TW201115873A - Apparatus for driving light-emitting diode (LED) backlight - Google Patents

Abstract

An apparatus for driving a light-emitting diode (LED) backlight is provided. The apparatus divides the LED backlight into first lightbars and second lightbars for time division control. The apparatus includes a first current mirror, a second current mirror and a control circuit. The first current mirror, if enabled, balances the current of each first lightbar. The second current mirror, if enabled, balances the current of each second lightbar. During a first period, the control circuit disables the second current mirror and modulates the time period of enabling the first current mirror according to a dimming signal and the total current of the first lightbars. During a second period, the control circuit disables the first current mirror and modulates the time period of enabling the second current mirror according to the dimming signal and the total current of the second lightbars. Therefore, only first or second lightbars are driven in each period.

Description

201115873 六、發明說明： 【發明所屬之技術領域】 本發明是有關於一種背光源驅動技術，且特別是一種發光二 極體背光源的驅動裝置。 【先前技術】 現有的液晶顯示器通常採用冷陰極螢光燈管（c〇ld Cathode201115873 VI. Description of the Invention: [Technical Field] The present invention relates to a backlight driving technique, and more particularly to a driving device for a backlight of a light emitting diode. [Prior Art] Existing liquid crystal displays usually use cold cathode fluorescent tubes (c〇ld Cathode)

Fluorescent Lamp，簡稱 CCFL)或發光二極體(Light-EmittingFluorescent Lamp (CCFL) or Light-Emitting

Diode’簡稱LED)作為背光源。但是，由於全球暖化現象日益嚴重， 各國在消費性電子產品功率損耗規範上日趨嚴格，使得CCFL背光 源因其功率損耗較大而漸漸為LED背光源所取代。 圖1為一種現有的LED背光源的驅動裝置之電路圖。請參照 圖1，LED背光源包括m個燈串11〜im，每個燈串1丨均包括〇個 串聯耦接的發光二極體D1〜Dn，其中m、η均為正整數，丨為1〜m 中任正盖數。led背光源的驅動裝置包括直流至直流(dc/dc)轉 換器21及LED控制器22。DC/DC轉換器21為降壓或升壓韓換5!， 用以將常見的5V、12V或24V等規格的直流電壓_轉換為狀 驅動燈串11〜lm的直流電壓Vdc2。每個燈串Η第一端均耦接至 DC/DC轉換H 21以接收錢輕·來麟所需的龍，每個燈 串h第二端則耦接至LED控制器22相應的通道端邙丨。匕助^ 器22摘測每個燈串π電流，並利用内較電流源或可變電^ 方式使每個燈串U電流相等或在—定誤差範_轉 衡’故燈串11〜lm得以在發光時提供均勻的亮度。為了 ^個 燈串h電流平衡且獲得所需賴，LED㈣器22還可從回 端FB达出脈寬調變⑽se_Width此她如，簡稱 ^， 以控制DC/DC轉換器21調整輸出的直流電壓Vdc2大小，^抑 201115873 月光源及LED控制器22可操作於最佳化。當然，led控制器22 也可不送出PWM信號’使DC/DC轉換器21輸出恆定的直流電壓 Vdc2 ’而LED控制器22僅用於使每個燈串Η電流達到平衡。 當LED背光源的燈串η〜im數量太多或採用具有大電流的高 壳發光二極體D1〜Dn時，為了避免LED控制器22因接收的電流 太大而過熱或燒毁，需要採用如圖2所示的外部控制方式。請參 知、圖2，每個燈串u第二端需要外加相應的電晶體以及電阻器 Ri ,其中電晶體Qi為場效電晶體且工作在線性區以作為可變電阻 來調整落在燈串Π上的電壓大小，使每個燈串U冑流達到平衡。 LED控制器220從電流偵測端ISi偵測燈串Η電流在流過電阻器 Ri時所產生與電流大小成正比的電壓值，並根據這個電壓值從通 道端CHi送出信號控制電晶體Qi改變其在線性區的工作點位置， 以改變電晶體Q!提供的可變電阻大小。㈣控制器22Q從電壓伯 測端VDi偵測電晶體q丨源極端上的電壓，在源極端上的電壓過高 時’從通道端CHi送出信號控制電晶體Qi截止以保護電路。 為了獲得更好的電壓調整，還可以如圖3所示採用多個dc/dc 轉換器^提供多個可各自調整的直流電壓到燈串。請參照 圖3 ’每個燈串11第一端轉接至各自相應的DC/DC轉換器21i以 接收直流電壓Vdc2i來獲得所需的電壓，每個燈串π第二端則先 柄，至外加的電晶體Qi及電阻器Ri再耗接至各自相應的⑽控 制器22i @此可以對⑽背光源的驅動做更細緻的操控。 不响如何’圖1〜圖3所示的LED冑光源的驅動裝置都必須採 :用的LED控制H 22、220或221〜22m。而且，隨著LED背光 ΐ =串U〜llD數量的増加，對於圖2所示的LED背光源的驅動 :說其中LED控制器220的接腳數量及外加的電晶體Qi和 阻器Ri數里均會增加，使得電路佈局困難且成本增加，而對於 201115873 圖3所示的LED背光源的驅動裝置來說，其中j)C/DC轉換器211 〜21m、LED控制器221〜22m及外加的電晶體Qi和電阻器Ri數量 均會增加’除了使電路佈局困難且成本增加之外，LED控制器221 〜22m之間的溝通及控制還會因LED控制器數量增加而相形困難。 【發明内容】 有鑑於此，本發明的目的就是在提供一種發光二極體(LED)背 光源的驅動裝置，採用簡單的驅動控制方式，可降低電源轉換器 (如DC/DC轉換器）及LED控制器的使用數量，以降低成本。 為了達成上述目的及其它目的，本發明提出一種發光二極毙 (LED)背光源的驅動裝置。LED背光源包括多個第—燈串及多個驾 二燈串，每個第-燈串及第二燈串均包括多個串聯输的發光二 極體，每個第-燈串及第二燈串第一端均減以接收固定的直法 電壓。LED背光源的驅練置包括第—電流鏡、第二電流鏡以及控 制電路’其中第-電流鏡至每個第—燈串第二端，第二電流 鏡麵接至母個第二燈串第二端，控制電路墟至第—電流鏡及第 二電流鏡。第-電流鏡職在致能辭衡每㈣—燈 使3第一燈串電流為零。第二電流鏡用以在致能時L平衡 母個第二燈串電流，在禁麟使每個第二燈串電流為零。控= 2以ίί—期間禁能第二電流鏡且根據調光信號及第一燈串始 時“ 脈寬 及不能，其中第-™信號的責任週期由調光信號及第一燈串ς 201115873 號及第二燈串總 電流所決定，第二PWM信號的責任週期由調光信 電流所決定。 ° 本發明將led f光源分成兩組燈串（一組為第一 為第二燈串）進行分時控制，在每段期間（第一 ^ _ 、、且 =一組_光，因此確每__=1= 的南壓電容器之電容值及其上的電壓漣波，另外可降低 ”作_全載運轉條件下所造成的瞬間電流過大問題3 者，本發明採用簡單的驅動控制方式， 再 控制器的使用數量，控制電路還可採用原轉換器及 …十而不需要專用的LED控制器之設計，可大幅降低成本心之 本發明之上述和其他目的、特徵和優點缺明顯易慯 下文特♦較佳減例，並配合所_式，作詳細說明如下。 【實施方式】 ί S" t r ：： 此堂数1為1〜JD中任一正萃激_ Α τ , 背光源的驅動裝置包括第一電流b'' m任一正整數。led 43以及DC/DC轉換器44。桃兄、一電流鏡42、控制電路 ^ 32j _第二爾至第二電流鏡 201115873 鏡42均_至控制電路43。本領域具有通常知識者應#知道為了 讓這些燈串得以正常工作，每個第一燈串3Π及每個第二燈串抝 中的發光二極體D1陽極端應_至燈串第—端，發光二極體⑽ 陰__接至發光二極體_陽極端，且發光二極體此陰極 端應墟至燈串第二端，其中〖為丨〜(㈣任—正整數。 請參照圖5’其為圖4所示電流鏡41或42的一實施例之電路 圖由於第電流鏡41及第二電流鏡42通常採用相同的電路結 構’在此僅以第-電流鏡41為例進行說明。第一電流鏡41包括 多個匹配的電晶體Qi，，其均為雙载子接面電晶體或場效電晶 體’在本例中電晶體卬〜咖均為場效電晶體。每個電晶體以具 有第鳊（即;及極端）、第二端（即源極端）及控制端（即閉極端）， 每個電晶體Qi第-端雛至相應的第一燈串3Π第二端，這些電 曰曰體Q1〜Qm第二端彼此耦接並耦接至控制電路43，且這些電晶體 Q1〜Qm其中之-電晶體(林例為qj )第一端還_接至控綱而連 接成二極體形式的電晶體(di〇de-connected IransistoiO。 當第一電流鏡41致能(enable)時，電晶體Q1〜Qin會正常動 作，因此在電晶體Q1被觸發後，由於電晶體Q1〜Qm匹配的緣故， 流過電晶體Q1〜Qm的電流I3ii〜I31m會相等或在—定誤差範圍 内’進而使流過每個第-燈串電流I31i達到平衡，故第一燈串311 〜31m發光並提供均勻的亮度。