JP4706148B2 - Discharge lamp lighting device - Google Patents

Description

【００２１】
そしてこの電圧をフィラメント電圧検知回路１２で検知することにより放電ランプ１３の異常を検知できる。
【００２２】
一方、放電ランプ１３の放電の始動時にはインバータ回路部１００の発振周波数を予熱時の周波数である１５０ＫＨｚから下げていき、負荷回路用の共振周波数に近づけることにより、放電ランプ１３への印加電圧が高くなり、点灯に必要な電圧を超えた時点で放電ランプ１３は点灯始動することが出来る。また、この時、インバータ回路部１００の周波数が下がることによりフィラメント電圧検知回路１２の電圧は予熱時の共振条件から外れていくので、フィラメント１４、１５の両端に印加される電圧も降下し、フィラメント電流も予熱時よりも下がる。
【００２３】
また、始動後にはインバータ回路の発振周波数を適宜に設定することで、負荷回路用の共振回路の共振特性を利用して放電ランプ１３への印加電圧を変化させることができ、放電ランプ１３を定格点灯させたり、調光点灯させたりすることが可能である。
【００２４】
次に、放電ランプの異常の一種であるフィラメントの断線或いは、断線しているがフィラメント電極のエミッタ材料がフィラメント１３、１４に付着してフィラメント両端の抵抗値が正常時よりも大きくなった状態を検出するフィラメント検知回路１２の動作を説明する。
【００２５】
フィラメント電圧検知回路１２の入力電圧は、予熱共振回路とフィラメント予熱用トランスとの接続点であるの電圧を検知している。即ち、コイルＬ２とトランスＴ１の接続点であるテストポイントＴＰ１１の電圧である。ＴＰ１１には、（数１）に示される電圧が得られるが、フィラメントが断線しているがフィラメント電極のエミッタ材料がフィラメントに付着すると、断線していない正常時のフィラメント両端の抵抗値より大きくなり、即ち、（数１）中のＲが大きくなり、結果として、フィラメント検知電圧Ｖｄが正常時より大きくなり、この検知電圧Ｖｄを測定してフィラメントの異常状態を検知するものである。
【００２６】
図２は、フィラメント検知回路１２の具体的な回路例を示す。フィラメント電圧検知回路は入力ＴＰ１１につながるコンデンサＣ１１と、それに直列につながるコンデンサＣ１２と、コンデンサＣ１１とＣ１２の中点からダイオードＤ１１のカソードに接続され、ダイオードＤ１１とアノード共通接続のＤ１２が接続される。ダイオードＤ１２には並列にコンデンサＣ１３がつながっており、ダイオードＤ１１のアノードには定電圧ダイオードＤ１３と抵抗Ｒ１１を介してトランジスタＱ１２のベースにつながっており、トランジスタＱ１２のベース・エミッタ間には抵抗Ｒ１４を挿入しており、コレクタのプルアップ抵抗Ｒ１５とでフィラメント検知回路１２の出力端子であるＴＰ１３に出力される。また、Ｄ１３のアノードには定電圧ダイオードＤ１４と抵抗Ｒ１２を介してトランジスタＱ１１のベースにつながっており、トランジスタＱ１１のベース・エミッタには抵抗Ｒ１３がつながる。また、トランジスタＱ１１のコレクタはトランジスタＱ１２のベースにつながっている。
【００２７】
このフィラメント電圧検出回路の動作を説明する。ＴＰ１１に発生した交流電圧はコンデンサＣ１１とＣ１２で分圧され、ダイオードＤ１１、Ｄ１２とＣ１３で倍電圧整流される。定電圧ダイオードＤ１３、Ｄ１４はツェナー電圧は異なる電圧値に設定し、定電圧ダイオードＤ１３は放電ランプ１３の正常点灯時にトランジスタＱ１２がオンする所定の定電圧とし、定電圧ダイオードＤ１４はフィラメントが断線したときにトランジスタＱ１１がオンする所定の定電圧に設定する。このように、フィラメントが断線したときには、正常時よりも高い電圧がＴＰ１１に入力されるので、Ｄ１４とＤ１３のツェナー電圧を異なる電圧のものを使用する他に、同じツェナー電圧のダイオードを利用して抵抗Ｒ１１とＲ１４、Ｒ１２とＲ１４の分圧を変えてトランジスタＱ１２とＱ１１への所定の電圧を得ることも可能である。これにより放電ランプが正常点灯時にはフィラメント検知回路１２の出力ＴＰ１３はＬ出力となり、フィラメント断線等の異常時にはトランジスタＱ１１がオンすることにより、トランジスタＱ１２がオフするので、フィラメント電圧検知回路１２の出力はＨ出力となる。また、放電ランプ点灯装置のいずれかの回路の異常によりフィラメント検知回路１２の入力端子ＴＰ１１に信号が無かった場合には、トランジスタＱ１２がオフするので保護回路出力ＴＰ１３はＬとなり異常時と同じ動作となり、何等かの異常状態を検知できる。
【００２８】
また、ダイオードＤ１１のアノード以降の回路を複数に並列に設け、それぞれの検知出力をインバータ制御回路の停止や、昇圧アクティブフィルタ制御回路１０の停止に利用できるように構成することができる。例えば、インバータの制御回路１１にマイコンを用いている場合には、フィラメント検知回路１２で異常を検出したらまずマイコンの動作を停止させる。マイコンが暴走した場合などを考慮して、マイコンの動作停止からさらに遅延時間を設けて昇圧アクティブフィルタ制御回路１０を停止させる等の動作を行うことができ、安全性、信頼性をより高くすることが出来る。
