JP2006185592A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device lighting a discharge lamp with an arbitrary luminance in a short time. <P>SOLUTION: This discharge lamp lighting device comprises: a circuit 5 for detecting a tube current I<SB>L</SB>flowing through a cold cathode tube 3; and a light control switching circuit 9 for generating an alternating current output V<SB>L</SB>continuously from an alternating current conversion circuit 2 by invalidating a light control signal V<SB>B</SB>being imparted from a light control signal generating circuit 4 to a light control circuit 7 during an interval T<SB>C</SB>when the tube current detecting circuit 5 does not detect the tube current I<SB>L</SB>and driving the light control circuit 7 when the tube current detecting circuit 5 detects the tube current I<SB>L</SB>. Since the light control signal V<SB>B</SB>being imparted from the light control signal generating circuit 4 to the light control circuit 7 is invalidated by the light control switching circuit 9 when the tube current I<SB>L</SB>scarcely flows into the cold cathode tube 3 at the time of starting, the alternating current output V<SB>L</SB>from the alternating current conversion circuit 2 is fed continuously to the cold cathode tube 3. Consequently, necessary and sufficient exciting energy is fed quickly to the cold cathode tube 3 at the time of starting, and the cold cathode tube 3 is lighted in a short time with an arbitrary luminance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、冷陰極管（ＣＣＦＬ：Ｃold Ｃathode Ｆluorescent Ｌamp）等の放電灯点灯装置、特に放電灯の輝度を調整する調光制御回路を有し且つ短時間で放電灯を任意の輝度で点灯することができる放電灯点灯装置に属する。
【０００２】
【従来の技術】
液晶テレビやノート型パソコン等に搭載される液晶表示装置のバックライト等に使用される冷陰極管等の放電灯点灯装置は公知である。例えば、図５に示す従来の放電灯点灯装置は、十数ボルトの直流電圧Ｖ_INを発生する直流電源(1)と、直流電源(1)の直流電圧Ｖ_INを数百ボルト〜千数百ボルトの交流電圧Ｖ_Lに変換する交流変換回路(2)と、交流変換回路(2)の出力端子に接続された放電管としての冷陰極管(3)と、冷陰極管(3)の調光信号Ｖ_Bを出力する調光信号発生回路(4)と、冷陰極管(3)に流れる管電流Ｉ_Lを検出する管電流検出回路(5)と、管電流検出回路(5)の検出電流値が予め設定された電流値となるように交流変換回路(2)の交流電圧Ｖ_Lを制御する電流制御信号Ｖ_Aを出力する管電流制御回路(6)と、調光信号発生回路(4)の調光信号Ｖ_Bにより管電流制御回路(6)の電流制御信号Ｖ_Aを連続的又は断続的に出力するゲート手段を有する調光制御回路(7)と、調光制御回路(7)の出力信号Ｖ_Dから交流変換回路(2)を駆動する駆動信号Ｖ_Gを形成する駆動回路(8)とを備えている。
【０００３】
図６に示すように、交流変換回路(2)は、直流電源(1)に接続される矩形波電圧発生回路(21)と、矩形波電圧発生回路(21)に接続され且つ１次巻線(22a)と直列に形成される漏洩インダクタンス(22c)を含むリーケージトランス(22)と、リーケージトランス(22)の２次巻線(22b)に接続された共振コンデンサ(23)とを有する。リーケージトランス(22)及び共振コンデンサ(23)は直列共振回路(24)を構成する。ここで、リーケージトランス(22)の１次巻線(22a)及び２次巻線(22b)の巻数をそれぞれＮ₁、Ｎ₂[turn]とすると、リーケージトランス(22)の巻数比Ｎ₂/Ｎ₁は１００程度となるように設定される。詳細な図示は省略するが、矩形波電圧発生回路(21)は、例えば複数のスイッチング素子をブリッジ接続して構成され且つ各スイッチング素子のスイッチング動作により直流電源(1)からの直流電圧Ｖ_INを矩形波交流電圧に変換するスイッチング回路と、１次側巻線にスイッチング回路が接続され且つ２次側巻線から電圧調整された矩形波交流電圧Ｖ_Sを発生する出力トランスとを有する。駆動回路(8)から入力される駆動信号Ｖ_Gにより、前記のスイッチング回路を構成する各スイッチング素子を数十[kHz]程度の周波数でオン・オフ動作させることにより、直流電源(1)から入力される直流電圧Ｖ_INを矩形波交流電圧Ｖ_Sに変換する。矩形波電圧発生回路(21)から出力される矩形波交流電圧Ｖ_Sは、リーケージトランス(22)及び共振コンデンサ(23)で構成される直列共振回路(24)により高圧（数百ボルト〜千数百ボルト）で且つ数十[kHz]程度の周波数の正弦波交流電圧Ｖ_Lに変換され、冷陰極管(3)に供給される。調光信号発生回路(4)は、交流変換回路(2)のスイッチング周波数（数十[kHz]程度）よりも十分に低い一定周波数（数十[Hz]〜数[kHz]）の矩形パルス信号を発生し、冷陰極管(3)の所望の輝度に応じて矩形パルス信号のオン・デューティを変化させることにより、冷陰極管(3)の調光信号Ｖ_Bを出力する。したがって、冷陰極管(3)の輝度が最大のときはオン・デューティ１００[％]の矩形パルス信号、即ち図７(Ａ)に示すように正電圧レベル一定の調光信号Ｖ_Bを出力する。
【０００４】
