A to 8D show schematic drive waveforms when the common electrode is scanned every four lines by such a multi-line scan method. 8A to 8D, for simplification of illustration, the waveforms of the selection periods in the common electrodes C1 to C4 among all the common electrodes CL (L = 1, 2, 3, 4,...) Are shown. Although illustrated as a rectangular wave, in reality, as will be described later, it is complicated considering the potential state of other common electrodes (for example, common electrodes C1, C3, and C4 with respect to the common electrode C2) that are driven simultaneously. It has a simple waveform.
Also, the waveform of the segment electrode S1 is shown so as not to change in one frame, but actually, as will be described later, four common electrodes that are scanned simultaneously (in the case of the above example, the common electrode) The pixel corresponding to the electrodes C1 to C4) is turned on and off, and has a complicated waveform corresponding to the voltage waveform applied to the common electrode.
For example, in the liquid crystal layer to which a voltage is applied by the common electrode C2 and the segment electrode S1, the integrated value of the voltage difference between the applied voltage of the common electrode C1 and the applied voltage of the segment electrode S1 (which changes momentarily on the time axis) ( Turns on or off according to the effective voltage.
[0030]
[3.1.1] Specific example of pixel lighting / non-lighting operation in selected region
Next, the pixel lighting / non-lighting operation in the selected region will be specifically described with reference to FIG. 1, FIG. 11, and FIG.
As shown in FIG. 11, the liquid crystal display device 10 includes a substrate having a plurality of common electrodes C1, C2,..., CL and a plurality of segment electrodes S1, S2,. A liquid crystal layer is interposed between the substrate and the substrate.
The scanning side driving circuit 15 of the liquid crystal driving circuit 12 outputs a scanning signal toward the common electrode C to drive the liquid crystal display panel 11, and the signal side driving circuit 16 outputs a data signal toward the segment electrode S. Output.
Next, the driving operation of the liquid crystal display device 10 having the above configuration will be described in more detail.
Here, three scanning electrodes are sequentially selected from the plurality of common electrodes C, and the display as shown in FIG. 11 is performed on the liquid crystal display panel 11.
That is, the first three common electrodes C1, C2, C3 Is selected in the selection period t1, a scanning signal as shown in FIG. 12A is applied to these common electrodes C1, C2, C3, and a predetermined data signal is applied to the segment electrode S at the same time.
Next, common electrodes C4, C5, C6 Are selected, and a scanning signal as shown in FIG. 12B is applied to these electrodes in the same manner as described above, and at the same time, a data signal is applied to the segment electrode S. Then, this is sequentially repeated until one frame is selected until all the common electrodes C in FIG. 11 are selected.
Further, the waveform of each scanning signal has a pulse pattern number of 2 in units of time Δt in one selection period t1, where h is the number of selected common electrodes C.^hThe waveform is used.
[0031]
For example, as shown in FIG. 12, the scanning signal formed when three common electrodes C are selected has eight selection periods t1 (2^Three= 8) divided by the time Δt, the common electrode C1 is turned off, the common electrode C2 is turned off, the common electrode C3 is turned off at the first time Δt, and the common electrode C1 is turned off at the next time Δt. The waveform formed by sequentially dividing the common electrode C2 into OFF and the common electrode C3 into ON at eight times Δt is used.
The data signal applied to the segment electrode S is determined by ON / OFF of each dot to be displayed simultaneously (3 dots if 3 lines are driven simultaneously) and the voltage value of the scanning signal applied to the common electrode C. The For example, when the waveform of the scanning signal applied to the simultaneously selected common electrodes C1, C2, and C3 is a positive pulse, it is turned on, and when it is a negative pulse, the display data is turned on / off for each pulse. The data signal is set according to the number of mismatches.
