201123974 六、發明說明： 【發明所屬之技術領域】 本發明是有關於一種光源驅動技術，且特別是有關於一種發 光二極體(Light-Emitting Diode，簡稱LED)驅動電路。 【先前技術】 理想上LED順向導通電壓額定例如為3. 3V，但是元件必然存 在有誤差，例如在5%的誤差情況下，實際上LE：D順向導通電壓額 鲁疋將會"於3.135V〜3. 465V。因此，即使是由相同數量、相同類 型的LED串聯搞接所形成的燈串（Hght bar) ’實際上各個燈串的 順向導通賴（其為所串接的各個LED _向導通賴的總和)仍 然會彼此不同。如果在各個燈串上施加相同的偏壓，各個燈串在 導通時將會因為實際的軸導通賴不同而使流過各個燈串的電 机不同，當然各個燈串提供的亮度也就不同。為了解決各個燈串 電流不均所造成的亮度不均的問題，電流平衡電路就成了驅動LED 燈串相當重要的元件。 瞻圖1為種現有的led驅動電路的電路圖。請參照圖1，燈串 u〜lm中的每個燈串π是由相同數量、相同類型的LED串聯祕 所形成，其中m、η均為正整數，i為h中任一正整數。在每個 燈串π的第一端上施加相同的直流電壓Vbus，這個直 是將^心⑽或碰等常見規格的直流電壓趾通過直流 至直流(DC/DC)轉換器降壓或升壓而來的。在每個燈串Η的第二 端外加相應的開關Mi及電阻RSi再通過LED控制器使燈串i〜】m =電流達到平衡，這種在LED控制器外再外加元件的控制方式尤 :、適用於燈串為㊉龍、尚電流（_般順向導通電壓大於、電 流大於100mA)的應用場合。 201123974 對燈串π❼言，流過燈串】i的電流還會流過開則i及電阻 Rsi，因此可通過電阻Rsi檢測流過燈串u的電流（其為電壓形 式）。然後L£D控制器從電流檢測端iSi接收所檢測到的流過燈串 h的電流平均值並和預設的電流舰錄比較，再娜比較結果 從通道端OT送出錢控觸義導通或不導通，使流過燈串n 的電流平均值等於f流雜值或在—定誤差範_(_般在挪〜 8%的誤差範圍内）而有一定的均流效果。LED控制器還通過電驗 測知VDi檢測燈串η第二端上的電塵，在檢測到燈串η第二端 的過高時’表示燈串Η令有發光二極體發生短路，此時從通 道端CHi送出信號控制開關Mi不導通以保護電路。 “但是’市f專㈣LED控㈣可支制燈串數量是固定的， 隨著，串11 lm數里的增加’需要採用多個⑽控制器並聯使 2 些並聯使用的LED控制器之間的溝通及控制會使得設計成 本上升且會使得電路變得複雜而不容易控制。而且，隨著燈串^ 〜lm數量的增加’外加的開關m〜Mm和電阻如〜_的數量也 ㈢增加’同樣會使得設計成本上升且會使得電路更為複雜。 【發明内容】 有m本發a㈣目賊；^在触—種㈣二極體(剛驅 。。’路不需要採用專用的LED控制器，且驅動電路架構相當簡 早，可大幅降低成本。 達成上述目的及其它目的，本發明提出—種發光二極體 帛於驅動多個燈串組成的絲，每個燈串均包括多個 ，接的發光二_，每個燈串的第一端均接收燈串電壓。發 體驅動電路包括多個電流平衡器、短路保護電路、電壓補 員電路以及調光電路。每個電流平衡器均包括電晶體及調節器， 201123974 電曰曰體的第-端墟至相應的燈#的第二端 過調節器_至接地，在調節器不動 :通 =期望值時_晶體二 電流賊值時控制電晶體的工作點遠離截止區。短路保 輸出一燈串的第二端的電壓大於過謝值時 未檢_任—燈㈣第二獅賴大於過麗 第- 號。電_射路用於在檢_任一燈串的 電電壓期望辦不影響燈串電壓。調光 =路=在收到關信號時，輸出控制信號控制所有調節器不動 ::ί!㈣開啟錢時’根據脈寬調變形式_光信號輸出控 第j的賴小於電壓期隸_高燈串祕，並在未檢測到任 制所有晰&交替地動作及不動作’以實現光源的脈寬 m2明的驅動電路在每個燈串的第二端串接電流平衡器 产带行v我回授控制來調整燈串各自流過的電流，加入電壓補 U微調，串電•以便使具有不同順向導通電壓的每個燈串都 ^凡王點7C ’另加人短路保護電路以便在燈串中有發光二極體 二路時咖LED驅動電路，以保護燈料至於因過電流而燒毀。 於本發明的LED驅動電路不需要制專用的LED控制器 9且驅 動電路架構相當簡單，可大幅降低成本。 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_圖式，作詳細說明如下。 【實施方式】 201123974 開關是第==常:識者應當知道開關或 在#編_ ^ 第 端。第—型開關或開關電路 制端收到低準位信號時不導通（即第—端及第二端斷^;)第二^ 開關或開關電路在㈣端收龍準位錢時導通（即第—端 二端導接）並在控制端收到高準位信號時不導通（即第一 第-型開關或開關電路可以NPN雙極性電晶體（或“ 極端（或源極端），控制端為基極端（或閘極端）；第二型_= 關，路可以PNP雙極性電晶體（或p通道場效應電晶體)實現，第 =射極端（或源極端第二端為集極端（或沒極端），控制端 或閘極端）。另外，電阻(resistOT)及電容―> 均具有第-端及第二端，二極體、發光二極體及齊納二極體(Zener diode)均具有陽極端及陰極端，以下不再贅述。 圖2為依照本發明一較佳實施例的發光二極體⑽)驅動電路 的方塊圖。請參照U 2，LED驅動電路2祕驅動燈串Η〜h組 成的光源’每個燈串h均是由烟數量、_翻的發光二極體 D1〜Dn串聯耗接所形成，其中m、n均為正整數，丄為h中任 -正整數。本領域具有通常知識者應當知道為了讓料丨丨〜化可 正常工作，在每個燈串π中，發光二極體Di的陽極端應搞接至 燈串li的β第-端’發光二極體Dk的陰極端應搞接至發光二極體 D(k+1)的陽極’且發光二極體Dn的陰極端應麵接至燈串η的 第二端Ph ’其中〜(η_υ中任一正整數。燈串n〜im组成 的光源可制作為液晶顯示器的背光源，例如直下式或側面入光 式背光源。 Μ驅動電路2包括直流至直流(DC/DC)轉換_ 2卜電流平衡 201123974 電路22、短路倾電路23、賴顯魏％以及調光電路π。 ^ 21為降壓或升壓轉換器，將5V、12V、撕 格的直流電壓MC降壓或升壓而轉換為直流燈串 ==。1)(：服轉換器21通常採用切換式電源轉換器，其至少 包括功率電晶體及控制器（圖中未繪示）。控制器的回授 至少-個電阻，通過電阻來檢職/DC轉換器21輸出的燈串電壓 換為適當準位的回授信號FB。當控制器從回授端收到的 ==小於預設值時’控制器會調整功率電晶體的切換來調 ^串電壓Vbus，當控制ϋ從回授端__授信號FB大於預設 日、’控制时調整神電晶體的切換來調低燈串電壓_。如 果在控㈣_授端_接的電阻旁再並聯另__個電阻，則會使 控制器的回授端_接的電阻的整體電阻值下降，進而使得從回 ，端收到_授信額必然小於預設值，此時控制器會調整功率 電晶體的切換來調高燈串電壓Vbus。每個燈串η的第—端均 至DC/DC轉換器21以接收燈串電壓Vbus來獲取導通所需的偏壓。 電流平衡電路22包括多個電流平衡器，每個電流平衡 ，相應的燈串h的第三端Pli以進行自我回授控制來調整流過燈 h的電流，使流過料li的電流在2%〜期誤差範圍内而有 更好的均流效果。每個電流平衡器均包括電晶體QH及調節器 22i:在每個電流平衡器中，電晶體QH的第—端祕至相應的燈 li的第二端Pli，電晶體Qli的第二端通過調節器22i耦接至 ，地。在調節器22i不動作時，電晶體Qli工作在截止區。在調 即器22ι動作日夺’電晶體qH工作在線性區且調節器如用於 測相應的料Π的電流並和電軸望值味，以便在相應的燈串 h的電流大於電流期望值時控制電晶體Qli的工作點靠近截止區 而使燈串li力電流變小’並在相應的燈串u的電流小於電流期 201123974 望值時控制電晶體Qli的工作點遠離截止區而使燈串Η的電流變 大。所以’電晶體Qli相當於跨壓可調的元件，用於調節各個燈 串li的順向導通電壓使流過各個燈串u的電流達到平衡。電晶 體Qh可採用電流驅動的雙極性電晶體或電壓驅動的場效應電晶 體、，其中以採用場效應電晶體為佳，這是因為若電晶體QU採用 電流驅動的雙極性電晶體，則控制信號vc〇N的電流準位必須足夠 大以便同時驅動電晶體QU〜Qlm，這對驅動電路25的設計是很大 的負擔。 短路保護電路23用於在檢測到任一燈串的第二端的電壓大於 過壓期望值時’表示燈串丨丨〜；^中有某—燈_的發光二極體短路 而使該燈串不正常，故輸出關閉信號OFF，並在未檢測到任一燈串 =第二端的電壓大於過壓期望值時，表示所有燈串n〜lm均正 常，故輸出開啟信號0N。關閉信號或開啟信號⑽可提供至 DC/DC轉換n DG/DC轉㈣21在收觸閉錢QFF時關閉而 不再提供燈串電壓Vbus’ ；關閉信號0FF或開啟信號⑽還可提供 至外。卩電路，如控制液晶顯示益的主板(main b〇ard)的微控制器 以便其在收到關閉信號off時依序關閉其它週邊元件。 電屢補償電路24用於在檢測到任一燈串的第二端的電壓小於 電壓期望值時’通過降低DC/DC轉換器21的回授信號ρβ來調高 燈串電壓Vbus，並在未檢測到任一燈㈣第二端的電壓小於電壓 期望值時’不影響燈串電壓Vbus。 調光電路25用於在收到關閉信號0FF (有燈_不正常）時，輸 出控制信號VC0N控制所有調節器221〜22m不動作，並在收到開 啟“號0N (所有燈串均正常）時，根據脈寬調變（puise_Wid比 Modulation，簡稱PWM)形式的調光信號DIM輸出控制信號 控制所有調節器221〜22m交替地動作及不動作，以實現 201123974 PWM調光。其中’ PWM形式的調光信號DIM的每個週期均包括一致 能期間及一禁能期間，例如在致能期間時調光信號為高準位 信號’而在禁能期間時調光信號DIM為低準位信號。另外，對於 控制信號VC0N而言，在調光電路25收到關閉信號OFF (有燈串不 正常）時’或在調光電路25收到開啟信號on (所有燈串均正常） 且調光信號DIM在禁能期間時，控制信號VC0N例如為低準位信 號，以控制調節器221〜22m不動作；而在調光電路25收到開啟 信號0N (所有燈串均正常）且調光信號DIM在致能期間時，控制信 號VC0N例如為高準位信號，以控制調節器221〜22m動作。口 圖3A為圖2所示電流平衡器的一電路實施例。請參照圖3八， 電流平衡器包括電晶體Q1 i及調節器22i。調節器22i包括限流電 阻Rbi、檢測電阻Rsi及並聯穩壓器（shunt regulat〇r) 。其201123974 VI. Description of the Invention: [Technical Field] The present invention relates to a light source driving technology, and more particularly to a Light-Emitting Diode (LED) driving circuit. [Prior Art] Ideally, the LED forward voltage rating is, for example, 3. 3V, but the component must have an error. For example, in the case of 5% error, the LE:D forward voltage will be recklessly " At 3.135V~3. 