當第一電流鏡41禁能(disable) 時，電晶體Q1〜Qm不會動作，沒有電流流過每個第一燈串3U , 即第-燈串電流I3li均為零’故第一燈串不發光。藉 由控制第一電流鏡41交替地致能及禁能，第一燈串311〜31m將 一下發光（亮）一下不發光（暗）。若亮暗的切換頻率在1〇〇Hz以上， 人眼將因視覺暫留的影響而感覺不到亮暗的變化，只能感覺到這 個變化的平均值，即人眼只能感受到平均亮度且這個平均亮度與 201115873 亮暗的比例成正比。因此，藉_整第—電流鏡41致能及禁能的 時長比例，可調整第-燈串311〜3im亮暗的比例，實現調整LED 背光源亮度的調光效果。 請再參照圖4，控制電路43包括控制器431、第一開關M1、 第二開關M2、第-電流_器Rdl以及第二電流侧器麗。在 本例中’控制器431為-般通用的簡控制器，可以自行設計或 ^用現有如TL494、OZ9938等的清控制晶片，而第一開關M1及Diode's referred to as LED) is used as a backlight. However, due to the increasing global warming phenomenon, countries are becoming more and more strict in the power loss specifications of consumer electronic products, making CCFL backlights gradually replaced by LED backlights due to their large power loss. FIG. 1 is a circuit diagram of a driving device of a conventional LED backlight. Referring to FIG. 1 , the LED backlight includes m light strings 11 〜im, and each light string 1 丨 includes a plurality of light-emitting diodes D1 DDn Dn coupled in series, wherein m and η are positive integers, The number of positive covers in 1~m. The driving device of the led backlight includes a direct current to direct current (dc/dc) converter 21 and an LED controller 22. The DC/DC converter 21 is a step-down or step-up converter 5! for converting a common DC voltage of a standard of 5V, 12V or 24V into a DC voltage Vdc2 of the driving string 11 to lm. The first end of each string is coupled to the DC/DC converter H 21 to receive the dragon required by the money light, and the second end of each string h is coupled to the corresponding channel end of the LED controller 22 Hey. The ^ helper 22 extracts the π current of each light string, and uses the internal current source or the variable electric current mode to make each light string U current equal or in a constant error range _ turn balance 'the light string 11 lm It provides uniform brightness when illuminated. In order to balance the current of the string h and obtain the desired voltage, the LED (four) device 22 can also obtain the pulse width modulation (10) se_Width from the return end FB. Here, for example, ^, to control the DC/DC converter 21 to adjust the output DC voltage. Vdc2 size, ^ 201118873 month light source and LED controller 22 can be operated to optimize. Of course, the LED controller 22 may also not send the PWM signal 'to cause the DC/DC converter 21 to output a constant DC voltage Vdc2' and the LED controller 22 is only used to balance the current of each string. When the number of light strings η~im of the LED backlight is too large or the high-shell light-emitting diodes D1 to Dn having a large current are used, in order to prevent the LED controller 22 from being overheated or burned due to too much current received, it is necessary to adopt The external control method shown in Figure 2. Please refer to FIG. 2, the second end of each string u needs to be added with a corresponding transistor and a resistor Ri, wherein the transistor Qi is a field effect transistor and operates in a linear region to adjust the falling lamp as a variable resistor. The voltage on the string is such that each string U turbulence is balanced. The LED controller 220 detects, from the current detecting terminal ISi, a voltage value which is proportional to the magnitude of the current when the lamp string current flows through the resistor Ri, and according to the voltage value, sends a signal from the channel terminal CHi to control the transistor Qi to change. It is located at the operating point of the linear region to change the size of the variable resistor provided by the transistor Q!. (4) The controller 22Q detects the voltage at the source terminal of the transistor from the voltage terminal VDi, and when the voltage at the source terminal is too high, 'the signal is sent from the channel terminal CHi to control the transistor Qi to be turned off to protect the circuit. In order to obtain a better voltage adjustment, a plurality of dc/dc converters can be used as shown in FIG. 3 to provide a plurality of individually adjustable DC voltages to the string. Referring to FIG. 3 'the first end of each string 11 is switched to the respective DC/DC converter 21i to receive the DC voltage Vdc2i to obtain the required voltage, and the second end of each string π is first stalked to The additional transistor Qi and resistor Ri are then drained to their respective (10) controllers 22i @ which allows for finer manipulation of the (10) backlight drive. No. How to drive the LED xenon light source shown in Figure 1 to Figure 3: The LEDs used must be controlled by H 