Specifically, in the waveform of the scanning signal to the common electrodes C1, C2, and C3 in FIG. 11, when applying the voltage V2, it is turned on, and when applying the voltage MV2, it is turned off. When the black circle mark is turned on and the white circle mark is turned off, the display of pixels intersecting the segment electrode S1 and the common electrodes C1, C2, C3 in FIG. 11 is turned on, on, and off in order. On the other hand, the initial voltages of the pulse patterns applied to the common electrodes C1, C2, and C3 are off, off, and off, respectively. When the two are compared in order, the number of mismatches is 2. Therefore, the voltage V2 as shown in FIG. 12C is applied to the first pulse pattern of the segment electrode S1.
[0032]
Thus, in FIG. 12, the pulse voltage of MV2 is applied when the number of mismatches is 0, MV1 when it is 1, V1 when it is 2, and V2 when it is 3. The voltage ratio between V1 and V2 is set so that V1: V2 = 1: 2. Further, the second pulse patterns of the voltages applied to the common electrodes C1, C2, and C3 are off, off, and on, respectively, and the pixel display is inconsistent when compared with the on, on, and off in order. Since the number of mismatches is 3, the voltage V2 is applied to the second pulse of the segment electrode S1. Similarly, V1 is applied to the third pulse, MV1 is applied to the fourth pulse, and thereafter, MV2, V1, MV1, and MV1 are applied in this order.
Further, when the next common electrodes C4 to C6 are selected and the voltage shown in FIG. 12B is applied to the common electrodes C4 to C6, the pixels of the intersection of the common electrodes C4 to C6 and the signal electrodes are displayed. A data signal having a voltage level corresponding to the mismatch between the on / off display and the on / off of the pulse patterns applied to the common electrodes C4 to C6 is applied as shown in FIG. FIG. 12D shows a waveform applied to a pixel where the common electrode C1 and the segment electrode S1 intersect, that is, a combined waveform of a scanning signal applied to the common electrode C1 and a data signal applied to the segment electrode S1. It is.
As described above, in the multi-line scanning method in which a plurality of scanning electrodes are sequentially selected and driven at the same time, an on / off ratio can be realized and a driving voltage can be kept low.
[0033]
[3.2] General configuration of common voltage switching circuit when not selected
FIG. 9 shows a schematic configuration diagram of a non-selected common voltage switching circuit that switches a common voltage when the scanning side drive circuit 15 is not selected.
The non-selection common voltage switching circuit 15D turns on one of the transistor switches T1 to T3 based on the control signal SC from the control unit 15A in the scanning side drive circuit 15 and applies the non-selection voltage VC to the common electrode CX. The first selection voltage V2 and the second selection voltage MV2 are selectively output as the common voltage VCMN. Among these three voltages, one of the first selection voltage V2, the non-selection voltage VC, and the second selection voltage MV2 is selected according to a predetermined voltage pattern in the selected region, and in the non-selected region, The non-selection voltage VC is selected.
Further, when line display is performed in the non-selected region, which is a feature of the present invention, the first selection voltage V2 or the second selection voltage MV2 is alternately selected in units of 1/2 frame. The 1/2 frame unit is easy to control and consumes less power (because of the low frequency), but is not limited to this, and is not limited to 1/4 frame unit, 1/8 frame unit, ...... 1/2 etc.ⁿIt is possible to configure to select alternately in units of frames.
In this case, the potential relationship among the first selection voltage V2, the non-selection voltage VC, the second selection voltage MV2, and the voltages V1 and MV1 is as follows.
V1 = V2 / 2
MV1 = MV2 / 2
V2> VC> MV2
| V2−VC | = | VC−MV2 |
[0034]
[3.3] Specific operation of the third embodiment
Next, a specific operation of the third embodiment will be described. In this case, the general operation of the liquid crystal display device 10 is the same as that of the first embodiment, and thus detailed description thereof is omitted.
Further, in the following description, for simplification of description, the description will focus on the state of voltage application to the liquid crystal layer constituting the pixel at the intersection of the common electrode C1 and the segment electrode S1.
[0035]
[3.3.1] Pixel non-lighting operation in non-selected area
As described above, the waveform of the segment electrode S1 is a complex waveform corresponding to the lighting and non-lighting of the pixels corresponding to the common electrodes C1 to C4 that are scanned simultaneously and the voltage waveform applied to the common electrode.