【００２９】
なお、図１に示す回路では、昇圧アクティブフィルタ制御回路１０内のアクティブフィルタの動作を停止させた場合には、昇圧動作が停止するために、コンデンサＣ１の直流電圧が商用交流電源の整流電圧に下がるために、放電ランプを点灯しつづけるための電圧が確保出来ず、放電ランプは消灯する。即ち、フィラメント検知回路１２の検知出力で昇圧アクティブフィルタ制御回路１０の動作を停止させることによっても、放電ランプ１３の放電を停止させことができる。
【００３０】
（実施の形態２）
本発明の他の実施の形態を図３を用いて説明する。図１に示した実施の形態１と異なるのは、フィラメント電圧を検知するのではなく、放電ランプ１３の両端にかかる電圧を検知している点である。図３において、カップリングコンデンサＣ３に並列に抵抗Ｒ２１と、コンデンサＣ３と共振回路のコイルＬ３の接続点の電圧を抵抗Ｒ２２とＲ２３で分圧し、コンデンサＣ２５と抵抗Ｒ２４からなるローパスフィルタを介してトランジスタＱ２４に接続している。直流成分を遮断するためのコンデンサＣ３に並列に抵抗Ｒ２１を接続しているので、Ｒ２２とＲ２３の接続点には矩形波と若干の直流成分の合成電圧が出てくる。その合成電圧がコンデンサＣ２５と抵抗Ｒ２５からなるローパスフィルタで直流電圧に変換し、トランジスタＱ２４のベース・エミッタ間に印加される。
【００３１】
正常な放電ランプ１３を接続した場合には、放電ランプの放電電流が増加すると放電ランプのランプ電圧が減少していくという負性抵抗特性を示すので、負荷用共振回路のコンデンサＣ４の両端に発生する電圧は、点灯時は放電開始時のランプ電圧から減少し正常な放電状態では、所定のランプ電圧に維持される。この正常放電時にはトランジスタＱ２４のベース・エミッタ間の電圧がオンしない電圧に設定する。点灯開始時には、インバータ回路制御回路１１で、インバータ回路部１００の出力周波数は１５０ＫＨｚから減少していき、又、放電ランプの不正抵抗特性により、ランプ電圧が高くなっていき放電ランプが点灯するが、それまでは、Ｑ２４はオンしない。即ち、点灯開始時から正常点灯状態では、Ｑ２４のコレクタはＨレベルであり、放電ランプが開放状態となったり、インバータ回路部１１や昇圧アクティブ回路部２００などが異常状態になり、コンデンサＣ４の両端に発生する電圧が所定の電圧を越えるとＱ２４がオンする。従って、このＱ２４に印加される電圧を監視してランプ電圧の異常を検知するのである。すなわち、点灯開始時の数秒間とそれ以後のＱ２４からの出力をインバータ制御回路１１で比較監視することによりランプ電圧の異常状態を検知することができる。
【００３２】
また、放電ランプの電極のエミッタが両方とも無くなった時や、放電ランプが器具から抜かれたときには、安定放電状態時の放電ランプ１３の両端抵抗より大きくなるので、共振コンデンサＣ４の両端の電圧を所定の電圧に維持する抵抗がなくなるために、ランプ電圧が上昇し、トランジスタＱ２４がオンする。このＱ２４のコレクタ出力信号でインバータ制御回路１１で制御することにより、放電ランプの電極のエミッタが両方とも無くなった時や、放電ランプが器具から抜かれたときに発生する共振コンデンサＣ４の両端の電圧が高い状態で持続するのを防ぐとともに、インバータ回路１１のスイッチングトランジスタＱ２、Ｑ３や、コンデンサＣ３、コイルＬ３へ印加される高電圧を抑えそれらの電子部品へのストレスを抑えることが出来る。
【００３３】
（実施の形態３）
次に、実施の形態３を図４、図５を用いて説明する。図４において、インバータ回路部１００のスイッチングトランジスタＱ３のソースに抵抗Ｒ３１と、その両端に発生する電圧がベースエミッタ間に発生する電圧でオン・オフするトランジスタＱ３１とそのベース抵抗Ｒ３２からなる。スイッチングトランジスタＱ３に流れる電流によりソース抵抗Ｒ３１の両端に発生する電圧がトランジスタＱ３１のベースエミッタ間電圧以上になるとトランジスタＱ３１がオンし、スイッチングトランジスタＱ３のゲート電位をＬにするので、スイッチングトランジスタＱ３へ規定電圧以上の異常電圧が印加されなくすることができトランジスタ等の電子部品へのストレスを軽減することができる。
【００３４】
この動作を図５のインバータ電圧出力波形を用いて説明する。正常点灯時は、図５（ａ）のパルス波形Ａに示す様に、約７０ＫＨｚのデューティー比が約５０％のパルス出力がインバータ出力の電圧波形である。何らかの原因で、インバータ出力電圧が高くなると、インバータ回路１００に流れる電流が増加し、Ｑ３１のベースに印加される電圧が閾値Ｔｈを越え、パルス波形図５（ｂ）に示す様に閾値Ｔｈ以上の電圧の時にＱ３のゲートに印加される電圧がＬレベルに落ちて、Ｑ３をオフする。そして、インバータ回路１００の出力が、図５（ａ）の実線の波形Ｂのように、デューティ比の小さいパルス波形となり、負荷用共振回路へ入力される矩形波のデューティー比が異なるために負荷用共振回路の共振条件から外れ、コンデンサＣ４の両端に発生する電圧は抑制される。従って、過大な電圧が共振回路のコイルＬ３、コンデンサＣ４などに印加されないので、電子部品へのストレスが軽減され、耐電圧の小さな小型部品を使うことが出来る。