22, 220 or 221 to 22 m. Moreover, with the LED backlight ΐ = the number of strings U ~ llD, for the LED backlight source shown in Figure 2: said the number of pins of the LED controller 220 and the number of additional transistors Qi and resistors Ri It will increase, making the circuit layout difficult and costly. For the LED backlight driving device shown in Figure 3 of 201115873, where j) C/DC converters 211 ~ 21m, LED controllers 221 ~ 22m and additional Both the number of transistors Qi and the number of resistors Ri will increase. In addition to making the circuit layout difficult and costly, the communication and control between the LED controllers 221 and 22m may be difficult due to the increase in the number of LED controllers. SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a driving device for a light-emitting diode (LED) backlight, which can reduce a power converter (such as a DC/DC converter) by using a simple driving control method. The number of LED controllers used to reduce costs. In order to achieve the above and other objects, the present invention provides a driving device for a light-emitting diode (LED) backlight. The LED backlight comprises a plurality of first light strings and a plurality of driving light strings, each of the first light string and the second light string comprises a plurality of serially connected light emitting diodes, each of the first light strings and the second The first end of the string is subtracted to receive a fixed straight voltage. The driving of the LED backlight comprises a first current mirror, a second current mirror and a control circuit, wherein the first current mirror is connected to the second end of each of the first light strings, and the second current mirror is connected to the second second light string. The second end controls the circuit to the first current mirror and the second current mirror. The first-current mirror is capable of exchanging each (four)-light to make the current of the first string of three zero. The second current mirror is used to balance the two second string currents when enabled, and to make each second string current zero in the forbidden phase. Control = 2 to ίί—the second current mirror is disabled during the period and according to the dimming signal and the first light string “pulse width and not, wherein the duty cycle of the first-TM signal is modulated by the dimming signal and the first light string 201115873 The duty cycle of the second PWM signal is determined by the total current of the second lamp string, and the duty cycle of the second PWM signal is determined by the dimming signal current. ° The present invention divides the LED light source into two sets of light strings (one set is the first second light string) Perform time-sharing control, during each period (first ^ _ , , and = a group of _ light, so the capacitance value of the south voltage capacitor per __ = 1 = and the voltage chopping on it, and can be reduced "The problem of excessive transient current caused by _ full load operation conditions, the present invention uses a simple drive control method, and the number of controllers used, the control circuit can also use the original converter and ... ten without special The above-described and other objects, features and advantages of the present invention are substantially reduced in cost. The following is a description of the present invention. ί S" tr :: This number 1 is 1~JD Any of the positive excitations _ Α τ , the driving device of the backlight includes any positive integer of the first current b′′ m. The LED 43 and the DC/DC converter 44. Tao Xi, a current mirror 42 , a control circuit ^ 32j _ second to second current mirror 201115873 mirror 42 is _ to control circuit 43. Those skilled in the art should know that in order for these strings to work properly, each first string 3 Π and each second lamp The anode end of the LED diode D1 in the string 应 should be _ to the first end of the string, the light emitting diode (10) is connected to the anode end of the light emitting diode, and the cathode end of the light emitting diode should be lighted to the light. The second end of the string, wherein 丨 ( ( ((4) 任 - positive integer. Please refer to FIG. 5 ' is a circuit diagram of an embodiment of the current mirror 41 or 42 shown in FIG. 4 due to the current mirror 41 and the second current mirror 42 The same circuit structure is generally used. Here, only the first current mirror 41 is taken as an example. The first current mirror 41 