JP2009245838A - Discharge tube uniform-flow lighting and driving device - Google Patents

Discharge tube uniform-flow lighting and driving device Download PDF

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JP2009245838A
JP2009245838A JP2008092589A JP2008092589A JP2009245838A JP 2009245838 A JP2009245838 A JP 2009245838A JP 2008092589 A JP2008092589 A JP 2008092589A JP 2008092589 A JP2008092589 A JP 2008092589A JP 2009245838 A JP2009245838 A JP 2009245838A
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frequency
cold cathode
inverter circuit
discharge tube
current
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Guo-Hua Wang
国華 王
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Nitta Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge tube uniform-flow lighting and driving device capable of surely carrying out start-up of each discharge tube, and capable of flowing stable uniform electric current to each discharge tube after start-up. <P>SOLUTION: The discharge tube uniform-flow lighting and driving device for lighting and driving a plurality of discharge tubes 15 connected in parallel with each other, is provided with a support member 14 supporting the plurality of discharge tubes 15 and with floating capacitance formed between the plurality of discharge tubes, a first inverter circuit 20 supplying high-frequency drive power, and a second inverter circuit 30 supplying the high-frequency drive power. A phase of the high-frequency drive power of the second inverter circuit 30 is shifted with a predetermined angle against the high-frequency drive power of the first inverter circuit 20. Brightness of each cold cathode tube can be uniformized regardless of portions, and also uniform-flow lighting of each discharge tube can be easily performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、複数の放電管を点灯させる放電管均流点灯駆動装置に関するものである。ここで「放電管」とは、高圧を印加して、密封管内でイオン化した気体（プラズマ）に放電させることにより発光させる器具をいい、ネオン管、ナトリウムランプ、蛍光管、冷陰極管などがこれに該当する。「均流」とは複数の放電管に対して、互いにほぼ等しい大きさの高周波電流を供給することをいう。   The present invention relates to a discharge tube equalizing lighting driving device for lighting a plurality of discharge tubes. Here, the “discharge tube” refers to a device that emits light by applying a high pressure to discharge into an ionized gas (plasma) in a sealed tube, such as a neon tube, a sodium lamp, a fluorescent tube, or a cold cathode tube. It corresponds to. “Uniform flow” means that high frequency currents having substantially the same magnitude are supplied to a plurality of discharge tubes.

液晶表示装置など各種表示装置のバックライトには、放電管の一種である冷陰極管( Cold Cathode Fluorescent Tube)が用いられる。この冷陰極管の点灯駆動には、従来から、インバータ回路を用いた高周波点灯方式が採用されている。
図８は、このインバータ回路を含む放電管均流点灯駆動装置の一例を示す回路図である。この放電管均流点灯駆動装置は、高周波交流電源を供給するためのスイッチング回路１０１と、高周波交流電源を昇圧するための主変圧器１０２と、その主変圧器１０２の二次側の出力回線に対して並列に接続される複数の放電管１０３と、各放電管１０３の一端又は両端に挿入され、各放電管１０３に互いに等しい電流を流すため各放電管１０３と直列に接続されたバラスト・キャパシタ(ballast capacitor)からなる均流回路１０４とを備えている。なおインバータ回路とは、スイッチング回路１０１と主変圧器１０２とを含む回路とする。 For the backlights of various display devices such as liquid crystal display devices, cold cathode fluorescent tubes are used. Conventionally, a high-frequency lighting method using an inverter circuit has been adopted for driving the cold cathode tubes.
FIG. 8 is a circuit diagram showing an example of a discharge tube uniform lighting driving device including the inverter circuit. This discharge tube equalizing lighting driving device includes a switching circuit 101 for supplying a high-frequency AC power source, a main transformer 102 for boosting the high-frequency AC power source, and an output line on the secondary side of the main transformer 102. A plurality of discharge tubes 103 connected in parallel to each other, and a ballast capacitor inserted in one end or both ends of each discharge tube 103 and connected in series with each discharge tube 103 in order to flow equal currents to each discharge tube 103 a current equalizing circuit 104 composed of a (ballast capacitor). Note that the inverter circuit is a circuit including the switching circuit 101 and the main transformer 102.

このような放電管均流点灯駆動装置においては、前記均流回路１０４を構成するキャパシタは、各放電管１０３の一端を支持する基板１０５上に、当該基板１０５と一体に形成されている。すなわち、図９に示すように、当該基板１０５の表面上に各放電管１０３に接続される各導体１０６を互いに分離して設け、当該基板１０５の裏面上に一枚の導体層１０７を設けて、それら表面及び裏面の導体層１０６，１０７の重なる領域に作られるキャパシタンスを利用して、均流回路１０４を構成している。   In such a discharge tube equalizing lighting driving device, the capacitor constituting the current equalizing circuit 104 is formed integrally with the substrate 105 on the substrate 105 supporting one end of each discharge tube 103. That is, as shown in FIG. 9, each conductor 106 connected to each discharge tube 103 is provided separately on the surface of the substrate 105, and one conductor layer 107 is provided on the back surface of the substrate 105. The current-dividing circuit 104 is configured by utilizing the capacitance formed in the overlapping region of the conductor layers 106 and 107 on the front and back surfaces.

放電管１０３の駆動は、インバータ回路から放電管に定格電圧（放電管の長さ等に応じた、放電管のメーカーから指定される電圧。例えば１０００Ｖ）、定格周波数（放電管のメーカーから指定される周波数。例えば６０ｋＨｚ）の高周波交流電源を供給することによって行っている。
特開2005-322479号公報 The discharge tube 103 is driven from the inverter circuit to the discharge tube at a rated voltage (a voltage specified by the discharge tube manufacturer according to the length of the discharge tube, for example, 1000 V), a rated frequency (specified by the discharge tube manufacturer). This is done by supplying a high-frequency AC power source having a frequency of 60 kHz, for example.
JP 2005-322479 A

ところが、前記放電管の点灯駆動時、特に低温起動時に、各放電管に均等な電流が流れないことがある。この電流の不均等は起動後も継続され、それがそのまま画面の明るさのムラにつながってしまう。
このような起動時の電流の不均等を防止するために、均流回路のキャパシタンスを小さくして、駆動電圧を高くすることが行われているが、駆動電圧を高くするとインバータ回路の主変圧器を大きくし、その耐圧も上げなければならない。このため、放電管均流点灯駆動装置の全体が大きくなり、また発熱量も増大する。 However, when the discharge tubes are turned on, particularly when starting at a low temperature, an equal current may not flow through each discharge tube. This current non-uniformity continues even after startup, which leads to uneven brightness of the screen.
In order to prevent such current non-uniformity at the time of start-up, it has been practiced to reduce the capacitance of the current-sharing circuit and increase the drive voltage, but when the drive voltage is increased, the main transformer of the inverter circuit Must be increased and its pressure resistance increased. For this reason, the whole discharge tube uniform lighting driving device becomes large, and the heat generation amount also increases.

そこで本発明は、各放電管の起動を確実に行うことができ、起動後も、各放電管に安定した均一の電流を流すことのできる放電管均流点灯駆動装置を提供することを目的とする。   Accordingly, an object of the present invention is to provide a discharge tube equalizing lighting driving device capable of reliably starting each discharge tube and allowing a stable and uniform current to flow through each discharge tube even after the start. To do.

本発明の放電管均流点灯駆動装置は、互いに並列に接続された複数の放電管を点灯駆動するための放電管均流点灯駆動装置であって、前記複数の放電管を支持し、前記複数の放電管との間に浮遊容量が形成されている支持部材と、高周波駆動電源を供給する第一のインバータ回路と、高周波駆動電源を供給する第二のインバータ回路とを備えるものである。   The discharge tube equalizing lighting driving device of the present invention is a discharge tube equalizing lighting driving device for driving and driving a plurality of discharge tubes connected in parallel to each other, and supports the plurality of discharge tubes, A support member in which a stray capacitance is formed between the discharge tube, a first inverter circuit that supplies high-frequency driving power, and a second inverter circuit that supplies high-frequency driving power.

前記第一のインバータ回路の高周波駆動電源の出力端から供給される高周波電流は、前記複数の放電管の一端から、前記浮遊容量を介して、前記支持部材に到達し、前記第一のインバータ回路の高周波駆動電源の接地端に還流する。前記第二のインバータ回路の高周波駆動電源の出力端から供給される高周波電流は、前記複数の放電管の他端から、前記浮遊容量を介して、前記支持部材に到達し、前記第二のインバータ回路の高周波駆動電源の接地端に還流する。   The high-frequency current supplied from the output end of the high-frequency drive power source of the first inverter circuit reaches the support member from one end of the plurality of discharge tubes via the stray capacitance, and the first inverter circuit Return to the ground terminal of the high frequency drive power supply. The high frequency current supplied from the output end of the high frequency drive power supply of the second inverter circuit reaches the support member from the other end of the plurality of discharge tubes via the stray capacitance, and the second inverter Return to the ground terminal of the circuit's high-frequency drive power supply.

