JP2005011714A

JP2005011714A - Discharge lamp lighting device

Info

Publication number: JP2005011714A
Application number: JP2003175366A
Authority: JP
Inventors: Tomohiro Mizoguchi; 智宏溝口
Original assignee: Harison Toshiba Lighting Corp
Current assignee: Toshiba Lighting and Technology Corp
Priority date: 2003-06-19
Filing date: 2003-06-19
Publication date: 2005-01-13

Abstract

<P>PROBLEM TO BE SOLVED: To execute a broad range of light modulation control by lighting only discharge lamps of a number according to a designated light modulation rate within a plurality of discharge lamps and by executing control for restricting their lamp currents, in light modulation control. <P>SOLUTION: This discharge lamp lighting device is equipped with: a plurality of the discharge lamps 1a-1c; power circuits 20a-20c for supplying lamp currents to a plurality of the respective discharge lamps; and a control circuit 21 for inputting a light modulation signal from the outside to execute, to the power circuits, lighting/extinguishing control of a plurality of the respective discharge lamps. The control circuit 21 controls the lamp currents so as to set the lamp currents corresponding to a designated light modulation rate based on a light modulation command, and executes light modulation control to extinguish an appropriate number of the discharge lamps out of a plurality of the discharge lamps when the designated light modulation rate is set lower than a predetermined light modulation rate to enable a broad range of light modulation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、調光機能を備えた放電灯点灯装置に関する。
【０００２】
【従来の技術】
従来、例えば、図９に示すような３本の放電灯１ａ〜１ｃにより液晶ユニット１５を側端面から照明するエッジライト方式の液晶バックライト装置１６に用いられる調光機能を備えた放電灯点灯装置は、図１０に示すように、１００％フル点灯から照明光量を絞り画面を暗くする調光を行うとき、全放電灯１ａ〜１ｃの輝度を調光指令に応じて均一に低下させる制御を行っていた。
【０００３】
【発明が解決しようとする課題】
ところが、このような従来の放電灯点灯装置では、放電灯各々の放電維持可能な電流には下限値（例えば２０％）があるため、調光制御において複数本の放電灯各々に対する輝度を指定調光率に応じて均一に暗くする制御では、図１０に示したように２０％を切る低い調光率での点灯ができない問題点があった。
【０００４】
しかしながら、複数本の放電灯それぞれの放電維持可能な電流の下限値がそれぞれの１００％点灯時の２０％であるとすれば、１灯だけ残して下限値まで電流を絞れば、３灯全灯点灯時の１００％の光量に対して約７％（＝２０％／３００％）まで調光できることになる。
【０００５】
本発明はこのような技術的課題に鑑みてなされたもので、調光制御において、複数本の放電灯のうち指定調光率に応じた本数の放電灯だけ点灯させると共にその電流を制御することにより、幅広い調光制御ができる放電灯点灯装置を提供することを目的とする。