includes a plurality of matched transistors Qi, which are all bipolar junction transistors or field effect transistors. Crystal 'In this example, the transistor 卬 咖 咖 is a field effect transistor. Each transistor has a third 即 (ie; and extreme), The second end (ie, the source terminal) and the control end (ie, the closed end), each transistor Qi is end-to-end to the corresponding first light string 3Π second end, and the second ends of the electric bodies Q1~Qm are coupled to each other Connected to the control circuit 43, and the first end of the transistors Q1~Qm (the case of the forest is qj) is connected to the control and connected to the transistor in the form of a diode (di〇de) -connected IransistoiO. When the first current mirror 41 is enabled, the transistors Q1~Qin will operate normally. Therefore, after the transistor Q1 is triggered, the transistors Q1~Qm match and flow through the transistor Q1. The currents I3ii to I31m of the ~Qm will be equal or within the range of the constant error, and thus the current through each of the first string currents I31i will be balanced, so that the first strings 311 to 31m emit light and provide uniform brightness. When the first current mirror 41 is disabled, the transistors Q1~Qm do not operate, and no current flows through each of the first string 3U, that is, the first string current I3li is zero, so the first string is Does not shine. By controlling the first current mirror 41 to be alternately enabled and disabled, the first light string 311 to 31m will be illuminated (bright) and not illuminated (dark). If the switching frequency of light and dark is above 1 Hz, the human eye will not feel the change of light and dark due to the influence of persistence of vision. Only the average value of this change can be felt, that is, the human eye can only feel the average brightness. And this average brightness is proportional to the ratio of 201115873 light and dark. Therefore, by using the ratio of the duration of the current-current mirror 41 enabling and disabling, the ratio of the light-darkness of the first light string 311~3im can be adjusted to achieve the dimming effect of adjusting the brightness of the LED backlight. Referring to FIG. 4 again, the control circuit 43 includes a controller 431, a first switch M1, a second switch M2, a first current_current Rd1, and a second current side. In this example, the controller 431 is a general-purpose simple controller, and can design or use existing clear control chips such as TL494, OZ9938, etc., and the first switch M1 and

第二開關M2均為場效電晶體，第—電流偵測器Kdl及第二電流债 測裔Rd2均為電阻器。控制器431具有調光端腿、控制端Gl和 G2及電流_端IS，從調光端麵接收調光信號她，從控制端 G1和G2分別輪出第- pwm信號Vpwml及第二剛信號細心，並 從電流偵測端is偵測第-燈串總電流131及第二燈串總電流132。 、控制器431藉由第-開_及第一電流偵測器肌控制第一 電^鏡41父替地致能及禁能，並藉由第二開關M2及第二電流侦 2 Rd2控制第二電流鏡42交替地致能及禁能。由於第一開關似 第-電流伽器RcU、與第二關M2及第二電流制器㈣通 吊=相同的魏結構，在此僅以第一開關Mi及第一電流偵測器 ‘、、-例進行。兒明。第—開關M1及第一電流债測器灿串聯織 技^電流鏡41及接地端之間，在本例中第一開關Ml第-端輕 魅流鏡41以接收第一燈串總電流131，第一開關M1第二 端祕電流侦測器咖第一端，第—電流_器顏第二 〜t端」其中第—燈串總電流131為第一燈串電流1311 」之〜'和。kDC/DC轉換器44輸出的電流經過第一燈串31卜 電产^ 郷正料通而錢流在其巾流動，第一 机兄、’，、;' 日正常動作，相當於致能第一電流鏡41 ;反之，若 201115873 » 是使此電流迴路斷開而不再有電流在其中流動，第一電流鏡4i必 然不再動作’相當於禁能第一電流鏡41。 因此，控制器431輸出第一 PWM信號VpWmi至第一開關扪抑 制端以控制其交替地開路(open)及閉合(closed)。當第—開關^ ^路時’第一開顧1第一端及第二端彼此未連接，上述電流迴路 開而相當於禁能第一電流鏡41。當第-開關Ml閉合時，第一開 關^第一端及第二端彼此連接，上述電流迴路正常導通而相當ς ，能第-電流鏡4卜另外，控制器431藉由第一電流伯測器田她 、f到第一燈串總電流131大小，並據以調整第-PWM信號! 的貝任週期，此即調整第一開關Ml開路及閉合的時長比例，進而 ，整第—電流鏡41致能及禁能的時長比例，實現調整LED背光源 冗度的調光效果。 ’、 社圖6為圖4所不控制器431於最大亮度需求下之控制時序圖。 -月同時參照圖4及圖6，控制器431由内部振盪器（圖中未繪示） 振盪產生脈衝信號VpUise作為其操作頻率。脈衝信號細以可 ^為，由夕個時長為τ的週騎組成，每個週期包括—個時長為Μ (或稱為脈寬為td)的脈衝，脈衝祕寬td遠小於週躺 另外這些脈衝可用來區隔第-剛信號v_及第二號 V_2以避免波形重叠(overlap)而造成第-燈_ 311〜31m及第 二燈串321〜32m會同時發光。在這裡將奇數個週期稱為第一期間 偶婁文個週期稱為第二期間T2，因此第一間τι及第二期間 T2具有相同的時長T且交替地發生。 ' 第一期間Τ1 ’控制器431輸出的第一 PWM信號Vpwml部份 ^準位、其餘為低準位，第一顺信號Vpwml在高準位時控制 第一開關Ml閉合’致能第-電流鏡41使第一燈串311〜3im發光， 而在低準位時控制第-開關M1 _，禁能第一電流鏡41使第一 201115873 燈串311〜31m不發光，制器431會根據調光信號_及第一 燈串總電流131調整輸出的第-PWM信號¥_的責任週期（其為 Τοη1/2Τ)」以調整第-電流鏡41致能的時長（其即第一蘭j言號 Vpwml在高準位時的時長Tonl)。控制器43丨輸出的第二p刪俨號u V_2怪為低準位，第二PWM錢ν_2在低準位時控制第二^關 M2開路，禁能第二電流鏡42使苐二燈串321〜32m不發光。