465V. Therefore, even if the same number and the same type of LEDs are connected in series, the light string (Hght bar) is actually the direct communication of each light string (which is the sum of the LEDs connected in series) ) will still be different from each other. If the same bias voltage is applied to each of the strings, the individual strings will be different when the actual axis conduction depends on the motor flowing through the strings. Of course, the brightness provided by each string will be different. In order to solve the problem of uneven brightness caused by uneven current of each string, the current balancing circuit becomes a very important component for driving the LED string. Figure 1 is a circuit diagram of an existing LED driver circuit. Referring to FIG. 1, each light string π in the light string u~lm is formed by the same number and the same type of LED serial connection, wherein m and η are positive integers, and i is any positive integer in h. The same DC voltage Vbus is applied to the first end of each string π. This is a direct voltage toe of a common specification such as a core (10) or a bump, which is stepped down or boosted by a DC-to-DC converter. Come here. At the second end of each string Η, a corresponding switch Mi and a resistor RSi are applied, and then the LED controller is used to balance the lamp string i~]m=current, and the control mode of the component is added outside the LED controller: It is suitable for applications where the string is a ten-long, still current (_like forward voltage is greater than, current is greater than 100mA). 201123974 For the light string π ,, the current flowing through the light string i will flow through the opening i and the resistance Rsi, so the current flowing through the string u (which is a voltage form) can be detected by the resistor Rsi. Then, the L£D controller receives the detected average value of the current flowing through the string h from the current detecting terminal iSi and compares it with the preset current ship record, and then compares the result from the channel end OT to send the money control touch-to-turn or It does not conduct, so that the average value of the current flowing through the lamp string n is equal to the f-flow impurity value or has a certain current sharing effect in the -set error range _ (in the range of ～ 〜 8% error). The LED controller also detects the electric dust on the second end of the lamp string η by the electric detector. When detecting that the second end of the lamp string η is too high, the LED string indicates that the light-emitting diode is short-circuited. The signal is sent from the channel terminal CHi to control the switch Mi to be non-conducting to protect the circuit. "But the city's special (four) LED control (four) can control the number of strings is fixed, with the increase of the string 11 lm number 'requires multiple (10) controllers in parallel to make two parallel use between the LED controllers Communication and control will increase the design cost and make the circuit complicated and not easy to control. Moreover, as the number of light strings ^ lm increases, the number of additional switches m to Mm and the number of resistors such as ~ _ is also increased (3). It will also increase the design cost and make the circuit more complicated. [Summary] There is a m-issue a (four) thief; ^ in the touch-type (four) diode (just drive. '' road does not need to use a dedicated LED controller The driving circuit structure is quite simple, and the cost can be greatly reduced. To achieve the above and other objects, the present invention provides a light-emitting diode that drives a plurality of strings of wires, each of which includes a plurality of wires. The first end of each string receives the string voltage. The body drive circuit includes a plurality of current balancers, a short circuit protection circuit, a voltage compensation circuit, and a dimming circuit. Each current balancer Including transistor And regulator, 201123974 The first end of the electric body to the corresponding lamp # the second end of the regulator _ to the ground, when the regulator does not move: pass = expected value _ crystal two current thief value when controlling the transistor The working point is far away from the cut-off area. The voltage at the second end of the short-circuit protection output string is greater than the value of the thank-you value. _ Ren-light (4) The second lion is larger than the Lili No. - Electric _ shooting is used for inspection The voltage of a string of lights is expected to not affect the voltage of the string. Dimming = Road = When the signal is received, the output control signal controls all the regulators to move:: ί! (4) When the money is turned on, 'Deformation according to the pulse width _ The optical signal output control is less than the voltage period of the _high-light string secret, and in the absence of detection of all the ambiguous & alternate action and no action 'to achieve the light source pulse width m2 clear drive circuit in each The second end of the string is connected in series with the current balancer. The feedback control is used to adjust the current flowing through the string, and the voltage is added to the U to adjust the string to make each lamp with different forward voltages. Strings ^ Van Wang point 7C 'Add a short circuit protection circuit so that there is a light in the string The polar body two-way LED driver circuit protects the lamp material from being burnt due to overcurrent. The LED driver circuit of the present invention does not require a dedicated LED controller 9 and the drive circuit architecture is relatively simple, which can greatly reduce the cost. The above and other objects, features, and advantages of the present invention will become more apparent and understood. It should be known that the switch or at the #编_^ terminal. The first type switch or the switch circuit terminal does not conduct when it receives the low level signal (ie, the first end and the second end break ^;) the second ^ switch or switch circuit When the (4) end receives the money, it conducts (ie, the first end and the second end conducts) and does not conduct when the control end receives the high level signal (ie, the first first type switch or the switch circuit can be NPN bipolar transistor) (or “extreme (or source extreme), the control terminal is the base terminal (or gate terminal); the second type _= off, the path can be realized by PNP bipolar transistor (or p-channel field effect transistor), the first = the emitter (or the second end of the source is the set extreme (or not End), a control terminal or gate terminal). In addition, the resistor (resistOT) and the capacitor-> have a first end and a second end, and the diode, the light-emitting diode, and the Zener diode each have an anode end and a cathode end, and the following are no longer Narration. 