管電流検出回路(5)は、冷陰極管(3)と直列に接続された管電流検出用抵抗(51)と、アノード端子が冷陰極管(3)と管電流検出用抵抗(51)との接続点に接続された整流ダイオード(52)と、整流ダイオード(52)のカソード端子と接地端子との間に接続された平滑コンデンサ(53)とを有する。即ち、管電流検出回路(5)は、管電流検出用抵抗(51)により冷陰極管(3)に流れる管電流Ｉ_Lをそれに対応する電圧に変換し、管電流検出用抵抗(51)の両端子間の電圧を整流ダイオード(52)及び平滑コンデンサ(53)により整流及び平滑化してその直流電圧を検出電圧Ｖ_Fとして出力する。管電流制御回路(6)は、冷陰極管(3)に流れる管電流Ｉ_Lの設定値を規定する基準電圧Ｖ_R1を発生する基準電源(61)と、管電流検出回路(5)の検出電圧Ｖ_Fと基準電源(61)の基準電圧Ｖ_R1との誤差電圧を増幅した出力電圧Ｖ_E1を出力する誤差増幅器(62)と、一定周波数（数十[kHz]程度）の三角波電圧Ｖ_Tを発生する三角波発振回路(63)と、誤差増幅器(62)の出力電圧Ｖ_E1と三角波発振回路(63)の三角波電圧Ｖ_Tとを比較することによりオン・デューティが変化する矩形パルス列の電流制御信号Ｖ_Aを発生するＰＷＭ（パルス幅変調）コンパレータ(64)とを有する。調光制御回路(7)のゲート手段は、例えば調光信号発生回路(4)の調光信号Ｖ_Bと管電流制御回路(6)の電流制御信号Ｖ_Aとの論理積信号Ｖ_Dを出力するＡＮＤゲート(71)で構成することができる。即ち、調光制御回路(7)は、図７(Ａ)に示すように調光信号発生回路(4)から正電圧レベル一定の調光信号Ｖ_Bが入力されたときは、管電流制御回路(6)からの電流制御信号Ｖ_Aを連続的に出力するため、冷陰極管(3)の輝度の調整、即ち調光動作を行わない。一方、図８(Ａ)に示すように管電流制御回路(6)から出力される電流制御信号Ｖ_Aの周波数（数十[kHz]程度）よりも十分に低い周波数（数十[Hz]〜数[kHz]）で且つ冷陰極管(3)の所望の輝度に対応するデューティ比を有する矩形パルス列の調光信号Ｖ_Bが調光信号発生回路(4)から調光制御回路(7)に入力されたときは、管電流制御回路(6)からの電流制御信号Ｖ_Aを調光信号Ｖ_Bの周期で断続的に出力し、冷陰極管(3)の調光動作を行う。駆動回路(8)は、調光制御回路(7)のＡＮＤゲート(71)から入力される論理積信号Ｖ_Dから交流変換回路(2)内の矩形波電圧発生回路(21)を連続的又は断続的に駆動する駆動信号Ｖ_Gを形成し、矩形波電圧発生回路(21)へ出力する。
【０００５】
図５に示す構成において、図７(Ａ)に示すように装置起動時ｔ₁から調光信号発生回路(4)の調光信号Ｖ_Bが正電圧レベル一定のときは、調光制御回路(7)は調光動作を行わず、管電流制御回路(6)から連続的に出力される電流制御信号Ｖ_Aにより、駆動回路(8)から交流変換回路(2)を連続的に駆動する駆動信号Ｖ_Gが出力される。これにより、図７(Ｂ)に示すように交流変換回路(2)から冷陰極管(3)に連続的に交流電圧Ｖ_Lが印加され、図７(Ｃ)に示すように時刻ｔ₂にて冷陰極管(3)に管電流Ｉ_Lが流れ始めると、冷陰極管(3)が点灯を開始する。時刻ｔ₂以降は、管電流制御回路(6)により冷陰極管(3)に流れる管電流Ｉ_Lが略一定に保持されるので、冷陰極管(3)の輝度が常に最大値一定となる。
【０００６】
また、図８(Ａ)に示すように、管電流制御回路(6)の電流制御信号Ｖ_Aの周波数よりも十分に低い周波数で且つ冷陰極管(3)の所望の輝度に対応するデューティ比を有する矩形パルス列の調光信号Ｖ_Bが調光信号発生回路(4)から出力される場合は、調光制御回路(7)から管電流制御回路(6)の電流制御信号Ｖ_Aを断続的にした出力信号Ｖ_Dが出力される。これにより、調光信号Ｖ_Bの周期で交流変換回路(2)を断続的に駆動する駆動信号Ｖ_Gが駆動回路(8)から出力され、図８(Ｂ)に示すように交流変換回路(2)から冷陰極管(3)に断続的に交流電圧Ｖ_Lが印加される。図８(Ｃ)に示すように、時刻ｔ₂にて冷陰極管(3)に管電流Ｉ_Lが流れ始めると冷陰極管(3)が点灯を開始し、時刻ｔ₂以降は冷陰極管(3)に管電流Ｉ_Lが断続的に流れ続ける。これにより、冷陰極管(3)が調光信号Ｖ_Bの周期で点滅を繰り返すので、調光信号Ｖ_Bのオン・デューティを適宜調整すれば所望の輝度が得られる。これと共に、管電流制御回路(6)により冷陰極管(3)に流れる管電流Ｉ_Lが略一定に保持されるので、冷陰極管(3)の輝度が常に一定となる。以上で述べた放電灯点灯装置の構成と類似の構成を有する放電灯点灯装置は、例えば下記の特許文献１に開示されている。
【０００７】
【特許文献１】
特開２０００−３５７５９９号公報（第６頁、図６）
【０００８】
【発明が解決しようとする課題】
図５に示す従来の放電灯点灯装置では、図８(Ａ)に示すように調光信号発生回路(4)から調光制御回路(7)に予め調光信号Ｖ_Bが入力されているとき、図８(Ｃ)に示すように冷陰極管(3)の管電流Ｉ_Lが検出されない期間Ｔ_Bにおいても図８(Ｂ)に示すように交流変換回路(2)の交流電圧Ｖ_Lが断続的に冷陰極管(3)に印加される。このため、管電流Ｉ_Lが検出されない暗黒始動期間Ｔ_B中に冷陰極管(3)を点灯するのに必要十分な励磁エネルギを交流変換回路(2)から冷陰極管(3)に供給できず、装置起動時ｔ₁から冷陰極管(3)の点灯開始時ｔ₂までの時間Ｔ_Bが交流変換回路(2)の交流電圧Ｖ_Lを連続的に冷陰極管(3)に印加する場合（図７(Ｂ)）の同時間Ｔ_Aに比較して長くなる欠点があった。したがって、冷陰極管(3)を長期間点灯させずに冷暗所に放置した場合の始動不良等の不具合が発生していた。
【０００９】
そこで、本発明は短時間で放電灯を任意の輝度で点灯することができる放電灯点灯装置を提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明による放電灯点灯装置は、直流電源(1)と、少なくとも１つのスイッチング素子を含むスイッチング回路を有し且つスイッチング回路のスイッチング動作により直流電源(1)から供給される直流電力を交流電力に変換する交流変換回路(2)と、交流変換回路(2)の出力端子に接続された放電管(3)と、調光信号発生回路(4)から出力される調光信号(V_B)により交流変換回路(2)の交流出力(V_L)を断続的に発生させて放電管(3)の輝度を調整する調光制御回路(7)とを備え、放電管(3)に流れる管電流(I_L)を検出する管電流検出回路(5)と、管電流検出回路(5)に接続された調光切替回路(9)とを備えている。調光切替回路(9)は、管電流検出回路(5)の検出電流値が基準値より低いときは第１の電圧(L)レベルの出力信号(V_E2)を発生し、管電流検出回路(5)の検出電流値が基準値以上となったときに第２の電圧(H)レベルの出力信号(V_E2)を発生する比較手段(92)と、電源投入時に起動信号(V_P)を発生する起動信号発生手段(93)と、起動信号発生手段(93)が起動信号(V_P)を発生したときに第１の状態となり、比較手段(92)の出力信号(V_E2)が第１の電圧(L)レベルの期間(T_C)は第１の状態を保持し、比較手段(92)の出力信号(V_E2)が第２の電圧(H)レベルとなったときに第２の状態となる状態保持手段(94)と、状態保持手段(94)が第１の状態のときは調光制御回路(7)に付与する調光信号(V_B)を無効にして交流変換回路(2)の交流出力(V_L)を連続的に発生させ、状態保持手段(94)が第２の状態となったときに調光制御回路(7)に調光信号(V_B)を付与する切替手段(95)とを有する。放電管(3)に管電流(I_L)が殆ど流れない起動時は、調光切替回路(9)により調光信号発生回路(4)から調光制御回路(7)に付与する調光信号(V_B)が無効となるため、交流変換回路(2)の交流出力(V_L)が連続的に放電管(3)に供給される。これにより、起動時に必要十分な励磁エネルギが速やかに放電管(3)に供給され、短時間で放電管(3)を任意の輝度で点灯することができる。
【００１１】
本発明の実施の形態では、管電流検出回路(5)の検出電流値が予め設定された電流値となるように交流変換回路(2)の交流出力(V_L)を制御する電流制御信号(V_A)を出力する管電流制御回路(6)を備えている。このため、放電管(3)の点灯開始後、管電流制御回路(6)により放電管(3)に流れる管電流(I_L)が略一定に保持されるので、放電管(3)の輝度が常に一定となる。調光信号発生回路(4)は、交流変換回路(2)のスイッチング周波数よりも十分に低い周波数で且つ放電管(3)の所望の輝度に対応するデューティ比を有する調光信号(V_B)を出力する。調光制御回路(7)は、前記調光切替回路(9)の出力信号(V_C)により前記管電流制御回路(6)の電流制御信号(V_A)を連続的又は断続的に出力するゲート手段(71)を有する。管電流制御回路(6)は、管電流検出回路(5)の検出信号(V_F)の電圧レベルに応じてオン・デューティが変化する電流制御信号(V_A)を出力する。また、管電流検出回路(5)の検出信号(V_F)の電圧レベルに応じて周波数が変化する電流制御信号(V_A)を出力する管電流制御回路(6)を使用してもよい。
【００１２】
【発明の実施の形態】
以下、本発明による放電灯点灯装置の一実施の形態を図１〜図３に基づいて説明する。但し、これらの図面では図５〜図８に示す箇所と実質的に同一の部分には同一の符号を付し、その説明を省略する。