The second switch M2 is a field effect transistor, and the first current detector Kdl and the second current debt detector Rd2 are resistors. The controller 431 has a dimming end leg, control terminals G1 and G2, and a current_end IS. The dimming signal is received from the dimming end face, and the first-pwm signal Vpwml and the second rigid signal are respectively rotated from the control terminals G1 and G2. Careful, and detecting the first-to-light string current 131 and the second string current 132 from the current detecting terminal is. The controller 431 controls the first electric mirror 41 to enable and disable the ground by the first-on-first and first current detector muscles, and is controlled by the second switch M2 and the second current detector 2 Rd2. The two current mirrors 42 are alternately enabled and disabled. Since the first switch is like the first current collector RcU, the second switch M2, and the second current controller (four) pass the same structure, here only the first switch Mi and the first current detector ', - The example is carried out. Children. The first switch M1 and the first current debt detector can be connected in series with the current mirror 41 and the ground terminal. In this example, the first switch M1 is connected to the first end of the light mirror 41 to receive the first current total current 131. First switch M1 second end secret current detector coffee first end, first - current _ device face second ~ t end" wherein the first - string total current 131 is the first string current 1311" and . The current output by the kDC/DC converter 44 passes through the first light string 31, and the electricity flow is flowing through the towel. The first brother, ',,;' is normally operated, which is equivalent to the enablement. A current mirror 41; conversely, if 201115873 » is to disconnect the current loop and no more current flows therein, the first current mirror 4i must no longer operate 'equivalent to disable the first current mirror 41. Therefore, the controller 431 outputs the first PWM signal VpWmi to the first switch 扪 suppression terminal to control its alternately open and closed. When the first switch and the second end are not connected to each other, the current circuit is opened and the first current mirror 41 is disabled. When the first switch M1 is closed, the first end and the second end of the first switch are connected to each other, and the current loop is normally turned on and is relatively ς, and the first current mirror 4 can be additionally used, and the controller 431 is tested by the first current. Shetian, f to the first lamp string total current size 131, and according to the adjustment of the first - PWM signal! Bayes cycle, which adjusts the first switch Ml open and closed time proportion, and then, the entire first - current The ratio of the length of the enabling and disabling of the mirror 41 enables the dimming effect of adjusting the redundancy of the LED backlight. FIG. 6 is a control timing diagram of the controller 431 of FIG. 4 under the maximum brightness requirement. Referring to FIG. 4 and FIG. 6 simultaneously, the controller 431 is oscillated by an internal oscillator (not shown) to generate a pulse signal VpUise as its operating frequency. The pulse signal is composed of a week-long ride with a period of time τ. Each cycle includes a pulse with a duration of Μ (or a pulse width of td), and the pulse width td is much smaller than the circumference. In addition, these pulses can be used to separate the first-right signal v_ and the second number V_2 to avoid waveform overlap, causing the first lamp_311~31m and the second lamp string 321~32m to emit light at the same time. Here, the odd number of periods is referred to as a first period, and the period of the second period is referred to as a second period T2, so that the first interval τι and the second period T2 have the same duration T and alternately occur. 'First period Τ1' The first PWM signal Vpwml outputted by the controller 431 is partially level, and the rest is low level, and the first forward signal Vpwml controls the first switch M1 to be closed at the high level to enable the first current The mirror 41 causes the first light string 311~3im to emit light, and controls the first switch M1_ at a low level, and disables the first current mirror 41 so that the first 201115873 light string 311~31m does not emit light, and the controller 431 adjusts according to the tone. The optical signal_and the first lamp total current 131 adjusts the duty cycle of the output -PWM signal ¥_ (which is Τοη1/2Τ)" to adjust the duration of the enablement of the first current mirror 41 (which is the first blue j The length of the word Vpwml at the high level is Tonl). The second p-cut number u V_2 outputted by the controller 43丨 is low level, the second PWM money ν_2 controls the second ^M2 open circuit when the low level is low, and the second current mirror 42 is disabled to make the second light string 321~32m does not emit light.

