1267323 (1) 玖、發明說明 【發明所屬之技術領域】 本發明是屬於一種冷陰極管（CCFL : Cold Cathode Fluorescent Lamp)等的放電燈點燈裝置，特別是具有調 整放電燈亮度的調光控制電路，且在短時間內以任意亮度 可點亮放電燈的放電燈點燈裝置。 【先前技術】 · 眾知被使用在液晶電視，及裝載於筆記型個人電腦等 的液晶顯示裝置的背面照明等的冷陰極管等的放電燈點燈 裝置。例如表示於第5圖的習知放電燈點燈裝置是具備： 發生十數伏特的直流電壓VIN的直流電源1，及將直流電 源1的直流電壓VIN變換成數百伏特至千數百伏特的交流 電壓VL的交流變換電路2，及作爲連接於交流變換電路2 的輸出端子的放電管的冷陰極管3，及輸出冷陰極管3的 調光信號VB的調光信號發生電路4，及檢測流在冷陰極 鲁 管3的管電流IL的管電流檢測電路5，及將管電流檢測電 路5的檢測電流値成爲事先設定的電流値般地，將控制交 流變換電路2的交流電壓Vl的電流控制信號VA予以輸出 的管電流控制電路6，及具有藉由調光信號發生電路4的 調光信號V b連續地或斷續地輸出的閘極手段7 1的調光控 制電路7，及從調光控制電路7的輸出信號VD形成驅動 交流變換電路2的驅動信號VG的驅動電路8。 如第6圖所示，交流變換電路2是具有：被連接於直 -4- (2) 1267323 流電源1的矩形波電壓發生電路2 1，及包括被連接於矩 形波電壓發生電路21，且與一次繞組22a串聯地形成的 洩漏電感22c的洩漏變壓器22，及被連接於洩漏變壓器 22的二次繞組22b的諧振電容器23。洩漏變壓器22及諧 振電容器23是構成串聯諧振電路24。在此，分別將洩漏 變壓器22的一次繞組22a及二次繞組22b的匝數作爲N ，N2〔匝〕，則洩漏變壓器22的匝比N2/ N，是被設定 在約1 00。省略詳圖，惟矩形波電壓發生電路2 1是具有 :例如橋接複數交換元件所構成且利用各交換元件的交換 動作將來自直流電源1的直流電壓VIN變換成矩形波交流 電壓的交換電路，及在一次側繞組連接有交換電路且從二 次側繞組發生被電壓調整的矩形波交流電壓Vs的輸出變 壓器。利用從驅動電路8所輸入的驅動信號VG，以數十 KHz左右的頻率導通，斷開動作構成上述交換電路的各交 換元件，俾將從直流電源1所輸入的直流電壓VlN變換成 矩形波交流電壓Vs。從矩形波電壓發生電路2 1所輸出的 矩形波交流電壓V s，是利用洩漏變壓器2 2及諧振電容器 23所構成的串聯諧振電路24變換成高壓（數百伏特至千 數百伏特）且數十KHz左右頻率的正弦波交流電壓Vl， 而被供給於冷陰極管3。調光信號發生電路4是發生比交 流變換電路2的交換頻率（數十KHz左右）充分更低的 一定頻率（數十Hz至數KHz)的矩形脈衝信號，按照冷 陰極管3的所期望亮度而利用變更矩形脈衝信號的即時作 用。輸出冷陰極管3的調光信號vB。因此，冷陰極管3 -5- (3) 1267323 的最大時是輸出即時作用100%的矩形脈衝信號， 第7 ( a )圖所示地，輸出正電壓位準一定的調光f! 〇 管電流檢測電路5是具有：與冷陰極管3串聯 的管電流檢測用電阻5 1，及陽極端子連接於冷陰 與管電流檢測用電阻5 1的連接點的整流二極體52 連接於整流二極體52的陰極端子與接地端子之間 電容器5 3。亦即，管電流檢測電路5是利用管電 用電阻5 1將流在冷陰極管3的管電流IL變換成對 管電流的電壓，並將管電流檢測用電阻51的兩端 電壓藉，由整流二極體52及平流電容器53加以整 流化而將該直流電壓輸出作爲檢測電壓VF。管電 電路6是具有：發生規定流在冷陰極管3的管電孩 設定値的基準電壓VR1的基準電源61，及輸出經 電流檢測電路5的檢測電壓VF與基準電源6 1的基 VR1的誤差電壓的輸出電壓VE1的誤差放大器62， 一定頻率（數十KHz左右）的三角波電壓VT的三 盪電路63，及利用比較誤差放大器62的輸出電壓 三角波振盪電路63的三角波電壓VT而發生即時作 的矩形脈衝列的電流控制信號VA的PWM比較器 光控制電路7的閘極手段7 1是可用輸出如調光信 電路4的調光信號VB與管流控制電路6的電流控 VA的邏輯積信號VD的AND閘極71所構成。亦即 控制電路是如第7圖所示地，從調光信號發生電路 亦即如 Ϊ號VB 地連接 極管3 ，及被 的平流 流檢測 應於該 子間的 流及平 流控制 ΐ II的 放大管 準電壓 及發生 角波振 VE1的 用變更 6 4 〇調 號發生 制信號 ，調光 r 4輸 -6 - (4) 1267323 入正電壓位準一定的調光信號Vb時，因連續地輸出來自 管電流控制電路6的電流控制信號vA，因此未進行調整 冷陰極管3的亮度，亦即未進行調光動作。另一方面，如 第8 ( A )圖所示地當以比從管電流控制電路6所輸出的 電流控制信號VA的頻率（數十KHz左右）還要更低低的 頻率（數十Hz至數KHz )，且具有對應於冷陰極管3的 所期望的亮度的作用比的矩形脈衝到的調光信號VB從調 光信號發生電路4輸入至調光控制電路7時，則以調光 信號V B的週期斷續性地輸出來自管電流控制電路6的電 流控制信號V a，而進行冷陰極管3的調光動作。驅動電 路8是從調光控制電路7的AND閘極7 1所輸入的邏輯積 信號VD形成連續地或斷續地驅動交流變換電路2內的矩 形波電壓發生電路21的交流變換電路2內的矩形波電壓 發生電路21的驅動信號VG，而輸出至矩形波電壓發生電 路21。 在表示於第5圖的構成中，如第7(A)圖所示地裝 置起動時U使調光信號發生電路4的調光信號VB在正電 壓位準一定之際，調光控制電路7是未進行調光動作，利 用從管電流控制電路6連續地輸出的電流控制信號VA， 而從驅動電路8的輸出連續地驅動交流變換電路2的驅動 信號V G。由此，如第7 ( B )圖所示地從交流變換電路2 連續地施加交流電壓Vl於冷陰極管3 ’而如第7 ( C )圖 所示地，在時刻h管電流U開始流在冷陰極管3 ’則冷 陰極管U保持在大約一定之故’因而冷陰極管3的亮度 (5) 1267323 經常地最大値成爲一定。 又，如第8 ( A )圖所示地，以比管電流控制電路6 的電流控制信號VA的頻率還要更低低的頻率，且具有對 應於冷陰極管3的所期望的亮度的作用比的矩形脈衝列的 調光信號V B從調光信號發生電路4輸出時，則從調光控 制電路7輸出管電流控制電路6的電流控制信號VA作成 斷續的輸出信號VB。由此，從驅動電路8輸出以調光信 號VB的週期斷續地驅動交流變換電路2的驅動信號Vg， 如第8 ( B )圖所示地從交流變換電路2斷續地施加交流 電壓VL於冷陰極管3。如第8(C)圖所示地，在時刻t2 管電流I l開始流在冷陰極管3時，則冷陰極管3開始點 壳，時刻12以後，管電流I l斷續地流在冷陰極管3。由 此，冷陰極管3以調光信號VB的週期重複點滅之故，因 而適當地調整調光信號V b的即時作用就可得到所期望的 亮度。與此同時地，利用管電流控制電路6使得流在冷陰 極管3的管電流U保持大約一定之故，因而冷陰極管3 的亮度經常地成爲一定。具有類似於上述的放電燈點燈裝 置的構成的放電燈點燈裝置，是被揭示在日本特開2000-357599號公報（第6頁，第6圖）。 在表示於第5圖的習知放電燈點燈裝置中，如第8 ( A )圖所示地調光信號V b從調光信號發生電路4事先輸 入於調光控制電路7時，如第8 ( C )圖所示地在冷陰極 管3的管電流IL未被檢測的期間TB之間，如第8 ( B )圖 所示地，交流變換電路2的交流電壓VL也斷續地施加冷 -8 - (6) 1267323 陰極管3。所以在管電流IL未被檢測的黑暗起期間TB中 ，無法將點亮冷陰極管3所必需充分的激磁能從交流變換 電路2供給於冷陰極管3，而從裝置起動時t i 一直到冷陰 極管3的開始點燈時t2的時間TB與將交流變換電路2的 交流變換電路2的交流電壓VL連續地施加於冷陰極管3 時〔第7 ( B )圖〕的相同時間TA相比較有變久的缺點。 因此，在長時間未點亮冷陰極管3而置放在冷暗處時有發 生起動不良等的不方便。 φ 如此本發明的目的是在於提供一種在短時間以任意亮 度可點亮放電燈的放電燈點燈裝置。 【發明內容】 依本發明的放電燈點燈裝置是具有：直流電源1，及 具有至少包括一個交換元件的交換電路，且利用該交換電 路的交換動作，將從直流電源所供給的直流電力變換成交 流電力的交流變換電路2，及連接於該交流變換電路2的 φ 輸出端子的放電管3，及利用從調光信號發生電路4所輸 出的調光信號，斷續地發生交流變換電路2的交流輸出而 調整放電管3的亮度的調光控制電路7。該放電燈點燈裝 置是具備：檢測流在放電管3的管電流IL的管電流檢測 電路5，及連接於管電流檢測電路5的調光轉換電路9。 調光轉換電路9是轉換成從調光信號發生電路4將調光信 號VB有效地供給於調光控制電路7的導通狀態，而斷續 地發生交流變換電路2的交流輸出之同時，轉換成將從調 (7) 1267323 光信號發生電路4供給於調光控制電路7的調光信號VB 作成無效的無效狀態，而連續地發生交流變換電路2的交 流輸出的轉換機構95，及在投入電源時發生起動信號的 起動信號發生機構93，及轉換成在起動信號發生機構93 發生起動信號時，將轉換機構95作成無效狀態的取消狀 態，及管電流檢測電路5的檢測電流値在基準値以上時， 將轉換機構95作成導通狀態的容許狀態的狀態轉換手段 96。在管電流IL幾乎不會流在放電管3的起動時，利用 調光轉換電路9將從調光信號發生電路4賦於調光控制電 路7的調光信號VB作成無效之故，因而交流變換電路2 的交流輸出Vl連續地供給於放電管3。由此，起動時所 需的充分激磁能量快速地供給於放電管3，而在短時間內 以任意亮度可點亮放電管3。 【實施方式】 以下，參照第1圖至第4圖說明依本發明的放電燈點 燈裝置的實施形態。在第1圖至第4圖中與表示於第5圖 至第8圖的部位實質上相同部分賦於同一記號，而省略其 說明。 如第1圖所示地，本實施形態的放電燈點燈裝置，是 管電流檢測電路5在未檢測到冷陰極管3的管電流IL的 期間Tc (第3圖），將從調光信號發生電路4賦於調光 控制電路7的調光信號VB作成無效而從交流變換電路2 連續地發生交流電壓VL，在管電流檢測電路5檢測到冷 -10- (8) 1267323 陰極管3的管電流IL時將驅動調光控制電路7的調光轉 換電路9連接於管電流檢測電路5之處與表示於第5圖的 習知放電燈點燈裝置不相同。 如第2圖所示地，調光轉換電路9是具備··在導通未 圖示的電源開關時，作爲發生單發脈衝的起動信號Vp的 起動信號發生機構的單發脈衝發生器93，及構成在調光 控制電路7的AND閘極7 1的輸入端子連接有輸出端子， 而在另一方的輸入端子連接有調光信號發生電路4的轉換 機構的OR閘極95，及作爲具有在〇R閘極95的另一方 輸入端子連接有輸出端子且連接於單發脈衝發生器93的 復置端子的狀態保持機構的R - S正反器94，及作爲在R 一 S正反器94的設定端子賦於輸出的比較機構的比較器 92，及發生規定流在冷陰極管3的管電流IL的檢測最小 値的基準電壓VR2的基準電源9 1。基準電源9 1，比較器 92及R— S正反器94是構成被連接於管電流檢測電路5 與調光控制電路7之間的狀態轉換機構96。狀態轉換機 構96是轉換成在單發脈衝發生器93發生起動信號時，將 OR閘極95作成無效狀態的取消狀態，及在管電流檢測電 路5的檢測電流値爲基準値以上時，將〇R閘極95作成 導通狀態的容許狀態。 〇 R閘極9 5是被轉換成導通狀態與無效狀態’當R -S正反器94成爲容許狀態時，則〇R閘極95被轉換成導 通狀態，而將調光信號VB從調光信號發生電路4有效地 供給於調光控制電路7，俾斷續地發生交流變換電路2的 -11 - 1267323 Ο) 交流輸出。又，當R — S正反器94成爲取消狀態時，則 OR閘極9 5被轉換成無效狀態，而將從調光信號發生電路 4供給於調光控制電路7的調光信號VB作成無效，俾連 續地發生交流變換電路2的交流輸出。 比較器92是在管電流檢測電路5的檢測電壓VF比基 準電源91的基準電壓VR2還低時發生低電壓L位準的非 開動信號VE2，而在管電流檢測電路5的檢測電壓Vf爲 基準電源91的基準電壓VR2以上時，發生高電壓Η位準 的開動信號VE2。