本実施の形態の放電灯点灯装置は、図１に示すように、管電流検出回路(5)が冷陰極管(3)の管電流Ｉ_Lを検出しない期間Ｔ_C（図３）は調光信号発生回路(4)から調光制御回路(7)に付与する調光信号Ｖ_Bを無効にして交流変換回路(2)から連続的に交流電圧Ｖ_Lを発生させ、管電流検出回路(5)が冷陰極管(3)の管電流Ｉ_Lを検出したときに調光制御回路(7)を駆動する調光切替回路(9)を管電流検出回路(5)に接続した点で図５に示す従来の放電灯点灯装置と異なる。
【００１３】
図２に示すように、調光切替回路(9)は、冷陰極管(3)に流れる管電流Ｉ_Lの検出最小値を規定する基準電圧Ｖ_R2を発生する基準電源(91)と、管電流検出回路(5)の検出電圧Ｖ_Fが基準電源(91)の基準電圧Ｖ_R2より低いときに低い電圧(Ｌ)レベルの出力信号Ｖ_E2を発生し、管電流検出回路(5)の検出電圧Ｖ_Fが基準電源(91)の基準電圧Ｖ_R2以上となったときに高い電圧(Ｈ)レベルの出力信号Ｖ_E2を発生する比較手段としてのコンパレータ(92)と、図示しない電源スイッチをオンしたときに単発パルスの起動信号Ｖ_Pを発生する起動信号発生手段としてのワンショットパルス発生器(93)と、ワンショットパルス発生器(93)からリセット端子(R)に起動信号Ｖ_Pが入力されたときにリセット状態となり、コンパレータ(92)の出力信号Ｖ_E2が低い電圧(Ｌ)レベルの期間はリセット状態を保持し、コンパレータ(92)からセット端子(S)に高い電圧(Ｈ)レベルの出力信号Ｖ_E2が入力されたときにセット状態となる状態保持手段としてのＲ-Ｓフリップフロップ(94)と、Ｒ-Ｓフリップフロップ(94)の反転出力信号Ｖ_Qと調光信号発生回路(4)の調光信号Ｖ_Bとの論理和信号Ｖ_Cを出力する切替手段としてのＯＲゲート(95)とを備えている。調光切替回路(9)の基準電源(91)の基準電圧Ｖ_R2は、管電流制御回路(6)の基準電源(61)の基準電圧Ｖ_R1よりも低い値に設定される。また、調光制御回路(7)のＡＮＤゲート(71)は、調光切替回路(9)から出力される論理和信号Ｖ_Cと管電流制御回路(6)から出力される電流制御信号Ｖ_Aとの論理積信号Ｖ_Dを出力する。その他の構成は、図６に示す従来の放電灯点灯装置と略同様である。
【００１４】
上記の構成において、時刻ｔ₁（図３）にて図示しない電源スイッチをオンして電源を投入すると、調光切替回路(9)内のワンショットパルス発生器(93)から単発パルスの起動信号Ｖ_Pが出力され、Ｒ-Ｓフリップフロップ(94)のリセット端子(R)に入力されてＲ-Ｓフリップフロップ(94)がリセット状態となる。これと共に、図３(Ａ)に示すように、管電流制御回路(6)の電流制御信号Ｖ_Aの周波数（数十〜数百[kHz]）よりも十分に低い周波数（数十[Hz]程度）で且つ冷陰極管(3)の所望の輝度に対応するデューティ比を有する矩形パルス列の調光信号Ｖ_Bが調光信号発生回路(4)から出力され、調光切替回路(9)内のＯＲゲート(95)に入力される。図３(Ｄ)に示すように、電源投入時ｔ₁から点灯開始時ｔ₂までの暗黒始動期間Ｔ_C中は冷陰極管(3)に管電流Ｉ_Lが殆ど流れず、管電流検出回路(5)の検出電圧Ｖ_Fが調光切替回路(9)内の基準電源(91)の基準電圧Ｖ_R2よりも低いため、コンパレータ(92)から低い電圧(Ｌ)レベルの出力信号Ｖ_E2が出力される。このため、Ｒ-Ｓフリップフロップ(94)はリセット状態を保持するから、反転出力端子から高い電圧(Ｈ)レベルの反転出力信号Ｖ_Qが出力され、ＯＲゲート(95)に入力される。これにより、図３(Ｂ)に示すように、ＯＲゲート(95)から調光制御回路(7)のＡＮＤゲート(71)に正電圧レベル一定の論理和信号Ｖ_Cが付与されるので、調光信号発生回路(4)からの調光信号Ｖ_Bは無効となり、調光制御回路(7)は冷陰極管(3)の調光動作を行わない。したがって、管電流制御回路(6)から調光制御回路(7)のＡＮＤゲート(71)に連続的に入力される電流制御信号Ｖ_Aが論理積信号Ｖ_Dとして調光制御回路(7)から出力され、駆動回路(8)から交流変換回路(2)内の矩形波電圧発生回路(21)に駆動信号Ｖ_Gが連続的に付与される。これにより、交流変換回路(2)内の矩形波電圧発生回路(21)が連続的に駆動され、直列共振回路(24)を介して図３(Ｃ)に示すように冷陰極管(3)に高圧の正弦波交流電圧Ｖ_Lが連続的に供給される。
【００１５】
時刻ｔ₂において、図３(Ｄ)に示すように管電流Ｉ_Lが流れ始めて冷陰極管(3)が点灯を開始し、管電流検出回路(5)の検出電圧Ｖ_Fが調光切替回路(9)内の基準電源(91)の基準電圧Ｖ_R2以上になると、コンパレータ(92)から高い電圧(Ｈ)レベルの出力信号Ｖ_E2が出力され、Ｒ-Ｓフリップフロップ(94)のセット端子(S)に入力されてＲ-Ｓフリップフロップ(94)がセット状態となる。このとき、Ｒ-Ｓフリップフロップ(94)の反転出力端子から低い電圧(Ｌ)レベルの反転出力信号Ｖ_Qが出力されるので、図３(Ｂ)に示すように時刻ｔ₂以降はＯＲゲート(95)から図３(Ａ)に示す調光信号発生回路(4)の調光信号Ｖ_Bが論理和信号Ｖ_Cとして出力され、調光制御回路(7)のＡＮＤゲート(71)に付与される。このため、調光信号発生回路(4)の調光信号Ｖ_Bの周期で断続する管電流制御回路(6)の電流制御信号Ｖ_Aが調光制御回路(7)のＡＮＤゲート(71)から論理積信号Ｖ_Dとして出力され、駆動回路(8)から交流変換回路(2)内の矩形波電圧発生回路(21)に駆動信号Ｖ_Gが断続的に付与される。これにより、交流変換回路(2)内の矩形波電圧発生回路(21)が調光信号Ｖ_Bの周期で断続的に駆動され、直列共振回路(24)を介して図３(Ｃ)に示すように冷陰極管(3)に高圧の正弦波交流電圧Ｖ_Lが調光信号Ｖ_Bの周期で断続的に供給される。したがって、冷陰極管(3)の点灯開始時ｔ₂以降は、図３(Ｄ)に示すように冷陰極管(3)に管電流Ｉ_Lが断続的に流れ続け、冷陰極管(3)が調光信号Ｖ_Bの周期で点滅を繰り返す冷陰極管(3)の調光動作が行われる。これと共に、管電流制御回路(6)により冷陰極管(3)に流れる管電流Ｉ_Lが略一定に保持されるので、冷陰極管(3)の輝度が常に一定となる。
【００１６】
本実施の形態では、冷陰極管(3)に管電流Ｉ_Lが殆ど流れない暗黒始動期間Ｔ_C中は、調光切替回路(9)により調光信号発生回路(4)から調光制御回路(7)に付与する調光信号Ｖ_Bが無効となるので、調光制御回路(7)による冷陰極管(3)の調光動作が行われない。これにより、交流変換回路(2)の交流電圧Ｖ_Lが連続的に冷陰極管(3)に供給されるので、点灯するために必要十分な励磁エネルギを速やかに冷陰極管(3)に供給できる。また、冷陰極管(3)の点灯開始以降は、調光信号発生回路(4)からの調光信号Ｖ_Bが調光制御回路(7)に付与され、調光制御回路(7)による冷陰極管(3)の調光動作が行われるので、冷陰極管(3)を任意の輝度で点灯することができる。したがって、短時間で冷陰極管(3)を任意の輝度で点灯することができる。実際に、調光信号発生回路(4)から出力される調光信号Ｖ_Bのオン・デューティを５０[％]に設定した場合、装置起動時ｔ₁から冷陰極管(3)の点灯開始時ｔ₂までの時間Ｔ_Cを図５及び図６に示す従来の放電灯点灯装置の場合の同時間Ｔ_Bの約半分に短縮することができた。
【００１７】
