JP4117561B2

JP4117561B2 - Discharge lamp lighting device

Info

Publication number: JP4117561B2
Application number: JP2003585483A
Authority: JP
Inventors: 修高橋
Original assignee: Mitsubishi Electric Corp; Mitsubishi Electric Lighting Corp
Current assignee: Mitsubishi Electric Corp; Mitsubishi Electric Lighting Corp
Priority date: 2002-04-12
Filing date: 2002-04-12
Publication date: 2008-07-16
Anticipated expiration: 2022-04-12
Also published as: CN1516992A; CN100431392C; JPWO2003088722A1; WO2003088722A1

Description

技術分野
この発明は、自励式インバータ回路からの高周波電力によって放電灯を点灯させる放電灯点灯装置に係り、安価で小型な検出回路で点灯状態を検出して、回路を保護することができる放電灯点灯装置に関する。
技術背景
図５に、従来の放電灯装置の回路図を示す。図において、１は商用電源から得られる直流電源、２及び３は、インバータ回路を構成するＭＯＳＦＥＴからなるスイッチング素子、Ｌ１００、Ｌ１１０は並列接続された放電灯負荷回路である。放電灯負荷回路Ｌ１００はチョークコイル５、放電灯６、放電灯６に並列に接続されたコンデンサ７及びカップリングコンデンサ８から構成される。
放電灯負荷回路Ｌ１１０はチョークコイル９、放電灯１０、放電灯１０に並列に接続されたコンデンサ１１及びカップリングコンデンサ１２から構成される。
４は２つのスイッチング素子２及び３の接続点と放電灯負荷回路Ｌ１００及びＬ１１０の並列回路の接続点間に接続された変流器（以下ＣＴと呼ぶ）で、その２次巻線４ａ、４ｂは図示・印の極性でスイッチング素子２及び３を交互にＯＮ／ＯＦＦ駆動するように抵抗１３及び抵抗１４を介してスイッチング素子２及び３のゲート、ソース間に接続される（ＣＴ４の１次巻線と２次巻線との結合を表すため、破線で図示してある。）。
なお、スイッチング素子２及び３のドレイン・ソース間に並列に内蔵されている等価ダイオード及びインバータを起動するための起動回路の図示を省略している。
Ｐ１００は放電灯負荷回路Ｌ１００のチョークコイル５と放電灯６の接続点ａ１００と直流電源１の負極ｂ１００（ダイオード５２のアノード近傍に図示）間に印加されるピーク間電圧（ｐｅａｋｔｏｐｅａｋ電圧）を検出するピーク間電圧検出回路、Ｐ１１０は放電灯負荷回路Ｌ１１０のチョークコイル９と放電灯１０の接続点ａ１１０と直流電源１の負極ｂ１１０（ダイオード５５のアノード近傍に図示）間に印加されるピーク間電圧を検出するピーク間電圧検出回路である。
ピーク間電圧検出回路Ｐ１００において、５０、５１は直列に接続されたコンデンサで５０の一端は直流電源１の負極に５１の他端はチョークコイル５と放電灯６の接続点に接続される。５２はアノードが直流電源１の負極にカソードがコンデンサ５０とコンデンサ５１の接続点に接続されたダイオードである。
この構成により、接続点ａ１００と直流電源１の負極ｂ１００間に印加されるピーク間電圧を、コンデンサ５１とコンデンサ５０の静電容量値の逆比でダイオード５６のアノードに取り出す。
ピーク間電圧検出回路Ｐ１１０において、５３、５４は直列に接続されたコンデンサで５３の一端は直流電源１の負極に５４の他端はチョークコイル９と放電灯１０の接続点に接続される。５５はアノードが直流電源１の負極にカソードがコンデンサ５３とコンデンサ５４の接続点に接続されたダイオードである。
この構成により、接続点ａ１１０と直流電源１の負極ｂ１１０間に印加されるピーク間電圧をコンデンサ５４とコンデンサ５３の静電容量値の逆比でダイオード５７のアノードに取り出す。
ダイオード５６とダイオード５７のカソードは接続され、その接続点と直流電源１の負極の間にコンデンサ５８が接続され、ピーク間電圧検出回路Ｐ１００、Ｐ１１０の電圧の内高い方の電圧がコンデンサ５８の両端に直流電圧としてピーク検出される。
Ｈ１００は回路を保護する保護回路であり、６１はダイオード５６と５７の接続点にカソードが接続されたツェナーダイオードでそのアノードから抵抗６０及び抵抗５９を介して直流電源１の負極に接続される。６２は抵抗６０と抵抗５９の接続点にゲートが接続されたサイリスタで、そのカソードは直流電源１の負極に、そのアノードはダイオード６３のカソードに接続される。ダイオード６３のアノードはスイッチング素子３のゲートに接続される。また、サイリスタ６３のアノードから抵抗６４を介して直流電源１の正極に接続される。
なお、商用電源から直流電源を得る場合の直流電源１の構成例を図６に示す。図に示すように、商用電源１ａから出力された交流電源は、ダイオードブリッジ１ｂで全波整流された後、平滑コンデンサ１ｃで平滑化され、直流電源として負荷回路に出力されるように構成される。
以下、この図５に示した従来例の回路の動作を説明する。
図において、直流電源１が投入されると、図示を省略している起動回路によってスイッチング素子２及び３は交互に高周波で駆動され放電灯は点灯に至る。
ここで、例えば放電灯６がフィラメントの放電物質の消耗などで寿命末期になれば、放電灯６の両端電圧は正常点灯時より上昇し、その電圧の変化はピーク間電圧検出回路Ｐ１００で検出され、ダイオード５６のアノード電圧が上昇し、コンデンサ５８の電圧も上昇する。また、ツェナーダイオード６１、抵抗６０、抵抗５９を適当に選定して、サイリスタ６２が放電灯６が正常点灯している時に得られるコンデンサ５８の電圧ではＯＮせず、放電灯の寿命末期のように電圧が上昇した場合にコンデンサ５８に得られる電圧によってＯＮするようにする。サイリスタ６２がＯＮすれば、ＣＴ４の２次巻線４ｂから抵抗１３を介してスイッチング素子３のゲートに流れる電流がダイオード６３、サイリスタ６２を介してバイバスされるため、スイッチング素子３はＯＦＦになりインバータ回路の発振は停止する。
そして、発振が停止しても、サイリスタ６２には抵抗６４を介して保持電流が流れ続けるので直流電源１を遮断後再投入するまでこの状態は保持されるので、放電灯６が異常放電を継続した状態で運転することを防止できるものであった。
なお、上記では放電灯６が正常放電でない場合の説明をしたが、放電灯１０が正常放電でない場合、及びいずれの放電灯も正常放電でない場合でも同様に異常放電を継続した状態で運転することを防止できるものであった。
しかしながら、上記構成では放電灯６、１０の両端電圧は、正常点灯時で例えばラピドスタート形蛍光放電灯４０Ｗで約９５Ｖ程度、３２ＷＨｆ放電灯で約１２５Ｖ程度、カップリングコンデンサの電圧も放電灯６、１０の両端電圧と同等程度あるのでピーク間電圧検出回路Ｐ１００、Ｐ１１０を構成する部品は大型で高価なものが必要であった。
また、ピーク間電圧検出回路Ｐ１００についていえば、ａ１００とｂ１００との間の電圧は高電圧なので、この電圧をサイリスタ６２のゲートに印加するためには、コンデンサ５１とコンデンサ５０容量比を適当に選定して、コンデンサ５０の両端にはａ１００とｂ１００との間の高電圧が分圧されるようにする必要があるが、分圧することにより正常点灯時と異常点灯時に得られる検出電圧も同じ分圧比で小さくなってしまい、外部ノイズなどに対して充分な識別が困難になる問題があった。