在第二期間T2，控制器431輸出的第一簡信號Vpwml 互為 低準位，第- PWM信號Vpwml在低準位時控制第一開關犯開路， 禁能第-電流鏡41使第-燈串311〜31m不發光。控制器仞 士的第二PWM信號細2部份為高準位、其餘為低準位，第二簡 信號V_2在高準位時控制第二開關M2閉合，致能第二電流鏡犯 =第二燈串321〜32m發光，而在低準位時控制第二開關M2開路， ^能第二電流鏡42使第二燈串321〜32m不發光。控制器側會 ^艮據調光信號Vdim及第二燈串總電流132調整輸出的第二觸作 號Vpwm2的責任週期（其為T〇n2/2T)，以調整第二電流鏡42致 的時長(其即第二PWM信號Vpwra2在高準位時的時長τ〇η2)。 所以，本發明將LED冑光源分成第-燈串311〜31m及第二燈 321〜32m兩組燈串進行分時控制，在第一期間Ή只驅動第一 ，串311〜31m發光而在第二期間T2只驅動第二燈串321〜32 ;而且利用人眼視覺暫留的影響，使人眼並不會感受到在第— ^間τι只有第-燈串311〜31m發光而在第二期間Τ2只有第二燈 =21〜32m發光。藉由調整第—觸信號ν_的責任週期 電机鏡41致能及禁能的時長比例，進而調整第一燈串 亮暗的比例來改變人眼所能感受到第-燈串311〜31m的平 敕=度，同樣地’藉由調整第二簡信號細2时任週期 正弟-電流鏡42致能及禁能的時長比例，賴調整第二燈串& 201115873 〜32m亮暗的比例來改變人眼所能感受到第二燈串321〜32m的平 均亮度。 圖7A及圖7B分別為圖4所示LED背光源之配置圖，在這裡 以LED背光源包括3個第一燈串311〜313及3個第二燈串321〜 323為例。請先照圖7A，其採用侧邊式背光源，故第一燈串 〜313設於液晶面板5的左半側邊，而第二燈串321〜323設於液 晶面板5的右半側邊。請再參照圖7B，其採用直下式背光源，故 第一燈串311〜313設於液晶面板5’的左半面，而第二燈串321〜 323設於液晶面板5’的右半面。但是，led背光源的配置並不僅限 於將第一燈串311〜313設於液晶面板的一半側邊或半面並將第二 燈串321〜323設於液晶面板的另一半側邊或半面，例如還可以將 第一燈串311〜313及第二燈串321〜323彼此交錯設於液晶面板 的側邊或整面。 綜上所述，本發明將led背光源分成兩組燈串（一組為第一燈 串311〜31m ’另一組為第二燈串321〜32m)進行分時控制，在每 段期間（第一期間T1或第二期間T2)只驅動一組燈串發光，因此可 降低每段期間從提供直流電壓Vdc2的電源轉換器44所抽取的電 流，相對地可降低電源轉換器44為穩壓穩流所需的高壓電容器之 電容值及其上的電壓漣波，另外可降低電源轉換器44開始動作瞬 間全载運轉條件下所造成的瞬間電流過大問題。再者，本發明採 用簡單的驅動控制方式，除了可降低電源轉換器及控制器^使用 數量，控制電路43還可採用一般通用的PWM控制器之設計而不需 要專用的LED控制器之設計，可大幅降低成本。 雖然本發明已以較佳實施例揭露如上，然其並非用以限定本 發明，任何熟習此技藝者，在不脫離本發明之精神和範圍内，當 可作些許之更動與潤飾，因此本發明之保護範圍當視後附之申^ 201115873 專利範圍所界定者為準。 【圖式簡單說明】 圖1〜圖3分別為現有的LE：D背光源的驅動裝置之電路圖。 圖4為依照本發明一較佳實施例所繪示之LEj)背光源的驅動 裴置之電路圖。 圖5為圖4所示電流鏡的一實施例之電路圖。 圖6為圖4所示控制器於最大亮度需求下之控制時序圖。 • 圖7A及圖分別為圖4所示LED背光源之配置圖。 【主要元件符號說明】 11〜lm :燈串 21、 211〜21m :直流至直流(DC/DC)轉換器 22、 220、221 〜22m: LED 控制器 CH、CH1〜CHm :通道端 FB :回授控制端 IS、IS1〜ISm ··電流债測端 VD、VD1〜VDm :電壓偵測端 311〜31m ··第一燈串 321〜32m:第二燈串 41 :第一電流鏡 42:第二電流鏡 43:控制電路 13 201115873 431 :控制器 DIM :調光端 Gl、G2 :控制端 IS :電流偵測端 44 :直流至直流(DC/DC)轉換器 5、5’ ：液晶面板 D1〜Dn :發光二極體 Ml :第一開關 M2 :第二開關 Q1〜Qm ·電晶體 R1〜Rm :電阻器 Rdl:第一電流偵測器 Rd2 :第二電流偵測器 Vpulse :脈衝信號In the second period T2, the first simple signal Vpwml outputted by the controller 431 is low level with each other, and the first PWM signal Vpwml controls the first switch to open the circuit when the low level is low, and disables the first current mirror 41 to make the first light. The strings 311 to 31m do not emit light. The second PWM signal of the controller gentleman is a high level and the rest is a low level, and the second simple signal V_2 controls the second switch M2 to be closed at a high level, enabling the second current mirror to commit = The two strings 321 to 32 m emit light, and when the low level controls the second switch M2 to open, the second current mirror 42 prevents the second strings 321 to 32m from emitting light. The controller side adjusts the duty cycle of the second touch number Vpwm2 (which is T〇n2/2T) according to the dimming signal Vdim and the second lamp total current 132 to adjust the second current mirror 42. Duration (which is the duration τ 〇 η 2 when the second PWM signal Vpwra2 is at a high level). Therefore, in the present invention, the LED 胄 light source is divided into two sets of light strings of the first light string 311 ～ 31 m and the second light 321 〜 32 m, and the first time period Ή only drives the first, the string 311 ～ 31 m emits light. During the second period, T2 only drives the second light string 321~32; and the influence of the persistence of the human eye vision is such that the human eye does not feel that only the first light string 311~31m emits light in the second interval. During the period Τ 2 only the second lamp = 21~32m illuminates. By adjusting the ratio of the enabling and disabling time period of the motor cycle 41 of the duty cycle of the first touch signal ν_, and adjusting the ratio of the brightness of the first light string to change the brightness of the first light string, the first light string 311 can be felt by the human eye. 31m flat 敕 = degree, the same as 'by adjusting the second simple signal fine 2 when the cycle is positive - the ratio of the current mirror 42 enable and disable time, depending on the adjustment of the second string & 201115873 ~ 32m bright The dark ratio changes the average brightness of the second light string 321 to 32 m that the human eye can feel. 7A and 7B are respectively a configuration diagram of the LED backlight shown in FIG. 4, where the LED backlight includes three first light strings 311 to 313 and three second light strings 321 to 323 as an example. Please refer to FIG. 7A first, which uses a side-type backlight, so that the first light string 313 is disposed on the left half of the liquid crystal panel 5, and the second light strings 321 323 323 are disposed on the right half of the liquid crystal panel 5. . Referring again to Fig. 7B, which uses a direct type backlight, the