本発明の実施態様は前記の実施の形態に限定されず、種々の変更が可能である。例えば、上記の実施の形態では矩形波電圧発生回路(21)及びリーケージトランス(22)と共振コンデンサ(23)とから成る直列共振回路(24)で交流変換回路(2)を構成したが、リーケージトランス(22)の代わりに単巻線のコイルを使用し、矩形波電圧発生回路(21)内の出力トランスの巻数比を１００程度に設定して交流変換回路(2)を構成してもよい。また、矩形波電圧発生回路(21)の代わりにチョッパ回路を設け、チョッパ回路の出力側に自励式のトランジスタインバータ回路を接続して交流変換回路(2)を構成してもよい。また、上記の実施の形態では管電流検出用抵抗(51)と整流ダイオード(52)と平滑コンデンサ(53)とで管電流検出回路(5)を構成したが、オペアンプ等を含む管電流検出回路（電流−電圧変換回路）を使用してもよい。また、上記の実施の形態では管電流検出回路(5)の検出電圧Ｖ_Fのレベルに応じてオン・デューティが変化する矩形パルス列の電流制御信号Ｖ_Aを出力するパルス幅変調（ＰＷＭ）方式の管電流制御回路(6)を使用したが、管電流検出回路(5)の検出電圧Ｖ_Fのレベルに応じて周波数が変化する矩形パルス列の電流制御信号Ｖ_Aを出力するパルス周波数変調（ＰＦＭ）方式の管電流制御回路(6)を使用してもよい。図４は、誤差増幅器(62)から出力される誤差電圧Ｖ_E1のレベルに応じて矩形パルス列のオフ期間が変化するオン幅固定の電流制御信号Ｖ_Aを発生する電圧−周波数変換回路（図中ではＶ／Ｆコンバータと表示）(65)を有するパルス周波数変調方式の管電流制御回路(6)を使用した変更実施の形態を示す。また、上記の実施の形態では調光切替回路(9)内の切替手段をＯＲゲート(95)で構成したが、トランジスタ等のスイッチング素子及び抵抗等を用いて切替手段を構成し、Ｒ-Ｓフリップフロップ(94)がリセット状態のときにスイッチング素子をオフ状態にして調光信号発生回路(4)からの調光信号Ｖ_Bを遮断すると共に正電圧レベル一定の信号を調光制御回路(7)に付与し、Ｒ-Ｓフリップフロップ(94)がセット状態となったときにスイッチング素子をオン状態にして調光信号発生回路(4)からの調光信号Ｖ_Bを調光制御回路(7)に付与してもよい。また、調光切替回路(9)内のワンショットパルス発生器(93)の代わりに抵抗及びコンデンサから成る微分回路と反転器とを使用し、電源投入時に微分回路から反転器を介して出力される微分パルス信号をＲ-Ｓフリップフロップ(94)のリセット端子(R)に付与する構成としてもよい。
【００１８】
【発明の効果】
本発明によれば、放電灯の点灯開始前は、調光切替回路により調光信号発生回路から調光制御回路に付与する調光信号が無効となり、交流変換回路の交流出力が連続的に放電灯に供給されるので、点灯するために必要十分な励磁エネルギを速やかに放電灯に供給でき、短時間で放電灯を任意の輝度で点灯することができる。特に、放電灯の設定輝度が小さく、オン・デューティの狭い調光信号を調光制御回路に付与する場合や、放電灯を長期間点灯させずに冷暗所に放置した場合は、本発明の効果が顕著に現れる。
【図面の簡単な説明】
【図１】 本発明による放電灯点灯装置の一実施の形態を示す回路ブロック図
【図２】 図１の各回路ブロックの内部構成を示す電気回路図
【図３】 図１の回路の各部の電圧及び電流を示す波形図
【図４】 図２の変更実施の形態を示す電気回路図
【図５】 従来の放電灯点灯装置を示す回路ブロック図
【図６】 図５の各回路ブロックの内部構成を示す電気回路図
【図７】 調光動作を行わない場合の図５の回路の各部の電圧及び電流を示す波形図
【図８】 調光動作を行う場合の図５の回路の各部の電圧及び電流を示す波形図
【符号の説明】
(1)・・直流電源、 (2)・・交流変換回路、 (21)・・矩形波電圧発生回路、 (22)・・リーケージトランス、 (22a)・・１次巻線、 (22b)・・２次巻線、 (22c)・・漏洩インダクタンス、 (23)・・共振コンデンサ、 (24)・・直列共振回路、 (3)・・冷陰極管（放電管）、 (4)・・調光信号発生回路、 (5)・・管電流検出回路、 (51)・・管電流検出用抵抗、 (52)・・整流ダイオード、 (53)・・平滑コンデンサ、 (6)・・管電流制御回路、 (61)・・基準電源、 (62)・・誤差増幅器、 (63)・・三角波発振回路、 (64)・・ＰＷＭコンパレータ、 (65)・・電圧−周波数変換回路、 (7)・・調光制御回路、 (71)・・ＡＮＤゲート（ゲート手段）、 (8)・・駆動回路、 (9)・・調光切替回路、 (91)・・基準電源、 (92)・・コンパレータ（比較手段）、 (93)・・ワンショットパルス発生器（起動信号発生手段）、 (94)・・Ｒ-Ｓフリップフロップ（状態保持手段）、 (95)・・ＯＲゲート（切替手段）、[0001]
BACKGROUND OF THE INVENTION
The present invention has a discharge lamp lighting device such as a cold cathode fluorescent lamp (CCFL), and more particularly has a dimming control circuit for adjusting the luminance of the discharge lamp, and lights the discharge lamp at an arbitrary luminance in a short time. It belongs to a discharge lamp lighting device.
[0002]
[Prior art]
A discharge lamp lighting device such as a cold cathode tube used for a backlight or the like of a liquid crystal display device mounted on a liquid crystal television or a notebook personal computer is known. For example, a conventional discharge lamp lighting device shown in FIG. 5, ten and several volts of DC voltage DC power supply for generating the V _IN (1), several hundred volts to a thousand and several DC voltage V _IN of the DC power supply (1) one hundred The AC converter circuit (2) for converting to the AC voltage V _{L of} volts, the cold cathode tube (3) as a discharge tube connected to the output terminal of the AC converter circuit (2), and the adjustment of the cold cathode tube (3) Dimming signal generation circuit (4) for outputting the optical signal V _B , tube current detection circuit (5) for detecting the tube current _IL flowing in the cold cathode tube (3), and detection of the tube current detection circuit (5) _A tube current control circuit (6) for outputting a current control signal V _A for controlling the AC voltage _VL of the AC conversion circuit (2) so that the current value becomes a preset current value, and a dimming signal generation circuit ( _A dimming control circuit (7) having a gate means for continuously or intermittently outputting the current control signal V _A of the tube current control circuit (6) by the dimming signal V _B of 4), and a dimming control circuit (7 ) Output signal V _D or And a drive circuit (8) for forming a drive signal V _G that drives et AC converter (2).