なお、上記のことはピーク間電圧検出回路Ｐ１１０についても同様である。また、ａ１００とｂ１００の間の電圧には放電灯６の電圧の他に、カップリングコンデンサ８の電圧も含まれているので、放電灯６の正常点灯時と異常点灯時の検出電圧の差が大きく得られない問題があった。
また、上記のことはピーク間電圧検出回路Ｐ１１０についても同様である。また、ＣＴ４には放電灯負荷回路Ｌ１００とＬ１１０の合成電流が流れるが放電灯６または放電灯１０の寿命による故障などのためいずれかの一方の放電灯を抜去した場合にはＣＴ４に流れる電流が減少し、そのためＣＴ４の２次巻線電圧も減少しスイッチング素子２及び３の駆動電圧が減少し、それによってインバータ回路の発振周波数は変化するため残った放電灯負荷回路に装着された放電灯電流も変化してしまい、これに伴って、正常点灯時及び異常点灯時にピーク間電圧検出回路Ｐ１００、Ｐ１１０に得られる電圧も変化してしまう問題があった。
この発明は、上記のような問題点を解決するためになされたもので、この発明の第１の目的はピーク間電圧検出回路を構成する部品に大型で高価なものを必要としない安価で小型な放電灯点灯装置を提供することを目的とする。
また、この発明の第２の目的は、正常点灯時と異常点灯時に得られるピーク間電圧検出回路の出力電圧の差が外部ノイズなどに対して充分余裕があり、保護回路の動作の信頼性が高い放電灯点灯装置を提供することを目的とする。
また、この発明の第３の目的は複数の放電灯の内、何れかを抜去しても、残りの放電灯の正常点灯と異常点灯状態を検出するピーク間電圧検出回路の出力電圧の差が全ての放電灯が装着されている場合の検出電圧の差と変わらず、同一の条件で異常状態を検出できる放電灯点灯装置を提供することを目的とする。
また、この発明の第４の目的は複数の放電灯の内、何れかを抜去しても、残りの放電灯の正常点灯と異常点灯状態を検出するピーク間電圧検出回路の出力電圧の差が、全ての放電灯が装着されている場合の検出電圧の差と概略等しい検出電圧を得ることができる安価で簡便な複数の放電灯に対して共通するピーク間電圧検出回路を有する放電灯点灯装置を提供することを目的とする。
発明の開示
この発明に係る放電灯点灯装置は、直流電源と、この直流電源から供給される直流を高周波電流に変換する一対のスイッチング素子を有するハーフブリッジ回路からなるインバータ回路と、このインバータ回路からの高周波電流により放電灯を点灯させ、複数並列接続された放電灯負荷回路とを備えた放電灯点灯装置において、上記各放電灯負荷回路はチョークコイル、放電灯、カップリングコンデンサの直列回路及び上記放電灯に並列に接続されたコンデンサを備え、上記各放電灯負荷回路の上記チョークコイルに各々一対設けられ、各々電流制限素子を介して上記一対のスイッチング素子のゲート・ソース間に接続され、上記一対のスイッチング素子を駆動する電圧を出力する２次巻線と、上記各々の一対の２次巻線の一方の２次巻線の両端に各々直列に接続されたコンデンサの直列回路と、直列に接続された上記コンデンサの一方のコンデンサに並列に接続されたダイオードとからなり、上記ダイオードと並列に接続された上記一方のコンデンサの容量を他方のコンデンサの容量の４倍以下に設定されるとともに、上記一方の２次巻線に発生するピーク間電圧を上記コンデンサの直列回路の他方のコンデンサと上記ダイオードと並列に接続された上記一方のコンデンサとの容量の逆比で検出する複数のピーク間検出回路と、これらの複数のピーク間電圧検出回路により検出された電圧をワイヤードオアした電圧が予め定めた値を越えたときに、上記インバータ回路の発振を停止させ、停止した状態を維持させる保護回路と、を備えたものである。このことによって、ピーク間電圧検出回路の構成部品を小型で安価な部品とすることができる。
また、ピーク間電圧検出回路の出力電圧として正常点灯時と異常点灯時に得られるピーク間電圧検出電圧の差が外部ノイズなどで対して充分余裕があり、保護回路の動作を信頼性を高くすることができる。
また、各放電灯負荷回路及びピーク間電圧検出回路が各々独立して設けられているので、何れかの放電灯を抜去した場合でも、全て装着されている場合と同一の条件で異常点灯状態を検出することができる。
また、部品のバラツキ、周囲温度変動、外来ノイズ等があっても、放電灯の正常点灯時と異常点灯時の識別を安定して行うことができる。
また、ピーク間電圧検出回路は、接続される２次巻線とコンデンサの間に挿入された抵抗を備えたものである。このことによって、チョークコイルの２次巻線のインダクタンス成分とピーク間電圧回路のコンデンサ成分とによる寄生発振を抑制でき、放電灯の正常点灯時と異常放電時の検出電圧の差を大きくすることができる。
また、直流電源と、この直流電源から供給される直流を高周波電流に変換する一対のスイッチング素子を有するハーフブリッジ回路からなるインバータ回路と、このインバータ回路からの高周波電流により放電灯を点灯させ、複数並列接続された放電灯負荷回路とを備えた放電灯点灯装置において、上記各放電灯負荷回路はチョークコイル、放電灯、カップリングコンデンサの直列回路及び上記放電灯に並列に接続されたコンデンサを備え、
上記各放電灯負荷回路の上記チョークコイルに各々一対設けられ、各々電流制限素子を介して上記一対のスイッチング素子のゲート・ソース間に接続され、上記一対のスイッチング素子を駆動する電圧を出力する２次巻線と、上記各々の一対の２次巻線のうち、１つの一対の２次巻線の一方の２次巻線の両端に各々直列に接続された抵抗と２つのコンデンサの直列回路と、直列に接続された上記コンデンサの一方のコンデンサに並列に接続されたダイオードと、他の一対の２次巻線の一方の２次巻線の一端と前記直列回路の前記抵抗及び前記コンデンサの接続点に接続された抵抗とからなり、上記ダイオードと並列に接続された上記一方のコンデンサの容量を他方のコンデンサの容量の４倍以下にするとともに、上記一方の２次巻線に発生するピーク間電圧を上記直列回路の他方のコンデンサと上記ダイオードと並列に接続された上記一方のコンデンサとの容量の逆比で検出する共通のピーク間検出回路と、このピーク間電圧検出回路により検出された電圧が予め定めた値を越えたときに、上記インバータ回路の発振を停止させ、停止した状態を維持させる保護回路と、を備えたものである。このことによって、ピーク間電圧検出回路を放電灯負荷回路に対応して複数設ける必要がないので小型で安価にすることができる。
また、ピーク間電圧検出回路を放電灯負荷回路に対応して複数設ける必要がないので小型で安価にすることができる。
発明を実施するための最良の形態
実施の形態１．
図１は、この発明の実施の形態１を示す放電灯点灯装置の回路図である。
図において、１は商用電源から得られる直流電源、２及び３は、インバータ回路を構成するＭＯＳＦＥＴからなるスイッチング素子、Ｌ１００、Ｌ１１０は並列接続された放電灯負荷回路である。放電灯負荷回路Ｌ１００はチョークコイル５、放電灯６、放電灯６に並列に接続されたコンデンサ７及びカップリングコンデンサ８から構成される。
放電灯負荷回路Ｌ１１０はチョークコイル９、放電灯１０、放電灯１０に並列に接続されたコンデンサ１１及びカップリングコンデンサ１２から構成される。
放電灯負荷回路Ｌ１００、Ｌ１１０のチョークコイル５及び９には、各々２つの２次巻線５ａ、５ｂ、９ａ、９ｂを設け、上記２次巻線は図示・印の極性でスイッチング素子２及び３を交互にＯＮ／ＯＦＦ駆動するように抵抗１３、１５及び抵抗１４、１６を介してゲート、ソース間に接続される。（チョークコイル５及び９の１次巻線と２次巻線の結合を表すため、一点鎖線及び破線で図示してある。）