Therefore, the effective voltage (= integrated effective voltage) between the common electrode C1 and the common electrode C1 may be prevented from exceeding the ON voltage with respect to all the predicted segment electrode S1 waveforms.
For this reason, the pixel non-lighting operation in the non-selected region is performed by applying the non-selection time voltage VC as a common voltage in the first frame and the second frame constituting a pair of frame groups as shown in FIG. Is done.
On the other hand, the segment electrode S1 has a voltage based on the waveform corresponding to the waveform of the voltage applied to the common electrodes C1 to C4 that are simultaneously scanned, and the lighting of the pixels corresponding to the common electrodes C1 to C4. V1 is shown in the figure).
[0036]
As a result, the voltage V applied to the liquid crystal layer in the first frame is
V ≒ V1-VC
Thus, the applied voltage V becomes equal to or lower than the predetermined liquid crystal layer OFF voltage (VOFF), and the pixel is in a non-lighting state.
Thereafter, in the second frame, the segment electrodes are supplied with voltages based on waveforms corresponding to the lighting and non-lighting of the pixels corresponding to the common electrodes C1 to C4 that are scanned simultaneously and the voltage waveform applied to the common electrodes (FIG. 10A). Then, MV1 is shown as the average voltage).
As a result, the voltage V applied to the liquid crystal layer in the first frame is
V ≒ VC-MV1
Thus, the applied voltage V becomes equal to or lower than the predetermined liquid crystal layer OFF voltage (VOFF), and the pixel is in a non-lighting state.
[0037]
[3.3.2] Pixel lighting operation in non-selected area
FIG. 10B is a waveform explanatory diagram for explaining the pixel forced lighting operation in the non-selected region, which is a feature of the present application. FIG. 10B also shows a voltage application state with respect to the liquid crystal layer constituting the pixel at the intersection of the common electrode C1 and the segment electrode S1 for the sake of simplicity of explanation.
As shown in FIG. 10B, the first selection voltage MV2 is applied as the common voltage in the first half of the first frame constituting the pair of frame groups, and the first selection is performed as the common voltage in the second half. The hour voltage V2 is applied.
On the other hand, the segment electrode includes a voltage based on a waveform corresponding to a voltage waveform corresponding to the voltage applied to the common electrode C1 to C4 that are simultaneously scanned, and an average voltage in FIG. 10B. V1 is shown.) Is applied.
[0038]
As a result, in the first half of the first frame, the voltage V applied to the liquid crystal layer is
V ≒ V1−MV2
Thus, the applied voltage V, which is an effective voltage per unit time (= 1 frame), becomes equal to or higher than the ON voltage (VON) of the predetermined liquid crystal layer, and the pixel is always lit during the first half period of the first frame. .
In the second half of the first frame, the voltage V applied to the liquid crystal layer is
V ≒ MV1-V1
Thus, the applied voltage V, which is an effective voltage per unit time (= 1 frame), is equal to or higher than the ON voltage (VON) of the predetermined liquid crystal layer, and the pixel is always in the non-lighting state during the latter half of the first frame. .
Further, as shown in FIG. 10B, the first selection voltage MV2 is applied as the common voltage in the first half of the second frame forming the pair of frame groups, and the first common voltage is used in the second half. When selected, voltage V2 is applied.
On the other hand, the segment electrode includes a voltage based on a waveform corresponding to a voltage waveform corresponding to the voltage applied to the common electrode C1 to C4 that are simultaneously scanned, and an average voltage in FIG. 10B. V1 is shown.) Is applied.
[0039]
As a result, in the first half of the first frame, the voltage V applied to the liquid crystal layer is
V ≒ V1−MV2
Thus, the applied voltage V, which is an effective voltage per unit time (= 1 frame), becomes equal to or higher than the ON voltage (VON) of the predetermined liquid crystal layer, and the pixel is always lit during the first half period of the second frame. .
