JP2008262871A - Discharge lamp lighting device, lighting system using it, and liquid crystal display device - Google Patents

Discharge lamp lighting device, lighting system using it, and liquid crystal display device Download PDF

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JP2008262871A
JP2008262871A JP2007106262A JP2007106262A JP2008262871A JP 2008262871 A JP2008262871 A JP 2008262871A JP 2007106262 A JP2007106262 A JP 2007106262A JP 2007106262 A JP2007106262 A JP 2007106262A JP 2008262871 A JP2008262871 A JP 2008262871A
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transformer
discharge lamp
capacitor
lighting device
lamp lighting
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Masahiro Naruo
誠浩 鳴尾
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Panasonic Electric Works Co Ltd
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Matsushita Electric Works Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive discharge lamp lighting device having achieved long service life even if an input voltage is low. <P>SOLUTION: This discharge lamp lighting device is provided with: a first transformer T1 having, on a primary winding, a center tap for inputting a voltage from a D.C. power source DC thereto; a pair of switching elements Q1 and Q2 respectively connected between the reference potential of the D.C. power source DC and both ends of the primary winding of the first transformer T1; and a control circuit 11 controlling the switching elements Q1 and Q2; and is structured such that the first transformer T1 is a leakage transformer, a first capacitor C1 is connected in parallel to a secondary winding of the first transformer T1, and a hot-cathode discharge lamp 1 is connected to the first capacitor C1 through a second capacitor C2. The inputs of preheating circuits of filaments of the hot-cathode discharge lamp 1 are connected between respective connection points between both the ends of the primary winding of the first transformer T1 and the pair of switching elements Q1 and Q2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、直流電源を高周波に変換して放電灯を点灯させる放電灯点灯装置及びこれを用いた照明装置、液晶表示装置に関する。   The present invention relates to a discharge lamp lighting device that turns on a discharge lamp by converting a direct current power source into a high frequency, an illumination device using the same, and a liquid crystal display device.

パーソナルコンピュータやＯＡ機器、液晶テレビなどの液晶表示装置や看板灯などの照明装置において、表示面を背面から照明する光源（所謂バックライト）が用いられることが多く、その中でも広い発光面を高輝度に照明するために、反射板上に複数本の放電灯を配置し、放電灯上方に拡散板等を配置して構成される直下型バックライトが知られている。   Light sources (so-called backlights) that illuminate the display surface from the back are often used in liquid crystal display devices such as personal computers, OA equipment, and liquid crystal televisions, and signage lamps. Among them, a wide light-emitting surface has high brightness. In order to illuminate the backlight, there is known a direct type backlight in which a plurality of discharge lamps are arranged on a reflection plate and a diffusion plate or the like is arranged above the discharge lamp.

図５に直下型バックライトを備えた液晶表示装置の分解斜視図を示す。液晶パネルＬＣＰの背面（直下）にバックライトＢＬが配置されておリ、バックライトＢＬは、筐体２１と、この上に設置された反射板２２及び複数の放電灯１〜８と、その上方に設置された拡散板２３、プリズムシート等の光学シート２４とから構成されている。また、筐体２１の背面に放電灯１〜８を点灯する放電灯点灯装置１０が設置されている。   FIG. 5 is an exploded perspective view of a liquid crystal display device having a direct type backlight. A backlight BL is disposed on the back surface (directly below) of the liquid crystal panel LCP. The backlight BL includes a casing 21, a reflector 22 and a plurality of discharge lamps 1 to 8 installed thereon, and an upper portion thereof. And an optical sheet 24 such as a prism sheet. In addition, a discharge lamp lighting device 10 for lighting the discharge lamps 1 to 8 is installed on the back surface of the casing 21.

この放電灯点灯装置１０は、入力電圧として１２Ｖや２４Ｖといった低い直流電圧源を用いられることが多く、冷陰極蛍光ランプ（ＣＣＦＬ）を点灯させる場合は非常に高い昇圧比のトランスが必要となる。そのため、放電灯点灯装置のインバータ回路構成として入力電圧が低い場合に有利なプッシュプル方式の回路が使用されている。   The discharge lamp lighting device 10 often uses a low DC voltage source such as 12V or 24V as an input voltage, and a transformer with a very high step-up ratio is required to light a cold cathode fluorescent lamp (CCFL). Therefore, a push-pull circuit that is advantageous when the input voltage is low is used as the inverter circuit configuration of the discharge lamp lighting device.

近年、特に液晶表示装置の分野では画面の大型化、高輝度化、均一化の要求により、装置１セット当たりに採用する灯数は増加し、使用される放電灯の管電圧はより高電圧になる傾向にある。ＣＣＦＬは３２インチサイズのバックライトに用いられるものでも管電圧がおよそ１ｋＶｒｍｓである。このため、高インピーダンス負荷と筐体間との寄生容量の影響が無視できず、筐体への漏れ電流の影響でランプの輝度分布に偏りが生じ、輝度が不均一となる問題がある。   In recent years, particularly in the field of liquid crystal display devices, the number of lamps used per set has increased due to demands for larger screens, higher brightness, and uniformity, and the tube voltage of discharge lamps used has become higher. Tend to be. CCFL has a tube voltage of about 1 kVrms even when used for a 32-inch size backlight. For this reason, the influence of the parasitic capacitance between the high impedance load and the housing cannot be ignored, and there is a problem that the luminance distribution of the lamp is biased due to the influence of the leakage current to the housing, resulting in uneven brightness.

