201247013 六、發明說明： 【發明所屬之技術領域】 本發明係關於一種發光二極體驅動電路’尤指一種利用單 一控制器驅動多個轉換電路之發光二極體驅動電路。 【先前技術】 請參見第一圖，為習知之發光二極體驅動電路之電路示意 圖。發光二極體驅動電路包含了一控制器100、一第一升壓轉 換電路160a、一第二升塵轉換電路160b、一共用輸出電容C、 一第一發光二極體串150a、一第二發光二極體串15〇b、一最 低電壓選擇電路140以及一電流平衡電路145。第一升壓轉換 電路160a為一直流轉直流升壓轉換電路，包含一電感La、一 切換開關SWa以及一整流元件Da，電感La —端耦接一直流 輸入電壓Vin ’另一端搞接切換開關sWa之一端；而切換開關 SWa之另一端接地。整流元件Da之正端耦接電感La及切換 開關SWa之連接點負端搞接共用輸出電容c。第二升壓轉 換電路160b為一直流轉直流升壓轉換電路，包含一電感、 一切換開關SWb以及一整流元件Db，其元件連接關係與第一 升壓轉換電路160a相同。共用輸出電容c接收第一升壓轉換 電路160a及第二升壓轉換電路i60b所傳送之電力以產生一輸 出電壓Vout,以驅動第一發光二極體串15如及第二發光二極 體串150b發光。 一電流平衡電路145耦接第一發光二極體串15加及第二發 光二極體串150b之負端，使第一發光二極體串150a及第二發 光二極體串15〇b之電流一致，如此可使第一發光二極體串 150a及第二發光二極體串150b發光一致。最低電壓選擇電路 140耦接第一發光二極體串15〇a及第二發光二極體串15%之 負端’用以偵測並判斷這些負端中電壓最低者，並據此輸出一 f測訊號VFB。控制器100根據偵測訊號VFB產生一切換訊 號Sc ’以控制切換開關SWa、SWb之切換。 上述電路架構之優點為可使用單一控制器來驅動多個轉 201247013 換，路、^以提供更大的驅動能力來驅動更多的發光二極體。而 於f些轉換電路之輸出端彼此連接，在元件間的電器特性 ^因製程誤差而不同’而無法提供相同的電力之情況下，電 供較夕的轉換電路可以補償電力提供較少的轉換電路，而 使發光二極體驅動電路的整體效率較高。 山這些轉換電路之輸入端搞接同一個直流輸入電壓Vin ,輸 出1也因相互連接而有相同之輸出電壓¥〇说。而這些轉換電路 又受同一切換訊號Sc控制進行切換。升壓比 Vbut/Vin=l/(1-D)，其中D為切換訊號Sc的工作週期（Duty Cycle)。在理想狀態下’ Vin、v〇ut、D均相同，電感La、Lb 的電流應相同。然而，由於因製程誤差，切換開關SWa、SWb 的導通阻抗、臨界電壓(Threshold Voltage)、寄生電容不同， 電感La、Lb的電感值、寄生電阻不同，整流元件Da、Db的 順向導通電壓不同等等這些差異會導致這些轉換電路的升壓 比不同’而在轉換電路的輸出端彼此連接而強迫輸出電壓v〇ut 相同下，會使電感La及電感Lb的電流差異被放大。 電感La及電感Lb的電流差異會使切換開關swa、SWb 及整流元件Da、Db所產生的熱不同而有不同的溫升，甚至可 能因電感的電流太大而造成磁飽和而反而降低轉換效率。另 外，在一些限制溫升大小的應用環境，例如：液晶顯示器的背 光模組，這會造成需使用更佳（更低的導通阻抗）的金氧半場 效電晶體，來抑制切換開關的熱，而使發光二極體驅動電路的 成本因而上升。 【發明内容】 鑑於先前技術中的發光二極體驅動電路中的轉換電路的 輸入k及輸入端彼此連接’造成因元件的製程誤差而使電流差 異被放大’而使切換開關、整流元件的溫升差異大，也因此造 成轉換效率降低。本發明將轉換電路的輸出端分離以彼此驅動 不同的發光二極體模組’使轉換電路的電流差異減少而降低切 換開關及整流元件的溫升差異及提升轉換效率。本發明亦可利 201247013 用多個整流二極體串聯做為整流元件，以提升發光二極體驅動 電路之轉換效率。 為達上述目的，本發明提供了一種發光二極體驅動電路， 包含一第一發光二極體模組、一第二發光二極體模組、一第一 切換式轉換電路、一第二切換式轉換電路、一極端電壓選擇電 路、一電流平衡電路以及一控制器。第一切換式轉換電路具有 輛接一輸入電源之一第一輸入端及耦接第一發光二極體模組 =了第一輸出端’用以將輸入電源之電力轉換成一第一輸出電 壓以驅動第一發光二極體模組發光。第二切換式轉換電路具有 輕接輸入電源之一第二輸入端及耦接第二發光二極體模組之 了第二輸出端’用以將輸入電源之電力轉換成一第二輸出電壓 以驅動，二發光二極體模組發光。電流平衡電路耦接第一發光 一極體模組及第二發光二極體模組，用以使第一發光二極體模 組及第二發光二極體模組中之發光二極體電流大體上相同。極 i^電壓選擇電路耦接第一發光二極體模組及第二發光二極體 模，以偵測並選擇其中之一之偵測結果輸出。控制器減極端 電壓選擇電路’以據此控制第—切換式轉觀路及第二切換式 轉換電路進行轉換时別驅動第—發光二極顏組及第二發 光二極體模組發光。 本發明也提供了一種發光二極體驅動電路，包含一一 ί二極發光二極體模組、—第—切換式轉換^ 路、-第—切換式轉換電路、—電流平衡電路、—極 j轉換電路料二切換式轉換電路具有—整流元件 輸入電源之電力，整流元件包含複數辦聯之二極體 二 換電:之第一輸出端與第二切換式轉換 ^ ^ ilhVI AL· Fsl λ* »<. ». ^第— 擇電路以及-控制ϋ。第—娜式轉換電路具有健—輸入電 源之一第一輸入端及一第一輸出端。第二切換式轉換 ^妾輸入電源之-第二輸人端及—第二輸出端，其中ς -發光 輸出端彼此祕以共同驅動第—發光二極體模組及第 201247013 二極體模組發光。電流平衡電路耦接第一發光二極體模組及第 二發光二極體模組，用以使第一發光二極體模組及第二發光二 極體模組中之發光二極體電流大體上相同。極端電壓選擇電路 耦接第一發光二極體模組及第二發光二極體模組以偵測並選 擇其中之一之偵測結果輸出。控制器耦接極端電壓選擇電路， 以據此產生一控制訊號，使第一切換式轉換電路及第二切換式 轉換電路根據控制訊號進行轉換。 以上的概述與接下來的詳細說明皆為示範性質，是為了進 一步說明本發明的申請專利範圍。而有關本發明的其他目的與 優點，將在後續的說明與圖示加以闡述。 【實施方式】 請參見第二圖，為根據本發明之一第一較佳實施例之發光 二極體驅動電路之電路示意圖❶發光二極體驅動電路，包含一 第一發光二極體模組25〇a、一第二發光二極體模組25〇b、一 第一切換式轉換電路260a、一第二切換式轉換電路260b、一 極端電壓選擇電路240、一電流平衡電路245以及一控制器 200。第一切換式轉換電路26〇a具有耦接一輸入電源％之一 第一輸入端及耦接第一發光二極體模組25〇a之一第一輸出 端，用以將輸入電源Vi之電力轉換成一第一輸出電壓v〇a以 驅動第一發光二極體模組25〇a發光。第一切換式轉換電路 260a為一直流轉直流升壓轉換電路，包含一電感La、一切換 開關SWa、一整流元件Da&第一輸出電容Ca，電感La 一端 耦接一輸入電源Vi，另一端耦接切換開關 SWa之一端；而切 換開關SWa之另一端接地。整流元件Da之正端耦接電感La 及切換開關SWa之連接點，負端耦接第一輸出電容Ca。第二 切換式轉換電路260b具有輕接輸入電源Vi之一第二輸入端及 輛接第二發光二極體模組250b之-第二輸出端，用以將輸入 電源Vi之電力轉換成一第二輸出電壓v〇b以驅動第二發光二 201247013 極體模組250b發光。第二切換式轉換電路26〇b為一直流轉直 流升壓轉換電路，包含一電感Lb、一切換開關swb、一整流 元件Db及一第二輸出電容cb，電感Lb —端耦接輸入電源 另一端耦接切換開關swb之一端；而切換開關swb之另 一端接地。整流元件Db之正端耦接電感Lb及切換開關SWb 之連接點，負端搞接第二輸出電容Cb。電流平衡電路245耗 接第一發光二極體模組250a及第二發光二極體模組25〇b，使 第一發光二極體模組250a及第二發光二極體模組25〇b上的跨 壓Ik其中的發光二極體調整，而其中的發光二極體流經大體上 相同之電流。由於電流平衡電路245有其最低的操作電壓限 制，故極端電壓選擇電路24〇耦接第一發光二極體模組25〇a 及第二發光二極體模組250b以偵測第一發光二極體模組25〇a 及第二發光二極體模組250b與電涑平衡電路245連接點之電 位，並選擇其中驅動電壓最高的發光二極體模組之連接端之電 位輸出。