【００３５】
（実施の形態４）
実施の形態４を図６を用いて説明する。図６において、トランジスタＱ３１のコレクタから抵抗Ｒ４５を介してトランジスタＱ４１のベースにつながっており、トランジスタＱ４１のベース・エミッタ間には抵抗Ｒ４１が接続される。また、トランジスタＱ４１のコレクタには抵抗Ｒ４３とＲ４４で分圧してトランジスタＱ４２のベースが接続される。トランジスタＱ４２のコレクタには抵抗Ｒ４２を介してトランジスタＱ４１のベースを接続することにより、ラッチ回路を構成している。このラッチ回路の電源としてＴＰ４１には直流電源が接続される。トランジスタＱ４２のコレクタにはダイオード４１のカソードが接続してあり、アノードはスイッチングトランジスタＱ３のゲートに接続される。
本回路の動作としては、過電流検出のトランジスタＱ３１が一端オンすると、トランジスタＱ４１のベース・エミッタ間の抵抗Ｒ４１の両端に電圧が発生し、トランジスタＱ４１はオンする。それにより抵抗Ｒ４３に電流が流はじめ、Ｒ４４の両端に電圧が発生し、トランジスタＱ４２はオンする。トランジスタＱ４２がオンすることにより、トランジスタＱ４１がオン条件を維持するためのベース電流がＲ４２に流れるのでＴＰ４１に直流電源がある限りトランジスタＱ４１はオンを維持する。それによりＴＰ４１からの逆流防止のダイオードＤ４１を介して、スイッチングトランジスタＱ３のゲート電圧をＬに維持しつづける。即ち、一旦異常電圧を検出すると、Ｑ３がオフとなりインバータ出力が停止するもことになる。
【００３６】
これにより、インバータ回路部１００の動作は停止し、スイッチングトランジスタＱ３へのストレスが軽減されるとともに、過電流が流れるとインバータ回路１１が停止するので、共振回路のコイルＬ３、コンデンサＣ４へのストレスも軽減されるので、小さな部品を使うことが出来る。
【００３７】
【発明の効果】
以上のように、本発明の放電ランプ点灯装置によれば、入力される直流電圧をアクティブフィルタ方式の昇圧アクティブフィルタ回路で高圧を発生する構成のため、大型の昇圧トランスを使用することなく、フィラメント予熱の比較的小型のトランスを利用してフィラメントへの予熱電流の供給と異常の検出ができるので装置の小型化がはかれる。
【００３８】
また、多重の保護回路を設けることにより、インバータ回路の動作停止と昇圧アクティブフィルタ回路の動作停止などの多段階異常の保護動作を構成して、信頼性の高い保護回路を提供できる。
【００３９】
また、カップリングコンデンサと共振回路のコイルの中点に発生する直流電圧が、正常な放電ランプが接続されている場合には、放電ランプの抵抗値により所定の電圧値に規定されるが、放電ランプが開放された場合には高くなり、簡易な回路構成で無負荷状態を検知することができる。
【００４０】
また、インバータ回路の出力スイッチングトランジスタに流れる過大な電流を検知するためスイッチングトランジスタのソース電流を検出するための検知回路をソース回路側に設けて、過大電流が流れると直ちにスイッチングトランジスタをオフ状態にしたり、オフ状態を持続する保護動作をさせることができる。ソース回路側に設けるため、低電圧で小型の回路構成で保護動作を実現できる。
【００４１】
更に、フィラメントの断線とランプの無負荷状態などの複数の異常状態を検出することのできる信頼性の高い放電ランプ保護装置を提供できる。
【図面の簡単な説明】
【図１】本発明の実施の形態１における放電ランプ点灯装置の主要部の構成図
【図２】本発明の実施の形態１における放電ランプ点灯装置のフィラメント電圧検知回路の回路図
【図３】本発明の実施の形態２における放電ランプ点灯装置の放電ランプの開放状態を検知するための回路図
【図４】本発明の実施の形態３における放電ランプ点灯装置の過電流検知回路
【図５】実施の形態３における放電ランプ点灯装置の過電流検知回路の動作説明のためのパルス波形図
【図６】本発明の実施の形態３における放電ランプ点灯装置の別の過電流検知回路
【図７】従来の実施の形態の放電ランプ点灯装置
【符号の説明】
Ｔ１、Ｔ２ 予熱用トランス
Ｌ２、Ｌ３ コイル
Ｃ２、Ｃ３、Ｃ４ コンデンサ
Ｑ１、Ｑ２、Ｑ３ トランジスタ
１０ 力率改善制御回路
１１ インバータ制御回路
１２ フィラメント電圧検知回路
１３ 放電ランプ
１４、１５ 放電ランプのフィラメント
１００ インバータ回路
２００ 昇圧アクティブフィルタ回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp lighting device, and particularly has a feature in a protective operation of the discharge lighting device.