そこで、ＣＣＦＬよりも高出力で、管電圧が低い熱陰極蛍光ランプ（ＨＣＦＬ）を利用することが考えられる。ＨＣＦＬを用いれば、ＣＣＦＬに比べランプ本数を激減させることができ、点灯回路を減らせる利点がある。また、管電圧が低いので、筐体間との寄生容量の影響が小さく、輝度の偏りも小さくなる。さらに低ノイズであるため、液晶パネル等周辺回路への影響も小さくなる。   Therefore, it is conceivable to use a hot cathode fluorescent lamp (HCFL) having a higher output than the CCFL and a low tube voltage. The use of HCFL has the advantage that the number of lamps can be drastically reduced compared with CCFL, and the number of lighting circuits can be reduced. Further, since the tube voltage is low, the influence of the parasitic capacitance between the cases is small, and the luminance deviation is also small. Furthermore, since the noise is low, the influence on peripheral circuits such as a liquid crystal panel is reduced.

ＨＣＦＬでも同様に、入力電圧が低い場合は、トランス、スイッチング素子の利用効率を考えるとプッシュプル方式が有利と考えられる。ＨＦＣＬでプッシュプル方式の放電灯点灯装置に関して記載された文献として、以下のようなものがある。   Similarly, in the case of HCFL, when the input voltage is low, the push-pull method is considered advantageous in view of the utilization efficiency of the transformer and the switching element. Documents described regarding the HFCL push-pull discharge lamp lighting device include the following.

特許文献１の技術では、図６に示すように、熱陰極放電ランプ１にランプ電流を供給するプッシュプルインバータのリーケージトランスＴ１に補助巻線を設けてフィラメントに電流を供給しているので、回路構成は簡単であるが、ランプ電流とフィラメント電流の制御を個別に行なうことが難しい。特許文献２の技術では、図７に示すように、ランプ電流供給用のインバータ１２とフィラメント電流供給用のインバータ１３を別に設けているので、ランプ電流とフィラメント電流の制御を個別に行なうことができるが、構成が複雑となる。
特開平５−２１１８４号公報 特開平９−３０６６８３号公報 In the technique of Patent Document 1, as shown in FIG. 6, since an auxiliary winding is provided in the leakage transformer T1 of a push-pull inverter that supplies a lamp current to the hot cathode discharge lamp 1, a current is supplied to the filament. Although the configuration is simple, it is difficult to individually control the lamp current and the filament current. In the technique of Patent Document 2, as shown in FIG. 7, since the lamp current supply inverter 12 and the filament current supply inverter 13 are provided separately, the lamp current and the filament current can be controlled separately. However, the configuration is complicated.
JP-A-5-21184 JP-A-9-306683

液晶テレビなどに用いられるバックライトは長寿命の要求が強く、ＨＣＦＬでもＣＣＦＬ同等の寿命が要求される。また、薄型化に対応するため細管形状となる傾向にある。また、幅広いコントラスト比を得るために、調光範囲を広くする必要があり、特に低光束調光が望まれる。故に、ＨＣＦＬにおいて、細い管径で幅広い調光範囲で動作しつつ長寿命を達成するためには、各調光レベルにおいて適切にフィラメント電流を設定する必要があり、フィラメントの予熱電流設計の自由度が高いことが望まれる。   Backlights used for liquid crystal televisions and the like have a strong demand for long life, and HCFLs are also required to have a life equivalent to CCFL. Moreover, it tends to be a thin tube shape in order to cope with the thinning. Further, in order to obtain a wide contrast ratio, it is necessary to widen the dimming range, and low beam dimming is particularly desired. Therefore, in HCFL, in order to achieve a long life while operating with a narrow tube diameter and a wide dimming range, it is necessary to set the filament current appropriately at each dimming level, and the degree of freedom in designing the preheating current of the filament Is desired to be high.

図６に示す特許文献１の回路では、ランプ点灯のための共振特性がフィラメント予熱電流にも影響するため、設計の自由度が低い。特に、ランプを点灯させる前の先行予熱時に十分な予熱電流を得ようとすると、ランプ両端に印加される電圧を上げなければならず、それによって予熱が不十分な状態でランプが点灯してしまうと、早期にフィラメントの断線に至ってしまう恐れがある。そのため、ランプ点灯のための共振特性と独立しての設計が望ましい。その点、図７に示す特許文献２の回路は、予熱回路と点灯回路が完全に独立して個別に設定が可能であるが、ランプ電流とフィラメント電流で同期が完全に取れないため位相関係が確定せず、ランプ電圧とフィラメント電圧の合成電圧が変動して、場合によっては輝度のちらつきを引き起こす。また、フィラメントのスポット形成が安定しないため、エミッタの消耗がまちまちとなり、寿命予測が困難となる。さらに、予熱回路と点灯回路が完全に独立しているので、部品数が多く高価であるといった問題があった。   In the circuit of Patent Document 1 shown in FIG. 6, the resonance characteristics for lamp lighting also affect the filament preheating current, and therefore the degree of design freedom is low. In particular, if a sufficient preheating current is to be obtained at the time of prior preheating before the lamp is lit, the voltage applied to both ends of the lamp must be increased, thereby causing the lamp to be lit with insufficient preheating. Then, there is a risk that the filament may be disconnected early. Therefore, a design independent of the resonance characteristics for lamp lighting is desirable. In that respect, the circuit of Patent Document 2 shown in FIG. 7 is capable of setting the preheating circuit and the lighting circuit completely independently and individually, but the phase relationship is not possible because the lamp current and the filament current cannot be completely synchronized. Without being determined, the combined voltage of the lamp voltage and the filament voltage fluctuates, possibly causing a flicker in brightness. In addition, since the filament spot formation is not stable, the emitters are consumed in various ways, making it difficult to predict the lifetime. Further, since the preheating circuit and the lighting circuit are completely independent, there is a problem that the number of parts is large and the cost is high.