在本實施例中，電流平衡電路245連接第一發光二極 體模組250a及第二發光二極體模組25〇b之負端，故電流平衡 ，路245選擇這些連接端中最低電壓者並據此輸出一迴授訊 號FB。控制器200耦接極端電壓選擇電路24〇 ,以據此控制 第一切換式轉換電路260a及第二切換式轉換電路26%分^產 生第一輸出電壓Voa及第二輸出電壓v〇b而分別驅動第一發光 二極體模組250a及第二發光二極體模組250b發光。 控制器200包含一誤差放大器210、一脈寬比較器220以 及一驅動電路230。誤差放大器210接收一參考電壓訊號Vr 以及迴授訊號FB ,並據此產生一脈寬調整訊號。脈寬比較器 220接收脈寬調整訊號及一斜波訊號以據此產生一脈寬控制訊 號Spwm。驅動電路230則根據脈寬控制訊號Spwm產=一^ 制訊號以同時控制切換開關SWa、SWb之切換。透過上述^ 迴授控制’使得電流平衡電路245得以順利操作在可操作的^最 低電壓或之上’而使第一發光二極體模組25〇a及第二發光二 極體模組250b的發光二極體流經大體上相同之電流。X 一 201247013 另外，為避免第一切換式轉換電路260a及第二切換式轉 換電路260b所產生的第一輸出電壓v〇a及第二輸出電壓Vob 過高，可額外增加一過壓偵測選擇電路265耦接第一切換式轉 換電路260a及第二切換式轉換電路260b以偵測第一輸出電壓 Voa及第二輸出電壓Vob並選擇其中最高者並據此輸出一過高 壓偵測訊號Dovp。控制器200更包含一過高壓比較器235， 而過尚壓比較器235接收過高壓偵測訊號Dovp及一過高壓參 考訊號Vovp並於過高壓偵測訊號之準位高於過高壓參考訊號 V0vp之準位時，產生一過壓保護訊號至驅動電路23〇，以停止 切換開關SWa、SWb之切換，使第一切換式轉換電路及第二 切換式轉換電路停止轉換。 一 當然，本發明亦可應用至三個或以上之轉換電路，而這些 轉J電路由單-控制器所控制，其輸入端均輕接同一輸入電; 而輸出端彼此獨立驅動對應的發光二極體模組。此為習知技術 之一般技藝者所熟知之電路變形，在此不再特別詳細說明。 根據上述說明，可知本發明透過單一控制器控制兩個 之轉換_分卿麟應的發光二極雜組，而且這些 電路的輸出端彼此駐。如此，每—轉換電路僅 ^動 ==，财些許不同，但在發光二極體 =太各轉，路之切換開關及整流元件所產』 異太大，使得其溫升差異較習知技藝的為 不至於差 大電感電流造成磁飽和崎低轉換效率之可避免較 接著，請參見第三圖，為根據本發明之一笛__ 之發光二極體驅動電路之電路示意圖。盥 j —方列 201247013 第一切換式轉換電路360a為一半橋式多重譜振轉換電 路，包含一第一切換開關Mia、一第二切換開關M2a、由一 串聯電感Lla、一並聯電感L2a和諧振電容Cra所組成的LLC 諧振網路、一變壓器Ta、整流元件Dla、D2a以及一第一輸出 電谷Ca。第一切換式轉換電路360b亦為一半橋式多重譜振轉 換電路，包含一第一切換開關Mlb、一第二切換開關M2b、 由一串聯電感Lib、一並聯電感L2b和諧振電容Crb所組成的 LLC諧振網路、一變壓器Tb、整流元件Dlb、D2b以及一第 二輸出電容Cb。透過半橋式多重諸振轉換電路，可使轉換電 路實現零電壓切換而使效率得以提升。上述的整流元件是兩個 二極體串聯而成，實際上也可以應用更多的二極體串聯而成。 利用多個二極體串聯，可使二極體平均跨壓。跨壓的下降可以 使二極體的寄生電容充放電所造成的功耗下降’尤其在輸出電 壓越高的應用架構下，改善轉換電路的轉換效率越明顯。因 此’第二圖所示的實施例中的整流元件Da、Db亦可為兩個或 以上的二極體串聯而成，甚至習知之電路架構（如第一圖所示 之發光二極體驅動電路）亦可使用此手段而改善轉換電路 換效率。 電流平衡電路345a、345b分別耦接第一發光二極體模组 中的發光二極體串350a、351a及第二發光二極體模組中的發 光二極體串350b、351b，使這些發光二極體串中的發光二極 體流經大體上相同之電流。極端電壓選擇電路34〇耦接發Z二 極體串350a、351a、350b、351b，以偵測電流平衡電路345a7 345b與發光二極體串350a、351a、350b、351b的連接點之電 位，並選擇這些連接端中最低電壓者並據此輸出一迴授訊號 FB。控制器300耦接極端電壓選擇電路34〇，以據此產生丄 控制訊號S1及第二控制訊號S2控制第一切換式轉換 360a及第二切換式轉換電路36〇b的第一切換開關μι&、' ^第二切換卿偷、腿，使第-切換式轉換電路％加及 第二切換式轉換電路360b分別產生第一輸出電壓v〇a及第二 201247013 輸出電壓Vob而分別驅動第一發光二極體模組及第二發光二 極體模組發光。 當然，本實施例也可以增加一過壓偵測選擇電路365耦接 第一切換式轉換電路360a及第二切換式轉換電路36〇b以偵測 第一輸出電壓Voa及第二輸出電壓Vob並選擇其中最高者並據 此輸出一過高壓偵測訊號Dovp。控制器3〇〇於判斷第一輸出 電壓^>a及第二輸出電壓Vob之任一高於一預定過壓保護值 時，停止產生第一控制訊號S1及第二控制訊號S2，以停止切 換開關Mia、Mlb、M2a、M2b之切換，使第一切換式轉換電 路及第二切換式轉換電路停止轉換。 如上所述，本發明完全符合專利三要件：新穎性、進步性 ，產業上的利用性。本發明在上文中已以較佳實施例揭露，然 熟習本項技術者應理解的是，該實施例僅用於描繪本發明，而 不應解讀為限制本發明之範圍。應注意的是，舉凡與該實施例 等效之變化與置換，均應設為涵蓋於本發明之範疇内。因此， 本發明之保護範圍當以下文之申請專利範圍所界定者為準。 【圖式簡單說明】 第一圖為習知之發光二極體驅動電路之電路示意圖。 第二圖為根據本發明之一第一較佳實施例之發光二極體驅動 電路之電路示意圖。 第三圖為根據本發明之一第二較佳實施例之發光二極體驅動 電路之電路示意圖。 【主要元件符號說明】 先前技術： 控制器100 最低電壓選擇電路140 電流平衡電路145 第一發光二極體串150a .第二發光二極體串150b 12 201247013 第一升壓轉換電路160a 第二升壓轉換電路160b 共用輸出電容C 電感La、lb 切換開關SWa、SWb 整流元件Da、Db 直流輸入電壓Vin 輸出電壓Vout 偵測訊號VFB 切換訊號Sc 本發明： 控制器200、300 誤差放大器210 脈寬比較器220 驅動電路230 過高壓比較器235 極端電壓選擇電路240、340 電流平衡電路245、345a、345b 第一發光二極體模組250a 第二發光二極體模組250b 第一切換式轉換電路260a、360a 第二切換式轉換電路260b、360b 過壓偵測選擇電路265、365 發光二極體串 350a、351a、350b、351b 輸入電源Vi 第一輸出電壓Voa 第二輸出電壓Vob 電感La、Lb 切換開關SWa、SWb 13 201247013 整流元件Da、Db 迴授訊號FB 參考電壓訊號Vr 脈寬控制訊號Spwm 過高壓偵測訊號Dovp 過高壓參考訊號Vovp 第一切換開關Mia、Mlb 第二切換開關M2a、M2b 串聯電感Lla、Llb 並聯電感L2a、L2b 諧振電容Cra、Crb 變壓器Ta、Tb 整流元件 Dla、D2a、Dlb、D2b 第一輸出電容Ca 第二輸出電容Cb 電流平衡電路 第一控制訊號S1 第二控制訊號S2201247013 VI. Description of the Invention: [Technical Field] The present invention relates to a light-emitting diode driving circuit, particularly a light-emitting diode driving circuit that drives a plurality of switching circuits by a single controller. [Prior Art] Please refer to the first figure, which is a circuit diagram of a conventional LED driving circuit. The LED driving circuit comprises a controller 100, a first boost converter circuit 160a, a second dust filter circuit 160b, a common