200917217 .九、發明說明： 【發明所屬之技術領域】 本發明係關於一種背光調節電路。 【先前技術】 狀曰日顯不由扳因具有低輻射性、厚度薄及耗電低等与 點，已廣泛應用於筆記本電腦、手機等現代化資訊1備中 惟’液晶顯示面板中之液晶本身不具發光特性，為達到· 示功效，需給液晶顯示面板提供背光源。 』一併參閱圖1及圖2,圖1係-種先前技術背光, ::::笔路方框示意圖’圖2係圖1所示之背光調節^ =應之一示例性輝度菜單示意圖。該背光調節電路 二括-縮放控制器12、一輝度調整按鍵u 體（1响—L卿4。該縮放控制哭= 次電連接之一處理雷改U包括炎 分電路122。 脈衝產生電路121及1 =縮放控制H12用於為該發光二極 二該=調節按鍵”用於調節該發光二極體二= 等、，及，亚發送輝度調節訊號至 輝 路12〇用於户—从 处王电路12〇。該處理 -次輝母!"―次該輝度調整按鍵η後，即每接收 級至該脈衝產生電：121t 先二極體14之輝度 生电路121。垓脈衝產生雷 存儲該輝度菜單之輝度等級—方面 按—次該輝度調整按㈣後兮另：；方面可即時計算- 與該輝度等級數量之比例，並H 14之輝度㈣ 產生一疋脈九與週期比例< 200917217 脈衝訊號。以圖2為例，輝度菜單之輝度等級數量為10， 該發光二極體14之輝度等級為6，則該脈衝產生電路121 產生脈寬與週期比例為3 : 5之脈衝訊號。該積分電路122 用於即時計算每按一次該輝度調整按鍵11後之脈衝訊號 對應之直流電壓，並輸出至該發光二極體14，從而調節該 發光二極體14之輝度。 通常為了滿足用戶對該發光二極體14輝度之高精度 及大範圍調節之需求，廠家將該輝度菜單之輝度等級設置 為較多，每按一次該輝度調整按鍵11，該發光二極體14 之輝度等級改變一個輝度等級。然而，在該輝度菜單之輝 度等級較多之情況下，相鄰輝度等級之間之輝度變化範圍 較小，每按一次該輝度調整按鍵11對該發光二極體14之 輝度改變較小。若用戶需要大範圍調節該發光二極體14 之輝度，需要多次按下該輝度調整按鍵11，給用戶帶來不 方便且造成時間之浪費。例如，若該發光二極體14之輝度 等級數量為50,每按一次該輝度調整按鍵11，該發光二極 體14之輝度等級僅能改變1級；若要將發光二極體14之 輝度等級從1調節至48，則需要按47次該輝度調整按鍵 11。因此該背光調節電路10不能在較短之時間内實現背光 源輝度之高精度及大範圍之調節。 【發明内容】 有鑑於此，提供一種可在短時間内實現背光源輝度之 高精度及大範圍之調節之背光調節電路實為必需。 一種背光調節電路，其包括一背光源，一背光驅動電 8 200917217 調按鍵，一縮放電路及一調光訊號 .路’ 一粗調按鍵，— 處理電路。該皆古％吩久一碉无訊號 -^ 11先驅動電路用於驅動該背光源。该粗喟# 鍵及該細調按鍵分別 垓粗凋按 發訊號。該縮放電路㈣2 觸發訊號及一細調觸 = = f:電壓及一脈寬調制訊號並疊加為-疊 訊號積分平滑產生一㈣物加調光控制 财背Ϊ 亥背光驅動電路，進而粗 過及月光源之輝度，同時， 光控制訊號分離出該脈寬㈣=5虎;=路從該疊加調 出至节其作為—細調訊號輸 出至“総動電路，進而細調該背光源之輝度。 :較於先前技術，前述背光調節電路包括一粗調按 細顺鍵、—縮放電路及―調光訊號處理電路 i 财理接收之粗簡發訊號及細調觸發訊 調光控制訊號，該疊加嫩I:;::说合成之-疊加 雷_ 0 Μ 門光控制5过餐由該調光訊號處理 、諸Ϊ彳輸出—粗調訊號或—細調訊號，實現對該背光 大範圍調節或高精度調節’因而可以減少按鍵之 調即次數，且提高背光調節精度。 【實施方式】 請參閱圖3,係本發明背光調節電路第一實施方式之 方框示意圖。該背光調節電路2G包括—粗調按鍵Η、一 細調按鍵22、-縮放電路（scaler)23、—調光訊號處理電路 24、-背光驅動電路25及一背光源2“該縮放電路& 邊调光訊號處理電路24、該背光驅動電路25及該背光源 200917217 • 連接。該粗調按鍵21與該細調按鍵22係人機交 •路^粗^按鍵21用於發送粗調觸發訊號至該縮放電 =、田㉟按鍵22用於發送細調觸發訊號至該縮放電 路23。該縮放電路23虚採兮· ^ π雜& _ D. v 處理該細調觸發訊號及該粗調觸發 細調控制訊號及—粗調控制訊號，並將 :调控制訊號及該粗調控制訊號調制合成為-疊加調光 口只乃光訊號處理電路24虚壬审兮晶丄 *认山, 电峪Z4處理該豎加調光控制訊號 =出-粗調訊號或—細調訊號至該背光驅動電路25。該 二：動電路25根據該粗調訊號或該細調訊號驅 2 %以實現背光輝度等級之大範圍或高精度之變化。該 月光源26係發光二極體或冷陰極螢光燈管。 電路23包括一粗調處理電路231、一粗調控制 ==生電路232、-細調處理電路233、_細調控制訊號 ，生电路234及-調制合成電路说。該調制合成電路加 包括一可控式可變電阻（圖未示）。該粗調處理電路231用 ^貞測該粗調按鍵21發出之粗調觸發訊號。當該粗調處理 电路23!偵測到-粗調觸發訊號後，該粗調控制訊號產生 電路232相應產生-粗調控制訊號並輪出至該調制合成電 路235。該粗調控制訊號控制該可控式可變電阻之滑動端 ，生-直流分壓。該細調處理電路233用於偵測該細調按 鍵22發出之細調觸發訊號。當該細調處理電路偵測到 一細調觸發訊號後，該細調控制訊號產生電路2^相應產 生一細調控制訊號並輸出至該調制合成電路。其中， 200917217 該細調控制訊號為一脈寬調制（PWM)訊號，每按一次該細 調按鍵22，該脈寬調制訊號之脈衝寬度相應增加。由於該 縮放電路23為一積體電路，受其輸出端口之限制，該調制 合成電路235將該直流分壓與該脈寬調制訊號疊加合成為 該4加調光控制訊號。 該調光訊號處理電路24包括一第一積分平滑電路 241、一反向電路242、一脈寬調制訊號分離電路243、一 第二積分平滑電路244、一加法電路245、一放大電路246、 一選擇器247及一計數比較電路248。該第一積分平滑電 路241與該脈寬調制訊號分離電路243分別接收該調制合 成電路235輸出之疊加調光控制訊號。該第一積分平滑電 路241對該疊加調光控制訊號積分，其輸出一第一正向直 流電壓，該反向電路242將該第一正向直流電壓反向，輸 出一反向直流電壓至該加法電路245。該脈寬調制訊號分 離電路243從該疊加調光控制訊號中分離出該脈寬調制訊 號並輸出至該第二積分平滑電路244。該第二積分平滑電 路244對該脈寬調制訊號積分後輸出一第二正向直流電壓 至該加法電路245。該加法電路245將該反向直流電壓與 該第二正向直流電壓相加並反向，並經由該放大電路246 放大後輸入該選擇器247之第一選擇端2471，其作為一用 於大範圍調節該背光源輝度之粗調訊號。該選擇器247之 第二選擇端2472同時接收該第二積分平滑電路244輸出之 該第二正向直流電壓，其作為一用於高精度調節該背光源 輝度之細調訊號。 11 200917217 同時，該脈寬調制訊號分離電路243輸出該脈寬調制 訊號至該計數比較電路248。該計數比較電路248包括一 計數比較器2481、一記憶體2482及一時鐘訊號發生器 2483。該記憶體2482存儲一初始脈寬調制訊號之脈寬值。 該時鐘訊號發生器2483產生一時鐘訊號用於計算該計數 比較器2481接收之脈寬調制訊號之脈寬值。該計數比較器 2481比較該初始脈寬調制訊號及其接收之脈寬調制訊號 之脈寬值，若該二脈寬值不同，則該計數比較器2481輸出 一高電平至該選擇器247，同時將該脈寬調制訊號之脈寬 值存儲至該記憶體2482，用於下一次之脈寬比較。該高電 平控制該選擇器247選擇將該第二選擇端2472輸入之細調 訊號輸出至該背光驅動電路25，該背光驅動電路25對背 光源26之輝度進行細調。若該二脈寬值相同，該計數比較 器2481輸出一低電平至該選擇器247，該低電平控制該選 擇器247選擇將該第一選擇端2471輸入之粗調訊號輸出至 該背光驅動電路25，該背光驅動電路25對背光源26之輝 度進行粗調。 