201250351 六、發明說明： . 【發明所屬之技術領域】 本發明係關於一種一發光二極體（LED)驅動電壓被穩定之 背光單元及其驅動方法。 【先前技術】 通书，一液晶顯示裝置透過使用一電場控制具有介電各向異 性之液晶之光透射率來顯示一圖片。要做到這一點，液晶顯示裝 置係提供有具有一液晶單元矩陣之一液晶面板、用於驅動液晶面 板之一驅動電路、以及用於指引一光線至液晶面板之一背光單元。 近來，作為背光單元，使用一發光二極體（LED)作為一光 源之一 LED背光單元被大眾所關注，其相比於目前照射燈具有高 亮度以及低能耗之優勢。 一習知技術LED背光單元係提供有複數個LED陣列、用於 產生一驅動電壓以驅動複數個LED陣列之一電壓產生單元、用於 反饋驅動電壓至電壓產生單元用以穩定驅動電壓之一反饋電路、 以及回應來自一定時控制器之一調光訊號之用於控制一電流至 LED陣列以控制光之亮度之—調光控制單元。 在此期間，調光訊號係為具有一預設占空比之一脉衝寬度調 製訊號。但是’因献饋電路之-切換延遲引起在調光訊號從-低狀態升至一高狀態時驅動電壓輕微降落之一波紋而存在一問 題。驅動電源之這樣的一波紋影響LED驅動電流，造成亮度之缺 201250351 【發明内容】 因此，鑒於上述問題，本發明之目的在於提供一種背光單元 及其驅動方法。 本發明之一目的在於提供一種一 LED驅動電壓被穩定之背光 早元及其驅動方法。 本發明其他的優點、目的和特徵將在如下的說明書中部分地 加以闡述’並且本發明其他的優點、目的和特徵對於本領域的普 通技術人員來說，可以透過本發明如τ的說明得以部分地理解或 者可以從本發_實射得出。本發_目的和其他優點可以透 過本發明所記載的說明書和申請專利範圍中特別指Β月的結構並結 合圖式部份，得以實現和獲得。 為了獲得本發明的這些目的和其他特徵，現對本發明作具體 化和概括㈣描述^依照本發明之―方面，本㈣之實施例係提 供了一種背光單元，包含：一發光二極體（LED)陣列，係具有 複數個LED 電壓產生單元，侧於產生—驅動電壓以回應一 切換訊號驅動些LED ; —放大單元，係用於反饋驅動電壓並放大 反饋的驅動電壓以輸出-放大訊號；—穩定器，係用於穩定放大 訊號；一比較器’係用於比較放大訊號與一參考波形以施加切換 訊號至電壓產生單元；-第-切換單元，係用於回應來自一定時 控制器之一脈寬調變（PWM)調光訊號切換LED陣列之一電流； 以及一第二切換單元，係用於回應PWM調光訊號，切換來自比 較器之切換訊號。 者光單元更包含一第二切換單元，係用於回應pwM調光訊 201250351201250351 VI. Description of the Invention: The present invention relates to a backlight unit in which a driving voltage of a light emitting diode (LED) is stabilized and a driving method thereof. [Prior Art] A liquid crystal display device displays a picture by controlling the light transmittance of a liquid crystal having dielectric anisotropy by using an electric field. To achieve this, the liquid crystal display device is provided with a liquid crystal panel having a liquid crystal cell matrix, a driving circuit for driving the liquid crystal panel, and a backlight unit for guiding a light to the liquid crystal panel. Recently, as a backlight unit, a light-emitting diode (LED) is used as one of the light sources. The LED backlight unit has been attracting attention by the public, and has an advantage of high brightness and low power consumption compared to the current illumination lamp. A conventional LED backlight unit is provided with a plurality of LED arrays for generating a driving voltage to drive a voltage generating unit of a plurality of LED arrays, and a feedback driving voltage to a voltage generating unit for stabilizing a driving voltage. A circuit, and a dimming control unit for controlling a current to the LED array to control the brightness of the light, responsive to a dimming signal from a controller at a time. During this time, the dimming signal is a pulse width modulation signal having a predetermined duty ratio. However, there is a problem that the switching delay causes a slight drop in the driving voltage when the dimming signal is raised from the low state to the high state. Such a ripple of the driving power source affects the LED driving current, resulting in a lack of brightness. [0005] Accordingly, in view of the above problems, it is an object of the present invention to provide a backlight unit and a driving method thereof. SUMMARY OF THE INVENTION An object of the present invention is to provide a backlight early element in which an LED driving voltage is stabilized and a driving method thereof. Other advantages, objects, and features of the invention will be set forth in part in