R— S正反器94是在起動信號VP從單 發脈衝發生器93輸入至復置端子R時成爲復置狀態（取 消狀態），而在發生比較器92的輸出信號VE2爲低電壓 L位準的非開動信號的期間是保持復置狀態（取消狀態） 之故，因而OR閘極95是成爲無效狀態。又，R- S正成 器94是管電流檢測電路5的檢測電壓VF變成比基準電源 91的基準電壓VR2還高，而在比較器92將高電壓Η位準 的開動信號VE2發生在設定端子S時被轉換成設定狀態（ 容許狀態）。所以，OR閘極95是成爲導通狀態，而輸出 R— S正反器94的換向輸出信號Vq與調光信號發生電路 4的調光信號VB的邏輯和信號Vc。 調光轉換電路9的基準電源91的基準電壓VR2，是 被設定成比管電流控制電路6的基準電源6 1的基準電壓 V R i還低的數値。又，調光控制電路7的AND閘極71是 輸出從調光轉換電路9所輸出的邏輯和信號V。與從管電 流控制電路6所輸出的電流控制信號Va的邏輯信號VD。 -12- (10) 1267323 其他構成是與表示於第6圖的習知放電燈點燈裝置大約同 樣。 在上述構成中，在時刻tl (第3圖）導通未圖示的電 源開關而投入電源，則單發脈衝的起動信號VP從調光轉 換電路9內的單發脈衝發生器93輸出，而輸入至r— S 正反器94的復置端子R，使得R—S正反器91成爲復置 狀態，亦即成爲取消狀態。與此同時地，如第3 ( A )圖 所示地，以比管電流控制電路的電流控制信號VA的頻率 (數十至數百KHz )還要更低低的頻率（數十Hz左右） ，且具有對應於冷陰極管3的所期望的亮度的作用比的矩 形脈衝列的調光信號VB從調光信號發生電路4被輸出， 而被輸入至調光轉換電路9內的OR閘極95。如第3‘（ D )圖所示地，從投入電源時ti 一直到開始點亮時t2爲止 的黑暗起動期間Te中是管電流IL幾乎不流動在冷陰極管 3，而管電流檢測電路5的檢測電壓V F比調光轉換電路9 內的基準電源91的基準電壓VR2還低之故，因而從比較 器92輸出低電壓L位準的輸出信號VE2。所以，從復置 狀態（取消狀態）的R- S正反器94的換向輸出端子輸 出高電壓Η位準的換向輸出信號Vq，而被輸入至〇R閘 極95。由此，如第3(B)圖所示地，正電壓位準一定的 邏輯和信號V。從位於無效狀態的〇R閘極95賦於調光控 制電路7的AND閘極71之故，因而來自調光信號發生電 路4的調光信號VB是成爲無效，調光控制電路7是不進 行冷陰極管3的調光動作。因此，從管電流控制電路6連 -13- (11) 1267323 續地輸入至調光控制電路7的AND閘極7 1的電流控制信 號VA作爲邏輯積信號Vd而從調光控制電路7被輸出’ 俾使驅動信號V〇從驅動電路8連續地賦於交流變換電路 2內的矩形波電壓發生電路21，由此，交流變換電路2內 的矩形波電壓發生電路2 1連續地被驅動，經由串聯諧振 電路24如第3 ( C )圖所示地高壓的正弦波交流電壓 連續地供給於冷陰極管3。 在時刻t2中，如第3 ( D )圖所示地，管電流IL開始 流動而使冷陰極管3開始點亮，當管電流檢測電路5的檢 測電壓VF成爲調光轉換電路9內的基準電源91的基準 電壓VR2以上，則高電壓Η位準的輸出信號VE2從比較器 92被輸出，而被輸入至R—S正反器94的設定端子S使 得R - S正反器94成爲設定狀態，亦即成爲容許狀態。 這時候，低電壓L位準的換向輸出信號Vq從R — S正反 器94的換向輸出端子被輸出之故，因而OR閘極95是被 轉換成導通狀態，如第3 ( B )圖所示地時刻t2以後，表 示於第3(A)圖的調光信號發生電路4的調光信號VB從 OR閘極95輸出作爲邏輯和信號Vc，而賦於調光控制電 路7的AND閘極71。所以，以調光信號發生電路4的調 光信號VB的週期斷續的管電流控制電路6的電流控制信 號VA從調光控制電路7的AND閘極71輸出作爲邏輯積 信號VP，使得驅動信號VG從驅動電路8斷續地賦於交流 變換電路2內的矩形波電壓發生電路21。由此’交流變 換電路2內的矩形波電壓發生電路2 1以調光信號VB的週 -14- (12) 1267323 期斷續地被驅動，經由串聯諧振電路24，如第3 ( C )圖 所示地高電壓的正弦波交流電壓VL以調光信號VB的週期 斷續地供給於冷陰極管3。因此，冷陰極管3的開始點亮 時t2以後，如第3 ( D )圖所不地管電流IL斷續地繼續流 在冷陰極管3，使得冷陰極管3以調光信號Vb的週期進 行重複點燈冷陰極管3的調光動作。與此同時地，利用管 電流控制電路6使流在冷陰極管3的管電流IL保持大約 一定之故，因而冷陰極管3的亮度經常地成爲一定。 修 在本實施形態中，管電流I l幾乎未流在冷陰極管3 的起動時，亦即黑暗起動期間T。中，利用調光轉換電路 9從調光信號發生電路4賦於調光控制電路7的調光信號 VB成爲無效之故，因而未進行依調光控制電路7的冷陰 極管3的調光動作。由此，交流變換電路2的交流電壓 VL連續地且快速地供給於冷陰極管3之故，因而可將爲 了點亮所需的充分激磁能量快速地供給於冷陰極管3。又 ，開始點亮冷陰極管3之後，來自調光信號發生電路4的 φ 調光信號VB賦於調光控制電路7，進行依調光控制電路7 的冷陰極管3的調光動作之故，因而以任意亮度可點亮冷 陰極管3。因此，在短時間以任意亮度可點亮冷陰極管3 。實際上，將從調光信號發生電路4所輸出的調光信號 VB的通態作用設定50%時，可將從裝置起動時q —直到 冷陰極管3的開始點亮時t2爲止的時間Tc縮短成表示於 第5圖及第6圖的習知放電燈點燈裝置時的相同時間TB 的大約一半。 -15- (13) 1267323 第4圖是表示使用具有按照從誤差放大器62所輸出 的誤差電壓Ve i的位準，而發生矩形脈衝列的斷開期間有 變化的導通寬度固定的電流控制信號VA的電壓一頻率變 換電路（在圖中表示爲V/ F變頻器）65的脈衝頻率調變 方式的管電流控制電路6的變更實施形態。 本發明的實施形態是並不被限定於上述實施形態，可 做各種變更。例如在上述實施形態中，以矩形波電壓發生 電路21及洩漏變壓器22與諧振電容器23所形成的串聯 諧振電路24來構成交流變換電路2，惟代替洩漏變壓器 22而使用單繞組的線圈，將矩形波電壓發生電路2 1內的 輸出變壓器的匝數比設定在1〇〇左右而構成交流變換電路 2也可以。又，在上述實施形態中，以管電流檢測用電阻 51與整流二極體5 2及平流電容器5 3構成管電流檢測電 路5，惟使用包含運算放大器等的管電流檢測電路（電流 -電壓變換電路）也可以。又，在上述實施形態按照管電 流檢測電路5的檢測電壓VF的位準，而使用輸出通態作 用有變更的矩形脈衝列的電流控制信號VA的脈衝寬調變 (PWM )方式的管電流控制電路6，惟按照管電流檢測電 路5的檢測電壓VF的位準，而使用輸出頻率有變更的矩 形脈衝列的電流控制信號VA的脈衝頻率調變（PFM )方 式的管電流控制電路6也可以。在上述實施形態中，以 OR閘極95構成調光轉換電路9內的轉換機構，惟使用電 晶體等的交換元件及電阻等來構成轉換機構，R - S正反 器94在復置狀態時，將交換元件作爲斷開狀態，而遮斷 -16- (14) 1267323 來自調光信號發生電路4的調光信號VB之同時，將正電 壓位準一定的信號賦於調光控制電路7，而在R 一 s正反 器9 4轉換成設定狀態時，則將交換元件作成導通狀態而 將來自調光信號發生電路4的調光信號Vb賦於調光控 制電路7也可以。代替調光轉換電路9內的單發脈衝發生 器，而作成使用電阻及電容器所形成的微分電路與換流器 ’在投入電源時從微分電路將經由換流器所輸出的微分脈 衝信號賦於復置端子R的構成也可以。 產業上的利用可能性 本發明的放電燈點燈裝置，是適用於作爲裝載液晶電 視及筆記型電腦等的液晶顯示裝置背面照明等冷陰極管的 使用。特別是，放電燈的設定亮度，將通態作用的狹窄調 光信號賦於調光控制電路時將放電燈長期間未點亮而放置 在冷暗所時，本發明的效果顯著地出現。 【圖式簡單說明】 苐1圖是表示依本發明的放電燈點燈裝置的一實施形 態的電路方塊圖。 第2圖是表示第1圖的各電路方塊的內部構成的電路 圖。 第3(A)圖至第3(D)圖是表示第1圖的電路各部 的電壓及電流的波形圖。 第4圖是表示第2圖的變更實施形態的電路圖。 -17- (15) 1267323 第5圖是表示習知放電燈點燈裝置的電路方塊圖。 第6圖是表示第5圖的各電路方塊的內部構成的電路 圖。 .第7(A)圖至第7(C)圖是表示未進行調光動作時 的第5圖電路各部的電壓及電流的波形圖。 第8(A)圖至第7(C)圖是表示進行調光動作時的 第5圖的電路各部的電壓及電流的波形圖。 〔主要元件對照表〕 1 直流電源 2 交流變換電路 3 放電管（冷陰極管） 4 調光信號發生電路 5 管電流檢測電路 6 管電流控制電路 7調光控制電路 ® 8 驅動電路 9 調光轉換電路 2 1 矩形波電壓發生電路 22 洩漏變壓器 2 2 a —次繞組 2 2 b二次繞組 22c洩漏電抗 23 諧振電容器 -18- (16) (16)1267323 24 串聯諧振電路 51 管電流檢測用電阻 5 2 整流二極體 5 3 平流電容器 6 1 基準電源 62 誤差放大器 63 三角波振盪電路 7 1 AND閘極 φ 9 1 基準電源 92 比較器 93 單發脈衝發生器 94 R— S正反器 95 0R閘極 V I N直流電壓 Vl 交流電壓 V B調光信號 籲 VA 電流控制信號 II 管電流 VD 輸出信號（邏輯積信號） VG 驅動信號（邏輯積信號）1267323 (1) Technical Field of the Invention The present invention relates to a discharge lamp lighting device such as a cold cathode fluorescent lamp (CCFL), and particularly to a dimming control for adjusting the brightness of a discharge lamp. A circuit, and a discharge lamp lighting device that illuminates a discharge lamp with an arbitrary brightness in a short time. [Prior Art] A discharge lamp lighting device such as a cold cathode tube or the like which is mounted on a liquid crystal television or a back surface illumination of a liquid crystal display device such as a notebook personal computer. For example, the conventional discharge lamp lighting device shown in FIG. 5 is provided with a DC power supply 1 that generates a DC voltage VIN of ten volts, and converts the DC voltage VIN of the DC power supply 1 into hundreds of volts to hundreds of volts. An AC conversion circuit 2 for AC voltage VL, a cold cathode tube 3 as a discharge tube connected to an output terminal of the AC conversion circuit 2, and a dimming signal generation circuit 4 for outputting a dimming signal VB of the cold cathode tube 3, and detection The tube current detecting circuit 5 flowing through the