相較於先前技術，該背光調節電路20包括一縮放電路 23及一調光訊號處理電路24，該縮放電路23包括一粗調 處理電路231及一細調處理電路233，可以分別處理該粗 調按鍵21及該細調按鍵22發出之觸發訊號。該縮放電路 23形成一疊加調光控制訊號，經由該調光訊號處理電路24 處理後可以分別實現對該背光源輝度之大範圍調節或高精 度調節，因而可以減少按鍵之調節次數，且提高背光調節 12 200917217 精度。 請參閱圖4,本發明背光調節電路第二實施方式之方 框示意圖。該背光調節電路30之調光訊號處理電路34包 括一第一積分平滑電路341、一反向電路342、一脈寬調制 訊號分離電路343、一第二積分平滑電路344、一加法電路 345、一放大電路346、一選擇器347及一計數比較電路 348。該背光調節電路30與該背光調節電路20相比，其區 別僅在於：該第一積分平滑電路341對其接收之疊加調光 控制訊號積分並輸出一第一正向直流電壓至該加法電路 345。該脈寬調制訊號分離電路343將其接收之疊加調光控 制訊號分離出一脈寬調制訊號並輸出至該第二積分平滑電 路344。該第二積分平滑電路344對該脈寬調制訊號積分 後輸出一第二正向直流電壓至該反向電路342，該反向電 路342將該第二正向直流電壓反向後輸出一反向直流電壓 至該加法電路345。該加法電路345將該反向直流電壓與 該弟正向直流電壓相加並經由該放大電路3 4 6放大後輸 、 入該選擇器347，其作為一粗調訊號。與該第一實施方式 相比，該加法電路345將該反向直流電壓與該第一正向直 流電壓相加後為一正向電壓，直接經由該放大電路345放 大後輸入該選擇器347 ’無需再反向便可經由該放大電路 345放大並輸入該選擇器347。 综上所述，本發明確已符合發明專利之要件，爰依法 提出專利申請。惟，以上所述者僅為本發明之較佳實施方 式，本發明之範圍並不以上述實施方式為限，舉凡熟悉本 13 200917217 案技藝之人士援依本發明之精神所作之等效修飾或變化， 皆應涵蓋於以下申請專利範圍内。 '【圖式簡單說明】 圖1係一種先前技術背光調節電路之電路方框示意圖。 圖2係圖1所示背光調節電路對應之一示例性輝度菜單示 意圖。 圖3係本發明背光調節電路第一實施方式之方框示意圖。 圖4係本發明背光調節電路第二實施方式之方框示意圖。 【主要元件符號說明】 背光調節電路 20 、30 反向電路 242 > 342 粗調按鍵 21 加法電路 245 > 345 細調按鍵 22 放大電路 246 > 346 縮放電路 23 選擇器 247 ' 347 背光驅動電路 25 計數比較電路 248 、 348 背光源 26 計數比較器 2481 粗調處理電路 231 記憶體 2482 細調處理電路 233 第一選擇端 2471 調制合成電路 235 第二選擇端 2472 脈寬調制訊號分離電路 243 、 343 第二積分平滑電路 244 ' 344 粗調控制訊號產生電路 232 細調訊號產生電路 234 第一積分平滑電路 241 、 341 調光訊號處理電路 24、34 時鐘訊號發生器 2483 14200917217. IX. INSTRUCTIONS: TECHNICAL FIELD OF THE INVENTION The present invention relates to a backlight adjustment circuit. [Prior Art] The 曰 曰 显 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 具有 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已 已In order to achieve the effect, it is necessary to provide a backlight for the liquid crystal display panel. Referring to FIG. 1 and FIG. 2 together, FIG. 1 is a prior art backlight, and :::: a schematic diagram of a pen path. FIG. 2 is a schematic diagram of an exemplary brightness menu shown in FIG. The backlight adjustment circuit includes a zoom controller 12 and a luminance adjustment button u body (1 ring - L Qing 4. The zoom control cry = one of the secondary electrical connections processing the lightning change U includes the inflammation circuit 122. The pulse generation circuit 121 And 1 = zoom control H12 is used for the light-emitting diode 2 = adjust button "for adjusting the light-emitting diode 2 =, etc., and, sub-transmitting the brightness adjustment signal to the Hui 12 12 for the household - from Wang circuit 12 〇. The processing - sub-mother! " - the second brightness adjustment button η, that is, each receiving stage to the pulse to generate electricity: 121t first diode 14 glow generating circuit 121. 垓 pulse generating thunder storage The brightness level of the brightness menu - the aspect is adjusted according to the time (4) and then the other:; the aspect can be calculated immediately - the ratio of the number of the brightness levels, and the brightness of the H 14 (4) produces a pulse and a cycle ratio < 200917217 For example, in FIG. 2, the luminance level of the luminance menu is 10, and the luminance level of the LED 14 is 6, the pulse generation circuit 121 generates a pulse signal with a pulse width and a period ratio of 3:5. The integration circuit 122 is used for instant The DC voltage corresponding to the pulse signal after the brightness adjustment button 11 is pressed once is output to the light emitting diode 14 to adjust the brightness of the light emitting diode 14. Generally, the user needs to adjust