本発明は、上述のような点に鑑みてなされたものであり、入力電圧が低くとも、安価で長寿命を達成した放電灯点灯装置及びそれを用いた液晶表示装置や照明装置を提供することを課題とする。   The present invention has been made in view of the above-described points, and provides a discharge lamp lighting device that achieves a long life even at a low input voltage, and a liquid crystal display device and a lighting device using the discharge lamp lighting device. Is an issue.

請求項１の発明によれば、上記の課題を解決するために、図１に示すように、直流電源ＤＣからの電圧が入力される中間タップを１次巻線に備える第１のトランスＴ１と、直流電源ＤＣの基準電位と前記第１のトランスＴ１の１次巻線の両端間にそれぞれ接続される一対のスイッチング素子Ｑ１，Ｑ２と、前記スイッチング素子Ｑ１，Ｑ２を制御する制御回路１１と、を備え、前記第１のトランスＴ１はリーケージトランスであり、前記第１のトランスＴ１の２次巻線に第１のコンデンサＣ１を並列接続し、前記第１のコンデンサＣ１に第２のコンデンサＣ２を介して熱陰極放電ランプ１を接続した放電灯点灯装置において、前記熱陰極放電ランプ１のフィラメントの予熱回路の入力を、前記第１のトランスＴ１の１次巻線の両端と前記一対のスイッチング素子Ｑ１，Ｑ２との各々の接続点間に接続したことを特徴とするものである。   According to the first aspect of the present invention, in order to solve the above-mentioned problem, as shown in FIG. 1, the first transformer T1 having an intermediate tap to which the voltage from the DC power source DC is input is provided in the primary winding. A pair of switching elements Q1, Q2 connected between the reference potential of the DC power source DC and both ends of the primary winding of the first transformer T1, and a control circuit 11 for controlling the switching elements Q1, Q2, The first transformer T1 is a leakage transformer, and a first capacitor C1 is connected in parallel to a secondary winding of the first transformer T1, and a second capacitor C2 is connected to the first capacitor C1. In the discharge lamp lighting device to which the hot cathode discharge lamp 1 is connected, the input of the filament preheating circuit of the hot cathode discharge lamp 1 is connected to both ends of the primary winding of the first transformer T1 and the pair. It is characterized in that connected between each connection point of the switching elements Q1, Q2.

請求項２の発明によれば、同じ課題を解決するために、図４に示すように、直流電源ＤＣからの電圧が入力される中間タップを１次巻線に備える第１のトランスＴ１１；Ｔ２１と、直流電源ＤＣの基準電位と前記第１のトランスＴ１１；Ｔ２１の１次巻線の両端間にそれぞれ接続される一対のスイッチング素子Ｑ１１，Ｑ２１；Ｑ１２，Ｑ２２と、を備え、前記第１のトランスＴ１１；Ｔ２１はリーケージトランスであり、前記第１のトランスＴ１１；Ｔ２１の２次巻線に第１のコンデンサＣ１１；Ｃ１２を並列接続し、前記第１のコンデンサＣ１１；Ｃ１２に第２のコンデンサＣ２１；Ｃ２２を介して熱陰極放電ランプ１；２を接続して成るインバータ回路を少なくとも２組備え、前記スイッチング素子Ｑ１１，Ｑ２１；Ｑ１２，Ｑ２２を制御する制御回路１１を備えた放電灯点灯装置において、前記インバータ回路の少なくとも１組は、前記熱陰極放電ランプ１；２のフィラメントの予熱回路の入力を、前記第１のトランスＴ１１の１次巻線の両端と前記一対のスイッチング素子Ｑ１１，Ｑ２１との各々の接続点間に接続されており、前記予熱回路の入力が接続されたインバータ回路以外の少なくとも１組は、直流電源ＤＣを含んで構成される電流ループにインピーダンス素子（抵抗Ｒ１）を挿入し、前記インピーダンス素子（抵抗Ｒ１）の両端電圧を前記制御回路１１に入力してフィードバック制御を行なうことを特徴とする。   According to the invention of claim 2, in order to solve the same problem, as shown in FIG. 4, the first transformer T11; T21 having an intermediate tap to which the voltage from the DC power source DC is inputted in the primary winding as shown in FIG. And a pair of switching elements Q11, Q21; Q12, Q22 respectively connected between the reference potential of the DC power source DC and both ends of the primary winding of the first transformer T11; T21. The transformer T11; T21 is a leakage transformer, and a first capacitor C11; C12 is connected in parallel to the secondary winding of the first transformer T11; T21, and a second capacitor C21 is connected to the first capacitor C11; C12. At least two sets of inverter circuits formed by connecting the hot cathode discharge lamp 1; 2 through C22, and the switching elements Q11, Q21; In the discharge lamp lighting device including the control circuit 11 to be controlled, at least one set of the inverter circuits is connected to the input of the preheating circuit of the filament of the hot cathode discharge lamp 1; 2, and the primary winding of the first transformer T11. At least one set other than the inverter circuit connected to both ends of the line and each of the connection points of the pair of switching elements Q11 and Q21 includes a DC power source DC. An impedance element (resistor R1) is inserted into the current loop, and a voltage across the impedance element (resistor R1) is input to the control circuit 11 to perform feedback control.