なお、スイッチング素子２及び３のドレイン・ソース間に並列に内蔵されている等価ダイオード及びインバータを起動するための起動回路の図示を省略している。
また、ここで放電灯６と放電灯１０が同一定格出力の場合は、各放電灯負荷回路Ｌ１００及びＬ１１０の回路定数を等しく選択する。
また、放電灯６と放電灯１０の定格出力が異なる場合は、放電灯負荷回路Ｌ１００、Ｌ１１０の点灯時の共振周波数が概略等しく、また、点灯時の各チョークコイル５、９の２次巻線電圧が概略等しくなるように設定する。
Ｐ１００は、放電灯負荷回路Ｌ１００のチョークコイル５の２次巻線５ｂに発生する電圧のピーク間電圧（ｐｅａｋｔｏｐｅａｋ電圧）を検出するピーク間電圧検出回路、Ｐ１１０は、放電灯負荷回路Ｌ１１０のチョークコイル９の２次巻線９ｂに発生するピーク間電圧を検出するピーク間電圧検出回路である。
ピーク間電圧検出回路Ｐ１００において、１５０、１５１は直列に接続されたコンデンサで、コンデンサ１５０の一端は直流電源１の負極に、１５１の他端はチョークコイル５の２次巻５ｂと抵抗１３の接続点に接続される。
１５２はアノードが直流電源１の負極にカソードがコンデンサ１５０とコンデンサ１５１の接続点に接続されたダイオードである。
この構成により、チョークコイル５の２次巻線間のピーク間電圧を、コンデンサ１５１とコンデンサ１５０の静電容量値の逆比でダイオード１５６のアノードに取り出す。
ピーク間電圧検出回路Ｐ１１０において、１５３、１５４は直列に接続されたコンデンサで１５３の一端は直流電源１の負極に１５４の他端はチョークコイル９の２次巻線と抵抗１５の接続点に接続される。
１５５はアノードが直流電源１の負極にカソードがコンデンサ１５３とコンデンサ１５４の接続点に接続されたダイオードである。
この構成により、チョークコイル９の２次巻線のピーク間電圧を、コンデンサ１５４とコンデンサ１５３の静電容量値の逆比でダイオード１５７のアノードに取り出す。
ダイオード１５６とダイオード１５７のカソードは接続され、その接続点と直流電源１の負極の間にコンデンサ１５８が接続され、ピーク間電圧検出回路Ｐ１００及びＰ１１０の電圧の内高い方の電圧がコンデンサ１５８の両端に直流電圧としてピーク検出される。
Ｈ１００はピーク間電圧検出回路Ｐ１００、Ｐ１１０により検出された電圧が予め定めた値を越えたときに、インバータ回路の発振を停止させる保護回路であり、６１はダイオード１５６と１５７の接続点にカソードが接続されたツェナーダイオードでそのアノードから抵抗６０及び抵抗５９を介して直流電源１の負極に接続される。６２は抵抗６０と抵抗６１の接続点にゲートが接続されたサイリスタで、そのカソードは直流電源１の負極に、そのアノードはダイオード６３のカソードに接続される。ダイオード６３のアノードはスイッチング素子３のゲートに接続される。また、サイリスタ６３のアノードから抵抗６４を介して直流電源１の正極に接続される。
以下、この発明の実施の形態１を示す放電灯点灯装置の動作を図１により説明する。
図１において、直流電源１が投入されると、図示を省略している起動回路によってスイッチング素子２、３は交互に高周波数で駆動され放電灯６、１０は点灯に至る。
ここで、例えば放電灯６がフィラメントの放電物質の消耗などで寿命末期になれば、放電灯６の両端電圧は正常点灯時より上昇し、チョークコイル５の両端電圧も上昇する。その電圧の変化はチョークコイル５の２次巻線５ｂに設けたピーク間電圧検出回路Ｐ１００で検出され、ダイオード１５６のアノード電圧が上昇し、コンデンサ１５８の電圧も上昇する。
また、保護回路Ｈ１００のツェナーダイオード６１、抵抗６０、抵抗５９を適当に選定して、サイリスタ６２が放電灯６、１０が正常点灯している時に得られるコンデンサ１５８の電圧ではＯＮせず、放電灯の寿命末期のように電圧が上昇した場合にコンデンサ１５８に得られる電圧によってＯＮするようにする。
サイリスタ６２がＯＮすれば、チョークコイル５、９の２次巻線５ｂ、９ｂから抵抗１３及び１５を介してスイッチング素子３のゲートに流れる電流がダイオード６３、サイリスタ６２を介してバイバスされるため、スイッチング素子３はＯＦＦになりインバータ回路の発振は停止する。
発振が停止しても、サイリスタ６２には抵抗６４を介して保持電流が流れ続けるので、直流電源１を遮断後再投入するまでこの状態は保持されるので、放電灯６が異常放電を継続した状態で運転することを防止できるものである。
なお、上記では放電灯６が正常放電でない場合の説明をしたが、放電灯１０が正常放電でない場合、及びいずれの放電灯も正常放電でない場合でも同様に異常放電を継続した状態で運転することを防止できる。
ここで、チョークコイル５、９の２次巻線５ｂ、９ｂの電圧はスイッチング素子３のゲート・ソース間閾値電圧より大きな電圧が得られるように選定すれば良く、図５の従来例のようにピーク間電圧検出回路Ｐ１００、Ｐ１１０を各々ａ１００とｂ１００、ａ１１０とｂ１１０の間に設けるよりも充分小さく選定でき、ピーク間電圧検出回路Ｐ１００、Ｐ１１０の構成部品を耐圧の小さい、小型で安価な部品を使用することができる。
また、ピーク間電圧検出回路Ｐ１００において、チョークコイルの２次巻線５ｂの電圧には、放電灯６の正常点灯時と異常点灯時の電圧変化の小さいカップリングコンデンサ８の電圧成分が含まれていないので、正常点灯時と異常点灯時の検出電圧の差が大きく得ることができ、保護回路Ｈ１００を外部ノイズなどで対して充分な識別が可能なものにすることができる。
なお、上記のことはピーク間電圧検出回路Ｐ１１０についても同様である。
また、放電灯６または放電灯１０の寿命による故障などのためいずれかの一方の放電灯を抜去しても各放電灯負荷回路Ｌ１１０、Ｌ１１０は独立しており、そのチョークコイルの２次巻線５ｂ、９ｂに生じる放電灯の正常点灯時及び異常点灯時のピーク間電圧を検出するピーク間電圧検出回路Ｐ１００、Ｐ１１０も独立して各々設けられているので１灯が抜去した場合でも、２灯が全て装着されている場合と同一の条件で異常点灯状態を検出することができる。
ところで、スイッチング素子３をＭＯＳＦＥＴで構成する場合に、そのゲート、ソース間の逆耐電圧は一般的に入手し易い標準品においては２０Ｖ乃至３０Ｖ程度以下であるので、異常点灯時にチョークコイル５、９の２次巻線５ｂ、９ｂに得られる電圧をそのゲート、ソース間の逆耐電圧より小さくなるように選定すれば、スイッチング素子３のＭＯＳＦＥＴとしては安価で入手し易い標準品を使用することができる。本実施の形態でＦＬ４０の放電灯を点灯させたところ、チョークコイル５、９の２次巻線５ｂ、９ｂには正常点灯時に平均的に１６．５Ｖ_0-P（３３．０Ｖ_P-P）、寿命末期放電時に１９．０Ｖ_0-P（３８．０_P-P）程度の電圧が得られた。また、ピーク間電圧検出回路Ｐ１００におけるコンデンサ１５０のコンデンサ１５１に対する比率を大きくするとダイオード１５６のアノードに得られる電圧はその逆比で小さくなり、放電灯の正常点灯時と異常点灯時に得られる電圧の差もその逆比で小さくなることになる。
上記のＦＬ４０の放電灯の場合、正常点灯時と異常放電時の検出電圧差は５Ｖ_P-Pになるが、上記検出電圧差が上記のほぼ１／４程度を越えると、即ち、１．２Ｖ_P-P程度を越えると、保護回路Ｈ１００のツェナーダイオード６１などの部品を標準的な仕様品を選定したときに、そのツェナー電圧のバラツキ、周囲温度変動、保護回路Ｈ１００への外来ノイズ等に対して不安定となるので、上記検出電圧差が上記のほぼ１／４程度以下とするのが好ましい。
即ち、ピーク間電圧検出回路として、コンデンサの直列回路と一方のコンデンサに並列にダイオードを接続してなる構成の場合で、この回路をチョークコイルの２次巻線に設けるものにあっては、ピーク間電圧検出回路のダイオードと並列に接続されたコンデンサの容量を他方のコンデンサの容量のほぼ４倍以下にするのが好ましく、このようにすることで放電灯の正常点灯時と異常点灯時の識別を部品のバラツキ、周囲温度変動、外来ノイズ等に対して安定して行うことができる。