the brightness of the light emitting diode 14. For the high-precision and wide-range adjustment of the luminance, the manufacturer sets the luminance level of the luminance menu to be more. Each time the luminance adjustment button 11 is pressed, the luminance level of the LED 14 changes by one luminance level. When the luminance level of the luminance menu is large, the luminance variation range between adjacent luminance levels is small, and the luminance adjustment button 11 changes the luminance of the LED 14 to be small each time the user presses the button. The range adjusts the brightness of the light-emitting diode 14 , and the brightness adjustment button 11 needs to be pressed multiple times, which is inconvenient to the user and wastes time. For example, if the brightness level of the light-emitting diode 14 is 50, Each time the brightness adjustment button 11 is pressed, the brightness level of the light-emitting diode 14 can only be changed by one level; if the brightness level of the light-emitting diode 14 is adjusted from 1 to 48, The brightness adjustment button 11 is pressed 47 times. Therefore, the backlight adjustment circuit 10 cannot achieve high precision and wide range adjustment of the backlight luminance in a short period of time. [Invention] In view of this, it is possible to provide a short time A backlight adjustment circuit that achieves high precision and wide range adjustment of backlight brightness is necessary. A backlight adjustment circuit includes a backlight, a backlight driving power 8 200917217 key button, a zoom circuit and a dimming signal. 'A coarse adjustment button, - processing circuit. This is the ancient % ー long time no signal - ^ 11 first drive circuit is used to drive the backlight. The rough 喟 # key and the fine adjustment button respectively 凋 凋 发 发 发. The scaling circuit (4) 2 trigger signal and a fine touch == f: voltage and a pulse width modulated signal and superimposed as - the integrated signal smoothing produces a (four) object plus dimming control, the back backlight driving circuit, and then coarse The brightness of the moonlight source, at the same time, the light control signal separates the pulse width (4) = 5 tiger; = the road is transferred from the superposition to the node as a fine-tuned signal output to the "swing circuit, and fine-tuning the brightness of the backlight Compared with the prior art, the backlight adjustment circuit includes a coarse adjustment key, a scaling circuit, and a dimming signal and a fine adjustment trigger light control signal received by the dimming signal processing circuit i. Superimposed tender I:;:: said synthetic - superimposed mine _ 0 Μ door light control 5 meal by the dimming signal processing, the output of the — - coarse adjustment signal or - fine tuning signal, to achieve a large range of adjustment of the backlight Or high-precision adjustment 'Therefore, the number of key adjustments can be reduced, and the backlight adjustment precision can be improved. [Embodiment] Please refer to FIG. 3, which is a block diagram of a first embodiment of the backlight adjustment circuit of the present invention. The backlight adjustment circuit 2G includes - coarse adjustment Key Η, a fine adjustment button 22, a scaling circuit 23, a dimming signal processing circuit 24, a backlight driving circuit 25, and a backlight 2, the scaling circuit & edge dimming signal processing