JP2004355864A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device composed by simplifying a circuit structure while meticulously controlling an operation state between a chopper circuit and an inverter circuit according to a light modulation level. <P>SOLUTION: The D.C. output voltage of the chopper circuit 3 can be varied by controlling the on and off states of a switching element Q3. The inverter circuit 4 converts the D.C. output outputted from the chopper circuit 3 to a high-frequency voltage, and applies the high-frequency voltage to a discharge lamp La through a resonance circuit comprising a capacitor C1 and an inductor L1. The output voltage of the chopper circuit 3 and the operation frequency of the inverter circuit 4 are collectively controlled by a control signal from a microcomputer 20. The microcomputer 20 lowers the output voltage of the chopper circuit 3 as compared with a normal lighting time in light modulation, and is provided with a table that is so set as to raise the operation frequency of the inverter circuit 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４７】
図示例では、予熱、始動、定常点灯の各動作モードを時間によって切り替えるように構成されている。つまり、電源が投入されると、マイコン２０ではチョッパ回路３およびインバータ回路４を予熱モードで動作させることにより、放電灯Ｌａのフィラメントに予熱電流を流し、電源投入から１ｓ後に始動モードに切り替える。始動モードでは、放電灯Ｌａに印加する電圧を上昇させて放電灯Ｌａを点灯させ、その後、放電灯Ｌａへの印加電圧を下げ、放電灯Ｌａに流す電流を多くする定常点灯モードに移行するのである。放電灯Ｌａを調光モードで点灯させる場合には、インバータ回路４の動作周波数を定常点灯時よりも上昇させることによって、インダクタＬ１を通して放電灯Ｌａに流れる電流を低減し、このときチョッパ回路３の出力電圧を定常点灯時よりも引き下げる。
【００４８】
上述のように、チョッパ回路３とインバータ回路４との動作をマイコン２０を用いて制御し、しかもテーブルによって両者の関係を設定するから、従来構成のように、チョッパ回路３とインバータ回路４との動作を１つの関係だけで一対一の関係に固定的に設定するのではなく、自由な組合せで設定することができ、結果的に放電灯Ｌａの動作状態に応じたきめ細かな制御が可能になる。しかも、チョッパ回路３とインバータ回路４とをマイコン２０の出力で直接制御するから、従来構成のようにチョッパ制御回路６とインバータ制御回路５とを別途に必要としていた従来構成に比較すると、部品点数が低減されて実装作業が容易になり、しかも部品点数の低減により実装スペースが低減すれることになる。
【００４９】
（実施形態２）
本実施形態は、図１に示した実施形態１の構成に、放電灯Ｌａに印加する電圧と放電灯Ｌａに流れる電流とを監視する構成を付加したものである。すなわち、コンデンサＣ３の両端間に２個の抵抗Ｒ１，Ｒ２の直列回路を接続してあり、チョッパ回路３の出力電圧であるコンデンサＣ３の両端電圧を抵抗Ｒ１，Ｒ２により分圧して、マイコン２０に設けたポートに入力してある。抵抗Ｒ１，Ｒ２により分圧された電圧は放電灯Ｌａへの印加電圧に比例する電圧になる。また、予熱トランスＴ１の１次巻線における低電位側の一端と放電灯Ｌａとの間に１次巻線を挿入したカレントトランスＴ２を設けてランプ電流を検出しており、カレントトランスＴ２の２次出力をマイコン２０に設けたポートに入力することによって、マイコン２０にランプ電流を取り込んでいる。後述するように、マイコン２０では、抵抗Ｒ１，Ｒ２により分圧した電圧がテーブルにより設定した目標値に保たれるようにチョッパ回路３のスイッチング素子Ｑ３を制御し、カレントトランスＴ２の２次出力がテーブルにより設定した目標値に保たれるようにインバータ回路４のスイッチング素子Ｑ１，Ｑ２を制御する。
【００５０】
ところで、本実施形態において放電灯Ｌａの電流−電圧特性（以下、ランプ特性という）が図３にＡで示す曲線のようになるものとする。図３にはチョッパ回路３およびインバータ回路４の定数（とくに、インダクタＬ１、コンデンサＣ１、Ｃ５）を一定値として、チョッパ回路３の出力電圧とインバータ回路４の動作周波数との組合せを種々変更した場合の動作例を示している。すなわち、図３においては、チョッパ回路３の出力電圧とインバータ回路４の動作周波数との４種類の組合せを示してあり、それぞれＢ１〜Ｂ４の符号で区別してある。チョッパ回路３の出力電圧とインバータ回路４との動作周波数との組を（出力電圧、動作周波数）として表すと、曲線Ｂ１は（１８０Ｖ、５５ｋＨｚ）、曲線Ｂ２は（２８０Ｖ、１０７ｋＨｚ）、曲線Ｂ３は（１８０Ｖ、９７ｋＨｚ）、曲線Ｂ４は（２８０Ｖ、５５ｋＨｚ）に対応する。以下では、チョッパ回路３の出力電圧とインバータ回路４の動作周波数との組合せによる総合的な電流−電圧特性を点灯回路特性と呼ぶ。
【００５１】
図示する放電灯Ｌａの定格ランプ電流は４００ｍＡ付近（ここでは、４３０ｍＡとする）であり、定格ランプ電流付近においてランプ特性に点灯回路特性が略直交する場合には、無効電流が多く効率が低下することになる。したがって、ランプ特性と点灯回路特性とが交差する角度はできるだけ小さくするのが望ましい。しかしながら、両者が交差しなくなれば放電灯Ｌａが立ち消えすることになる。図示例において曲線Ｂ１は、ランプ電流が４３０ｍＡを満足する交点の得られない点灯回路特性を示している。一方、調光状態では、ランプ特性の傾きが大きくなるから、点灯回路特性の傾きを大きくしなければ立ち消えが生じ、また曲線Ｂ２のようにランプ特性と点灯回路特性との交点が２箇所に隣接して形成されると、いわゆるジャンプ現象を生じるなど放電灯Ｌａの挙動が不安定になってちらつきを生じることになる。
【００５２】
つまり、曲線Ｂ３，Ｂ４のように調光レベルに応じてチョッパ回路３の出力電圧とインバータ回路４の動作周波数との両方の出力を変化させれば、定格点灯時には効率よく動作させることができ、しかも低光束まで調光が可能になる。ただし、調光レベルに応じてチョッパ回路３の出力電圧とインバータ回路４の動作周波数とを個別部品を用いて適正に制御しようとすると、回路構成が複雑になる上に回路規模が大きくなるという問題が生じる。また、従来構成として説明したように小規模の回路構成では適正な制御を行うことは困難である。
【００５３】
そこで、本実施形態ではマイコン２０を用いているのであって、調光レベルに応じてチョッパ回路３の出力電圧とインバータ回路４の動作周波数との両方を制御することによって、複雑な構成の回路を用いたり回路規模が大きくなったりすることなく適正な制御を行うことが可能になる。ここで、放電灯Ｌａを適正に点灯させるようにマイコン２０に設けたテーブルの一例を表２に示す。このように、マイコン２０にテーブルを持たせるだけで、簡単な構成ながら低出力まで調光可能になる。他の構成および動作は実施形態１と同様である。
【００５４】
【表２】

【００５５】
（実施形態３）
本実施形態は、図４に示すように、基本的には図１に示した実施形態１の構成に、リモコン送信器から送出される赤外線を伝送媒体としたワイヤレス信号を受信するためのワイヤレス受信部１１を付加したものである。ワイヤレス受信部１１は、フォトダイオードのような受光素子と、増幅回路や波形整形回路のように受光素子の出力からワイヤレス信号に相当するパルス信号を抽出する回路部とを備えるものであって、ワイヤレス受信部１１から出力されるパルス信号をマイコン２０に入力する構成を採用している。また、マイコン２０とインバータ回路４との間には、マイコン２０から出力される制御信号をインバータ回路４に設けたスイッチング素子を制御可能な電圧に変換するレベルシフト回路を含んだドライバ回路７を挿入してある。
【００５６】
ワイヤレス受信部１１から出力されるパルス信号は、マイコン２０の内部においてチョッパ回路３とインバータ回路４とを制御する信号に変換される。すなわち、マイコン２０には従来構成において必要であった信号処理部１２やパルス幅−電圧変換部１３（図３７参照）が不要であって、マイコン２０において、電圧信号のようなアナログ信号を生成することなく、パルス信号からチョッパ回路３およびインバータ回路４を制御する信号をデジタル処理によって直接生成する。ここに、調光に際してはインバータ回路４の動作周波数を高くするとともに、チョッパ回路３の出力電圧を低下させる関係とする。
【００５７】
本実施形態の動作を簡単に説明する。上述したように、ワイヤレス受信部１１において受信したワイヤレス信号に対応するパルス信号は、マイコン２０に直接入力あれ、マイコン２０の内部においてヘッダやトレーラが除去され、ワイヤレス信号に含まれるパルス信号のうち制御用のパルス信号から、マイコン２０のクロック信号を分周した形で２種類の制御信号を生成する。一方の制御信号はインバータ回路４の動作周波数の制御に用いられ、他方の制御信号はチョッパ回路３の出力電圧の制御に用いられる。つまり、リモコン送信器から受信したワイヤレス信号を用いて、チョッパ回路３とインバータ回路４とに用いる２つの制御信号を生成するのである。
【００５８】
ここに、ワイヤレス信号に含まれる制御用のパルス信号のうち、各調光レベルに対応するデータ部分に対応するＨレベルの期間とＬレベルの期間をあらかじめ決めておくことにより、ワイヤレス信号に１対１で対応する制御信号をマイコン２０で生成することが可能になる。その結果、ワイヤレス信号により指示された調光レベルに対応させて、チョッパ回路３の出力電圧とインバータ回路４の動作周波数とを一義的に決めることができるので、リモコンの送信器から送信された調光レベルをチョッパ回路３の出力電圧とインバータ回路４の動作周波数とにそのまま反映させることができ、チョッパ回路３の出力電圧およびインバータ回路４の出力電圧に誤差がほどんど生じないのである。
【００５９】
なお、本実施形態では、チョッパ回路３やインバータ回路４を構成する部品の定数のばらつきを補正する手段については記載していないが、この種の定数のばらつきの補正には、可変抵抗器などによる調整用素子をチョッパ回路３やインバータ回路４に適宜に付加すればよい。このような調整を行った上でマイコン２０による制御を行うことにより、製品ごとのばらつきを抑制することができる。
【００６０】
本実施形態におけるマイコン２０の機能を表すブロック図を図５に示す。マイコン２０にはワイヤレス受信部１１からのパルス信号が入力される調光信号抽出手段２１が設けられ、パルス信号から調光信号のような制御情報に対応するデータビット列（制御用のパルス信号）を抜き出す。このデータビット列は、リモコン送信器から指示されたオンオフの情報あるいは調光レベルの情報を表す。調光信号抽出手段２１の出力は、変換テーブル２２に入力される。変換テーブル２２は、ワイヤレス信号から抽出されるデータビット列にマイコン２０のクロック信号の分周比を対応付けたＲＯＭからなり、ワイヤレス信号から抽出されたデータビット列がパラレルデータまたはシリアルデータの形で変換テーブル２２に照合されることによってクロック信号の分周比が求められる。ここに、変換テーブル２２には、チョッパ回路３に対応するデューティテーブルとインバータ回路４に対応する周波数テーブルとが設けられている。変換テーブル２２により決定された分周比は出力パルス生成手段２３に入力され、出力パルス生成手段２３では入力された分周比に従ってクロック信号を分周する。つまり、出力パルス生成手段２３は、カウンタもしくはタイマを構成しており、チョッパ回路３とインバータ回路４とにそれぞれ与える制御信号のＨレベルの期間とＬレベルの期間と持つパルス信号を生成する。つまり、チョッパ回路３およびインバータ回路４に与える制御信号の周波数とオンデューティとが決定される。さらに、出力パルス生成手段２３から出力されたパルス信号はＰＷＭ出力手段２４を介して、チョッパ回路３とインバータ回路４とにそれぞれ制御信号として与えられる。
【００６１】
出力パルス生成手段２３およびＰＷＭ出力手段２４においてクロック信号からＰＷＭ信号である制御信号を生成する動作について、図６を用いて簡単に説明する。図６（ａ）に示すクロック信号の周波数はＰＷＭ信号の周期に比較して十分に短いが、図６では実際の周期よりも大幅に長周期で示している。
【００６２】
図６において期間ｔ０〜ｔ１は期間ｔ２〜ｔ３よりも放電灯Ｌａへの電力供給が多い場合を示している。時間ｔ０〜ｔ１においては、変換テーブル２２に設けたデューティテーブルから、オン時間が２クロック分、オフ時間が３クロック分となるデータが選択されることによってチョッパ回路３の出力電圧が決定され、変換テーブル２２に設けた周波数テーブルから、分周比が１／８であるデータが選択されることによってインバータ回路４の動作周波数が決定される。同様にして、時間ｔ２〜ｔ３においては、変換テーブル２２に設けたデューティテーブルから、オン時間が１クロック分、オフ期間が３クロック分のデータが選択され、変換テーブル２２に設けた周波数テーブルから、分周比が１／４であるデータが選択される。もっとも実際には、マイコン２０のクロック周波数は８ＭＨｚ以上であって、インバータ回路４の動作周波数を５０ｋＨｚ付近に設定しているから、分周比は１／１６０以下になる。
【００６３】
上述のように、変換テーブル２２において、１つのデータビット列からチョッパ回路３とインバータ回路４とにそれぞれ対応した分周比を生成するから、変換テーブル２２の内容に応じてチョッパ回路３の動作とインバータ回路４の動作とを任意に設定することが可能になる。しかも、変換テーブル２２を用いることによって、アナログ信号を介さずにデータビット列と分周比との対応関係によってデジタルデータによって制御信号を生成するから、リモコン送信器からのワイヤレス信号に対して誤差のほとんど生じない制御信号を生成することが可能になる。
【００６４】
ところで、放電灯Ｌａの電流−電圧特性の負特性領域での傾きが最大となる点付近よりも低い深調光レベルでは、放電灯Ｌａの点灯状態が不安定になり立ち消えしやすくなるから、深調光レベルでは、放電灯Ｌａを安定点灯を維持するために他の調光レベルとは異なる制御が必要になる。本実施形態では、ランプ電流波形の振幅を一定周期で一定期間だけ他の期間よりも大きくすることによって、深調光レベルにおいて放電灯Ｌａの安定点灯を維持するようにしている。
【００６５】
いま、変換テーブル２２に設けた周波数テーブルにおいて、図７のように、調光レベル１〜ｎに分周比Ｘ１〜Ｘｎを対応付けて設定されているものとする。各分周比Ｘ１〜Ｘｎはインバータ回路４の動作周波数ｆ１〜ｆｎに対応する。また、図７において破線Ｄ１で示した規定値よりも深調光レベルであるときに、インバータ回路４の制御を、破線Ｄ１よりも浅調光レベルであるときとは異ならせるものとする。図７では破線Ｄ１よりも深調光レベルであるときの分周比Ｘ１……を、破線Ｄ１よりも浅調光レベルであるときの分周比……Ｘｎに対して一対一に対応付けていることを矢印によって表している。つまり、インバータ回路４は動作周波数ｆ１〜ｆｎを変化させることによって放電灯Ｌａのランプ電流を変化させることができるから、深調光レベルであるときの分周比Ｘ１……と浅調光レベルであるときの分周比……Ｘｎとを一対一に対応付けておき、深調光レベルであるときに、分周比Ｘ１……を選択すると、一定周期で一定期間だけ分周比Ｘ１……に対応する分周比……Ｘｎが選択されるようにしている。
【００６６】
たとえば、分周比Ｘ１は分周比Ｘｎに対応付けられ、調光レベルが１であるときには、分周比Ｘ１（つまり、周波数ｆ１）が選択されるが、一定周期で一定期間ごとに分周比Ｘｎ（つまり、周波数ｆｎ）が選択され、ランプ電流が一定周期で一定期間ごとに大きくなるようにしてある。ここに、深調光レベルと浅調光レベルとを対応付けるために別途に制御テーブルが必要であり、深調光レベルが選択されたときには、当該調光レベルに対応する浅調光レベルが選択され、変換テーブル２２からは両調光レベルに対応する分周比が交互に出力されることになる。分周比Ｘ１を選択する時間をＴ１、分周比Ｘｎを選択する時間をＴ２（＜Ｔ１）とすれば、図８に示すように、インバータ回路４の動作周波数として周波数ｆ１が選択されるときには、一定周期（Ｔ１＋Ｔ２）で一定時間Ｔ２だけ周波数ｆｎが選択される。このような制御によって、インバータ回路４に設けた各スイッチング素子Ｑ１，Ｑ２（図１参照）のオンオフは図９（ａ）（ｂ）のようになり、立ち消え対策が必要な深調光レベルでは、ランプ電流波形は図９（ｃ）のように周波数および振幅が変調され、振幅が周期的に大きくなるので立ち消えを防止することができる。なお、制御テーブルを設ける代わりに、調光レベル１〜ｎを数値で表しておき、破線Ｄ１に対して深調光レベルが選択されたときには、調光レベルの和が、たとえば（ｎ＋１）になるような浅調光レベルを選択するようにしてもよい。このような選択のルールを決めておけば、調光レベル１に対して分周比Ｘ１，Ｘｎが選択され、調光レベル２に対して分周比Ｘ２，Ｘ（ｎ−１）が選択される。
【００６７】
上述した例では、深調光レベルにおいてランプ電流波形の振幅を周期的に変化させるために、周波数テーブルとは別に制御テーブルが必要としていたが、図１０に示すように、周波数テーブルにおいて深調光レベルにおいて、調光レベルに対して、２種類の分周比Ｘ１……、Ｙ１……をあらかじめ設定しておいてもよい。つまり、分周比Ｘ１……と分周比Ｙ１……とは一対一に対応しており、分周比Ｘ１……が選択されるとインバータ回路４の動作周波数が高くなってランプ電流が小さくなり、分周比Ｙ１……が選択されると対応する分周比Ｘ１……が選択されたときよりもインバータ回路４の動作周波数が低くなってランプ電流が大きくなるように、分周比Ｘ１……と分周比Ｙ１……とが対応付けられる。ただし、調光レベルに対して２つの分周比Ｘ１……、Ｙ１……を対応付けるのは、破線Ｄ１よりも深い調光レベルのみである。
【００６８】
深調光レベルにおいてランプ電流波形の振幅を周期的に変化させるために、図７に示した周波数テーブルでは、破線Ｄ１に対して深調光レベルの分周比Ｘ１……を破線Ｄ１に対して浅調光レベルの分周比……Ｘｎと一対一に対応つけていたが、図１１に示すように、多体一に対応させてもよい。要するに、破線Ｄ１に対して深調光レベルであるすべての分周比Ｘ１……を、破線Ｄ１に対して浅調光レベルである１つの分周比Ｘ（ｎ−２）に対応付けるのである。このように決めておけば、深調光レベルにおける分周比の選択を単純化することができる。
【００６９】
上述の例では、２種類の分周比を一定時間Ｔ１，Ｔ２で交互に選択しているが、一般に調光レベルが深いほど立ち消えが生じやすくなるから、調光レベルが深いほどランプ電流の振幅を大きくする周期（Ｔ１＋Ｔ２）を短くし、ランプ電流の振幅を大きくする時間Ｔ２を長くしてもよい。ここに、周期（Ｔ１＋Ｔ２）と時間Ｔ２との少なくとも一方を調光レベルに応じて制御すればよい。このような制御を行うために変換テーブル２２には時間Ｔ１，Ｔ２を調光レベルに対応付けた制御テーブルが必要になる。なお、当然のことながら、立ち消え対策が必要な調光レベルの範囲内であっても立ち消えの生じやすさは異なるので、調光レベルに応じて周期（Ｔ１＋Ｔ２）および時間Ｔ２を選択する必要がある。
