201208490 六、發明說明： 【發明所屬之技術領域】 尤指一種具有短路 本發明有關於一種發光二極體驅動電路 保護功能的發光二極體驅動電路。 【先前技術】 現今的液晶顯示產品已逐漸開始使用由發光二極體所組成之 光源作為背光光源。請參閱第1圖，第1_-種現有的發光二 極體驅動電路H)的電關。發光二極體驅誠路1()伽以驅動 複數個發光二極體燈串22，其中每—發光二極體燈串22均包含複 數個串聯雛的發光二極體26。複數個發光二極體燈串22所組成 之光源可顧於作為液晶顯示產品的背光光源。每—發光二極體 燈串22分別具有_輸人端221以及-輸出端223，所有發光二極 體燈串22的輸入端221均輕接一直流至直流(DC/DC)轉換器24輸 出的-直流電壓。發光二極體驅動電路1G可偵測複數個發光二極 體燈串22是否有短路，並在侧到任—發光二㈣料22發生 ，路時關所有發光二频料22 ’娜護發光二鋪驅動電路 〇及發生過娜的發光二_燈串22 _電子元件不被繼續損 壞’以減少液晶顯示產品安全隱患問題。 發光一極體驅動電路1Q包含—開關控制電路13、複數個定電 流電路14與-短路保護電路15。每一定電流電路14麵接於一相 對應發光二極體燈串22的輸出端223與一地端16之間，短路保 護電路15輕接於每-發光二極體燈串22的輸出端挪，開關控制 電路13搞接於每-定電流電路14與短路保護電路15之間。開關 控制電路13還減於-主板電路12以接收—調光控制信號跑 和-開關控制信號On/Off ’調光控制信號Dim用於控制全部發光 201208490 的亮度，開_信號Qn/Qff用_㈣發光 一極體燈串22的開啟與關閉。 utT^ 143 二跡Μ 9«^ 一 141與檢電143㈣減於相對應發光 在定雷:雷攸的輸出端223與地端16之間’回饋電路145用以 的電流:檢測====應發光二極體燈串22 制流過電晶體141的電t =^_職輸出一信號來控 相斜廄热本^電机(在本例中為及_源極電流)大小，以達到 、f叙伽:5體燈串22的定電流控制。短路保護電路巧包含 ;53，其一中m 一穩壓二極體152與-短路信號產生電路 體151、八別^垃~極體152又稱為齊納（Zener)二極體。每一二極 數個-。Τ5，Γ相對應發光二極體燈串22之輸出端223，複 之電免複數個發光二極體燈串22的輸出端223 信號產生 當複數個發光二極體燈串22有至少一 潰!超過一預定竭，穩壓二極體則 時’短路電路153輸入端電_到一預設電麼 野短路仏號產生電路153内部電晶體導 電路153輸出端將輸出一低準位信號(相當於輸出 從主板電路12輸出的開關控制信號〇n/〇f 〇n/0ff 13 關11截止’使得直流電麼Vcc不再供電到所 =控， 此所有定電流電路14不工作， /ML ， 此時液晶顯示產品將無法顯ut關閉所有發先二極趙燈串22， 201208490 這樣的液晶顯示產品可能會產生如下問題：第一，當人們在 使用液晶彩電觀看精彩節目時或在使用多媒體液晶顯示器開會或 學習時，突然因液晶面板中發光二極體燈串中的發光二極體短路 而造成短路保護電路動作而使整個液晶面板畫面不亮，可能會導 致使用者對這樣的液晶顯示產品產生較大的抱怨。第二，由於液 晶面板出現故障通常無法在液晶顯示產品設計廠家做維修，而通 常要送到液晶面板原廠去做維修，而有些液晶面板產地在國外， ，而就會造成維修週期很長，若超過保修期則使用者需要花費較 高的維修費，這些讓使用者無法接受。 【發明内容】 本發明的目的在於提出一種發光二極體驅動電路，用來偵測 複數個發光二極體料各自是否有娜，且可依據制結果僅關 閉發生短路的發光二極體燈串，因此液晶顯示產品仍可顯示畫面 (雖然其畫面亮度可能有所下降或不是很均勻）。 本發明提出一種用於驅動複數個發光二極體燈串的發光二極 f驅，電路’其包含複數個定電流電路與複數個短路保護電路。 每個定電流電路之-電晶體與—檢測電阻串翻接於—相對應發 光二f體燈串之-輸出端與-地端之間，且在定電流電路正；： 作寺母個又電流電路之一回饋電路通過比較一參考電壓與該檢測 電阻上產生的-檢測縣以輸出_信號控制流過該電晶體的電流 大小，以達到相對應發光二極體燈串的定電流控希卜此外，每個 短路，護電路_於—相對應發光二極體燈串之—輸出端與一相 對應定電流電路’用以於軸對應發光二極體燈串有至少一發光 $體發生短路導致其輸出端雜達到—預定賴且#短路保護 電路内部的短路信號產生電路輸入端電麼達到-預設電廢時，輸 出短路域使該相對應定電流電路之該電晶體截止，以關閉該 201208490 相對應發光二極體料，且_可鱗其他未發生短 極體燈串正常工作。 赞尤一 為讓本發明之上述和其他目的、特徵和優點能更明顯易懂， 下文特舉較佳實施例，並配合所關式，作詳細說明如下。 【實施方式】201208490 VI. Description of the invention: [Technical field to which the invention pertains] In particular, a short circuit of the invention relates to a light-emitting diode driving circuit for a protection function of a light-emitting diode driving circuit. [Prior Art] Today's liquid crystal display products have gradually begun to use a light source composed of a light-emitting diode as a backlight source. Please refer to Fig. 1, the electrical switching of the first light-emitting diode driving circuit H). The light-emitting diode drive road 1 () gamma drives a plurality of light-emitting diode strings 22, wherein each of the light-emitting diode strings 22 includes a plurality of light-emitting diodes 26 connected in series. A light source composed of a plurality of light-emitting diode strings 22 can be used as a backlight source of a liquid crystal display product. Each of the light-emitting diode strings 22 has an _ input terminal 221 and an output terminal 223, and the input terminals 221 of all the LED strings 22 are lightly connected to the DC (DC/DC) converter 24 output. - DC voltage. The LED driving circuit 1G can detect whether a plurality of LED strings 22 are short-circuited, and occurs in the side-to-light-emitting two (four) material 22, and all the light-emitting two-frequency materials 22 are closed on the road. The driving circuit and the illuminating light _ string 22 _ electronic components are not continuously damaged to reduce the safety hazard of the liquid crystal display product. The