請求項３の発明によれば、図２に示すように、前記フィラメントの予熱回路の周波数特性において、フィラメント電流Ｉｆが極大値となる周波数を、前記第１のトランスＴ１の２次巻線のリーケージトランスと前記第１のコンデンサＣ１で決まる共振周波数よりも高く設定したことを特徴とする。   According to the invention of claim 3, as shown in FIG. 2, in the frequency characteristic of the preheating circuit of the filament, the frequency at which the filament current If becomes the maximum value is set to the leakage of the secondary winding of the first transformer T1. It is characterized in that it is set higher than the resonance frequency determined by the transformer and the first capacitor C1.

請求項４の発明によれば、図１に示すように、前記フィラメントの予熱回路は第２のトランスＴ２を備え、前記第１のトランスＴ１の１次巻線の両端と前記一対のスイッチング素子Ｑ１，Ｑ２との各々の接続点間に、第３のコンデンサＣ３と前記第２のトランスＴ２の１次巻線の直列回路を接続したことを特徴とする。   According to the invention of claim 4, as shown in FIG. 1, the preheating circuit of the filament includes the second transformer T2, both ends of the primary winding of the first transformer T1, and the pair of switching elements Q1. , Q2 is connected to a series circuit of a third capacitor C3 and a primary winding of the second transformer T2.

請求項５の発明は、請求項１〜４のいずれかに記載の放電灯点灯装置を含んでなる照明装置である。   Invention of Claim 5 is an illuminating device containing the discharge lamp lighting device in any one of Claims 1-4.

請求項６の発明は、請求項１〜４のいずれかに記載の放電灯点灯装置を含んでなる液晶表示装置である。   A sixth aspect of the present invention is a liquid crystal display device comprising the discharge lamp lighting device according to any one of the first to fourth aspects.

請求項１、３、４の発明によれば、低い入力電圧で動作するのに有利なプッシュプル方式のインバータ回路において、調光の広い範囲でフィラメント温度の適正化が可能なので長寿命とすることができ、点灯装置の小型化、軽量化、コスト低減に寄与する効果がある。   According to the first, third, and fourth aspects of the invention, in the push-pull type inverter circuit that is advantageous to operate at a low input voltage, the filament temperature can be optimized in a wide range of dimming, so that the lifetime is long. Thus, the lighting device can be reduced in size, weight, and cost.

請求項２の発明によれば、上記効果に加えて、より低光束調光の範囲においても精度良くランプ出力（光出力）の安定化が図れる効果がある。   According to the second aspect of the invention, in addition to the above effect, there is an effect that the lamp output (light output) can be stabilized with high accuracy even in the range of the lower light beam dimming.

請求項５、６の発明によれば、上記効果を持つ照明装置、液晶表示装置を提供することが可能となる。   According to the fifth and sixth aspects of the invention, it is possible to provide an illumination device and a liquid crystal display device having the above effects.

（実施形態１）
図１に本発明の実施形態１の放電灯点灯装置の回路図を示す。直流電源ＤＣは所定の直流電圧を出力する電源であり、例えば商用交流電源を全波整流し、周知の昇圧チョッパ回路により平滑化して出力する回路などで構成できる。直流電源ＤＣの負極は基準電位（グランド）に接続されている。直流電源ＤＣの正極はトランスＴ１の１次巻線の中間タップに接続されており、各１次巻線の他端と基準電位（グランド）間にそれぞれスイッチング素子Ｑ１，Ｑ２が接続されて、プッシュプル回路を構成している。スイッチング素子Ｑ１，Ｑ２は例えばパワーＭＯＳＦＥＴよりなり、制御回路１１の出力により高周波で交互にオン・オフ駆動される。 (Embodiment 1)
FIG. 1 shows a circuit diagram of a discharge lamp lighting device according to Embodiment 1 of the present invention. The direct current power source DC is a power source that outputs a predetermined direct current voltage. For example, the direct current power source DC can be constituted by a circuit that rectifies a commercial alternating current power source in a full wave, smoothes it with a known boost chopper circuit, and outputs it. The negative electrode of the DC power source DC is connected to a reference potential (ground). The positive electrode of the DC power source DC is connected to the intermediate tap of the primary winding of the transformer T1, and switching elements Q1, Q2 are connected between the other end of each primary winding and the reference potential (ground), respectively, and pushed. A pull circuit is configured. The switching elements Q1, Q2 are made of, for example, a power MOSFET, and are alternately turned on / off at a high frequency by the output of the control circuit 11.

また、トランスＴ１の２次巻線にコンデンサＣ１が並列接続され、コンデンサＣ１の両端にはコンデンサＣ２を介して熱陰極蛍光ランプ１が接続されている。トランスＴ１はリーケージトランスである。トランスＴ１のリーケージインダクタンスとコンデンサＣ１、Ｃ２、及び熱陰極蛍光ランプ１が点灯時にはそのときのランプインピーダンスによって共振回路を構成している。スイッチング素子Ｑ１，Ｑ２のスイッチング周波数は前記共振回路の負荷時共振周波数よりも高く設定されている。したがって、スイッチング周波数が高くなるにつれて、ランプ電流は減少するように制御される。   A capacitor C1 is connected in parallel to the secondary winding of the transformer T1, and the hot cathode fluorescent lamp 1 is connected to both ends of the capacitor C1 via the capacitor C2. The transformer T1 is a leakage transformer. When the leakage inductance of the transformer T1, the capacitors C1 and C2, and the hot cathode fluorescent lamp 1 are lit, a resonance circuit is configured by the lamp impedance at that time. The switching frequency of the switching elements Q1, Q2 is set to be higher than the resonance frequency when the resonance circuit is loaded. Therefore, the lamp current is controlled to decrease as the switching frequency increases.