[0002]
[Prior art]
In recent years, a small-diameter and high-efficiency discharge lamp that has begun to spread has a longer distance between the two filaments than a conventional fluorescent lamp, and therefore, it is necessary to apply a high lamp voltage. Therefore, as a discharge lamp lighting device for lighting this type of discharge lamp, a high power factor may be required, and a commercial AC power source is boosted by an active filter type chopper circuit, and further an output of an inverter circuit is increased. This can be done by boosting the voltage using a transformer.
[0003]
FIG. 7 is a circuit diagram of a capacitor preheating method that is most commonly used in inverter lighting circuits of fluorescent lamps that have been widely used.
[0004]
This circuit comprises a coil L1 connected to a pulsating voltage, a transistor Q1 that switches through the coil, a drain of the transistor Q1, a diode D1 connected to the coil L1, and a capacitor C1 for rectifying the voltage waveform. And an active filter type boosting active filter control circuit, an inverter circuit made up of transistors Q2 and Q3, a resonance circuit made up of a coupling capacitor C3, a coil L3 and a capacitor C4. A current value necessary for heating the filament is set with the impedance of C4, and the current is limited by the impedance of the coil L3 of the resonance circuit at the time of lighting. The voltage applied to the lamp is determined by the resonance frequency of the capacitor C4 and the coil L3. In this circuit, even if the filament is disconnected, there is a path through which current flows in the capacitor C4 of the resonance circuit. Therefore, even if the filament is disconnected while the discharge lamp is lit, the discharge lamp continues to be lit, and abnormal heat is generated. May be.
[0005]
Therefore, as disclosed in JP-A-10-284275, a preheating transformer type is adopted for a discharge lighting device in a thin tube. In this method, when the filament is disconnected, there is no current flow path, so the aforementioned heat generation problem is reduced. This circuit is provided with a filament break detection circuit to stop protection. Then, a resonance circuit is connected to the inverter circuit, and further a step-up transformer is provided to generate a higher voltage than the inverter circuit of a fluorescent lamp that has been widely used, and a preheating transformer coupled to the step-up transformer is provided. Regarding the disconnection detection of the filament, a DC component is cut off by inserting a capacitor in series with one end of the preheating transformer, and a DC current is passed through a resistance to the other end of the filament to detect a voltage across the resistance. Is going on.
[0006]
[Problems to be solved by the invention]
However, in the method of obtaining a high voltage by providing a step-up transformer, a large step-up transformer is required, and a resistor for detecting a break in the filament is required in a portion where the high voltage is generated, and a component having a high withstand voltage is required. There is a problem.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, a discharge lamp lighting device according to the present invention includes an inverter circuit that converts a DC power source into high-frequency power, and a discharge lamp lighting that applies the output of the inverter circuit to the discharge lamp via a load resonance circuit. In the device
Between the inverter circuit and the load resonance circuit, a series resonance circuit having a resonance frequency different from that of the resonance circuit and a preheating transformer for passing a preheating current to the filament of the discharge lamp are connected in series, and the preheating transformer It has a filament voltage detecting means for measuring a terminal voltage to detect a filament voltage, and determining that the filament is in an abnormal state when the detected filament voltage is greater than a predetermined voltage. The boosting is performed by the active filter type boosting active filter circuit before the inverter circuit, so that the filament abnormality can be detected only by using a relatively small transformer for preheating the filament of the discharge lamp without using a large step-up transformer. It can be detected. That is, since the resistance value of the filament is different between when it is normal and when it is disconnected, the disconnection state of the filament can be detected by monitoring the voltage generated in the winding of the preheating transformer.
[0010]
Furthermore, in the discharge lamp lighting device that applies the output of the inverter circuit to the discharge lamp via the coupling capacitor and the load resonance circuit, the inverter circuit that converts the DC power into the high frequency power,
Between the inverter circuit and the load resonance circuit, a series resonance circuit having a resonance frequency different from that of the resonance circuit and a preheating transformer for passing a preheating current to the filament of the discharge lamp are connected in series, and the preheating transformer A resistance is connected in parallel with the coupling capacitor and a filament voltage detecting means for detecting an abnormal state of the filament by measuring the terminal voltage and detecting the filament voltage, and the voltage at one end of the resistor on the load resonance circuit side is set as the resistance. A lamp open detection means for dividing the voltage and determining that there is no load through which the discharge current flows when the divided voltage of the resistor is greater than a predetermined voltage, and stopping the operation of the discharge lamp lighting device;
A control transistor is connected between the gate and source of the output transistor of the inverter circuit, the voltage across the source resistance of the output transistor is measured, the current flowing through the output transistor is detected, and the excess current exceeding the predetermined current value is detected. And an output transistor overcurrent detecting means for detecting an overcurrent value exceeding a predetermined current value by lowering a gate voltage of the output transistor of the inverter circuit and controlling an inverter output when a current value is detected. Even when a certain protection circuit operates poorly, other protection circuits operate even when a certain protection circuit is malfunctioning, thereby providing a highly reliable discharge lamp lighting device as a protection circuit for the discharge lamp lighting device. Can be provided.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
(Embodiment 1)
An embodiment of the present invention will be described with reference to FIG. In addition, the part which show | plays the structure and effect similar to a prior art attaches | subjects the same code | symbol as FIG. 7, and demonstrates a structure and operation | movement.