[0003]
As shown in FIG. 6, the AC conversion circuit (2) includes a rectangular wave voltage generation circuit (21) connected to the DC power source (1), a rectangular wave voltage generation circuit (21), and a primary winding. A leakage transformer (22) including a leakage inductance (22c) formed in series with (22a), and a resonant capacitor (23) connected to the secondary winding (22b) of the leakage transformer (22). The leakage transformer (22) and the resonant capacitor (23) constitute a series resonant circuit (24). Here, assuming that the number of turns of the primary winding (22a) and the secondary winding (22b) of the leakage transformer (22) is N ₁ and N ₂ [turn], respectively, the turns ratio of the leakage transformer (22) N ₂ / N ₁ is set to be about 100. Although the detailed illustration is omitted, the rectangular wave voltage generation circuit (21) is configured by, for example, connecting a plurality of switching elements by bridge connection, and generates the DC voltage V _IN from the DC power source (1) by the switching operation of each switching element. A switching circuit for converting to a rectangular wave AC voltage and an output transformer having a switching circuit connected to the primary side winding and generating a rectangular wave AC voltage V _S adjusted in voltage from the secondary side winding. The drive signal V _G which is input from the drive circuit (8) input, by on-off operation at a frequency of about several tens [kHz] to the switching elements constituting the switching circuit, the DC power supply (1) The converted DC voltage V _IN is converted into a rectangular wave AC voltage V _S. The rectangular wave AC voltage V _S output from the rectangular wave voltage generation circuit (21) is high voltage (several hundred volts to thousands) by a series resonance circuit (24) composed of a leakage transformer (22) and a resonance capacitor (23). Is converted to a sinusoidal AC voltage _VL having a frequency of about several tens [kHz] and supplied to the cold cathode tube (3). The dimming signal generator circuit (4) is a rectangular pulse signal with a constant frequency (several tens [Hz] to several [kHz]) that is sufficiently lower than the switching frequency (several tens [kHz]) of the AC converter circuit (2). And the dimming signal V _B of the cold cathode tube (3) is output by changing the on-duty of the rectangular pulse signal according to the desired luminance of the cold cathode tube (3). Therefore, when the luminance of the cold cathode fluorescent lamp (3) is maximum, a rectangular pulse signal with an on-duty of 100 [%], that is, a dimming signal V _B with a constant positive voltage level is output as shown in FIG. .
[0004]
The tube current detection circuit (5) includes a tube current detection resistor (51) connected in series with the cold cathode tube (3), and an anode terminal connected to the cold cathode tube (3) and the tube current detection resistor (51). And a smoothing capacitor (53) connected between the cathode terminal and the ground terminal of the rectifier diode (52). That is, the tube current detection circuit (5) converts the tube current I _L flowing through the cold cathode tube (3) into the corresponding voltage by the tube current detection resistor (51), and the tube current detection resistor (51) by rectifying and smoothing the voltage between the terminals the rectifier diode (52) and a smoothing capacitor (53) and outputs the DC voltage as a detection voltage V _F. Tube current control circuit (6), a cold cathode tube as a reference power source (61) for generating a reference voltage V _R1 for defining the set value of the tube current I _L flowing through (3), the detection of the tube current detecting circuit (5) An error amplifier (62) that outputs an output voltage V _E1 obtained by amplifying an error voltage between the voltage V _F and the reference voltage V _R1 of the reference power source (61), and a triangular wave voltage V _T having a constant frequency (several tens [kHz]) Current control of a rectangular pulse train in which the on-duty changes by comparing the output voltage V _E1 of the error amplifier (62) with the triangular wave voltage V _T of the triangular wave oscillation circuit (63) And a PWM (pulse width modulation) comparator (64) for generating the signal V _A. The gate means of the dimming control circuit (7) outputs, for example, a logical product signal V _D of the dimming signal V _B of the dimming signal generation circuit (4) and the current control signal V _A of the tube current control circuit (6). The AND gate (71) can be configured. That is, the dimming control circuit (7), FIG. 7 (A) to dimming signal generating circuit as shown in (4) when a positive voltage level constant dimming signal V _B is input, the tube current control circuit Since the current control signal V _A from (6) is continuously output, the luminance of the cold cathode tube (3), that is, the dimming operation is not performed. On the other hand, as shown in FIG. 8 (A), a frequency (several tens [Hz] to a frequency sufficiently lower than the frequency (about several tens [kHz]) of the current control signal V _A output from the tube current control circuit (6). A dimming signal V _B of a rectangular pulse train having a duty ratio corresponding to a desired luminance of the cold cathode tube (3) from the dimming signal generation circuit (4) to the dimming control circuit (7). When input, the current control signal V _A from the tube current control circuit (6) is intermittently output at the cycle of the dimming signal V _B to perform the dimming operation of the cold cathode tube (3). The drive circuit (8) continuously or continuously converts the rectangular wave voltage generation circuit (21) in the AC conversion circuit (2) from the logical product signal V _D input from the AND gate (71) of the dimming control circuit (7). A drive signal V _G that is intermittently driven is formed and output to the rectangular wave voltage generation circuit (21).
[0005]
In the configuration shown in FIG. 5, when the dimming signal V _B of the device startup t ₁ dimming signal generating circuit as shown in FIG. 7 (A) (4) of the positive voltage level constant, the dimming control circuit ( 7) does not perform dimming operation, and drives the AC conversion circuit (2) continuously from the drive circuit (8) by the current control signal V _A continuously output from the tube current control circuit (6). A signal V _G is output. As a result, the AC voltage V _L is continuously applied from the AC conversion circuit (2) to the cold cathode tube (3) as shown in FIG. 7 (B), and at time t _{2 as} shown in FIG. 7 (C). When the tube current I _L starts to flow through the cold cathode tube (3), the cold cathode tube (3) starts to light. The time t ₂ later, the tube current I _L flowing through the cold cathode tube (3) by the tube current control circuit (6) is held substantially constant at all times the maximum value constant brightness of the cold cathode tube (3) .
[0006]
Further, as shown in FIG. 8 (A), a duty ratio corresponding to a desired brightness of the cold cathode tube (3) at a frequency sufficiently lower than the frequency of the current control signal V _A of the tube current control circuit (6). When the dimming signal V _B of the rectangular pulse train having the output is output from the dimming signal generation circuit (4), the current control signal V _A of the tube current control circuit (6) is intermittently transmitted from the dimming control circuit (7). The output signal V _D is output. Thus, the dimming signal drive signal V _G intermittently drive the cycle at AC converter (2) of the V _B are outputted from the drive circuit (8), the AC conversion circuit as shown in FIG. 8 (B) ( The AC voltage V _L is intermittently applied from 2) to the cold cathode tube (3). As shown in FIG. 8 (C), a cold cathode tube at time t ₂ (3) to the tube current I when _L starts flowing cold cathode tube (3) starts lighting, the time t ₂ after the cold cathode tube In (3), the tube current I _L continues to flow intermittently. Thus, the repeated blinking period of the cold cathode tube (3) the dimming signal V _B, the desired brightness can be obtained by appropriately adjusting the on-duty of the dimming signal V _B. At the same time, since the tube current I _L flowing through the cold cathode tube (3) by the tube current control circuit (6) is held substantially constant, the luminance of the cold cathode tube (3) is always constant. A discharge lamp lighting device having a configuration similar to the configuration of the discharge lamp lighting device described above is disclosed, for example, in Patent Document 1 below.