In the second half of the first frame, the voltage V applied to the liquid crystal layer is
V ≒ MV1-V1
Thus, the applied voltage V, which is an effective voltage per unit time (= 1 frame), is equal to or higher than the ON voltage (VON) of the predetermined liquid crystal layer, and the pixel is always in the non-lighting state during the second half of the second frame. .
As a result, when the user visually recognizes the pair of frames, a line corresponding to the common electrode is displayed on the liquid crystal display panel 11 due to the afterimage effect.
[0040]
[3.4] Effects of the third embodiment
According to the third embodiment, by performing the display control of the above three modes with respect to the normal drive display as shown in FIG. If two common electrodes are used, as shown in FIG. 4C, two lines can be drawn on the display screen of the liquid crystal display panel, which is more preferable in terms of design.
Furthermore, in this case, the lighting control is performed in the non-selected area as shown in FIG. 4B, compared with the case where the lighting / non-lighting control is performed in the selected area as shown in FIG. According to this, power consumption can be reduced.
[0041]
[4] Effects of the embodiment
As described above, according to each embodiment, even when partial driving is performed, the degree of freedom in design of the display screen is improved without unnecessarily increasing power consumption, and a screen display that is more preferable for the user is achieved. Can be done.
In addition, compared to the case where forced pixel lighting operation is not performed in the non-selected region, the power consumption is not much different, so it can benefit from partial driving and can be driven for a long time in battery-driven information devices, etc. Become.
[0042]
【The invention's effect】
As described above, according to the present invention, the voltage applied to the scan electrode corresponding to the pixel in the non-selected state is set so that the effective applied voltage of the pixel exceeds the on-voltage of the pixel. The pixels along the selected scan electrode can be turned on without significantly increasing power consumption.
Accordingly, it is possible to display a more flexible and design-friendly display screen while reducing power consumption.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of a main part of a liquid crystal display device according to an embodiment.
FIG. 2 is a schematic configuration diagram of a common voltage switching circuit according to the first embodiment.
FIG. 3 is an operation explanation timing chart of the first embodiment.
FIG. 4 is an explanatory diagram of a screen display example of the embodiment.
FIG. 5 is an explanatory diagram of an on voltage and an off voltage of each pixel.
FIG. 6 is a schematic configuration diagram of a common voltage switching circuit according to a second embodiment.
FIG. 7 is an operation explanation timing chart of the second embodiment.
FIG. 8 is an operation explanation timing chart (No. 1) of the third embodiment;
FIG. 9 is a schematic configuration diagram of a non-selected common voltage switching circuit according to a third embodiment.
FIG. 10 is an operation explanation timing chart (2) of the third embodiment;
FIG. 11 is a diagram illustrating a specific operation of the third embodiment.
FIG. 12 is a timing chart illustrating the specific operation of the third embodiment.
[Explanation of symbols]
10. Liquid crystal display device
11 ... Liquid crystal display panel
12 ... Liquid crystal drive circuit
13 ... Liquid crystal drive voltage generation circuit
14 ... Drive control circuit
15 ... Scanning side drive circuit
15B, 15C ... Common voltage switching circuit when selected
15D: Common voltage switching circuit when not selected
16: Signal side drive circuit

Claims (7)

The liquid crystal layer constituting the liquid crystal display panel is driven by applying a voltage to the liquid crystal layer through the scan electrode and the signal electrode, and pixels corresponding to some of the scan electrodes among all the scan electrodes are set in a non-selected state, and the remaining scans are performed. In a liquid crystal display driving circuit capable of performing various displays using a pixel corresponding to an electrode as a selected state and using the pixel in the selected state,
Of the scanning electrodes of the part, according to instructions from the outside,
Further, a part of the scan electrodes is selected, and the predetermined selection voltage set in advance so that the effective voltage applied to the liquid crystal layer of the pixel corresponding to the selected scan electrode exceeds the ON voltage of the pixel is selected. While applying to the scan electrode ,