light-emitting one-pole driving circuit 1Q includes a switch control circuit 13, a plurality of constant current circuits 14 and a short-circuit protection circuit 15. Each of the constant current circuits 14 is connected between the output end 223 of a corresponding LED string 22 and a ground end 16, and the short circuit protection circuit 15 is lightly connected to the output end of each of the LED strings 22 The switch control circuit 13 is connected between each of the constant current circuit 14 and the short circuit protection circuit 15. The switch control circuit 13 is also subtracted from the - mainboard circuit 12 to receive - dimming control signal running and - switching control signal On / Off ' dimming control signal Dim is used to control the brightness of all illumination 201208490, open_signal Qn / Qff _ (4) Opening and closing of the light-emitting polar light string 22. utT^ 143 Two traces « 9 «^ 141 and check 143 (four) minus the corresponding illuminating in the fixed lightning: between the output 223 of the Thunder and the ground 16 'current used by the feedback circuit 145: detection ==== The light-emitting diode string 22 should be passed through the transistor 141. The electric output of the transistor 141 is a signal to control the phase of the heat motor (in this case, the source current). , f-Symbol: Constant current control of the 5-body light string 22. The short-circuit protection circuit comprises: 53, a m-regulator diode 152 and a short-circuit signal generating circuit body 151, and an eight-pole electrode 152, which is also called a Zener diode. Each of the two poles -. Τ5, Γ corresponds to the output end 223 of the LED string 22, and the output 223 signal of the plurality of LED strings 22 is generated when at least one of the plurality of LED strings 22 is broken. More than one predetermined exhaustion, the voltage regulator diode is then 'short circuit 153 input terminal _ to a preset power field short circuit nickname generation circuit 153 internal transistor conduction circuit 153 output will output a low level signal ( Equivalent to the output of the switch control signal 〇n / 〇f 〇 n / 0ff 13 output from the main board circuit 12 off 11 off 'so that the DC power Vcc is no longer powered to the = control, all the constant current circuit 14 does not work, / ML, At this time, the liquid crystal display product will not be able to turn off all the first two-pole Zhao light string 22, 201208490 Such liquid crystal display products may have the following problems: First, when people use the LCD color TV to watch the wonderful programs or use multimedia LCD When the display is in a meeting or learning, the short circuit protection circuit is caused by the short circuit of the light-emitting diode in the light-emitting diode string in the liquid crystal panel, so that the entire liquid crystal panel screen is not bright, which may cause the user to Such liquid crystal display products generate large complaints. Second, due to the failure of the liquid crystal panel, it is usually impossible to repair the liquid crystal display product design manufacturer, but usually sent to the original LCD panel for repair, and some LCD panels are produced in the country. In addition, the maintenance cycle is long, and if the warranty period is exceeded, the user needs to pay a high maintenance fee, which is unacceptable to the user. SUMMARY OF THE INVENTION The object of the present invention is to provide a light-emitting diode drive. The circuit is configured