tube current IL of the cold cathode tube 3 and the current 値 of the tube current detecting circuit 5 are set to a predetermined current, and the current of the alternating current voltage V1 of the alternating current converting circuit 2 is controlled. a tube current control circuit 6 for outputting the control signal VA, and a dimming control circuit 7 having a gate means 71 which is continuously or intermittently outputted by the dimming signal Vb of the dimming signal generating circuit 4, and The output signal VD of the dimming control circuit 7 forms a drive circuit 8 that drives the drive signal VG of the AC conversion circuit 2. As shown in FIG. 6, the AC conversion circuit 2 has a rectangular wave voltage generating circuit 21 connected to a straight-4-(2) 1267323 power supply 1, and includes a rectangular wave voltage generating circuit 21 connected thereto, and A leakage transformer 22 of a leakage inductance 22c formed in series with the primary winding 22a, and a resonance capacitor 23 connected to the secondary winding 22b of the leakage transformer 22. The leakage transformer 22 and the resonance capacitor 23 constitute a series resonance circuit 24. Here, when the number of turns of the primary winding 22a and the secondary winding 22b of the leakage transformer 22 is N, N2 [匝], the turns ratio N2 / N of the leakage transformer 22 is set to about 100. The rectangular wave voltage generating circuit 21 has a switching circuit that is configured by, for example, bridging a plurality of switching elements, and converts a DC voltage VIN from the DC power source 1 into a rectangular wave AC voltage by an exchange operation of each switching element, and An output transformer in which a switching circuit is connected to the primary side winding and a voltage-adjusted rectangular wave AC voltage Vs is generated from the secondary side winding. The drive signal VG input from the drive circuit 8 is turned on at a frequency of about several tens of KHz, and the switching operation constitutes each switching element of the switching circuit, and the DC voltage V1N input from the DC power supply 1 is converted into a rectangular wave AC. Voltage Vs. The rectangular wave AC voltage V s outputted from the rectangular wave voltage generating circuit 2 is converted into a high voltage (hundreds of volts to several hundreds of volts) by the series resonant circuit 24 constituted by the leakage transformer 2 2 and the resonant capacitor 23 A sinusoidal alternating current voltage V1 at a frequency of about ten kHz is supplied to the cold cathode tube 3. The dimming signal generating circuit 4 is a rectangular pulse signal having a certain frequency (tens of Hz to several KHz) which is sufficiently lower than the switching frequency (about several tens of kHz) of the alternating current converting circuit 2, according to the desired brightness of the cold cathode tube 3. And use the immediate effect of changing the rectangular pulse signal. The dimming signal vB of the cold cathode tube 3 is output. Therefore, the maximum time of the cold cathode tube 3 -5- (3) 1267323 is a rectangular pulse signal that outputs 100% of the immediate action, and as shown in Fig. 7 (a), the dimming of the positive voltage level is fixed. The current detecting circuit 5 includes a tube current detecting resistor 51 connected in series with the cold cathode tube 3, and a rectifying diode 52 having an anode terminal connected to a connection point between the cold cathode and the tube current detecting resistor 51. A capacitor 53 is connected between the cathode terminal of the pole body 52 and the ground terminal. In other words, the tube current detecting circuit 5 converts the tube current IL flowing in the cold cathode tube 3 into a voltage corresponding to the tube current by the tube electric resistance 51, and borrows the voltage across the tube current detecting resistor 51. The rectifying diode 52 and the smoothing capacitor 53 are rectified to output the DC voltage as the detection voltage VF. The battery circuit 6 is a reference power source 61 having a reference voltage VR1 at which a predetermined current flows in the tube of the cold cathode tube 3, and a detection voltage VF outputted from the current detecting circuit 5 and a base VR1 of the reference power source 6 1 . The error amplifier 62 of the output voltage VE1 of the error voltage, the three-way circuit 63 of the triangular wave voltage VT of a certain frequency (about several tens of KHz), and the triangular wave voltage VT of the output voltage triangular wave oscillation circuit 63 of the comparison error amplifier 62 are instantaneously generated. The gate comparator 7 1 of the PWM comparator light control circuit 7 of the rectangular pulse train current control signal VA is a logical product of the output control signal such as the dimming signal VB of the dimming circuit 4 and the current control VA of the tube flow control circuit 6. The AND gate 71 of the signal VD is formed. That is, the control circuit is connected to the pole tube 3 from the dimming signal generating circuit, that is, the VVB, as shown in Fig. 7, and the parallel flow detection