For the scanning electrodes other than the scanning electrodes, the forcible lighting is performed by applying a predetermined non-selection voltage that is set in advance so that the effective voltage applied to the liquid crystal layer of the corresponding pixel is equal to or lower than the off-voltage of the pixel. A liquid crystal display driving circuit comprising voltage applying means. The liquid crystal layer constituting the liquid crystal display panel is driven by applying a voltage to the liquid crystal layer through the scan electrode and the signal electrode, and pixels corresponding to some of the scan electrodes among all the scan electrodes are set in a non-selected state, and the remaining scans are performed. In a liquid crystal display driving circuit capable of performing various displays using a pixel corresponding to an electrode as a selected state and using the pixel in the selected state,
Of the scanning electrodes of the part, according to instructions from the outside,
Further, a part of the scan electrodes is selected, and a predetermined selection voltage that is set in advance so that the integral effective voltage applied within a unit time for the pixel corresponding to the selected scan electrode exceeds the ON voltage of the pixel is selected. While applying to selected scan electrodes
Further, for a scan electrode other than the scan electrode, a predetermined non-selection voltage is applied in advance so that the integrated effective voltage applied to the corresponding pixel within a unit time is equal to or lower than the off-voltage of the pixel. A liquid crystal display driving circuit comprising a forced lighting voltage applying means. The liquid crystal display driving circuit according to claim 1.
The liquid crystal display driving circuit, wherein the forced lighting voltage applying unit applies the predetermined voltage so that a sign of a voltage difference of the predetermined voltage with respect to a predetermined reference voltage is inverted every frame. The liquid crystal display driving circuit according to claim 2.
The forced lighting voltage application means applies the predetermined voltage so that a sign of a voltage difference of the predetermined voltage with respect to a predetermined reference voltage is inverted at a predetermined timing within one frame. Driving circuit. The liquid crystal layer constituting the liquid crystal display panel is driven by applying a voltage to the liquid crystal layer via the scanning electrode and the signal electrode, and pixels corresponding to some of the scanning electrodes among all the scanning electrodes are set in a non-selected state, and the remaining scanning is performed. In a control method of a liquid crystal display driving circuit capable of performing various displays using a pixel corresponding to an electrode as a selected state and using the pixel in the selected state,
Of the scanning electrodes of the part, according to instructions from the outside,
Further, a part of the scan electrodes is selected, and the predetermined selection voltage set in advance so that the effective voltage applied to the liquid crystal layer of the pixel corresponding to the selected scan electrode exceeds the ON voltage of the pixel is selected. While applying to the scan electrode ,
For the scanning electrodes other than the scanning electrodes, the forcible lighting is performed by applying a predetermined non-selection voltage that is set in advance so that the effective voltage applied to the liquid crystal layer of the corresponding pixel is equal to or lower than the off-voltage of the pixel. A method for controlling a liquid crystal display drive circuit, comprising a voltage application step. The liquid crystal layer constituting the liquid crystal display panel is driven by applying a voltage to the liquid crystal layer via the scanning electrode and the signal electrode, and pixels corresponding to some of the scanning electrodes among all the scanning electrodes are set in a non-selected state, and the remaining scanning is performed. In a control method of a liquid crystal display driving circuit capable of performing various displays using a pixel corresponding to an electrode as a selected state and using the pixel in the selected state,
Of the scanning electrodes of the part, according to instructions from the outside,
Further, a part of the scan electrodes is selected, and a predetermined selection voltage that is set in advance so that the integral effective voltage applied within a unit time for the pixel corresponding to the selected scan electrode exceeds the ON voltage of the pixel is selected. While applying to selected scan electrodes
Further, for a scan electrode other than the scan electrode, a predetermined non-selection voltage is applied in advance so that the integrated effective voltage applied to the corresponding pixel within a unit time is equal to or lower than the off-voltage of the pixel. A method for controlling a liquid crystal display driving circuit, comprising a step of applying a forced lighting voltage. A liquid crystal display panel having scanning electrodes and signal electrodes;
A liquid crystal display driving circuit according to claim 1 or 2,
A liquid crystal display device comprising:

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