first light strings 311 to 313 are disposed on the left half of the liquid crystal panel 5', and the second light strings 321 to 323 are disposed on the right half of the liquid crystal panel 5'. However, the configuration of the LED backlight is not limited to the first light strings 311 313 313 being disposed on one half or half of the liquid crystal panel, and the second light strings 321 321 323 being disposed on the other half or half of the liquid crystal panel, for example, for example. The first light strings 311 to 313 and the second light strings 321 to 323 may be alternately arranged on the side or the entire surface of the liquid crystal panel. In summary, the present invention divides the LED backlight into two sets of light strings (one set is the first light string 311~31m 'the other set is the second light string 321~32m) for time-sharing control during each period ( The first period T1 or the second period T2) only drives a group of light strings to emit light, so that the current drawn from the power converter 44 that supplies the DC voltage Vdc2 during each period can be reduced, and the power converter 44 can be relatively reduced. The capacitance value of the high-voltage capacitor required for steady current flow and the voltage chopping thereon can also reduce the problem of excessive transient current caused by the full-load operation condition of the power converter 44 at the moment of starting operation. Furthermore, the present invention employs a simple drive control method. In addition to reducing the number of power converters and controllers used, the control circuit 43 can also adopt a general-purpose PWM controller design without the need for a dedicated LED controller design. Can significantly reduce costs. While the present invention has been described in its preferred embodiments, the present invention is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 to FIG. 3 are circuit diagrams of a driving device of a conventional LE:D backlight, respectively. 4 is a circuit diagram of a driving device of a LEj) backlight according to a preferred embodiment of the present invention. Figure 5 is a circuit diagram of an embodiment of the current mirror of Figure 4. Figure 6 is a timing diagram of the control of the controller of Figure 4 under maximum brightness requirements. • Fig. 7A and Fig. 7 are configuration diagrams of the LED backlight shown in Fig. 4, respectively. [Description of main component symbols] 11~lm: Light string 21, 211~21m: DC to DC converter 22, 220, 221 to 22m: LED controller CH, CH1~CHm: Channel end FB: Back Control terminal IS, IS1~ISm · Current debt measuring terminal VD, VD1 VVDm: voltage detecting terminal 311~31m ··first light string 321~32m: second light string 41: first current mirror 42: Two current mirror 43: control circuit 13 201115873 431: controller DIM: dimming terminal Gl, G2: control terminal IS: current detecting terminal 44: direct current to direct current (DC/DC) converter 5, 5': liquid crystal panel D1 ~Dn: Light-emitting diode M1: First switch M2: Second switch Q1~Qm · Transistor R1~Rm: Resistor Rdl: First current detector Rd2: Second current detector Vpulse: Pulse signal

Vdcl、Vdc2、Vdc21 〜Vdc2m :直流電壓 Vdim :調光信號Vdcl, Vdc2, Vdc21 ~ Vdc2m : DC voltage Vdim : Dimming signal

Vp丽1 :第一脈寬調變(PWM)信號 Vpwm2 :第二脈寬調變(PWM)信號 131 :第一燈串總電流 1311〜I31m :第一燈串電流 201115873 132 :第二燈串總電流 1321〜I32m:第二燈串電流 T:週期的時長 T1 :第一期間 T2 :第二期間Vp 丽1: first pulse width modulation (PWM) signal Vpwm2: second pulse width modulation (PWM) signal 131: first lamp string total current 1311~I31m: first string current 201115873 132: second string Total current 1321~I32m: second string current T: period duration T1: first period T2: second period

Td :脈衝的時長（或脈寬）Td : duration of the pulse (or pulse width)

Toni :第一脈寬調變(PWM)信號致能的時長 • Ton2 :第二脈寬調變(PWM)信號致能的時長Toni: The duration of the first pulse width modulation (PWM) signal enable • Ton2 : the duration of the second pulse width modulation (PWM) signal enable

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Claims (1)