[0007]
[Patent Document 1]
JP 2000-357599 A (6th page, FIG. 6)
[0008]
[Problems to be solved by the invention]
In the conventional discharge lamp lighting device shown in FIG. 5, when the dimming signal V _B is inputted in advance from the dimming signal generating circuit (4) to the dimming control circuit (7) as shown in FIG. 8 (A). , the AC voltage V _L of the AC converter (2) as shown in FIG. 8 (B) even in the period T _B in which the tube current I _L is not detected in the cold cathode tube (3), as shown in FIG. 8 (C) It is intermittently applied to the cold cathode tube (3). Therefore, can be supplied from the AC converter necessary and sufficient excitation energy to lighting the cold-cathode tube (3) in-dark starting time T _B the tube current I _L is not detected (2) in cold cathode tubes (3) not, applied from device startup t ₁ CCFL (3) continuously CCFL AC voltage V _L of the time T _B is AC converter lighting up at the start t ₂ of (2) to (3) If there is compared to a longer and disadvantages at the same time T _a (FIG. 7 (B)). Therefore, problems such as a starting failure have occurred when the cold cathode tube (3) is left in a cool and dark place without being lit for a long time.
[0009]
Therefore, an object of the present invention is to provide a discharge lamp lighting device capable of lighting a discharge lamp with an arbitrary luminance in a short time.
[0010]
[Means for Solving the Problems]
A discharge lamp lighting device according to the present invention has a DC power source (1) and a switching circuit including at least one switching element, and DC power supplied from the DC power source (1) by switching operation of the switching circuit is changed to AC power. The AC converter circuit (2) for conversion, the discharge tube (3) connected to the output terminal of the AC converter circuit (2), and the dimming signal (V _B ) output from the dimming signal generation circuit (4) A dimming control circuit (7) for adjusting the brightness of the discharge tube (3) by intermittently generating the AC output (V _L ) of the AC conversion circuit (2), and the tube current flowing through the discharge tube (3) A tube current detection circuit (5) for detecting (I _L ) and a dimming switching circuit (9) connected to the tube current detection circuit (5) are provided. The dimming switching circuit (9) generates an output signal (V _E2 ) of the first voltage (L) level when the detected current value of the tube current detection circuit (5) is lower than the reference value, and the tube current detection circuit Comparing means (92) that generates the output signal (V _E2 ) of the second voltage (H) level when the detected current value of (5) exceeds the reference value, and the start signal (V _P ) when the power is turned on When the start signal generating means (93) for generating the start signal and the start signal generating means (93) generate the start signal (V _P ), the first state is entered, and the output signal (V _E2 ) of the comparison means (92) is During the first voltage (L) level period (T _C ), the first state is maintained, and when the output signal (V _E2 ) of the comparing means (92) becomes the second voltage (H) level. When the state holding means (94) which becomes the state 2 and the state holding means (94) are in the first state, the dimming signal (V _B ) applied to the dimming control circuit (7) is invalidated and AC conversion is performed. continuously generating AC output of the circuit (2) to (V _L), the state holding means (94) is first And a switching means (95) for imparting status and dimming control circuit when it is (7) to the dimming signal (V _B). The dimming signal given from the dimming signal generation circuit (4) to the dimming control circuit (7) by the dimming switching circuit (9) at the start-up when almost no tube current (I _L ) flows through the discharge tube (3) Since (V _B ) becomes invalid, the AC output (V _L ) of the AC conversion circuit (2) is continuously supplied to the discharge tube (3). Thereby, necessary and sufficient excitation energy at the time of start-up is promptly supplied to the discharge tube (3), and the discharge tube (3) can be lit with an arbitrary luminance in a short time.
[0011]
In the embodiment of the present invention, a current control signal (V _L ) for controlling the AC output (V _L ) of the AC conversion circuit (2) so that the detection current value of the tube current detection circuit (5) becomes a preset current value. _A tube current control circuit (6) for outputting V _A ) is provided. For this reason, after the discharge tube (3) starts to light, the tube current control circuit (6) keeps the tube current (I _L ) flowing in the discharge tube (3) substantially constant, so that the brightness of the discharge tube (3) Is always constant. The dimming signal generation circuit (4) is a dimming signal (V _B ) having a duty ratio that is sufficiently lower than the switching frequency of the AC conversion circuit (2) and corresponding to the desired luminance of the discharge tube (3). Is output. The dimming control circuit (7) outputs the current control signal (V _A ) of the tube current control circuit (6) continuously or intermittently by the output signal (V _C ) of the dimming switching circuit (9). It has a gate means (71). The tube current control circuit (6) outputs a current control signal (V _A ) whose on-duty changes according to the voltage level of the detection signal (V _F ) of the tube current detection circuit (5). Alternatively, a tube current control circuit (6) that outputs a current control signal (V _A ) whose frequency changes according to the voltage level of the detection signal (V _F ) of the tube current detection circuit (5) may be used.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a discharge lamp lighting device according to the present invention will be described with reference to FIGS. However, in these drawings, substantially the same parts as those shown in FIGS. 5 to 8 are denoted by the same reference numerals, and description thereof is omitted.
The discharge lamp lighting device of the present embodiment, as shown in FIG. 1, the period T _C (FIG. 3) of the tube current detecting circuit (5) does not detect the tube current I _L of the cold cathode tube (3) is dimming The dimming signal V _{B applied} from the signal generation circuit (4) to the dimming control circuit (7) is invalidated to continuously generate the AC voltage V _L from the AC conversion circuit (2), and the tube current detection circuit (5 Figure 5) is in that connected cold cathode tube (3) tube current I _L of the detected dimming switching circuit for driving a light control circuit (7) at (9) to the tube current detecting circuit (5) Different from the conventional discharge lamp lighting device shown in FIG.
[0013]
As shown in FIG. 2, the dimming switching circuit (9) includes a reference power supply (91) that generates a reference voltage V _R2 that defines a minimum detection value of the tube current I _L flowing through the cold cathode tube (3), a tube When the detection voltage V _{F of the} current detection circuit (5) is lower than the reference voltage V _R2 of the reference power supply (91), a low voltage (L) level output signal V _E2 is generated to detect the tube current detection circuit (5). When the voltage V _F becomes equal to or higher than the reference voltage V _R2 of the reference power source 91, the comparator 92 as a comparison means for generating the output signal V _E2 having a high voltage (H) level and a power switch (not shown) are turned on. The one-shot pulse generator (93) as a starting signal generating means for generating a single-pulse starting signal V _P when it is activated, and the starting signal V _P is input from the one-shot pulse generator (93) to the reset terminal (R) to become a reset state when the output signal V _E2 is low voltage (L) level period of the comparator (92) Lise Holding the door state, R-S flip-flop as a state holding means the set state when the output signal V _E2 of the high voltage (H) level comparator (92) from the set terminal (S) is input (94 a), OR gate (95 as switching means for outputting a logical sum signal V _C of the dimming signal V _B of the inverted output signal V _Q and the dimming signal generating circuit (4) of the R-S flip-flop (94) ). The reference voltage V _R2 of the reference power source (91) of the dimming / switching circuit (9) is set to a value lower than the reference voltage V _R1 of the reference power source (61) of the tube current control circuit (6). The AND gate (71) of the dimming control circuit (7) includes a logical sum signal V _C output from the dimming switching circuit (9) and a current control signal V _A output from the tube current control circuit (6). And a logical product signal V _D is output. Other configurations are substantially the same as those of the conventional discharge lamp lighting device shown in FIG.