[0013]
In FIG. 1, a boosting active filter circuit unit 200 includes a coil L1, a transistor Q1, a diode D1, and a capacitor C1, and a pulsating voltage obtained by full-wave rectification of a commercial AC power supply is input via the coil L1. The step-up active filter control circuit 10 uses an active filter circuit system to filter the input waveform into a sine wave and also performs step-up. A series circuit of a diode D1 and a smoothing capacitor C1 is connected to the drain of the transistor Q1. The transistor Q1 is switched by the boost active filter control circuit 10 at a frequency sufficiently higher than the commercial power supply frequency.
[0014]
The step-up active filter control circuit unit 200 releases energy stored in the coil L1 when the transistor Q1 is turned on, and generates a voltage obtained by adding the input voltage and the voltage across the coil L1. A voltage higher than the input voltage is stored in the capacitor C1 as a DC power supply by the rectifier circuit of the diode D1 and the capacitor C1.
[0015]
The inverter circuit unit 100 includes transistors Q2 and Q3 and an inverter control circuit 11. A series circuit of transistors Q2 and Q3 connected to both ends of the capacitor C1 is alternately turned on and off by the inverter control circuit 11. A resonance circuit (load circuit resonance circuit) composed of a coil L3 and a capacitor C4 is connected to a midpoint between the source of the transistor Q2 and the drain of Q3 via a DC blocking capacitor C3. The resonance frequency of this load circuit resonance circuit is about 70 KHz.
[0016]
The discharge lamp 13 is connected to both ends of the resonance capacitor C4, and secondary windings of the preheating transformers T1 and T2 are connected to one end of the bipolar filaments 14 and 15 of the discharge lamp 13. The primary windings of the preheating transformers T1 and T2 are connected in series from the connection point of the transistors Q2 and Q3 through the series connection of the capacitor C2 and the coil L2 forming the preheating resonance circuit, and the secondary side is the discharge lamp 13. The filaments 14 and 15 are connected. Unlike the load circuit resonance frequency, the resonance frequency of the preheating resonance circuit is about 150 KHz. The preheating transformers T1 and T2 allow a preheating current to flow at the start of discharge of the discharge lamp 13 (current value varies even at the start of discharge).
[0017]
The capacitor C2 and the coil L2 connected in series of the preheating resonance circuit are directly connected to the preheating transformers T1 and T2, and the test point TP11 which is a connection point on the resonance circuit side (coil L2 side) of the preheating transformer is a filament voltage detection circuit 12 Connect to. The resonance frequency of the capacitor C2 and the coil L2 of the preheating resonance circuit is set to a frequency (about 150 KHz) higher than the resonance frequency of the capacitor C4 and the coil L3 of the resonance circuit for the load circuit.
[0018]
At the time of preheating, the discharge lamp 13 is not lit, and a condition must be made such that a larger current flows through the filaments 14 and 15 of the discharge lamp 13 than at the time of lighting. That is, under the control of the inverter control circuit 11, the frequency of the high frequency output from the inverter circuit unit 100 during preheating is set higher than the resonance frequency for the load circuit, so that both ends of the discharge lamp 13 are necessary for lighting. Only a voltage less than the applied voltage is generated. However, since the preheating resonance circuit composed of the series connection of the coil L2 and the capacitor C2 is close to the resonance frequency, voltage levels during preheating are generated in the primary windings Np1 and Np2 of the preheating transformers T1 and T2. This voltage is generated at both ends of the filaments 14 and 15 of the discharge lamp 13 in accordance with the winding ratio of the preheating transformers T1 and T2. However, since the resistance value of the filament at this time is about several ohms, a predetermined preheating voltage is applied to both ends of the filaments 14 and 15.
[0019]
The voltage across the capacitor C1 is Vin, the resistance value of the filament is R (corresponding to the effective secondary resistance of the transformers T1 and T2), the number of primary windings Np and the number of secondary windings Ns of the preheating transformer Assuming that the winding ratio of M is M, the voltage input to the filament voltage detection circuit 12 (the voltage at the test point TP11) is expressed as in (Equation 1).
[0020]
[Expression 1]

[0021]
The abnormality of the discharge lamp 13 can be detected by detecting this voltage with the filament voltage detection circuit 12.
[0022]
On the other hand, when the discharge of the discharge lamp 13 is started, the oscillation frequency of the inverter circuit unit 100 is lowered from 150 KHz, which is the preheating frequency, and close to the resonance frequency for the load circuit, so that the applied voltage to the discharge lamp 13 is increased. Thus, the discharge lamp 13 can be turned on when the voltage required for lighting is exceeded. At this time, the voltage of the filament voltage detection circuit 12 deviates from the resonance condition at the time of preheating because the frequency of the inverter circuit unit 100 is lowered, so that the voltage applied to both ends of the filaments 14 and 15 also drops. The current is also lower than during preheating.
[0023]
In addition, by appropriately setting the oscillation frequency of the inverter circuit after starting, the applied voltage to the discharge lamp 13 can be changed using the resonance characteristics of the resonance circuit for the load circuit, and the discharge lamp 13 is rated. It can be turned on or dimmed.
[0024]
Next, the filament breakage, which is a kind of abnormality of the discharge lamp, or a state in which the filament electrode emitter material adheres to the filaments 13 and 14 and the resistance values at both ends of the filament are larger than normal. The operation of the filament detection circuit 12 to be detected will be described.