to detect whether a plurality of light-emitting diode materials have a respective color, and only the short-circuiting light-emitting diode light string can be turned off according to the result, so the liquid crystal display product can still display a picture (although the brightness of the screen may be The invention is directed to a light-emitting two-pole f-drive for driving a plurality of light-emitting diode strings, the circuit comprising a plurality of constant current circuits and a plurality of short-circuit protection circuits. The circuit-transistor and the sense resistor string are connected to each other - corresponding to the light-emitting body of the f-light string - between the output end and the ground end, and The flow circuit is positive;: one of the mother circuit and the current circuit is fed back to the circuit by comparing a reference voltage with the detection resistance generated by the detection resistor to control the current flowing through the transistor to achieve the corresponding illumination In addition, each short circuit, the protection circuit _ in the corresponding light-emitting diode string - the output end and a corresponding constant current circuit 'for the axis corresponding to the light-emitting diode The body light string has at least one light-emitting body, and the short-circuit signal is generated at the output end of the short-circuit protection circuit. When the short-circuit signal is generated at the input end of the circuit, the output short-circuit field makes the corresponding corresponding The transistor of the constant current circuit is turned off to turn off the 201208490 corresponding light-emitting diode material, and the other short-pole light string does not normally work. The above and other objects, features, and advantages of the present invention will become more apparent and understood. [Embodiment]
清參閱第2 H ’第2圖為本發明之發光二極體驅動電路2〇的 較佳實施例的電路圖。-般來說，發光二極體驅動電路2Q可應用 於使用由發光二極體所組成之光源作騎光光源的液晶顯^產 品。發光二極體鷄電路20用以驅動由複數個料二極體燈串四 所組成之絲，其巾每-發光二極體燈串22均包含複數個串聯輛 接的發光二極體26。每個發光二極體燈串22分別具有-輸入端 221以及一輸出端223，所有發光二極體燈串22的輸入端221均 耦接一直流至直流(DC/DC)轉換器24輸出的一直流電壓。 發光二極體驅動電路20包含有複數個定電流電路28，其中每 個定電流電路28包含-電晶體30、-檢測電阻32及-回饋電路 34。電晶體30與檢測電阻32串聯耗接於—相對應發光二極體燈 串22之輸出端223與-地端之間，且在定電流電路28正常工作 時回饋電路34通過味-參考縣(Vref，將料3圖有進一步 描述)與檢測電阻32上產生的一檢測電壓Vdet輸出一信號，藉以 控制流過電晶體30的電流(在糊巾為汲_雜電流)大小，以達 到相對應發光-極體燈φ 22的定電流控制。發光二極體驅動電路 20另包含有複數個短路保護電路36，每個短路保護電路祁包含 有一穩壓二極體38及一短路信號產生電路4〇。穩壓二極體38耦 接於相對應發光二極體燈串22之輸出端223與短路信號產生電路 40之間，且短路彳§號產生電路4〇耦接於穩壓二極體洲與相對應 201208490 疋，流電路28之間。短路倾電路36用以於相對應發光二極體 =22之輸出端223之電壓達到-預定時，藉由其穩壓二極 體38的崩潰且當短路保護電路36内部的短路信號產生電路 入端電壓達到-預設電壓時，經由短路信號產生電路4〇輸出一短 路信號，藉以使相對應定電流電路28之電晶體3G截止，進 閉相對應發光二極體燈争22以達到保護作用。 請參閱第3圖’第3圖為進-步說明第2圖所示定電流電路 28及短路保護電路36的電路圖。首先，針對定電流電路跗進一 步說明，定電流電路28之電晶體30具有一第一端3〇卜一第二端 3〇2及一控制端303。檢測電阻32具有—第一端321及一第二端# 322。回饋電路34可包含一並聯穩壓器犯，其具有一陽極端421、 :陰極端422及一參考端423。並聯穩壓器42例如是TU31積體 電路’其内部電路示意圖如晒示包含—誤差放A|| 58、 電壓源60及-電晶體62，其中誤差放大器58具有一正輸入端 、一負輸入端582及-輸出端583 ’電晶體62具有一第一端 62卜一一山第二端622及一控制端623。其輕接關係如下，電晶體3〇 f第一端301耗接於相對應發光二極體燈串四之輸出端挪，電 口?30之第二端302耗接於檢測電p且32之第-端321與並聯穩⑩ ，器42之參考端423，檢測電阻32之第二端322麵接於該地端: 並聯穩壓器42之陰極端422搞接於電晶體3〇之控制端3〇3，且並 ，穩麗器42之陽極端421耦接於該地端。其中電晶體3〇係可為 N型金氧半場效電晶體。誤差放大器58的正輸入端測耗接於 於=壓器42的參考端423 ’誤差放大器沾的負輸入端嫩輕接 ^考電壓源60輸出的參考電壓Vref，誤差放大器58的輪出端 3耗接於電晶體62的控制端623，電晶體62的第一端621耦 於並聯穩壓器42的陰極端422，電晶體62的第二端622輕接於並 8 ⑧ 201208490 聯穩壓器42的陽極端421。