2 is a block diagram of a driving circuit of a light emitting diode (10) in accordance with a preferred embodiment of the present invention. Please refer to U 2, LED driving circuit 2 secret driving light source Η ~ h composed of light source 'each string h is formed by the number of smoke, _ turn of the LEDs D1 ~ Dn series consumption, where m, n is a positive integer, and 丄 is any - positive integer in h. Those skilled in the art should know that in order to make the material work properly, in each light string π, the anode end of the light-emitting diode Di should be connected to the β-end end of the light string li. The cathode end of the polar body Dk should be connected to the anode of the light-emitting diode D(k+1) and the cathode end of the light-emitting diode Dn should be connected to the second end of the light string η Ph ' where ~(η_υ中Any positive integer. The light source consisting of a light string n~im can be made as a backlight of a liquid crystal display, such as a direct-lit or side-lit backlight. Μ drive circuit 2 includes DC to DC conversion (DC/DC) conversion _ 2 Current balance 201123974 Circuit 22, short circuit circuit 23, Lai Xianwei%, and dimming circuit π. ^ 21 is a buck or boost converter, which converts or boosts the 5V, 12V, and the DC voltage MC of the tear grid. For the DC lamp string ==. 1) (: The service converter 21 usually adopts a switching power converter, which at least includes a power transistor and a controller (not shown). The controller feedbacks at least one resistor, The string voltage output by the inspection/DC converter 21 is replaced by a resistor to a feedback signal FB of an appropriate level. When the controller receives the == less than the preset value from the feedback terminal, the controller adjusts the switching of the power transistor to adjust the string voltage Vbus. When the control ϋ is sent from the feedback terminal __ the signal FB is greater than the preset date, ' Adjust the switching of the god crystal to reduce the string voltage _. If you connect another __ resistor in parallel with the resistance of the control (four) _ terminal, the feedback resistor of the controller will be connected. The overall resistance value decreases, so that the received _ credit amount from the back end must be less than the preset value. At this time, the controller adjusts the switching of the power transistor to increase the string voltage Vbus. The first end of each string η The DC/DC converter 21 is multiplexed to receive the string voltage Vbus to obtain the bias voltage required for conduction. The current balancing circuit 22 includes a plurality of current balancers, each of which is balanced, and the third terminal Pli of the corresponding string h is Self-feedback control is performed to adjust the current flowing through the lamp h so that the current flowing through the material li has a better current sharing effect within a 2% to period error range. Each current balancer includes a transistor QH and a regulator. 22i: in each current balancer, the first end of the transistor QH is secreted to the corresponding lamp li The second end Pli, the second end of the transistor Qli is coupled to the ground through the regulator 22i. When the regulator 22i is not in operation, the transistor Qli operates in the cut-off area. In the switch 22i action, the transistor qH works. In the linear region and the regulator is used to measure the current of the corresponding material and to appreciate the electric axis, so that the operating point of the transistor Qli is close to the cut-off region and the lamp is made when the current of the corresponding string h is greater than the current expected value. The string li current becomes smaller 'and the current of the corresponding lamp string u is smaller than the current period 201123974. The operating point of the control transistor Qli is far from the cut-off area, so that the current of the lamp string 变 becomes larger. Therefore, the transistor Qli is equivalent. A voltage-adjustable component for adjusting the forward voltage of each string li to balance the current flowing through each string u. The transistor Qh can be a current-driven bipolar transistor or a voltage-driven field effect transistor, wherein a field effect transistor is preferred because the transistor QU is controlled by a current-driven bipolar transistor. The current level of the signal vc 〇 N must be large enough to drive the transistors QU Q Qlm at the same time, which is a great burden on the design of the drive circuit 25. The short circuit protection circuit 23 is configured to: when it is detected that the voltage of the second end of any of the light strings is greater than the expected value of the overvoltage, the light emitting diode of the light source is short-circuited and the light string is not shorted. Normal, the output close signal is OFF, and when