[0025]
The input voltage of the filament voltage detection circuit 12 detects the voltage at the connection point between the preheating resonance circuit and the filament preheating transformer. That is, the voltage of the test point TP11, which is a connection point between the coil L2 and the transformer T1. The voltage shown in (Equation 1) is obtained for TP11. However, if the filament is disconnected but the emitter material of the filament electrode adheres to the filament, the resistance value is larger than the resistance value at both ends of the filament when it is not disconnected. That is, R in (Equation 1) increases, and as a result, the filament detection voltage Vd becomes larger than normal, and the detection voltage Vd is measured to detect an abnormal state of the filament.
[0026]
FIG. 2 shows a specific circuit example of the filament detection circuit 12. The filament voltage detection circuit is connected to the capacitor C11 connected to the input TP11, the capacitor C12 connected in series thereto, the cathode of the diode D11 from the middle point of the capacitors C11 and C12, and the diode D11 and the common anode connection D12 are connected. A capacitor C13 is connected in parallel to the diode D12, the anode of the diode D11 is connected to the base of the transistor Q12 via the constant voltage diode D13 and the resistor R11, and the resistor R14 is connected between the base and emitter of the transistor Q12. It is inserted and output to TP13, which is the output terminal of the filament detection circuit 12, through the collector pull-up resistor R15. The anode of D13 is connected to the base of the transistor Q11 via the constant voltage diode D14 and the resistor R12, and the resistor R13 is connected to the base and emitter of the transistor Q11. The collector of the transistor Q11 is connected to the base of the transistor Q12.
[0027]
The operation of this filament voltage detection circuit will be described. The AC voltage generated in TP11 is divided by capacitors C11 and C12, and is double-voltage rectified by diodes D11, D12, and C13. When the constant voltage diodes D13 and D14 have different zener voltages, the constant voltage diode D13 is set to a predetermined constant voltage that turns on the transistor Q12 when the discharge lamp 13 is normally lit, and the constant voltage diode D14 is when the filament is disconnected. Is set to a predetermined constant voltage at which the transistor Q11 is turned on. Thus, when the filament is disconnected, a higher voltage than normal is input to TP11. Therefore, in addition to using different Zener voltages for D14 and D13, diodes having the same Zener voltage are used. It is also possible to obtain a predetermined voltage to the transistors Q12 and Q11 by changing the divided voltage of the resistors R11 and R14 and R12 and R14. As a result, when the discharge lamp is normally lit, the output TP13 of the filament detection circuit 12 becomes L output, and when the filament breakage or the like is abnormal, the transistor Q11 is turned on and the transistor Q12 is turned off, so the output of the filament voltage detection circuit 12 is H Output. Further, when there is no signal at the input terminal TP11 of the filament detection circuit 12 due to an abnormality in any circuit of the discharge lamp lighting device, the transistor Q12 is turned off, so that the protection circuit output TP13 becomes L, and the same operation as that at the time of abnormality is performed. Any abnormal state can be detected.
[0028]
Further, a plurality of circuits after the anode of the diode D11 can be provided in parallel, and the respective detection outputs can be used for stopping the inverter control circuit and stopping the boosting active filter control circuit 10. For example, when a microcomputer is used for the control circuit 11 of the inverter, when an abnormality is detected by the filament detection circuit 12, the operation of the microcomputer is stopped first. Considering the case where the microcomputer runs out of control, it is possible to perform an operation such as stopping the boosting active filter control circuit 10 by providing a delay time after the microcomputer stops operating, and to increase safety and reliability. I can do it.
[0029]
In the circuit shown in FIG. 1, when the operation of the active filter in the step-up active filter control circuit 10 is stopped, the step-up operation is stopped, so that the DC voltage of the capacitor C1 becomes the rectified voltage of the commercial AC power supply. Therefore, the voltage for continuing to turn on the discharge lamp cannot be secured, and the discharge lamp is turned off. That is, the discharge of the discharge lamp 13 can also be stopped by stopping the operation of the step-up active filter control circuit 10 with the detection output of the filament detection circuit 12.
[0030]
(Embodiment 2)
Another embodiment of the present invention will be described with reference to FIG. The difference from Embodiment 1 shown in FIG. 1 is that the voltage applied to both ends of the discharge lamp 13 is detected instead of detecting the filament voltage. In FIG. 3, in parallel with the coupling capacitor C3, the voltage at the connection point of the resistor R21, the capacitor C3 and the coil L3 of the resonance circuit is divided by the resistors R22 and R23, and the transistor is passed through the low-pass filter composed of the capacitor C25 and the resistor R24. Connected to Q24. Since the resistor R21 is connected in parallel with the capacitor C3 for cutting off the DC component, a combined voltage of a rectangular wave and a slight DC component appears at the connection point between R22 and R23. The combined voltage is converted into a DC voltage by a low-pass filter including a capacitor C25 and a resistor R25, and is applied between the base and emitter of the transistor Q24.