在定 =5:通過並聯麵器42的 :=時2 :3 ==:’再藉由比較其内部提供的參 (在本例中為流過電晶體62的電流 糊概伽概_體的控制 ㈣大小’《達到相對應發光二極體=:==-_2 is a circuit diagram of a preferred embodiment of the light-emitting diode driving circuit 2 of the present invention. In general, the light-emitting diode driving circuit 2Q can be applied to a liquid crystal display product using a light source composed of a light-emitting diode as a light source. The LED circuit 20 is used to drive a wire composed of a plurality of material diode strings 40, and each of the light-emitting diode strings 22 includes a plurality of LEDs 26 connected in series. Each of the LED strings 22 has an input terminal 221 and an output terminal 223. The input terminals 221 of all the LED strings 22 are coupled to the output of the DC/DC converter 24. A DC voltage. The LED driving circuit 20 includes a plurality of constant current circuits 28, wherein each of the constant current circuits 28 includes a transistor 30, a detecting resistor 32, and a feedback circuit 34. The transistor 30 and the detecting resistor 32 are connected in series between the output terminal 223 and the ground terminal of the corresponding LED string 22, and the feedback circuit 34 passes through the flavor-reference county when the constant current circuit 28 operates normally. Vref, which is further described in FIG. 3, outputs a signal with a detection voltage Vdet generated on the detecting resistor 32, thereby controlling the current flowing through the transistor 30 (in the case of a paste), to achieve a corresponding value. Constant current control of the illuminating-polar body lamp φ 22. The LED driving circuit 20 further includes a plurality of short circuit protection circuits 36, each of which includes a voltage stabilizing diode 38 and a short circuit signal generating circuit 4'. The voltage stabilizing diode 38 is coupled between the output end 223 of the corresponding LED string 22 and the short circuit signal generating circuit 40, and the short circuit 产生 产生 generating circuit 4 〇 is coupled to the Zener diode and Corresponding to 201208490 疋, between stream circuits 28. The short circuiting circuit 36 is configured to generate a circuit when the voltage of the output terminal 223 of the corresponding light-emitting diode=22 reaches a predetermined state by the collapse of the voltage stabilizing diode 38 and the short-circuit signal inside the short-circuit protection circuit 36. When the terminal voltage reaches the preset voltage, the short circuit signal generating circuit 4 outputs a short circuit signal, so that the transistor 3G corresponding to the constant current circuit 28 is turned off, and the corresponding light emitting diode lamp competes for 22 to achieve protection. . Referring to Fig. 3, Fig. 3 is a circuit diagram showing the constant current circuit 28 and the short circuit protection circuit 36 shown in Fig. 2 in the second step. First, for the constant current circuit, the transistor 30 of the constant current circuit 28 has a first terminal 3, a second terminal 3〇2, and a control terminal 303. The detecting resistor 32 has a first end 321 and a second end # 322. The feedback circuit 34 can include a shunt regulator having an anode terminal 421, a cathode terminal 422, and a reference terminal 423. The shunt regulator 42 is, for example, a TU31 integrated circuit'. The internal circuit diagram includes an error-distributed A|| 58 , a voltage source 60 and a transistor 62 , wherein the error amplifier 58 has a positive input terminal and a negative input terminal. The end 582 and the output end 583 'the transistor 62 have a first end 62, a second end 622, and a control end 623. The light connection relationship is as follows. The first end 301 of the transistor 3〇f is