この装置構成であれば、点灯時、前記第一のインバータ回路の前記出力端から、前記複数の放電管の一端に高周波電流が供給され、当該高周波電流は、前記浮遊容量、前記支持部材を通って、前記第一のインバータ回路に還流する。したがって、従来、支持部材に一部が逃げていた高周波電流を積極的に利用して放電管を点灯する。また、前記第二のインバータ回路の前記出力端から、前記複数の放電管の他端に高周波電流が供給され、当該高周波電流は、前記浮遊容量、前記支持部材を通って前記第二のインバータ回路に還流するので、放電管の暗端現象を補うことができる。   With this device configuration, at the time of lighting, a high-frequency current is supplied from the output end of the first inverter circuit to one end of the plurality of discharge tubes, and the high-frequency current passes through the stray capacitance and the support member. To the first inverter circuit. Therefore, the discharge tube is lit by positively utilizing the high-frequency current that has been partly escaping from the support member. In addition, a high frequency current is supplied from the output end of the second inverter circuit to the other end of the plurality of discharge tubes, and the high frequency current passes through the stray capacitance and the support member, and the second inverter circuit. Therefore, the dark end phenomenon of the discharge tube can be compensated.

前記第一のインバータ回路の高周波駆動電源に対して、前記第二のインバータ回路の高周波駆動電源の位相が所定角度ずれていることが好ましい。この位相のずれにより、各放電管と直列に接続された均流素子（例えばバラスト・キャパシタ）がなくても、各放電管の均流点灯が容易にできる。
特に、所定角度が０度を超え１８０度未満の任意の角度、又は１８０度を超え３６０度未満の任意の角度であることが望ましい。 It is preferable that the phase of the high frequency driving power source of the second inverter circuit is shifted by a predetermined angle with respect to the high frequency driving power source of the first inverter circuit. Due to this phase shift, even if there is no current-equalizing element (for example, a ballast capacitor) connected in series with each discharge tube, the current-equalization lighting of each discharge tube can be facilitated.
In particular, it is desirable that the predetermined angle is an arbitrary angle exceeding 0 degree and less than 180 degrees, or an arbitrary angle exceeding 180 degrees and less than 360 degrees.

前記第一のインバータ回路の高周波駆動電源と、前記第二のインバータ回路の高周波駆動電源とは、交互に切換えられて供給される構成であってもよい。これによれば、切換え状態に応じて、ある期間では前記複数の放電管の一端から支持部材へ高周波電流が流れ、他の期間では前記複数の放電管の他端から支持部材へ高周波電流が流れる。このようにして、放電管に供給される高周波電源の極性を、時間的に交互に逆にすることができ、輝度ムラを分散させることができる。また放電管の均流点灯が容易にできる。   The high-frequency driving power source for the first inverter circuit and the high-frequency driving power source for the second inverter circuit may be alternately switched and supplied. According to this, a high-frequency current flows from one end of the plurality of discharge tubes to the support member in a certain period according to the switching state, and a high-frequency current flows from the other end of the plurality of discharge tubes to the support member in the other period. . In this way, the polarity of the high-frequency power source supplied to the discharge tube can be alternately reversed with respect to time, and luminance unevenness can be dispersed. In addition, the discharge tube can be easily lit.

前記第一のインバータ回路の高周波駆動電源に対して、前記第二のインバータ回路の高周波駆動電源の周波数が異なっている構成であってもよい。この構成であれば、前記第一のインバータ回路の高周波駆動電源に対する、前記第二のインバータ回路の高周波駆動電源の位相差を、時間的に変化させることができるので、放電管の一部が暗くなる現象を補うことができるとともに、放電管の均流点灯が容易にできるようになる。   The high frequency drive power source of the first inverter circuit may have a different frequency from the high frequency drive power source of the second inverter circuit. With this configuration, the phase difference of the high-frequency driving power source of the second inverter circuit with respect to the high-frequency driving power source of the first inverter circuit can be temporally changed, so that a part of the discharge tube is darkened. The phenomenon described above can be compensated for, and the discharge tube can be easily lit.

前記放電管は、蛍光灯又は冷陰極管であってもよい。   The discharge tube may be a fluorescent lamp or a cold cathode tube.

以上のように本発明によれば、特に均流素子を必要としなくても放電管の起動が容易にでき、起動後、放電管に流れる電流の不均等化を防止し、各放電管の明るさを均等にすることができる。   As described above, according to the present invention, the start-up of the discharge tube can be facilitated without requiring a current-equalizing element, and the current flowing in the discharge tube can be prevented from becoming uneven after the start-up. Can be made even.

以下、本発明の実施の形態を、添付図面を参照しながら詳細に説明する。
図１は、本発明が適用される液晶表示装置１０を示す分解図である。この液晶表示装置１０は、液晶表示部１１と、液晶表示部１１を支持する液晶パネル１２と、均流点灯駆動装置本体１３とを備えている。
均流点灯駆動装置本体１３は、その一部又は全部が金属で構成されるとともに接地された支持板１４に複数の冷陰極管１５が配置されたものであり、これらの冷陰極管１５は互いに並列に接続され、インバータ回路に接続される。複数の冷陰極管１５と、支持板１４及びその周辺に配置されている導電性の部材（支持板１４を固定する金具など）との間には、浮遊容量又は寄生容量が形成される。これにより複数の冷陰極管１５と支持板１４は高周波的につながっている。なお複数の冷陰極管１５のそれぞれを示すとき、冷陰極管１５１〜１５ｎと表記することがある。ｎは冷陰極管の本数（ｎ＞＝２）である。 Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an exploded view showing a liquid crystal display device 10 to which the present invention is applied. The liquid crystal display device 10 includes a liquid crystal display unit 11, a liquid crystal panel 12 that supports the liquid crystal display unit 11, and a uniform current lighting drive device main body 13.
A part of or all of the uniform current lighting drive device body 13 is made of metal, and a plurality of cold cathode tubes 15 are arranged on a grounded support plate 14. These cold cathode tubes 15 are mutually connected. Connected in parallel and connected to the inverter circuit. A stray capacitance or a parasitic capacitance is formed between the plurality of cold cathode fluorescent lamps 15 and the support plate 14 and conductive members (such as a metal fitting for fixing the support plate 14) disposed around the support plate 14. Thereby, the plurality of cold cathode fluorescent lamps 15 and the support plate 14 are connected in high frequency. In addition, when each of the several cold cathode tube 15 is shown, it may describe with the cold cathode tubes 151-15n. n is the number of cold cathode tubes (n> = 2).

液晶表示部１１は、例えば４：３，１６：９などの横長形状である。なお液晶表示部１１の構造は公知のものであり、例えば、表面側の透明基板と光源側の透明基板とを向き合わせた構造になっている。液晶駆動方式はパッシブマトリクス型でもアクティブマトリクス型でもよい。アクティブマトリクス型を例に挙げると、表面側の透明基板の内面には複数のマトリクス状透明電極群を配列し、光源側の透明基板の内面にはマトリクス状透明電極群と対向するように１枚の半透明電極を設置している。さらに、それぞれの電極の上に、一定方向にラビングした樹脂からなる配向膜を形成している。そして両配向膜の間に液晶を封入している。なお、カラー液晶の場合は、表面側の透明基板にカラーフィルター層が設けられている。   The liquid crystal display unit 11 has a horizontally long shape such as 4: 3, 16: 9, for example. The structure of the liquid crystal display unit 11 is a known structure, for example, a structure in which a transparent substrate on the surface side and a transparent substrate on the light source side face each other. The liquid crystal driving method may be a passive matrix type or an active matrix type. Taking the active matrix type as an example, a plurality of matrix-like transparent electrode groups are arranged on the inner surface of the transparent substrate on the surface side, and one sheet is arranged on the inner surface of the transparent substrate on the light source side so as to face the matrix-like transparent electrode group. The semi-transparent electrode is installed. Further, an alignment film made of a resin rubbed in a certain direction is formed on each electrode. Liquid crystal is sealed between the alignment films. In the case of color liquid crystal, a color filter layer is provided on the transparent substrate on the front side.