ここで本実施形態では、トランスＴ１の１次巻線の各他端とスイッチング素子Ｑ１，Ｑ２の接続点間に、コンデンサＣ３と予熱トランスＴ２の１次巻線Ｎ１の直列回路を接続している。予熱トランスＴ２は一対の２次巻線Ｎ２，Ｎ３を備え、それぞれ予熱用コンデンサＣ４，Ｃ５を介して熱陰極蛍光ランプ１の各フィラメントに接続されている。   Here, in the present embodiment, a series circuit of the capacitor C3 and the primary winding N1 of the preheating transformer T2 is connected between each other end of the primary winding of the transformer T1 and the connection point of the switching elements Q1 and Q2. . The preheating transformer T2 includes a pair of secondary windings N2 and N3, and is connected to each filament of the hot cathode fluorescent lamp 1 via preheating capacitors C4 and C5, respectively.

直流電源ＤＣの電圧をＶDCとすると、各スイッチング素子Ｑ１，Ｑ２のオン・オフ動作によってトランスＴ１の１次側に印加される電圧は略ＶDC×２をピークとする矩形波となる（リンギング成分等は除く）。よって、コンデンサＣ３と予熱トランスＴ２の１次巻線Ｎ１の直列回路には、略±ＶDC×２の矩形波電圧、すなわち直流電源電圧に略比例した矩形波電圧が印加される。そのため、フィラメント電流は、トランスＴ１のリーケージインダクタンス、コンデンサＣ１、Ｃ２、ランプインピーダンスからなるランプ点灯のための共振特性と独立した特性とすることができる。また、コンデンサＣ３と予熱トランスＴ２の１次側インダクタンスによってフィラメント予熱用の共振特性を構成することが可能となる。 When the voltage of the DC power supply DC is V DC , the voltage applied to the primary side of the transformer T1 by the on / off operation of the switching elements Q1 and Q2 is a rectangular wave having a peak of approximately V DC × 2 (ringing). Excluding ingredients). Therefore, a rectangular wave voltage of approximately ± V DC × 2, that is, a rectangular wave voltage substantially proportional to the DC power supply voltage is applied to the series circuit of the capacitor C3 and the primary winding N1 of the preheating transformer T2. Therefore, the filament current can be made independent of the resonance characteristic for lighting the lamp, which includes the leakage inductance of the transformer T1, the capacitors C1 and C2, and the lamp impedance. Further, the resonance characteristics for filament preheating can be configured by the primary inductance of the capacitor C3 and the preheating transformer T2.

図２に実施形態１の周波数特性の一例を示す。実線：Ｉｌａ１は全点灯時のランプインピーダンスを負荷とした共振回路の周波数特性であり、周波数ｆ１で点灯される。破線：Ｉｌａ２は調光点灯時のランプインピーダンスを負荷とした共振回路の周波数特性であり、周波数ｆ２で点灯される。一点鎖線：Ｉｆはフィラメント電流の周波数特性を示している。図中、Ｆｕｌｌは全点灯時、Ｄｉｍは調光点灯時を意味する。図２のように、調光レベルを下げるに従いフィラメント電流Ｉｆを増加させるような特性とすることで、調光の広い範囲においてフィラメント温度を適切に設定し、長寿命を確保することができる。また、先行予熱時には、スイッチング素子Ｑ１，Ｑ２の動作周波数をｆｐとすることで、ランプに印加される電圧を低くしつつ十分な予熱電流を確保することができるので、点滅寿命に対しても有効である。   FIG. 2 shows an example of the frequency characteristic of the first embodiment. Solid line: Ila1 is the frequency characteristic of the resonance circuit with the lamp impedance when fully lit as a load, and is lit at the frequency f1. Dashed line: Ila2 is the frequency characteristic of the resonance circuit with the lamp impedance at the time of dimming lighting as a load, and is lit at the frequency f2. Dotted line: If indicates the frequency characteristic of the filament current. In the figure, Full means full lighting and Dim means dimming lighting. As shown in FIG. 2, by setting the filament current If to increase as the dimming level is lowered, the filament temperature can be appropriately set in a wide range of dimming and a long life can be ensured. Also, at the time of pre-heating, by setting the operating frequency of the switching elements Q1 and Q2 to fp, a sufficient pre-heating current can be secured while lowering the voltage applied to the lamp, which is also effective for the flashing life. It is.

トランスＴ１をリーケージトランスではなく、密結合トランスとインダクタンスを用いれば、トランス２次巻線にコンデンサＣ３と予熱トランスＴ２の１次巻線Ｎ１の直列回路を接続することで同様の効果を奏するが、この場合、限流要素としての巻線部品が増加するため、この点では本実施形態に比べ不利となる。本実施形態のように、リーケージトランスの１次側に予熱回路の入力を接続することにより、安価な構成でランプ電流とフィラメント電流を独立して設定できるのである。   If the transformer T1 is not a leakage transformer, but a tightly coupled transformer and an inductance are used, the same effect can be achieved by connecting a series circuit of the capacitor C3 and the primary winding N1 of the preheating transformer T2 to the transformer secondary winding. In this case, since the number of winding components as current limiting elements increases, this is disadvantageous compared to the present embodiment. By connecting the input of the preheating circuit to the primary side of the leakage transformer as in this embodiment, the lamp current and the filament current can be set independently with an inexpensive configuration.