consumed by the output end of the corresponding LED string 4, and the second end 302 of the electric port 30 is consumed by the detection circuit p and 32. The first end 321 and the parallel stable 10, the reference end 423 of the device 42, the second end 322 of the detecting resistor 32 is connected to the ground end: the cathode end 422 of the shunt regulator 42 is connected to the control end of the transistor 3〇 3〇3, and the anode end 421 of the stabilizer 42 is coupled to the ground end. The transistor 3 lanthanide can be an N-type gold oxide half field effect transistor. The positive input terminal of the error amplifier 58 is connected to the reference terminal 423 of the voltage regulator 42. The negative input terminal of the error amplifier is connected to the reference voltage Vref outputted by the voltage source 60, and the wheel terminal 3 of the error amplifier 58 is connected. The first end 621 of the transistor 62 is coupled to the cathode end 422 of the shunt regulator 42 , and the second end 622 of the transistor 62 is lightly connected to the 8 8 201208490 voltage regulator. The anode end 421 of 42. At deg=5: through the == 2:3 ==:' of the shunter 42 and then by comparing the internally supplied parameters (in this case, the current flowing through the transistor 62) Control (four) size 'to reach the corresponding light-emitting diode =:==-_
再者，針對短路保護電路36進一步 之:路信號產生電路4〇包含有—第, -電容48及-開㈣。穩壓二極體38具有m 46、 極端382。第一電阻44具有一第 ^極& 381及一陰 電阻46具有Lm:端則容H 442第第ς 如及一第二端482 β開關5〇具有一第一端48 ^一第一端 及-控制端503。其中開關50係可為一半導 第二端502 型雙載子接面f雜。其_柯，懸二 382輕接於相對應發光二極體燈_ 22之輸出端如 := 38之陽極端381輕接於第一電阻44之第一端44ι，且第體 之第二端442耦接於開關5〇之控制端5〇3、電容48 # 與第二電阻46之第—端461。此外，„ 5Q之第 電容48之第二端482、第二電阻46之第二端462與該地端， 關50之第一端501耦接於相對應定電流電路28之電曰 : 制端303。 曰曰菔㈨之控 除此之外，發光二極體驅動電路20另可包含一開關控 52。開關控制電路52耦接於一開關56之控制端563，開關邡 第一端561耦接於一直流電壓vcc，開關56之第二端5兕通 電阻64耦接於複數個定電流電路28的422端和3〇3端，=一 201208490 控制電路52還輕接於一主板電路54，其中開關56係可為一, 型雙載子接面電晶體。當開關控制電路52控制開關56導通時， 直μ電壓Vcc通過一電阻64提供偏壓通過422端給並聯穩壓器42 及通過303端給電晶體30，使得定電流電路28得以正常^作。主 板電路54輸出-開關控制信號〇n/〇ff和用於突發模式⑸故 mode)調光的一調光控制信號Dim給開關控制電路於，其中開關控 制信號Οη/Off和調光控制信號Dim的關係及作用是：第一當^ 主板電路Μ輸出的_控繼號〇禮f為高準位信號輸入二開 關控制電路52時且當從主板電路54輸出的調光控制信號脇輸 入到開關控制電路52時’開關控制電路52根據調光控制信號Dim 的責任週期（duty cycle)來控制開關56的導通時間與關斷睹間的 比例，以控制相對應發光二極體燈串22正常工作時間與關閉時間 的比例，進而控制相對應發光二極體燈串22提供液晶面板畫面的 平均亮度。第二，當從主板電路54輸出的開關控制信號〇n/〇ff 為低準位信號輸入到開關控制電路52時，無論是否有無調光控制 信號Dim輸入到開關控制電路52，開關56都將關斷。 需要說明的是，假設每一燈串22由n個發光二極體26按順 序串聯組成(η為大於1的整數）’每一發光二極體26正向導通電 壓為Vf，因此每一燈串22的輸入端221電壓V221和輸出端223 電壓V223關係為：V223=V221-nxVf。此外，在電晶體3〇導通正 常工作時，相對應燈串22中的每一發光二極體26導通電壓例如 約為Vf=3. 0V〜3. 2V ’而在電晶體30截止時，相對應燈串22中的 每一發光二極體26存在例如約為Vf=2. 〇v~2. 4V的臨界崩潰導通 電壓。當這些燈串22當中的第i個燈串有m個發光二極體出現短 路時(m為大於或等於1的整數）’第i個燈串輸出端電壓為 V223=V221-(n_m)xVf，即第i個燈串輸出端電壓上升且上升的電 201208490 壓為mxVf ’短路保護電路36偵測的是燈_輸出端223最大值電 壓，而由於電晶體30截止時其對應的發光二極體正向電壓Further, for the short circuit protection circuit 36, the path signal generating circuit 4A includes -, -, and - (48) capacitors. The voltage stabilizing diode 38 has m 46 and an extreme 382. The first resistor 44 has a first pole & 381 and a cathode resistor 46 having Lm: the end is H 442 and the second end 482. The switch 5 has a first end 48 ^ a first end And - control terminal 503. The switch 50 can be a half-conducting second-end 502 type double-carrier junction. The _ ke, the suspension 382 is lightly connected to the output end of the corresponding illuminating diode lamp _ 22, such as: the anode end 381 of the 38 is lightly connected to the first end 44 of the first resistor 44, and the second end of the first body The 442 is coupled to the control terminal 