is performed between the sub-flow and the advection control ΐ II Amplification tube quasi-voltage and occurrence of angular wave vibration VE1 change 6 4 〇 Coding generation signal, dimming r 4 output -6 - (4) 1267323 When entering a positive voltage level fixed dimming signal Vb, due to continuous Since the current control signal vA from the tube current control circuit 6 is output, the brightness of the cold cathode tube 3 is not adjusted, that is, the dimming operation is not performed. On the other hand, as shown in Fig. 8(A), the frequency is lower than the frequency (about tens of KHz) of the current control signal VA output from the tube current control circuit 6 (tens of Hz to a number of KHz), and a rectangular pulsed dimming signal VB having an action ratio corresponding to the desired brightness of the cold cathode tube 3 is input from the dimming signal generating circuit 4 to the dimming control circuit 7, and then a dimming signal The period of VB intermittently outputs the current control signal V a from the tube current control circuit 6 to perform the dimming operation of the cold cathode tube 3. The drive circuit 8 is formed in the AC conversion circuit 2 that continuously or intermittently drives the rectangular wave voltage generation circuit 21 in the AC conversion circuit 2 from the logical product signal VD input from the AND gate 71 of the dimming control circuit 7. The drive signal VG of the rectangular wave voltage generating circuit 21 is output to the rectangular wave voltage generating circuit 21. In the configuration shown in Fig. 5, when the apparatus U is activated as shown in Fig. 7(A), U adjusts the dimming signal VB of the dimming signal generating circuit 4 to a positive voltage level, and the dimming control circuit 7 The dimming operation is not performed, and the drive signal VG of the AC conversion circuit 2 is continuously driven from the output of the drive circuit 8 by the current control signal VA continuously outputted from the tube current control circuit 6. Thereby, the AC voltage V1 is continuously applied from the AC conversion circuit 2 to the cold cathode tube 3' as shown in Fig. 7(B), and as shown in Fig. 7(C), the tube current U starts to flow at the time h. In the cold cathode tube 3', the cold cathode tube U is kept at about a certain value. Thus, the brightness of the cold cathode tube 3 (5) 1267323 is often maximized. Further, as shown in Fig. 8(A), the frequency is lower than the frequency of the current control signal VA of the tube current control circuit 6, and has a function corresponding to the desired brightness of the cold cathode tube 3. When the dimming signal VB of the rectangular pulse train is output from the dimming signal generating circuit 4, the current control signal VA of the tube current control circuit 6 is output from the dimming control circuit 7 to form the intermittent output signal VB. Thereby, the drive signal Vg of the AC conversion circuit 2 is intermittently driven from the drive circuit 8 at the period of the dimming signal VB, and the AC voltage VL is intermittently applied from the AC conversion circuit 2 as shown in Fig. 8(B). In the cold cathode tube 3. As shown in Fig. 8(C), when the tube current I1 starts to flow in the cold cathode tube 3 at time t2, the cold cathode tube 3 starts to be in a shell, and after time 12, the tube current I1 intermittently flows in the cold. Cathode tube 3. As a result, the cold cathode tube 3 is repeatedly turned off at the period of the dimming signal VB, so that the desired brightness can be obtained by appropriately adjusting the instantaneous action of the dimming signal Vb. At the same time, the tube current control circuit 6 is used to keep the tube current U flowing through the cold cathode tube 3 constant, so that the brightness of the cold cathode tube 3 is often constant. A discharge lamp lighting device having a configuration similar to the above-described discharge lamp lighting device is disclosed in Japanese Laid-Open Patent Publication No. 2000-357599 (page 6, page 6). In the conventional discharge lamp lighting device shown in Fig. 5, when the dimming signal Vb is input from the dimming signal generating circuit 4 to the dimming control circuit 7 as previously shown in Fig. 8 (A), 8 (C), between the periods TB during which the tube current IL of the cold cathode tube 3 is not detected, as shown in Fig. 8(B), the alternating current voltage VL of the alternating current converting circuit 2 is also intermittently applied. Cold-8 - (6) 1267323 Cathode tube 3. Therefore, in the dark period TB during which the tube current IL is not detected, sufficient excitation energy necessary for lighting the cold cathode tube 3 cannot be supplied from the alternating current conversion circuit 2 to the cold cathode tube 3, and the ti is cooled from the start of the apparatus. The time TB at the start of lighting of the cathode tube 3 at t2 is compared with the same time TA when the alternating current voltage VL of the alternating current converting circuit 2 of the alternating current converting circuit 2 is continuously applied to the cold cathode tube 3 [Fig. 7 (B)]. There are