circuit 24, The backlight driving circuit 25 and the backlight 200917217 • are connected. The coarse adjustment button 21 and the fine adjustment button 22 are connected by a human machine. The road ^ coarse ^ button 21 is used to send a coarse adjustment trigger signal to the zoom power =, the field 35 button 22 is used to send a fine adjustment trigger signal to the zoom circuit twenty three. The scaling circuit 23 processes the fine adjustment trigger signal and the coarse adjustment trigger fine adjustment control signal and the coarse adjustment control signal, and adjusts the control signal and the coarse adjustment control. The signal modulation synthesis is - the superimposed dimming port is only the optical signal processing circuit 24 壬 壬 壬 丄 认 认 认 认 认 认 认 认 认 , , , , , , , , , , , , , , , , , , , , , , , , , , , , 竖 竖 竖 竖 竖The backlight drive circuit 25. The two: the dynamic circuit 25 drives 2% according to the coarse adjustment signal or the fine adjustment signal to achieve a wide range or high precision change of the backlight luminance level. The light source 26 is a light-emitting diode or a cold cathode fluorescent tube. The circuit 23 includes a coarse adjustment processing circuit 231, a coarse adjustment control == generation circuit 232, a fine adjustment processing circuit 233, a fine adjustment control signal, a generation circuit 234, and a modulation synthesis circuit. The modulation synthesis circuit includes a controllable variable resistor (not shown). The coarse adjustment processing circuit 231 uses the coarse adjustment trigger signal sent by the coarse adjustment button 21. After the coarse adjustment processing circuit 23! detects the coarse adjustment trigger signal, the coarse adjustment signal generation circuit 232 correspondingly generates a coarse adjustment control signal and rotates to the modulation synthesis circuit 235. The coarse control signal controls the sliding end of the controllable variable resistor, the raw-DC partial voltage. The fine adjustment processing circuit 233 is configured to detect the fine adjustment trigger signal sent by the fine adjustment button 22. After the fine-tuning processing circuit detects a fine-tuning trigger signal, the fine-tuning control signal generating circuit 2^ generates a fine-tuning control signal and outputs the fine-tuning control signal to the modulation combining circuit. Wherein, the 200917217 fine-tuning control signal is a pulse width modulation (PWM) signal, and the pulse width of the pulse width modulation signal is increased each time the fine adjustment button 22 is pressed. Since the scaling circuit 23 is an integrated circuit, the modulation combining circuit 235 superimposes the DC voltage division and the pulse width modulation signal into the 4 plus dimming control signals. The dimming signal processing circuit 24 includes a first integral smoothing circuit 241, a reverse circuit 242, a pulse width modulated signal separating circuit 243, a second integral smoothing circuit 244, an adding circuit 245, an amplifying circuit 246, and a The selector 247 and a count comparison circuit 248. The first integral smoothing circuit 241 and the pulse width modulation signal separating circuit 243 respectively receive the superimposed dimming control signals output by the modulation synthesizing circuit 235. The first integral smoothing circuit 241 integrates the