the description which follows. <RTIgt; </ RTI> <RTIgt; </ RTI> Other advantages, objects, and features of the invention will be apparent to those of ordinary skill in the art Understand or can be derived from the _ real shot. The present invention and other advantages can be realized and obtained by the structure of the present invention and the combination of the drawings in the specification and the claims of the present invention. In order to achieve these and other features of the present invention, the present invention will be embodied and summarized. (IV) Description In accordance with the aspects of the present invention, the embodiment of the present invention provides a backlight unit comprising: a light emitting diode (LED) Array having a plurality of LED voltage generating units, side generating a driving voltage in response to a switching signal to drive the LEDs; and an amplifying unit for feeding back the driving voltage and amplifying the feedback driving voltage to output-amplify the signal; a stabilizer for stabilizing the amplified signal; a comparator for comparing the amplified signal with a reference waveform to apply a switching signal to the voltage generating unit; and a - switching unit for responding to one of the controllers from the timing A pulse width modulation (PWM) dimming signal switches one of the LED array currents; and a second switching unit is responsive to the PWM dimming signal to switch the switching signal from the comparator. The light unit further includes a second switching unit for responding to the pwM dimming message 201250351
•-W 號在放大單元和穩定器兩者之間切換。 : 進一步’一背光單元包含：一 LED陣列，係具有複數個LED ; -電壓產生單70 ’伽於產生-驅動電壓以喊-切換訊號驅動 些LED，-放大單元’係用於反饋驅動電壓並放大反饋的驅動電 壓以輸出一放大訊號；一穩定器，係用於穩定放大訊號；一比較 器，係用於比較放大訊號與一參考波形以施加切換訊號至電壓產 生單元；一第一切換單元，係用於回應來自一定時控制器之一 PWM調光訊號切換LED陣列之一電流；以及一第二切換單元， 係用於回應PWM調光訊號，在放大單元和穩定器之間切換。 第一切換單元、第二切換單元、第三切換單元在PWM調光 訊號之一高週期被打開，以及在PWM調光訊號之一低週期被關 閉。 參考波形具有一三角波形。 一種用於驅動一背光單元之方法，此方法包含：回應一切換 訊號產生一驅動電壓以驅動一 LED陣列；分配並反饋驅動電壓， 並放大反饋的驅動電壓以產生一放大訊號；穩定放大訊號；回應 一 PWM調光訊號，控制LED陣列之一電流；比較放大訊號與一 參考波形以產生切換訊號；以及回應PWM調光訊號切換切換訊 號0 進一步，一種用於驅動一背光單元之方法，方法包含：回應 一切換訊號產生一驅動電壓以驅動一 LED陣列；分配並反饋驅動 電壓，並放大反饋的驅動電壓以產生一放大訊號；穩定放大訊號； 回應一 PWM調光訊號，控制LED陣列之一電流；比較放大訊號 201250351 ” ’考絲以產生鳩峨；以及喊PWM調光訊號切換放 大訊號以不穩定放大訊號。 要瞭解的是本發明之上文综述和下文細節描述之兩者係為示 例的以及轉性的’並賴提供如權項之本判之進—步解釋。 【實施方式】 現在將詳細參考在關t被闡述之示例之本發明之特定實施 例無’那種可此性，整個圖示中相同的參考標號將被使用以參 考相同或類似部件。 在下文中，本發明之背光單元之實施例和用於驅動背光單元 之方法將參考附圖而被詳細描述。 在此期間，依照本發明之—實酬之背光單元具有應用至此 之-LED作為用於指引—光至—液晶面板之—光源。在背光單元 中’儘管取決於光源之—位置而具有—直下式和—邊緣式，但本 發明不限於此。 第1圖」係為依照本發明之一實施例之一背光單元之電路 圖。 參考「第1圖」’背光單元包含：被劃分為複數個通道比之 一 LED陣列1〇，每個通道具有複數個LED ;回應於一切換訊號， 用於驅動複數個led以產生一驅動電壓vied之一電壓產生單元 40 ;用於分配驅動電壓Vled，產生一反饋電壓FB，差動放大此反 饋電壓FB以產生-放大訊號之一放大單元5〇 ;用於穩定從放大 單兀50所輸出之放大訊號之一穩定器60 ;用於比較從放大單元 50所輸出之放大訊號與一參考訊號（一三角波形訊號）以透過切 201250351 換電壓產生單元4G之-第-切換農置们控制—led陣列之一電 流之-比較器30 ;回應於從—料控制器（未示出）所輸出之一 PWM調光訊號用於切換LED陣列1〇之電流之一第一切換單元 SWi ;以及回應於從定時㈣器所輸出之卩侧調光訊號用於切 換從比較ϋ 30所輸出之切換峨之—第二峨單元sw2。 儘管未在圖中被示出，驗感應—電流之—檢測電阻可以被 包含在第一切換裝置T1和接地_兩者之間。 LED陣列1〇包含複數個通道ch，每個通道具有串聯連接之 至少兩個LED。儘管「第！圖」闡述一個通道，包含在Lm)陣列 中之通道ch之數量不被限定。led被配置以發射一白光線至液晶 面板。但是’取決於情況，LED可以被配置以發射紅色（R)、綠 色（G)和藍色（B)光之任意一種。 電壓產生單元40包含一感應器L、一第一切換裝置丁丨、一二 極體D以及一第一電容（：卜電壓產生單元4〇透過感應器L、二 極體D以及第一電容(:丨之共振產生一直流電流（DC)電壓。換 言之’第一切換裝置T1回應與從比較器30所輸出之一切換訊號 之占空比而被切換，以將一輸入電壓Vin切換為具有一恒定位準 之DC驅動電壓vied，以及提供切換的驅動電源vied至LED陣 列10。