以上のように、ピーク間電圧検出回路Ｐ１００、Ｐ１１０の構成部品を耐圧の小さい、小型で安価な部品にすることができ、また、正常点灯時と異常点灯時の検出電圧の差を大きくすることができ、保護回路Ｈ１００を外部ノイズなどに対して充分な識別が可能なものにすることができる。
また、１灯が抜去した場合でも、２灯が全て装着されている場合と同一の条件で異常点灯状態を検出することができる。
また、部品のバラツキ、周囲温度変動、外来ノイズ等があっても、放電灯の正常点灯時と異常点灯時の識別を安定して行うことができる。
実施の形態２．
図２は、この発明の実施の形態２を示す放電灯点灯装置の回路図である。
図において、実施の形態１の図１と同一の部分には同一の符号を付し説明を省略する。
図において、放電灯負荷回路Ｌ１００において、３０は放電灯６とカップリングコンデンサ８との接続点にアノードが、直流電源１の正極にカソードが接続されたダイオード、３１は放電灯６とカップリングコンデンサ８との接続点にカソードが、直流電源１の負極にアノードが接続されたダイオードである。
３２及び３３は、放電灯負荷回路Ｌ１１０において、放電灯１００のダイオード３０及びダイオード３１に対応するダイオードである。
この構成において、放電灯６、１０の寿命末期等に放電灯６、１０の電流が減少してその等価インピーダンスが大きくなり、放電灯負荷回路Ｌ１００、Ｌ１１０の共振の鋭さが大きくなって、カップリングコンデンサ８、１２の両端電圧が直流電源１よりも増大したときに、各々ダイオード３０〜３３を介して直流電源１に還流することにより、放電灯負荷回路Ｌ１００、Ｌ１１０に生じる共振電圧の増大を抑制することができる。
また、実施の形態１と同様の効果がある。
実施の形態３．
図３は、この発明の実施の形態３を示す放電灯点灯装置の回路図である。
図において、実施の形態１の図１、実施の形態２の図２と同一の部分には同一の符号を付し説明を省略する。
図において、７０はコンデンサ１５１とチョークコイル５の２次巻線５ｂとの間に新たに挿入された抵抗、また、７１はコンデンサ１５４とチョークコイル９の２次巻線９ｂとの間に新たに挿入された抵抗である。
この構成において、抵抗７０及び７１はチョークコイル５、９の２次巻線５ｂ、９ｂのインダクタンス成分とピーク間電圧検出回路Ｐ１００、Ｐ１１０のコンデンサ成分とで放電灯負荷回路Ｌ１００、Ｌ１１０と異なる寄生発振が生じ、その電圧によってコンデンサ１５８の両端にサイリスタ６２を誤動作させる電圧が発生するのを抑制するための制動抵抗である。
そして、抵抗７０および７１を適当に選定すれば、ピーク間電圧検出回路Ｐ１００、Ｐ１１０の出力電圧にほとんど影響を与えること無く、チョークコイル５、９の２次巻線５ｂ、９ｂのインダクタンス成分とピーク間電圧検出回路Ｐ１００、Ｐ１１０のコンデンサ成分とによる寄生発振を抑制でき、放電灯の正常点灯時と異常放電時の検出電圧の差を大きくすることができ、保護回路Ｈ１００を外部ノイズなどで対してより充分な識別が可能なものにすることができる。
実施の形態４．
図４は、この発明の実施の形態４を示す放電灯点灯装置の回路図である。
本実施の形態は実施の形態３においてピーク間電圧検出回路Ｐ１１０を検出回路Ｐ１００と共用化して一つにしたものである。
図において、実施の形態１の図１、実施の形態２の図２と同一の部分には同一の符号を付し説明を省略する。
Ｐ１２０は共用のピーク間電圧検出回路であり、各々直列に接続されたコンデンサ１５０、１５１からなる直列回路、コンデンサ１５０に並列に接続されたダイオード１５２、コンデンサ１５１と２次巻線５ｂとの間に新たに挿入された抵抗７０、抵抗７０とコンデンサ１５１の接続点と２次巻線９ｂとの間に挿入された抵抗７１から構成される。
この構成において、ピーク間電圧検出回路Ｐ１２０の入力にはチョークコイル５、９の２次巻線５ｂ、９ｂに発生した電圧が抵抗７０及び７１を介して合成されるので、例えば、放電灯６が正常点灯、放電灯１０が寿命末期等の異常点灯状態になったとすると、ピーク間電圧検出回路Ｐ１２０からの出力としてダイオード１５６のアノードには正常点灯時と異常点灯時の合成したピーク間電圧が得られるので、ツェナーダイオード６１、抵抗６０及び抵抗５９を適当に選定すれば、全ての放電灯が正常点灯時には保護回路Ｈ１００が動作せず、放電灯６が正常点灯、放電灯１０が寿命末期等の異常点灯時にのみ保護回路Ｈ１００を動作させてインバータ回路の発振を停止させることができる。
また、放電灯６が寿命末期等の異常放電、放電灯１０が正常点灯になった場合、及び全ての放電灯が異常点灯状態になった場合も同様に保護回路Ｈ１００を動作させてインバータ回路の発振を停止させることができる。
また、ピーク間電圧検出回路を放電灯負荷回路Ｌ１００、Ｌ１１０に各々対応して設ける必要がないので小型で安価にすることができる。
【図面の簡単な説明】
第１図はこの発明の実施の形態１を示す放電灯点灯装置の回路図、第２図は、この発明の実施の形態２を示す放電灯点灯装置の回路図、第３図は、この発明の実施の形態３を示す放電灯点灯装置の回路図、第４図は、この発明の実施の形態４を示す放電灯点灯装置の回路図、第５図は従来の放電灯点灯装置の回路図、第６図は従来の放電灯点灯装置の直流電源の回路図である。Technical field
The present invention relates to a discharge lamp lighting device that lights a discharge lamp with high-frequency power from a self-excited inverter circuit, and can detect a lighting state with an inexpensive and small detection circuit to protect the circuit. About.
Technical background
FIG. 5 shows a circuit diagram of a conventional discharge lamp device. In the figure, 1 is a DC power source obtained from a commercial power source, 2 and 3 are switching elements composed of MOSFETs constituting an inverter circuit, and L100 and L110 are discharge lamp load circuits connected in parallel. The discharge lamp load circuit L100 includes a choke coil 5, a discharge lamp 6, a capacitor 7 connected in parallel to the discharge lamp 6, and a coupling capacitor 8.
The discharge lamp load circuit L110 includes a choke coil 9, a discharge lamp 10, a capacitor 11 connected in parallel to the discharge lamp 10, and a coupling capacitor 12.