long-term disadvantages. Therefore, when the cold cathode tube 3 is not lit for a long time and placed in a cool dark place, there is an inconvenience such as a start failure. φ Thus, an object of the present invention is to provide a discharge lamp lighting device which can illuminate a discharge lamp with an arbitrary brightness in a short time. SUMMARY OF THE INVENTION A discharge lamp lighting device according to the present invention has a DC power supply 1 and a switching circuit including at least one switching element, and uses the switching operation of the switching circuit to convert DC power supplied from a DC power source. The AC conversion circuit 2 that is an AC power, the discharge tube 3 connected to the φ output terminal of the AC conversion circuit 2, and the dimming signal output from the dimming signal generation circuit 4 intermittently generate the AC conversion circuit 2 The dimming control circuit 7 that adjusts the brightness of the discharge tube 3 by the AC output. The discharge lamp lighting device includes a tube current detecting circuit 5 that detects a tube current IL flowing through the discharge tube 3, and a dimming conversion circuit 9 connected to the tube current detecting circuit 5. The dimming conversion circuit 9 is converted into an on state in which the dimming signal VB is efficiently supplied from the dimming signal generating circuit 4 to the dimming control circuit 7, and the AC output of the AC converting circuit 2 is intermittently generated, and converted into The dimming signal VB supplied from the tune (7) 1267323 optical signal generating circuit 4 to the dimming control circuit 7 is made in an inactive state, and the switching mechanism 95 that continuously generates the AC output of the AC converting circuit 2 is turned on. The start signal generating unit 93 that generates the start signal is converted to a cancel state in which the switching mechanism 95 is in an inactive state when the start signal generating unit 93 generates a start signal, and the detected current of the tube current detecting circuit 5 is equal to or higher than the reference value. At this time, the switching mechanism 95 is made into the state transition means 96 in the allowable state of the on state. When the tube current IL hardly flows to the start of the discharge tube 3, the dimming signal VB applied from the dimming signal generating circuit 4 to the dimming control circuit 7 is invalidated by the dimming conversion circuit 9, and thus the AC conversion is performed. The AC output V1 of the circuit 2 is continuously supplied to the discharge tube 3. Thereby, the sufficient excitation energy required at the time of starting is quickly supplied to the discharge tube 3, and the discharge tube 3 can be illuminated with an arbitrary brightness in a short time. [Embodiment] Hereinafter, an embodiment of a discharge lamp lighting apparatus according to the present invention will be described with reference to Figs. 1 to 4 . In the first to fourth aspects, substantially the same portions as those in the fifth to eighth embodiments are denoted by the same reference numerals, and the description thereof will be omitted. As shown in Fig. 1, the discharge lamp lighting device of the present embodiment is a period Tc (Fig. 3) in which the tube current detecting circuit 5 does not detect the tube current IL of the cold cathode tube 3, and the dimming signal is obtained from the dimming signal. The dimming signal VB of the generating circuit 4 is applied to the dimming control circuit 7 to be inactive, and the AC voltage VL is continuously generated from the AC converting circuit 2, and the tube current detecting circuit 5 detects the cold-10-(8) 1267323 cathode tube 3 When the tube current IL is connected, the dimming conversion circuit 9 for driving the dimming control circuit 7 is connected to the tube current detecting circuit 5, which is different from the conventional discharge lamp lighting device shown in Fig. 5. As shown in FIG. 2, the dimming conversion circuit 9 is a single-shot pulse generator 93 including a start signal generating means for generating a single-shot pulse start signal Vp when a power switch (not shown) is turned on, and An output terminal is connected to an input terminal of the AND gate 7 1 of the dimming control circuit 7, and an OR gate 95 of a switching mechanism of the dimming signal generating circuit 4 is connected to the other input terminal, and The other input terminal of the R gate 95 is connected to the R-S flip-flop 94 of the state holding mechanism of the state terminal and connected to the reset terminal of the single-shot pulse generator 93, and as the R-S flip-flop 94. The comparator 92 of the comparison means for which the terminal is applied to the output is set, and the reference power source 9 1 which generates the reference voltage VR2 which is the minimum detection of the tube current IL flowing in the cold cathode tube 3 is generated. The reference power source 193, the comparator 92, and the R-S flip-flop 94 constitute a state transition mechanism 96 connected between the tube current detecting circuit 5 and the dimming control circuit 7. The state transition mechanism 96 is switched to a cancel state in which the OR gate 95 is in an inactive state when the single pulse generator 93 generates a start signal, and when the detected current 値 of the tube current detecting circuit 5 is equal to or greater than the reference ,, The R gate 95 is in an allowable state in an on state. 