【０００６】
本発明はまた、調光制御において複数本の放電灯のうち指定調光率に応じた本数の放電灯だけを点灯させておき、残りの放電灯は消灯させる制御により、回路構成をシンプルにして使用放電灯数分の１まで段階的に調光ができる放電灯点灯装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
請求項１の発明の放電灯点灯装置は、複数の放電灯と、前記複数の放電灯各々を点灯する電源回路と、外部からの調光指令を入力し、前記電源回路に対して前記複数の放電灯各々の点灯／消灯制御を行う制御回路とを備え、前記制御回路は、前記調光指令に基づき指定調光率が所定の調光率よりも低くなったときに前記複数の放電灯のうちの該当本数の放電灯を消灯させる制御機能を有するものである。
【０００８】
請求項１の発明の放電灯点灯装置では、調光指令に基づき指定調光率が所定の調光率よりも低くなったときに複数の放電灯のうちの該当本数の放電灯だけ点灯させ、残りの放電灯は消灯させることにより、シンプルな制御によって幅広い調光が行える。
【０００９】
請求項２の発明の放電灯点灯装置は、複数の放電灯と、前記複数の放電灯各々を点灯する電源回路と、外部からの調光指令を入力し、前記電源回路に対して前記複数の放電灯各々の点灯、消灯、点灯時の輝度制御を行う制御回路とを備え、前記制御回路は、前記調光指令に基づき指定調光率に対応する輝度になるように制御し、かつ指定調光率が所定の調光率よりも低くなったときに前記複数の放電灯のうちの該当本数の放電灯を消灯させる制御機能を有するものである。
【００１０】
請求項２の発明の放電灯点灯装置では、調光指令に基づき指定調光率に対応する輝度になるように制御し、かつ指定調光率が所定の調光率よりも低くなったときに複数の放電灯のうちの該当本数の放電灯だけ点灯させ、かつそれらの輝度を暗くし、残りの放電灯は消灯させることにより、幅広い調光を可能にする。
【００１１】
【発明の実施の形態】
以下、本発明の実施の形態を図に基づいて詳説する。図１は、本発明の第１の実施の形態の放電灯点灯装置の回路構成を示している。本実施の形態の放電灯点灯装置は、従来同様、図９に示すような例えば３本の放電灯１ａ〜１ｃにより液晶ユニット１５を側端面から照明するエッジライト方式の液晶バックライト装置１６として用いられる調光機能を備えたものである。本実施の形態の放電灯点灯装置は、複数本、ここでは３本の放電灯１ａ，１ｂ，１ｃそれぞれに対してインバータ回路２０ａ〜２０ｃにより高圧高周波電力を供給する構成である。
【００１２】
インバータ回路２０ａ〜２０ｃそれぞれは、ロイヤーインバータ回路であり、対となる２つの発振トランジスタ７，７と、両発振トランジスタ７，７のベースに供給する電流を制御するベース抵抗１０と、ベース用巻線として３次巻線５を設けたインバータトランス２と、コンデンサ６によって構成されている。
【００１３】
各インバータトランス２はセンタータップの設けられた１次巻線４、ランプ電流を供給する２次巻線３、そして上述した３次巻線５から構成されている。
【００１４】
各ベース抵抗１０の一端は直流電源１２に接続し、その他端は駆動用スイッチ９を介して、インバータトランス２の３次巻線５から発振トランジスタ７に戻る接続線に接続してある。インバータトランス２の１次巻線４の中間タップは、直流電源１２にインダクタ８を介して接続してある。
【００１５】
各駆動用スイッチ９をなすトランジスタのベースには調光制御回路２１からの調光制御信号線２２ａ〜２２ｃ各々がベース抵抗１１を介して接続してある。調光指令が入力されない限り、調光制御回路２１は各駆動用スイッチ９を導通させる制御信号を出力している。
【００１６】
このようなインバータ回路２０ａ〜２０ｃそれぞれは、直流電源１２が印加されると、インダクタ８を通してインバータトランス２の１次巻線４に電流が流れ、同時に直流電源１２から出力された電圧がベース抵抗１０、駆動用スイッチ９を通じて発振トランジスタ７，７のベースに印加される。
【００１７】
インバータトランス２の１次巻線４と３次巻線５のリアクタンスと共振コンデンサ７とで共振し、インバータトランス２の３次巻線５の端子間にインバータトランス２の１次巻線４と３次巻線５の巻数比だけ昇圧された高電圧が誘起され、同時に、３次巻線５には１次巻線４に流れる電流の方向と同一方向に電流が流れて自励発振し、共振周波数で発振トランジスタ７，７を交互に導通させる。インバータトランス２は、その１次巻線４と２次巻線３との巻数比だけ１次巻線４に流れる電流の電圧を昇圧し、この結果として、放電灯１ａ〜１ｃ各々に高圧高周波電流を供給して点灯させる。
【００１８】
調光制御回路２１は通常はオペアンプを用いた論理回路で構成されるが、ここでは機能を分かりやすくするためにデジタル回路として示してある。この調光制御回路２１は、外部から入力される調光指令信号Ｓを入力端子２３で受けて、表１に示す比較を行い、その比較結果に応じた点灯本数Ｎと輝度を決定し、これに基づいて生成した調光制御信号を調光制御信号線２２ａ〜２２ｃに出力する。
【００１９】
【表１】