no light string is detected = the voltage at the second end is greater than the expected value of the overvoltage, it means that all the light strings n~lm are normal, so the output open signal is 0N. The turn-off signal or the turn-on signal (10) can be supplied to the DC/DC converter. n DG/DC turn (4) 21 is turned off when the closed money QFF is closed and the string voltage Vbus' is no longer supplied; the turn-off signal 0FF or the turn-on signal (10) can also be supplied. A circuit, such as a microcontroller that controls the main board of the liquid crystal display, so that it closes other peripheral components in sequence when it receives the off signal off. The electric compensation circuit 24 is configured to increase the string voltage Vbus by lowering the feedback signal ρβ of the DC/DC converter 21 when detecting that the voltage of the second end of any of the strings is less than the voltage expected value, and detecting that the string voltage Vbus is not detected When the voltage at the second end of any lamp (4) is less than the expected voltage value, 'the string voltage Vbus is not affected. The dimming circuit 25 is configured to control all the regulators 221 to 22m not to operate when the shutdown signal 0FF (with lamp_not normal) is received, and to turn on the number 0N (all strings are normal) When the dimming signal DIM output control signal in the form of pulse width modulation (puise_Wid than Modulation, abbreviated as PWM) is used to control all the regulators 221~22m to alternately operate and not operate, to realize the 201123974 PWM dimming. Each period of the dimming signal DIM includes a coincidence period and an disable period, for example, the dimming signal is a high level signal during the enable period and the dimming signal DIM is a low level signal during the disable period. In addition, for the control signal VC0N, when the dimming circuit 25 receives the OFF signal OFF (the lamp string is abnormal) or the dimming circuit 25 receives the ON signal on (all the strings are normal) and the dimming signal When the DIM is in the disable period, the control signal VC0N is, for example, a low level signal to control the regulators 221 to 22m not to operate; and the dimming circuit 25 receives the ON signal 0N (all strings are normal) and the dimming signal DIM During the enablement period The control signal VC0N is, for example, a high-level signal to control the regulators 221 22 22 m. Figure 3A is a circuit embodiment of the current balancer shown in Figure 2. Referring to Figure 3, the current balancer includes the transistor Q1. And the regulator 22i. The regulator 22i includes a current limiting resistor Rbi, a detecting resistor Rsi, and a shunt regulator (shunt regulat〇r).
中，並聯穩壓器TLi具有陰極端κ、陽極端A及參考端R，可採^ 市售積體電路TL43卜TL432等。限流電阻Rbi的第一端麵接至調 光電路25以接收控制信號vc〇N，限流電阻肋丨的第二端叙接 晶體Qli的控制端及並聯穩壓器TLi的陰極端κ，檢測電阻 的第-端輕接至電晶體Qli的第二端及並聯穩壓器TLi的參考 端’且檢測電阻RS1的第二端耗接至並聯穩壓器TLi的陽極端A 過燈串Π的電流還會流過電晶體QH及檢測電阻 因此可通過檢測電阻Rsi檢測流過燈串π的電流(其為電壓 ^)。假設並聯穩壓器TLi採用積體電路TU31，其將參考端r ^的參考電壓_做比較，在參考端R電壓大於 端A相t電壓㈣時’並聯穩壓器以導通而陰極端K和陽極 化Α相當缝路，在參相R龍小於2 ^ 並聯穩壓器瓜不導通而陰極端K和陽極端A相^^在本 201123974 例中’電流難值為參考電屋Vref除以制電阻⑹的電阻值， 可表不為Vref/Rsi，其中的Vref和採用的並聯穩壓器有關，因此 可通過選擇不同的並聯穩壓器來改變電流期望值。 二β當控制信號VC0N為低準位信號時，控制調節器22i不動作， 這是，為電晶體Qli的控綱收到低準位信號紅作在截止區， 此時/又有電流流過檢測電阻Rsi，檢測電阻Rsi的跨壓（即 R電壓）為零而使並聯穩壓$ TLi轉通，因此調節器饥無法 測流過燈串li的電流再據以回授控制電晶體Qli進行電流。 =控制b虎VC0N為高準位信號時’控制調節器22i動作，此時電 晶體Q1 i工作在線性區且調節器22丨用於檢測相應的燈串1 i的 机並和電軸望值比較，以便在料Η的電流大於電軸望值 檢測電阻Rsi的跨壓大於參考電壓Vref)時，因並聯穩壓器 導通而使電晶體QH的控制端墟至接地 1 =工作點_止區而使料Η _變小；並^^體^ 机小於電流期望值（即檢測電阻Rsi力跨壓小於參考電壓㈣ 時’因並聯穩壓器TLi不導通而使電晶體Qli的控制端收； 制信號· ’進而控制電晶體Qli的工作點遠離戴止區而 使燈串li的電流變大。 ，、3B為圖2所示電流平衡器的另一電路實施例。請參照 電，平衡器包括電晶體Qli及調節器22i。調節器22i包括運The shunt regulator TLi has a cathode terminal κ, an anode terminal A and a reference terminal R, and can be commercially available as an integrated circuit TL43 TL432. The first end surface of the current limiting resistor Rbi is connected to the dimming circuit 25 to receive the control signal vc〇N, and the second end of the current limiting resistor rib is connected to the control end of the crystal Qli and the cathode end κ of the shunt regulator TLi. The first end of the sense resistor is connected to the second end of the transistor Qli and the reference terminal of the shunt regulator TLi' and the second end of the sense resistor RS1 is drained to the anode terminal A of the shunt regulator TLi. The current also flows through the transistor QH and the sense resistor so that the current flowing through the string π (which is the voltage ^) can be detected by the sense resistor Rsi. Assume that the shunt regulator TLi uses the integrated circuit TU31, which compares the reference voltage _ of the reference terminal r ^. When the reference terminal R voltage is greater than the terminal A phase t voltage (four), the shunt regulator is turned on and the cathode terminal K and Anodized Α is quite a slit, in the phase R R less than 2 ^ shunt regulator melon is not turned on and cathode end K and anode end A phase ^ ^ in this 201123974 case 'current hard value is reference electric house Vref divided by The resistance of resistor (6) can be expressed as Vref/Rsi, where Vref is related to the shunt regulator used, so the current expectation can be changed by selecting different shunt regulators. When the control signal VC0N is a low level signal, the control regulator 22i does not operate. This is, for the control of the transistor Qli, the low level signal is received in the cutoff region, and at this time, a current flows again. Detecting the resistance Rsi, the