output capacitor C, a first LED string 150a, and a second The LED string 15〇b, a minimum voltage selection circuit 140, and a current balancing circuit 145. The first boost converter circuit 160a is a DC-DC converter circuit including an inductor La, a switch SWa and a rectifying component Da. The inductor La is coupled to the DC input voltage Vin. The other end is connected to the switch sWa. One end; and the other end of the switch SWa is grounded. The positive terminal of the rectifying element Da is coupled to the negative end of the connection point of the inductor La and the switching switch SWa to engage the common output capacitor c. The second step-up conversion circuit 160b is a DC-DC converter circuit including an inductor, a switch SWb, and a rectifying element Db having the same element connection relationship as the first boost converter circuit 160a. The common output capacitor c receives the power transmitted by the first boost converter circuit 160a and the second boost converter circuit i60b to generate an output voltage Vout for driving the first LED string 15 and the second LED string. 150b glows. A current balancing circuit 145 is coupled to the first LED array 15 and the negative terminal of the second LED string 150b, so that the first LED string 150a and the second LED string 15b The currents are uniform, so that the first light-emitting diode string 150a and the second light-emitting diode string 150b can be made to emit light. The lowest voltage selection circuit 140 is coupled to the first LED array 15〇a and the second LED dipole string 15% of the negative terminal 'to detect and determine the lowest voltage among the negative terminals, and output a f test signal VFB. The controller 100 generates a switching signal Sc' based on the detection signal VFB to control the switching of the switching switches SWa, SWb. The advantage of the above circuit architecture is that a single controller can be used to drive multiple relays, which provide more drive capability to drive more LEDs. However, in the case where the output terminals of the conversion circuits are connected to each other and the electrical characteristics between the components are different due to process errors, and the same power cannot be supplied, the conversion circuit of the power supply can compensate for the power to provide less conversion. The circuit makes the overall efficiency of the LED driving circuit higher. The input terminals of these conversion circuits are connected to the same DC input voltage Vin, and the output 1 is also connected to each other and has the same output voltage. These conversion circuits are switched by the same switching signal Sc. The boost ratio Vbut/Vin=l/(1-D), where D is the duty cycle of the switching signal Sc. In the ideal state, ' Vin, v〇ut, and D are the same, and the currents of the inductors La and Lb should be the same. However, due to process error, the on-resistance, threshold voltage, and parasitic capacitance of the switches SWa and SWb are different, and the inductance values and parasitic resistances of the inductors La and Lb are different, and the forward conduction voltages of the rectifier elements Da and Db are different. These differences will cause the boosting ratios of these converter circuits to be different. When the output terminals of the converter circuits are connected to each other and the output voltage v〇ut is forced to be the same, the current difference between the inductor La and the inductor Lb is amplified. The difference in current between the inductor La and the inductor