調光制御信号は、負論理では１パルス周期に対するＬ（ローレベル）期間のデューティを調光指令に応じた比率に調整したパルス信号である。なお、正論理の回路であれば、１パルス周期に対するＨ（ハイレベル）期間のデューティを調光指令に応じた比率に調整することになる。
【００２０】
次に、上記構成の第１の実施の形態の放電灯点灯装置の点灯動作について、図２〜図５を用いて説明する。
【００２１】
（１）全点灯時
全点灯時には、調光指令Ｓは１００％指令であり、これに対して制御回路２１は放電灯１ａ〜１ｃ３灯全部に１００％点灯制御信号を出力する。この場合、３灯のインバータ回路２０ａ〜２０ｃそれぞれの駆動スイッチ９にはデューティ１００％の信号が出力され、インバータ回路２０ａ〜２０ｃそれぞれはフルパワーで動作し、各放電灯１ａ〜１ｃを１００％の輝度で点灯させる。
【００２２】
（２）１００％〜６０％調光時
外部から１００％〜６０％の調光指令Ｓ（０Ｖ〜第１の設定電圧までの調光電圧）が制御回路２１に与えられると、制御回路２１は図２のフローチャートのステップＳ１，Ｓ２，Ｓ３の制御により、図３、図４におけるＡ区間の調光動作を行い、３灯点灯で、かつ、各灯の点灯デューティを調光指令Ｓと合わせる。
【００２３】
これにより、放電灯１ａ〜１ｃの全灯が均一に１００〜６０％の輝度で点灯し、装置全体の実質輝度も１００〜６０％に調光される。このときの３灯の点灯状態は、図５（ａ）に示すように３灯点灯である。
【００２４】
（３）６０％〜４５％調光時
外部から６０％〜４５％の調光指令Ｓ（第１の設定電圧〜第２の設定電圧の調光電圧）が制御回路２１に与えられると、制御回路２１は図２のフローチャートのステップＳ１，Ｓ２，Ｓ４，Ｓ５の制御により、図３、図４におけるＢ区間の調光動作を行い、放電灯１ａの１灯は消灯し、残りの放電灯１ｂ，１ｃの２灯を点灯させ、それぞれの点灯デューティを調光指令Ｓと合わせる。
【００２５】
これにより、放電灯１ｂ，１ｃの２灯が均一に６０〜４５％の輝度で点灯し、装置全体の実質輝度は４０〜３０％（＝１２０〜９０％／３００％）に調光される。このときの３灯の点灯状態は、図５（ｂ）に示すものである。
【００２６】
（４）４５％〜２０％調光時
外部から調光指令として４５％〜２０％の調光指令Ｓ（第２の設定電圧〜輝度最小となる設定電圧の調光電圧）が制御回路２１に与えられると、制御回路２１は図２のフローチャートのステップＳ１，Ｓ２，Ｓ４，Ｓ６の制御により、図３、図４におけるＣ区間の調光動作を行い、放電灯１ａ，１ｃの２灯を消灯させ、残りの放電灯１ｂの１灯だけを点灯させ、その点灯デューティを調光指令Ｓと合わせる。
【００２７】
これにより、１灯の放電灯１ｂだけが４５〜２０％の輝度で点灯し、装置全体の実質輝度は１５〜７％（＝４５〜２０％／３００％）に調光される。このときの３灯の点灯状態は、図５（ｃ）に示すものである。
【００２８】
これにより、図３に示したように、従来であれば装置全体での実質輝度がフル点灯時の約２０％になるまでしか調光できなかったが、本実施の形態によれば同じ性能の放電灯を使用しながらも、従来の１／３である約７％までの低い輝度まで実質輝度を調整でき、調光範囲を広げることができる。
【００２９】
さらに一般には、例えば、従来であればＮ本の放電灯（あるいは同時に点灯／消灯される放電灯の組数がＮ組の放電灯）について装置全体での実質輝度がフル点灯時の約２０％になるまでしか調光できなかったものが、本実施の形態の放電灯点灯装置では、同じ性能の放電灯を使用しながらも、従来の約２０％に対してその１／Ｎになる低い輝度まで実質輝度を調整でき、調光範囲を広げることができるのである。
【００３０】
次に、本発明の第２の実施の形態の放電灯点灯装置について、図１、図６〜図８を用いて説明する。第２の実施の形態の特徴は、外部からの調光指令に対して、３灯を段階的に消灯させ、輝度を段階的に調整する、シンプル化された調光機能にある。したがって、第２の実施の形態の放電灯点灯装置の回路構成は、図１に示した第１の実施の形態と共通する。そして、制御回路２１の機能構成がシンプル化され、図７に示すように、調光指令が「明」、「中間」、「暗」の３段階であり、それぞれに応じて３灯全灯点灯、２灯点灯、１灯点灯の制御を行うように構成されている。
【００３１】
この第２の実施の形態の放電灯点灯装置による調光動作について説明する。図７、図８において、調光指令Ｓとして「明」が入力されれば、制御回路２１は放電灯１ａ〜１ｃの３灯全灯をデューティ１００％で点灯させる制御信号を出力する（図６のフローチャートにおけるステップＳ１１，Ｓ１２，Ｓ１３）。
【００３２】
調光指令Ｓが「中間」であれば、制御回路２１は放電灯１ａを消灯させ、残りの放電灯１ｂ，１ｃの２灯について、デューティ１００％で点灯させる制御信号を出力する（ステップＳ１１，Ｓ１２，Ｓ１４，Ｓ１５）。
【００３３】
そして調光指令Ｓが「暗」であれば、制御回路２１は放電灯１ａ，１ｃの２灯を消灯させ、残りの放電灯１ｂの１灯だけをデューティ１００％で点灯させる制御信号を出力する（ステップＳ１１，Ｓ１２，Ｓ１４，Ｓ１６）。
【００３４】
この第２の実施の形態によれば、３灯−２灯−１灯の点灯／消灯の切り替えだけで３段階の調光ができ、回路をシンプル化して多段調光できる。
【００３５】
なお、上記の第１、第２の実施の形態の放電灯点灯装置において、放電灯数は３灯に限定されることはなく、さらに多くの本数を点灯させる放電灯点灯装置についても同様に適用できる。
【００３６】
【発明の効果】
以上のように請求項１の発明によれば、調光指令に基づき指定調光率が所定の調光率よりも低くなったときに複数の放電灯のうちの該当本数の放電灯だけ点灯させ、残りの放電灯は消灯させることにより、シンプルな制御によって幅広い調光が行える。
【００３７】
請求項２の発明によれば、調光指令に基づき指定調光率に対応する輝度になるように制御し、かつ指定調光率が所定の調光率よりも低くなったときに複数の放電灯のうちの該当本数の放電灯だけ点灯させて、それらの輝度を制御し、かつ残りの放電灯は消灯させることにより、幅広い調光を可能にする。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態の放電灯点灯装置の回路ブロック図。
【図２】上記の実施の形態による調光動作のフローチャート。
【図３】上記の実施の形態による調光動作時の調光電圧と実質輝度との関係を示す説明図。
【図４】上記の実施の形態による調光動作の制御波形図。