voltage across the sense resistor Rsi (ie, the R voltage) is zero, and the shunt regulator $TLi is turned on, so the regulator can't measure the current flowing through the string li and then feedback the control transistor Qli. Current. = control b tiger VC0N is a high level signal when the 'control regulator 22i action, at this time the transistor Q1 i works in the linear region and the regulator 22 is used to detect the corresponding string 1 i and the axis value Comparing, so that when the current of the material is greater than the voltage across the electric axis detection resistance Rsi is greater than the reference voltage Vref), the control terminal of the transistor QH is grounded to the ground 1 = operating point_stop region due to the conduction of the shunt regulator And make the material _ _ smaller; and ^ ^ body ^ machine is less than the current expected value (ie, the detection resistance Rsi force across the voltage is less than the reference voltage (four) 'because the shunt regulator TLi is not conducting, so that the control terminal of the transistor Qli; The signal ·' further controls the operating point of the transistor Qli away from the wearing area to increase the current of the lamp string li. 3B is another circuit embodiment of the current balancer shown in Fig. 2. Please refer to the electric, the balancer includes Transistor Qli and regulator 22i. Regulator 22i includes
Li=plv及τ則電，卜運算放大器0ρι的非反相輪入端接 01又齡Vset ’運异放大器0P1的反相輸入端耗接至電晶體 :、第二端及檢測電阻Rsi的第一端運算放大器0P1的輸 光電ίί5晶的控制端’運算放大器0P1的電源端輕接至調 接地。在柏^運 賴阻Rsi㈣：軸至 不j中運异放大|g 0P1的電源端包括正電源端及負電 10 201123974 源端，正電源端輕接至調光電路25以接收控制信f虎聰，而負電 源端输至接地。另外，運算放大H QP1可以比較器取代。在本 例中，電流期望值為設定電壓Vsetl除以檢測電阻如的電阻值， 可表不為Vsetl/Rsi，因此可通過設定不同的設定電壓改 變電流期望值。Li=plv and τ are electric, the non-inverting wheel of the operational amplifier 0ρι is connected to the 01 and the Vset's inverting input of the op amp 0P1 is connected to the transistor: the second end and the detection resistor Rsi The control terminal of the operational amplifier 0P1 of one end of the op amp 0P1 is connected to the ground of the op amp 0P1. In the cypress, the Rsi (R) (four): the shaft to the non-j in the transmission | g 0P1 power supply terminal includes the positive power terminal and the negative power 10 201123974 source, the positive power terminal is lightly connected to the dimming circuit 25 to receive the control letter f Hu Cong And the negative power terminal is connected to ground. In addition, the operational amplification H QP1 can be replaced by a comparator. In this example, the current expectation value is the set voltage Vsetl divided by the resistance value of the sense resistor. It can be expressed as Vsetl/Rsi, so the current expectation value can be changed by setting different set voltages.
與圖3A的工作原理相同，在調節器22i不動作時，電晶體奶土 工作在截止區。在調節器22i動作時，電晶體QH工作在線性區 且調節器22i 檢測相應的燈串u力電流並和電流期望值比 較’以便在燈串li的電流大於雜期望值（即檢測電阻如的跨 壓纽設定電壓Vsetl)時，運算放大器〇ρι的輸出端輸出低準位 ㈣控制電晶體Qh的工作點靠近截止區而使燈串Η的電流變 小；並在燈串li的電流小於電流期望值（即檢測電阻如的^壓 小於設定電壓Vsetl)時，運算放大器〇P1的輸出端輸出高準位作 號控制電晶體Qli的工作點遠離截止區而使燈串u的電流變大。 圖4為圖2所示短路保護電路23的—電路實施例 4 ’短路保護電路23包括二極體D11〜_、齊納二極體zdi:圆 =31:谓電路咖。每個二極體DU的陽極端耦接至相； 的燈串h的第二知Ph，每個二極體Dli的陰極端轉接至齊納二 極體ZD1的陰極端，齊納二極體ZD1的陽極端輕接至 23i，開關電路232的第一端輕接至調光電路25，且 = 的第二端粞接至禁能錢(在本例巾湘接地提供低準 另外，分壓電路231包括電mR1〜R4及電容C1，其 ^ R4用於分壓，而電容C1用於穩壓遽波。開關電路= 開關Q1 ’故開關電路232為第一型開關電路。 隹怯一燈串的第 ' 叫……王八…迎！期呈值時，齊納二未 ZD1崩潰’通過分壓電路231將落在電阻R1〜R4的電壓分^ 201123974 輸出適當準位的高準位域到開關電路232控制端以控制開關電 路232導通’此時禁能信號傳送到調光電路25而實現調光電路25 收到關閉信號OFF。在未檢測到任一燈串的第二端的電壓大於過壓 期望值時，齊納二極體ZD1未崩潰，未有電壓落在電阻R1〜R4而 使分壓電路231輸出鮮健號酬關電路232控制端以控制開 關電路232不導通，此時禁能信號未傳送到調光電路&而實現調 光電路25收到開啟彳§號on。因此，可通過選擇不同崩潰電壓的齊 納-極體ZD1來改變過壓期望值的設計，即相當於設計當燈串中 有多少個發光二極體短路時才輸出關閉信號〇FF。 圖5為圖2所示電壓補償電路24的一電路實施例。請參照圖 5，電壓補償電路24包括二極體D21〜D2m、定電壓源241、分壓 電路242、正端電阻R8、負端電阻R7、運算放大器〇p2、開關電 路243及並聯電阻R12。每個二極體D2i的陰極端耦接至相應的燈 串li的第二端ΡΠ，每個二極體D2i的陽極端耦接至運算^大器 0P2的反相輸入端，定電壓源241輸出定電壓v〇,定電壓v〇通過 分壓電路242分壓產生設定電壓Vset2 ’正端電阻欣的第一端麵 接至为壓電路242以接收設定電壓Vset2，正端電阻耶的第一端 耦接至運算放大器0P2的非反相輸入端，負端電阻的第一端耦 接至定電壓源241以接收定電壓Vo,負端電阻R7的第二端搞接至 運算放大器0P2的反相輸入端，運算放大器〇P2的輪出端耦接至 開關電路243的控制端，開關電路243的第一端麵接至dc/dc轉 換器21的回授端而可調整回授信號FB，開關電路243的第二端輕 接至並聯電阻R12的第一端，並聯電阻R12的第二端輕接至接地。 在本例中’電壓期望值為設定電壓Vset2減去二極體D2i的順向 導通電壓。 另外，定電壓源241包括電阻R1〜R4、第一型開關Q1、並聯 201123974 穩，器TL1及電容Cl、C2，其中電阻則〜以、開關及並聯穩 壓器TL1構成的電路輪出定電壓Vo=(l+R3/R4)xVref，Vref為並 聯穩壓器TL1用於和參考端R電壓比較的内部參考電壓㈣，而 電容C卜C2用於穩壓濾波。分壓電路242包括電阻R5、R6及電 今C3 ’其中電阻R5、R6用於分壓以產生設定電壓Vset2=R6/(R5+R6) xVo,而電容C3用於穩壓濾波。開關電路243包括二極體兕卜電 P^RIO、R^、電容C4及第一型開關Q2，其中二極體⑽丨用於使 ^只可單向傳送’電阻R1G、R11驗將運算放A||()p2輸出的 籲錢分壓以轉換為適當準位的電壓信號來控制第一型開關Q2導通 或不導通，電容C4用於穩壓濾波。 正端電阻R8、負端電阻R7及運算放大器〇p2即可構成一般的 比較器，此時運算放大器〇P2可以比較器取代。但是，在本例中 還加入回授電阻R9，回授電阻四的第一端祕至運算放大器〇p2 的非反相輸入端，回授電阻R9的第二端耦接至運算放大器〇p2的 輸出端’因此正端電阻欣、負端電阻R7、運算放大器〇p2及回授 電阻R9構成遲滞比較器，可有效避免雜訊干擾。 • 當檢測到任一燈串的第二端的電壓小於電壓期望值時，檢測 電壓Vdect小於設定電壓vset2，運算放大器〇P2輸出高準位信號 控制開關電路243 (或第-型開關Q2)導通，此時並聯電阻則2°將 和DC/DC轉換器21的控制器的回授端所耦接的電阻並聯而降低回 授端所耦接的電阻的整體電阻值，使得控制器從回授端收到的回 授信號FB必然小於預設值，因此控制器會調高燈串電壓。當 未檢測到任一燈串的第二端的電壓小於電壓期望值時，檢測電& Vdect不小於設定電壓Vset2，運算放大器〇p2輸出低準位信 制開關電路243 (或第-型關Q2)不導通，此時電壓補償電口路^ 不影響DC/DC轉換器21的控制器從回授端收到的回授信號FB，因 201123974 此不會影響DC/DC轉換器21輸出的燈串電壓vbus。 圖6為圖2所示調光電路25的一電路實施例。請參照圖6， 調光電路25包括第一開關電路251、第二開關電路252及第三開 關電路253，第一開關電路251的第一端251】接收調光信號麵， 第一開關電路251的第二端2512耦接至第二開關電路252的控制 端2523 ’第-開關電路251的控制端2513耗接至短路保護電路 2&3以接收關閉信號〇FF或開啟信號〇N，第二開關電路252的第一 端2521麵接至第三開關電路253的控制端2533，第二開關電路 252的第二端2522健至低準位信號(在本例中利用接地提供低 準位信號），第三開關電路253的第一端2531柄接至高準位信號 (在本例中利用直流顏Vcc提供高準位信號），第三開關電路踟 的第二端2532輸出控制信號VC0N’其中第二開關電路脱的控制 端2523及第三開關電路253的控制端2533在未收到信號輸入時 均不導通’且在第三開關電路253不導通時控制信號聰為低準 位信號。需要注意的是，第—_電路251因包括第—型開_ 而為第-型開關電路’第二開關電路252因包 為第-型開關電路，第三開關電路253因包括第 ^^ 第二型開關電路。 *玉開關㈨而為 當第一開關電路251的控制端2513收到關 低準位信號）時’第-開關電路251不導通，因 ^ 輸入。