Lb causes the heat generated by the switching switches swa, SWb and the rectifying elements Da, Db to have different temperature rises, and may even cause magnetic saturation due to the current of the inductor being too large, thereby reducing the conversion efficiency. . In addition, in some application environments that limit the temperature rise, such as the backlight module of a liquid crystal display, this will result in the use of a better (lower on-resistance) MOS field-effect transistor to suppress the heat of the switch. The cost of the light-emitting diode driving circuit is thus increased. SUMMARY OF THE INVENTION In view of the prior art, the input k and the input terminals of the conversion circuit in the LED driving circuit are connected to each other 'the current difference is amplified due to the process error of the device', and the temperature of the switching switch and the rectifying element is made. The difference in the rise is large, which in turn causes a reduction in conversion efficiency. The present invention separates the output terminals of the conversion circuit to drive different light-emitting diode modules to each other to reduce the current difference of the conversion circuit and reduce the temperature rise difference of the switching switch and the rectifier element and improve the conversion efficiency. The invention can also be used in 201247013 to use a plurality of rectifying diodes in series as a rectifying element to improve the conversion efficiency of the LED driving circuit. To achieve the above objective, the present invention provides a light emitting diode driving circuit including a first light emitting diode module, a second light emitting diode module, a first switching conversion circuit, and a second switching. Conversion circuit, an extreme voltage selection circuit, a current balancing circuit, and a controller. The first switching conversion circuit has a first input end connected to an input power source and coupled to the first light emitting diode module=the first output end is configured to convert the power of the input power source into a first output voltage. Driving the first light emitting diode module to emit light. The second switching conversion circuit has a second input end of the light input power source and a second output end coupled to the second LED module for converting the power of the input power source into a second output voltage to drive The two-emitting diode module emits light. The current balancing circuit is coupled to the first light emitting body module and the second light emitting diode module for causing the light emitting diode current in the first light emitting diode module and the second light emitting diode module It is basically the same. The first voltage-selecting circuit is coupled to the first light-emitting diode module and the second light-emitting diode module to detect and select one of the detection result outputs. The controller reduces the extreme voltage selection circuit ’ to drive the first-to-light-emitting diode group and the second-light-emitting diode module to emit light when the first-switching switching path and the second switching-type converting circuit are controlled. The invention also provides a light-emitting diode driving circuit, comprising a 二2-pole light-emitting diode module, a first-switching conversion circuit, a first-switching conversion circuit, a current balancing circuit, and a pole j conversion circuit material two switching conversion circuit has - the power of the input power of the rectifying element, the