【図５】上記の実施の形態の放電灯点灯装置の調光動作時の各放電灯の点灯／消灯状態の推移を示す説明図。
【図６】本発明の第２の実施の形態の放電灯点灯装置による調光動作のフローチャート。
【図７】上記の実施の形態による調光動作時の調光電圧と実質輝度との関係を示す説明図。
【図８】上記の実施の形態による調光動作の制御波形図。
【図９】従来例の放電灯点灯装置の側面図。
【図１０】従来例の放電灯点灯装置による調光動作時の調光電圧と実質輝度との関係を示す説明図。
【符号の説明】
１ａ〜１ｃ放電灯
２０ａ〜２０ｃインバータ回路
２１制御回路
２２ａ〜２２ｃ調光制御信号線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp lighting device having a dimming function.
[0002]
[Prior art]
Conventionally, for example, a discharge lamp lighting device having a dimming function used in an edge light type liquid crystal backlight device 16 that illuminates the liquid crystal unit 15 from the side end surface by three discharge lamps 1a to 1c as shown in FIG. As shown in FIG. 10, when performing dimming to reduce the illumination light amount from 100% full lighting and darken the screen, control is performed to uniformly reduce the luminance of all the discharge lamps 1a to 1c according to the dimming command. It was.
[0003]
[Problems to be solved by the invention]
However, in such a conventional discharge lamp lighting device, since there is a lower limit value (for example, 20%) in the current that can maintain the discharge of each discharge lamp, the luminance for each of the plurality of discharge lamps is designated and adjusted in dimming control. In the control for darkening uniformly according to the light rate, there is a problem that it is impossible to light at a low light control rate of less than 20% as shown in FIG.
[0004]
However, if the lower limit value of the current that can maintain the discharge of each of the plurality of discharge lamps is 20% of the lighting at 100% of each, if only one lamp is left and the current is reduced to the lower limit value, all three lamps are turned on. The light can be dimmed to about 7% (= 20% / 300%) with respect to the light amount of 100% at the time of lighting.
[0005]
The present invention has been made in view of such a technical problem. In dimming control, only the number of discharge lamps corresponding to a specified dimming rate among a plurality of discharge lamps is turned on and the current is controlled. Accordingly, an object of the present invention is to provide a discharge lamp lighting device that can perform wide dimming control.
[0006]
The present invention also simplifies the circuit configuration by controlling to turn on only the number of discharge lamps corresponding to the specified dimming rate among the plurality of discharge lamps in the dimming control, and to turn off the remaining discharge lamps. It is an object of the present invention to provide a discharge lamp lighting device capable of dimming in steps up to a fraction of the number of used discharge lamps.
[0007]
[Means for Solving the Problems]