在此期間，二極體D阻止被提供至LED陣列之電流沿反 向流動，以及第一電容C1穩定驅動電壓Vied。放大單元50依照 第一電阻R1和第二電阻R2之一電阻比率分配驅動電壓vied以產 生反饋電壓FB。在此情況下，反饋電壓FB被提供至差動放大器 20上。差動放大器2〇放大在反饋電壓FB和參考電壓vref兩者之 201250351 間之一差值，並輸出此放大的差值。要做到這一點，差動放大器 2〇具有接收反饋電壓FB之一反向輸入終端，以及用於接收參考 電壓Vref之一非反向輸入終端。換言之，假設在反饋電壓FB和 參考電壓Vref之間之差值變得更高，放大電路5〇輸出具有高電勢 之一訊號，假設此差值變得更低，則輸出具有低電勢之一訊號。 穩定器60包含-第二電容C2、-第三電容C3和一第三電阻幻。 比較器30比較從差動放大器20所輸出之差動訊號與一參考 波形Ramp以產生切換訊號。要做到這一點，比較器3〇具有用於 接收參考波形Ramp之一反向輸入終端，以及用於接收從差動放 大器20所輸出之差動訊號之一非反向輸入終端。儘管，在實施例 中’參考波形Ramp具有一三教波形，但是不限於此。 在此期間，從比較器30所輸出之切換訊號係為具有一預設占 空比之一 PWM訊號。在細節上，切換訊號隨著比較器3〇之比較 操作而變化如下。 換言之，如果從差動放大器20所輸出之放大訊號具有比參考 波形Ramp之放大訊號更高之電勢，比較器3〇輸出具有高位準之 切換訊號。如果從差動放大器20所輸出之放大訊號具有比參考波 形Ramp之放大訊號更低之電勢，比較器3〇輸出具有低位準之切 換訊號。這裡，如果在從差動放大器20所輸出之放大訊號具有比 從參考波形Ramp所輸出之放大訊號更高之電勢之時間變得更長 時，切換訊號之占空比增加。但是，如果在從差動放大器2〇所輸 出之放大訊號具有比從參考波形Ramp所輸出之放大訊號更高之 電勢之時間減少時，切換訊號之占空比變小。 201250351 ~ ^ . 因此，電壓產生單元4〇透過使用具有不同占空比之切換訊號 * 維持驅動電壓Vied恒定。 如之前所描述，放大單元5〇透過使用反饋電壓FB用以維持 驅動電壓Vied恒定。 假设「第1圖」之背光單元不包含第二切換單元SW2 ,下面 的弊端可能出現。 即，從定時控制器所提供之一PWM調光訊號以固定的間隔 重複一低狀態和一高狀態。在PWM調光訊號之一高週期，第一 切換單元SW1被打開以產生用於LED陣列1〇之一驅動電流。在 PWM調光訊號之一低週期，第一切換單元SW1被關閉而不產生 用於LED陣列10之驅動電流。 依照此’既然在PWM調光訊號之低週期中，在LED陣列1〇 上ί又有負載，以及由於後來所提及之延遲效應，驅動電壓Vied則 在電壓產生單元40之一輸出終端上升。如果驅動電壓乂丨以因此 上升，反饋電壓FB也上升，引起差動放大器2〇轉發具有低電勢 之訊號。 因此，如果差動放大器20在PWM調光訊號之低週期，輸出 具有低電勢之放大訊號，穩定器60之第二電容C2被放電。 在此期間’隨著第二電容C2被充電之時間，延遲係發生，這 是因為如之前所描述當放大單元50放大並輸出在反饋訊號和參考 訊號之差值時，在PWM調光訊號之低週期中被放電之第二電容 C2被充電，，在此時間點PWM調光訊號從低狀態上升至高狀態。 因此，從差動放大器20所輸出之訊號係與延遲晚一樣多時間而被 11 201250351 提供至比較器30。 延遲之產生引起驅動電源Vied之波紋。這將詳細被描述。 「第2圖」係示出假設「第i圖」之背光單元不包含第二切 換單元時用於描述在一放大單元50和一比較器3〇發生的延遲之 波形。 「第3圖」係示出在「第2圖」中部份被放大之波形。 參考「第2圖」，第一切換單元SW1回應從定時控制器所提 供之PWM s周光號而控制LED陣列10之電流。在此情況下， PWM調光訊號係為以固定間隔重複一低狀態和一高狀態之一 PWM訊號。在PWM調光訊號之一高週期中，隨著第一切換單元 SW1被打開’用於LD3陣列1〇之驅動電流被產生。在pWM調 光訊號之一低週期中，隨著第一切換單元SW1被關閉，用於LED 陣列10之驅動電流不被產生》 依照此’既然在PW]V[調光訊號之低週期中，在Led陣列1〇 上沒有負載，以及由於延遲效應，驅動電壓Vle(j則在電壓產生單 元40之一輸出終端上升。如果驅動電壓^以因此上升，反饋電 壓FB也上升，引起差動放大器2〇轉發具有低電勢之放大訊號。 因此，如果差動放大器20在PWM調光訊號之低週期，輸出 具有低電勢之放大訊號，穩定器60之第二電容C2被放電。 既然當放大單元50放大並輸出在反饋訊號和參考訊號之差值 時在PWM調光訊號之低週期中被放電之第二電容〇被充電，， 在此時間點PWM調光訊號從低狀態上升至高狀態之，隨著第二 電容C2被充電之時間’延遲係發生^因此，從差動放大器2〇所 12 201250351 輸出之訊號係與延遲晚一樣多時間而被提供至比較器3〇。 比較器30比較從放大單元50所輸出之放大訊號與參考訊號 (三角波形訊號’ Ramp)以產生具有占空比之一切換訊號，並輸 出此切換訊號至電壓產生器40之第一切換裝置T1。• The -W number switches between the amplification unit and the stabilizer. Further, a backlight unit includes: an LED array having a plurality of LEDs; - a voltage generating unit 70 gamma gamma generating a driving voltage to shunt - a switching signal to drive the LEDs, and an amplifying unit 'for feeding back the driving voltage and Amplifying the feedback driving voltage to output an amplified signal; a stabilizer for stabilizing the amplified signal; and a comparator for comparing the amplified signal with a reference waveform to apply the switching signal to the voltage generating unit; a first switching unit And is used for responding to one of the PWM dimming signals from a certain time controller to switch the current of one of the LED arrays; and a second switching unit for responding to the PWM dimming signal to switch between the amplifying unit and the stabilizer. The first switching unit, the second switching unit, and the third switching unit are turned on in one of the high periods of the PWM dimming