[0014]
In the above configuration, when a power switch (not shown) is turned on at time t ₁ (FIG. 3) and the power is turned on, the one-shot pulse generator (93) in the dimming switching circuit (9) starts a single pulse start signal. _VP is output and input to the reset terminal (R) of the RS flip-flop (94), and the RS flip-flop (94) is reset. At the same time, as shown in FIG. 3A, a frequency (tens of Hz) that is sufficiently lower than the frequency (tens to hundreds of kHz) of the current control signal _VA of the tube current control circuit (6). Dimming signal V _B of a rectangular pulse train having a duty ratio corresponding to the desired luminance of the cold cathode fluorescent lamp (3) is output from the dimming signal generation circuit (4), and the dimming switching circuit (9) To the OR gate (95). As shown in FIG. 3 (D), the tube current I _L hardly flows through the cold cathode tube (3) during the dark start period T _C from the power-on t ₁ to the lighting start time t ₂ , and the tube current detection circuit. Since the detection voltage V _F of (5) is lower than the reference voltage V _R2 of the reference power supply (91) in the dimming switching circuit (9), the low voltage (L) level output signal V _E2 is output from the comparator (92). Is output. Therefore, since the R-S flip-flop (94) holds the reset state, the inverted output signal V _Q of the high voltage (H) level from the inverted output terminal is output and input to the OR gate (95). As a result, as shown in FIG. 3B, a logical sum signal V _C with a constant positive voltage level is applied from the OR gate (95) to the AND gate (71) of the dimming control circuit (7). The dimming signal V _B from the optical signal generating circuit (4) becomes invalid, and the dimming control circuit (7) does not perform the dimming operation of the cold cathode tube (3). Therefore, the current control signal V _A continuously input from the tube current control circuit (6) to the AND gate (71) of the dimming control circuit (7) is output from the dimming control circuit (7) as the logical product signal V _D. is output, the drive signal V _G is continuously applied to the rectangular wave voltage generation circuit of the AC converter (2) in the driving circuit (8) (21). As a result, the rectangular wave voltage generation circuit (21) in the AC conversion circuit (2) is continuously driven, and the cold cathode tube (3) is connected via the series resonance circuit (24) as shown in FIG. Is continuously supplied with a high voltage sine wave AC voltage V _L.
[0015]
In time t _2, the Figure 3 tube current I _L as shown in (D) is started to flow cold cathode tube (3) starts lighting, the detection voltage V _F dimming switching circuit of the tube current detecting circuit (5) When the reference voltage V _R2 of the reference power source (91) in (9) becomes higher than the output voltage V _{E2 of the} high voltage (H) level from the comparator (92), the set terminal of the RS flip-flop (94) The signal is input to (S), and the RS flip-flop (94) is set. In this case, since R-S inverted output signal V _Q of the inverted lower the output terminal voltage (L) level of the flip-flop (94) is outputted, the time t ₂ after as shown in FIG. 3 (B) OR gate The dimming signal V _B of the dimming signal generation circuit (4) shown in FIG. 3 (A) is output as an OR signal V _C from (95) to the AND gate (71) of the dimming control circuit (7). Is done. For this reason, the current control signal V _{A of} the tube current control circuit (6) that is intermittent in the cycle of the dimming signal V _B of the dimming signal generation circuit (4) is sent from the AND gate (71) of the dimming control circuit (7). It is output as a logical product signal V _D , and the drive signal V _G is intermittently applied from the drive circuit (8) to the rectangular wave voltage generation circuit (21) in the AC conversion circuit (2). Thereby, the driven intermittently with a period of the AC conversion circuit (2) of the rectangular wave voltage generating circuit (21) the dimming signal V _B, shown in FIG. 3 (C) via the series resonant circuit (24) As described above, the high voltage sinusoidal AC voltage V _L is intermittently supplied to the cold cathode tube 3 in the cycle of the dimming signal V _B. Therefore, the lighting start time t ₂ after the cold cathode tube (3), the tube current I _L continues to flow intermittently to the cold cathode tube (3) As shown in FIG. 3 (D), a cold cathode tube (3) dimming operation of the cold cathode tube (3) is carried out but repeating the flashing cycle of the dimming signal V _B. At the same time, since the tube current I _L flowing through the cold cathode tube (3) by the tube current control circuit (6) is held substantially constant, the luminance of the cold cathode tube (3) is always constant.
[0016]
In the present embodiment, during the dark start period T _C in which the tube current I _L hardly flows through the cold cathode tube (3), the dimming signal generation circuit (4) to the dimming control circuit are controlled by the dimming switching circuit (9). Since the dimming signal V _{B applied} to (7) becomes invalid, the dimming operation of the cold cathode tube (3) by the dimming control circuit (7) is not performed. As a result, the AC voltage _VL of the AC conversion circuit (2) is continuously supplied to the cold cathode tube (3), so that the excitation energy necessary and sufficient for lighting is quickly supplied to the cold cathode tube (3). it can. In addition, after the cold cathode tube (3) is turned on, the dimming signal V _B from the dimming signal generation circuit (4) is applied to the dimming control circuit (7), and the dimming control circuit (7) performs cooling. Since the light control operation of the cathode tube (3) is performed, the cold cathode tube (3) can be lit with an arbitrary luminance. Therefore, the cold cathode fluorescent lamp (3) can be lit with an arbitrary luminance in a short time. Indeed, the dimming signal generating circuit (4) if you set the on duty of the dimming signal V _B output to 50% from the lighting start of the cold cathode tube from the device startup t ₁ (3) could be reduced to the same about half the time T _B in the case of the conventional discharge lamp lighting device shown in FIGS. 5 and 6 the time T _C until t _2.
[0017]
Embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made. For example, in the above embodiment, the AC converter circuit (2) is configured by the series wave resonance circuit (24) including the rectangular wave voltage generation circuit (21) and the leakage transformer (22) and the resonance capacitor (23). The AC converter circuit (2) may be configured by using a single-winding coil instead of the transformer (22) and setting the turn ratio of the output transformer in the rectangular wave voltage generating circuit (21) to about 100. . Further, the AC converter circuit (2) may be configured by providing a chopper circuit instead of the rectangular wave voltage generation circuit (21) and connecting a self-excited transistor inverter circuit to the output side of the chopper circuit. In the above embodiment, the tube current detection resistor (51), the rectifier diode (52), and the smoothing capacitor (53) constitute the tube current detection circuit (5). (Current-voltage conversion circuit) may be used. Further, in the above embodiment the lamp current detecting circuit detects a voltage pulse width modulation for outputting a current control signal V _A of the rectangular pulse train is on duty changes according to the level of V _F (PWM) method of (5) Although the tube current control circuit (6) is used, pulse frequency modulation (PFM) that outputs a current control signal V _A of a rectangular pulse train whose frequency changes according to the level of the detection voltage V _F of the tube current detection circuit (5) A tube current control circuit (6) of the type may be used. FIG. 4 shows a voltage-frequency conversion circuit for generating a current control signal V _A with a fixed on-width in which the off-period of the rectangular pulse train changes according to the level of the error voltage V _E1 output from the error amplifier (62). Then, a modified embodiment using a pulse current modulation type tube current control circuit (6) having a V / F converter (display) (65) is shown. In the above embodiment, the switching means in the dimming switching circuit (9) is configured by the OR gate (95). However, the switching means is configured using a switching element such as a transistor and a resistor, and RS flip-flop (94) is a positive voltage level constant signal the dimming control circuit as well as blocking the dimming signal V _B from when the switching element in the off state the dimming signal generating circuit (4) when the reset state (7 ) And when the RS flip-flop (94) is in the set state, the switching element is turned on and the dimming signal V _B from the dimming signal generation circuit (4) is supplied to the dimming control circuit (7). ). Also, instead of the one-shot pulse generator (93) in the dimming switching circuit (9), a differentiating circuit consisting of a resistor and a capacitor and an inverter are used, and output from the differentiating circuit via the inverter when the power is turned on. The differential pulse signal may be applied to the reset terminal (R) of the RS flip-flop (94).
