TW200934293A

TW200934293A - LED dimming control circuit

Info

Publication number: TW200934293A
Application number: TW97101891A
Authority: TW
Inventors: Chien Shang-Yu Chang; Tien-Tzu Chen
Original assignee: Global Mixed Mode Technology Inc
Priority date: 2008-01-18
Filing date: 2008-01-18
Publication date: 2009-08-01

Abstract

A LED dimming control circuit is used to drive a LED. The LED dimming control circuit comprises an inductor, a transistor, a dimming control signal, a feedback signal, a switching control circuit, an error amplifier, and an inverted amplifier. The switching control circuit is controlled by the dimming control signal and the feedback signal. The transistor is controlled by the switching control circuit. The output terminal and the non-inverted terminal of the error amplifier form a negative feedback path via the inverted amplifier.

Description

200934293 九、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調光控制電路，尤其關於一種可防止電感之湧入電流過大且避免輸出電壓過高之發光二極體調光控制電路。【先前技術】圖1顯示習知的發光二極體調光控制電路100之電路圖。在圖1的例子中，發光二極體調光控制電路1〇〇係由一升壓式（Boost-Type)電壓調節器所實施，用以將輸入電壓Vinl轉換成所期望的輸出電壓V(>1，進而驅動發光二極體19。切換控制電路10包含一電容Cll、一電阻Rll、一比較器13、一震盪電路14、一電流對電壓轉換器15、一閃鎖器16、一電流感測器17、及一驅動電路丨8。電阻Ri2 之一端與發光二極體19之陰極端之耦合點提供一電壓作為回授信號V fb 1。切換控制電路1 〇回應於一調光控制信號CN1、回授信號Vfbl、及電感L1之電流用以控制電晶體T1。使用者可藉由改變調光控制信號cni來調整發光二極體19之明暗程度。錯誤放大器12比較參考電壓Vri 與回授信號vfbl用以產生一輸出電流Ie〇i至切換控制電路 10。當調光控制信號CN1為高位準時，發光二極體調光控制電路100係操作於正常升壓模式，此時電感Li之峰值電流係受輸出電流ie()1所控制。當調光控制信號CN1為低位準時，發光二極體調光控制電路1〇〇停止切換，此時輸 5 200934293 出電壓V〇i下降’導致回授信號Vfbl下降且輸出電流上升。而當調光控制信號CN1由低位準轉換成高位準時，電感L1之湧入電流將會過大，因而造成輸出電壓¥〇1過高。【發明内容】有鑑於前述問題，本發明之目的在於提供—種發光二 ◎ 極體調光控制電路，可防止電感之湧入電流過大且避免輸出電壓過高。依據本發明之態樣，一種發光二極體調光控制電路用以驅動一發光二極體。發光二極體調光控制電路具有一緩啟動電路、一錯誤放大器、第一開關至第四開關、一反相器、一反相放大器、一切換控制電路、一電感、一電晶體、一一·極體。電感、電晶體、及二極體係共同輕合於一節點β 切換控制電路回應於一調光控制信號、一回授信號、及電感之電流用以控制電晶體。使用者可藉由改變調光控制传號來調整發光二極體之明暗程度。第一開關及第二開關係受調光控制信號之反相信號所控制而第三開關及第四開關係受調光控制信號所控制。第一開關耦合於錯誤放大器之輸出端與反相放大器之輸入端間；第二開關輕合於錯誤放大器之非反相輸入端與反相放大器之輸出端間；第三開關耦合於緩啟動電路之輸出端與錯誤放大器之非反相輸入端間；並且第四開關耦合於錯誤放大器之輸出端與比較器之反相輸入端間。當調光控制信號為高位準時，此時發 200934293 光二極體調光控制電路係操作於正常電流模式。當調光控制信號為低位準時’發光二極體調光控制電路停止切換，此時回授信號下降。由於錯誤放大器之輸出端與非反相輸入端經由反相放大器形成一單位增益之負回授路徑，此時錯誤放大器之非反相輸入端之電壓追隨回授信號往下降。當調光控制信號由低位準轉換成高位準時，回授信號會追隨錯誤放大器之非反相輸入端之電壓慢慢往上升，使得錯誤放大器之輸出電流不會過大。因此，電感之渴入電流不會過大，進而避免輸出電壓過高。【實施方式】下文中之說明與附圖將使本發明之前述與其他目的、特徵、與優點更明顯《茲將參照圖式詳細說明依據本發明之較佳實施例。圖2顯示依據本發明之發光二極體調光控制電路2〇〇之電路圖。在圖2的例子中，發光二極體調光控制電路200 〇係由一升壓式電壓調節器所實施，用以將輸入電壓乂化轉換成所期望的輸出電壓V。，進而驅動發光二極體29。發光二極體調光控制電路200包含一緩啟動電路21、一錯誤放大器22、開關S1至S4、一反相器30、一反相放大器 31、一切換控制電路20、. 一電感L、一電晶體T、一二極體D、一電阻R22、及一輸出電容c。，彼此柄合形成如圖所示之結構。電感L、電晶體τ、及二極體D係共同耦合於一節點N。發光二極體29之陽極端、二極體D、及輸出 7 200934293 電容c。係共同耦合於另一節點〇。電阻R22之一端與發光 Ο200934293 IX. Description of the Invention: [Technical Field] The present invention relates to a light-emitting diode dimming control circuit, and more particularly to a light-emitting diode adjustment capable of preventing an inrush current of an inductor from being excessively large and avoiding an excessive output voltage Light control circuit. [Prior Art] Fig. 1 shows a circuit diagram of a conventional light-emitting diode dimming control circuit 100. In the example of FIG. 1, the LED dimming control circuit 1 is implemented by a boost-type voltage regulator for converting the input voltage Vin1 to a desired output voltage V ( >1, and further driving the light-emitting diode 19. The switching control circuit 10 includes a capacitor C11, a resistor R11, a comparator 13, an oscillating circuit 14, a current-to-voltage converter 15, a flash lock 16, a current The sensor 17 and a driving circuit 丨 8. The coupling point of one end of the resistor Ri2 and the cathode end of the LED body 19 provides a voltage as a feedback signal V fb 1. The switching control circuit 1 〇 responds to a dimming control The currents of the signal CN1, the feedback signal Vfbl, and the inductor L1 are used to control the transistor T1. The user can adjust the brightness of the light-emitting diode 19 by changing the dimming control signal cni. The error amplifier 12 compares the reference voltage Vri with The feedback signal vfbl is used to generate an output current Ie〇i to the switching control circuit 