superimposed dimming control signal, and outputs a first forward DC voltage, and the inverting circuit 242 inverts the first forward DC voltage to output a reverse DC voltage to the Addition circuit 245. The pulse width modulation signal separation circuit 243 separates the pulse width modulation signal from the superimposed dimming control signal and outputs the pulse width modulation signal to the second integration smoothing circuit 244. The second integrating smoothing circuit 244 integrates the pulse width modulated signal to output a second forward DC voltage to the adding circuit 245. The adding circuit 245 adds and reverses the reverse DC voltage and the second forward DC voltage, and is amplified by the amplifying circuit 246 and input to the first selection terminal 2471 of the selector 247, which is used as a large The range adjusts the coarse adjustment signal of the backlight luminance. The second selection terminal 2472 of the selector 247 simultaneously receives the second forward DC voltage output by the second integration smoothing circuit 244 as a fine adjustment signal for adjusting the luminance of the backlight with high precision. 11 200917217 At the same time, the pulse width modulation signal separation circuit 243 outputs the pulse width modulation signal to the count comparison circuit 248. The count comparison circuit 248 includes a count comparator 2481, a memory 2482, and a clock signal generator 2483. The memory 2482 stores a pulse width value of an initial pulse width modulated signal. The clock signal generator 2843 generates a clock signal for calculating the pulse width value of the pulse width modulated signal received by the counter comparator 2481. The counting comparator 2481 compares the pulse width value of the initial pulse width modulation signal and the received pulse width modulation signal. If the two pulse width values are different, the counting comparator 2481 outputs a high level to the selector 247. At the same time, the pulse width value of the pulse width modulated signal is stored in the memory 2482 for the next pulse width comparison. The high level control selector 247 selects the fine adjustment signal input to the second selection terminal 2472 to output to the backlight driving circuit 25, and the backlight driving circuit 25 finely adjusts the luminance of the backlight 26 . If the two pulse width values are the same, the count comparator 2481 outputs a low level to the selector 247, and the low level controls the selector 247 to select the coarse adjustment signal input by the first selection terminal 2471 to the backlight. The driving circuit 25 performs coarse adjustment of the luminance of the backlight 26. Compared with the prior art, the backlight adjustment circuit 20 includes a scaling circuit 23 and a dimming signal processing circuit 24. The scaling circuit 23 includes a coarse adjustment processing circuit 231 and a fine processing circuit 233, which can respectively process the coarse adjustment. The trigger signal sent by the button 21 and the fine button 22 is used. The scaling circuit 23 forms a superimposed dimming control signal, and the dimming signal processing circuit 24 can realize large-scale adjustment or high-precision adjustment of the luminance of the backlight, thereby reducing the number of adjustments of the button and improving the backlight. Adjust 12 200917217 accuracy. Referring to