第二開關電路252的控制端2523因A打仏韻 邱雷阳R以苴減兔帝、 為沒收到信號而通過内 抑R5 (，、跨壓為零)接收到低準位信號，故第二 π 不導通。第三開關電路253的控制端也 過内部電阻R6接收到高準位信號，故第三_路1^=通 此時調光電路25的輸出端（即第三開關電路25 通過内部電阻_輕树)域， 14 201123974 VC0N為低準位信號以控制調節器22〗〜22m不動作。 當第-開關電路251的控制端2513收到開啟信號〇N (其為高 準位信號)時’第-關電路251導通，因此有調光信號顧輸入。 第-開關電路252的控制端2523收到調光信號疆，在調光信號 DIM的致能期間（其為高準位信號)時，第二開關電路脱導通而將 低準位信號(其為接地)傳送到第三開關電路253的控制端2533， 使知第二開關電路253導通祕高準位信號(其為直流電遷⑽ 傳送到調光 25輸出端，因此㈣錢聰為高準位信號以As with the operation of Fig. 3A, the transistor milk soil operates in the cut-off region when the regulator 22i is not operating. When the regulator 22i is actuated, the transistor QH operates in the linear region and the regulator 22i detects the corresponding lamp string u current and compares it with the expected current value 'so that the current in the string li is greater than the expected value (ie, the crossover voltage of the sense resistor such as When the voltage is set to Vsetl), the output terminal of the operational amplifier 〇ρι outputs a low level. (4) The operating point of the control transistor Qh is close to the cut-off region to make the current of the string Η small; and the current in the string li is smaller than the current expected value ( That is, when the voltage of the detecting resistor is less than the set voltage Vset1), the output terminal of the operational amplifier 〇P1 outputs a high level to control the operating point of the transistor Qli away from the cut-off region to increase the current of the lamp string u. 4 is a circuit example 4 of the short circuit protection circuit 23 shown in FIG. 2. The short circuit protection circuit 23 includes a diode D11~_, a Zener diode zdi: a circle = 31: a circuit. The anode end of each diode DU is coupled to the second phase Ph of the string h; the cathode end of each diode Dli is switched to the cathode end of the Zener diode ZD1, Zener diode The anode end of the body ZD1 is lightly connected to 23i, the first end of the switch circuit 232 is lightly connected to the dimming circuit 25, and the second end of the = is connected to the forbidden money (in this case, the grounding is provided with a low level. The voltage circuit 231 includes electric mR1 to R4 and a capacitor C1, wherein R4 is used for voltage division, and capacitor C1 is used for voltage regulation chopping. Switching circuit = switch Q1', so switching circuit 232 is a first type switching circuit. The first name of a light string is called ... Wang Ba...When the value is present, the Zener II does not collapse ZD1'. The voltage divided by the voltage divider circuit 231 will fall to the appropriate level of the voltage of the resistors R1 to R4. The bit field is connected to the control terminal of the switch circuit 232 to control the switch circuit 232 to be turned on. At this time, the disable signal is transmitted to the dimming circuit 25, and the dimming circuit 25 receives the OFF signal OFF. The second end of the string is not detected. When the voltage is greater than the expected value of the overvoltage, the Zener diode ZD1 does not collapse, and no voltage falls on the resistors R1 to R4 to cause the voltage dividing circuit 231 to output. The control terminal 232 controls the switch circuit 232 to be non-conducting, and the disable signal is not transmitted to the dimming circuit & and the dimming circuit 25 receives the opening 彳 § on. Therefore, the selection can be different. The Zener-polar body ZD1 of the breakdown voltage is used to change the design of the overvoltage expectation value, which is equivalent to designing the shutdown signal 〇FF when there is a short circuit in the light string. Figure 5 is the voltage compensation shown in Figure 2. A circuit embodiment of the circuit 24. Referring to Figure 5, the voltage compensation circuit 24 includes diodes D21 to D2m, a constant voltage source 241, a voltage dividing circuit 242, a positive terminal resistor R8, a negative terminal resistor R7, and an operational amplifier 〇p2. a switching circuit 243 and a parallel resistor R12. The cathode end of each diode D2i is coupled to the second end 相应 of the corresponding string li, and the anode end of each diode D2i is coupled to the operation unit OP2 In the inverting input terminal, the constant voltage source 241 outputs a constant voltage v〇, and the constant voltage v〇 is divided by the voltage dividing circuit 242 to generate a set voltage Vset2. The first end surface of the positive terminal resistance is connected to the voltage circuit 242 for receiving. Setting the voltage Vset2, the first end of the positive terminal resistor is coupled to the operational amplifier The non-inverting input terminal of the transistor 0P2, the first end of the negative terminal resistor is coupled to the constant voltage source 241 to receive the constant voltage Vo, and the second end of the negative terminal resistor R7 is connected to the inverting input terminal of the operational amplifier OP2. The output terminal of the operational amplifier 〇P2 is coupled to the control end of the switch circuit 243, and the first end surface of the switch circuit 243 is connected to the feedback end of the dc/dc converter 21 to adjust the feedback signal FB, and the switch circuit 243 The second end is lightly connected to the first end of the shunt resistor R12, and the second end of the shunt resistor R12 is lightly connected to the ground. In this example, the voltage expectation value is the set voltage Vset2 minus the forward voltage of the diode D2i. In addition, the constant voltage source 241 includes resistors R1 