このように本実施形態では、低い入力電圧で動作するのに有利なプッシュプル方式のインバータ回路において、ランプ点灯のための共振特性とフィラメント電流特性を独立して設定することが可能なので、フィラメントの予熱電流設計の自由度が高いという利点がある。また、熱陰極蛍光ランプにランプ電流を供給するためのインバータ回路とスイッチング素子を兼用してフィラメントの予熱電流を供給しているので、フィラメント予熱用のインバータを別設する必要がなく、上記リーケージトランスを使用することも合わせて、点灯装置の小型化、軽量化、コスト低減に寄与できる。さらに、ランプ電流とフィラメント電流の位相関係が安定することによりフィラメント上のスポット（輝点）の形成が安定する利点もある。   As described above, in this embodiment, in the push-pull type inverter circuit that is advantageous to operate with a low input voltage, the resonance characteristic and the filament current characteristic for lighting the lamp can be set independently. There is an advantage that the degree of freedom in designing the preheating current is high. Further, since the preheating current of the filament is supplied by using both the inverter circuit and the switching element for supplying the lamp current to the hot cathode fluorescent lamp, there is no need to separately provide an inverter for preheating the filament, and the above leakage transformer. In combination with the use of the lamp, it is possible to contribute to reducing the size, weight and cost of the lighting device. Furthermore, there is also an advantage that the formation of spots (bright spots) on the filament is stabilized by stabilizing the phase relationship between the lamp current and the filament current.

図３に実施形態１の出力フィードバック回路構成の一例を示す。スイッチング素子Ｑ１，Ｑ２のソース端子を共通接続し、その接続点と基準電位（グランド）の間に抵抗Ｒ１のようなインピーダンス素子を接続し、このインピーダンス素子の両端電圧を制御回路１１に入力したものである。制御回路１１はその入力値に応じてスイッチング素子Ｑ１，Ｑ２の周波数もしくはオンデューティ比を変化させるものであり、スイッチング素子Ｑ１，Ｑ２の合成電流はほぼ入力電流と等しいので、入力電力を略一定化させることが可能となる。ある調光レベルの定常状態において、フィラメント損失及び回路損失に大きな変化はないので、入力電力を略一定化することで出力電力を略一定化することが可能である。   FIG. 3 shows an example of the output feedback circuit configuration of the first embodiment. The source terminals of the switching elements Q1 and Q2 are connected in common, an impedance element such as a resistor R1 is connected between the connection point and the reference potential (ground), and the voltage across the impedance element is input to the control circuit 11 It is. The control circuit 11 changes the frequency or on-duty ratio of the switching elements Q1 and Q2 in accordance with the input value. Since the combined current of the switching elements Q1 and Q2 is substantially equal to the input current, the input power is made substantially constant. It becomes possible to make it. In a steady state at a certain dimming level, there is no significant change in the filament loss and the circuit loss. Therefore, the output power can be made substantially constant by making the input power substantially constant.

（実施形態２）
図４に本発明の実施形態２の放電灯点灯装置の回路図を示す。本実施形態の放電灯点灯装置は、プッシュプル構成のインバータ回路を２組持つ２灯用回路を示したものであるが、一方の組のトランスＴ１１の１次巻線の各他端とスイッチング素子Ｑ１１，Ｑ２１の接続点間に、コンデンサＣ３と予熱トランスＴ２の１次巻線Ｎ１の直列回路を接続し、他方の組のスイッチング素子Ｑ１２，Ｑ２２のソース端子を共通接続し、その接続点と基準電位の間に抵抗Ｒ１のようなインピーダンス素子を接続し、このインピーダンス素子の両端電圧を制御回路１１に入力している。スイッチング素子Ｑ１１とＱ１２、Ｑ２１とＱ２２はそれぞれ同じ駆動信号を与えて動作させるものであり、各スイッチング素子の並列制御のためにドライバＤＶ１１，ＤＶ１２及びＤＶ２１，ＤＶ２２を備えている。 (Embodiment 2)
FIG. 4 shows a circuit diagram of a discharge lamp lighting device according to Embodiment 2 of the present invention. The discharge lamp lighting device of this embodiment shows a circuit for two lamps having two sets of push-pull configuration inverter circuits, but each other end of the primary winding of one set of transformer T11 and a switching element. A series circuit of the capacitor C3 and the primary winding N1 of the preheating transformer T2 is connected between the connection points of Q11 and Q21, and the source terminals of the other set of switching elements Q12 and Q22 are connected in common. An impedance element such as a resistor R 1 is connected between the potentials, and the voltage across the impedance element is input to the control circuit 11. The switching elements Q11 and Q12 and Q21 and Q22 are operated by applying the same drive signal, and are provided with drivers DV11 and DV12 and DV21 and DV22 for parallel control of the switching elements.

予熱トランスＴ２は２次巻線Ｎ２，Ｎ３，Ｎ４を備え、それぞれ予熱用コンデンサＣ４１，Ｃ４２，Ｃ５１，Ｃ５２を介して各熱陰極蛍光ランプのフィラメントに接続されている。ここで、低圧側のフィラメントに接続される２次巻線Ｎ３は、ランプ２本分をそれぞれ予熱用コンデンサＣ５１，Ｃ５２を介して並列に予熱する構成の例を示しているが、２次巻線Ｎ３を２つに分けてそれぞれ個別に接続する構成でもよい。   The preheating transformer T2 includes secondary windings N2, N3, and N4, and is connected to the filaments of the hot cathode fluorescent lamps via preheating capacitors C41, C42, C51, and C52, respectively. Here, the secondary winding N3 connected to the low-voltage side filament shows an example of a configuration in which two lamps are preheated in parallel via preheating capacitors C51 and C52, respectively. N3 may be divided into two and connected individually.