5〇3 of the switch 5〇, the capacitor 48# and the first terminal 461 of the second resistor 46. In addition, the second end 482 of the capacitor 48 of the 5Q, the second end 462 of the second resistor 46, and the ground end, the first end 501 of the switch 50 is coupled to the corresponding constant current circuit 28: In addition, the LED driver circuit 20 can further include a switch control 52. The switch control circuit 52 is coupled to the control terminal 563 of a switch 56, and the switch 邡 first end 561 is coupled. The second end 5 of the switch 56 is coupled to the 422 terminal and the 3〇3 terminal of the plurality of constant current circuits 28, and the control circuit 52 is also connected to a mainboard circuit 54. The switch 56 can be a type, double-carrier junction transistor. When the switch control circuit 52 controls the switch 56 to be turned on, the straight μ voltage Vcc is biased through a resistor 64 through the 422 terminal to the shunt regulator 42 and through The 303 terminal is supplied to the transistor 30, so that the constant current circuit 28 can be normally operated. The mainboard circuit 54 outputs a switch control signal 〇n/〇ff and a dimming control signal Dim for burst mode (5) mode dimming to the switch. a control circuit in which a relationship between the switch control signal Οη/Off and the dimming control signal Dim The function is: when the main circuit circuit Μ output _ control relay number f is a high level signal input to the two switch control circuit 52 and when the dimming control signal output from the main circuit circuit 54 is input to the switch control circuit 52 The switch control circuit 52 controls the ratio of the on-time of the switch 56 to the turn-off time according to the duty cycle of the dimming control signal Dim to control the normal operating time and off of the corresponding LED string 22 The ratio of time, in turn, controls the corresponding luminance of the picture of the liquid crystal panel provided by the corresponding LED string 22. Second, when the switch control signal 〇n/〇ff outputted from the main board circuit 54 is a low level signal input to the switch control In the case of the circuit 52, the switch 56 is turned off regardless of whether or not the dimming control signal Dim is input to the switch control circuit 52. It is to be noted that each of the lamp strings 22 is composed of n light-emitting diodes 26 in series in sequence ( η is an integer greater than 1) 'the forward voltage of each of the light-emitting diodes 26 is Vf, so the voltage of the input terminal 221 of each string 22 and the voltage of the output terminal 223 are V223: V223=V221-nxVf. When the transistor 3 is turned on, the on-voltage of each of the corresponding light-emitting diodes 26 is, for example, about Vf=3.0 V~3. 2V ', and when the transistor 30 is turned off, correspondingly Each of the light-emitting diodes 26 has a critical collapse conduction voltage of, for example, about Vf=2. 〇v~2. 4V. When the ith light string among the light strings 22 has m light-emitting diodes When the body is short-circuited (m is an integer greater than or equal to 1), the voltage at the output of the i-th string is V223=V221-(n_m)xVf, that is, the voltage at the output of the i-th string is increased and the voltage of the rise is 201208490. The mxVf 'short circuit protection circuit 36 detects the maximum voltage of the lamp_output terminal 223, and the corresponding light-emitting diode forward voltage due to the transistor 30 being turned off.