10. When the dimming control signal CN1 is at a high level, the LED dimming control circuit 100 operates in a normal boost mode, and the inductor Li Peak current Controlled by the output current ie()1. When the dimming control signal CN1 is low, the LED dimming control circuit 1〇〇 stops switching. At this time, the output voltage of V2009 is decreased. Vfbl falls and the output current rises. When the dimming control signal CN1 is converted from the low level to the high level, the inrush current of the inductor L1 will be too large, causing the output voltage ¥〇1 to be too high. The object of the present invention is to provide a light-emitting two-pole dimming control circuit, which can prevent an inrush current of an inductor from being excessively large and avoid an excessive output voltage. According to an aspect of the invention, a light-emitting diode dimming control circuit The LED dimming control circuit has a slow start circuit, an error amplifier, first to fourth switches, an inverter, an inverting amplifier, a switching control circuit, An inductor, a transistor, a pole body, an inductor, a transistor, and a two-pole system are collectively coupled to a node β switching control circuit in response to a dimming control signal, one time The signal and the current of the inductor are used to control the transistor. The user can adjust the brightness of the light-emitting diode by changing the dimming control signal. The first switch and the second open relationship are inverted signals of the dimming control signal. The third switch and the fourth open relationship are controlled by the dimming control signal. The first switch is coupled between the output of the error amplifier and the input of the inverting amplifier; the second switch is coupled to the non-inverting of the error amplifier. The input terminal is coupled to the output of the inverting amplifier; the third switch is coupled between the output of the slow start circuit and the non-inverting input of the error amplifier; and the fourth switch is coupled to the output of the error amplifier and is inverted by the comparator When the dimming control signal is high, the 200934293 optical diode dimming control circuit operates in the normal current mode. When the dimming control signal is low, the light-emitting diode dimming control circuit stops switching, and the feedback signal drops. Since the output of the error amplifier and the non-inverting input form a negative feedback path of unity gain via the inverting amplifier, the voltage of the non-inverting input of the error amplifier follows the feedback signal. When the dimming control signal is converted from a low level to a high level, the feedback signal will follow the voltage of the non-inverting input of the error amplifier and slowly rise, so that the output current of the error amplifier is not excessive. Therefore, the inductor's thirst into the current will not be too large, thus avoiding the output voltage is too high. The above and other objects, features and advantages of the present invention will become more apparent from the aspects of the appended claims. Fig. 2 is a circuit diagram showing a light-emitting diode dimming control circuit 2A according to the present invention. In the example of Figure 2, the LED dimming control circuit 200 is implemented by a boost voltage regulator for converting the input voltage to a desired output voltage V. In turn, the light-emitting diodes 29 are driven. The LED dimming control circuit 200 includes a slow start circuit 21, an error amplifier 22, switches S1 to S4, an inverter 30, an inverting amplifier 31, a switching control circuit 20, an inductor L, and a The transistor T, a diode D, a resistor R22, and an output capacitor c. They are ligated to form a structure as shown in the figure. The inductor L, the transistor τ, and the diode D are coupled together at a node N. The anode terminal of the LED 29, the diode D, and the output 7 200934293 capacitor c. The system is commonly coupled to another node. One end of the resistor R22 and the light Ο