均流点灯駆動装置本体１３は、ｎ本の冷陰極管１５１〜１５ｎを、液晶表示部１１の長辺方向と平行に配列している。各冷陰極管１５１〜１５ｎの一端部のリード線及び他端部のリード線は、給電基板１６の電極にそれぞれ接続されている。これらの給電基板１６の電極が後述するインバータ回路の高周波電源供給端２５ａ，２５ｂに接続される。
図２は、２つのインバータ回路２０，３０及びそれに接続された複数の冷陰極管１５１〜１５ｎを含む均流点灯駆動装置の全体回路図である。 The uniform current lighting drive device main body 13 has n cold cathode tubes 151 to 15 n arranged in parallel with the long side direction of the liquid crystal display unit 11. The lead wires at one end and the lead wires at the other end of each of the cold cathode tubes 151 to 15 n are connected to electrodes of the power supply substrate 16, respectively. The electrodes of the power supply substrate 16 are connected to high frequency power supply terminals 25a and 25b of an inverter circuit described later.
FIG. 2 is an overall circuit diagram of a uniform current lighting driving device including two inverter circuits 20 and 30 and a plurality of cold cathode tubes 151 to 15n connected thereto.

インバータ回路２０は、商用交流電源２２ａに接続されたスイッチＳＷ及び整流回路２２ｂと、整流回路２２ｂの直流出力に基づいて高周波交流電源を得るためのスイッチング回路２３と、高周波交流電源を昇圧するための主変圧器２４と、その主変圧器２４の出力回線に接続され、高周波駆動電源を供給するための高周波電源供給端２５ａと、を備えている。   The inverter circuit 20 includes a switch SW and a rectifier circuit 22b connected to the commercial AC power supply 22a, a switching circuit 23 for obtaining a high-frequency AC power supply based on the DC output of the rectifier circuit 22b, and a voltage booster for the high-frequency AC power supply. A main transformer 24 and a high frequency power supply end 25a connected to the output line of the main transformer 24 for supplying high frequency driving power are provided.

インバータ回路３０は、整流回路２２ｂの直流出力に基づいて高周波交流電源を得るためのスイッチング回路３３と、高周波交流電源を昇圧するための主変圧器３４と、その主変圧器３４の出力回線に接続され、高周波駆動電源を供給するための高周波電源供給端２５ｂと、を備えている。
高周波電源供給端２５ａ，２５ｂに対して、複数の冷陰極管１５１〜１５ｎの一端及び他端がそれぞれ接続されている。また、主変圧器２４の高周波電源供給端２５ａと反対の端と、主変圧器３４の高周波電源供給端２５ｂと反対の端とは、それぞれ支持板１４と同じ電位になるように接地されている。 The inverter circuit 30 is connected to a switching circuit 33 for obtaining a high-frequency AC power source based on the DC output of the rectifier circuit 22b, a main transformer 34 for boosting the high-frequency AC power source, and an output line of the main transformer 34. And a high frequency power supply end 25b for supplying a high frequency drive power.
One end and the other end of the plurality of cold cathode fluorescent lamps 151 to 15n are connected to the high frequency power supply ends 25a and 25b, respectively. Further, the end opposite to the high frequency power supply end 25a of the main transformer 24 and the end opposite to the high frequency power supply end 25b of the main transformer 34 are grounded so as to have the same potential as the support plate 14, respectively. .

スイッチング回路２３は、スイッチング動作をするトランジスタＴｒ１，Ｔｒ２とキャパシタＣｓ１，Ｃｓ２とからなるブリッジ回路を含んでいる。トランジスタＴｒ１，Ｔｒ２の各ゲートには、２つの互いに逆位相の高周波パルス電圧を供給するためのクロックパルス回路２３ａが接続されている。このクロックパルス回路２３ａは、既定周波数ｆ１の交流信号の半サイクルが入るごとに２つの高周波パルス電圧の位相を１８０°切り替える。既定周波数ｆ１は、冷陰極管１５を起動し起動後も点灯を続けるために必要な周波数であり、例えば数十ｋＨｚ〜数百ｋＨｚの範囲の中から選ばれる。   The switching circuit 23 includes a bridge circuit including transistors Tr1 and Tr2 that perform a switching operation and capacitors Cs1 and Cs2. Two gates of the transistors Tr1 and Tr2 are connected to a clock pulse circuit 23a for supplying two high-frequency pulse voltages with opposite phases. The clock pulse circuit 23a switches the phase of the two high-frequency pulse voltages by 180 ° every time a half cycle of the AC signal having the predetermined frequency f1 is entered. The predetermined frequency f1 is a frequency necessary for starting the cold cathode tube 15 and continuing lighting after the start-up, and is selected from a range of several tens kHz to several hundred kHz, for example.

主変圧器２４は、所定の巻き数と巻き数比を持つことによって、交流電圧を所定の昇圧比で昇圧する。これによって、各冷陰極管１５１〜１５ｎの点灯に必要な交流電圧Ｖｄ（冷陰極管の長さに応じて決まる、通常１０００Ｖ〜２０００Ｖ程度）を得ることができる。
スイッチング回路３３も、スイッチング回路２３と同様、スイッチング動作をするトランジスタＴｒ３，Ｔｒ４とキャパシタＣｓ３，Ｃｓ４とからなるブリッジ回路を含んでいる。トランジスタＴｒ３，Ｔｒ４の各ゲートには、２つの互いに逆位相の高周波パルス電圧を供給するためのクロックパルス回路３３ａが接続されている。このクロックパルス回路３３ａの信号入力端子ＣＰと、前記クロックパルス回路２３ａの信号入力端子ＣＰとは抵抗Ｒｕで接続されている。また、クロックパルス回路３３ａの信号入力端子ＣＰとコールド側回線との間には、キャパシタＣｕが接続されている。これらの抵抗ＲｕとキャパシタＣｕとで遅延時定数ＲｕＣｕを形成する。 The main transformer 24 boosts the AC voltage at a predetermined boost ratio by having a predetermined number of turns and a turn ratio. As a result, it is possible to obtain an AC voltage Vd (normally about 1000 V to 2000 V, which is determined according to the length of the cold cathode tube) necessary for lighting the cold cathode tubes 151 to 15n.
Similarly to the switching circuit 23, the switching circuit 33 includes a bridge circuit including transistors Tr3 and Tr4 that perform a switching operation and capacitors Cs3 and Cs4. Two gates of the transistors Tr3 and Tr4 are connected to a clock pulse circuit 33a for supplying two high-frequency pulse voltages having opposite phases. The signal input terminal CP of the clock pulse circuit 33a and the signal input terminal CP of the clock pulse circuit 23a are connected by a resistor Ru. A capacitor Cu is connected between the signal input terminal CP of the clock pulse circuit 33a and the cold side line. These resistor Ru and capacitor Cu form a delay time constant RuCu.

この時定数ＲｕＣｕは、既定周波数ｆ１の交流波の所定の位相角φに相当する時間に選ばれる。位相角φは、０度以上３６０度未満の任意の角度に設定することができる。位相角φ＝０度にするには、抵抗ＲｕとキャパシタＣｕのいずれか若しくは両方の値を０にすればよい。
主変圧器３４も、主変圧器２４と同様、所定の巻き数と巻き数比を持つことによって、交流電圧を所定の昇圧比で昇圧する。これによって、各冷陰極管１５１〜１５ｎの点灯に必要な交流電圧Ｖｄ′（冷陰極管の長さに応じて決まる、通常１０００Ｖ〜２０００Ｖ程度）を得ることができる。 This time constant RuCu is selected at a time corresponding to a predetermined phase angle φ of the AC wave having the predetermined frequency f1. The phase angle φ can be set to any angle between 0 ° and less than 360 °. In order to set the phase angle φ = 0 degree, the value of either or both of the resistor Ru and the capacitor Cu may be set to zero.
Similarly to the main transformer 24, the main transformer 34 has a predetermined number of turns and a turn ratio, thereby boosting the AC voltage at a predetermined step-up ratio. As a result, it is possible to obtain an AC voltage Vd ′ (normally about 1000 V to 2000 V, which is determined according to the length of the cold cathode tube) necessary for lighting the cold cathode tubes 151 to 15n.

インバータ回路２０によって得られる交流電圧Ｖｄと、インバータ回路３０によって得られる交流電圧Ｖｄ′とは、互いに等しい電圧であっても良く、異なる電圧であっても良い。
このインバータ回路２０の動作説明をすると、商用交流電源２２ａのスイッチオン後、整流回路２２ｂによって得られた直流電源は、スイッチング回路２３によって高周波電源に変換され主変圧器２４に供給される。 The AC voltage Vd obtained by the inverter circuit 20 and the AC voltage Vd ′ obtained by the inverter circuit 30 may be the same voltage or different voltages.
The operation of the inverter circuit 20 will be described. After the commercial AC power supply 22a is switched on, the DC power obtained by the rectifier circuit 22b is converted into a high frequency power by the switching circuit 23 and supplied to the main transformer 24.