Reference numeral 4 denotes a current transformer (hereinafter referred to as CT) connected between the connection point of the two switching elements 2 and 3 and the connection point of the parallel circuit of the discharge lamp load circuits L100 and L110, and its secondary windings 4a and 4b. Is connected between the gate and the source of the switching elements 2 and 3 via the resistor 13 and the resistor 14 so as to alternately turn on / off the switching elements 2 and 3 with the polarity shown in the figure (the primary winding of CT4). (Indicated by a broken line to represent the coupling between the line and the secondary winding).
In addition, illustration of the starting circuit for starting the equivalent diode and inverter which were built in parallel between the drain-source of the switching elements 2 and 3 is abbreviate | omitted.
P100 is a peak-to-peak voltage applied between the connection point a100 of the choke coil 5 and the discharge lamp 6 of the discharge lamp load circuit L100 and the negative electrode b100 of the DC power supply 1 (shown near the anode of the diode 52). A peak-to-peak voltage detection circuit P110 is a peak-to-peak voltage applied between the connection point a110 of the choke coil 9 and the discharge lamp 10 of the discharge lamp load circuit L110 and the negative electrode b110 of the DC power source 1 (shown near the anode of the diode 55). It is a peak-to-peak voltage detection circuit for detecting a voltage.
In the peak-to-peak voltage detection circuit P100, 50 and 51 are capacitors connected in series. One end of 50 is connected to the negative electrode of the DC power source 1 and the other end of 51 is connected to the connection point of the choke coil 5 and the discharge lamp 6. A diode 52 has an anode connected to the negative electrode of the DC power source 1 and a cathode connected to a connection point between the capacitor 50 and the capacitor 51.
With this configuration, the peak-to-peak voltage applied between the connection point a100 and the negative electrode b100 of the DC power supply 1 is taken out to the anode of the diode 56 at the inverse ratio of the capacitance values of the capacitor 51 and the capacitor 50.
In the peak-to-peak voltage detection circuit P <b> 110, 53 and 54 are capacitors connected in series. One end of 53 is connected to the negative electrode of the DC power source 1 and the other end of 54 is connected to the connection point between the choke coil 9 and the discharge lamp 10. A diode 55 has an anode connected to the negative electrode of the DC power source 1 and a cathode connected to a connection point between the capacitor 53 and the capacitor 54.
With this configuration, the peak-to-peak voltage applied between the connection point a <b> 110 and the negative electrode b <b> 110 of the DC power supply 1 is extracted to the anode of the diode 57 with the inverse ratio of the capacitance values of the capacitor 54 and the capacitor 53.
The cathodes of the diode 56 and the diode 57 are connected, and a capacitor 58 is connected between the connection point and the negative electrode of the DC power supply 1, and the higher one of the voltages between the peak-to-peak voltage detection circuits P100 and P110 is applied to both ends of the capacitor 58. The peak is detected as a DC voltage.
H100 is a protection circuit for protecting the circuit, and 61 is a Zener diode having a cathode connected to a connection point between the diodes 56 and 57, and is connected from the anode to the negative electrode of the DC power source 1 through the resistor 60 and the resistor 59. A thyristor 62 has a gate connected to a connection point between the resistor 60 and the resistor 59, and has a cathode connected to the negative electrode of the DC power supply 1 and an anode connected to the cathode of the diode 63. The anode of the diode 63 is connected to the gate of the switching element 3. In addition, the anode of the thyristor 63 is connected to the positive electrode of the DC power source 1 through the resistor 64.
In addition, the structural example of the DC power supply 1 in the case of obtaining DC power from commercial power is shown in FIG. As shown in the figure, the AC power output from the commercial power source 1a is configured to be full-wave rectified by the diode bridge 1b, smoothed by the smoothing capacitor 1c, and output to the load circuit as a DC power source. .
The operation of the conventional circuit shown in FIG. 5 will be described below.
In the figure, when the DC power source 1 is turned on, the switching elements 2 and 3 are alternately driven at a high frequency by a starting circuit (not shown), and the discharge lamp is turned on.
Here, for example, when the discharge lamp 6 reaches the end of its life due to exhaustion of the filament discharge material, the voltage across the discharge lamp 6 rises from that during normal lighting, and the voltage change is detected by the peak-to-peak voltage detection circuit P100. The anode voltage of the diode 56 increases, and the voltage of the capacitor 58 also increases. In addition, the Zener diode 61, the resistor 60, and the resistor 59 are appropriately selected, and the thyristor 62 is not turned on with the voltage of the capacitor 58 obtained when the discharge lamp 6 is normally lit, as in the end of the life of the discharge lamp. When the voltage rises, it is turned on by the voltage obtained in the capacitor 58. When the thyristor 62 is turned on, the current flowing from the secondary winding 4b of CT4 to the gate of the switching element 3 via the resistor 13 is bypassed via the diode 63 and the thyristor 62, so that the switching element 3 is turned off and the inverter Circuit oscillation stops.
Even when the oscillation stops, the holding current continues to flow through the resistor 64 through the resistor 64, so this state is maintained until the DC power supply 1 is turned off and then turned on again, so that the discharge lamp 6 continues abnormal discharge. It was possible to prevent driving in the state.
In addition, although the case where the discharge lamp 6 is not normal discharge was demonstrated above, when the discharge lamp 10 is not normal discharge and when any discharge lamp is not normal discharge, it is operated in the state which continued abnormal discharge similarly. Can be prevented.
However, in the above configuration, the voltage across the discharge lamps 6 and 10 is about 95V for the rapid start type fluorescent discharge lamp 40W and about 125V for the 32WHf discharge lamp when normally lit, and the voltage of the coupling capacitor is also about the discharge lamp 6. Since the voltage is about the same as the voltage at both ends of the circuit 10, parts constituting the peak-to-peak voltage detection circuits P100 and P110 are large and expensive.
Further, regarding the peak-to-peak voltage detection circuit P100, since the voltage between a100 and b100 is a high voltage, in order to apply this voltage to the gate of the thyristor 62, the capacitance ratio between the capacitor 51 and the capacitor 50 is appropriately selected. Thus, it is necessary to divide the high voltage between a100 and b100 at both ends of the capacitor 50, but the detection voltage obtained during normal lighting and abnormal lighting by dividing the voltage is also the same voltage dividing ratio. There is a problem that it becomes difficult to sufficiently identify external noise and the like.
The above also applies to the peak-to-peak voltage detection circuit P110. Further, since the voltage between a100 and b100 includes the voltage of the coupling capacitor 8 in addition to the voltage of the discharge lamp 6, there is a difference between the detected voltage when the discharge lamp 6 is normally lit and when it is abnormally lit. There was a problem that could not be obtained greatly.
The above also applies to the peak-to-peak voltage detection circuit P110. The combined current of the discharge lamp load circuits L100 and L110 flows through CT4. However, if one of the discharge lamps is removed due to a failure due to the life of the discharge lamp 6 or the discharge lamp 10, the current flowing through CT4 is Therefore, the secondary winding voltage of CT4 also decreases, and the driving voltage of the switching elements 2 and 3 decreases, whereby the oscillation frequency of the inverter circuit changes, so that the discharge lamp current mounted on the remaining discharge lamp load circuit is reduced. As a result, the voltage obtained in the peak-to-peak voltage detection circuits P100 and P110 also changes during normal lighting and abnormal lighting.
The present invention has been made to solve the above-described problems, and a first object of the present invention is to provide an inexpensive and small-sized device that does not require large and expensive components constituting the peak-to-peak voltage detection circuit. It is an object to provide a discharge lamp lighting device.
The second object of the present invention is that the difference in the output voltage of the peak-to-peak voltage detection circuit obtained during normal lighting and abnormal lighting has a sufficient margin against external noise, etc., and the operation reliability of the protection circuit is improved. It aims at providing a high discharge lamp lighting device.