201115873 &'申請專利範圍： 發光二極體背光源的驅動裝置，該發光二極體背光源包括 =第-燈串及多個第二燈串’每個第―燈串及第二燈串均包 1夕個串聯輕接的發光二極體，每個第—燈串及第二燈串第一 ^均輕接以接收-固定的直流電壓，該驅動裝置包括： 第—電流鏡’輕接至每個第-燈串第二端，在致能時平衡每 個第-燈串電流’在禁能時使每_—燈串電流為零； 第二電流鏡，祕至每個第二燈串第二端，在致能時平衡每 固第二燈串電流’在禁能時使每個第二燈串電流為零；以及 控制電路，接至該第-電流鏡及該第二電流鏡，在一第一 期間禁此該第二電流鏡且根據_調光信號及該些第一燈串 總電流調魏第-電流鏡致能的時長，在―第二期間禁能該 f電流鏡且根據該調光信號及該些第二燈串總電流調整 该第二電流鏡致賴時長，料-朗及該第二綱具有相 同的時長且交替地發生。 '、 •如申睛專利範圍帛1項所述之發光二極體背光源的驅動裝置， 其中該第-電流鏡包婦魅_電晶體，每個電晶體具有一 第—，、一第二端及一控制端’每個電晶體第—端#接至一相 應的第-燈串第二端’該些電晶體第二端彼此減並輕接至該 控制電路，該些電晶體控制端彼此耦接，該些電晶體其中之一 電晶體第一端更搞接至控制端。 3.如申請專利範目第丨項所述之發光二極體背光源的驅動褒置， 其+該第二電流鏡包括多個匹配的電晶體，每個電晶體具有一 第一端、一第二端及一控制端，每個電晶體第一端耦接至一相 201115873 SI:燈:’該些電晶體第二端彼此耦接並耦接至該 +曰^# 電晶體控制端彼此耦接，該些電晶體其中之一 电日曰體第-端更耦接至控制端。 苴由·^概圍第1項所述之發光二極體背統的驅動裝置， 制電路輸出一第—脈寬調變信號及一第二脈寬調變 二馳㈣H錢及該第二電流鏡的致能及禁 ΪΙ^Ι鄉—脈寬機信號的責任週齡該調光信號及該些201115873 & 'Patent scope: A driving device for a light-emitting diode backlight, the light-emitting diode backlight includes a =-light string and a plurality of second light strings 'each of the first light string and the second light string Each of the first light string and the second light string are lightly connected to receive a fixed DC voltage, and the driving device comprises: a first current mirror Connected to the second end of each of the first string, balance each of the first string currents when enabled - to make each _-string current zero when disabled; the second current mirror, secret to each second The second end of the string, when energized, balances the current of each second string, 'each second string current is zero when disabled; and the control circuit is coupled to the first current mirror and the second current Mirroring, the second current mirror is disabled during a first period, and the duration of the Wei-current mirror enable is adjusted according to the _ dimming signal and the total current of the first light strings, and the f is disabled during the second period The current mirror adjusts the duration of the second current mirror according to the dimming signal and the total current of the second light strings, and the second axis has At the same length and alternately occur. The driving device of the backlight of the light-emitting diode according to claim 1, wherein the first current mirror comprises a transistor, each transistor has a first, a second And a control terminal 'each transistor first end # is connected to a corresponding second light string second end'. The second ends of the transistors are subtracted from each other and lightly connected to the control circuit, and the transistor control terminals Coupling with each other, one of the transistors has a first end of the transistor that is connected to the control end. 3. The driving device of the LED backlight of claim 2, wherein the second current mirror comprises a plurality of matching transistors, each transistor having a first end, a a second end and a control end, the first end of each transistor is coupled to a phase 201115873 SI: a lamp: 'the second ends of the transistors are coupled to each other and coupled to the + 曰 ^ # transistor control end of each other The first end of the plurality of electric cells is further coupled to the control end.苴 · · ^ ^ 概 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第 第Mirror's enablement and imprisonment ^Ι乡-pulse width machine signal responsibility Zhou Ling the dimming signal and these ί上ΐ總電流所決定，該第二脈寬調變信號的責任週期由該 、5號及該些第二燈串總電流所決定。 5· tl %專她11第4項所述之發光二極體背光源的驅動裝置， 其中該控制電路包括： f開關及帛一電流谓測器串聯麵接於該第一電流鏡及 ，地端之間’該第—關根據該第—脈寬調魏號開路及 二口，，，路時禁能該第—電流鏡，在閉合時致能該第一電 Μ鏡’辟-電流伽指偵_些第—燈串總電流； 一，二開關及一第二電流偵測器串聯耦接於該第二電流鏡及 口亥接地端之間’該第二開關根據該第二脈寬讀信號開路及 閉合’在開路啦驗第二電流鏡，在閉合喊能該第二電 流鏡’該第二電流偵測器偵測該些第二燈串總電流；以及 一控制器’肋輸出娜—脈寬婦健及該第二脈寬調變信 J，並，據綱光信號及該些第—燈串總電流罐該第一脈 I調邊彳5_責任棚’及根據該調光信號些第二燈串 總電流調整該第二脈寬調變信號的責任週期。 6.如申凊專他圍第5項所述之發光二極體背光源的驅動裝置， 其中δ亥控制器為一脈寬調變控制器。 17The duty cycle of the second pulse width modulation signal is determined by the total current of the second pulse width modulation signal. 5· tl % The driving device for the backlight of the light-emitting diode according to the fourth item, wherein the control circuit comprises: an f-switch and a current-current detector connected in series to the first current mirror and ground Between the ends of the 'the first-off according to the first-pulse width adjustment Wei open circuit and two,, the road is disabled when the first - current mirror, when closed, the first electric ' mirror - open - current gamma Detecting _ some of the total current of the light string; one, two switches and a second current detector are coupled in series between the second current mirror and the grounding ground of the mouth. The second switch is according to the second pulse width The read signal is open and closed 'in the open circuit, the second current mirror is turned on, and the second current mirror is turned on, the second current detector detects the total current of the second light string; and a controller' rib output娜-脉宽妇健 and the second pulse width modulation letter J, and according to the main light signal and the first-light string total current tank, the first pulse I adjust the edge _ 5_ responsibility shed' and according to the tone The second signal string total current of the optical signal adjusts the duty cycle of the second pulse width modulation signal. 6. A driving device for a backlight of a light-emitting diode according to item 5, wherein the δ hai controller is a pulse width modulation controller. 17