FIG. 4, a block diagram of a second embodiment of a backlight adjustment circuit of the present invention is shown. The dimming signal processing circuit 34 of the backlight adjustment circuit 30 includes a first integration smoothing circuit 341, a reverse circuit 342, a pulse width modulation signal separation circuit 343, a second integration smoothing circuit 344, an adding circuit 345, and a The amplifier circuit 346, a selector 347 and a count comparison circuit 348. The backlight adjustment circuit 30 is different from the backlight adjustment circuit 20 only in that the first integration smoothing circuit 341 integrates the superimposed dimming control signal received therefrom and outputs a first forward DC voltage to the adding circuit 345. . The pulse width modulation signal separating circuit 343 separates the received superimposed dimming control signal from a received pulse width modulated signal and outputs the pulse width modulated signal to the second integrating smoothing circuit 344. The second integral smoothing circuit 344 integrates the pulse width modulation signal and outputs a second forward DC voltage to the reverse circuit 342. The reverse circuit 342 reverses the second forward DC voltage to output a reverse DC. The voltage is applied to the summing circuit 345. The summing circuit 345 adds the reverse DC voltage to the forward DC voltage and amplifies it via the amplifying circuit 34 to input the selector 347 as a coarse signal. Compared with the first embodiment, the adding circuit 345 adds the reverse DC voltage to the first forward DC voltage to be a forward voltage, and is directly amplified by the amplifying circuit 345 and input to the selector 347 ' The selector 347 can be amplified and input via the amplifying circuit 345 without further reversal. In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above is only a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiments, and those skilled in the art of the present invention will be equivalently modified according to the spirit of the present invention. Changes should be covered by the following patents. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing the circuit of a prior art backlight adjustment circuit. Figure 2 is an illustration of an exemplary luminance menu corresponding to the backlight adjustment circuit of Figure 1. 3 is a block diagram showing a first embodiment of a backlight adjustment circuit of the present invention. 4 is a block diagram showing a second embodiment of the backlight adjustment circuit of the present invention. [Main component symbol description] backlight adjustment circuit 20, 30 reverse circuit 242 > 342 coarse adjustment button 21 addition circuit 245 > 345 fine adjustment button 22 amplification circuit 246 > 346 scaling circuit 23 selector 247 ' 347 backlight driving circuit 25 count comparison circuit 248, 348 backlight 26 count comparator 2481 coarse adjustment processing circuit 231 memory 2482 fine adjustment processing circuit 233 first selection terminal 2471 modulation synthesis circuit 235 second selection terminal 2472 pulse width modulation signal separation circuit 243, 343 Second integral smoothing circuit 244 '344 coarse tuning control signal generating circuit 232 fine tuning signal generating circuit 234 first integral smoothing circuit 241, 341 dimming signal processing circuit 24, 34 clock signal generator 2843 14