〇R gate 915 is converted into an on state and an inactive state. When the R-S flip flop 94 is in an allowable state, the 〇R gate 95 is converted into an on state, and the dimming signal VB is dimmed. The signal generating circuit 4 is effectively supplied to the dimming control circuit 7, and the -11 - 1267323 Ο AC output of the AC converting circuit 2 is intermittently generated. Further, when the R-S flip-flop 94 is in the cancel state, the OR gate 96 is converted into the inactive state, and the dimming signal VB supplied from the dimming signal generating circuit 4 to the dimming control circuit 7 is made invalid. The AC output of the AC conversion circuit 2 is continuously generated. The comparator 92 is a non-start signal VE2 that generates a low voltage L level when the detection voltage VF of the tube current detecting circuit 5 is lower than the reference voltage VR2 of the reference power source 91, and the detection voltage Vf of the tube current detecting circuit 5 is used as a reference. When the reference voltage VR2 of the power supply 91 is equal to or higher than the reference voltage VR2, the high voltage Η level start signal VE2 is generated. The R-S flip-flop 94 is in a reset state (cancellation state) when the start signal VP is input from the single-shot pulse generator 93 to the reset terminal R, and the output signal VE2 of the comparator 92 is low-voltage L-bit. The period of the quasi-non-start signal is maintained in the reset state (cancellation state), and thus the OR gate 95 is in an inactive state. Further, the R-S normalizer 94 is such that the detection voltage VF of the tube current detecting circuit 5 becomes higher than the reference voltage VR2 of the reference power source 91, and the start signal VE2 of the high voltage clamp level is generated at the setting terminal S by the comparator 92. The time is converted to the set state (allowed state). Therefore, the OR gate 95 is in an on state, and outputs a logical sum signal Vc of the commutation output signal Vq of the R-S flip-flop 94 and the dimming signal VB of the dimming signal generating circuit 4. The reference voltage VR2 of the reference power source 91 of the dimming conversion circuit 9 is set to be lower than the reference voltage V R i of the reference power source 6 1 of the tube current control circuit 6. Further, the AND gate 71 of the dimming control circuit 7 outputs a logical sum signal V output from the dimming conversion circuit 9. The logic signal VD of the current control signal Va outputted from the tube current control circuit 6. -12- (10) 1267323 The other configuration is approximately the same as that of the conventional discharge lamp lighting device shown in Fig. 6. In the above configuration, when the power switch (not shown) is turned on at time t1 (Fig. 3) and the power is turned on, the single-shot pulse start signal VP is output from the single-shot pulse generator 93 in the dimming conversion circuit 9, and is input. The reset terminal R to the r-S flip-flop 94 causes the R-S flip-flop 91 to be in a reset state, that is, to be in a cancel state. At the same time, as shown in the third (A) diagram, the frequency is lower than the frequency of the current control signal VA (tens to hundreds of KHz) of the tube current control circuit (about tens of Hz). The dimming signal VB of the rectangular pulse train having an action ratio corresponding to the desired luminance of the cold cathode tube 3 is output from the dimming signal generating circuit 4, and is input to the OR gate in the dimming conversion circuit 9. 95. As shown in the third figure (D), the tube current IL hardly flows in the cold cathode tube 3 from the dark start period Te from the time when the power is supplied until the start of lighting t2, and the tube current detecting circuit 5 does not flow. The detection voltage VF is lower than the reference voltage VR2 of the reference power supply 91 in the dimming conversion circuit 9, and thus the output signal VE2 of the low voltage L level is output from the comparator 92. Therefore, the commutation output signal Vq of the high voltage clamp level is output from the commutation output terminal of the R-S flip-flop 94 of the reset state (cancellation state), and is input to the 〇R gate 95. Thereby, as shown in Fig. 3(B), the logical sum signal V having a constant positive voltage level is obtained. Since the 〇R gate 95 in the inactive state is applied to the AND gate 71 of the dimming control circuit 7, the dimming signal VB from the dimming signal generating circuit 4 is invalid, and the dimming control circuit 7 does not perform. The dimming action of the cold cathode tube 3. Therefore, the current control signal VA input from the tube current control circuit 6-13-(11) 1267323 to the AND gate 7 1 of the dimming control