このスイッチング回路２３の交流周波数の範囲は、主変圧器２４として十分な変換効率が得られる周波数であることが必要であり、前述したように数十ｋＨｚ〜数百ｋＨｚの範囲の中から選ばれる。前記範囲は、好ましくは、２０ｋＨｚ〜２００ｋＨｚである。周波数がこの数十ｋＨｚ〜数百ｋＨｚの範囲より低すぎると、特に低温時に冷陰極管１５の起動が困難になることがある。周波数がこの範囲よりも高いと、主変圧器２４内部で発生する浮遊容量の影響が大きくなり、共振が発生して変換効率が低下する。   The range of the AC frequency of the switching circuit 23 needs to be a frequency at which sufficient conversion efficiency can be obtained as the main transformer 24, and is selected from the range of several tens of kHz to several hundreds of kHz as described above. . The range is preferably 20 kHz to 200 kHz. If the frequency is lower than the range of several tens of kHz to several hundreds of kHz, it may be difficult to start the cold cathode tube 15 particularly at a low temperature. If the frequency is higher than this range, the effect of stray capacitance generated inside the main transformer 24 becomes large, resonance occurs, and conversion efficiency decreases.

一方、スイッチング回路３３は、スイッチング回路２３の高周波交流電源から位相角φずれた高周波交流電源を主変圧器３４に提供する。
主変圧器２４，３４によって昇圧された各高周波電源は、高周波電源供給端２５ａ，２５ｂから、各冷陰極管１５１〜１５ｎの両端に供給される。これらの高周波電流を図２に“Ｉ１，Ｉ２”で示す。高周波電流Ｉ１は、各冷陰極管１５１〜１５ｎの内部を通って、各冷陰極管１５１〜１５ｎと支持板１４との間に分布した状態で形成されている浮遊容量を通過することによって、接地側へ流れていく。高周波電流Ｉ２も、各冷陰極管１５１〜１５ｎの内部を通って、各冷陰極管１５１〜１５ｎと支持板１４との間に分布した状態で形成されている浮遊容量を通過することによって、接地側へ流れていく。 On the other hand, the switching circuit 33 provides the main transformer 34 with a high-frequency AC power source that is shifted in phase angle φ from the high-frequency AC power source of the switching circuit 23.
The high frequency power sources boosted by the main transformers 24 and 34 are supplied to both ends of the cold cathode tubes 151 to 15n from the high frequency power source supply ends 25a and 25b. These high-frequency currents are indicated by “I1, I2” in FIG. The high-frequency current I1 passes through the inside of each cold cathode tube 151-15n and passes through the stray capacitance formed in a state distributed between each cold cathode tube 151-15n and the support plate 14, thereby grounding. It flows to the side. The high-frequency current I2 is also grounded by passing through the inside of each cold cathode tube 151-15n and passing through the stray capacitance formed in a state distributed between each cold cathode tube 151-15n and the support plate 14. It flows to the side.

ここで、高周波電流Ｉ１のみを流す場合を想定する。高周波電流Ｉ１は、各冷陰極管１５の一端から冷陰極管内部に注入されるものであり、冷陰極管１５の浮遊容量を通過して接地側へ流れていくので、冷陰極管１５の他端に近づくほど電流値が低下する。このため、冷陰極管１５の他端に近い部分が暗くなる傾向がある。
高周波電流Ｉ２のみを流す場合も同様であり、冷陰極管１５の一端に近い部分が暗くなる傾向がある。 Here, it is assumed that only the high-frequency current I1 flows. The high-frequency current I1 is injected into the cold cathode tube from one end of each cold cathode tube 15 and flows to the ground side through the stray capacitance of the cold cathode tube 15. The closer to the edge, the lower the current value. For this reason, the portion close to the other end of the cold cathode tube 15 tends to be dark.
The same applies to the case where only the high-frequency current I2 is passed, and the portion near one end of the cold cathode tube 15 tends to be dark.

そこで、高周波電流Ｉ１と高周波電流Ｉ２とを同時に冷陰極管１５の両端から流す。
まず高周波電流Ｉ１と高周波電流Ｉ２との間に位相差がない場合（φ＝０度）を想定すると、冷陰極管１５の両端に同位相の電圧をかけることとなり、冷陰極管１５の端に近い部分が暗くなる傾向を無くすことができる。これは、高周波電流Ｉ１のみを流すことによって起こる冷陰極管１５の他端が暗くなる減少を高周波電流Ｉ２が補い、高周波電流Ｉ２のみを流すことによって起こる冷陰極管１５の一端が暗くなる減少を高周波電流Ｉ１が補うからである。 Therefore, the high-frequency current I1 and the high-frequency current I2 are simultaneously supplied from both ends of the cold cathode tube 15.
First, assuming that there is no phase difference between the high-frequency current I1 and the high-frequency current I2 (φ = 0 degrees), a voltage having the same phase is applied to both ends of the cold cathode tube 15, and the end of the cold cathode tube 15 is applied. It is possible to eliminate the tendency for the near part to become dark. This is because the high-frequency current I2 compensates for the decrease in the other end of the cold cathode tube 15 caused by flowing only the high-frequency current I1, and the decrease in the one end of the cold-cathode tube 15 caused by flowing only the high-frequency current I2. This is because the high-frequency current I1 compensates.

次に高周波電流Ｉ１と高周波電流Ｉ２との位相が逆相の場合（φ＝１８０度）を想定すると、既定周波数ｆ１の信号のある半サイクルには、冷陰極管１５の一端から他端まで高周波電流が流れるとともに、他の半サイクルには、冷陰極管１５の他端から一端まで高周波電流が流れる。従って、冷陰極管１５の端から端まで流れる大きな高周波電流が流れるので、冷陰極管１５の一端が暗くなる減少を補うことができる。   Next, assuming that the phases of the high-frequency current I1 and the high-frequency current I2 are opposite (φ = 180 degrees), the high-frequency current from one end to the other end of the cold cathode tube 15 is in a half cycle with a signal of the predetermined frequency f1. As current flows, high-frequency current flows from the other end to the other end of the cold cathode tube 15 in the other half cycle. Accordingly, since a large high-frequency current flowing from one end to the other end of the cold cathode tube 15 flows, it is possible to compensate for the decrease in the darkness of the one end of the cold cathode tube 15.

次に高周波電流Ｉ１と高周波電流Ｉ２との間の位相差φを、前記φ＝０度、φ＝１８０度以外の角度、すなわち０度を超え１８０度未満の任意の角度、又は１８０度を超え３６０度未満の任意の角度に設定した場合の効果を検討する。
図３は、高周波電源供給端２５ａの電圧波形と、高周波電源供給端２５ｂの電圧波形とを対比して示すグラフである。２５ｂの電圧波形は、２５ａの電圧波形と比べて、位相が、この例では９０°遅れている。このため、φ＝０度、φ＝１８０度の場合と比較して次のような効果がある。 Next, the phase difference φ between the high-frequency current I1 and the high-frequency current I2 is set to an angle other than φ = 0 degrees and φ = 180 degrees, that is, an arbitrary angle exceeding 0 degrees and less than 180 degrees, or exceeding 180 degrees. Consider the effect of setting an arbitrary angle of less than 360 degrees.
FIG. 3 is a graph showing the voltage waveform of the high-frequency power supply end 25a in comparison with the voltage waveform of the high-frequency power supply end 25b. The phase of the voltage waveform of 25b is delayed by 90 ° in this example as compared with the voltage waveform of 25a. For this reason, there are the following effects compared with the case of φ = 0 degrees and φ = 180 degrees.