予熱電流の設定等は実施形態１と同様（図２参照）である。本実施形態では、予熱回路が接続されるのと別の組のインバータ回路に出力フィードバック用の信号を取り出す回路を備えたものであり、このような構成とすることで、フィラメント損失を含む予熱回路の消費電力を含まない信号をフィードバックに用いる。それによってほぼランプ電力のフィードバックが可能となるので、より低光束の調光範囲においても精度良くランプ出力（光出力）の安定化が図れる。ここでは２灯用の点灯回路を例示したが、３灯以上の点灯回路にも適用できる。   The setting of the preheating current and the like are the same as in the first embodiment (see FIG. 2). In this embodiment, a circuit for extracting a signal for output feedback is provided in a different set of inverter circuits to which the preheating circuit is connected. With such a configuration, the preheating circuit including filament loss is provided. A signal that does not include the power consumption is used for feedback. As a result, the lamp power can be almost fed back, so that the lamp output (light output) can be stabilized with high accuracy even in the dimming range of a lower luminous flux. Here, a lighting circuit for two lamps is illustrated, but the present invention can also be applied to a lighting circuit having three or more lamps.

（実施形態３）
図５に本発明の放電灯点灯装置を用いた液晶表示装置の概略構成を示す分解斜視図である。液晶パネルＬＣＰの背面（直下）にバックライトＢＬが配置されており、バックライトＢＬは、筐体２１と、この上に設置された反射板２２及び複数の放電灯１〜８と、その上方に設置された拡散板２３、プリズムシート等の光学シート２４とから構成されている。また筐体２１の背面に放電灯１〜８を点灯する放電灯点灯装置１０が設置されている。反射板２２は各放電灯１〜８の光を有効に前面に指向させるものである。拡散板２３は放電灯１〜８及び反射板２２からの光を拡散させて前面への照明光の明るさ分布を平均化する機能を有する。 (Embodiment 3)
FIG. 5 is an exploded perspective view showing a schematic configuration of a liquid crystal display device using the discharge lamp lighting device of the present invention. A backlight BL is disposed on the back surface (directly below) of the liquid crystal panel LCP. The backlight BL includes a casing 21, a reflector 22 and a plurality of discharge lamps 1 to 8 installed thereon, and an upper side thereof. It comprises an installed diffusion plate 23 and an optical sheet 24 such as a prism sheet. A discharge lamp lighting device 10 for lighting the discharge lamps 1 to 8 is installed on the back surface of the housing 21. The reflector 22 effectively directs the light from the discharge lamps 1 to 8 to the front surface. The diffusion plate 23 has a function of diffusing the light from the discharge lamps 1 to 8 and the reflection plate 22 and averaging the brightness distribution of the illumination light to the front surface.

なお、本発明の放電灯点灯装置の用途は液晶表示装置に限定されるものではなく、放電灯を用いた照明装置にも搭載できることは言うまでもない。   Needless to say, the application of the discharge lamp lighting device of the present invention is not limited to a liquid crystal display device, and can be mounted on a lighting device using a discharge lamp.

本発明の実施形態１の回路図である。It is a circuit diagram of Embodiment 1 of the present invention. 本発明の実施形態１の動作説明図である。It is operation | movement explanatory drawing of Embodiment 1 of this invention. 本発明の実施形態１の一変形例の回路図である。It is a circuit diagram of one modification of Embodiment 1 of the present invention. 本発明の実施形態２の回路図である。It is a circuit diagram of Embodiment 2 of the present invention. 本発明の放電灯点灯装置を用いた液晶表示装置の概略構成を示す分解斜視図である。It is a disassembled perspective view which shows schematic structure of the liquid crystal display device using the discharge lamp lighting device of this invention. 従来例１の回路図である。FIG. 6 is a circuit diagram of Conventional Example 1. 従来例２の回路図である。FIG. 10 is a circuit diagram of Conventional Example 2.

符号の説明Explanation of symbols

１，２ 熱陰極蛍光ランプ
Ｔ１ リーケージトランス
Ｔ２ 予熱トランス
Ｑ１，Ｑ２ スイッチング素子
Ｃ１，Ｃ２，Ｃ３ コンデンサ 1, 2 Hot cathode fluorescent lamp T1, Leakage transformer T2, Preheating transformer Q1, Q2 Switching element C1, C2, C3 Capacitor

Claims (6)