rectifying element comprises a plurality of diodes of the two switching bodies: the first output end and the second switching type conversion ^ ^ ilhVI AL · Fsl λ * »<. ». ^第—Select circuit and control ϋ. The first-type conversion circuit has a first input terminal and a first output terminal of the health-input power source. The second switching type is the second input end and the second output end, wherein the ς-light output end is mutually driven to jointly drive the first light emitting diode module and the 201247013 diode module Glowing. The current balancing circuit is coupled to the first light emitting diode module and the second light emitting diode module for causing the LED current in the first light emitting diode module and the second light emitting diode module It is basically the same. The extreme voltage selection circuit is coupled to the first LED module and the second LED module to detect and select one of the detection result outputs. The controller is coupled to the extreme voltage selection circuit to generate a control signal, so that the first switching conversion circuit and the second switching conversion circuit convert according to the control signal. The above summary and the following detailed description are exemplary in order to further illustrate the scope of the claims. Other objects and advantages of the present invention will be described in the following description and drawings. [Embodiment] Please refer to the second figure, which is a schematic circuit diagram of a light-emitting diode driving circuit according to a first preferred embodiment of the present invention, a light-emitting diode driving circuit, including a first light-emitting diode module 25〇a, a second LED module 25〇b, a first switching converter circuit 260a, a second switching converter circuit 260b, an extreme voltage selection circuit 240, a current balancing circuit 245, and a control 200. The first switching conversion circuit 26A has a first input end coupled to an input power source and a first output end coupled to the first LED module 25A for inputting the power source Vi The power is converted into a first output voltage v〇a to drive the first LED module 25〇a to emit light. The first switching conversion circuit 260a is a DC-DC converter circuit including an inductor La, a switch SWa, a rectifying component Da & a first output capacitor Ca, one end of the inductor La coupled to an input power source Vi, and the other end coupled One end of the switch SWa is connected; and the other end of the switch SWa is grounded. The positive terminal of the rectifier element Da is coupled to the connection point of the inductor La and the switch SWa, and the negative terminal is coupled to the first output capacitor Ca. The second switching conversion circuit 260b has a second input end of the input power source Vi and a second output end of the second LED module 250b for converting the power of the input power source Vi into a second The output voltage v〇b is used to drive the second light-emitting diode 201247013 polar body module 250b to emit light. The second switching conversion circuit 26〇b is a DC-DC converter circuit including an inductor Lb, a switch SWb, a rectifying component Db and a second output capacitor cb. The inductor Lb is coupled to the other end of the input power source. One end of the switch swb is coupled; and the other end of the switch swb is grounded. The positive terminal of the rectifier element Db is coupled to the connection point of the inductor Lb and the switch SWb, and the negative terminal is coupled to the