【００７０】
周波数テーブルとしては、図１２に概念図として示すように、各調光レベル１〜ｎに、それぞれ３個以上の分周比Ａ〜Ｅを組み合わせて対応付けるようにしてもよい。図示例では、１つの調光レベル１〜ｎに５個の分周比Ａ〜Ｅを組にして対応付けてあり、所定時間ずつ各分周比Ａ〜Ｅが循環的（サイクリック）に選択されるようにしてある。たとえば、立ち消え対策が必要である深い調光レベル１においては、調光レベル１に対する基本の分周比Ａと、分周比Ａよりもランプ電流が大きくなる（インバータ回路４の動作周波数が低くなる）分周比Ｂとを用い、分周比Ａが４回選択される間に分周比Ｂが１回選択されるようにする。このような処理によって、ランプ電流を周期的に大きくすることが可能になる。また、ランプ電流を周期的に変化させる必要のない浅調光レベルに対しては、１つの分周比Ｅを設定し、５回の選択においてすべて分周比Ｅを選択すればよい。このような処理により、周波数テーブルの内容の設定のみで、深調光レベルと浅調光レベルとに対して同一処理による対応が可能になる。なお、図示例では破線Ｄ１に対して深調光レベルにおいて、それぞれ２種類の分周比Ａ〜Ｄを対応付けているが、３種類以上の分周比を対応付けるようにすることも可能である。また、各調光レベル１〜ｎに対して５個の分周比を対応付けているが、対応付ける分周比の個数も適宜に選択することが可能である。このような周波数テーブルを用いることによって、インバータ回路４の動作周波数を変更する周期の精度を高くすることができ、また分周比の組み合わせを適宜に設定することによってランプ電流波形を多様に変化させることが可能になる。
【００７１】
図１２に示した周波数テーブルでは、破線Ｄ１に対して浅調光レベルであっても１つの調光レベルに複数個の分周比を対応付けているが、図１３に示すように、浅調光レベルでは１個の分周比のみを対応付けるようにしてもよい。このような設定とすれば、図１２に示した周波数テーブルに対して周波数テーブルの記憶容量を低減することが可能である。
【００７２】
なお、上述の例ではインバータ回路４の動作周波数のみを制御するものとして周波数テーブルにおける分周比を例示したが、変換テーブルにおいてチョッパ回路３の動作を制御するデューティテーブルについても同様に設定することが可能である。
【００７３】
（実施形態４）
本実施形態は、図１４に示すように、基本的には実施形態２と同様の回路構成を有しており、図２と同符号を付した部材は同機能を有する。ただし、予熱用の回路は図では省略してある。また、検出手段１４はチョッパ回路３の出力電圧を検出するものであって実施形態２における抵抗Ｒ１，Ｒ２と等価な機能を有し、検出手段１５は放電灯Ｌａのランプ電流を検出する機能を有するものであって実施形態２におけるカレントトランスＴ２と等価な機能を有する。各検出手段１４，１５の出力はそれぞれＡＤ変換器１６，１７を介してマイコン２０に入力される。マイコン２０から出力される制御信号は、ドライバ７を介してインバータ回路４のスイッチング素子Ｑ１，Ｑ２に与えられ、またドライバ８を介してチョッパ回路３のスイッチング素子Ｑ３に与えられる。さらに、マイコン２０には後述するようにメモリからなる設定値記憶手段２５が付加される。
【００７４】
本実施形態では、インバータ回路４の動作周波数は、一定周期ごとに適宜の時間だけ周波数が変更される。ここに、検出手段１５において検出されるランプ電流は、ＡＤ変換器１７によりデジタル値に変換された後にマイコン２０に入力され、設定値記憶手段２５における設定値との差分が求められる。つまり、設定値記憶手段２５では、調光レベルと放電灯Ｌａの出力（ランプ電流）の設定値とが対応付けられている。マイコン２０では、この差分を小さくするように、チョッパ回路３のスイッチング素子Ｑ３のオンデューティと動作周波数との少なくとも一方を変化させ、放電灯Ｌａのランプ電流が上記設定値に保たれようにフィードバック制御を行う。ただし、フィードバック制御によってスイッチング素子Ｑ３の動作を変更する周期は、インバータ回路４において動作周波数が変更されている周期よりも長く設定されている。
【００７５】
従来の技術として説明したように、インバータ回路４の動作周波数を変調することにより低光束時において安定に点灯させることが提案されている。しかしながら、マイコン２０を用いてインバータ回路４の動作周波数を毎周期連続的に変化させる構成を実現しようとすると、高速で演算処理が行えるマイコン２０を用いる必要がある。また、インバータ回路４だけでなく、チョッパ回路３やワイヤレス信号の処理にもマイコン２０を用いるから、さらに高速かつ高性能なマイコン２０が要求され高コストになる。
【００７６】
また、ランプ出力（ランプ電流とランプ電圧との少なくとも一方）を検出してフィードバック制御を行い、ランプ出力の安定化を図る構成も従来から知られている。アナログ回路を用いてフィードバック制御を行う場合には、チョッパ回路３のオンデューティやインバータ回路４の動作周波数を逐次更新することができるが、同様のフィードバック制御をマイコン２０によって実現しようとすれば、高速な演算処理が要求される。とくに、低光束時において立ち消えを防止して安定に点灯させるには、実施形態３のようにインバータ回路４の動作周波数を切り替える必要があり、このような動作には高速性が要求される。
【００７７】
そこで、本実施形態では、インバータ回路４のスイッチング素子Ｑ１，Ｑ２の動作周波数（スイッチング周波数）を簡易的に変化させる技術と、チョッパ回路３の出力電圧およびインバータ回路４の動作周波数を更新する周期を比較的長くしたフィードバック制御の技術とを組み合わせることによって、比較的低性能で安価なマイコン２０を用いながらもチョッパ回路３の出力電圧とインバータ回路４の動作周波数との制御を可能とし、放電灯Ｌａの低光束域での安定点灯を実現している。
【００７８】
本実施形態の動作について説明する。図１５（ａ）に示すように、インバータ回路４に設けたスイッチング素子Ｑ１、Ｑ２の駆動周波数は、調光レベルに応じて決まる基準の周波数ｆ１に対して、周期Ｔｂごとに時間Ｔａだけ周波数ｆ２（ｆ１≧ｆ２）に変更される。この動作によって、図１５（ｂ）のように、放電灯Ｌａの印加電圧Ｖｌａは、周期Ｔｂで時間Ｔａだけパルス状に変化する。その結果、図１５（ｃ）のように、放電灯Ｌａのランプ電流Ｉｌａが一時的に増加し、ランプの立ち消えが防止される。なお、図１４には調光信号を示していないが、実施形態３と同様に外部から適宜に調光信号を入力するものとする。
【００７９】
一方、検出手段１５で検出したランプ電流を、図１５（ａ）に示す時間ｔ１〜ｔ２においてマイコン２０に入力し、時間ｔ１〜ｔ２における積算値または平均値を求めて設定値記憶手段２５に格納されている設定値との差分を求める。マイコン２０では、求めた差分から放電灯Ｌａのランプ電流を設定値に保つのに必要なインバータ回路４の動作周波数を演算し、演算により求めた駆動周波数を時刻ｔ２においてインバータ回路４の動作周波数として適用する。すなわち、時間ｔ１〜ｔ２におけるランプ出力（ランプ電流）の平均的な値によってランプ出力を補正するのであって、時間ｔ１〜ｔ２＝Ｔｃとすると、時間Ｔｃの周期でインバータ回路４の動作周波数をフィードバック制御により更新することになる。時間Ｔａと周期Ｔｂと時間Ｔｃとの関係は、Ｔａ＜Ｔｂ＜Ｔｃになる。周期Ｔｂは、立ち消え防止のために数１００μｓ〜数ｍｓに設定するのが望ましく、低光束を実現するにはランプ電流が増加している期間が短いほど光出力を小さくできるので、周期Ｔｂに比べて時間Ｔａは、およそ１／５〜１／１０に設定するのが望ましい。つまり、時間Ｔａは数１０μｓ〜数１００μｓになる。
【００８０】
ところで、チョッパ回路３に設けたコンデンサＣ３の容量は有限であって、コンデンサＣ３の両端電圧は、交流電源１からの入力電圧の半周期のリップルを含むように変化し、ランプ出力にもこの影響が現れる。したがって、フィードバック制御においてリップル成分の影響を受けないようにするために、時間Ｔｃは交流電源１の電圧の半周期ないしその整数倍に設定するのが望ましい。
【００８１】
本実施形態では、ランプ出力の安定化のためにインバータ回路４の動作周波数を制御する例を示したが、検出手段１４の出力に基づいてチョッパ回路３の出力電圧（コンデンサＣ３の両端電圧）を制御する場合も同様である。また、望ましくはチョッパ回路３の出力電圧とインバータ回路４の動作周波数とをともにフィードバック制御する。
【００８２】
上述したように、インバータ回路４の動作周波数を２段階に切り替える程度の簡易的な動作とし、しかもランプ出力のフィードバック制御を行う際の動作周波数の更新を比較的長い周期で行うことができるから、比較的低性能で安価なマイコン２０を用いても放電灯Ｌａの立ち消えを防止し、かつランプ出力の安定化を図ることができ、低光束時の安定点灯が可能となる。なお、図１４に示す例ではランプ出力の検出にランプ電流を検出しているが、たとえば、インバータ回路４のスイッチング素子Ｑ１，Ｑ２を通過する電流や共振回路（インダクタＬ１とコンデンサＣ１からなる）の共振電流など、放電灯Ｌａの出力を等価的に検出する構成を採用してもよい。
【００８３】
（実施形態５）
本実施形態は、実施形態４と同様に、インバータ回路４の動作周波数を２段階に切り替えるように動作するものであって、マイコン２０に設定される２種類の動作周波数を、基本周波数（のデータ）と周波数変化幅（のデータ）との組合せとしたものである。周波数変化幅は調光レベルに応じて複数段階に設定し、マイコン２０には調光レベルと各段階の周波数変化幅とを対応付けた変換テーブル（図５に示した変換テーブル２２に相当）を設ける。したがって、調光レベルに応じた周波数変化幅を基本周波数に加算することによって、各調光レベルにおけるインバータ回路４の動作周波数を決定する。
【００８４】
以下、具体的に説明する。マイコン２０が出力可能な信号の分解能をα、図１５の周波数ｆ１に対応する周波数データをＤｆとすると（Ｄｆは任意の整数）、これらの関係は、ｆ１＝１／（Ｄｆ×α）となる。各調光レベル毎に周波数データＤｆを設定することにより、各調光レベルに対するインバータ回路４の動作周波数を設定する。ここで、周波数変化幅に対応するデータをＤｘとし（Ｄｘは任意の整数）、図１５の周波数ｆ２への変化時に、ｆ２＝１／（（Ｄｆ＋Ｄｘ）×α）という形で、Ｄｆ→Ｄｆ＋Ｄｘに置き換えるようにマイコン２０での処理を行うことで、動作周波数の切替を実現できる。
【００８５】
また、本実施形態において、実施形態４に示すようなフィードバック制御による動作周波数の更新を周波数データＤｆの値を変えることで更新すれば周波数変化幅を略一定とすることができる。さらに、周波数変化幅のデータＤｘの値は、たとえば実施形態３において説明した立ち消え対策が必要になる深調光レベルの範囲において適宜の自然数を設定すればよく、立ち消え対策が不要である浅調光レベルにおいてはＤｘ＝０に設定すればよい。他の構成および動作は実施形態４と同様である。
【００８６】
（実施形態６）
本実施形態はマイコン２０によってインバータ回路４の動作周波数を切り替える際に、切替のタイミングをマイコン２０とは別に設けた外部回路からのトリガによって与えるものである。インバータ回路４の動作周波数を切り替えることによってランプ出力を変化させながらも、放電灯Ｌａの光出力の変化が目に見えないようにするには、一般に動作周波数を切り替える周期を１０ｍｓ以下にすることが必要である。
【００８７】
そこで、本実施形態では、図１６に示すように、交流電源１を整流回路２により整流した脈流電圧を、２段階に設定した閾値Ｔｈ１，Ｔｈ２とそれぞれ比較する比較器ＣＰ１，ＣＰ２を設け、両比較器ＣＰ１，ＣＰ２の出力を比較器ＣＰ３で比較することによって、動作周波数の切替を指示するパルス信号を生成している。
【００８８】
図１６に示す構成の動作を図１７に示す。いま、交流電源１の周波数を５０Ｈｚとすると、図１７（ａ）に示す整流回路２から出力される脈流波形の周期は１０ｍｓになる。各比較器ＣＰ１，ＣＰ２の立ち上がりと立ち下がりとが図１７（ｂ）（ｃ）に示すタイミングになるように閾値Ｔｈ１，Ｔｈ２を設定しておけば、２つの比較器ＣＰ１，ＣＰ２の出力を組み合わせた比較器ＣＰ３の出力では、図１７（ｃ）のように、立ち上がりと立ち下がりとを１０ｍｓの間に４つ得ることができる。つまり、比較器ＣＰ３の出力をマイコン２０に入力し、４つのタイミングをトリガにしてインバータ回路４の動作周波数を切り替えるようにすれば、約２．５ｍｓの周期で動作周波数の切替が可能になる。本実施形態では、２つの閾値Ｔｈ１，Ｔｈ２を設けることによって、マイコン２０へのトリガを得るようにしているが、トリガの周期をさらに短い周期とする必要があれば３個以上の閾値を設定すればよい。他の構成および動作は実施形態５と同様である。
【００８９】
（実施形態７）
本実施形態は、図１８に示すように、基本的には実施形態１の回路構成に、ランプ電圧検出手段９を付加したものである。マイコン２０は、インバータ回路４のスイッチング素子Ｑ１，Ｑ２に対してドライバ７を介して制御信号ｏｕｔ１を与え、チョッパ回路３のスイッチング素子Ｑ３にドライバ８を介して制御信号ｏｕｔ２を与える。また、ランプ電圧検出手段９は、ランプ電圧があらかじめ設定されたしきい値を超えると出力が反転するようにコンパレータなどを用いて構成され、ランプ電圧検出手段９の出力はマイコン２０の外部割込み機能を持つ端子に入力される。
【００９０】
本実施形態では、ランプ電圧検出手段９の出力の立ち上がりまたは立ち下がりにより、マイコン２０がチョッパ回路３およびインバータ回路４への制御信号ｏｕｔ１，ｏｕｔ２を停止する。この動作によって、放電灯Ｌａを外した場合や、放電灯Ｌａの異常によって負荷インピーダンスが急激に上昇した場合などであって、放電灯Ｌａの両端電圧（ランプ電圧）Ｖｌａが急激に上昇したときに、素子へのストレスが過大になって破壊に至る前にインバータ回路４の動作を停止させることが可能になる。すなわち、図１９（ａ）のように、時刻ｔ３において異常が発生し、時刻ｔ４においてランプ電圧Ｖｌａがランプ電圧検出手段９に設定されたしきい値（一点鎖線で示す）を超えると、図１９（ｂ）のように、ランプ電圧検出手段９の出力が反転して立ち下がり、マイコン２０では制御信号ｏｕｔ１，ｏｕｔ２を即座に停止させるのである。このように、放電灯Ｌａの以上のうちランプ電圧Ｖｌａが急激に変化するような異常に対して、マイコン２０に割込をかけるだけで、マイコン２０を即座に停止させることができ、異常に対する回路保護を行うことができる。
【００９１】
（実施形態８）
本実施形態は、図２０に示すように、実施形態７の構成におけるランプ電圧検出手段９に代えて、ランプ電圧検出手段９′とＡＤ変換器１０とを設けたものである。実施形態７のランプ電圧検出手段９は２値出力であったのに対して、本実施形態のランプ電圧検出手段９′はランプ電圧Ｖｌａの包絡線に対応した直流電圧（たとえば、平均電圧）を出力するものである。つまり、マイコン２０にはランプ電圧Ｖｌａに相当する電圧がＡＤ変換器１０を介して入力される。
【００９２】
本実施形態では、マイコン２０においてランプ電圧検出手段９′で検出したランプ電圧Ｖｌａに相当する電圧を、マイコン２０にあらかじめ設定したしきい値と比較し、ランプ電圧Ｖｌａがしきい値を超えると、マイコン２０がチョッパ回路３およびインバータ回路４への制御信号ｏｕｔ１，ｏｕｔ２の出力を停止するように構成してある。したがって、放電灯Ｌａの寿命末期において、フィラメントに塗布されているエミッタの減少によって生じる半波放電状態（エミレス状態）になると、ランプ電圧Ｖｌａの上昇を検出してチョッパ回路３およびインバータ回路４の動作を停止させることができ、結果的に素子へのストレスの増加を抑制することができる。
【００９３】
上述したエミレス状態などの異常の場合には、比較的緩やかなランプ電圧Ｖｌａの変化を捉えることが必要であるから、ランプ電圧検出手段９′の出力をＡＤ変換器１０によりデジタル値に変換する構成を採用し、ランプ電圧Ｖｌａに相当する値をマイコン２０に入力して、マイコン２０の内部で演算処理を施すとともに判定する構成を採用している。
【００９４】
たとえば、図２１（ａ）のようなランプ電圧検出手段９′の出力Ｖｙに相当するデジタル値をマイコン２０において時刻ｔ５〜ｔ８の一定周期で読み込み、マイコン２０において、時刻ｔ６〜ｔ８のように３回連続してしきい値（一点鎖線）を超えたときに異常と判断し、図２１（ｂ）のように、マイコン２０がチョッパ回路３およびインバータ回路４への制御信号ｏｕｔ１，ｏｕｔ２を停止するのである。
【００９５】
なお、図２１に示す例では、ランプ電圧検出手段９′の出力が３回連続してしきい値を超えた場合に異常と判断しているが、所定回数毎に平均値を求め、求めた平均値と適宜のしきい値とを比較してエミレス状態を判定したり、平均値が所定回数連続してしきい値を超えるときに、異常と判断するようにしてもよい。本実施形態では、放電灯Ｌａのランプ電圧が比較的緩やかに変化するような異常に対して、ランプ電圧の平均値を求めたり、ランプ電圧がしきい値を超える回数を求めたりすることによって、ソフト的な処理による判定で停止することにより、異常に対する保護を精度よく行うことができる。他の構成および動作は実施形態７と同様である。
【００９６】
（実施形態９）
本実施形態は、図２２に示すように、実施形態８の構成においてマイコン２０に設定値記憶手段２５を付加したものである。設定値記憶手段２５には、調光レベルごとに設定したしきい値がテーブルの形で格納されている。
【００９７】
放電灯Ｌａの特性では、図２３に示すように、調光レベルが深くなるとランプ電圧Ｖｌａが上昇する傾向にある。したがって、放電灯Ｌａのエミレス状態をランプ電圧Ｖｌａによって検出する場合に、調光レベルに応じて異常と判断するためのしきい値を変化させなければならない。たとえば、放電灯Ｌａが１００％点灯であるときのランプ電圧Ｖｌａに対してしきい値を設定していると、調光時において正常な放電灯Ｌａに対してエミレス状態ではなくとも異常と判定される可能性が生じる。また、調光レベルを設定可能な全範囲におけるランプ電圧Ｖｌａよりもしきい値を高く設定していると、１００％点灯時にエミレス状態になっているにもかかわらず、検出が遅れることになる。つまり、異常が生じてから異常と判断されるまでの時間が長くなり、素子へのストレスが増加した状態が継続することで、異常と検出する前に素子の破壊を招くことがある。
【００９８】
そこで、本実施形態では、設定値記憶部２５において調光レベルに応じたしきい値を設定しているのであって、図２３に示すランプ電圧Ｖｌａの曲線に沿ったしきい値を設定することにより、各調光レベルで適切なしきい値とすることができ、調光レベルが変わっても回路異常に対する保護を精度よく行うことができる。また、ストレスに対する余裕度を大きくとる必要がないから、高耐圧の素子を用いることなく、低コストで提供することが可能になる。他の構成および動作は実施形態８と同様である。
【００９９】
（実施形態１０）
本実施形態は、図２４に示すように、基本的には図２０に示した実施形態８の構成と同様のものであって、ランプ電圧Ｖｌａを直接検出するのではなく、直流カット用のコンデンサＣ０の位置を変更するとともに、コンデンサＣ０の両端電圧を検出手段９″により検出している。検出手段９″の出力はＡＤ変換器１０によりデジタル値に変換され、マイコン２０に入力される。コンデンサＣ０は、実施形態８ではスイッチング素子Ｑ１，Ｑ２の接続点とインダクタＬ１との間に接続しているが、本実施形態ではスイッチング素子Ｑ２の低電位側の一端（回路グランド）と放電灯Ｌａの一端との間に接続してある。また、マイコン２０において基準値の上下にしきい値を設定してある。すなわち、ＡＤ変換器１０の出力であるデジタル値が、上しきい値を超えたときと、下しきい値を下回ったときとのいずれも異常と判断するものである。言い換えると、正常範囲に上限値と下限値とが設定され、検出手段９″により検出されるコンデンサＣ０の両端電圧Ｖｃ０に相当する電圧Ｖｙが上限値と下限値との範囲を逸脱すると異常と判断するのである。
【０１００】
検出手段９″は、図２４に示すように、コンデンサＣ０の両端電圧を分圧する抵抗Ｒａ１，Ｒａ２を備え、抵抗Ｒａ１，Ｒａ２の接続点と電源ＶＤＤとの間に挿入した抵抗Ｒａ３を備えている。エミレス状態においては、コンデンサＣ０の両端電圧Ｖｃ０が増加もしくは減少するから、上述のようにマイコン２０に上限値と下限値とを設定して異常の有無を判定することにより、エミレス状態を検出することが可能になる。ここに、コンデンサＣ０の両端電圧Ｖｃ０を用いてエミレス状態を判定する場合には、上述のように２段階のしきい値が必要であって、アナログ回路を用いて判定しようとすれば、２個のコンパレータを必要とするが、本実施形態のようにマイコン２０を用いることによってコンパレータが不要であり、結果的に部品数を低減することができる。