まず冷陰極管１５の両端に同相（φ＝０度）の電圧が印加される場合と比較する。
冷陰極管１５の両端に同相（φ＝０度）の電圧が印加される場合、電流は、支持板１４など冷陰極管１５の周囲に存在する電圧の低い部材に流れ、冷陰極管１５の端から端まで流れにくい。特に、冷陰極管１５の両端に同相かつ、ほぼ同じ大きさの電圧が印加されたとき、冷陰極管１５の中央部が最も低い電位になり、各冷陰極管１５１〜１５ｎの両端から中央部１７ｃに近づくほど電流値が低下し、電流は冷陰極管１５の中央部を乗り超えることができなくなってしまう。このため、冷陰極管１５に流れる電流は全体として少なくなり、特に中央部が最も暗くなる。 First, a comparison is made with a case where a voltage of the same phase (φ = 0 degree) is applied to both ends of the cold cathode tube 15.
When a voltage having the same phase (φ = 0 degrees) is applied to both ends of the cold cathode tube 15, the current flows through a member having a low voltage, such as the support plate 14, around the cold cathode tube 15. Difficult to flow from end to end. In particular, when a voltage having the same phase and substantially the same magnitude is applied to both ends of the cold cathode tube 15, the central portion of the cold cathode tube 15 is at the lowest potential, and the central portion from both ends of each cold cathode tube 151 to 15n. As the value approaches 17c, the current value decreases, and the current cannot get over the central portion of the cold cathode tube 15. For this reason, the electric current which flows into the cold cathode tube 15 decreases as a whole, and especially a center part becomes the darkest.

そこで、高周波電源供給端２５ａの電圧波形と高周波電源供給端２５ｂの電圧波形との位相差φを、０度又は３６０度以外の任意の位相にすれば、冷陰極管１５１〜１５ｎの両端に電圧差が生じるので、電流の一部は、冷陰極管１５１〜１５ｎの一端から他端にまで流れる。したがって、φ＝０度の場合と比べて、中央部がやや暗くなる傾向が緩和されるという利点がある。   Therefore, if the phase difference φ between the voltage waveform of the high-frequency power supply end 25a and the voltage waveform of the high-frequency power supply end 25b is set to an arbitrary phase other than 0 degrees or 360 degrees, the voltage is applied to both ends of the cold cathode tubes 151 to 15n. Since a difference occurs, a part of the current flows from one end of the cold cathode fluorescent lamps 151 to 15n to the other end. Therefore, there is an advantage that the tendency of the central portion to become slightly darker is reduced as compared with the case where φ = 0 degrees.

次に、冷陰極管１５の両端に逆相（φ＝１８０度）の電圧が印加される場合と比較する。
冷陰極管１５の両端に逆相（φ＝１８０度）の電圧が印加されると高周波電流は、冷陰極管１５と支持板１４との間に形成されている浮遊容量を通して接地側へ流れていくものも少しあるが、ほとんど冷陰極管１５の端から端まで流れるので、冷陰極管１５に大きな電流が流れる。 Next, a comparison is made with a case where a reverse phase (φ = 180 degrees) voltage is applied to both ends of the cold cathode tube 15.
When a reverse-phase voltage (φ = 180 degrees) is applied to both ends of the cold cathode tube 15, the high-frequency current flows to the ground side through the stray capacitance formed between the cold cathode tube 15 and the support plate 14. Although there are a few things, almost all of the cold cathode tube 15 flows from end to end, so that a large current flows through the cold cathode tube 15.

この場合、各冷陰極管１５１〜１５ｎには、一端から他端に流れる大きな電流によって、それぞれ負性抵抗特性に基づく一定の電圧降下が発生する。「負性抵抗特性」とは、各冷陰極管１５１〜１５ｎの端から端までが均一に点灯することにより、冷陰極管１５に流れる電流が大きくなるほど冷陰極管１５の電圧が低くなっていく状態をいう。この「負性抵抗特性」によって、各冷陰極管１５１〜１５ｎに、点灯ムラが発生する。すなわちある冷陰極管１５１が明るくなり、他の冷陰極管１５２が暗くなる、という状態がスイッチオフするまで続く。   In this case, a constant voltage drop based on the negative resistance characteristic occurs in each of the cold cathode tubes 151 to 15n due to a large current flowing from one end to the other end. “Negative resistance characteristics” means that the cold cathode fluorescent lamps 15-15n are lit uniformly from end to end, and the voltage of the cold cathode fluorescent lamps 15 decreases as the current flowing through the cold cathode fluorescent lamps 15 increases. State. Due to this “negative resistance characteristic”, lighting unevenness occurs in each of the cold cathode fluorescent lamps 151 to 15n. That is, a state in which one cold cathode tube 151 becomes bright and another cold cathode tube 152 becomes dark continues until it is switched off.

そこで、位相φを、逆相（φ＝１８０度）以外の値に設定すると、冷陰極管１５の端から端まで流れる電流は減少し、冷陰極管１５と支持板１４との間に形成されている浮遊容量を通して接地側へ流れていく電流が増大する。このため、冷陰極管１５内に不均一な電流分布が発生する。すなわち、冷陰極管１５内に電流の小さい部分が生じる。この電流の小さい部分は、冷陰極管１５内に「正抵抗特性」を発生させる。「正抵抗特性」とは、冷陰極管１５に流れる電流が上がるほど冷陰極管１５の電圧が上がっていく状態をいう。この「正抵抗特性」による電圧降下を実現することによって、点灯時、各冷陰極管１５１〜１５ｎの個体差を吸収して、各冷陰極管１５１〜１５ｎに均等の電流を供給することができ、均等に点灯させることができる。   Therefore, when the phase φ is set to a value other than the reverse phase (φ = 180 degrees), the current flowing from one end of the cold cathode tube 15 to the other is reduced and formed between the cold cathode tube 15 and the support plate 14. The current flowing to the ground side through the stray capacitance increases. For this reason, non-uniform current distribution occurs in the cold cathode tube 15. That is, a portion with a small current is generated in the cold cathode tube 15. This portion with a small current generates a “positive resistance characteristic” in the cold cathode tube 15. The “positive resistance characteristic” refers to a state in which the voltage of the cold cathode tube 15 increases as the current flowing through the cold cathode tube 15 increases. By realizing the voltage drop due to this “positive resistance characteristic”, it is possible to supply individual currents to the cold cathode tubes 151 to 15n by absorbing the individual differences of the cold cathode tubes 151 to 15n at the time of lighting. Can be lit evenly.

図３を用いて、数値例を挙げて説明する。図３において、高周波電源供給端２５ａの電圧波形が最大の時点をｔ１とし、高周波電源供給端２５ａの電圧波形が負側に最大の時点をｔ３とする。高周波電源供給端２５ｂの電圧波形が最大の時点をｔ２とし、高周波電源供給端２５ｂの電圧波形が負側に最大の時点をｔ４とする。
冷陰極管１５の定格電流が５ｍＡとする。時点ｔ１では、高周波電源供給端２５ａから高周波電流Ｉ１のみが供給される。高周波電流Ｉ２は０である。高周波電流Ｉ１は、冷陰極管１５の一端では最大だが、冷陰極管１５を流れていくうちに、浮遊容量を通して接地側へ逃げて行くため、冷陰極管１５の他端では最小になる。例えば冷陰極管１５の一端では９ｍＡ、中央部では５ｍＡ、他端では１ｍＡとする。このため他端では、電流値が１ｍＡと小さくなり、「正抵抗特性」が実現する。この正抵抗特性に基づく一定の電圧降下を実現することによって、点灯時、各冷陰極管１５１〜１５ｎの個体差を吸収して、各冷陰極管１５１〜１５ｎに均等の電流を供給することができ、均等に点灯させることができる。 A numerical example will be described with reference to FIG. In FIG. 3, the time point when the voltage waveform of the high frequency power supply end 25a is maximum is t1, and the time point when the voltage waveform of the high frequency power supply end 25a is negative is the maximum. A point in time when the voltage waveform at the high frequency power supply end 25b is maximum is t2, and a point when the voltage waveform at the high frequency power supply end 25b is negative is t4.
The rated current of the cold cathode tube 15 is 5 mA. At time t1, only the high frequency current I1 is supplied from the high frequency power supply end 25a. The high frequency current I2 is zero. The high-frequency current I1 is maximum at one end of the cold-cathode tube 15, but escapes to the ground side through the stray capacitance while flowing through the cold-cathode tube 15. Therefore, the high-frequency current I1 is minimum at the other end of the cold-cathode tube 15. For example, it is 9 mA at one end of the cold cathode tube 15, 5 mA at the center, and 1 mA at the other end. For this reason, at the other end, the current value becomes as small as 1 mA, and the “positive resistance characteristic” is realized. By realizing a constant voltage drop based on this positive resistance characteristic, the individual difference of each cold cathode tube 151-15n can be absorbed and an equal current can be supplied to each cold cathode tube 151-15n at the time of lighting. Can be lit evenly.