The discharge lamp lighting device of the invention of claim 1 inputs a plurality of discharge lamps, a power supply circuit that lights each of the plurality of discharge lamps, and a dimming command from the outside, and the plurality of discharge lamps to the power supply circuit A control circuit that controls the turning on / off of each of the discharge lamps, and the control circuit controls the plurality of discharge lamps when a designated dimming rate is lower than a predetermined dimming rate based on the dimming command. It has a control function to turn off the corresponding number of discharge lamps.
[0008]
In the discharge lamp lighting device of the invention of claim 1, when the specified dimming rate is lower than the predetermined dimming rate based on the dimming command, only the corresponding number of discharge lamps among the plurality of discharge lamps are lit. By turning off the remaining discharge lamps, a wide range of dimming can be achieved with simple control.
[0009]
The discharge lamp lighting device of the invention of claim 2 inputs a plurality of discharge lamps, a power supply circuit that lights each of the plurality of discharge lamps, and a dimming command from the outside, and the plurality of discharge lamps to the power supply circuit Each of the discharge lamps is turned on, turned off, and has a control circuit for controlling the brightness at the time of lighting.The control circuit controls the brightness to correspond to the specified dimming rate based on the dimming command, and performs the specified dimming. When the light rate becomes lower than a predetermined dimming rate, it has a control function to turn off the corresponding number of discharge lamps among the plurality of discharge lamps.
[0010]
In the discharge lamp lighting device according to the second aspect of the present invention, control is performed so that the luminance corresponds to the designated dimming rate based on the dimming command, and the designated dimming rate is lower than the predetermined dimming rate. Only a corresponding number of discharge lamps among a plurality of discharge lamps are turned on, their brightness is darkened, and the remaining discharge lamps are turned off, thereby enabling wide dimming.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a circuit configuration of a discharge lamp lighting device according to a first embodiment of the present invention. The discharge lamp lighting device according to the present embodiment is used as an edge light type liquid crystal backlight device 16 that illuminates the liquid crystal unit 15 from the side end surfaces by, for example, three discharge lamps 1a to 1c as shown in FIG. It has a dimming function. The discharge lamp lighting device according to the present embodiment is configured to supply high-voltage and high-frequency power to a plurality of, here three,