Further, the third object of the present invention is that even if any of the plurality of discharge lamps is removed, the difference between the output voltages of the peak-to-peak voltage detection circuit for detecting the normal lighting state and the abnormal lighting state of the remaining discharge lamps. It is an object of the present invention to provide a discharge lamp lighting device capable of detecting an abnormal state under the same conditions without changing the difference in detection voltage when all the discharge lamps are mounted.
A fourth object of the present invention is to provide a difference between output voltages of a peak-to-peak voltage detection circuit that detects a normal lighting state and an abnormal lighting state of the remaining discharge lamps even if any of the plurality of discharge lamps is removed. A discharge lamp lighting device having a common peak-to-peak voltage detection circuit for a plurality of inexpensive and simple discharge lamps capable of obtaining a detection voltage substantially equal to the difference in detection voltage when all the discharge lamps are mounted The purpose is to provide.
Disclosure of the invention
A discharge lamp lighting device according to the present invention includes a DC power supply, an inverter circuit including a half bridge circuit having a pair of switching elements that convert a DC supplied from the DC power supply into a high-frequency current, and a high-frequency current from the inverter circuit. A discharge lamp lighting device comprising a plurality of discharge lamp load circuits connected in parallel, and each of the discharge lamp load circuits includes a choke coil, a discharge lamp, a series circuit of a coupling capacitor, and the discharge lamp. A pair of capacitors connected in parallel, each provided in the choke coil of each discharge lamp load circuit, each connected between the gate and source of the pair of switching elements via a current limiting element, and the pair of switching A secondary winding that outputs a voltage for driving the element, and one secondary winding of each of the pair of secondary windings. A series circuit of a capacitor each connected in series to the end, Connected in series Consisting of a diode connected in parallel to one of the capacitors, The capacitance of the one capacitor connected in parallel with the diode is set to be not more than four times the capacitance of the other capacitor, and A plurality of peak-to-peak detections for detecting a peak-to-peak voltage generated in one of the secondary windings by an inverse ratio of the capacitance of the other capacitor in the series circuit of the capacitors and the one capacitor connected in parallel with the diode When the voltage detected by the circuit and the voltage detected by the plurality of peak-to-peak voltage detection circuits exceeds a predetermined value, the oscillation of the inverter circuit is stopped. , Keep it stopped A protective circuit I got Is. As a result, the component parts of the peak-to-peak voltage detection circuit can be made small and inexpensive.
In addition, the output voltage of the peak-to-peak voltage detection circuit must have a sufficient margin for the difference between the peak-to-peak voltage detection voltages obtained during normal lighting and abnormal lighting, due to external noise, etc. Can do.
In addition, since each discharge lamp load circuit and peak-to-peak voltage detection circuit are provided independently, even when any discharge lamp is removed, the abnormal lighting state is maintained under the same conditions as when all the discharge lamps are installed. Can be detected.
Further, even when there are component variations, ambient temperature fluctuations, external noise, etc., it is possible to stably identify when the discharge lamp is normally lit and when it is abnormally lit.
The peak-to-peak voltage detection circuit includes a resistor inserted between the connected secondary winding and the capacitor. As a result, parasitic oscillation due to the inductance component of the secondary winding of the choke coil and the capacitor component of the peak-to-peak voltage circuit can be suppressed, and the difference between the detection voltage during normal lighting and abnormal discharge of the discharge lamp can be increased. it can.
In addition, an inverter circuit composed of a half-bridge circuit having a DC power supply and a pair of switching elements that convert a DC supplied from the DC power supply into a high-frequency current, and a discharge lamp is lit by the high-frequency current from the inverter circuit, In the discharge lamp lighting device comprising a discharge lamp load circuit connected in parallel, each of the discharge lamp load circuits includes a series circuit of a choke coil, a discharge lamp, a coupling capacitor, and a capacitor connected in parallel to the discharge lamp. ,
A pair of choke coils provided in each of the discharge lamp load circuits is connected between the gates and sources of the pair of switching elements via current limiting elements, and outputs a voltage for driving the pair of switching elements. A series circuit of a secondary winding, a resistor and two capacitors connected in series to both ends of one secondary winding of a pair of secondary windings of each of the pair of secondary windings; , Connected in series A diode connected in parallel to one capacitor of the capacitor, one end of one secondary winding of the other pair of secondary windings, a resistor connected to the resistor of the series circuit and the connection point of the capacitor And consist of The capacitance of the one capacitor connected in parallel with the diode is made to be not more than four times the capacitance of the other capacitor, A common peak-to-peak detection circuit for detecting a peak-to-peak voltage generated in the one secondary winding by an inverse ratio of the capacitance of the other capacitor of the series circuit and the one capacitor connected in parallel with the diode; When the voltage detected by the peak-to-peak voltage detection circuit exceeds a predetermined value, the oscillation of the inverter circuit is stopped. , Keep it stopped A protective circuit I got Is. Accordingly, it is not necessary to provide a plurality of peak-to-peak voltage detection circuits corresponding to the discharge lamp load circuit, so that the size and the cost can be reduced.
Further, since it is not necessary to provide a plurality of peak-to-peak voltage detection circuits corresponding to the discharge lamp load circuit, it can be made small and inexpensive.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
1 is a circuit diagram of a discharge lamp lighting device showing Embodiment 1 of the present invention.
In the figure, 1 is a DC power source obtained from a commercial power source, 2 and 3 are switching elements composed of MOSFETs constituting an inverter circuit, and L100 and L110 are discharge lamp load circuits connected in parallel. The discharge lamp load circuit L100 includes a choke coil 5, a discharge lamp 6, a capacitor 7 connected in parallel to the discharge lamp 6, and a coupling capacitor 8.
The discharge lamp load circuit L110 includes a choke coil 9, a discharge lamp 10, a capacitor 11 connected in parallel to the discharge lamp 10, and a coupling capacitor 12.
The choke coils 5 and 9 of the discharge lamp load circuits L100 and L110 are each provided with two secondary windings 5a, 5b, 9a and 9b, and the secondary windings have switching polarities shown and marked with the switching elements 2 and 3 Are connected between the gate and the source via the resistors 13 and 15 and the resistors 14 and 16 so as to be alternately turned ON / OFF. (In order to represent the coupling between the primary winding and the secondary winding of the choke coils 5 and 9, they are shown by a dashed line and a broken line.)
In addition, illustration of the starting circuit for starting the equivalent diode and inverter which were built in parallel between the drain-source of the switching elements 2 and 3 is abbreviate | omitted.
Here, when the discharge lamp 6 and the discharge lamp 10 have the same rated output, the circuit constants of the discharge lamp load circuits L100 and L110 are selected to be equal.
When the rated outputs of the discharge lamp 6 and the discharge lamp 10 are different, the resonance frequencies when the discharge lamp load circuits L100 and L110 are turned on are approximately equal, and the secondary windings of the choke coils 5 and 9 are turned on. Set so that the voltages are approximately equal.
P100 is a peak-to-peak voltage detection circuit for detecting a peak-to-peak voltage generated in the secondary winding 5b of the choke coil 5 of the discharge lamp load circuit L100. P110 is a peak-to-peak voltage detection circuit. This is a peak-to-peak voltage detection circuit that detects a peak-to-peak voltage generated in the secondary winding 9 b of the choke coil 9.
In the peak-to-peak voltage detection circuit P100, 150 and 151 are capacitors connected in series. One end of the capacitor 150 is connected to the negative electrode of the DC power source 1, and the other end of 151 is connected to the secondary winding 5b of the choke coil 5 and the resistor 13. Connected to a point.
A diode 152 has an anode connected to the negative electrode of the DC power supply 1 and a cathode connected to a connection point between the capacitor 150 and the capacitor 151.
With this configuration, the peak-to-peak voltage between the secondary windings of the choke coil 5 is extracted to the anode of the diode 156 at the inverse ratio of the capacitance values of the capacitor 151 and the capacitor 150.