[0031]
When a normal discharge lamp 13 is connected, it exhibits a negative resistance characteristic that the lamp voltage of the discharge lamp decreases as the discharge current of the discharge lamp increases, so that it occurs at both ends of the capacitor C4 of the load resonance circuit. The voltage to be reduced is reduced from the lamp voltage at the start of discharge during lighting, and is maintained at a predetermined lamp voltage in a normal discharge state. During this normal discharge, the voltage between the base and emitter of the transistor Q24 is set to a voltage that does not turn on. At the start of lighting, the inverter circuit control circuit 11 decreases the output frequency of the inverter circuit unit 100 from 150 KHz, and the discharge lamp lights up as the lamp voltage increases due to the incorrect resistance characteristics of the discharge lamp. Until then, Q24 does not turn on. That is, in the normal lighting state from the start of lighting, the collector of Q24 is at the H level, the discharge lamp is in an open state, the inverter circuit unit 11 and the boosting active circuit unit 200 are in an abnormal state, and both ends of the capacitor C4. Q24 is turned on when the voltage generated at the time exceeds a predetermined voltage. Accordingly, the voltage applied to Q24 is monitored to detect an abnormality in the lamp voltage. That is, an abnormal state of the lamp voltage can be detected by comparing and monitoring the output from Q24 for a few seconds at the start of lighting and thereafter from the inverter control circuit 11.
[0032]
Further, when both of the emitters of the electrodes of the discharge lamp disappear or when the discharge lamp is removed from the fixture, the resistance across the discharge lamp 13 in the stable discharge state becomes larger than the voltage across the resonance capacitor C4. Since there is no longer a resistance to maintain this voltage, the ramp voltage rises and the transistor Q24 is turned on. By controlling the inverter output circuit 11 using the collector output signal of Q24, the voltage across the resonant capacitor C4 generated when both the emitters of the electrodes of the discharge lamp disappear or when the discharge lamp is removed from the appliance is obtained. It is possible to prevent sustaining at a high state and to suppress high voltage applied to the switching transistors Q2 and Q3, the capacitor C3, and the coil L3 of the inverter circuit 11, and to suppress stress on those electronic components.
[0033]
(Embodiment 3)
Next, Embodiment 3 will be described with reference to FIGS. In FIG. 4, a resistor R31 is formed at the source of the switching transistor Q3 of the inverter circuit unit 100, and a transistor Q31 that is turned on / off by a voltage generated between its base and emitter at its both ends and its base resistor R32. When the voltage generated at both ends of the source resistor R31 by the current flowing through the switching transistor Q3 becomes equal to or higher than the base-emitter voltage of the transistor Q31, the transistor Q31 is turned on and the gate potential of the switching transistor Q3 is set to L, so that the switching transistor Q3 is specified. An abnormal voltage higher than the voltage can be prevented from being applied, and stress on electronic components such as transistors can be reduced.
[0034]
This operation will be described using the inverter voltage output waveform of FIG. At the time of normal lighting, as shown in the pulse waveform A of FIG. 5A, a pulse output having a duty ratio of about 70 KHz and a duty ratio of about 50% is a voltage waveform of the inverter output. When the inverter output voltage increases for some reason, the current flowing through the inverter circuit 100 increases, the voltage applied to the base of Q31 exceeds the threshold Th, and the pulse waveform exceeds the threshold Th as shown in FIG. 5B. When the voltage is applied, the voltage applied to the gate of Q3 falls to the L level, and Q3 is turned off. The output of the inverter circuit 100 becomes a pulse waveform having a small duty ratio as shown by the solid line waveform B in FIG. 5A, and the duty ratio of the rectangular wave input to the load resonance circuit is different. The voltage generated at both ends of the capacitor C4 is suppressed because the resonance condition of the resonance circuit is not satisfied. Therefore, since an excessive voltage is not applied to the coil L3, the capacitor C4, etc. of the resonance circuit, the stress on the electronic component is reduced, and a small component with a small withstand voltage can be used.
[0035]
(Embodiment 4)
The fourth embodiment will be described with reference to FIG. In FIG. 6, the collector of the transistor Q31 is connected to the base of the transistor Q41 via the resistor R45, and the resistor R41 is connected between the base and emitter of the transistor Q41. Further, the base of the transistor Q42 is connected to the collector of the transistor Q41 by dividing by resistors R43 and R44. A latch circuit is configured by connecting the base of the transistor Q41 to the collector of the transistor Q42 via a resistor R42. A DC power source is connected to TP41 as a power source for the latch circuit. The cathode of the diode 41 is connected to the collector of the transistor Q42, and the anode is connected to the gate of the switching transistor Q3.
In the operation of this circuit, when the overcurrent detection transistor Q31 is turned on once, a voltage is generated across the base-emitter resistor R41 of the transistor Q41, and the transistor Q41 is turned on. As a result, current begins to flow through the resistor R43, a voltage is generated across the R44, and the transistor Q42 is turned on. When the transistor Q42 is turned on, a base current for maintaining the on-condition of the transistor Q41 flows in R42, so that the transistor Q41 is kept on as long as the TP41 has a DC power supply. As a result, the gate voltage of the switching transistor Q3 continues to be maintained at L via the diode D41 for preventing backflow from the TP41. That is, once an abnormal voltage is detected, Q3 is turned off and the inverter output is stopped.
[0036]
As a result, the operation of the inverter circuit unit 100 is stopped, the stress on the switching transistor Q3 is reduced, and the inverter circuit 11 is stopped when an overcurrent flows, so that the stress on the coil L3 and the capacitor C4 of the resonance circuit is also reduced. Since it is reduced, small parts can be used.