discharge lamps

1a, 1b, and 1c by inverter circuits 20a to 20c.
[0012]
Each of the inverter circuits 20a to 20c is a Royer inverter circuit, and includes two

oscillation transistors

7 and 7 as a pair, a base resistor 10 for controlling a current supplied to the bases of both

oscillation transistors

7 and 7, and a base winding. The inverter transformer 2 provided with the tertiary winding 5 and the capacitor 6 are configured.
[0013]
Each inverter transformer 2 includes a primary winding 4 provided with a center tap, a secondary winding 3 for supplying a lamp current, and the above-described tertiary winding 5.
[0014]
One end of each base resistor 10 is connected to a DC power supply 12, and the other end is connected to a connection line that returns from the tertiary winding 5 of the inverter transformer 2 to the oscillation transistor 7 via a drive switch 9. An intermediate tap of the primary winding 4 of the inverter transformer 2 is connected to a DC power source 12 via an inductor 8.
[0015]
The dimming control signal lines 22 a to 22 c from the dimming control circuit 21 are connected to the bases of the transistors constituting the driving switches 9 via the base resistors 11. As long as a dimming command is not input, the dimming control circuit 21 outputs a control signal for making each driving switch 9 conductive.
[0016]
In each of the inverter circuits 20a to 20c, when the DC power supply 12 is applied, a current flows to the primary winding 4 of the inverter transformer 2 through the inductor 8, and at the same time, the voltage output from the DC power supply 12 is the base resistance 10 The voltage is applied to the bases of the

oscillation transistors

7 and 7 through the drive switch 9.
[0017]
The

primary windings

4 and 3 of the inverter transformer 2 resonate with the reactance of the primary winding 4 and the tertiary winding 5 and the resonant capacitor 7, and the

primary windings

4 and 3 of the inverter transformer 2 are connected between the terminals of the tertiary winding 5 of the inverter transformer 2. A high voltage boosted by the turn ratio of the secondary winding 5 is induced. At the same time, a current flows in the tertiary winding 5 in the same direction as the current flowing in the primary winding 4 and self-oscillates. The

oscillation transistors

7 and 7 are alternately turned on at a frequency. The inverter transformer 2 boosts the voltage of the current flowing through the primary winding 4 by the turn ratio of the primary winding 4 and the secondary winding 3, and as a result, the high-voltage high-frequency current is supplied to each of the discharge lamps 1a to 1c. To light up.
[0018]
The dimming control circuit 21 is usually composed of a logic circuit using an operational amplifier, but here it is shown as a digital circuit for easy understanding of the function. The dimming control circuit 21 receives the dimming command signal S input from the outside at the input terminal 23, performs the comparison shown in Table 1, determines the number of lighting N and the luminance according to the comparison result, The dimming control signal generated based on the above is output to the dimming control signal lines 22a to 22c.
[0019]
[Table 1]