second output capacitor Cb. The current balancing circuit 245 consumes the first LED module 250a and the second LED module 25〇b, so that the first LED module 250a and the second LED module 25〇b The upper voltage Ik is adjusted by the light-emitting diodes, and the light-emitting diodes flow through substantially the same current. Since the current balancing circuit 245 has the lowest operating voltage limit, the extreme voltage selecting circuit 24 is coupled to the first LED module 25A and the second LED module 250b to detect the first LED. The pole body module 25A and the second LED module 250b are connected to the potential of the power balance circuit 245, and the potential output of the connection terminal of the LED module having the highest driving voltage is selected. In this embodiment, the current balancing circuit 245 is connected to the negative terminals of the first LED module 250a and the second LED module 25〇b, so that the current is balanced, and the path 245 selects the lowest voltage among the terminals. And according to this, a feedback signal FB is output. The controller 200 is coupled to the extreme voltage selection circuit 24A to control the first switching conversion circuit 260a and the second switching conversion circuit 26 to generate the first output voltage Voa and the second output voltage v〇b, respectively. The first light emitting diode module 250a and the second light emitting diode module 250b are driven to emit light. The controller 200 includes an error amplifier 210, a pulse width comparator 220, and a drive circuit 230. The error amplifier 210 receives a reference voltage signal Vr and a feedback signal FB, and generates a pulse width adjustment signal accordingly. The pulse width comparator 220 receives the pulse width adjustment signal and a ramp signal to thereby generate a pulse width control signal Spwm. The driving circuit 230 generates a signal according to the pulse width control signal Spwm to simultaneously control the switching of the switching switches SWa, SWb. The first light-emitting diode module 25A and the second light-emitting diode module 250b are configured by the above-mentioned feedback control 'making the current balancing circuit 245 to operate smoothly at an operable minimum voltage or above' The light emitting diodes flow through substantially the same current. X-201247013 In addition, in order to prevent the first output voltage v〇a and the second output voltage Vob generated by the first switching conversion circuit 260a and the second switching conversion circuit 260b from being too high, an overvoltage detection option may be additionally added. The circuit 265 is coupled to the first switching conversion circuit 260a and the second switching conversion circuit 260b to detect the first output voltage Voa and the second output voltage Vob and select the highest one and output an overvoltage detection signal Dovp accordingly. The controller 200 further includes an overvoltage comparator 235, and the overvoltage comparator 235 receives the high voltage detection signal Dovp and an overvoltage reference signal Vovp and is above the high voltage reference signal V0vp at the level of the overvoltage detection signal. When the level is on, an overvoltage protection signal is generated to the driving circuit 23A to stop the switching of the switching switches SWa and SWb, so that the first switching conversion circuit and the second switching conversion circuit stop switching. Of course, the present invention can also be applied to three or more conversion circuits, and these conversion