【０１０１】
なお、コンデンサＣ０の位置は図２４に示す位置ではなくともエミレス状態の検出に用いることが可能である。また、コンデンサＣ０の両端電圧Ｖｃ０は放電灯Ｌａのエミレス状態において正負両極性になることがあるが、本実施形態では図２５に示すように、検出手段９″に抵抗Ｒａ３を設けることによって、直流バイアスを与えているから、検出手段９″の出力電圧の極性を正に保つことができる。他の構成および動作は実施形態８と同様である。
【０１０２】
（実施形態１１）
本実施形態は、図２６に示すように、図１４に示した実施形態４の構成に、交流電源１の電圧波形のゼロクロス点を検出する電源同期信号検出手段１６を付加したものである。すなわち、電源同期信号検出手段１６は、図２７（ａ）に示すような交流電源１の電圧波形におけるゼロクロス点に対応して、図２７（ｂ）に示すようなパルス状の電源同期信号を生成する。したがって、電源同期信号の発生周期Ｔは電源電圧の半周期に一致する。電源同期信号検出手段１６から出力される電源同期信号はマイコン２０に入力される。
【０１０３】
本実施形態では、検出手段１４で検出されるチョッパ回路３の出力電圧と、検出手段１５で検出されるランプ出力（ランプ電流）との少なくとも一方を、電源同期信号検出手段２６からマイコン２０に入力される電源同期信号の周期の略１／２ｎ（ｎ＝１，２，３，……）の周期でＡＤ変換器１６，１７からデジタル値として読み込み、検出手段１４を通して入力されたデジタル値はチョッパ回路３の出力電圧に対する設定値との差分を演算し、検出手段１５を通して入力されたデジタル値はランプ出力に対する設定値との差分を演算する。求めた差分値は、電源同期信号の周期で合計値を求め、この合計値に対して適宜の関数を適用してチョッパ回路３の出力電圧（スイッチング素子Ｑ３のオンデューティ）ないしインバータ回路４の動作周波数を決定する。
【０１０４】
具体的には、以下のようにして、チョッパ回路３の出力電圧オンデューティないしインバータ回路４の動作周波数を決定する。ただし、以下では、検出手段１４により検出したチョッパ回路３の出力電圧に基づいて、チョッパ回路３のスイッチング素子Ｑ３のオンデューティを制御する場合について説明する。いま、適宜の調光レベルにおいて、チョッパ回路３のスイッチング素子Ｑ３のオン期間の基準値をＴｏｎ０とし、補正後のオン時間をＴｏｎとし、それぞれに対応してＡＤ変換器１６から出力されるデジタル値をＤｏｎ０，Ｄｏｎ、マイコン２０が出力可能な信号の分解能をαとする。したがって、Ｔｏｎ０＝Ｄｏｎ０×α、Ｔｏｎ＝Ｄｏｎ×αになる。さらに、この調光レベルにおけるチョッパ回路３の出力電圧に対応する設定値をＶＡ（デジタル値）、ＡＤ変換器１６から出力されるデジタル値をＶ１とする。
【０１０５】
図２９に示すように、まずカウンタｊを０に初期化し（Ｓ１）、次に電源同期信号検出手段２６から出力される電源同期信号の周期Ｔに対して、略１／２ｎ（ｎ＝１，２，３，……）の周期でＡＤ変換器１６を通してチョッパ回路３の出力電圧Ｖ１をマイコン２０に読み込む（Ｓ２）。チョッパ回路３の出力電圧Ｖ１について、まず設定値ＶＡとの差分δＶ（＝ＶＡ−Ｖ１）が求められる（Ｓ３）。次に、周期Ｔにおいて２ｎ回分の差分δＶを合計し、差分の合計値ΔＶ（＝ΣδＶ）を求める（Ｓ４，Ｓ５）。次に、原点を対称とする図２８のような適宜の関数Ｇ（ｘ）に合計値ΔＶを代入し、チョッパ回路３に設けたスイッチング素子Ｑ３のオン時間の補正値ＤＡｉ（ｉ＝１，２，３，……）を求める（ＤＡｉ＝Ｇ（△Ｖ））（Ｓ６）。ここにおいて、添字ｉはそれぞれのタイミングで求めた補正値ＤＡｉを意味し、関数Ｇ（ｘ）は添字ｉに対しては不変である。上述のようにして補正値ＤＡｉが求められると、スイッチング素子Ｑ３のオン期間の基準値Ｔｏｎ０に補正値ＤＡｉを加算する（Ｓ７）。すなわち、Ｄｏｎ＝Ｄｏｎ０＋ΣＤＡｉとしてスイッチング素子Ｑ３のオン時間Ｄｏｎを決定する（Ｓ８）。
【０１０６】
図２９に示す動作を電源同期信号の発生毎（周期Ｔ毎）に繰り返すことによって、周期Ｔごとにチョッパ回路３のスイッチング素子Ｑ３のオン時間Ｔｏｎを更新する。このようにして、最終的にＤＡｉ＝０、すなわちＶＡ＝Ｖ１になると動作が安定する。このようにして設定値ＶＡを目標値とするフィードバック制御が可能となり、チョッパ回路３の出力電圧を安定化することが可能になる。結果的に、ランプ出力の安定化が図れる。また、チョッパ回路３のコンデンサＣ３の容量は有限であり、コンデンサＣ３の両端電圧は交流電源１の電圧周期に対して半周期Ｔのリップルを含んでいるが、周期Ｔにおいて偶数回の略等間隔でチョッパ回路３の出力電圧をマイコン２０に取り込み、その合計値に基づいてスイッチング素子Ｑ３のオン時間Ｔｏｎを求める演算を行っているから、リップル成分の影響を除去することができ、チョッパ回路３の出力電圧の十分な安定化を図ることができる。
【０１０７】
本実施形態では、設定値ＶＡとチョッパ回路３の出力電圧Ｖ１の差分δＶを求めた後、周期Ｔにおいて２ｎ回の合計値ΔＶを求める例を示したが、設定値をＶＡ×ｎとし、チョッパ回路３の出力電圧Ｖ１を周期Ｔの間で２ｎ回合計した後に、設定値ＶＡ×ｎとの差分を求め、この差分を合計値ΔＶとしてもよい。また、差分δＶに関数Ｇ（ｘ）を適用し、周期Ｔの間でＧ（δＶ）の２ｎ回の合計値を求めることによって、補正値ＤＡｉを求めるようにしてもよい。さらに、周期Ｔの間の２ｎ回の合計値ではなく、２ｎ回の平均値を用いて後の処理を行うようにしてもよい。このように平均値を用いる場合には、ＡＤ変換器１６の読み込み周期を略Ｔ／２^ｎ （ｎ＝１，２，３，……）としておけば、ｎビットシフトで平均値を求めることができるから、計算処理が簡単になり計算時間の短縮化を図ることができる。
【０１０８】
また、本実施形態では、ＡＤ変換器１６の読み込み周期を略Ｔ／２ｎ（ｎ＝１，２，３，……）としているが、周期Ｔの前半部分（１〜ｎ番目）と後半部分（ｎ＋１〜２ｎ番目）とが同じ時間間隔パターンであればよい。たとえばｎ＝４として、周期Ｔで８点読み込むものとし、基本的な読み込み周期を「５」とし、ＡＤ変換器１６にデータが入力される時間間隔を、［５，５，６，５，５，５，６，５］、あるいは［５，６，４，５，５，６，４，５］などとしてもよい。ここに、［］内の各数字はＡＤ変換器１６が値を読み込んでから次に読み込むまでの時間間隔を表している。
【０１０９】
さらに本実施形態では、チョッパ回路３の出力電圧を検出してチョッパ回路３スイッチング素子Ｑ３のオン時間Ｔｏｎを設定する例を示しているが、ランプ出力（ランプ電流）を検出してインバータ回路４の動作周波数を制御したり、チョッパ回路３の出力電圧を検出してインバータ回路４の動作周波数を制御したり、ランプ出力を検出してチョッパ回路３のスイッチング素子Ｑ３のオン時間Ｔｏｎを制御したりする場合にも、同様の技術思想を適用することができる。
【０１１０】
上述した関数Ｇ（ｘ）以外の関数Ｇ（ｘ）の設定例を図３０ないし図３４に示す。図３０に示す関数Ｇ（ｘ）は一次関数で定義したものであって、マイコン２０内にテーブルではなく数式の形で定義してある。このようにマイコン２０において数式で関数Ｇ（ｘ）を定義すれば記憶容量を低減することができる。
【０１１１】
図３１に示す例は、関数Ｇ（ｘ）において、補正値ＤＡｉの絶対値に制限を設けたものであって、たとえば、図３０に示した一次関数で定義される関数Ｇ（ｘ）において、補正値ＤＡｉに上限値と下限値とを規定するのである。補正値ＤＡｉに制限を加えることによって、チョッパ回路３の出力電圧Ｖ１と設定値ＶＡとの差分δＶが大きすぎるような場合や、負荷の急激な変動などによって出力電圧Ｖ１が設定値ＶＡから大きくずれるような場合に、補正値ＤＡｉが極端に大きくなってチョッパ回路３の動作が不安全な領域に入るのを防止することができる。
【０１１２】
図３２に示す例は、関数Ｇ（ｘ）において、合計値ΔＶの原点付近における所定の範囲で、補正値ＤＡｉを略０に設定したものである。また、それ以外の範囲では一次関数で定義してある。すなわち、最終的に動作が安定して原点付近の動作になった後に、ＡＤ変換器１６から出力されるデジタル値が外乱ノイズなどによってずれを生じることがあるから、このようなずれの影響を防止するために、不感領域を設けているのである。すなわち、関数Ｇ（ｘ）に不感領域を設けておくことで、微小な外乱ノイズなどの影響を抑制することが可能になる。
【０１１３】
図３３に示す例は、関数Ｇ（ｘ）を適宜の三次関数で定義したものである。一次関数の場合と同様にマイコン２０において関数Ｇ（ｘ）を数式で定義する。つまり、記憶容量の低減につながる。
【０１１４】
図３４に示す例は、関数Ｇ（ｘ）として、合計値ΔＶと補正値ＤＡｉとを対応付けたテーブルとしてあり、図３４に示す白丸の部位のデータをテーブルとして、関数Ｇ（ｘ）を定義している。このようなテーブルを用いることによって、図３１ないし図３３に示した非線型の関数や高次関数のような複雑な関係になる場合に、演算処理が簡単になり、処理能力が比較的低いマイコン２０であっても実用的な時間で演算処理が可能になる。
【０１１５】
なお、上述した各実施形態において、ＤＣ−ＤＣ変換回路として昇圧形のチョッパ回路３を用いているが、他の構成のチョッパ回路を用いたり、フライバック形などのＤＣ−ＤＣ変換回路を用いてもよい。要するに、出力電圧を外部から制御可能な構成であればよい。また、インバータ回路４として、直流カット用のコンデンサを備えるハーフブリッジ形のインバータ回路を例示したが、他の構成のインバータ回路であっても本発明の技術思想を適用可能であり、さらに、放電灯Ｌａは１灯に限らず複数灯であってもよい。
【０１１６】
【発明の効果】
本発明の構成によれば、１つのマイコンによりＤＣ−ＤＣ変換回路とインバータ回路と一括して制御することにより、部品点数の削減による低コスト化の実現が可能になる。しかも、マイコンに設けたテーブルによりＤＣ−ＤＣ変換回路の出力電圧とインバータ回路の動作周波数との組合せを制御することができるから、放電灯点灯時における、予熱、始動、定常点灯、調光などの各動作状態に合わせた適切な制御が可能になる。また、インバータ回路の動作周波数を高くして放電灯の光出力を低減する際にＤＣ−ＤＣ変換回路の出力電圧も低減するから、配光用点灯装置として好適な放電灯点灯装置を提供することができる。
【図面の簡単な説明】
【図１】実施形態１を示す回路図である。
【図２】実施形態２を示す回路図である。
【図３】実施形態２を示す動作説明図である。
【図４】実施形態３を示す動作説明図である。
【図５】実施形態３の要部ブロック図である。
【図６】実施形態３の動作説明図である。
【図７】実施形態３に用いる周波数テーブルの一例を示す図である。
【図８】実施形態３の動作説明図である。
【図９】実施形態３の動作説明図である。
【図１０】実施形態３に用いる周波数テーブルの他例を示す図である。
【図１１】実施形態３に用いる周波数テーブルのさらに他例を示す図である。
【図１２】実施形態３に用いる周波数テーブルの別例を示す図である。
【図１３】実施形態３に用いる周波数テーブルのさらに別例を示す図である。
【図１４】実施形態４を示す回路図である。
【図１５】実施形態４の動作説明図である。
【図１６】実施形態６の要部回路図である。
【図１７】実施形態６の動作説明図である。
【図１８】実施形態７を示す回路図である。
【図１９】実施形態７の動作説明図である。
【図２０】実施形態８を示す回路図である。
【図２１】実施形態８の動作説明図である。
【図２２】実施形態９を示す回路図である。
【図２３】実施形態９の動作説明図である。
【図２４】実施形態１０を示す回路図である。
【図２５】実施形態１０の要部回路図である。
【図２６】実施形態１１を示す回路図である。
【図２７】実施形態１１の動作説明図である。
【図２８】実施形態１１に用いる関数の一例を示す図である。
【図２９】実施形態１１の処理手順を示す動作説明図である。
【図３０】実施形態１１に用いる関数の他例を示す図である。
【図３１】実施形態１１に用いる関数のさらに他例を示す図である。
【図３２】実施形態１１に用いる関数のまた他例を示す図である。
【図３３】実施形態１１に用いる関数の別例を示す図である。
【図３４】実施形態１１に用いる関数のさらに別例を示す図である。
【図３５】従来例を示すブロック図である。
【図３６】従来例の動作説明図である。
【図３７】他の従来例を示すブロック図である。
【図３８】他の従来例の動作説明図である。
【図３９】別の従来例を示すブロック図である。
【符号の説明】
１ 交流電源
２ 整流回路
３ チョッパ回路（ＤＣ−ＤＣ変換回路）
４ インバータ回路
９ ランプ電圧検出手段
９′ ランプ電圧検出手段
９″ 検出手段
１１ ワイヤレス受信部
１４ 検出手段
１５ 検出手段
２０ マイコン
２１ 調光信号抽出手段
２２ 変換テーブル
２３ 出力パルス生成手段
２４ ＰＷＭ出力手段
２５ 設定値記憶手段
Ｃ１ コンデンサ
Ｌ１ インダクタ
Ｌａ 放電灯
Ｑ１〜Ｑ３ スイッチング素子[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a discharge lamp lighting device that applies a high frequency voltage to a discharge lamp using an inverter circuit.
[0002]
[Prior art]
As shown in FIG. 35, this type of conventional discharge lamp lighting device includes an inverter circuit 4 for converting a DC voltage to a high-frequency voltage, and rectifies the AC power supply 1 as a power supply of the inverter circuit 4. A configuration is known in which a chopper circuit (boost circuit) 3 that boosts the output voltage of the rectifier circuit 2 is provided (for example, see Patent Document 1). The high-frequency voltage output from the inverter circuit 4 is applied to a series resonance circuit composed of an inductor L1 and a capacitor C1, and a preheated discharge lamp La such as a fluorescent lamp is used to reduce the current flowing through the capacitor C1 to a filament of the discharge lamp La. Is connected in parallel with the capacitor C1 so as to obtain the preheating current. That is, the output terminal of the inverter circuit 4 is connected between one end on the power supply side of both filaments of the discharge lamp La via the inductor L1, and the capacitor C1 is connected between one end on the non-power supply side of both filaments of the discharge lamp La. .
[0003]
Each of the chopper circuit 3 and the inverter circuit 4 includes a switching element, and the switching frequency of the switching element provided in the inverter circuit 4 is controlled by an inverter control circuit (oscillation frequency control circuit) 5 so that the inverter circuit 4 supplies the discharge lamp La. The supplied power is controlled, and the output voltage of the chopper circuit 3 is controlled by controlling the switching frequency of a switching element provided in the chopper circuit 3 by a chopper control circuit (boosted voltage control circuit) 6.
[0004]
In the technique described in Patent Document 1, the chopper control circuit 6 is linked to the inverter control circuit 5 and increases the operating frequency of the inverter circuit 5 (the switching frequency of the switching element provided in the inverter circuit 4) to increase the discharge lamp. When the power supplied to La is reduced and the dimming is deepened, the chopper control circuit reduces the output voltage of the chopper circuit 3 in order to suppress an increase in the current flowing through the capacitor C1 (that is, the current flowing through the filament). 6 is operating. That is, as shown in FIG. 36, as the oscillation frequency of the inverter control circuit 5 increases (the switching frequency of the inverter circuit 4 increases), the operating frequency of the inverter circuit 4 and the chopper The relationship with the output voltage of the circuit 5 is set.
[0005]