二極體29之陰極端之耦合點提供一電壓作為回授信號 Vfb’其中回授信號Vfb耗合於錯誤放大器22之反相輸入端。切換控制電路20回應於一調光控制信號CN、回授信號Vfb、及電感L之電流用以控制電晶體τ。使用者可藉由改變調光控制信號CN來調整發光二極體29之明暗程度。此外，切換控制電路20更包含一電容C21、一電阻 Rn、一比較器23、一震盪電路24、一電流對電壓轉換器 25、一閂鎖器26、一電流感測器27、及一驅動電路28。開關S 1及S2係受調光控制信號CN之反相信號α所控制而開關S3及S4係受調光控制信號CN所控制。開關s j 耦合於錯誤放大器22之輸出端與反相放大器31之輸入端間；開關S2耦合於錯誤放大器22之非反相輸入端與反相放大器31之輸出端間；開關S3耦合於緩啟動電路21之輸出端與錯誤放大器22之非反相輸入端間；並且開關“ 麵合於錯誤放大器22之輸出端與比較器23之反相輸入端备調光控龍號™為高位準時，_SUS2不導 =關S3及S4導通，此時發光二極體調光控制電路2〇〇 :操=正常電流模式。驅動電路28根據問鎖器％之輸出心號用以控制電晶體端之雷蔽v & 鯖誤放大器22比較非反相輸入電壓vp與回授信號Vfb用以 c2丨進杆翰出電流以對電容電，其中電阻R21與電容C21形成— 震盪電路24施加一固定頻率肌衝彳0鈮至閂鎖器20之設 8 200934293 定端S用以導通電晶體τ。一旦電晶體τ導通，流經電感 L之電流會開始增加。此外，電流感測器27產生一電流 Is至電流對電壓轉換器25，其中電流ls係正比於電感l 之電流。電流對電壓轉換器25接收電流Is用以產生一輸出電壓Vs至比較器23之非反相輸入端。當輸出電壓vs 超過比較器23之反相輸入端之電壓~時，比較器23即觸發閂鎖器26之重置端r使得電晶體τ不導通。 ΟThe coupling point of the cathode terminal of the diode 29 provides a voltage as a feedback signal Vfb' in which the feedback signal Vfb is consumed by the inverting input terminal of the error amplifier 22. The switching control circuit 20 is responsive to a dimming control signal CN, a feedback signal Vfb, and a current of the inductor L for controlling the transistor τ. The user can adjust the brightness of the light-emitting diodes 29 by changing the dimming control signal CN. In addition, the switching control circuit 20 further includes a capacitor C21, a resistor Rn, a comparator 23, an oscillating circuit 24, a current-to-voltage converter 25, a latch 26, a current sensor 27, and a driving unit. Circuit 28. The switches S 1 and S2 are controlled by the inverted signal α of the dimming control signal CN and the switches S3 and S4 are controlled by the dimming control signal CN. The switch sj is coupled between the output of the error amplifier 22 and the input of the inverting amplifier 31; the switch S2 is coupled between the non-inverting input of the error amplifier 22 and the output of the inverting amplifier 31; the switch S3 is coupled to the slow-start circuit The output of 21 is connected to the non-inverting input of the error amplifier 22; and the switch is "closed to the output of the error amplifier 22 and the inverting input of the comparator 23 is set to the high level, _SUS2 is not Conduction = off S3 and S4 are on, at this time, the LED dimming control circuit 2: operation = normal current mode. The drive circuit 28 is used to control the lightning deflection of the transistor end according to the output heart number of the locker %. The & error amplifier 22 compares the non-inverting input voltage vp with the feedback signal Vfb for c2 to sink the current to the capacitor, wherein the resistor R21 is formed with the capacitor C21 - the oscillating circuit 24 applies a fixed frequency muscle impulse 0铌 to the setting of the latch 20 200934293 The fixed end S is used to conduct the crystal τ. Once the transistor τ is turned on, the current flowing through the inductor L starts to increase. In addition, the current sensor 27 generates a current Is to the current. Voltage converter 25, wherein the current ls is proportional to the current of the inductor 1. The current-to-voltage converter 25 receives the current Is for generating an output voltage Vs to the non-inverting input of the comparator 23. When the output voltage vs exceeds the inverse of the comparator 23. When the voltage at the phase input is ~, the comparator 23 triggers the reset terminal r of the latch 26 so that the transistor τ is not turned on.