Vf(=2.0V〜2.4V)較電晶體30導通時其對應的發光二極體正向電壓Vf (=2.0V~2.4V) corresponds to the corresponding LED forward voltage when the transistor 30 is turned on
Vf〇3. 0V〜3. 2V)小，使得電晶體3〇在截止時燈串輸出端223的電 壓較電晶體導通時大得多，故通常保護電路36偵測的是電晶體3〇 截止時電壓，當上升的電壓達到某一值時，穩壓二極體38導通， 此時有一電流流過電阻44及46，且在電阻46第一端產生一分壓， 當此電壓大於電晶體5〇的臨界電壓時，電晶體5〇導通，因電晶 體50的第一端501與並聯穩壓器42陰極端422及電晶體30的控 制端303相連接，故並聯穩壓器42陰極端422及電晶體30的控 制端303被接為低準位致使定電流電路28被停止工作，進而控制 相對，燈串22被保護而不工作，而其它料22未受其相對應短 路保護電路36保護仍可正常卫作。因此，短路保護電路36可設 置為相對紐_ 22有m個發光二極體鱗時，相對絲路保護電 路36 __f動作’而此料22只有m-l個發光二極體短路 時，此燈串22仍可正常工作。 /综上所述’本發明之發光二極體驅動電路20係可用以偵測各 發光-極體燈串22的輸出端223電壓是否達到一預定電壓，並依 ΐΐϋ果執行相對應驗路職功能。當其中—發光二極體燈 j出端223電壓未超過該預定電壓時，發光二極體驅動電 m發光二極體燈串22正#作；反之當其中一發光 的輸出端223電壓超過該預定電壓時，其會造成相 電：36内極體38發生崩潰，且當短路保護 的路域產生電路40輸入端電壓達到一預設電壓 號使相保護電路36之短路信號產生電路40輸出短路信 ;對應&電流電路28之電晶體3G截止，藉以關前述發光 201208490 二極體燈串22以執行 仍不受影響而可繼續正常工=蒦功此’此時其他發光二極體燈串22 相較於先前技術太 尸=光二極體燈串之測 疋疋否要停止相對齡㈣“疋否達到該預疋電麗，以決 體之該發光二極體；串。之工作來關閉具有短路發光二極 於其中-個發光-:挪纟本發明之發光二鋪驅動電路只會 作，藉以料轉雜从姉歧驗電路之工 晶顯示產品會因她 呆護作用。雖然此時液 ==，所;降或畫面亮度不=^^ 戶的利顯示產品，這樣的液晶顯示產品更符合終端客 .1並可減〉、客戶的抱怨，而不會有先前技術中因其中一發 二極n燈串短路而造摘有發光二極贿串皆啊被強迫關閉 的缺點。 雖然本發明之實施例揭露如上所述，然並非用以限定本發 明，任何具有本發明所屬技術領域之通常知識者，均可依本發明 之實施例所揭露的内容，對本發明之形狀、結構或特徵做些許之 變更。因此，本發明所主張之保護範圍，須視本說明書所附之申鲁 請專利範圍所界定者為準。 【圖式簡單說明】 第1圖為一種現有的發光二極體驅動電路的電路圖。 第2圖為本發明之發光二極體驅動電路的較佳實施例的電路 圖。 第3圖為進一步說明第2圖所示定電流電路及短路保護電路 的電路圖。 201208490Vf 〇 3. 0V~3. 2V) is small, so that the voltage of the output terminal 223 of the transistor 3 截止 is much larger than when the transistor is turned on. Therefore, the protection circuit 36 usually detects the transistor 3 〇 cutoff. When the rising voltage reaches a certain value, the voltage stabilizing diode 38 is turned on, at which time a current flows through the resistors 44 and 46, and a voltage is generated at the first end of the resistor 46, when the voltage is greater than the transistor When the threshold voltage is 5〇, the transistor 5 turns on, because the first end 501 of the transistor 50 is connected to the cathode terminal 422 of the shunt regulator 42 and the control terminal 303 of the transistor 30, so the cathode terminal of the shunt regulator 42 422 and the control terminal 303 of the transistor 30 are connected to a low level to cause the constant current circuit 28 to be stopped, thereby controlling the opposite, the string 22 is protected from operation, and the other material 22 is not subjected to its corresponding short circuit protection circuit 36. Protection can still be normal. Therefore, the short circuit protection circuit 36 can be arranged to have m light-emitting diode scales relative to the button 22, and the light circuit protection circuit 36__f acts 'when the material 22 is only short-circuited by the ml light-emitting diodes, the light string 22 Still working. In summary, the LED driving circuit 20 of the present invention can be used to detect whether the voltage of the output terminal 223 of each of the light-emitting body strings 22 reaches a predetermined voltage, and perform the corresponding test function according to the result. . When the voltage of the output terminal 223 of the light-emitting diode lamp j does not exceed the predetermined voltage, the light-emitting diode driving the electric light-emitting diode lamp string 22 is made; otherwise, when the voltage of one of the light-emitting output terminals 223 exceeds the When the voltage is predetermined, it will cause phase electricity: 36 the inner body 38 collapses, and when the short circuit protection circuit generating circuit 40 input terminal voltage reaches a preset voltage number, the short circuit signal generating circuit 40 of the phase protection circuit 36 outputs a short circuit. The signal 3G of the corresponding & current circuit 28 is turned off, thereby turning off the aforementioned illumination 201208490 diode string 22 to perform still unaffected and can continue normal