As another configuration example of the discharge lamp lighting device, as shown in FIG. 37, a remote control-controlled discharge lamp lighting device that controls the lighting state of the discharge lamp La by a wireless signal using infrared rays as a medium is known. That is, a configuration for processing a wireless signal is added to the configuration shown in FIG. 35. In the illustrated example, the control signal output from the inverter control circuit 5 is a voltage that can control a switching element provided in the inverter circuit 4. FIG. 2 shows a configuration in which a driver circuit 7 including a level shift circuit for converting into a signal is provided between the inverter control circuit 5 and the inverter circuit 4.
[0006]
As a configuration for processing a wireless signal, a wireless receiving unit 11 for receiving a wireless signal using infrared rays from a separately provided remote control transmitter as a medium, and a header and a trailer included in the wireless signal received by the wireless receiving unit 11 are removed. A signal processing unit 12 including a microcomputer for extracting a control pulse signal from the microcomputer; and a pulse width-voltage conversion unit 13 for converting the pulse signal output from the signal processing unit 12 into a voltage. The voltage output from the pulse width-voltage converter 13 is input to the inverter control circuit 5, and the inverter control circuit 5 changes the operation frequency of the inverter circuit 4 according to the input voltage.
[0007]
This will be described more specifically. FIG. 38A shows a pulse signal output from the signal processing unit 12, and this pulse signal is a signal in which power supplied to the discharge lamp La (light control amount) is associated with a pulse width. In the periods t0 to t1 in FIG. 38, the dimming is shallower (the supply power is large and the light output is large) than the periods t2 to t3. That is, in order to increase the power supplied to the discharge lamp La, the ON period (H-level period) of the pulse signal included in the wireless signal is increased (the frequency is constant). As shown in FIG. 38B, the pulse width-voltage converter 13 is configured such that the output voltage decreases as the ON period of the input pulse signal increases. Further, as shown in FIG. 38C, the inverter control circuit 5 is configured such that the lower the input voltage from the pulse width-voltage converter 13 is, the lower the oscillation frequency (the operating frequency of the inverter circuit 4) is. The power supplied to the discharge lamp La increases as the ON period of the pulse signal increases (the ON duty increases). Further, since the inverter control circuit 5 and the chopper control circuit 6 are linked, when the operating frequency of the inverter circuit 4 increases, the output voltage of the chopper circuit 3 decreases. Although the clock signal for operating the signal processing unit 12 is different from and not synchronized with the oscillation frequency of the inverter control circuit 5, since the pulse signal is converted into the DC voltage as described above, the signal processing unit 12 and the inverter control circuit 5 can be operated individually.
[0008]
As still another example of the discharge lamp lighting device, a configuration shown in FIG. 39 has been proposed (for example, see Patent Document 2). In the illustrated example, the input power supply of the inverter circuit 4 is shown as a DC power supply DC, and the capacitor C1 is connected between one end of one filament on the non-power supply side and one end of the other filament on the power supply side. . Further, a single-ended half-bridge type is used as the inverter circuit 4, and therefore a DC cut capacitor C0 is added.
[0009]
In the configuration shown in FIG. 39, a modulation signal is input to an inverter control circuit (frequency determination circuit) 5 together with a dimming signal in order to change the light output of the discharge lamp La. The frequency-modulated signal whose frequency has been determined is modulated by a sinusoidal modulation signal. In this configuration, the operating frequency of the inverter circuit 4 is alternately changed between a high state and a low state, so that the current flowing through the discharge lamp La also changes with time due to the modulation signal. It is possible to keep the discharge lamp La lit without flicker.
[0010]
[Patent Document 1]
JP-A-5-258889
[Patent Document 2]
JP-A-7-130487
[0011]
[Problems to be solved by the invention]
By the way, in the configurations shown in FIGS. 35 and 37, the inverter control circuit 5 and the chopper control circuit 6 are linked, and the relationship between the operating frequency of the inverter circuit 4 and the output voltage of the chopper circuit 3 is associated one-to-one. Therefore, the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 cannot be independently controlled, and the output voltage of the chopper circuit 3 and the inverter circuit are adjusted in accordance with the lighting conditions of the discharge lamp La. However, there is a problem that it is not possible to finely control the operating frequency of 4 while cooperating. For example, by changing only the operating frequency of the inverter circuit 4 while keeping the output voltage of the chopper circuit 3 constant, it is not possible to perform control for changing the light control amount. Further, if the inverter control circuit 5 and the chopper control circuit 6 are configured as separate circuits, they are easily affected by noise, and it becomes difficult to control the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 with high accuracy.
[0012]
Further, in the configuration shown in FIG. 37, a configuration for processing a wireless signal is added, and after converting the on-duty of a pulse signal indicating a dimming level in the wireless signal into a DC voltage, the operating frequency of the inverter circuit 4 is changed. , A relatively large conversion error occurs due to the two conversions, and a difference easily occurs between the dimming level specified by the wireless signal transmitted from the remote control transmitter and the dimming level of the discharge lamp La. Further, since the number of components is increased by adding a configuration for processing a wireless signal, there is also a problem that a mounting space is increased and a cost is increased.
[0013]
In the configuration shown in FIG. 39, it is necessary to input a modulation signal in addition to the dimming signal to the inverter control circuit 5, so that there is a problem that the inverter control circuit 5 is easily affected by noise. In addition, since the inverter control circuit 5 needs a circuit that generates a modulated signal in accordance with the dimming signal and modulates the modulated signal with the modulation signal, the circuit configuration becomes complicated and the cost increases. Occurs.
[0014]
The present invention has been made in view of the above circumstances, and has as its object to simplify the circuit configuration while finely controlling the operation states of the chopper circuit and the inverter circuit according to the dimming level, thereby reducing noise. An object of the present invention is to provide a discharge lamp lighting device which is hardly affected by the influence of the discharge lamp and can make the mounting space relatively small.
[0015]
[Means for Solving the Problems]
The invention according to claim 1 is a DC-DC conversion circuit in which a DC output voltage is variable by controlling ON / OFF of a switching element, and an inverter circuit that converts a DC voltage output from the DC-DC conversion circuit into a high-frequency voltage. A resonance circuit provided in a path for supplying a high-frequency voltage output from the inverter circuit to the discharge lamp, and a microcomputer that collectively generates control signals for the output voltage of the DC-DC conversion circuit and the operating frequency of the inverter circuit. A table is set in the microcomputer so that the output voltage of the DC-DC conversion circuit is reduced and the operating frequency of the inverter circuit is increased at the time of dimming as compared with the time of steady lighting.
[0016]
According to this configuration, since the DC-DC conversion circuit and the inverter circuit are controlled collectively by one microcomputer, the cost can be reduced by reducing the number of components. In addition, since the combination of the output voltage of the DC-DC conversion circuit and the operating frequency of the inverter circuit can be controlled by a table provided in the microcomputer, the preheating, starting, steady lighting, dimming, etc., when the discharge lamp is lit. Appropriate control can be performed according to each operation state. In addition, when the operating frequency of the inverter circuit is increased to reduce the light output of the discharge lamp, the output voltage of the DC-DC conversion circuit is also reduced, so that a discharge lamp lighting device suitable as a light distribution lighting device is provided. Can be.