The dimming control signal is a pulse signal in which the duty of the L (low level) period with respect to one pulse period is adjusted to a ratio corresponding to the dimming command in the negative logic. In the case of a positive logic circuit, the duty of the H (high level) period for one pulse period is adjusted to a ratio according to the dimming command.
[0020]
Next, the lighting operation of the discharge lamp lighting device according to the first embodiment having the above-described configuration will be described with reference to FIGS.
[0021]
(1) Full lighting When full lighting, the dimming command S is a 100% command, and the control circuit 21 outputs a 100% lighting control signal to all the discharge lamps 1a to 1c3. In this case, a signal with a duty of 100% is output to the drive switch 9 of each of the three lamp inverter circuits 20a to 20c, each of the inverter circuits 20a to 20c operates at full power, and each of the discharge lamps 1a to 1c is set to 100%. Turn on with brightness.
[0022]
(2) When 100% to 60% dimming, 100% to 60% dimming command S (dimming voltage from 0V to first set voltage) is given to the control circuit 21 from the outside. The light control operation in section A in FIGS. 3 and 4 is performed by the control of steps S1, S2, and S3 in the flowchart of FIG. 2, and the lighting duty of each lamp is matched with the light control command S.
[0023]
Thereby, all the lamps of the discharge lamps 1a to 1c are lighted uniformly with a luminance of 100 to 60%, and the actual luminance of the entire apparatus is also adjusted to 100 to 60%. The lighting state of the three lamps at this time is three lamp lighting as shown in FIG.
[0024]
(3) When 60% to 45% dimming, 60% to 45% dimming command S (dimming voltage of the first set voltage to the second set voltage) is given to the control circuit 21 from the outside. The circuit 21 performs dimming operation in the section B in FIGS. 3 and 4 under the control of steps S1, S2, S4, and S5 in the flowchart of FIG. 2, one of the discharge lamps 1a is turned off, and the remaining discharge lamp 1b. , 1c are turned on, and each lighting duty is matched with the dimming command S.
[0025]
As a result, the two lamps 1b and 1c are uniformly lit with a luminance of 60 to 45%, and the actual luminance of the entire apparatus is adjusted to 40 to 30% (= 120 to 90% / 300%). The lighting state of the three lights at this time is as shown in FIG.
[0026]
(4) 45% to 20% dimming command 45% to 20% as a dimming command from the outside (second set voltage to dimming voltage of the set voltage that minimizes the brightness) is supplied to the control circuit 21 When given, the control circuit 21 performs dimming operation in the section C in FIGS. 3 and 4 under the control of steps S1, S2, S4 and S6 in the flowchart of FIG. 2, and turns off the two lamps 1a and 1c. Then, only one of the remaining discharge lamps 1b is turned on, and the lighting duty is matched with the dimming command S.
[0027]
Accordingly, only one discharge lamp 1b is lit with a luminance of 45 to 20%, and the actual luminance of the entire apparatus is adjusted to 15 to 7% (= 45 to 20% / 300%). The lighting state of the three lights at this time is as shown in FIG.
[0028]
As a result, as shown in FIG. 3, dimming can be performed only until the actual luminance of the entire apparatus reaches about 20% of that at the time of full lighting as shown in FIG. While using a discharge lamp, the actual luminance can be adjusted to a low luminance of about 1%, which is 1/3 of the conventional one, and the dimming range can be expanded.
[0029]
More generally, for example, in the case of conventional N discharge lamps (or discharge lamps having N sets of discharge lamps that are simultaneously turned on / off), the actual luminance of the entire apparatus is about 20% of that when fully lit. The discharge lamp lighting device according to the present embodiment can only be dimmed until the brightness becomes low, while using a discharge lamp with the same performance, it has a low brightness of 1 / N compared to about 20% of the conventional one. The actual luminance can be adjusted up to the range, and the dimming range can be expanded.
[0030]
Next, the discharge lamp lighting device of the 2nd Embodiment of this invention is demonstrated using FIG. 1, FIG. 6-FIG. The feature of the second embodiment is a simplified dimming function in which the three lamps are turned off in stages and the luminance is adjusted in stages in response to a dimming command from the outside. Therefore, the circuit configuration of the discharge lamp lighting device of the second embodiment is common to that of the first embodiment shown in FIG. Then, the functional configuration of the control circuit 21 is simplified, and as shown in FIG. 7, there are three levels of dimming commands: “bright”, “intermediate”, and “dark”, and all three lights are turned on according to each. Two lamps are lit and one lamp is lit.