J circuits are controlled by a single-controller, and the input terminals are all connected to the same input power; and the output terminals independently drive the corresponding illumination two. Polar body module. This is a circuit variant well known to those of ordinary skill in the art and will not be described in detail herein. According to the above description, it can be seen that the present invention controls the conversion of two of the two illuminating dipoles by a single controller, and the outputs of these circuits are mutually resident. In this way, each conversion circuit only moves ==, the difference is a little bit different, but in the light-emitting diode = too many turns, the switch of the circuit and the rectifier component are too large, so that the difference in temperature rise is better than the conventional skill. It is avoided that the magnetic saturation saturation conversion efficiency is not caused by the difference in inductance current. Referring to the third figure, it is a circuit diagram of the LED driving circuit of the flute according to the present invention.盥j - square column 201247013 The first switching conversion circuit 360a is a half bridge multi-spectral conversion circuit, comprising a first switching switch Mia, a second switching switch M2a, a series inductance Lla, a parallel inductance L2a and resonance An LLC resonant network composed of a capacitor Cra, a transformer Ta, rectifying elements Dla, D2a, and a first output electric valley Ca. The first switching conversion circuit 360b is also a half bridge multi-spectral conversion circuit, comprising a first switching switch M1b, a second switching switch M2b, a series inductor Lib, a parallel inductor L2b and a resonant capacitor Crb. A LLC resonant network, a transformer Tb, rectifying elements D1b, D2b, and a second output capacitor Cb. Through the half-bridge multi-vibration conversion circuit, the switching circuit can achieve zero voltage switching and improve efficiency. The above-mentioned rectifying element is formed by connecting two diodes in series, and in fact, more diodes can be used in series. By using a plurality of diodes in series, the diodes can be evenly cross-pressured. The drop in voltage across the voltage can reduce the power consumption caused by the parasitic capacitance charge and discharge of the diode'. Especially in the application architecture where the output voltage is higher, the conversion efficiency of the conversion circuit is more obvious. Therefore, the rectifying elements Da, Db in the embodiment shown in the second figure may also be formed by connecting two or more diodes in series, or even a conventional circuit structure (such as the LED driving shown in the first figure). The circuit can also use this means to improve the conversion circuit switching efficiency. The current balancing circuits 345a and 345b are respectively coupled to the LED arrays 350a and 351a in the first LED module and the LED strings 350b and 351b in the second LED module. The light emitting diodes in the diode string flow through substantially the same current. The extreme voltage selection circuit 34 is coupled to the Zener diode strings 350a, 351a, 350b, and 351b to detect the potential of the connection point of the current balancing circuit 345a7 345b and the LED strings 350a, 351a, 350b, and 351b, and Select the lowest voltage among these connections and output a feedback signal FB accordingly. The controller 300 is coupled to the extreme voltage selection circuit 34A to generate the first switching switch πb of the