R R4, a first type switch Q1, a parallel circuit 201123974, a device TL1, and capacitors C1 and C2, wherein the resistors are connected to a circuit wheel formed by a switch and a shunt regulator TL1. Vo=(l+R3/R4)xVref, Vref is the internal reference voltage (4) used by the shunt regulator TL1 for comparison with the reference terminal R voltage, and the capacitor CbC2 is used for voltage stabilization filtering. The voltage dividing circuit 242 includes resistors R5, R6 and a current C3' where the resistors R5, R6 are used to divide the voltage to generate a set voltage Vset2 = R6 / (R5 + R6) xVo, and the capacitor C3 is used for voltage stabilization filtering. The switch circuit 243 includes a diode body P^RIO, R^, a capacitor C4, and a first type switch Q2, wherein the diode (10) is used to enable the unidirectional transmission of the resistors R1G and R11. The A||() p2 output is divided into voltage signals to be converted to an appropriate level to control whether the first type switch Q2 is turned on or off, and the capacitor C4 is used for voltage stabilization filtering. The positive terminal resistor R8, the negative terminal resistor R7 and the operational amplifier 〇p2 form a general comparator. At this time, the operational amplifier 〇P2 can be replaced by a comparator. However, in this example, a feedback resistor R9 is added, and the first end of the feedback resistor 4 is secreted to the non-inverting input terminal of the operational amplifier 〇p2, and the second end of the feedback resistor R9 is coupled to the operational amplifier 〇p2. The output terminal 'so positive-side resistor hin, negative-side resistor R7, operational amplifier 〇p2 and feedback resistor R9 form a hysteresis comparator, which can effectively avoid noise interference. • When it is detected that the voltage of the second end of any of the strings is less than the voltage expected value, the detection voltage Vdect is less than the set voltage vset2, and the operational amplifier 〇P2 outputs the high level signal to control the switch circuit 243 (or the first-type switch Q2) to be turned on. The parallel resistance of 2° will be connected in parallel with the resistance coupled to the feedback terminal of the controller of the DC/DC converter 21 to reduce the overall resistance value of the resistor coupled to the feedback terminal, so that the controller receives the feedback from the feedback terminal. The feedback signal FB to which it arrives must be less than the preset value, so the controller will increase the string voltage. When it is not detected that the voltage of the second end of any of the strings is less than the voltage expected value, the detection electric & Vdect is not less than the set voltage Vset2, and the operational amplifier 〇p2 outputs the low level signal switching circuit 243 (or the first type Q2) If the voltage is not turned on, the voltage compensation circuit 2 does not affect the feedback signal FB received by the controller of the DC/DC converter 21 from the feedback terminal. This does not affect the output of the DC/DC converter 21 due to 201123974. Voltage vbus. FIG. 6 is a circuit embodiment of the dimming circuit 25 of FIG. 2. Referring to FIG. 6 , the dimming circuit 25 includes a first switch circuit 251 , a second switch circuit 252 , and a third switch circuit 253 . The first end 251 of the first switch circuit 251 receives the dimming signal surface, and the first switch circuit 251 The second terminal 2512 is coupled to the control terminal 2523 of the second switch circuit 252. The control terminal 2513 of the first switch circuit 251 is connected to the short circuit protection circuit 2 & 3 to receive the turn-off signal 〇FF or the turn-on signal 〇N, and second The first end 2521 of the switch circuit 252 is connected to the control terminal 2533 of the third switch circuit 253, and the second end 2522 of the second switch circuit 252 is activated to a low level signal (in this example, the ground is used to provide a low level signal). The first end 2531 of the third switch circuit 253 is connected to the high level signal (in this example, the DC level Vcc is used to provide a high level signal), and the second end 2532 of the third switch circuit 输出 outputs the control signal VC0N'. The control terminal 2523 of the switch circuit and the control terminal 2533 of the third switch circuit 253 are not turned on when no signal input is received, and the control signal is a low level signal when the third switch circuit 253 is not turned on. It should be noted that the first-type circuit 251 is a first-type switching circuit because the first-type switching circuit 252 includes a first-type switching circuit, and the third switching circuit 253 includes a second-type switching circuit. Type 2 switch circuit. * Jade switch (9). When the control terminal 2513 of the first switch circuit 251 receives the low level signal), the first switch circuit 251 is not turned on, because of the ^ input. The control terminal 2523 of the second switch circuit 252 receives the low-level signal through the internal suppression R5 (,, the cross-voltage is zero) due to the smashing of the rhyme Qiu Leiyang R to reduce the rabbit emperor. Two π is not conducting. The control terminal of the third switch circuit 253 also receives the high level signal through the internal resistor R6, so the third path 1^=passes the output end of the dimming circuit 25 at this time (ie, the third switch circuit 25 passes the internal resistance _ light Tree) field, 14 201123974 VC0N is a low level signal to control the regulator 22 〜 22m does not operate. When the control terminal 2513 of the first-switch circuit 251 receives the turn-on signal 〇N (which is the high-level signal), the first-off circuit 251 is turned on, so that there is a dimming signal. The control terminal 2523 of the first-switch circuit 252 receives the dimming signal. When the dimming signal DIM is enabled (which is a high-level signal), the second switching circuit is turned off to turn the low-level signal (which is The grounding is transmitted to the control terminal 2533 of the third switching circuit 253, so that the second switching circuit 253 is turned on to the secret high level signal (which is the DC current (10) transmitted to the output of the dimming 25, so (4) Qian Cong is a high level signal. Take