circuit 7 is output from the dimming control circuit 7 as the logical product signal Vd. The drive signal V is continuously supplied from the drive circuit 8 to the rectangular wave voltage generating circuit 21 in the AC conversion circuit 2, whereby the rectangular wave voltage generating circuit 21 in the AC conversion circuit 2 is continuously driven, via The series resonant circuit 24 is continuously supplied to the cold cathode tube 3 as a high-voltage sinusoidal alternating voltage as shown in the third (C) diagram. At time t2, as shown in the third (D) diagram, the tube current IL starts to flow, and the cold cathode tube 3 starts to light, and the detection voltage VF of the tube current detecting circuit 5 becomes the reference in the dimming conversion circuit 9. When the reference voltage VR2 of the power source 91 is equal to or higher than the reference voltage VR2 of the power source 91, the output signal VE2 of the high voltage level is output from the comparator 92, and is input to the setting terminal S of the R-S flip-flop 94 so that the R-S flip-flop 94 becomes the setting. The state is the allowable state. At this time, the low-voltage L-level commutated output signal Vq is output from the commutation output terminal of the R-S flip-flop 94, and thus the OR gate 95 is converted into an on state, as in the third (B). After the time t2 shown in the figure, the dimming signal VB of the dimming signal generating circuit 4 shown in the third (A) diagram is output from the OR gate 95 as the logical sum signal Vc, and is applied to the dimming control circuit 7 Gate 71. Therefore, the current control signal VA of the tube current control circuit 6 interrupted by the period of the dimming signal VB of the dimming signal generating circuit 4 is output from the AND gate 71 of the dimming control circuit 7 as the logical product signal VP, so that the driving signal The VG is intermittently applied from the drive circuit 8 to the rectangular wave voltage generating circuit 21 in the AC conversion circuit 2. Thus, the rectangular wave voltage generating circuit 2 1 in the 'AC converting circuit 2' is intermittently driven by the period -14 - (12) 1267323 of the dimming signal VB, via the series resonant circuit 24, as shown in the third (C) diagram. The high-voltage sinusoidal alternating current voltage VL shown is intermittently supplied to the cold cathode tube 3 at the period of the dimming signal VB. Therefore, after the start of the cold cathode tube 3, after t2, the tube current TS continues to flow continuously in the cold cathode tube 3 as shown in the third (D), so that the cold cathode tube 3 has a period of the dimming signal Vb. The dimming operation of the cold cathode tube 3 is repeated. At the same time, the tube current IL of the cold cathode tube 3 is kept constant by the tube current control circuit 6, and the brightness of the cold cathode tube 3 is often constant. In the present embodiment, the tube current I1 hardly flows at the start of the cold cathode tube 3, that is, during the dark start period T. The dimming signal VB applied to the dimming control circuit 7 from the dimming signal generating circuit 4 by the dimming conversion circuit 9 is disabled, and thus the dimming operation of the cold cathode tube 3 by the dimming control circuit 7 is not performed. . Thereby, the AC voltage VL of the AC converter circuit 2 is continuously and rapidly supplied to the cold cathode tube 3, so that the sufficient excitation energy required for lighting can be quickly supplied to the cold cathode tube 3. When the cold cathode tube 3 is started to be lit, the φ dimming signal VB from the dimming signal generating circuit 4 is applied to the dimming control circuit 7, and the dimming operation of the cold cathode tube 3 by the dimming control circuit 7 is performed. Therefore, the cold cathode tube 3 can be illuminated with an arbitrary brightness. Therefore, the cold cathode tube 3 can be illuminated with an arbitrary brightness in a short time. Actually, when the on-state action of the dimming signal VB outputted from the dimming signal generating circuit 4 is set to 50%, the time Tc from when the device is started q to the time t2 when the cold cathode tube 3 starts lighting can be obtained. It is shortened to about half of the same time TB when it is shown in the conventional discharge lamp lighting device of Figs. 5 and 6. -15-(13) 1267323 Fig. 4 is a diagram showing a current control signal VA having a constant conduction width which varies in the off period of the rectangular pulse train in accordance with the level of the error voltage Vei outputted from the error amplifier 62. A modified embodiment of the tube current control circuit 6 of the pulse frequency modulation method of the voltage-frequency conversion circuit (shown as V/F inverter in the figure) 65. The embodiment of the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the alternating current converting circuit 2 is constituted by the rectangular wave voltage generating circuit 21 and the series resonant circuit 24 formed by the leakage transformer 22 and the resonant capacitor 23. However, instead of the