[0017]
According to a second aspect of the present invention, in the first aspect of the present invention, there is provided a wireless receiving unit for receiving a wireless signal from a remote control transmitter separately provided, wherein the microcomputer is configured to transmit a data bit string included in a wireless signal and the DC-DC conversion. A conversion table in which data for generating a control signal to be provided to each of the circuit and the inverter circuit are associated with each other; and output pulse generation means for generating the control signal from a clock signal based on data obtained from the conversion table. It is characterized by the following.
[0018]
According to this configuration, the operating frequency of the inverter circuit and the output voltage of the DC-DC conversion circuit corresponding to each dimming level of the wireless signal can be uniquely determined by digital processing. This control information can be directly reflected on the control of the operation state of the discharge lamp, and there is almost no error in the output voltage of the DC-DC conversion circuit and the operation frequency of the inverter circuit.
[0019]
According to a third aspect of the present invention, in the second aspect of the present invention, the microcomputer further includes a dimming signal extracting unit that extracts a data bit string to be compared with a conversion table from the pulse signal output from the wireless receiving unit. I do.
[0020]
According to this configuration, the dimming level transmitted from the remote control transmitter can be directly reflected in the control of the operation state of the discharge lamp, and almost no error occurs in the output voltage of the DC-DC conversion circuit and the operation frequency of the inverter circuit. It does not happen. In addition, since one microcomputer performs not only the DC-DC conversion circuit and the inverter circuit but also the reception processing of the wireless signal, the number of components can be reduced.
[0021]
According to a fourth aspect of the present invention, in the first aspect of the present invention, in the frequency table for determining the operating frequency of the inverter circuit in the conversion table, a gradient of a current-voltage characteristic of the discharge lamp in a negative characteristic region is maximum. The operating frequency of the dimming level deeper than the specified value near the point and the operating frequency of the dimming level shallower than the specified value are associated one-to-one, and the microcomputer controls the dimming level deeper than the specified value. Is selected, the two operating frequencies are periodically switched.
[0022]
According to this configuration, the operation frequency of the inverter circuit can be switched at the time of deep light control without requiring a complicated circuit configuration or complicated control, and countermeasures against the disappearance at the time of deep light control can be performed.
[0023]
According to a fifth aspect of the present invention, in the first aspect of the present invention, in the frequency table for determining the operating frequency of the inverter circuit in the conversion table, a gradient of a current-voltage characteristic of the discharge lamp in a negative characteristic region is maximum. All the operating frequencies of the dimming level deeper than the specified value near the point are associated with one operating frequency of the dimming level shallower than the specified value, and the microcomputer performs dimming deeper than the specified value. When a level is selected, an operating frequency of a dimming level deeper than the specified value and an operating frequency of a dimming level shallower than the specified value associated with the operating frequency are periodically switched. I do.
[0024]
According to this configuration, the operation frequency of the inverter circuit can be switched at the time of deep light control without requiring a complicated circuit configuration or complicated control, and countermeasures against the disappearance at the time of deep light control can be performed. In particular, when the operating frequency of the inverter circuit is switched at the time of deep dimming, one of the operating frequencies can be fixedly set, so that the control is simplified.
[0025]
According to a sixth aspect of the present invention, in the first aspect of the invention, the microcomputer changes at least one of a cycle for changing an operating frequency of the inverter circuit and a period for changing the operating frequency in accordance with a dimming level. And
[0026]
According to this configuration, at least one of the cycle in which the operating frequency is changed and the period in which the operating frequency is changed can be set in accordance with the dimming level. The discharge lamp can be turned on.
[0027]
According to a seventh aspect of the present invention, in the first aspect of the invention, the microcomputer associates the dimming level with a plurality of sets of the operating frequencies of the inverter circuits and associates the operating frequencies forming the set with the selected dimming level. It is characterized in that it is selected cyclically.
[0028]
According to this configuration, the switching frequency of the operating frequency can be accurately managed, and the operating frequency can be varied in various ways depending on the combination of the operating frequencies.
[0029]
According to an eighth aspect of the present invention, in the first aspect of the present invention, a detecting means for detecting the output of the discharge lamp and a set value storage means for associating a dimming level with a set value of the output of the discharge lamp are added. The microcomputer alternately sets an operating frequency of the inverter circuit to a first operating frequency for lighting the discharge lamp at a selected dimming level and a second operating frequency for preventing the discharge lamp from turning off. A switching function, and a function of updating the first and second operating frequencies of the inverter circuit so that the output of the discharge lamp detected by the detection means approaches the set value in the set value storage means. It is characterized in that the cycle for updating the first and second operating frequencies is set longer than the cycle for alternately selecting the first operating frequency and the second operating frequency.
[0030]
According to this configuration, even if a relatively low-performance and inexpensive microcomputer is used, the lamp output can be stabilized while preventing the discharge lamp from going out, and stable lighting during deep dimming can be expected.
[0031]
According to a ninth aspect of the present invention, the timing for switching the operating frequency of the inverter circuit by the microcomputer is given by a trigger from an external circuit provided separately from the microcomputer. I do.
[0032]
According to this configuration, the switching timing of the conversion table provided in the microcomputer is designated by an external circuit, thereby enabling stable lighting during deep light control.
[0033]
According to a tenth aspect of the present invention, in the first aspect, a lamp voltage detecting means for detecting a lamp voltage of the discharge lamp and inverting the lamp voltage when the lamp voltage exceeds a set threshold is added, The operation of the DC-DC converter and the inverter circuit is stopped in response to an interrupt due to inversion of the output of the detection means.
[0034]
According to this configuration, the circuit can be protected against the abnormality by stopping the operation in response to the abnormal state in which the lamp voltage or the like rapidly changes.
[0035]
According to an eleventh aspect of the present invention, in the first aspect of the present invention, the microcomputer further comprises a lamp voltage detecting and detecting means for outputting a DC voltage reflecting the lamp voltage of the discharge lamp, and the microcomputer has a normal range for an output value of the detecting means. The operation of the DC-DC conversion circuit and the inverter circuit is stopped when the value deviates from one of the upper limit value and the lower limit value.
[0036]
According to this configuration, it is possible to accurately protect the circuit against the abnormality even when the lamp voltage gradually changes.
[0037]
According to a twelfth aspect of the present invention, in accordance with the eleventh aspect of the present invention, the apparatus according to the eleventh aspect further comprises a set value storage unit that associates the upper limit value and the lower limit value with each light control level.
[0038]
According to this configuration, since an appropriate threshold value can be set according to the dimming level, circuit protection against abnormalities can be accurately performed over the entire dimming range.
[0039]
According to a thirteenth aspect, in the first aspect, a first detecting means for detecting an output of the discharge lamp, a second detecting means for detecting an output voltage of the DC-DC conversion circuit, Setting value storage means for associating a set value of the output of the discharge lamp with a level, wherein the microcomputer stores the set value stored in the set value storage means and the value detected by the first or second detection means. Of the difference, calculate a total value or an average value of the differences a plurality of times, and use the correction value obtained by substituting the total value or the average value into a function to obtain a switching element provided in the DC-DC conversion circuit. And at least one of the on-time and the operating frequency of the inverter circuit is corrected, and the correction is repeated in a cycle for obtaining a total value or an average value of the differences.
[0040]
According to this configuration, feedback control can be performed while using a microcomputer having a relatively low processing capability, and the output of the discharge lamp can be stabilized.
[0041]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
As shown in FIG. 1, the present embodiment includes a rectifier circuit 2 composed of a diode bridge for full-wave rectifying an AC power supply 1 such as a commercial power supply, and the output of the rectifier circuit 2 is a boost type as a DC-DC conversion circuit. After the voltage is boosted by the chopper circuit 3, the DC voltage output from the chopper circuit 3 is converted into a high frequency voltage by the inverter circuit 4, and the high frequency voltage output from the inverter circuit 4 is converted into a resonance circuit including the inductor L1 and the capacitor C1. Through a discharge lamp La. That is, the circuit configuration of the basic part is the same as the conventional configuration shown in FIG.
[0042]
The chopper circuit 3 includes a capacitor C2 connected between the DC output terminals of the rectifier circuit 2, and an inductor L3 connected between the DC output terminals of the rectifier circuit 2 and a switching element Q3 (in the illustrated example, a MOSFET is used). It comprises a circuit and a series circuit of a diode D3 and a capacitor C3 connected between both ends of the switching element Q3. The chopper circuit 3 has a well-known configuration as a step-up chopper circuit, and discharges energy accumulated in the inductor L3 during the ON period of the switching element Q3 to the capacitor C3 through the diode D3 during the OFF period of the switching element Q3. Thus, the voltage between both ends of the capacitor C3 is boosted from the peak value of the output voltage of the rectifier circuit 2. Further, as is apparent from the operation of the chopper circuit 3, since the current flows through the inductor L3 during both the ON period and the OFF period of the switching element Q3, the current flowing from the AC power supply 1 into the rectifier circuit 2 is substantially reduced. There is no idle period, so that the input current distortion is small, and the phase of the input current substantially matches the voltage phase of the AC power supply 1, so that a high power factor can be obtained. That is, the chopper circuit 3 also functions as a power factor improvement circuit.
[0043]
The inverter circuit 4 is composed of a series circuit of a pair of switching elements Q1 and Q2 (a MOSFET is used in the illustrated example) connected between both ends of a capacitor C3. A series circuit of a capacitor C0, an inductor L1, and a capacitor C1 is connected, and a discharge lamp La is connected in parallel to the capacitor C1. That is, the inverter circuit 4 is a half-bridge type, and the switching elements Q1 and Q2 are alternately turned on and off, so that the capacitor C3-switching element Q1-capacitor C0-inductor L1-capacitor C1 during the ON period of the switching element Q1. Current flows through the path of the discharge lamp La and the capacitor C3, and during the ON period of the switching element Q2, the current flows through the path of the capacitor C0, the switching element Q2, the capacitor C1, and the discharge lamp La, the inductor L1, and the capacitor C0. It is configured.
[0044]
In this embodiment, a preheating transformer T1 is provided to preheat the filament of the discharge lamp La. The primary winding of the preheating transformer T1 is connected in series with the capacitor C4, and a series circuit of the primary winding and the capacitor C4 is provided. Is connected between both ends of the switching element Q2 via the capacitor C0. The preheating transformer T1 has two secondary windings, and each secondary winding is connected to each filament of the discharge lamp La. Therefore, by setting the operating frequency of the inverter circuit 4 appropriately (set to a relatively high frequency), a relatively large current can flow through the primary winding of the preheating transformer T1 through the capacitor C4. Since a relatively large current flows through the filament of the electric lamp La, the discharge lamp La can be preheated. Further, when the operating frequency of the inverter circuit 4 is reduced, the impedance of the capacitor C5 increases, the current flowing through the primary winding of the preheating transformer T1 decreases, and the current flowing through the filament of the discharge lamp La can be reduced. At this time, if a relatively high voltage is applied to the discharge lamp La by resonance between the inductor L1 and the capacitor C1, the discharge lamp La can be started, and thereafter, the lighting of the discharge lamp La can be maintained. Can be.
[0045]
By the way, the present embodiment is characterized in that the on / off of the switching elements Q1 to Q3 of the chopper circuit 3 and the inverter circuit 4 is controlled by using a microcomputer (hereinafter abbreviated as "microcomputer") 20. . That is, by executing an appropriate program by the microcomputer, the operation (output voltage) of the chopper circuit 3 and the operation (operating frequency) of the inverter circuit 4 are controlled in various combinations according to the operation state of the discharge lamp La. It is possible. To enable various combinations of the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4, the microcomputer 20 stores a table in which the output voltage of the chopper circuit and the operating frequency of the inverter circuit 4 are associated with each other. Is provided. Specifically, a combination of the output voltage of the chopper circuit and the operating frequency of the inverter circuit 4 is set in accordance with each operation mode of preheating, starting, steady lighting, and dimming. It looks like 1.
[0046]
[Table 1]

[0047]
In the illustrated example, each operation mode of preheating, starting, and steady lighting is switched over according to time. That is, when the power is turned on, the microcomputer 20 operates the chopper circuit 3 and the inverter circuit 4 in the preheating mode, so that a preheating current flows through the filament of the discharge lamp La, and the microcomputer 20 switches to the starting mode 1 s after the power is turned on. In the starting mode, the voltage applied to the discharge lamp La is increased to turn on the discharge lamp La, and thereafter, the voltage applied to the discharge lamp La is reduced, and the mode shifts to the steady lighting mode in which the current flowing through the discharge lamp La is increased. is there. When the discharge lamp La is lit in the dimming mode, the operating frequency of the inverter circuit 4 is increased from that at the time of steady lighting, so that the current flowing through the inductor L1 to the discharge lamp La is reduced. Reduce the output voltage from that at steady lighting.
[0048]
As described above, the operation of the chopper circuit 3 and the inverter circuit 4 is controlled by using the microcomputer 20 and the relationship between the two is set by the table. The operation is not fixedly set to a one-to-one relationship with only one relationship, but can be set in any combination, and as a result, fine control according to the operation state of the discharge lamp La becomes possible. . Moreover, since the chopper circuit 3 and the inverter circuit 4 are directly controlled by the output of the microcomputer 20, the number of parts is smaller than that of the conventional configuration which requires the chopper control circuit 6 and the inverter control circuit 5 separately as in the conventional configuration. And the mounting operation is facilitated, and the mounting space is reduced by reducing the number of components.
[0049]
(Embodiment 2)
In the present embodiment, a configuration for monitoring the voltage applied to the discharge lamp La and the current flowing through the discharge lamp La is added to the configuration of the first embodiment shown in FIG. That is, a series circuit of two resistors R1 and R2 is connected between both ends of the capacitor C3, and the voltage between both ends of the capacitor C3, which is the output voltage of the chopper circuit 3, is divided by the resistors R1 and R2. Input to the provided port. The voltage divided by the resistors R1 and R2 becomes a voltage proportional to the voltage applied to the discharge lamp La. In addition, a current transformer T2 having a primary winding inserted between the low-potential end of the primary winding of the preheating transformer T1 and the discharge lamp La is provided to detect a lamp current. By inputting the next output to a port provided in the microcomputer 20, the microcomputer 20 takes in the lamp current. As described later, the microcomputer 20 controls the switching element Q3 of the chopper circuit 3 so that the voltage divided by the resistors R1 and R2 is maintained at the target value set by the table, and the secondary output of the current transformer T2 is controlled. The switching elements Q1 and Q2 of the inverter circuit 4 are controlled so as to be maintained at the target value set by the table.
[0050]
By the way, in the present embodiment, it is assumed that the current-voltage characteristics (hereinafter, referred to as lamp characteristics) of the discharge lamp La are as shown by a curve indicated by A in FIG. FIG. 3 shows a case where the constants of the chopper circuit 3 and the inverter circuit 4 (particularly, the inductor L1 and the capacitors C1 and C5) are fixed values and the combination of the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 is variously changed. 3 shows an operation example. That is, in FIG. 3, four types of combinations of the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 are shown, and are distinguished by reference numerals B1 to B4. When a set of the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 is expressed as (output voltage, operating frequency), the curve B1 is (180 V, 55 kHz), the curve B2 is (280 V, 107 kHz), and the curve B3 is (180 V, 97 kHz) and curve B4 correspond to (280 V, 55 kHz). Hereinafter, a comprehensive current-voltage characteristic based on a combination of the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 is referred to as a lighting circuit characteristic.
[0051]
The rated lamp current of the illustrated discharge lamp La is around 400 mA (here, 430 mA). When the lighting circuit characteristic is substantially orthogonal to the lamp characteristic near the rated lamp current, the reactive current is large and the efficiency is reduced. Will be. Therefore, it is desirable to minimize the angle at which the lamp characteristics and the lighting circuit characteristics intersect. However, if they do not cross, the discharge lamp La will go out. In the illustrated example, a curve B1 indicates a lighting circuit characteristic in which an intersection satisfying a lamp current of 430 mA cannot be obtained. On the other hand, in the dimming state, since the slope of the lamp characteristics becomes large, if the slope of the lighting circuit characteristics is not increased, the light-off occurs, and the intersection of the lamp characteristics and the lighting circuit characteristics is adjacent to two places as shown by the curve B2. When formed, the behavior of the discharge lamp La becomes unstable, causing a so-called jump phenomenon, and flickering occurs.
[0052]
That is, if both the output voltage of the chopper circuit 3 and the output of the operating frequency of the inverter circuit 4 are changed according to the dimming level as shown by the curves B3 and B4, efficient operation can be performed at the time of rated lighting. In addition, light can be adjusted to a low luminous flux. However, if the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 are controlled appropriately using individual components according to the dimming level, the circuit configuration becomes complicated and the circuit scale becomes large. Occurs. Also, as described as the conventional configuration, it is difficult to perform appropriate control with a small-scale circuit configuration.