當調光控制信號CN為低位準時，發光二極體調光控制電路200停止切換，此時輸出電壓v。下降，導致回授信號Vfb下降。此時開關S1及S2導通且開關S3及S4不導通電麗Vp不再受緩啟動電路21所控制。.由於錯誤放大^ 22之輸出端與非反相輸入端經由反相放大器31形成單位增益（Unit Gain)之負回授路徑，此時電壓Vp追隨回授信號Vfb往下降。田調光控制信號CN自低位準轉換成高位準時，緩啟動電路21輪出之參考電壓Vr係慢慢往上升，且上升至一預定電壓vA後維垃认& _ ^ m ^ 維持於此預疋電壓VA。由於開關S3導通，調光控制電路2〇〇 ::而慢慢往上升。此時發光二極體會追隨電壓V 4電流模式，回授信號^ 流不會過大。因此/ 使得錯誤放大器22之輸出電免輸出電壓V 電感L之湧入電流不會過大，進而避束V。過兩。雖然本發明業口拉. 明，應瞭解者為.、藉由較佳實施例作為例示加以說本發明不限於此被揭露的實施例。相反 9 200934293 地，本發明意欲涵蓋對於熟習此項技藝之人士而言係明顯的各種修改與相似配置。因此’申請專利範圍之範圍應根據最廣的給釋，以包容所有此類修改與相似配置。【圖式簡單說明】When the dimming control signal CN is at a low level, the light-emitting diode dimming control circuit 200 stops switching, and at this time, the voltage v is output. The drop causes the feedback signal Vfb to drop. At this time, the switches S1 and S2 are turned on and the switches S3 and S4 are not energized, and the Vp is no longer controlled by the slow start circuit 21. Since the output terminal of the error amplification 22 and the non-inverting input terminal form a negative feedback path of unit Gain via the inverting amplifier 31, the voltage Vp follows the feedback signal Vfb. When the field dimming control signal CN is converted from the low level to the high level, the reference voltage Vr of the slow start circuit 21 is slowly rising, and after rising to a predetermined voltage vA, the maintenance & _ ^ m ^ is maintained here. Pre-voltage VA. Since the switch S3 is turned on, the dimming control circuit 2 〇〇 :: and slowly rises. At this time, the light-emitting diode will follow the voltage V 4 current mode, and the feedback signal will not be too large. Therefore, the output of the error amplifier 22 is made free of the output voltage V. The inrush current of the inductor L is not excessively large, thereby avoiding the V. Over two. The present invention is not limited to the disclosed embodiments, which are to be understood by the description of the preferred embodiments. In contrast, the present invention is intended to cover various modifications and similar configurations that are obvious to those skilled in the art. Therefore, the scope of the patent application should be based on the broadest interpretation to accommodate all such modifications and similar configurations. [Simple description of the map]