In the peak-to-peak voltage detection circuit P110, 153 and 154 are capacitors connected in series. One end of the 153 is connected to the negative electrode of the DC power source 1 and the other end of the 154 is connected to the connection point between the secondary winding of the choke coil 9 and the resistor 15. Is done.
A diode 155 has an anode connected to the negative electrode of the DC power supply 1 and a cathode connected to a connection point between the capacitor 153 and the capacitor 154.
With this configuration, the peak-to-peak voltage of the secondary winding of the choke coil 9 is extracted to the anode of the diode 157 at the inverse ratio of the capacitance values of the capacitors 154 and 153.
The cathodes of the diode 156 and the diode 157 are connected, and a capacitor 158 is connected between the connection point and the negative electrode of the DC power supply 1, and the higher one of the voltages between the peak-to-peak voltage detection circuits P100 and P110 is connected across the capacitor 158. The peak is detected as a DC voltage.
H100 is a protection circuit that stops the oscillation of the inverter circuit when the voltages detected by the peak-to-peak voltage detection circuits P100 and P110 exceed a predetermined value, and 61 is a cathode at the connection point of the diodes 156 and 157. The connected Zener diode is connected from the anode to the negative electrode of the DC power source 1 through the resistor 60 and the resistor 59. Reference numeral 62 denotes a thyristor having a gate connected to a connection point between the resistor 60 and the resistor 61, a cathode connected to the negative electrode of the DC power supply 1, and an anode connected to the cathode of the diode 63. The anode of the diode 63 is connected to the gate of the switching element 3. In addition, the anode of the thyristor 63 is connected to the positive electrode of the DC power source 1 through the resistor 64.
Hereinafter, the operation of the discharge lamp lighting device according to Embodiment 1 of the present invention will be described with reference to FIG.
In FIG. 1, when the DC power source 1 is turned on, the switching elements 2 and 3 are alternately driven at a high frequency by a starting circuit not shown, and the discharge lamps 6 and 10 are turned on.
Here, for example, when the discharge lamp 6 reaches the end of its life due to exhaustion of the discharge material of the filament, the voltage across the discharge lamp 6 rises from that during normal lighting, and the voltage across the choke coil 5 also rises. The change in voltage is detected by the peak-to-peak voltage detection circuit P100 provided in the secondary winding 5b of the choke coil 5, the anode voltage of the diode 156 increases, and the voltage of the capacitor 158 also increases.
In addition, the Zener diode 61, the resistor 60, and the resistor 59 of the protection circuit H100 are appropriately selected, and the thyristor 62 is not turned on with the voltage of the capacitor 158 obtained when the discharge lamps 6 and 10 are normally lit. When the voltage rises at the end of the life of the capacitor 158, it is turned on by the voltage obtained in the capacitor 158.
If the thyristor 62 is turned on, the current flowing from the secondary windings 5b and 9b of the choke coils 5 and 9 to the gate of the switching element 3 via the resistors 13 and 15 is bypassed via the diode 63 and the thyristor 62. The switching element 3 is turned OFF and the oscillation of the inverter circuit is stopped.
Even if the oscillation stops, the holding current continues to flow through the resistor 64 through the resistor 64. Therefore, this state is maintained until the DC power supply 1 is turned off and then turned on again, so that the discharge lamp 6 continued abnormal discharge. It is possible to prevent driving in a state.
In addition, although the case where the discharge lamp 6 is not normal discharge was demonstrated above, when the discharge lamp 10 is not normal discharge and when any discharge lamp is not normal discharge, it is operated in the state which continued abnormal discharge similarly. Can be prevented.
Here, the voltages of the secondary windings 5b and 9b of the choke coils 5 and 9 may be selected so as to obtain a voltage larger than the threshold voltage between the gate and the source of the switching element 3, as in the conventional example of FIG. The peak-to-peak voltage detection circuits P100 and P110 can be selected to be sufficiently smaller than those provided between a100 and b100 and a110 and b110, respectively. The components of the peak-to-peak voltage detection circuits P100 and P110 are small and inexpensive parts with a low withstand voltage. Can be used.
Further, in the peak-to-peak voltage detection circuit P100, the voltage of the secondary winding 5b of the choke coil includes the voltage component of the coupling capacitor 8 that has a small voltage change during normal lighting and abnormal lighting of the discharge lamp 6. Therefore, a large difference in detection voltage between normal lighting and abnormal lighting can be obtained, and the protection circuit H100 can be sufficiently distinguished from external noise or the like.
The above also applies to the peak-to-peak voltage detection circuit P110.
Even if one of the discharge lamps is removed due to a failure due to the life of the discharge lamp 6 or the discharge lamp 10, the discharge lamp load circuits L110 and L110 are independent, and the secondary winding of the choke coil Since the peak-to-peak voltage detection circuits P100 and P110 for detecting the peak-to-peak voltage at the time of normal lighting and abnormal lighting of the discharge lamps generated in 5b and 9b are also provided independently, It is possible to detect an abnormal lighting state under the same conditions as when all are mounted.
By the way, when the switching element 3 is constituted by a MOSFET, the reverse withstand voltage between the gate and the source is about 20 V to 30 V or less in a standard product that is generally easily available. If the voltage obtained at the secondary windings 5b and 9b is selected to be smaller than the reverse withstand voltage between the gate and source, it is possible to use an inexpensive and easily available standard product as the MOSFET of the switching element 3. it can. In this embodiment, when the discharge lamp of FL40 is turned on, the secondary windings 5b and 9b of the choke coils 5 and 9 have an average of 16.5V when normally lit. _0-P (33.0V _PP ), 19.0V at the end of life discharge _0-P (38.0 _PP ) About a voltage was obtained. Further, when the ratio of the capacitor 150 to the capacitor 151 in the peak-to-peak voltage detection circuit P100 is increased, the voltage obtained at the anode of the diode 156 is reduced by the inverse ratio, and the difference between the voltages obtained when the discharge lamp is normally lit and abnormally lit. Is also reduced by the inverse ratio.
In the case of the above-mentioned FL40 discharge lamp, the detected voltage difference between normal lighting and abnormal discharge is 5V. _PP However, when the detected voltage difference exceeds about 1/4 of the above, that is, 1.2V. _PP Exceeding a certain level, when a standard specification product such as the Zener diode 61 of the protection circuit H100 is selected, it is unstable against variations in the Zener voltage, ambient temperature fluctuations, external noise to the protection circuit H100, etc. Therefore, it is preferable that the detected voltage difference is about ¼ or less of the above.
That is, the peak-to-peak voltage detection circuit has a configuration in which a diode is connected in parallel to a series circuit of capacitors and one capacitor, and this circuit is provided in the secondary winding of the choke coil. It is preferable that the capacity of the capacitor connected in parallel with the diode of the inter-voltage detection circuit is less than about 4 times the capacity of the other capacitor, so that the discharge lamp can be distinguished between normal lighting and abnormal lighting. Can be stably performed against component variations, ambient temperature fluctuations, external noise, and the like.
As described above, the components of the peak-to-peak voltage detection circuits P100 and P110 can be made small and inexpensive with low withstand voltage, and the difference in detection voltage between normal lighting and abnormal lighting can be increased. The protection circuit H100 can be sufficiently identified against external noise and the like.
Even when one light is removed, the abnormal lighting state can be detected under the same conditions as when all the two lights are mounted.
Further, even when there are component variations, ambient temperature fluctuations, external noise, etc., it is possible to stably identify when the discharge lamp is normally lit and when it is abnormally lit.
Embodiment 2. FIG.
FIG. 2 is a circuit diagram of a discharge lamp lighting device showing Embodiment 2 of the present invention.
In the figure, the same reference numerals are given to the same parts as those in FIG.