[0018]
【The invention's effect】
According to the present invention, the dimming signal applied from the dimming signal generating circuit to the dimming control circuit is invalidated by the dimming switching circuit before starting the lighting of the discharge lamp, and the AC output of the AC conversion circuit is continuously released. Since it is supplied to the electric lamp, the excitation energy necessary and sufficient for lighting can be quickly supplied to the discharge lamp, and the discharge lamp can be lit with an arbitrary luminance in a short time. The effect of the present invention is particularly effective when a dimming signal having a low set luminance and a low on-duty is applied to the dimming control circuit, or when the discharge lamp is left in a cool dark place without being lit for a long time. Appears prominently.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing an embodiment of a discharge lamp lighting device according to the present invention. FIG. 2 is an electric circuit diagram showing an internal configuration of each circuit block in FIG. 1. FIG. Waveform diagram showing voltage and current [FIG. 4] Electric circuit diagram showing a modified embodiment of FIG. 2 [FIG. 5] Circuit block diagram showing a conventional discharge lamp lighting device [FIG. 6] Inside each circuit block of FIG. FIG. 7 is a waveform diagram showing the voltage and current of each part of the circuit of FIG. 5 when the dimming operation is not performed. FIG. 8 is a waveform diagram of the parts of the circuit of FIG. 5 when the dimming operation is performed. Waveform diagram showing voltage and current 【Explanation of symbols】
(1) ・ ・ DC power supply, (2) ・ AC conversion circuit, (21) ・ ・ Square wave voltage generator, (22) ・ Leakage transformer, (22a) ・ ・ Primary winding, (22b) ・· Secondary winding, (22c) · · Leakage inductance, (23) · · Resonance capacitor, (24) · · Series resonance circuit, (3) · · Cold cathode tube (discharge tube), (4) · · adjustment Optical signal generation circuit, (5) ... Tube current detection circuit, (51) ... Tube current detection resistor, (52) ... Rectifier diode, (53) ... Smoothing capacitor, (6) ... Tube current control Circuit, (61) ・ ・ Reference power supply, (62) ・ ・ Error amplifier, (63) ・ ・ Triangle wave oscillation circuit, (64) ・ ・ PWM comparator, (65) ・ ・ Voltage-frequency conversion circuit, (7) ・・ Dimming control circuit, (71) ・ ・ AND gate (gate means), (8) ・ ・ Drive circuit, (9) ・ ・ Dimming switching circuit, (91) ・ ・ Reference power supply, (92) ・ ・ Comparator (Comparison means), (93) .. One-shot pulse generator (startup) (Signal generating means), (94) .. R-S flip-flop (state holding means), (95) .. OR gate (switching means),

Claims (6)

直流電源と、少なくとも１つのスイッチング素子を含むスイッチング回路を有し且つ該スイッチング回路のスイッチング動作により前記直流電源から供給される直流電力を交流電力に変換する交流変換回路と、該交流変換回路の出力端子に接続された放電管と、調光信号発生回路から出力される調光信号により前記交流変換回路の交流出力を断続的に発生させて前記放電管の輝度を調整する調光制御回路とを備えた放電灯点灯装置において、
前記放電管に流れる管電流を検出する管電流検出回路と、該管電流検出回路に接続された調光切替回路とを備え、
前記調光切替回路は、前記管電流検出回路の検出電流値が基準値より低いときは第１の電圧レベルの出力信号を発生し、前記管電流検出回路の検出電流値が基準値以上となったときに第２の電圧レベルの出力信号を発生する比較手段と、
電源投入時に起動信号を発生する起動信号発生手段と、
該起動信号発生手段が起動信号を発生したときに第１の状態となり、前記比較手段の出力信号が前記第１の電圧レベルの期間は前記第１の状態を保持し、前記比較手段の出力信号が前記第２の電圧レベルとなったときに第２の状態となる状態保持手段と、
該状態保持手段が前記第１の状態のときは前記調光制御回路に付与する前記調光信号を無効にして前記交流変換回路の交流出力を連続的に発生させ、前記状態保持手段が前記第２の状態となったときに前記調光制御回路に前記調光信号を付与する切替手段とを有することを特徴とする放電灯点灯装置。An AC conversion circuit having a DC power supply, a switching circuit including at least one switching element, and converting DC power supplied from the DC power supply into AC power by a switching operation of the switching circuit, and an output of the AC conversion circuit A discharge tube connected to the terminal, and a dimming control circuit for adjusting the luminance of the discharge tube by intermittently generating an AC output of the AC conversion circuit by a dimming signal output from the dimming signal generation circuit In the provided discharge lamp lighting device,
A tube current detection circuit for detecting a tube current flowing in the discharge tube, and a dimming switching circuit connected to the tube current detection circuit,
The dimming switching circuit generates an output signal of a first voltage level when the detection current value of the tube current detection circuit is lower than a reference value, and the detection current value of the tube current detection circuit becomes equal to or higher than the reference value. Comparing means for generating an output signal of a second voltage level when
Start signal generating means for generating a start signal when the power is turned on;
When the activation signal generating means generates the activation signal, the first state is obtained, and the output signal of the comparison means maintains the first state during the period of the first voltage level, and the output signal of the comparison means State holding means that enters a second state when is at the second voltage level;
When the state holding means is in the first state, the dimming signal applied to the dimming control circuit is invalidated to continuously generate an AC output of the AC conversion circuit, and the state holding means A discharge lamp lighting device comprising: switching means for applying the dimming signal to the dimming control circuit when the state becomes 2. 前記管電流検出回路の検出電流値が予め設定された電流値となるように前記交流変換回路の交流出力を制御する電流制御信号を出力する管電流制御回路を備えた請求項１に記載の放電灯点灯装置。  The tube current control circuit according to claim 1, further comprising a tube current control circuit that outputs a current control signal for controlling an AC output of the AC conversion circuit so that a detection current value of the tube current detection circuit becomes a preset current value. Electric light lighting device. 前記調光信号発生回路は、前記交流変換回路のスイッチング周波数よりも十分に低い周波数で且つ前記放電管の所望の輝度に対応するデューティ比を有する前記調光信号を出力する請求項１又は２に記載の放電灯点灯装置。  The dimming signal generation circuit outputs the dimming signal having a duty ratio corresponding to a desired luminance of the discharge tube at a frequency sufficiently lower than a switching frequency of the AC conversion circuit. The discharge lamp lighting device described. 前記調光制御回路は、前記調光切替回路の出力信号により前記管電流制御回路の電流制御信号を連続的又は断続的に出力するゲート手段を有する請求項２又は３に記載の放電灯点灯装置。  4. The discharge lamp lighting device according to claim 2, wherein the dimming control circuit includes gate means for continuously or intermittently outputting a current control signal of the tube current control circuit according to an output signal of the dimming switching circuit. . 前記管電流制御回路は、前記管電流検出回路の検出信号の電圧レベルに応じてオン・デューティが変化する前記電流制御信号を出力する請求項２〜４の何れか１項に記載の放電灯点灯装置。  The discharge lamp lighting according to any one of claims 2 to 4, wherein the tube current control circuit outputs the current control signal whose on-duty changes according to a voltage level of a detection signal of the tube current detection circuit. apparatus. 前記管電流制御回路は、前記管電流検出回路の検出信号の電圧レベルに応じて周波数が変化する前記電流制御信号を出力する請求項２〜４の何れか１項に記載の放電灯点灯装置。  The discharge lamp lighting device according to any one of claims 2 to 4, wherein the tube current control circuit outputs the current control signal whose frequency changes according to a voltage level of a detection signal of the tube current detection circuit.

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