圖圖路圖。 1顯示習知的發光二極體調光控制電路之電路圖。 2顯示依據本發明之發光二極體調光控制電路之電【主要元件符號說明】 100, 200 發光二極體調光控制電路 10j 20 切換控制電路 21 緩啟動電路 12, 22 錯誤放大器 13, 23 比較器〇 14, 24 震盪電路 15, 25 電流對電壓轉換器 16, 26 問鎖器 17，2 7 電流感測器 18» 28 驅動電路 19, 29 發光二極體 30 反相器 31 反相放大器Figure Figure Road diagram. 1 shows a circuit diagram of a conventional light-emitting diode dimming control circuit. 2 shows the electric power of the light-emitting diode dimming control circuit according to the present invention. [Main component symbol description] 100, 200 light-emitting diode dimming control circuit 10j 20 switching control circuit 21 slow-start circuit 12, 22 error amplifier 13, 23 Comparator ,14, 24 oscillating circuit 15, 25 current-to-voltage converter 16, 26 LOCK lock 17, 2 7 current sensor 18» 28 drive circuit 19, 29 light-emitting diode 30 inverter 31 inverting amplifier

Sl，S2, S3, S4 開關 200934293 R-llj Rl2, R21, R22 電阻Sl, S2, S3, S4 switch 200934293 R-llj Rl2, R21, R22 resistance

Cn, C21 電容 C〇l, C〇輸出電容 LI, L 電感 Tl, T 電晶體 Dl, D 二極體 Nl, N, 〇節點 _ Vrl，Vr ❹ 參考電壓 V fb l, V f b 回授信號 CN1, CN 調光控制信號Cn, C21 Capacitor C〇l, C〇 Output Capacitor LI, L Inductor Tl, T Transistor Dl, D Dipole Nl, N, 〇 Node _ Vrl, Vr ❹ Reference Voltage V fb l, V fb Feedback Signal CN1 , CN dimming control signal

Cl 調光控制信號之反相信號Inverted signal of Cl dimming control signal

Vd，V。輸出電壓 Vs, Vp, Vn 電壓 Va 預定電壓Vd, V. Output voltage Vs, Vp, Vn voltage Va predetermined voltage

Is 電流 ❹ 11Is Current ❹ 11

Claims

200934293 十、申請專利範園： 1· 一種調光控制電路，用以驅動一發光二極體，該調光控制電路包含：一電感’其中該電感流過一第一電流；一電晶體’其中該電感與該電晶體係共同耦合於一節一調光控制信號；一回授信號；一切換控制電路，其中該切換控制電路係受控於該調光控制信號及該回授信號，且該電晶體係受控於該切換控制電路；一錯誤放大器，該錯誤放大器具有一第一非反相輸入端、一第一反相輸入端、及一第一輸出端；以及一反相放大器，該反相放大器具有一第二輸入端及— 第二輸出端； Ο 其中該第一輸出端與該第一相放大器形成一負回授路徑。非反相輸入端經由該反 2.如申請專利範圍第1 體，其中該二極體之一項之調光控制電路，更包含一端耦合於該節點。200934293 X. Application for Patent Park: 1. A dimming control circuit for driving a light-emitting diode, the dimming control circuit comprising: an inductor 'where the inductor flows through a first current; a transistor' The inductor and the electro-crystal system are coupled together to a one-level dimming control signal; a feedback signal; a switching control circuit, wherein the switching control circuit is controlled by the dimming control signal and the feedback signal, and the electric The crystal system is controlled by the switching control circuit; an error amplifier having a first non-inverting input terminal, a first inverting input terminal, and a first output terminal; and an inverting amplifier, the inverse The phase amplifier has a second input terminal and a second output terminal; wherein the first output terminal forms a negative feedback path with the first phase amplifier. The non-inverting input is via the inverse 2. As in the first aspect of the patent application, the dimming control circuit of one of the diodes further includes a terminal coupled to the node.