時点ｔ２では、高周波電源供給端２５ｂから高周波電流Ｉ２のみが供給される。高周波電流Ｉ２は０である。高周波電流Ｉ２は、冷陰極管１５の他端では最大だが、冷陰極管１５を流れていくうちに、浮遊容量を通して接地側へ逃げて行くため、冷陰極管１５の一端では最小になる。例えば冷陰極管１５の他端では９ｍＡ、中央部では５ｍＡ、一端では１ｍＡとする。このため一端では、電流が小さくなり、「正抵抗特性」が実現する。この正抵抗特性に基づく一定の電圧降下を実現することによって、点灯時、各冷陰極管１５１〜１５ｎの個体差を吸収して、各冷陰極管１５１〜１５ｎに均等の電流を供給することができ、均等に点灯させることができる。   At time t2, only the high frequency current I2 is supplied from the high frequency power supply end 25b. The high frequency current I2 is zero. The high-frequency current I2 is maximum at the other end of the cold cathode tube 15, but escapes to the ground side through the stray capacitance as it flows through the cold cathode tube 15, and thus becomes minimum at one end of the cold cathode tube 15. For example, the other end of the cold cathode tube 15 is 9 mA, the central portion is 5 mA, and the other end is 1 mA. For this reason, at one end, the current becomes small, and a “positive resistance characteristic” is realized. By realizing a constant voltage drop based on this positive resistance characteristic, the individual difference of each cold cathode tube 151-15n can be absorbed and an equal current can be supplied to each cold cathode tube 151-15n at the time of lighting. Can be lit evenly.

時点ｔ３では、高周波電源供給端２５ａから高周波電流Ｉ１のみが供給され高周波電流Ｉ２は０である。時点ｔ１と比べると、電流の方向が異なるだけであり、各冷陰極管１５１〜１５ｎを均等に点灯させることができるという効果は同じである。
時点ｔ４では、高周波電源供給端２５ｂから高周波電流Ｉ２のみが供給され高周波電流Ｉ１は０である。時点ｔ２と比べると、電流の方向が異なるだけであり、各冷陰極管１５１〜１５ｎを均等に点灯させることができるという効果は同じである。 At time t3, only the high-frequency current I1 is supplied from the high-frequency power supply end 25a, and the high-frequency current I2 is zero. Compared with the time t1, only the direction of the current is different, and the effect that each of the cold cathode fluorescent lamps 151 to 15n can be lighted equally is the same.
At time t4, only the high frequency current I2 is supplied from the high frequency power supply end 25b, and the high frequency current I1 is zero. Compared with the time point t2, only the direction of the current is different, and the effect that each of the cold cathode fluorescent lamps 151 to 15n can be lighted equally is the same.

なお、以上の図３の例では、位相差φ＝９０度の場合を説明したが、位相差が０度を超え１８０度未満の任意の角度、又は１８０度を超え３６０度未満の任意の角度である場合にも、同じような現象を起こすことができる。
以上のことをまとめると、次のようなことが言える。
（１）位相差φ＝０度，３６０度：均流点灯は最も容易。中央部暗くなる傾向。 In the example of FIG. 3 described above, the case where the phase difference φ is 90 degrees has been described. However, any angle where the phase difference exceeds 0 degree and less than 180 degrees, or any angle where the phase difference exceeds 180 degrees and less than 360 degrees. Even in this case, the same phenomenon can be caused.
In summary, the following can be said.
(1) Phase difference φ = 0 °, 360 °: Uniform lighting is the easiest. Tends to darken the center.

（２）位相差φ＝１８０度：均流点灯が難しくなる。管内での明るさの分布は最も均等。
（３）位相差φが、０度を超え１８０度未満の角度、又は１８０度を超え３６０度未満：均流点灯容易。中央部暗くならない。
特に位相差φが９０度に近い場合又は２７０度に近い場合、均流点灯容易であり、中央部も暗くならないという、最もバランスのよい効果が得られる。 (2) Phase difference φ = 180 degrees: Uniform lighting is difficult. The distribution of brightness within the tube is the most uniform.
(3) The phase difference φ is greater than 0 degree and less than 180 degrees, or more than 180 degrees and less than 360 degrees. It will not darken in the center.
In particular, when the phase difference φ is close to 90 degrees or close to 270 degrees, it is easy to perform uniform current lighting, and the most balanced effect that the central portion does not become dark can be obtained.

以下、本発明の実施の形態の変形例を説明する。
図４は、スイッチング回路２３，３３内で抵抗ＲｕとキャパシタＣｕとで遅延回路を形成するのに代えて、高周波電源供給端２５ａ，２５ｂのいずれか、例えば高周波電源供給端２５ｂと複数の冷陰極管１５１〜１５ｎの他端との間に、進相素子又は遅相素子２８を挿入した回路図である。 Hereinafter, modifications of the embodiment of the present invention will be described.
In FIG. 4, instead of forming a delay circuit with the resistor Ru and the capacitor Cu in the switching circuits 23 and 33, one of the high-frequency power supply terminals 25a and 25b, for example, the high-frequency power supply terminal 25b and a plurality of cold cathodes. It is the circuit diagram which inserted the phase advance element or the late phase element 28 between the other ends of the pipe | tubes 151-15n.

進相素子としてキャパシタ、遅相素子としてチョークコイルを採用することができる。この進相素子又は遅相素子２８により、前記複数の冷陰極管の一端と他端に印加される高周波電圧の位相をずらすことができる。
なお、高周波電源供給端２５ａと前記複数の冷陰極管１５の一端との間に進相素子を挿入し、高周波電源供給端２５ｂと前記複数の冷陰極管１５の他端との間に遅相素子を挿入してもよい。また高周波電源供給端２５ａと前記複数の冷陰極管１５の一端との間に遅相素子を挿入し、高周波電源供給端２５ｂと前記複数の冷陰極管１５の他端との間に進相素子を挿入してもよい。 A capacitor can be used as the phase advance element, and a choke coil can be used as the slow phase element. The phase advance element or the phase delay element 28 can shift the phase of the high-frequency voltage applied to one end and the other end of the plurality of cold-cathode tubes.
A phase advance element is inserted between the high frequency power supply end 25a and one end of the plurality of cold cathode tubes 15, and a slow phase is inserted between the high frequency power supply end 25b and the other ends of the plurality of cold cathode tubes 15. An element may be inserted. Further, a slow phase element is inserted between the high frequency power supply end 25 a and one end of the plurality of cold cathode tubes 15, and a phase advance element is inserted between the high frequency power supply end 25 b and the other ends of the plurality of cold cathode tubes 15. May be inserted.

次に、前記クロックパルス回路２３ａの信号入力端子ＣＰに印加される交流信号と、クロックパルス回路３３ａの信号入力端子ＣＰに印加される交流信号とを、ＩＣ切換回路２７で切り替える回路例を、図５を用いて説明する。
この回路例では、ＩＣ切換回路２７の状態に応じて、ある期間では高周波電源供給端２５ａから冷陰極管１５へ高周波電流を流し、他の期間では高周波電源供給端２５ｂから冷陰極管１５の他端からへ高周波電流を流す。 Next, a circuit example in which an IC switching circuit 27 switches between an AC signal applied to the signal input terminal CP of the clock pulse circuit 23a and an AC signal applied to the signal input terminal CP of the clock pulse circuit 33a is shown in FIG. 5 will be described.
In this circuit example, depending on the state of the IC switching circuit 27, a high-frequency current is supplied from the high-frequency power supply end 25a to the cold cathode tube 15 in a certain period, and the cold cathode tube 15 is supplied from the high-frequency power supply end 25b in another period. A high frequency current flows from the end.

ＩＣ切換回路２７の端子を１，２，３と表記する。端子３が既定周波数ｆ１の交流信号供給端に接続される共通端子であり、端子１はクロックパルス回路２３ａに、端子２はクロックパルス回路３３ａに接続される。
この図５の回路では、ＩＣ切換回路２７が端子１側につながる期間、高周波電源供給端２５ａから冷陰極管１５の一端につながる。冷陰極管１５の他端には電圧がかからない（主変圧器３４の二次側コイルで絶縁されている状態）ので、高周波電流は、冷陰極管１５の一端から支持板１４に流れる。ＩＣ切換回路２７が端子２側に接続される期間、高周波電流は、冷陰極管１５の他端から支持板１４に流れる。ＩＣ切換回路２７を周期的に切り替えると、冷陰極管に供給される高周波流の供給端を、時間的に交互に逆にすることができる。これにより、輝度ムラの発生する場所を時間的に切り替えることができる。 The terminals of the IC switching circuit 27 are expressed as 1, 2, and 3. The terminal 3 is a common terminal connected to the AC signal supply end of the predetermined frequency f1, the terminal 1 is connected to the clock pulse circuit 23a, and the terminal 2 is connected to the clock pulse circuit 33a.
In the circuit of FIG. 5, the high frequency power supply end 25 a is connected to one end of the cold cathode tube 15 while the IC switching circuit 27 is connected to the terminal 1 side. Since no voltage is applied to the other end of the cold-cathode tube 15 (insulated by the secondary coil of the main transformer 34), the high-frequency current flows from one end of the cold-cathode tube 15 to the support plate 14. During the period when the IC switching circuit 27 is connected to the terminal 2 side, the high-frequency current flows from the other end of the cold cathode tube 15 to the support plate 14. When the IC switching circuit 27 is periodically switched, the supply end of the high-frequency flow supplied to the cold cathode tube can be alternately reversed in time. Thereby, the place where the brightness unevenness occurs can be switched over time.