signal, and are turned off in one of the low periods of the PWM dimming signal. The reference waveform has a triangular waveform. A method for driving a backlight unit, the method comprising: generating a driving voltage in response to a switching signal to drive an LED array; distributing and feeding back a driving voltage, and amplifying the feedback driving voltage to generate an amplification signal; and stabilizing the amplification signal; Responding to a PWM dimming signal, controlling a current of the LED array; comparing the amplified signal with a reference waveform to generate a switching signal; and responding to the PWM dimming signal switching switching signal 0. Further, a method for driving a backlight unit, the method comprising Responding to a switching signal to generate a driving voltage to drive an LED array; distributing and feeding back the driving voltage, and amplifying the feedback driving voltage to generate an amplification signal; stabilizing the amplification signal; responding to a PWM dimming signal, controlling one of the LED array currents Comparing the amplified signal 201250351 ” 'Coss to generate 鸠峨; and shouting PWM dimming signal to switch the amplified signal to unstablely amplify the signal. It is to be understood that the above summary of the present invention and the following detailed description are examples. And the transfer of the 'depending on the provision of the power of the sentence [Embodiment] Reference will now be made in detail to the particular embodiments of the invention, which are set forth in detail, The embodiment of the backlight unit of the present invention and the method for driving the backlight unit will be described in detail with reference to the accompanying drawings. During this period, the backlight unit according to the present invention has an LED applied thereto as a guide for guiding Light-to-liquid crystal panel-light source. In the backlight unit, although it has a direct-type and a-edge type depending on the position of the light source, the present invention is not limited thereto. FIG. 1 is a view according to the present invention. A circuit diagram of a backlight unit of one embodiment. Referring to "FIG. 1", the backlight unit includes: a plurality of LEDs arranged in a plurality of channels, each of which has a plurality of LEDs; and in response to a switching signal, is used to drive a plurality of LEDs to generate a driving voltage. a voltage generating unit 40 for vied; for distributing the driving voltage Vled, generating a feedback voltage FB, differentially amplifying the feedback voltage FB to generate an amplification unit 5 of the amplification signal; for stabilizing the output from the amplification unit 50 The one of the amplified signals is a stabilizer 60; for comparing the amplified signal outputted from the amplifying unit 50 with a reference signal (a triangular waveform signal) to pass through the 201250351 voltage conversion generating unit 4G - the first-switching farm control - a current-comparator 30 of the led array; a PWM dimming signal outputted in response to a slave controller (not shown) for switching one of the currents of the LED array 1 第一 first switching unit SWi; and a response