operation = 此 此 this 'other LED strings 22 Compared with the prior art, the corpse=photodiode light string test is to stop the relative age (4) “Why do you reach the pre-charged galvanic, to the light-emitting diode of the body; the work of the string is closed. It has a short-circuited light-emitting diode in which one-light---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Liquid ==, where; drop or screen brightness =^^ The user's profit display product, such a liquid crystal display product is more in line with the terminal customer.1 and can be reduced, customer complaints, without the prior art due to one of the two poles n light string short circuit The illuminating two-pole bribe is forced to close. Although the embodiments of the present invention are disclosed above, it is not intended to limit the present invention, and any one having the ordinary knowledge in the technical field to which the present invention pertains may be in accordance with the present invention. The invention is not limited by the scope of the invention, and the scope of protection claimed in the present invention is subject to the definition of the scope of the patent application attached to the specification. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit diagram of a conventional light emitting diode driving circuit. Fig. 2 is a circuit diagram of a preferred embodiment of the light emitting diode driving circuit of the present invention. Fig. 3 is a further illustration of Fig. 2. Circuit diagram of the constant current circuit and short circuit protection circuit shown. 201208490
【主要元件符號說明】 ίο:驅動電路 12 :主板電路 14 :定電流電路 143 :檢測電阻 15 :短路保護電路 152 :穩壓二極體 16 :地端 22 :發光二極體燈串 223 :輸出端 26 :發光二極體 30 :電晶體 302 :第二端 32 :檢測電阻 322 :第二端 36 :短路保護電路 381 :陽極端 40 :短路信號產生電路 421 :陽極端 423 :參考端 11 :開關 13 :開關控制電路 141 :電晶體 145 :回饋電路 151 :二極體 153 :短路信號產生電路 20 :發光二極體驅動電路 221 :輸入端 24 : DC/DC轉換器 28 :定電流電路 301 :第一端 303 :控制端 321 :第一端 34 :回饋電路 38 :穩壓二極體 382 :陰極端 42 :並聯穩壓器 422 :陰極端 44 :第一電阻 13 201208490 441 :第一端 46 :第二電阻 461 :第二端 481 :第一端 50 :開關 502 :第二端 52 :開關控制電路 56 :開關 562 :第二端 58 :誤差放大器 582 '·負輸入端 60 :參考電壓源 621 :第一端 623 :控制端[Main component symbol description] ίο: Drive circuit 12: Main board circuit 14: Constant current circuit 143: Detection resistor 15: Short circuit protection circuit 152: Voltage regulator diode 16: Ground terminal 22: LED string 223: Output Terminal 26: Light Emitting Diode 30: Transistor 302: Second End 32: Sense Resistor 322: Second End 36: Short Circuit Protection Circuit 381: Anode End 40: Short Circuit Signal Generation Circuit 421: Anode End 423: Reference End 11: Switch 13 : Switch control circuit 141 : transistor 145 : feedback circuit 151 : diode 153 : short circuit signal generating circuit 20 : light emitting diode driving circuit 221 : input terminal 24 : DC/DC converter 28 : constant current circuit 301 : first end 303 : control terminal 321 : first end 34 : feedback circuit 38 : voltage regulator diode 382 : cathode end 42 : shunt regulator 422 : cathode end 44 : first resistor 13 201208490 441 : first end 46: second resistor 461: second end 481: first end 50: switch 502: second end 52: switch control circuit 56: switch 562: second end 58: error amplifier 582 '. negative input 60: reference voltage Source 621: first end 623: control end
Vcc :直流電壓Vcc: DC voltage
Vref :參考電壓 0n/0ff :開關控制信號 442 :第二端 461 :第一端 48 :電容 482 :第二端 501 :第一端 503 :控制端 54 :主板電路 561 :第一端 563 :控制端 581 :正輸入端 583 :輸出端 62 :電晶體 622 :第二端 64 :電阻 Vdet :檢測電壓 Dim :調光控制信號Vref: reference voltage 0n/0ff: switch control signal 442: second end 461: first end 48: capacitor 482: second end 501: first end 503: control end 54: main board circuit 561: first end 563: control Terminal 581: Positive input terminal 583: Output terminal 62: Transistor 622: Second terminal 64: Resistor Vdet: Detection voltage Dim: Dimming control signal