直流電源からの電圧が入力される中間タップを１次巻線に備える第１のトランスと、
直流電源の基準電位と前記第１のトランスの１次巻線の両端間にそれぞれ接続される一対のスイッチング素子と、
前記スイッチング素子を制御する制御回路と、を備え、
前記第１のトランスはリーケージトランスであり、
前記第１のトランスの２次巻線に第１のコンデンサを並列接続し、
前記第１のコンデンサに第２のコンデンサを介して熱陰極放電ランプを接続した放電灯点灯装置において、
前記熱陰極放電ランプのフィラメントの予熱回路の入力を、前記第１のトランスの１次巻線の両端と前記一対のスイッチング素子との各々の接続点間に接続したことを特徴とする放電灯点灯装置。 A first transformer having a primary winding provided with an intermediate tap to which a voltage from a DC power supply is input;
A pair of switching elements respectively connected between the reference potential of the DC power source and both ends of the primary winding of the first transformer;
A control circuit for controlling the switching element,
The first transformer is a leakage transformer;
A first capacitor connected in parallel to the secondary winding of the first transformer;
In a discharge lamp lighting device in which a hot cathode discharge lamp is connected to the first capacitor via a second capacitor,
The discharge lamp lighting characterized in that the input of the preheating circuit of the filament of the hot cathode discharge lamp is connected between the connection points of both ends of the primary winding of the first transformer and the pair of switching elements. apparatus. 直流電源からの電圧が入力される中間タップを１次巻線に備える第１のトランスと、
直流電源の基準電位と前記第１のトランスの１次巻線の両端間にそれぞれ接続される一対のスイッチング素子と、を備え、
前記第１のトランスはリーケージトランスであり、
前記第１のトランスの２次巻線に第１のコンデンサを並列接続し、
前記第１のコンデンサに第２のコンデンサを介して熱陰極放電ランプを接続して成るインバータ回路を少なくとも２組備え、
前記スイッチング素子を制御する制御回路を備えた放電灯点灯装置において、
前記インバータ回路の少なくとも１組は、前記熱陰極放電ランプのフィラメントの予熱回路の入力を、前記第１のトランスの１次巻線の両端と前記一対のスイッチング素子との各々の接続点間に接続されており、
前記予熱回路の入力が接続されたインバータ回路以外の少なくとも１組は、直流電源を含んで構成される電流ループにインピーダンス素子を挿入し、前記インピーダンス素子の両端電圧を前記制御回路に入力してフィードバック制御を行なうことを特徴とする放電灯点灯装置。 A first transformer having a primary winding provided with an intermediate tap to which a voltage from a DC power supply is input;
A pair of switching elements respectively connected between a reference potential of a DC power source and both ends of the primary winding of the first transformer,
The first transformer is a leakage transformer;
A first capacitor connected in parallel to the secondary winding of the first transformer;
At least two sets of inverter circuits formed by connecting a hot cathode discharge lamp to the first capacitor via a second capacitor;
In a discharge lamp lighting device comprising a control circuit for controlling the switching element,
At least one set of the inverter circuits connects an input of a filament preheating circuit of the hot cathode discharge lamp between connection points of both ends of the primary winding of the first transformer and the pair of switching elements. Has been
At least one set other than the inverter circuit to which the input of the preheating circuit is connected inserts an impedance element into a current loop including a DC power supply, and the voltage across the impedance element is input to the control circuit for feedback. A discharge lamp lighting device characterized by performing control. 前記フィラメントの予熱回路の周波数特性において、フィラメント電流が極大値となる周波数を、前記第１のトランスの２次巻線のリーケージトランスと前記第１のコンデンサで決まる共振周波数よりも高く設定したことを特徴とする請求項１または２記載の放電灯点灯装置。 In the frequency characteristic of the preheating circuit of the filament, the frequency at which the filament current reaches a maximum value is set higher than the resonance frequency determined by the leakage transformer of the secondary winding of the first transformer and the first capacitor. The discharge lamp lighting device according to claim 1 or 2, characterized in that 前記フィラメントの予熱回路は第２のトランスを備え、前記第１のトランスの１次巻線の両端と前記一対のスイッチング素子との各々の接続点間に、第３のコンデンサと前記第２のトランスの１次巻線の直列回路を接続したことを特徴とする請求項１〜３のいずれかに記載の放電灯点灯装置。 The filament preheating circuit includes a second transformer, and a third capacitor and the second transformer are connected between the connection points of both ends of the primary winding of the first transformer and the pair of switching elements. A discharge lamp lighting device according to any one of claims 1 to 3, wherein a series circuit of primary windings is connected. 請求項１〜４のいずれかに記載の放電灯点灯装置を含んでなる照明装置。 The illuminating device containing the discharge lamp lighting device in any one of Claims 1-4. 請求項１〜４のいずれかに記載の放電灯点灯装置を含んでなる液晶表示装置。 A liquid crystal display device comprising the discharge lamp lighting device according to claim 1.
JP2007106262A 2007-04-13 2007-04-13 Discharge lamp lighting device, lighting system using it, and liquid crystal display device Pending JP2008262871A (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01166493A (en) * 1987-12-23 1989-06-30 Matsushita Electric Works Ltd Lighting device for electric discharge lamp
JPH01298691A (en) * 1988-05-26 1989-12-01 Matsushita Electric Works Ltd Electric-discharge lamp lighting device
JPH0249097U (en) * 1988-09-30 1990-04-05
JPH0594890A (en) * 1991-10-03 1993-04-16 Nagano Japan Radio Co Lighting device
JP2000308363A (en) * 1999-04-16 2000-11-02 Toko Inc Multichannel inverter
JP2005243305A (en) * 2004-02-24 2005-09-08 Matsushita Electric Works Ltd Discharge lamp lighting device and luminaire

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01166493A (en) * 1987-12-23 1989-06-30 Matsushita Electric Works Ltd Lighting device for electric discharge lamp
JPH01298691A (en) * 1988-05-26 1989-12-01 Matsushita Electric Works Ltd Electric-discharge lamp lighting device
JPH0249097U (en) * 1988-09-30 1990-04-05
JPH0594890A (en) * 1991-10-03 1993-04-16 Nagano Japan Radio Co Lighting device
JP2000308363A (en) * 1999-04-16 2000-11-02 Toko Inc Multichannel inverter
JP2005243305A (en) * 2004-02-24 2005-09-08 Matsushita Electric Works Ltd Discharge lamp lighting device and luminaire

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