leakage transformer 22, a coil of a single winding is used, and a rectangular shape is used. The number of turns of the output transformer in the wave voltage generating circuit 2 1 may be set to about 1 而 to constitute the alternating current converting circuit 2. In the above-described embodiment, the tube current detecting circuit 5 is constituted by the tube current detecting resistor 51, the rectifier diode 52, and the smoothing capacitor 5, but a tube current detecting circuit (current-voltage conversion) including an operational amplifier or the like is used. Circuit) is also available. Further, in the above-described embodiment, the tube current control using the pulse width modulation (PWM) method of the current control signal VA of the rectangular pulse train whose output on-state action is changed is used in accordance with the level of the detection voltage VF of the tube current detecting circuit 5. In the circuit 6, the tube current control circuit 6 of the pulse frequency modulation (PFM) method of the current control signal VA of the rectangular pulse train whose output frequency is changed according to the level of the detection voltage VF of the tube current detecting circuit 5 may be used. . In the above-described embodiment, the switching mechanism in the dimming conversion circuit 9 is configured by the OR gate 95, but the switching means is formed using a switching element such as a transistor or the like, and the R-S flip-flop 94 is in the reset state. The switching element is turned off, and the dimming signal VB from the dimming signal generating circuit 4 is blocked while the dimming signal VB of the dimming signal generating circuit 4 is blocked, and the signal having a positive voltage level is given to the dimming control circuit 7, On the other hand, when the R-s flip-flop 9 is switched to the set state, the switching element is turned on, and the dimming signal Vb from the dimming signal generating circuit 4 is applied to the dimming control circuit 7. Instead of the single-shot pulse generator in the dimming conversion circuit 9, a differential circuit and an inverter formed using a resistor and a capacitor are used to impart a differential pulse signal output from the differential circuit via the inverter when the power is turned on. The configuration of the reset terminal R may be sufficient. Industrial Applicability The discharge lamp lighting device of the present invention is suitable for use as a cold cathode tube such as a back surface illumination of a liquid crystal display device such as a liquid crystal television or a notebook computer. In particular, when the set brightness of the discharge lamp is applied to the dimming control circuit when the narrow dimming signal of the on-state operation is applied, the effect of the present invention remarkably occurs when the discharge lamp is not lit for a long period of time and is placed in a cold dark place. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit block diagram showing an embodiment of a discharge lamp lighting device according to the present invention. Fig. 2 is a circuit diagram showing the internal structure of each circuit block in Fig. 1. Figs. 3(A) to 3(D) are waveform diagrams showing voltages and currents of respective portions of the circuit of Fig. 1. Figs. Fig. 4 is a circuit diagram showing a modified embodiment of Fig. 2; -17- (15) 1267323 Fig. 5 is a circuit block diagram showing a conventional discharge lamp lighting device. Fig. 6 is a circuit diagram showing the internal structure of each circuit block of Fig. 5. 7(A) to 7(C) are waveform diagrams showing voltages and currents of respective portions of the circuit of Fig. 5 when the dimming operation is not performed. Figs. 8(A) to 7(C) are waveform diagrams showing voltages and currents of respective portions of the circuit of Fig. 5 when the dimming operation is performed. [Main component comparison table] 1 DC power supply 2 AC conversion circuit 3 Discharge tube (cold cathode tube) 4 Dimming signal generation circuit 5 Tube current detection circuit 6 Tube current control circuit 7 Dimming control circuit ® 8 Drive circuit 9 Dimming conversion Circuit 2 1 Rectangular wave voltage generating circuit 22 Leakage transformer 2 2 a - Secondary winding 2 2 b Secondary winding 22c Leakage reactance 23 Resonant capacitor -18- (16) (16) 1267323 24 Series resonant circuit 51 Tube current detecting resistor 5 2 Rectifier diode 5 3 Rectifier capacitor 6 1 Reference power supply 62 Error amplifier 63 Triangular wave oscillation circuit 7 1 AND gate φ 9 1 Reference power supply 92 Comparator 93 Single pulse generator 94 R—S positive and negative device 95 0R gate VIN DC voltage Vl AC voltage VB dimming signal VA current control signal II tube current VD output signal (logical product signal) VG drive signal (logical product signal)
Vs 矩形波交流電壓 VF 檢測電壓 VR1、VR2 基準電壓 VE1輸出電壓 -19- 1267323 (17) VT 三角波電壓 VL 正弦波交流電壓 Vl 邏輯和信號Vs Rectangular wave AC voltage VF Detection voltage VR1, VR2 Reference voltage VE1 Output voltage -19- 1267323 (17) VT Triangle voltage VL Sine wave AC voltage Vl Logic sum signal
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