[0037]
【The invention's effect】
As described above, according to the discharge lamp lighting device of the present invention, the input DC voltage is generated by the active filter type boosting active filter circuit, so that the filament can be used without using a large step-up transformer. Since a preheating current can be supplied to the filament and an abnormality can be detected using a relatively small preheating transformer, the apparatus can be downsized.
[0038]
Further, by providing multiple protection circuits, it is possible to provide a multi-stage abnormality protection operation such as the operation stop of the inverter circuit and the operation stop of the boosting active filter circuit, thereby providing a highly reliable protection circuit.
[0039]
In addition, when a normal discharge lamp is connected, the DC voltage generated at the midpoint of the coupling capacitor and the coil of the resonance circuit is regulated to a predetermined voltage value by the resistance value of the discharge lamp. It becomes high when the lamp is opened, and a no-load state can be detected with a simple circuit configuration.
[0040]
In addition, a detection circuit for detecting the source current of the switching transistor is provided on the source circuit side in order to detect an excessive current flowing through the output switching transistor of the inverter circuit, and when the excessive current flows, the switching transistor is immediately turned off. Thus, a protection operation that maintains the off state can be performed. Since it is provided on the source circuit side, the protection operation can be realized with a low voltage and a small circuit configuration.
[0041]
Furthermore, it is possible to provide a highly reliable discharge lamp protection device capable of detecting a plurality of abnormal states such as filament breakage and no-load state of the lamp.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a main part of a discharge lamp lighting device according to Embodiment 1 of the present invention. FIG. 2 is a circuit diagram of a filament voltage detection circuit of the discharge lamp lighting device according to Embodiment 1 of the present invention. FIG. 4 is a circuit diagram for detecting the open state of the discharge lamp of the discharge lamp lighting device according to Embodiment 2 of the present invention. FIG. 4 is an overcurrent detection circuit of the discharge lamp lighting device according to Embodiment 3 of the present invention. FIG. 6 is a pulse waveform diagram for explaining the operation of the overcurrent detection circuit of the discharge lamp lighting device according to the third embodiment. FIG. 6 is another overcurrent detection circuit of the discharge lamp lighting device according to the third embodiment of the present invention. Discharge lamp lighting device according to a conventional embodiment [Explanation of symbols]
T1, T2 Preheating transformer L2, L3 Coils C2, C3, C4 Capacitors Q1, Q2, Q3 Transistor 10 Power factor improvement control circuit 11 Inverter control circuit 12 Filament voltage detection circuit 13 Discharge lamp 14, 15 Discharge lamp filament 100 Inverter circuit 200 Boost Active Filter Circuit

Claims (4)

In an inverter circuit that converts a DC power source into high-frequency power, and a discharge lamp lighting device that applies the output of the inverter circuit to a discharge lamp via a resonant circuit for a load,
Between the inverter circuit and the load resonance circuit, a series resonance circuit having a resonance frequency different from that of the resonance circuit and a preheating transformer for passing a preheating current to the filament of the discharge lamp are connected in series, and the preheating transformer Discharge lamp lighting characterized by having a filament voltage detection means for measuring a terminal voltage to detect a filament voltage and determining that the filament is in an abnormal state when the detected filament voltage is greater than a predetermined voltage apparatus.   2. The discharge lamp according to claim 1, wherein when the filament voltage detected by the filament voltage detecting means is equal to or higher than a predetermined voltage, it is determined that the filament of the discharge lamp is abnormal and the discharge lamp lighting device is stopped. Lighting device. A boost active filter circuit that boosts a high-frequency pulsating voltage obtained by switching an input pulsating voltage; an inverter circuit that converts a DC voltage obtained by rectifying the output of the boost active filter circuit into high-frequency power; In the discharge lamp lighting device that applies the output of the inverter circuit to the discharge lamp via the load resonance circuit,
Between the inverter circuit and the load resonance circuit, a series resonance circuit having a resonance frequency different from that of the resonance circuit and a preheating transformer for passing a preheating current to the filament of the discharge lamp are connected in series, and the preheating transformer Filament voltage detection means for measuring the terminal voltage and outputting at least two or more control signals to control the boost active filter circuit and the inverter control circuit when the measured filament voltage is greater than a predetermined voltage. A discharge lamp lighting device comprising: In an inverter circuit that converts a DC power source into high-frequency power, and a discharge lamp lighting device that applies an output of the inverter circuit to a discharge lamp via a coupling capacitor and a load resonance circuit,
Between the inverter circuit and the load resonance circuit, a series resonance circuit having a resonance frequency different from that of the resonance circuit and a preheating transformer for passing a preheating current to the filament of the discharge lamp are connected in series, and the preheating transformer A filament voltage detecting means for measuring a terminal voltage and detecting a filament voltage to detect an abnormal state of the filament;
A resistor is connected in parallel with the coupling capacitor, the voltage at one end of the resistor on the load resonance circuit side is divided by resistance, and a discharge current flows when the divided voltage is higher than a predetermined voltage. A lamp open detection means for determining that there is no load and stopping the operation of the discharge lamp lighting device;
A control transistor is connected between the gate and source of the output transistor of the inverter circuit, the voltage across the source resistance of the output transistor is measured, the current flowing through the output transistor is detected, and the excess current exceeding the predetermined current value is detected. Discharging comprising: an output transistor overcurrent detecting means for detecting an overcurrent value exceeding a predetermined current value by lowering a gate voltage of the output transistor of the inverter circuit and controlling an inverter output when a current value is detected. Lamp lighting device.

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