このＩＣ切換回路２７の切替えの周波数は、０Ｈｚを超え周波数ｆ１未満であれば、いかなる周波数でもよい。特に前記ＩＣ切換回路２７の切り替え周期が目の残像時間（約０．３秒）よりも短くなるような周波数に設定することが輝度ムラを感じないようにするために好ましい。さらに好ましくは、切替えの周波数を１００Ｈｚ以上にすると、チラツキを感じなくなるので好ましい。また、あまり高い周波数で切り替えても、チラツキを感じなくなる効果は同じなので、３００Ｈｚ程度が好ましい上限と考えられる。   The switching frequency of the IC switching circuit 27 may be any frequency as long as it exceeds 0 Hz and is less than the frequency f1. In particular, it is preferable to set the frequency so that the switching cycle of the IC switching circuit 27 is shorter than the afterimage time (about 0.3 seconds) of the eyes so as not to cause uneven brightness. More preferably, the switching frequency is set to 100 Hz or more because flickering is not felt. Moreover, even if the frequency is switched at a very high frequency, the effect of not feeling flickering is the same, so about 300 Hz is considered a preferable upper limit.

図６は、スイッチング回路２３のクロックパルス回路２３ａの信号入力端子ＣＰに印加される交流信号と、スイッチング回路３３のクロックパルス回路３３ａの信号入力端子ＣＰに印加される交流信号との周波数を変える回路例を示す。
スイッチング回路２３の交流信号の周波数をｆ１、スイッチング回路３３の交流信号の周波数をｆ２と表記する。周波数ｆ１，ｆ２ともに、数十ｋＨｚ〜数百ｋＨｚの範囲の中から選ばれることが好ましい。 FIG. 6 shows a circuit for changing the frequency of the AC signal applied to the signal input terminal CP of the clock pulse circuit 23a of the switching circuit 23 and the AC signal applied to the signal input terminal CP of the clock pulse circuit 33a of the switching circuit 33. An example is shown.
The frequency of the AC signal of the switching circuit 23 is denoted by f1, and the frequency of the AC signal of the switching circuit 33 is denoted by f2. Both the frequencies f1 and f2 are preferably selected from the range of several tens of kHz to several hundreds of kHz.

この図６の回路では、高周波電源供給端２５ａから供給される電流の周波数ｆ１と、高周波電源供給端２５ｂから供給される電流の周波数ｆ２とが異なるため、両電流に位相差が発生する。その位相差は時間的に変化していく。すなわち、位相は０度〜３６０度の間を時計のように回転していく。
そのため、或る瞬間をとれば、冷陰極管１５の両端には同位相の電流が供給される。そのため前述した（１）のように、均流点灯は最も容易、中央部暗くなるという状態が発生する。他の瞬間では、冷陰極管１５の両端には逆位相の電流が供給される。そのため前述した（２）のように、均流点灯が難しくなるが、管内での明るさの分布は最も均等という状態が発生する。さらに他の瞬間では前述した（３）のように、均流点灯容易で、中央部も暗くならないという中間の状態が発生する。 In the circuit of FIG. 6, since the frequency f1 of the current supplied from the high frequency power supply end 25a is different from the frequency f2 of the current supplied from the high frequency power supply end 25b, a phase difference occurs between the two currents. The phase difference changes with time. That is, the phase rotates like a clock between 0 degrees and 360 degrees.
Therefore, if a certain moment is taken, currents in the same phase are supplied to both ends of the cold cathode tube 15. For this reason, as described in (1) above, the uniform current lighting is the easiest and the state where the central part becomes dark occurs. At other moments, opposite phase currents are supplied to both ends of the cold cathode tube 15. For this reason, as described in (2) above, uniform current lighting becomes difficult, but the brightness distribution in the tube is most uniform. At another moment, as described in (3) above, an intermediate state occurs in which uniform current lighting is easy and the central portion is not darkened.

したがって、特に均流素子を必要としなくても放電管の起動が容易にでき、起動後、放電管に流れる電流の不均等化を防止し、各放電管の明るさを均等にすることができるという、本発明の効果が得られる。
前記２つの周波数ｆ１，ｆ２の差｜ｆ１−ｆ２｜は、２０ｋＨｚ以上、２００ｋＨｚ以下の範囲にあることが好ましい。２０ｋＨｚ未満であれば、変圧器のサイズが大きくなるとともに、うなり音が聞こえるという不具合があり、２００ｋＨｚを超えると漏れ電流（無効電流）が多く流れ、効率が落ちる、また明るさも不均等になるという不具合がある。 Therefore, the discharge tube can be easily started even if no current-equalizing element is required, and non-uniformity of the current flowing through the discharge tube can be prevented after the start, and the brightness of each discharge tube can be made uniform. The effect of the present invention is obtained.
The difference | f1-f2 | between the two frequencies f1 and f2 is preferably in the range of 20 kHz to 200 kHz. If it is less than 20 kHz, there is a problem that the size of the transformer increases and a roaring sound can be heard, and if it exceeds 200 kHz, a large amount of leakage current (reactive current) flows, efficiency decreases, and brightness also becomes uneven. There is a bug.

次に図７は、冷陰極管１５１〜１５ｎの好ましい配線状態を説明するための回路図である。複数の冷陰極管１５１〜１５ｎのうち、左から数えて奇数本目の冷陰極管１５では、高周波電源供給端２５ａが、当該冷陰極管１５の一端（紙面上側の端）に接続され、高周波電源供給端２５ｂが、当該冷陰極管１５の他端（紙面下側の端）に接続されている。また、奇数本目の冷陰極管１５の他端と、偶数本目の冷陰極管１５の一端は相互に接続され、奇数本目の冷陰極管１５の一端と、偶数本目の冷陰極管１５の他端は相互に接続されている。   Next, FIG. 7 is a circuit diagram for explaining a preferable wiring state of the cold cathode fluorescent lamps 151 to 15n. Of the plurality of cold-cathode tubes 151 to 15n, in the odd-numbered cold-cathode tube 15 counted from the left, the high-frequency power supply end 25a is connected to one end of the cold-cathode tube 15 (the upper end on the paper surface). The supply end 25b is connected to the other end of the cold cathode tube 15 (the lower end on the paper surface). Further, the other end of the odd-numbered cold cathode tube 15 and one end of the even-numbered cold cathode tube 15 are connected to each other, and one end of the odd-numbered cold cathode tube 15 and the other end of the even-numbered cold cathode tube 15 Are connected to each other.

この配線構造を採用すれば、奇数本目の冷陰極管１５の他端に近い部分がやや暗くなっても、偶数本目の冷陰極管１５の他端に近い部分は高周波電源供給端２５ａから電流が流れ込むので明るい。また偶数本目の冷陰極管１５の他端に近い部分がやや暗くなっても、奇数本目の冷陰極管１５の他端に近い部分は高周波電源供給端２５ｂから電流が流れ込むので明るい。よって、冷陰極管１５を全体としてみれば、明るい部分と暗い部分が交互に配置されることにより、明るさの分布を一様にすることができる。   If this wiring structure is adopted, even if the portion near the other end of the odd-numbered cold cathode tube 15 becomes slightly dark, the portion near the other end of the even-numbered cold cathode tube 15 receives current from the high-frequency power supply end 25a. Bright because it flows. Even if the portion near the other end of the even-numbered cold-cathode tube 15 becomes slightly dark, the portion near the other end of the odd-numbered cold-cathode tube 15 is bright because current flows from the high-frequency power supply end 25b. Therefore, when the cold cathode tube 15 is viewed as a whole, the brightness distribution can be made uniform by alternately arranging the bright portions and the dark portions.