[0053]
Therefore, in the present embodiment, the microcomputer 20 is used, and by controlling both the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 according to the dimming level, a circuit having a complicated configuration can be realized. Appropriate control can be performed without using or increasing the circuit scale. Here, Table 2 shows an example of a table provided in the microcomputer 20 so that the discharge lamp La is appropriately turned on. Thus, the dimming can be performed down to a low output with a simple configuration only by providing the microcomputer 20 with a table. Other configurations and operations are the same as those of the first embodiment.
[0054]
[Table 2]

[0055]
(Embodiment 3)
As shown in FIG. 4, this embodiment basically has the same configuration as that of the first embodiment shown in FIG. 1 except that a wireless reception for receiving a wireless signal using infrared rays transmitted from a remote control transmitter as a transmission medium is used. The part 11 is added. The wireless receiving unit 11 includes a light receiving element such as a photodiode, and a circuit unit that extracts a pulse signal corresponding to a wireless signal from an output of the light receiving element such as an amplifier circuit or a waveform shaping circuit. The pulse signal output from the receiving unit 11 is input to the microcomputer 20. A driver circuit 7 including a level shift circuit for converting a control signal output from the microcomputer 20 into a voltage that can control a switching element provided in the inverter circuit 4 is inserted between the microcomputer 20 and the inverter circuit 4. I have.
[0056]
The pulse signal output from the wireless receiving unit 11 is converted into a signal for controlling the chopper circuit 3 and the inverter circuit 4 inside the microcomputer 20. That is, the microcomputer 20 does not need the signal processing unit 12 and the pulse width-voltage conversion unit 13 (see FIG. 37) that are required in the conventional configuration, and the microcomputer 20 generates an analog signal such as a voltage signal. Instead, a signal for controlling the chopper circuit 3 and the inverter circuit 4 is directly generated from the pulse signal by digital processing. Here, when dimming, the operating frequency of the inverter circuit 4 is increased and the output voltage of the chopper circuit 3 is reduced.
[0057]
The operation of the present embodiment will be briefly described. As described above, the pulse signal corresponding to the wireless signal received by the wireless reception unit 11 is directly input to the microcomputer 20, the header and the trailer are removed inside the microcomputer 20, and the pulse signal included in the wireless signal is controlled. Two types of control signals are generated from the pulse signal for use by dividing the clock signal of the microcomputer 20. One control signal is used for controlling the operating frequency of the inverter circuit 4, and the other control signal is used for controlling the output voltage of the chopper circuit 3. That is, two control signals used for the chopper circuit 3 and the inverter circuit 4 are generated using the wireless signal received from the remote control transmitter.
[0058]
Here, of the control pulse signal included in the wireless signal, the H-level period and the L-level period corresponding to the data portion corresponding to each dimming level are determined in advance, so that one pair of the wireless signal can be obtained. 1 allows the microcomputer 20 to generate a corresponding control signal. As a result, the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 can be uniquely determined in accordance with the dimming level instructed by the wireless signal, so that the dimming transmitted from the transmitter of the remote controller can be determined. The light level can be directly reflected on the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4, and little error occurs in the output voltage of the chopper circuit 3 and the output voltage of the inverter circuit 4.
[0059]
In this embodiment, means for correcting the variation in the constants of the components constituting the chopper circuit 3 and the inverter circuit 4 is not described. However, such variation in the constants is corrected by a variable resistor or the like. An adjusting element may be appropriately added to the chopper circuit 3 or the inverter circuit 4. By performing control by the microcomputer 20 after performing such an adjustment, it is possible to suppress variations among products.
[0060]
FIG. 5 is a block diagram illustrating functions of the microcomputer 20 according to the present embodiment. The microcomputer 20 is provided with a dimming signal extraction unit 21 to which a pulse signal from the wireless receiving unit 11 is input, and converts a data bit string (control pulse signal) corresponding to control information such as a dimming signal from the pulse signal. Pull out. This data bit string represents ON / OFF information or dimming level information specified by the remote control transmitter. The output of the dimming signal extraction means 21 is input to the conversion table 22. The conversion table 22 is composed of a ROM in which the data bit string extracted from the wireless signal is associated with the frequency division ratio of the clock signal of the microcomputer 20, and the data bit string extracted from the wireless signal is converted into parallel data or serial data. The frequency division ratio of the clock signal is obtained by collation with 22. Here, the conversion table 22 is provided with a duty table corresponding to the chopper circuit 3 and a frequency table corresponding to the inverter circuit 4. The division ratio determined by the conversion table 22 is input to the output pulse generation unit 23, and the output pulse generation unit 23 divides the clock signal according to the input division ratio. That is, the output pulse generating means 23 constitutes a counter or a timer, and generates a pulse signal having an H level period and an L level period of a control signal supplied to the chopper circuit 3 and the inverter circuit 4, respectively. That is, the frequency and the on-duty of the control signal provided to the chopper circuit 3 and the inverter circuit 4 are determined. Further, the pulse signal output from the output pulse generation means 23 is supplied to the chopper circuit 3 and the inverter circuit 4 as control signals via the PWM output means 24.
[0061]
The operation of generating a control signal, which is a PWM signal, from a clock signal in the output pulse generating means 23 and the PWM output means 24 will be briefly described with reference to FIG. Although the frequency of the clock signal shown in FIG. 6A is sufficiently shorter than the period of the PWM signal, FIG. 6 shows the frequency significantly longer than the actual period.
[0062]
In FIG. 6, the period t0 to t1 shows a case where the power supply to the discharge lamp La is larger than the period t2 to t3. At times t0 to t1, the output voltage of the chopper circuit 3 is determined by selecting data having an ON time of 2 clocks and an OFF time of 3 clocks from the duty table provided in the conversion table 22, and the conversion is performed. The operation frequency of the inverter circuit 4 is determined by selecting data whose frequency division ratio is ８ from the frequency table provided in the table 22. Similarly, from time t2 to time t3, from the duty table provided in the conversion table 22, data corresponding to one clock for the ON time and to three clocks for the OFF period are selected, and from the frequency table provided in the conversion table 22, Data having a division ratio of 1/4 is selected. However, actually, the clock frequency of the microcomputer 20 is 8 MHz or more, and the operating frequency of the inverter circuit 4 is set to around 50 kHz, so that the frequency division ratio is 1/160 or less.
[0063]
As described above, in the conversion table 22, the frequency division ratio corresponding to each of the chopper circuit 3 and the inverter circuit 4 is generated from one data bit string, so that the operation of the chopper circuit 3 and the inverter are performed in accordance with the contents of the conversion table 22. The operation of the circuit 4 can be arbitrarily set. Moreover, by using the conversion table 22, a control signal is generated by digital data based on the correspondence between the data bit string and the frequency division ratio without using an analog signal. It is possible to generate a control signal that does not occur.
[0064]
By the way, at a deep dimming level lower than the vicinity of the point where the slope of the current-voltage characteristic of the discharge lamp La in the negative characteristic region is maximum, the lighting state of the discharge lamp La becomes unstable and the discharge lamp La tends to extinguish. At the dimming level, control different from other dimming levels is required to maintain stable lighting of the discharge lamp La. In this embodiment, the discharge lamp La is kept stable at the deep dimming level by increasing the amplitude of the lamp current waveform at a constant cycle for a fixed period compared to other periods.
[0065]
Now, in the frequency table provided in the conversion table 22, it is assumed that the dimming levels X1 to Xn are set in association with the dimming levels 1 to n as shown in FIG. The division ratios X1 to Xn correspond to the operating frequencies f1 to fn of the inverter circuit 4. Further, when the dimming level is deeper than the specified value indicated by the dashed line D1 in FIG. 7, the control of the inverter circuit 4 is made different from that when the dimming level is shallower than the dashed line D1. In FIG. 7, the division ratios X1... When the dimming level is deeper than the dashed line D1 are associated one-to-one with the division ratios. Is indicated by an arrow. That is, since the inverter circuit 4 can change the lamp current of the discharge lamp La by changing the operating frequencies f1 to fn, the division ratio X1 at the deep dimming level and the dimming ratio at the shallow dimming level are obtained. When the division ratio X1 at a certain time is associated with the one-to-one correspondence and the division ratio X1 is selected at the time of the deep dimming level, the division ratio X1 at a constant period and for a predetermined period is selected. The frequency division ratio... Xn corresponding to is selected.
[0066]
For example, the division ratio X1 is associated with the division ratio Xn. When the dimming level is 1, the division ratio X1 (that is, the frequency f1) is selected. The ratio Xn (that is, the frequency fn) is selected so that the lamp current increases in a constant cycle at regular intervals. Here, a separate control table is required to associate the deep dimming level with the shallow dimming level, and when the deep dimming level is selected, the shallow dimming level corresponding to the dimming level is selected. From the conversion table 22, frequency division ratios corresponding to both dimming levels are output alternately. Assuming that the time for selecting the frequency division ratio X1 is T1 and the time for selecting the frequency division ratio Xn is T2 (<T1), as shown in FIG. 8, when the frequency f1 is selected as the operating frequency of the inverter circuit 4, The frequency fn is selected for a certain period (T1 + T2) and a certain time T2. By such control, the on / off of each of the switching elements Q1 and Q2 (see FIG. 1) provided in the inverter circuit 4 becomes as shown in FIGS. 9A and 9B. The frequency and amplitude of the lamp current waveform are modulated as shown in FIG. 9 (c), and the amplitude periodically increases. Instead of providing a control table, dimming levels 1 to n are represented by numerical values, and when a deep dimming level is selected with respect to the broken line D1, the sum of the dimming levels becomes, for example, (n + 1). Such a shallow light control level may be selected. If such selection rules are determined, the division ratios X1 and Xn are selected for the dimming level 1, and the division ratios X2 and X (n-1) are selected for the dimming level 2. You.
[0067]
In the example described above, a control table was required separately from the frequency table to periodically change the amplitude of the lamp current waveform at the deep dimming level. However, as shown in FIG. In the level, two kinds of frequency division ratios X1..., Y1. That is, the division ratios X1... And the division ratios Y1... Correspond one-to-one, and when the division ratio X1... Is selected, the operating frequency of the inverter circuit 4 increases and the lamp current decreases. Is selected so that the operating frequency of the inverter circuit 4 becomes lower and the lamp current becomes larger than when the corresponding division ratio X1 is selected. .. Are associated with the frequency division ratios Y1. However, the two division ratios X1..., Y1... Correspond to the dimming level only for dimming levels deeper than the broken line D1.
[0068]
In order to periodically change the amplitude of the lamp current waveform at the deep dimming level, the frequency table shown in FIG. Although the frequency division ratio of the shallow light control level is associated with Xn on a one-to-one basis, as shown in FIG. In short, all the division ratios X1... That are the deep dimming levels with respect to the broken line D1 are associated with one division ratio X (n−2) that is the shallow dimming level with respect to the broken line D1. With this determination, the selection of the frequency division ratio at the deep dimming level can be simplified.
[0069]
In the above-described example, the two types of frequency division ratios are alternately selected for the fixed time T1 and T2. Generally, the deeper the dimming level, the more easily the extinction occurs. Therefore, the deeper the dimming level, the greater the amplitude of the lamp current. May be shortened (T1 + T2), and the time T2 for increasing the amplitude of the lamp current may be increased. Here, at least one of the cycle (T1 + T2) and the time T2 may be controlled according to the dimming level. In order to perform such control, the conversion table 22 needs a control table in which the times T1 and T2 are associated with the dimming levels. Needless to say, even in the range of the dimming level for which the countermeasure against extinction is required, the likelihood of occurrence of the extinction is different. Therefore, it is necessary to select the period (T1 + T2) and the time T2 according to the dimming level. .
[0070]
As a frequency table, as shown as a conceptual diagram in FIG. 12, three or more division ratios A to E may be associated with each dimming level 1 to n, respectively. In the illustrated example, one of the dimming levels 1 to n is associated with a set of five division ratios A to E, and the division ratios A to E are cyclically selected at predetermined time intervals. It is to be done. For example, at a deep dimming level 1 where a countermeasure against extinction is required, the basic frequency division ratio A with respect to the dimming level 1 and the lamp current become larger than the frequency division ratio A (the operating frequency of the inverter circuit 4 decreases ) Using the frequency division ratio B, the frequency division ratio B is selected once while the frequency division ratio A is selected four times. Such processing makes it possible to periodically increase the lamp current. Further, for a shallow dimming level in which it is not necessary to change the lamp current periodically, one division ratio E may be set, and the division ratio E may be selected in all five selections. By such processing, it is possible to cope with the deep light control level and the shallow light control level by the same processing only by setting the contents of the frequency table. In the illustrated example, two types of division ratios A to D are associated with the broken line D1 at the deep dimming level, but three or more types of division ratios may be associated with each other. . Further, although five frequency division ratios are associated with each of the dimming levels 1 to n, the number of frequency division ratios to be associated can be appropriately selected. By using such a frequency table, the accuracy of the cycle for changing the operating frequency of the inverter circuit 4 can be increased, and the lamp current waveform can be varied in various ways by appropriately setting the combination of the dividing ratios. It becomes possible.
[0071]
In the frequency table shown in FIG. 12, a plurality of frequency division ratios are associated with one light control level even if the light control level is a shallow light control level with respect to the broken line D1, but as shown in FIG. At the light level, only one division ratio may be associated. With such a setting, it is possible to reduce the storage capacity of the frequency table as compared with the frequency table shown in FIG.
[0072]
In the above example, the frequency division ratio in the frequency table is exemplified as controlling only the operating frequency of the inverter circuit 4. However, the duty table for controlling the operation of the chopper circuit 3 in the conversion table may be set in the same manner. It is possible.
[0073]
(Embodiment 4)
As shown in FIG. 14, this embodiment has basically the same circuit configuration as that of the second embodiment, and members denoted by the same reference numerals as those in FIG. 2 have the same functions. However, the circuit for preheating is omitted in the figure. The detecting means 14 detects the output voltage of the chopper circuit 3 and has a function equivalent to the resistors R1 and R2 in the second embodiment. The detecting means 15 has a function of detecting the lamp current of the discharge lamp La. And has a function equivalent to the current transformer T2 in the second embodiment. The outputs of the detection means 14 and 15 are input to the microcomputer 20 via the AD converters 16 and 17, respectively. The control signal output from the microcomputer 20 is supplied to the switching elements Q1 and Q2 of the inverter circuit 4 via the driver 7 and to the switching element Q3 of the chopper circuit 3 via the driver 8. Further, the microcomputer 20 is provided with a setting value storage unit 25 composed of a memory as described later.
[0074]
In the present embodiment, the operating frequency of the inverter circuit 4 is changed for an appropriate time at regular intervals. Here, the lamp current detected by the detection means 15 is converted into a digital value by the AD converter 17 and then input to the microcomputer 20 to obtain a difference from the set value in the set value storage means 25. That is, in the set value storage unit 25, the dimming level is associated with the set value of the output (lamp current) of the discharge lamp La. The microcomputer 20 changes at least one of the on-duty and the operating frequency of the switching element Q3 of the chopper circuit 3 so as to reduce the difference, and performs feedback control so that the lamp current of the discharge lamp La is maintained at the set value. I do. However, the cycle for changing the operation of the switching element Q3 by the feedback control is set longer than the cycle for changing the operation frequency in the inverter circuit 4.
[0075]
As described in the related art, it has been proposed that the operating frequency of the inverter circuit 4 be modulated to stably turn on the light at a low luminous flux. However, in order to realize a configuration in which the operating frequency of the inverter circuit 4 is continuously changed every cycle by using the microcomputer 20, it is necessary to use the microcomputer 20 that can perform arithmetic processing at high speed. Further, since the microcomputer 20 is used not only for the inverter circuit 4 but also for the processing of the chopper circuit 3 and the wireless signal, the microcomputer 20 having a higher speed and a higher performance is required and the cost is increased.
[0076]
In addition, a configuration has been conventionally known in which a lamp output (at least one of a lamp current and a lamp voltage) is detected and feedback control is performed to stabilize the lamp output. When the feedback control is performed by using the analog circuit, the on-duty of the chopper circuit 3 and the operating frequency of the inverter circuit 4 can be updated successively. Operation processing is required. In particular, in order to prevent extinguishing at a low luminous flux and stably turn on the light, it is necessary to switch the operating frequency of the inverter circuit 4 as in the third embodiment, and such an operation requires high speed.