之調光控制電路，更包含：開關耦合於該第—輸出端與該第 3 _如申請專利範圍第1項一第一開關，該第一 '一輸入端間；以及 12 200934293 一第二開關，該第二開關耦合於該第一非反相輸入端與該第一輸出端間。 4.如申請專利範圍第3項之調光控制電路，其中該第一開關及該第二開關係受該調光控制信號之一反相信號所控制。 5. 如申請專利範圍第4項之調光控制電路，更包含：一第三開關；以及一第四開關；其中該第三開關及該第四開關係受該調光控制信號所控制。 6. 如申請專利範圍第5項之調光控制電路，其中：該切換控制電路包含：一電流感測器，用以提供一第二電流，該第二電流係正比於該第一電流；一比較器，該比較器具有一第三非反相輸入端、一第三反相輸入端、及一第三輸出端，其中該第三反相輸入端執合於一補償電路；一電流對電壓轉換器，接收該第二電流，用以產生一第一電壓至該第三非反相輸入端；一震盪電路，該震盪電路具有一第四輸出端；一閂鎖器，該閂鎖器具有一重置端、一設定端、 13 200934293 及一第一輸出信號，其中該重置端輛合於該第三輪出端且該設定端耦合於該第四輸出端；以及驅動電路’根據該調光控制信镜及該第一輸出信號’用以控制該電晶體。 7. 如申請專利範圍第丨項之調光控制電路，其中該回授芦號耦合於該發光二極體之一陰極端。 " 8. 如申請專利範圍第6項之調光控制電路，更包含一緩啟動電路，其中該緩啟動電路根據一預定電麗用以產生一參考電壓，且該緩啟動電路具有一第五輸出端，其中該第五輸出端之電壓等於該參考電壓。 9. 如申請專利範圍第8項之調光控制電路，其中該第三開關耦合於該第五輸出端與該第一非反相輸入端間，且該第四開關耦合於該第一輸出端與該第三反相輸入端間。 10. 如申請專利範圍第2項之調光控制電路，其中該二極體之另一端耦合於該發光二極體之一陽極端。 11. 如申請專利範圍第1項之調光控制電路，其中該回授信號耦合於該第一反相輸入端。 12.如申請專利範圍第1項之調光控制電路，其中該切換 200934293 控制電路係受控於該第一電流The dimming control circuit further includes: a switch coupled to the first output terminal and the third _ as in the first item of the patent application scope, a first switch, the first 'one input terminal; and 12 200934293 a second switch The second switch is coupled between the first non-inverting input and the first output. 4. The dimming control circuit of claim 3, wherein the first switch and the second open relationship are controlled by an inverted signal of the dimming control signal. 5. The dimming control circuit of claim 4, further comprising: a third switch; and a fourth switch; wherein the third switch and the fourth open relationship are controlled by the dimming control signal. 6. The dimming control circuit of claim 5, wherein: the switching control circuit comprises: a current sensor for providing a second current, the second current being proportional to the first current; a comparator having a third non-inverting input, a third inverting input, and a third output, wherein the third inverting input is coupled to a compensation circuit; a current to voltage conversion Receiving the second current for generating a first voltage to the third non-inverting input terminal; an oscillating circuit having a fourth output; a latch having a weight a terminal, a set terminal, 13 200934293 and a first output signal, wherein the reset terminal is coupled to the third wheel output terminal and the set terminal is coupled to the fourth output terminal; and the driving circuit 'according to the dimming The control mirror and the first output signal ' are used to control the transistor. 7. The dimming control circuit of claim </ RTI> wherein the feedback reed is coupled to one of the cathode ends of the illuminating diode. " 8. The dimming control circuit of claim 6 further includes a slow start circuit, wherein the slow start circuit is configured to generate a reference voltage according to a predetermined voltage, and the slow start circuit has a fifth An output, wherein the voltage of the fifth output is equal to the reference voltage. 9. The dimming control circuit of claim 8, wherein the third switch is coupled between the fifth output terminal and the first non-inverting input terminal, and the fourth switch is coupled to the first output terminal And the third inverting input. 10. The dimming control circuit of claim 2, wherein the other end of the diode is coupled to one of the anode ends of the light emitting diode. 11. The dimming control circuit of claim 1, wherein the feedback signal is coupled to the first inverting input. 12. The dimming control circuit of claim 1, wherein the switching control circuit is controlled by the first current

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