なお、図７の例では、奇数本目の冷陰極管１５と、偶数本目の冷陰極管１５とで高周波駆動電源の極性が反対になるようにしているが、本発明は奇数・偶数に限定されるものではない。ｎ本の冷陰極管１５を、隣り合うＭ本ずつのグループまとめて、まとめられたグループの中で高周波駆動電源の極性が同一になるようにし、隣り合うグループでは、高周波駆動電源の極性が反対になるようにしてもよい。前記グループ内の本数Ｍは、２以上ｎ／２以下の自然数とすることが好ましい。   In the example of FIG. 7, the odd-numbered cold-cathode tubes 15 and the even-numbered cold-cathode tubes 15 have opposite polarities of the high-frequency drive power supply. However, the present invention is limited to odd-numbered and even-numbered cold-cathode tubes. It is not something. The n cold cathode tubes 15 are grouped in groups of M adjacent to each other so that the polarities of the high frequency driving power supply are the same in the group, and the polarities of the high frequency driving power supply are opposite in the adjacent groups. It may be made to become. The number M in the group is preferably a natural number of 2 or more and n / 2 or less.

いままで本発明の実施の形態を説明したが、本発明は、実施の形態に限られるものでないことはもちろんである。例えば本発明は、実施の形態で用いた冷陰極管に限られず、放電管一般に適用できるものである。   Although the embodiments of the present invention have been described so far, the present invention is of course not limited to the embodiments. For example, the present invention is not limited to the cold cathode tubes used in the embodiments, and can be applied to general discharge tubes.

本発明の放電管均流点灯駆動装置が適用される液晶表示装置１０を示す分解斜視図である。It is a disassembled perspective view which shows the liquid crystal display device 10 with which the discharge tube equality lighting drive device of this invention is applied. インバータ回路２０，３０及びそれに接続される複数の冷陰極管１５を含む均流点灯駆動装置の全体回路図である。1 is an overall circuit diagram of a uniform current lighting driving device including inverter circuits 20 and 30 and a plurality of cold cathode tubes 15 connected thereto. FIG. 高周波電源供給端２５ａ，２５ｂの電圧波形を対比して示すグラフである。It is a graph which compares and shows the voltage waveform of high frequency power supply terminal 25a, 25b. 高周波電源供給端２５ａを、複数の冷陰極管１５１〜１５ｎの一端に直接接続するとともに、高周波電源供給端２５ｂを、進相素子又は遅相素子を介して冷陰極管１５１〜１５ｎの他端に接続した回路図である。The high frequency power supply end 25a is directly connected to one end of a plurality of cold cathode tubes 151 to 15n, and the high frequency power supply end 25b is connected to the other end of the cold cathode tubes 151 to 15n via a phase advance element or a slow phase element. It is the circuit diagram which connected. インバータ回路２０の高周波駆動電源と、インバータ回路３０の高周波駆動電源とが、交互にスイッチングされて高周波電源供給端２５ａ，２５ｂに供給される均流点灯駆動装置の全体回路図である。FIG. 3 is an overall circuit diagram of a uniform current lighting driving device in which a high-frequency driving power source of an inverter circuit 20 and a high-frequency driving power source of an inverter circuit 30 are alternately switched and supplied to high-frequency power supply terminals 25a and 25b. 高低２つの周波数の各インバータ回路２０，３０を用いて複数の冷陰極管１５を点灯する均流点灯駆動装置を示す回路図である。It is a circuit diagram showing a uniform current lighting driving device for lighting a plurality of cold cathode fluorescent lamps 15 using inverter circuits 20 and 30 of two frequencies, high and low. 冷陰極管１５１〜１５ｎの好ましい配線例を説明するための回路図であるIt is a circuit diagram for demonstrating the preferable wiring example of the cold cathode tubes 151-15n バラスト・キャパシタを利用した従来の放電管均流点灯駆動装置の一例を示す回路図である。It is a circuit diagram which shows an example of the conventional discharge tube equality lighting drive device using a ballast capacitor. 各放電管の一端又は両端を支持する基板上にキャパシタを、当該基板と一体に形成した例を示す斜視図である。It is a perspective view which shows the example which formed the capacitor integrally with the said board | substrate on the board | substrate which supports the one end or both ends of each discharge tube.

符号の説明Explanation of symbols

１０ 液晶表示装置
１１ 液晶表示部
１２ 液晶パネル
１３ 均流点灯駆動装置本体
１４ 支持板
１５，１５１〜１５ｎ 冷陰極管
１６ 給電基板
２０，３０ インバータ回路
２３，３３ スイッチング回路
２３ａ，３３ａ クロックパルス回路
２４，３４ 主変圧器
２５ａ，２５ｂ 高周波電源供給端
２７ ＩＣ切換回路
２８ 進相素子又は遅相素子 DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 11 Liquid crystal display part 12 Liquid crystal panel 13 Current equalization lighting drive apparatus main body 14 Support plate 15,151-15n Cold cathode tube 16 Power supply board | substrates 20 and 30 Inverter circuits 23 and 33 Switching circuits 23a and 33a Clock pulse circuit 24, 34 Main transformer 25a, 25b High frequency power supply terminal 27 IC switching circuit 28 Phase advance element or phase lag element

Claims (6)

互いに並列に接続された複数の放電管を点灯駆動するための放電管均流点灯駆動装置であって、
前記複数の放電管を支持し、前記複数の放電管との間に浮遊容量が形成されている支持部材と、高周波駆動電源を供給する第一のインバータ回路と、高周波駆動電源を供給する第二のインバータ回路とを備え、
前記第一のインバータ回路の高周波駆動電源の出力端から供給される高周波電流は、前記複数の放電管の一端から、前記浮遊容量を介して、前記支持部材に到達し、前記第一のインバータ回路の高周波駆動電源の接地端に還流し、
前記第二のインバータ回路の高周波駆動電源の出力端から供給される高周波電流は、前記複数の放電管の他端から、前記浮遊容量を介して、前記支持部材に到達し、前記第二のインバータ回路の高周波駆動電源の接地端に還流することを特徴とする放電管均流点灯駆動装置。 A discharge tube equalizing lighting driving device for driving and driving a plurality of discharge tubes connected in parallel with each other,
A support member that supports the plurality of discharge tubes and has a stray capacitance formed between the plurality of discharge tubes, a first inverter circuit that supplies high-frequency drive power, and a second that supplies high-frequency drive power Inverter circuit and
The high-frequency current supplied from the output end of the high-frequency drive power source of the first inverter circuit reaches the support member from one end of the plurality of discharge tubes via the stray capacitance, and the first inverter circuit Return to the ground terminal of the high-frequency drive power supply
The high-frequency current supplied from the output end of the high-frequency drive power supply of the second inverter circuit reaches the support member from the other end of the plurality of discharge tubes via the stray capacitance, and the second inverter A discharge tube equalizing lighting driving device characterized by recirculating to a ground terminal of a high frequency driving power source of a circuit. 前記第一のインバータ回路の高周波駆動電源に対して、前記第二のインバータ回路の高周波駆動電源の位相が所定角度ずれている請求項１記載の放電管均流点灯駆動装置。   2. The discharge tube equalizing lighting driving device according to claim 1, wherein a phase of the high-frequency driving power source of the second inverter circuit is shifted by a predetermined angle with respect to the high-frequency driving power source of the first inverter circuit. 所定角度が０度を超え１８０度未満の任意の角度、又は１８０度を超え３６０度未満の任意の角度である請求項２記載の放電管均流点灯駆動装置。   3. The discharge tube uniform lighting driving device according to claim 2, wherein the predetermined angle is an arbitrary angle greater than 0 degree and less than 180 degrees, or an arbitrary angle greater than 180 degrees and less than 360 degrees. 前記第一のインバータ回路の高周波駆動電源と、前記第二のインバータ回路の高周波駆動電源とが、交互に切換えられて供給される請求項１記載の放電管均流点灯駆動装置。   2. The discharge tube equalizing lighting driving device according to claim 1, wherein the high-frequency driving power of the first inverter circuit and the high-frequency driving power of the second inverter circuit are alternately switched and supplied. 前記第一のインバータ回路の高周波駆動電源に対して、前記第二のインバータ回路の高周波駆動電源の周波数が異なっている請求項１記載の放電管均流点灯駆動装置。   2. The discharge tube equalizing lighting driving device according to claim 1, wherein a frequency of the high-frequency driving power source of the second inverter circuit is different from a high-frequency driving power source of the first inverter circuit. 前記放電管は、蛍光灯又は冷陰極管である請求項１ないし請求項５のいずれか１項に記載の放電管均流点灯駆動装置。   The discharge tube uniform current lighting driving device according to any one of claims 1 to 5, wherein the discharge tube is a fluorescent lamp or a cold cathode tube.
JP2008092589A 2008-03-31 2008-03-31 Discharge tube uniform-flow lighting and driving device Pending JP2009245838A (en)

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