[0077]
Therefore, in the present embodiment, a technique for simply changing the operating frequency (switching frequency) of the switching elements Q1 and Q2 of the inverter circuit 4 and a cycle for updating the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 are described. By combining with a relatively long feedback control technique, it is possible to control the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 while using a relatively low-performance and inexpensive microcomputer 20. Stable lighting in a low luminous flux area is realized.
[0078]
The operation of the present embodiment will be described. As shown in FIG. 15A, the driving frequency of the switching elements Q1 and Q2 provided in the inverter circuit 4 is different from the reference frequency f1 determined according to the dimming level by the frequency Ta for a period Ta for each cycle Tb. (F1 ≧ f2). By this operation, as shown in FIG. 15B, the applied voltage Vla of the discharge lamp La changes in a pulse shape for the period Ta and the time Ta. As a result, as shown in FIG. 15C, the lamp current Ila of the discharge lamp La temporarily increases, and the lamp is prevented from going out. Although a dimming signal is not shown in FIG. 14, it is assumed that a dimming signal is appropriately input from the outside similarly to the third embodiment.
[0079]
On the other hand, the lamp current detected by the detecting means 15 is input to the microcomputer 20 at times t1 to t2 shown in FIG. 15A, and an integrated value or an average value at times t1 to t2 is obtained and stored in the set value storing means 25. Find the difference from the set value. The microcomputer 20 calculates the operating frequency of the inverter circuit 4 necessary to keep the lamp current of the discharge lamp La at the set value from the obtained difference, and uses the calculated drive frequency as the operating frequency of the inverter circuit 4 at time t2. Apply. That is, the lamp output is corrected by the average value of the lamp output (lamp current) at the time t1 to t2. If the time t1 to t2 = Tc, the operating frequency of the inverter circuit 4 is fed back at the cycle of the time Tc. It will be updated by control. The relationship between the time Ta, the cycle Tb, and the time Tc is Ta <Tb <Tc. The period Tb is preferably set to several hundreds μs to several ms in order to prevent extinction. In order to realize a low luminous flux, the shorter the period during which the lamp current is increased, the smaller the light output can be made. It is desirable that the time Ta is set to approximately 1/5 to 1/10. That is, the time Ta is several tens μs to several hundreds μs.
[0080]
By the way, the capacity of the capacitor C3 provided in the chopper circuit 3 is finite, and the voltage between both ends of the capacitor C3 changes so as to include a half-period ripple of the input voltage from the AC power supply 1, which also affects the lamp output. Appears. Therefore, it is desirable to set the time Tc to a half cycle of the voltage of the AC power supply 1 or an integral multiple thereof, in order to prevent the influence of the ripple component in the feedback control.
[0081]
In the present embodiment, an example in which the operating frequency of the inverter circuit 4 is controlled to stabilize the lamp output has been described. However, the output voltage of the chopper circuit 3 (the voltage across the capacitor C3) is controlled based on the output of the detecting means 14. The same applies to control. Preferably, the output voltage of the chopper circuit 3 and the operating frequency of the inverter circuit 4 are both feedback-controlled.
[0082]
As described above, the operation frequency can be made as simple as switching the operation frequency of the inverter circuit 4 in two stages, and the operation frequency can be updated at a relatively long cycle when performing the feedback control of the lamp output. Even if a relatively low-performance and inexpensive microcomputer 20 is used, the discharge lamp La can be prevented from extinguishing, the lamp output can be stabilized, and stable lighting at low luminous flux can be achieved. In the example shown in FIG. 14, the lamp current is detected to detect the lamp output. For example, the current flowing through the switching elements Q1 and Q2 of the inverter circuit 4 and the resonance circuit (consisting of the inductor L1 and the capacitor C1) are detected. A configuration for equivalently detecting the output of the discharge lamp La, such as a resonance current, may be employed.
[0083]
(Embodiment 5)
The present embodiment operates to switch the operating frequency of the inverter circuit 4 in two stages, similarly to the fourth embodiment, and the two types of operating frequencies set in the microcomputer 20 correspond to the basic frequency (data of the basic frequency). ) And the frequency change width (data thereof). The frequency change width is set in a plurality of stages according to the dimming level, and the microcomputer 20 stores a conversion table (corresponding to the conversion table 22 shown in FIG. 5) in which the dimming level is associated with the frequency change width of each stage. Provide. Therefore, the operating frequency of the inverter circuit 4 at each dimming level is determined by adding the frequency change width according to the dimming level to the basic frequency.
[0084]
This will be specifically described below. Assuming that the resolution of the signal that can be output by the microcomputer 20 is α and the frequency data corresponding to the frequency f1 in FIG. 15 is Df (Df is an arbitrary integer), the relationship becomes f1 = 1 / (Df × α). . By setting the frequency data Df for each dimming level, the operating frequency of the inverter circuit 4 for each dimming level is set. Here, data corresponding to the frequency change width is assumed to be Dx (Dx is an arbitrary integer), and when changing to the frequency f2 in FIG. 15, Df → Df + Dx in the form of f2 = 1 / ((Df + Dx) × α). By performing the processing in the microcomputer 20 so as to replace it, switching of the operating frequency can be realized.
[0085]
Further, in the present embodiment, if the operating frequency is updated by changing the value of the frequency data Df by the feedback control as shown in the fourth embodiment, the frequency change width can be made substantially constant. Furthermore, the value of the frequency change width data Dx may be set to an appropriate natural number in the range of the deep dimming level in which the countermeasure against extinction described in the third embodiment is required, and shallow dimming in which the countermeasure against extinction is unnecessary. At the level, Dx = 0 may be set. Other configurations and operations are the same as those of the fourth embodiment.
[0086]
(Embodiment 6)
In the present embodiment, when the operating frequency of the inverter circuit 4 is switched by the microcomputer 20, the switching timing is given by a trigger from an external circuit provided separately from the microcomputer 20. In order to make the change in the light output of the discharge lamp La invisible while changing the lamp output by switching the operating frequency of the inverter circuit 4, the cycle of switching the operating frequency is generally set to 10 ms or less. is necessary.
[0087]
Therefore, in the present embodiment, as shown in FIG. 16, comparators CP1 and CP2 are provided for comparing the pulsating voltage obtained by rectifying the AC power supply 1 by the rectifier circuit 2 with threshold values Th1 and Th2 set in two stages, respectively. By comparing the outputs of the comparators CP1 and CP2 with the comparator CP3, a pulse signal for instructing switching of the operating frequency is generated.
[0088]
FIG. 17 shows the operation of the configuration shown in FIG. Now, assuming that the frequency of the AC power supply 1 is 50 Hz, the period of the pulsating waveform output from the rectifier circuit 2 shown in FIG. 17A is 10 ms. If the thresholds Th1 and Th2 are set so that the rising and falling of each of the comparators CP1 and CP2 have the timings shown in FIGS. 17B and 17C, the outputs of the two comparators CP1 and CP2 are combined. With the output of the comparator CP3, four risings and fallings can be obtained within 10 ms as shown in FIG. That is, if the output of the comparator CP3 is input to the microcomputer 20 and the operating frequency of the inverter circuit 4 is switched using the four timings as a trigger, the operating frequency can be switched at a period of about 2.5 ms. In the present embodiment, a trigger to the microcomputer 20 is obtained by providing two thresholds Th1 and Th2. However, if it is necessary to make the cycle of the trigger even shorter, three or more thresholds can be set. Just fine. Other configurations and operations are the same as those of the fifth embodiment.
[0089]
(Embodiment 7)
In the present embodiment, as shown in FIG. 18, the lamp voltage detecting means 9 is basically added to the circuit configuration of the first embodiment. The microcomputer 20 supplies a control signal out1 to the switching elements Q1 and Q2 of the inverter circuit 4 via the driver 7, and supplies a control signal out2 to the switching element Q3 of the chopper circuit 3 via the driver 8. The lamp voltage detecting means 9 is configured using a comparator or the like so that the output is inverted when the lamp voltage exceeds a preset threshold value. Is input to the terminal with.
[0090]
In the present embodiment, the microcomputer 20 stops the control signals out1 and out2 to the chopper circuit 3 and the inverter circuit 4 when the output of the lamp voltage detecting means 9 rises or falls. By this operation, when the discharge lamp La is removed, or when the load impedance suddenly rises due to an abnormality of the discharge lamp La, for example, when the voltage (lamp voltage) Vla across the discharge lamp La suddenly rises. In addition, it is possible to stop the operation of the inverter circuit 4 before the stress on the element becomes excessive and the element is destroyed. That is, as shown in FIG. 19A, when an abnormality occurs at time t3 and the lamp voltage Vla exceeds a threshold value (shown by a dashed line) set in the lamp voltage detecting means 9 at time t4, FIG. As shown in (b), the output of the lamp voltage detecting means 9 is inverted and falls, and the microcomputer 20 immediately stops the control signals out1 and out2. As described above, the microcomputer 20 can be immediately stopped by merely interrupting the microcomputer 20 for an abnormality in which the lamp voltage Vla suddenly changes among the discharge lamps La. Protection can be provided.
[0091]
(Embodiment 8)
In the present embodiment, as shown in FIG. 20, a lamp voltage detecting means 9 'and an AD converter 10 are provided instead of the lamp voltage detecting means 9 in the configuration of the seventh embodiment. While the lamp voltage detecting means 9 of the seventh embodiment has a binary output, the lamp voltage detecting means 9 'of the present embodiment outputs a DC voltage (for example, an average voltage) corresponding to the envelope of the lamp voltage Vla. Output. That is, a voltage corresponding to the lamp voltage Vla is input to the microcomputer 20 via the AD converter 10.
[0092]
In the present embodiment, the microcomputer 20 compares a voltage corresponding to the lamp voltage Vla detected by the lamp voltage detecting means 9 ′ with a threshold value preset in the microcomputer 20, and when the lamp voltage Vla exceeds the threshold value, The microcomputer 20 is configured to stop outputting the control signals out1 and out2 to the chopper circuit 3 and the inverter circuit 4. Therefore, at the end of the life of the discharge lamp La, when a half-wave discharge state (Emiless state) occurs due to the decrease of the emitter applied to the filament, the rise of the lamp voltage Vla is detected and the operations of the chopper circuit 3 and the inverter circuit 4 are performed. Can be stopped, and as a result, an increase in stress on the element can be suppressed.
[0093]
In the case of an abnormality such as the Emiless state described above, it is necessary to catch a relatively gradual change in the lamp voltage Vla. Therefore, a configuration in which the output of the lamp voltage detecting means 9 ′ is converted into a digital value by the AD converter 10. And a value corresponding to the lamp voltage Vla is input to the microcomputer 20 to perform arithmetic processing inside the microcomputer 20 and make a determination.
[0094]
For example, a digital value corresponding to the output Vy of the lamp voltage detecting means 9 'as shown in FIG. 21 (a) is read by the microcomputer 20 at a constant period from time t5 to t8, and the microcomputer 20 reads the digital value from time t6 to t8 as shown at time t6 to t8. It is determined that an abnormality has occurred when the threshold value (dashed-dotted line) is exceeded consecutively, and the microcomputer 20 stops the control signals out1 and out2 to the chopper circuit 3 and the inverter circuit 4 as shown in FIG. It is.
[0095]
In the example shown in FIG. 21, when the output of the lamp voltage detecting means 9 ′ exceeds the threshold value three times in succession, it is determined that an abnormality has occurred. The average value may be compared with an appropriate threshold value to determine the Emiless state, or when the average value exceeds the threshold value continuously for a predetermined number of times, it may be determined that there is an abnormality. In the present embodiment, for an abnormality in which the lamp voltage of the discharge lamp La changes relatively slowly, the average value of the lamp voltage is obtained, or the number of times the lamp voltage exceeds the threshold value is obtained. By stopping by the determination by the software processing, the protection against the abnormality can be accurately performed. Other configurations and operations are the same as those of the seventh embodiment.
[0096]
(Embodiment 9)
In this embodiment, as shown in FIG. 22, a setting value storage means 25 is added to the microcomputer 20 in the configuration of the eighth embodiment. The set value storage means 25 stores threshold values set for each dimming level in the form of a table.
[0097]
In the characteristics of the discharge lamp La, as shown in FIG. 23, the lamp voltage Vla tends to increase as the dimming level increases. Therefore, when the Emiless state of the discharge lamp La is detected by the lamp voltage Vla, the threshold value for judging an abnormality must be changed according to the dimming level. For example, if a threshold value is set for the lamp voltage Vla when the discharge lamp La is turned on 100%, it is determined that the normal discharge lamp La is abnormal even if it is not in the Emiless state during dimming. The possibility arises. Further, if the threshold value is set higher than the lamp voltage Vla in the entire range in which the dimming level can be set, the detection will be delayed despite the fact that the lamp is in the Emiless state at 100% lighting. That is, the time from the occurrence of an abnormality to the determination of an abnormality becomes longer, and the state in which the stress on the element is increased continues, which may lead to destruction of the element before detecting the abnormality.
[0098]
Therefore, in the present embodiment, the threshold value according to the dimming level is set in the set value storage unit 25, and the threshold value along the curve of the lamp voltage Vla shown in FIG. Accordingly, an appropriate threshold value can be set for each dimming level, and even if the dimming level changes, protection against a circuit abnormality can be performed accurately. In addition, since it is not necessary to increase the degree of allowance for stress, it is possible to provide the device at low cost without using a high withstand voltage element. Other configurations and operations are the same as those of the eighth embodiment.
[0099]
(Embodiment 10)
As shown in FIG. 24, the present embodiment has basically the same configuration as that of the eighth embodiment shown in FIG. 20. Instead of directly detecting the lamp voltage Vla, a DC cut capacitor is used. The position of C0 is changed, and the voltage across capacitor C0 is detected by detection means 9 ". The output of detection means 9" is converted to a digital value by AD converter 10 and input to microcomputer 20. In the eighth embodiment, the capacitor C0 is connected between the connection point of the switching elements Q1 and Q2 and the inductor L1, but in the present embodiment, one end (circuit ground) of the switching element Q2 on the low potential side and the discharge lamp La Connected to one end of the In the microcomputer 20, thresholds are set above and below the reference value. That is, both when the digital value output from the AD converter 10 exceeds the upper threshold value and when the digital value falls below the lower threshold value are determined to be abnormal. In other words, an upper limit value and a lower limit value are set in the normal range, and if the voltage Vy corresponding to the voltage Vc0 across the capacitor C0 detected by the detecting means 9 "deviates from the range between the upper limit value and the lower limit value, it is determined that there is an abnormality. You do it.
[0100]
As shown in FIG. 24, the detecting means 9 ″ includes resistors Ra1 and Ra2 for dividing the voltage between both ends of the capacitor C0, and includes a resistor Ra3 inserted between a connection point between the resistors Ra1 and Ra2 and the power supply VDD. Since the voltage Vc0 across the capacitor C0 increases or decreases in the Emiless state, the Emiless state is detected by setting the upper limit value and the lower limit value in the microcomputer 20 and determining whether there is an abnormality as described above. Here, when the Emiless state is determined using the voltage Vc0 across the capacitor C0, a two-step threshold is required as described above, and the determination will be made using an analog circuit. In this case, two comparators are required. However, by using the microcomputer 20 as in the present embodiment, no comparator is required, and as a result, the number of parts is reduced. It can be reduced.
[0101]
The position of the capacitor C0 is not limited to the position shown in FIG. 24, but can be used for detecting the Emiless state. Further, the voltage Vc0 across the capacitor C0 may have both positive and negative polarities in the emiless state of the discharge lamp La. However, in this embodiment, as shown in FIG. Since the bias is applied, the polarity of the output voltage of the detecting means 9 "can be kept positive. Other configurations and operations are the same as those of the eighth embodiment.
[0102]
(Embodiment 11)
In the present embodiment, as shown in FIG. 26, a power supply synchronization signal detecting means 16 for detecting a zero cross point of the voltage waveform of the AC power supply 1 is added to the configuration of the fourth embodiment shown in FIG. That is, the power supply synchronizing signal detecting means 16 generates a pulse-like power supply synchronizing signal as shown in FIG. 27B corresponding to the zero crossing point in the voltage waveform of the AC power supply 1 as shown in FIG. I do. Therefore, the generation period T of the power supply synchronization signal matches the half period of the power supply voltage. The power synchronization signal output from the power synchronization signal detecting means 16 is input to the microcomputer 20.