The side dimming signal outputted from the timing (four) is used to switch the switching unit ϋ2 from the output ϋ 30 output to the second unit sw2. Although not shown in the figure, the sense-current-detection resistor can be included between the first switching device T1 and the ground_. The LED array 1A includes a plurality of channels ch each having at least two LEDs connected in series. Although the "!!" illustrates a channel, the number of channels ch contained in the Lm) array is not limited. The led is configured to emit a white light to the liquid crystal panel. However, depending on the situation, the LEDs can be configured to emit any of red (R), green (G), and blue (B) light. The voltage generating unit 40 includes an inductor L, a first switching device, a diode D, and a first capacitor (the voltage generating unit 4 〇 passes through the inductor L, the diode D, and the first capacitor ( The resonance of the 产生 generates a DC current (in other words). In other words, the first switching device T1 is switched in response to the duty ratio of the switching signal from the output of the comparator 30 to switch an input voltage Vin to have one. A constant level DC drive voltage vied, and a switched drive power supply vied to the LED array 10. During this time, the diode D prevents the current supplied to the LED array from flowing in the reverse direction, and the first capacitor C1 stabilizes the driving voltage. The amplifying unit 50 distributes the driving voltage vied in accordance with a resistance ratio of one of the first resistor R1 and the second resistor R2 to generate a feedback voltage FB. In this case, the feedback voltage FB is supplied to the differential amplifier 20. The differential amplifier 2 〇 amplifies a difference between the feedback voltage FB and the reference voltage vref of 201250351, and outputs the amplified difference. To do this, the differential amplifier 2 〇 has one of the received feedback voltages FB An input terminal, and a non-inverting input terminal for receiving one of the reference voltages Vref. In other words, assuming that the difference between the feedback voltage FB and the reference voltage Vref becomes higher, the amplifying circuit 5 outputs a signal having a high potential Assuming that the difference becomes lower, the output has a signal having a low potential. The stabilizer 60 includes a second capacitor C2, a third capacitor C3, and a third resistor illusion. The comparator 30 compares the differential amplifier 20 The output differential signal and a reference waveform Ramp are used to generate a switching signal. To do this, the comparator 3A has an inverting input terminal for receiving the reference waveform Ramp, and for receiving from the differential amplifier 20 One of the output differential signals is a non-inverting input terminal. Although the reference waveform Ramp has a three-teaching waveform in the embodiment, it is not limited thereto. During this period, the switching signal output from the comparator 30 is A PWM signal of a predetermined duty ratio. In detail, the switching signal changes as the comparison operation of the comparator 3 is as follows. In other words, if the amplified signal is output from