控制調節II 221〜22m動作；而在調光信號應的禁能期間（其為 低準位信號）時’第二開關電路252不導通，第三開關電路253的 控制端25抑因為沒收到信號而通過内部電阻R6接收到高準位作 號丄故第三開關電路253不導通，此時調光電路25的輸出端（/p 第二開關電路253的第二端2532)通過内部電阻R8 (並跨壓為零〉 ，收到低雜錄，因此㈣廳v⑽為鱗健號啸制調節 器221〜22m不動作。 綜上所述，本發明的LED驅動電路在每個燈串的第二端 電流平衡器以進行自我回授控制來調整燈串各自流過的電流，且 力口入電壓補電额婦串電壓續使具林同順向導 :個料魏被完全點亮，壯人贿保護電路讀在燈串中^ 極路咖閉⑽驅_路，以保護燈串不致於因過電 本發明的卿跑不需要採用專用的 制盗’且驅動電路架構相當簡單，可大幅降低成本。 Μ雖已以較佳實施例揭露如上，財並_於限定本 可作料IΜ技藝者’在不脫離本發明之精神和範圍内，當 專===:，祕嫩贿__之申請 15 201123974 【圖式簡單說明】 圖1為一種現有的LED驅動電路的電路圖。 圖2為依照本發明一較佳實施例的發光二極體驅動電路的方 塊圖。 圖3A及圖3B均為圖2所示電流平衡器的電路實施例。 圖4為圖2所示短路保護電路23的一電路實施例。 圖5為圖2所示電壓補償電路24的一電路實施例。 圖6為圖2所示調光電路25的一電路實施例。 【主要元件符號說明】 11〜lm :燈串 2 : LED驅動電路 21 : DC/DC轉換器 22 :電流平衡電路 221〜22m、22i :調節器 23 :短路保護電路 231 :分壓電路 232 :開關電路 24 :電壓補償電路 241 :定電壓源 242 :分壓電路 243 :開關電路 25 :調光電路 251 :第一開關電路 2511 :第一端 2512 :第二端 2513 :控制端 252 :第二開關電路 2521 :第一端 2522 :第二端 2523 :控制端 253 :第三開關電路 2531 :第一端 2532 :第二端 201123974 2533 :控制端 C1〜C4 :電容 0P1、0P2 :運算放大器 D1〜Dn :發光二極體 D11 〜Dlm、D21 〜D2m、D31 : 二極體 Ml〜Mm、Q1〜Q3 :開關 Q11〜Qlm、Qli :電晶體 R1〜R12 :電阻 Rbi :限流電阻 Rsl〜Rsm、Rsi :檢測電阻 TL1、TLi :並聯穩壓器 ZD1 :齊納二極體 A :陽極端 ® K:陰極端 R :參考端 CH1〜CHm :通道端 IS1〜ISm :電流檢測端 VD1〜VDm :電壓檢測端 P11〜Plm、Pli :燈串的第二端 FB :回授信號 DIM :調光信號 OFF :關閉信號 0N :開啟信號 VC0N :控制信號 Vbus :燈串電壓 φ Vcc、Vdc :直流電壓 Vdect :檢測電壓 Vo :定電壓 Vsetl、Vset2 :設定電壓 17Control regulation II 221~22m action; while the dimming signal should be disabled during the disable period (which is a low level signal), the second switch circuit 252 is not turned on, and the control terminal 25 of the third switch circuit 253 does not receive the signal. The third switch circuit 253 is not turned on by the internal resistor R6. The output end of the dimming circuit 25 (/p the second end 2532 of the second switch circuit 253) passes through the internal resistor R8 ( And the cross pressure is zero>, and the low miscellaneous record is received, so (4) the hall v(10) is not operated for the scale health whistle regulator 221~22m. In summary, the LED drive circuit of the present invention is in the second of each light string. The terminal current balancer adjusts the current flowing through the lamp string by self-return control, and the voltage of the force input voltage is increased by the voltage of the string. The Lin Weishun guide is completed: the material Wei is completely lit, and the strong bribe protects the circuit. Read in the light string ^ pole road coffee (10) drive _ road, to protect the light string from over-powered, the invention does not need to use a dedicated thief and drive circuit architecture is quite simple, can significantly reduce costs. Although the above has been disclosed in the preferred embodiment, The invention can be made by the skilled person without departing from the spirit and scope of the present invention. When the application is ===:, the secret bribe __ application 15 201123974 [Simplified illustration] Figure 1 is a circuit diagram of a conventional LED driving circuit Figure 2 is a block diagram of a light-emitting diode driving circuit in accordance with a preferred embodiment of the present invention. Figures 3A and 3B are circuit embodiments of the current balancer of Figure 2. Figure 4 is a short circuit of Figure 2. A circuit embodiment of the protection circuit 23. Fig. 5 is a circuit embodiment of the voltage compensation circuit 24 shown in Fig. 2. Fig. 6 is a circuit embodiment of the dimming circuit 25 shown in Fig. 2. [Explanation of main component symbols] 11 ~lm : string 2 : LED drive circuit 21 : DC/DC converter 22 : current balance circuit 221 to 22m, 22i : regulator 23 : short circuit protection circuit 231 : voltage divider circuit 232 : switch circuit 24 : voltage compensation circuit 241: constant voltage source 242: voltage dividing circuit 243: switching circuit 25: dimming circuit 251: first switching circuit 2511: first end 2512: second end 2513: control terminal 252: second switching circuit 2521: first Terminal 2522: second end 2523: control terminal 253: third switching circuit 2531: first terminal 2532: second terminal 201123974 2533: control terminal C1 to C4: capacitors 0P1, 0P2: operational amplifiers D1 to Dn: light-emitting diodes D11 to Dlm, D21 to D2m, D31: diodes M1 to Mm Q1~Q3: Switch Q11~Qlm, Qli: Transistor R1~R12: Resistor Rbi: Current limiting resistors Rsl~Rsm, Rsi: Sense resistors TL1, TLi: Shunt regulator ZD1: Zener diode A: Yang Extreme® K: Cathode terminal R: Reference terminal CH1~CHm: Channel terminal IS1~ISm: Current detection terminal VD1~VDm: Voltage detection terminal P11~Plm, Pli: Second end of the string FB: Feedback signal DIM: Tune Optical signal OFF: Off signal 0N: On signal VC0N: Control signal Vbus: String voltage φ Vcc, Vdc: DC voltage Vdect: Detection voltage Vo: Constant voltage Vsetl, Vset2: Set voltage 17