[0031]
The light control operation by the discharge lamp lighting device of the second embodiment will be described. 7 and 8, when “bright” is input as the dimming command S, the control circuit 21 outputs a control signal for lighting all three lamps of the discharge lamps 1a to 1c with a duty of 100% (FIG. 6). In steps S11, S12, and S13).
[0032]
If the dimming command S is “intermediate”, the control circuit 21 turns off the discharge lamp 1a and outputs a control signal for turning on the remaining two lamps 1b and 1c with a duty of 100% (step S11, S12, S14, S15).
[0033]
If the dimming command S is “dark”, the control circuit 21 turns off the two lamps 1a and 1c and outputs a control signal for turning on only the remaining one of the discharge lamps 1b with a duty of 100%. (Steps S11, S12, S14, S16).
[0034]
According to the second embodiment, three-stage dimming can be performed only by switching on / off of 3 lamps, 2 lamps and 1 lamp, and the circuit can be simplified and multistage dimming can be performed.
[0035]
In the discharge lamp lighting device of the first and second embodiments, the number of discharge lamps is not limited to three, and the same applies to a discharge lamp lighting device that lights a larger number. it can.
[0036]
【The invention's effect】
As described above, according to the invention of claim 1, when the designated dimming rate becomes lower than the predetermined dimming rate based on the dimming command, only the corresponding number of discharge lamps among the plurality of discharge lamps are turned on. By turning off the remaining discharge lamps, a wide range of dimming can be achieved with simple control.
[0037]
According to the second aspect of the present invention, control is performed so that the brightness corresponding to the designated dimming rate is obtained based on the dimming command, and a plurality of releases are performed when the designated dimming rate is lower than the predetermined dimming rate. By turning on only the corresponding number of discharge lamps among the lamps to control their brightness and turning off the remaining discharge lamps, a wide range of dimming is possible.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of a discharge lamp lighting device according to a first embodiment of the present invention.
FIG. 2 is a flowchart of a dimming operation according to the above embodiment.
FIG. 3 is an explanatory diagram showing a relationship between a dimming voltage and a substantial luminance during the dimming operation according to the embodiment.
FIG. 4 is a control waveform diagram of a dimming operation according to the above embodiment.
FIG. 5 is an explanatory diagram showing transition of lighting / extinguishing states of each discharge lamp during the dimming operation of the discharge lamp lighting device according to the embodiment.
FIG. 6 is a flowchart of a dimming operation by the discharge lamp lighting device according to the second embodiment of the present invention.
FIG. 7 is an explanatory diagram showing the relationship between the dimming voltage and the actual luminance during the dimming operation according to the embodiment.
FIG. 8 is a control waveform diagram of a dimming operation according to the embodiment.
FIG. 9 is a side view of a conventional discharge lamp lighting device.
FIG. 10 is an explanatory diagram showing the relationship between the dimming voltage and the actual luminance during the dimming operation by the conventional discharge lamp lighting device.
[Explanation of symbols]
1a to 1c Discharge lamps 20a to 20c Inverter circuit 21 Control circuits 22a to 22c Dimming control signal line

Claims

Multiple discharge lamps,
A power supply circuit for lighting each of the plurality of discharge lamps;
A control circuit that inputs a dimming command from the outside and controls the power supply circuit to turn on / off each of the plurality of discharge lamps;
The control circuit has a control function of turning off a corresponding number of discharge lamps among the plurality of discharge lamps when a designated dimming rate is lower than a predetermined dimming rate based on the dimming command. A discharge lamp lighting device characterized.

Multiple discharge lamps,
A power supply circuit for lighting each of the plurality of discharge lamps;
A control circuit that inputs a dimming command from the outside and performs brightness control at the time of lighting, extinguishing, and lighting of each of the plurality of discharge lamps with respect to the power supply circuit,
The control circuit controls the brightness corresponding to the designated dimming rate based on the dimming command, and when the designated dimming rate is lower than a predetermined dimming rate, the plurality of discharge lamps are controlled. A discharge lamp lighting device having a control function of turning off a corresponding number of discharge lamps.