first switching conversion 360a and the second switching conversion circuit 36〇b according to the 丄 control signal S1 and the second control signal S2. , the second switching switch, the first switching output circuit 360b and the second switching conversion circuit 360b respectively generate a first output voltage v〇a and a second 201247013 output voltage Vob to respectively drive the first illumination The diode module and the second LED module emit light. Of course, in this embodiment, an overvoltage detection selection circuit 365 can be coupled to the first switching conversion circuit 360a and the second switching conversion circuit 36〇b to detect the first output voltage Voa and the second output voltage Vob. Select the highest one and output a high voltage detection signal Dovp accordingly. The controller 3 stops generating the first control signal S1 and the second control signal S2 to stop when any one of the first output voltage ^>a and the second output voltage Vob is higher than a predetermined overvoltage protection value. The switching of the switches Mia, Mlb, M2a, and M2b causes the first switching converter circuit and the second switching converter circuit to stop switching. As described above, the present invention fully complies with the three requirements of the patent: novelty, advancement, and industrial applicability. The invention has been described above in terms of preferred embodiments, and it is understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of the invention is defined by the scope of the following claims. [Simple description of the drawing] The first figure is a schematic circuit diagram of a conventional LED driving circuit. The second figure is a circuit diagram of a light emitting diode driving circuit according to a first preferred embodiment of the present invention. The third figure is a circuit diagram of a light emitting diode driving circuit according to a second preferred embodiment of the present invention. [Major component symbol description] Prior art: controller 100 minimum voltage selection circuit 140 current balancing circuit 145 first light emitting diode string 150a. second light emitting diode string 150b 12 201247013 first boost converter circuit 160a second liter Voltage conversion circuit 160b shared output capacitor C inductor La, lb switch SWa, SWb rectifier element Da, Db DC input voltage Vin output voltage Vout detection signal VFB switching signal Sc The present invention: controller 200, 300 error amplifier 210 pulse width comparison 220 drive circuit 230 overvoltage comparator 235 extreme voltage selection circuit 240, 340 current balancing circuit 245, 345a, 345b first light emitting diode module 250a second light emitting diode module 250b first switching converter circuit 260a 360a second switching conversion circuit 260b, 360b overvoltage detection selection circuit 265, 365 LED series 350a, 351a, 350b, 351b input power supply Vi first output voltage Voa second output voltage Vob inductance La, Lb switching Switch SWa, SWb 13 201247013 Rectifier element Da, Db feedback signal FB reference voltage signal Vr pulse width control signal Spwm over high voltage detection signal Dovp High-voltage reference signal Vovp First switch Mia, Mlb Second switch M2a, M2b Series inductor Lla, Llb Parallel inductor L2a, L2b Resonant capacitor Cra, Crb Transformer Ta, Tb Rectifier components Dla, D2a, Dlb, D2b First output capacitor Ca second output capacitor Cb current balancing circuit first control signal S1 second control signal S2
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