[0103]
In the present embodiment, at least one of the output voltage of the chopper circuit 3 detected by the detection unit 14 and the lamp output (lamp current) detected by the detection unit 15 is input from the power supply synchronization signal detection unit 26 to the microcomputer 20. Are read from the A / D converters 16 and 17 as digital values at a cycle of approximately 1 / 2n (n = 1, 2, 3,...) Of the cycle of the power supply synchronizing signal. The difference between the output voltage of the circuit 3 and the set value is calculated, and the digital value input through the detecting means 15 calculates the difference between the set value and the lamp output. The obtained difference value is obtained as a total value in the cycle of the power supply synchronization signal, and an appropriate function is applied to the total value to output the chopper circuit 3 (on-duty of the switching element Q3) or the operation of the inverter circuit 4. Determine the frequency.
[0104]
Specifically, the output voltage on-duty of the chopper circuit 3 or the operating frequency of the inverter circuit 4 is determined as follows. However, hereinafter, a case will be described in which the on-duty of the switching element Q3 of the chopper circuit 3 is controlled based on the output voltage of the chopper circuit 3 detected by the detection unit 14. Now, at an appropriate dimming level, the reference value of the on-period of the switching element Q3 of the chopper circuit 3 is Ton0, the on-time after correction is Ton, and the digital value output from the AD converter 16 corresponding to each. Are Don0 and Don, and the resolution of a signal that can be output by the microcomputer 20 is α. Therefore, Ton0 = Don0 × α and Ton = Don × α. Further, the set value corresponding to the output voltage of the chopper circuit 3 at this dimming level is VA (digital value), and the digital value output from the AD converter 16 is V1.
[0105]
As shown in FIG. 29, first, the counter j is initialized to 0 (S1), and then, with respect to the period T of the power synchronization signal output from the power synchronization signal detecting means 26, approximately 1 / 2n (n = 1, The output voltage V1 of the chopper circuit 3 is read into the microcomputer 20 through the AD converter 16 at a cycle of (2, 3,...) (S2). For the output voltage V1 of the chopper circuit 3, a difference δV (= VA−V1) from the set value VA is first obtained (S3). Next, the differences δV for 2n times in the period T are summed, and a total difference value ΔV (= ΣδV) is obtained (S4, S5). Next, the total value ΔV is substituted into an appropriate function G (x) as shown in FIG. 28 with the origin being symmetrical, and a correction value DAi (i = 1, 2) of the ON time of the switching element Q3 provided in the chopper circuit 3 , 3,...) (DAi = G (△ V)) (S6). Here, the subscript i means the correction value DAi obtained at each timing, and the function G (x) is invariant with respect to the subscript i. When the correction value DAi is obtained as described above, the correction value DAi is added to the reference value Ton0 of the ON period of the switching element Q3 (S7). That is, the ON time Don of the switching element Q3 is determined as Don = Don0 + ΣDAi (S8).
[0106]
The on-time Ton of the switching element Q3 of the chopper circuit 3 is updated every cycle T by repeating the operation shown in FIG. 29 every time a power supply synchronization signal is generated (every cycle T). In this way, when DAi = 0, that is, VA = V1, the operation is stabilized. In this way, feedback control using the set value VA as a target value becomes possible, and the output voltage of the chopper circuit 3 can be stabilized. As a result, the lamp output can be stabilized. The capacitance of the capacitor C3 of the chopper circuit 3 is finite, and the voltage across the capacitor C3 includes a half cycle T of a ripple with respect to the voltage cycle of the AC power supply 1. Since the output voltage of the chopper circuit 3 is taken into the microcomputer 20 to calculate the on-time Ton of the switching element Q3 based on the total value, the influence of the ripple component can be removed. The output voltage can be sufficiently stabilized.
[0107]
In the present embodiment, an example has been described in which the difference δV between the set value VA and the output voltage V1 of the chopper circuit 3 is calculated, and then the total value ΔV is calculated 2n times in the cycle T. After summing the output voltage V1 of the circuit 3 2n times during the period T, a difference from the set value VA × n may be obtained, and this difference may be used as the total value ΔV. Further, the correction value DAi may be obtained by applying the function G (x) to the difference δV and obtaining the total value of 2n times of G (δV) during the period T. Further, the subsequent processing may be performed using an average value of 2n times instead of the total value of 2n times during the cycle T. When the average value is used, the read cycle of the AD converter 16 is set to approximately T / 2. ⁿ If (n = 1, 2, 3,...), The average value can be obtained by n-bit shift, so that the calculation process is simplified and the calculation time can be shortened.
[0108]
Further, in the present embodiment, the read cycle of the AD converter 16 is substantially T / 2n (n = 1, 2, 3,...), But the first half (1 to n-th) and the second half (1 to n) of the cycle T (n + 1 to 2nth) may be the same time interval pattern. For example, assume that n = 4, 8 points are read at a period T, the basic reading period is “5”, and the time interval at which data is input to the AD converter 16 is [5, 5, 6, 5, 5 , 5, 6, 5, 5] or [5, 6, 4, 5, 5, 6, 4, 5]. Here, each number in [] represents a time interval from the time when the AD converter 16 reads a value to the time when the value is next read.
[0109]
Further, in the present embodiment, an example in which the output voltage of the chopper circuit 3 is detected to set the ON time Ton of the switching element Q3 of the chopper circuit 3 is described. It controls the operating frequency, controls the operating frequency of the inverter circuit 4 by detecting the output voltage of the chopper circuit 3, and controls the on time Ton of the switching element Q3 of the chopper circuit 3 by detecting the lamp output. In such a case, a similar technical idea can be applied.
[0110]
FIGS. 30 to 34 show setting examples of the function G (x) other than the function G (x) described above. The function G (x) shown in FIG. 30 is defined as a linear function, and is defined in the microcomputer 20 not in a table but in the form of a mathematical expression. As described above, if the function G (x) is defined by the equation in the microcomputer 20, the storage capacity can be reduced.
[0111]
In the example shown in FIG. 31, the absolute value of the correction value DAi is limited in the function G (x). For example, in the function G (x) defined by the linear function shown in FIG. The upper limit value and the lower limit value are defined for the correction value DAi. By limiting the correction value DAi, the output voltage V1 greatly deviates from the set value VA due to an excessively large difference δV between the output voltage V1 of the chopper circuit 3 and the set value VA, or a sudden change in load. In such a case, it is possible to prevent the correction value DAi from becoming extremely large and the operation of the chopper circuit 3 from entering an unsafe area.
[0112]
In the example shown in FIG. 32, in the function G (x), the correction value DAi is set to approximately 0 in a predetermined range near the origin of the total value ΔV. In other ranges, they are defined by linear functions. That is, since the digital value output from the AD converter 16 may be shifted due to disturbance noise or the like after the operation is finally stabilized and the operation is near the origin, the influence of such a shift is prevented. In order to do so, a dead area is provided. That is, by providing a dead area in the function G (x), it is possible to suppress the influence of minute disturbance noise and the like.
[0113]
In the example shown in FIG. 33, the function G (x) is defined by an appropriate cubic function. As in the case of the linear function, the microcomputer 20 defines the function G (x) by an equation. That is, the storage capacity is reduced.
[0114]
The example shown in FIG. 34 is a table in which the total value ΔV and the correction value DAi are associated with each other as the function G (x). The function G (x) is defined using the data of the white circle shown in FIG. 34 as the table. are doing. By using such a table, when complicated relations such as the nonlinear functions and higher-order functions shown in FIGS. 31 to 33 are established, the arithmetic processing is simplified and the microcomputer having a relatively low processing capability is used. Even if it is 20, arithmetic processing can be performed in a practical time.
[0115]
In each of the embodiments described above, the step-up chopper circuit 3 is used as the DC-DC conversion circuit. However, a chopper circuit having another configuration or a DC-DC conversion circuit such as a flyback type is used. Is also good. In short, any configuration can be used as long as the output voltage can be externally controlled. Further, the half bridge type inverter circuit having a DC cut capacitor is exemplified as the inverter circuit 4, but the technical concept of the present invention can be applied to an inverter circuit having another configuration. La is not limited to one lamp and may be a plurality of lamps.
[0116]
【The invention's effect】
According to the configuration of the present invention, the DC-DC conversion circuit and the inverter circuit are collectively controlled by one microcomputer, thereby realizing cost reduction by reducing the number of components. In addition, since the combination of the output voltage of the DC-DC conversion circuit and the operating frequency of the inverter circuit can be controlled by a table provided in the microcomputer, the preheating, starting, steady lighting, dimming, etc., when the discharge lamp is lit. Appropriate control can be performed according to each operation state. In addition, when the operating frequency of the inverter circuit is increased to reduce the light output of the discharge lamp, the output voltage of the DC-DC conversion circuit is also reduced, so that a discharge lamp lighting device suitable as a light distribution lighting device is provided. Can be.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment.
FIG. 2 is a circuit diagram showing a second embodiment.
FIG. 3 is an operation explanatory diagram showing the second embodiment.
FIG. 4 is an operation explanatory view showing a third embodiment.
FIG. 5 is a main block diagram of a third embodiment.
FIG. 6 is an operation explanatory diagram of the third embodiment.
FIG. 7 is a diagram illustrating an example of a frequency table used in a third embodiment.
FIG. 8 is an operation explanatory diagram of the third embodiment.
FIG. 9 is an operation explanatory diagram of the third embodiment.
FIG. 10 is a diagram illustrating another example of the frequency table used in the third embodiment.
FIG. 11 is a diagram showing still another example of the frequency table used in the third embodiment.
FIG. 12 is a diagram illustrating another example of the frequency table used in the third embodiment.
FIG. 13 is a diagram showing still another example of the frequency table used in the third embodiment.
FIG. 14 is a circuit diagram showing a fourth embodiment.
FIG. 15 is an operation explanatory diagram of the fourth embodiment.
FIG. 16 is a main part circuit diagram of a sixth embodiment.
FIG. 17 is an operation explanatory diagram of the sixth embodiment.
FIG. 18 is a circuit diagram showing a seventh embodiment.
FIG. 19 is an operation explanatory diagram of the seventh embodiment.
FIG. 20 is a circuit diagram showing an eighth embodiment.
FIG. 21 is an operation explanatory diagram of the eighth embodiment.
FIG. 22 is a circuit diagram showing a ninth embodiment;
FIG. 23 is an operation explanatory diagram of the ninth embodiment.
FIG. 24 is a circuit diagram showing a tenth embodiment.
FIG. 25 is a main part circuit diagram of a tenth embodiment.
FIG. 26 is a circuit diagram showing an eleventh embodiment.
FIG. 27 is an operation explanatory diagram of the eleventh embodiment.
FIG. 28 is a diagram illustrating an example of a function used in the eleventh embodiment.
FIG. 29 is an operation explanatory view showing a processing procedure according to the eleventh embodiment.
FIG. 30 is a diagram showing another example of a function used in the eleventh embodiment.
FIG. 31 is a diagram showing still another example of the function used in the eleventh embodiment.
FIG. 32 is a diagram showing still another example of the function used in the eleventh embodiment.
FIG. 33 is a diagram illustrating another example of the function used in the eleventh embodiment.
FIG. 34 is a diagram showing still another example of the function used in the eleventh embodiment.
FIG. 35 is a block diagram showing a conventional example.
FIG. 36 is an operation explanatory diagram of the conventional example.
FIG. 37 is a block diagram showing another conventional example.
FIG. 38 is an operation explanatory diagram of another conventional example.
FIG. 39 is a block diagram showing another conventional example.
[Explanation of symbols]
1 AC power supply
2 Rectifier circuit
3 Chopper circuit (DC-DC conversion circuit)
4 Inverter circuit
9 Lamp voltage detection means
9 'lamp voltage detecting means
9 "detection means
11 Wireless receiver
14 Detecting means
15 Detecting means
20 microcomputer
21 Dimming signal extraction means
22 Conversion table
23 Output pulse generation means
24 PWM output means
25 Set value storage means
C1 capacitor
L1 inductor
La discharge lamp
Q1-Q3 switching element

Claims (13)

A DC-DC conversion circuit in which a DC output voltage is variable by controlling on / off of a switching element, an inverter circuit for converting a DC voltage output from the DC-DC conversion circuit into a high-frequency voltage, and an output from the inverter circuit A resonance circuit provided in a path for supplying a high-frequency voltage to the discharge lamp, and a microcomputer which collectively generates control signals for the output voltage of the DC-DC conversion circuit and the operating frequency of the inverter circuit, and is provided with a steady state during dimming. A discharge lamp lighting device, wherein a table is set in a microcomputer so that the output voltage of the DC-DC conversion circuit is lower than at the time of lighting and the operating frequency of the inverter circuit is increased. A microcomputer configured to generate a control signal to be provided to the data bit string included in the wireless signal, the DC-DC conversion circuit, and the inverter circuit; 2. The discharge lamp lighting device according to claim 1, further comprising: a conversion table in which data are associated with each other; and an output pulse generation unit configured to generate the control signal from a clock signal based on the data obtained from the conversion table. . 3. The discharge lamp lighting device according to claim 2, wherein the microcomputer includes a dimming signal extracting unit that extracts a data bit string to be compared with a conversion table from a pulse signal output from the wireless receiving unit. In the frequency table for determining the operating frequency of the inverter circuit in the conversion table, the operating frequency of the dimming level deeper than a specified value near a point where the slope in the negative characteristic region of the current-voltage characteristic of the discharge lamp is maximum is obtained. And the operating frequency of a dimming level shallower than the specified value are associated one-to-one, and the microcomputer periodically switches between both operating frequencies when a dimming level deeper than the specified value is selected. The discharge lamp lighting device according to claim 1, wherein: In the conversion table, in the frequency table that determines the operating frequency of the inverter circuit, all of the dimming levels deeper than a specified value near the point where the slope in the negative characteristic region of the current-voltage characteristic of the discharge lamp is maximum are obtained. The operating frequency is associated with one operating frequency having a dimming level shallower than the specified value, and when the dimming level deeper than the specified value is selected, the microcomputer performs dimming deeper than the specified value. 2. The discharge lamp lighting device according to claim 1, wherein an operation frequency of a level and an operation frequency of a dimming level shallower than the specified value associated with the operation frequency are periodically switched. 2. The discharge lamp lighting device according to claim 1, wherein the microcomputer changes at least one of a cycle in which the operating frequency of the inverter circuit is changed and a period in which the operating frequency is changed according to the dimming level. 3. 2. The microcomputer according to claim 1, wherein a plurality of sets of operating frequencies of the inverter circuit are associated with the dimming level, and the operating frequencies forming the set at the selected dimming level are cyclically selected. Discharge lamp lighting device. Detecting means for detecting the output of the discharge lamp, and set value storage means for associating a dimming level with a set value of the output of the discharge lamp are added, and the microcomputer sets the operating frequency of the inverter circuit to: A discharge lamp having a function of alternately switching between a first operating frequency for lighting the discharge lamp at a selected dimming level and a second operating frequency for preventing the discharge lamp from extinction, and a discharge lamp detected by the detection means; And a function of updating the first and second operating frequencies of the inverter circuit so that the output of the inverter circuit approaches the set value in the set value storage means. The discharge lamp lighting device according to claim 1, wherein a cycle for updating the first and second operating frequencies is set longer than a cycle for selecting. 7. The discharge lamp lighting device according to claim 4, wherein a timing of switching the operating frequency of the inverter circuit by the microcomputer is given by a trigger from an external circuit provided separately from the microcomputer. . Lamp voltage detection means for detecting the lamp voltage of the discharge lamp and inverting when the lamp voltage exceeds a set threshold value is added, and the microcomputer receives an interrupt due to inversion of the output of the detection means. 2. The discharge lamp lighting device according to claim 1, wherein the operations of the DC-DC converter and the inverter circuit are stopped. Lamp voltage detecting means for outputting a DC voltage reflecting the lamp voltage of the discharge lamp; and 2. The discharge lamp lighting device according to claim 1, wherein the operations of the DC conversion circuit and the inverter circuit are stopped. The discharge lamp lighting device according to claim 11, further comprising a set value storage unit that associates the upper limit value and the lower limit value with each light control level. First detection means for detecting the output of the discharge lamp, second detection means for detecting the output voltage of the DC-DC conversion circuit, and a set value of the output of the discharge lamp associated with a dimming level. Setting value storage means, wherein the microcomputer obtains a difference between the setting value stored in the setting value storage means and a detection value by the first or second detection means, and calculates a total value of the difference a plurality of times or An average value is calculated and at least one of an on-time of a switching element provided in the DC-DC conversion circuit and an operation frequency of the inverter circuit is obtained by a correction value obtained by substituting the total value or the average value into a function. 2. The discharge lamp lighting device according to claim 1, wherein the correction is repeated in a cycle for obtaining a total value or an average value of the differences.

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