In the figure, in the discharge lamp load circuit L100, 30 is a diode in which an anode is connected to the connection point between the discharge lamp 6 and the coupling capacitor 8, and a cathode is connected to the positive electrode of the DC power source 1. 31 is the discharge lamp 6 and the coupling capacitor. 8 is a diode in which a cathode is connected to a connection point to 8 and an anode is connected to the negative electrode of the DC power supply 1.
Reference numerals 32 and 33 denote diodes corresponding to the diode 30 and the diode 31 of the discharge lamp 100 in the discharge lamp load circuit L110.
In this configuration, the current of the discharge lamps 6 and 10 decreases at the end of the life of the discharge lamps 6 and 10 and the equivalent impedance increases, and the sharpness of the resonance of the discharge lamp load circuits L100 and L110 increases. When the voltage across the capacitors 8 and 12 increases from the DC power source 1, the increase in the resonance voltage generated in the discharge lamp load circuits L 100 and L 110 is suppressed by returning to the DC power source 1 via the diodes 30 to 33. can do.
In addition, the same effect as in the first embodiment is obtained.
Embodiment 3 FIG.
FIG. 3 is a circuit diagram of a discharge lamp lighting device showing Embodiment 3 of the present invention.
In the figure, the same parts as those in FIG. 1 of the first embodiment and FIG.
In the figure, 70 is a resistor newly inserted between the capacitor 151 and the secondary winding 5b of the choke coil 5, and 71 is newly inserted between the capacitor 154 and the secondary winding 9b of the choke coil 9. Inserted resistance.
In this configuration, the resistors 70 and 71 are parasitic oscillations different from those of the discharge lamp load circuits L100 and L110 due to the inductance components of the secondary windings 5b and 9b of the choke coils 5 and 9 and the capacitor components of the peak-to-peak voltage detection circuits P100 and P110. This is a braking resistor for suppressing the occurrence of a voltage that causes the thyristor 62 to malfunction at both ends of the capacitor 158 due to the voltage.
If the resistors 70 and 71 are appropriately selected, the inductance components and the peaks of the secondary windings 5b and 9b of the choke coils 5 and 9 are hardly affected with little influence on the output voltages of the peak-to-peak voltage detection circuits P100 and P110. Parasitic oscillation due to the capacitor components of the inter-voltage detection circuits P100 and P110 can be suppressed, the difference in detection voltage between the normal lighting and abnormal discharge of the discharge lamp can be increased, and the protection circuit H100 can be protected against external noise. It is possible to make the identification more sufficient.
Embodiment 4 FIG.
FIG. 4 is a circuit diagram of a discharge lamp lighting device according to Embodiment 4 of the present invention.
In this embodiment, the peak-to-peak voltage detection circuit P110 is shared with the detection circuit P100 in the third embodiment, and is combined into one.
In the figure, the same parts as those in FIG. 1 of the first embodiment and FIG.
P120 is a common peak-to-peak voltage detection circuit, which is a series circuit composed of capacitors 150 and 151 connected in series, a diode 152 connected in parallel to the capacitor 150, and between the capacitor 151 and the secondary winding 5b. The resistor 70 is newly inserted, and the resistor 71 is inserted between the connection point of the resistor 70 and the capacitor 151 and the secondary winding 9b.
In this configuration, the voltage generated in the secondary windings 5b and 9b of the choke coils 5 and 9 is synthesized via the resistors 70 and 71 at the input of the peak-to-peak voltage detection circuit P120. If the normal lighting and the discharge lamp 10 are in an abnormal lighting state such as the end of life, the combined peak-to-peak voltage during normal lighting and abnormal lighting is obtained at the anode of the diode 156 as an output from the peak-to-peak voltage detection circuit P120. Therefore, if the Zener diode 61, the resistor 60, and the resistor 59 are appropriately selected, the protection circuit H100 does not operate when all the discharge lamps are normally lit, the discharge lamp 6 is normally lit, and the discharge lamp 10 is at the end of its life. It is possible to stop the oscillation of the inverter circuit by operating the protection circuit H100 only at the time of abnormal lighting.
Similarly, when the discharge lamp 6 is abnormally discharged at the end of its life, when the discharge lamp 10 is normally lit, and when all the discharge lamps are abnormally lit, the protection circuit H100 is operated in the same manner. Oscillation can be stopped.
Further, since it is not necessary to provide a peak-to-peak voltage detection circuit corresponding to each of the discharge lamp load circuits L100 and L110, it can be made small and inexpensive.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a discharge lamp lighting device according to Embodiment 1 of the present invention, FIG. 2 is a circuit diagram of a discharge lamp lighting device according to Embodiment 2 of the present invention, and FIG. FIG. 4 is a circuit diagram of a discharge lamp lighting device showing a fourth embodiment of the present invention, and FIG. 5 is a circuit diagram of a conventional discharge lamp lighting device. FIG. 6 is a circuit diagram of a DC power source of a conventional discharge lamp lighting device.

Claims

An inverter circuit composed of a DC power supply and a half-bridge circuit having a pair of switching elements that convert the DC supplied from the DC power supply into a high-frequency current, and a plurality of parallel connections are made by lighting a discharge lamp by the high-frequency current from the inverter circuit In the discharge lamp lighting device comprising the discharge lamp load circuit,
Each discharge lamp load circuit includes a choke coil, a discharge lamp, a series circuit of a coupling capacitor, and a capacitor connected in parallel to the discharge lamp,
A pair of choke coils provided in each of the discharge lamp load circuits is connected between the gates and sources of the pair of switching elements via current limiting elements, and outputs a voltage for driving the pair of switching elements. The next winding,
A series circuit of capacitors connected in series to both ends of one secondary winding of each of the pair of secondary windings; a diode connected in parallel to one capacitor of the capacitors connected in series ; And the capacitance of the one capacitor connected in parallel with the diode is set to be not more than four times the capacitance of the other capacitor, and the peak-to-peak voltage generated in the one secondary winding is A plurality of peak-to-peak detection circuits that detect a reverse ratio of the capacitance of the other capacitor in the series circuit and the one capacitor connected in parallel with the diode;
A protection circuit that stops the oscillation of the inverter circuit and maintains the stopped state when a voltage obtained by wired-ORing voltages detected by the plurality of peak-to-peak voltage detection circuits exceeds a predetermined value;
The discharge lamp lighting device comprising the Ruco equipped with.

2. The discharge lamp lighting device according to claim 1, wherein the peak-to-peak voltage detection circuit includes a resistor inserted between the secondary winding to be connected and the capacitor.

An inverter circuit composed of a DC power supply and a half-bridge circuit having a pair of switching elements that convert the DC supplied from the DC power supply into a high-frequency current, and a plurality of parallel connections are made by lighting a discharge lamp by the high-frequency current from the inverter circuit In the discharge lamp lighting device comprising the discharge lamp load circuit,
Each discharge lamp load circuit includes a choke coil, a discharge lamp, a series circuit of a coupling capacitor, and a capacitor connected in parallel to the discharge lamp,
A pair of choke coils provided in each of the discharge lamp load circuits is connected between the gates and sources of the pair of switching elements via current limiting elements, and outputs a voltage for driving the pair of switching elements. The next winding,
Of the pair of secondary windings, a series circuit of a resistor and two capacitors connected in series to both ends of one secondary winding of one pair of secondary windings is connected in series. The diode connected in parallel to one capacitor of the capacitor, one end of one secondary winding of the other pair of secondary windings, the resistor of the series circuit and the connection point of the capacitor And the capacitance of the one capacitor connected in parallel with the diode is less than four times the capacitance of the other capacitor, and the peak-to-peak voltage generated in the one secondary winding is reduced to the series circuit. A common peak-to-peak detection circuit that detects a reverse ratio of the capacitance of the other capacitor and the one capacitor connected in parallel with the diode;
A protection circuit for stopping the oscillation of the inverter circuit and maintaining the stopped state when the voltage detected by the peak-to-peak voltage detection circuit exceeds a predetermined value;
The discharge lamp lighting device comprising the Ruco equipped with.