the differential amplifier 20 There is a higher potential than the amplified signal of the reference waveform Ramp, and the comparator 3 outputs a switching signal having a high level. If the amplified signal output from the differential amplifier 20 has a lower potential than the amplified signal of the reference waveform Ramp, comparison is made. The switch 3 outputs a switching signal having a low level. Here, if the amplified signal output from the differential amplifier 20 has a longer potential than the amplified signal output from the reference waveform Ramp, the switching signal is switched. The duty ratio is increased. However, if the amplified signal output from the differential amplifier 2 has a lower potential than the amplified signal output from the reference waveform Ramp, the duty ratio of the switching signal becomes small. 201250351 ~ ^ . Therefore, the voltage generating unit 4〇 maintains the driving voltage Vied constant by using switching signals having different duty ratios*. As described earlier, the amplifying unit 5 〇 uses the feedback voltage FB to maintain the driving voltage Vied constant. Assuming that the backlight unit of "Fig. 1" does not include the second switching unit SW2, the following drawbacks may occur. That is, one of the PWM dimming signals provided from the timing controller repeats a low state and a high state at regular intervals. During one of the high periods of the PWM dimming signal, the first switching unit SW1 is turned on to generate a driving current for the LED array 1 . During one of the low periods of the PWM dimming signal, the first switching unit SW1 is turned off without generating a driving current for the LED array 10. According to this, since the LED array 1〇 has a load in the low period of the PWM dimming signal, and the delay effect mentioned later, the driving voltage Vied rises at one of the output terminals of the voltage generating unit 40. If the drive voltage 乂丨 rises accordingly, the feedback voltage FB also rises, causing the differential amplifier 2 〇 to forward a signal having a low potential. Therefore, if the differential amplifier 20 outputs a low-potential amplification signal during the low period of the PWM dimming signal, the second capacitor C2 of the stabilizer 60 is discharged. During this period, the delay occurs as the second capacitor C2 is charged, because the amplification unit 50 amplifies and outputs the difference between the feedback signal and the reference signal as described above, in the PWM dimming signal. The second capacitor C2 that is discharged during the low cycle is charged, and at this point in time, the PWM dimming signal rises from a low state to a high state. Therefore, the signal output from the differential amplifier 20 is supplied to the comparator 30 by 11 201250351 as much as the delay later. The generation of the delay causes the ripple of the driving power source Vied. This will be described in detail. The "Fig. 2" shows a waveform for describing the delay occurring in an amplifying unit 50 and a comparator 3 when the backlight unit of the "ith drawing" does not include the second switching unit. "Fig. 3" shows a waveform that is partially enlarged in "Fig. 2". Referring to "Fig. 2", the first switching unit SW1 controls the current of the LED array 10 in response to the PWM s ambient light number supplied from the timing controller. In this case, the PWM dimming signal is a PWM signal that repeats a low state and a high state at regular intervals. In one of the high periods of the PWM dimming signal, as the first switching unit SW1 is turned on, the driving current for the LD3 array 1 is generated. In one of the low periods of the pWM dimming signal, as the first switching unit SW1 is turned off, the driving current for the LED array 10 is not generated. According to this, since in the low period of the PW]V [dimming signal, There is no load on the Led array 1 ,, and the driving voltage Vle (j rises at the output terminal of one of the voltage generating units 40 due to the delay effect. If the driving voltage ^ thus rises, the feedback voltage FB also rises, causing the differential amplifier 2 〇 Forwarding the amplified signal with a low potential. Therefore, if the differential amplifier 20 outputs a low-potential amplification signal during the low period of the PWM dimming signal, the second capacitor C2 of the stabilizer 60 is discharged. And outputting the second capacitor 放电 discharged during the low period of the PWM dimming signal when the difference between the feedback signal and the reference signal is charged, and the PWM dimming signal rises from the low state to the high state at this time point, When the second capacitor C2 is charged, the delay is generated. Therefore, the signal output from the differential amplifier 2201250351 is supplied to the comparator 3〇 as much as the delay. The comparator 30 compares the amplified signal and the reference signal (triangular waveform signal 'Ramp) output from the amplifying unit 50 to generate a switching signal having a duty ratio, and outputs the switching signal to the first switching device T1 of the voltage generator 40. .
如「第3圖」所示，由於延遲，當與PWM調光訊號相比較 時從比較器30所輸出之切換訊號被延遲一恒定時間。即，在pwM 調光訊號之上升沿切換訊號不被輸出，而在PWM調光訊號之下 降沿被輸出。 因此’既然切換虎不被輸出，儘管由於在[調光訊號 之上升沿中之PWM調光訊號’具有發生在LED陣列1〇上之一負 載，驅動電壓Vied立即下降。既然切換訊號被輸出，儘管由於在 PWM調光訊號之下降沿中之pwm調光訊號，不具有發生在led 陣列10上之一負載，驅動電壓Vied立即上升。 由於上述原因，在PWM調光訊號之上升沿中，驅動電壓观 暫時形成具有低電勢之波紋。驅動電壓Vied之波紋影響LED驅 動電流，導致亮度之一缺陷。 為了解決上述問題，「第1圖」之實施例建議提供連接至比較 器30之一輸出終端之第二切換單元，。第二切換單元漁係 配置以回應PWM調光訊號而被切換。 一種用於驅動在比較器30之輸出終端具有第二切換單一 SW2之「第i圖」之背光單元之實施例之方法，料下；J述。 「第4圖」係示出「第i圖」中之背光單元之驅動波形。 辦「第4圖」’依照本發明之「第1圖」之實施例之背光單 13 201250351 元在PWM調光訊5虎從一低狀態升至一高狀態之時間點以及在 PWM調光訊號從一低狀態升至一高狀態之時間點，阻止切換訊號 之轉發延遲，致使維持驅動電源Vied恒定，能夠維持LED驅動 電流穩定。 即’如參考「第2圖」和「第3圖」上文所提及，由於延遲， 當與PWM調光訊號相比較時，從比較器30所輸出之切換訊號被 延遲一恒定時間。換句話說，在PWM調光訊號之上升沿切換訊 號不被輸出，而在PWM調光訊號之下降沿被輸出。 但是’既然第二切換單元SW2透過PWM調光訊號被切換（關 閉），調光訊號不從比較器30被輸出至電壓產生器40之第一切換 裝置T1。因此，在PWM調光訊號之下降沿，在LED陣列1〇上 沒有負載之同時，驅動電壓Vied之上升透過延遲而被阻止。 因此，既然驅動電壓Vied在PWM調光訊號之低週期不在瞬 間上升，放大單元50之反饋電壓FB沒有上升，進而放大器2〇 持續輸出具有高電勢之一放大訊號。 因此，既然差動放大器20甚至在PWM調光訊號之一低週期 輸出具有高電勢之一放大訊號’穩定器60之電容器C2不被放電。 進一步，由於PWM調光訊號從一低狀態上升至一高狀態之時間 點’不需要充電穩定器60之第二電容C2。因此，從差動放大器 20輪出至比較器30之放大訊號之延遲不會出現。 如上文所提及，既然延遲不會出現，從比較器30所輸出之切 換訊號與PWM調光訊號同步。即，切換訊號在PWM調光訊號之 上升沿被輸出，而在PWM調光訊號之下降沿不被輸出。 201250351 *·* 、 因此，在PWM調光訊號之上升沿，驅動電壓Vied之一瞬間 降落可以被阻止，以及在PWM調光訊號之下降沿，驅動電壓 之瞬間上升可以被阻止。同樣，背光單元可以在PWM調光訊 號之上升沿阻止驅動電壓Vied之一波紋，能夠實現LED驅動電 流之穩定的維持。 以及’在「第1圖」中，甚至在第二切換單元SW2係位於放 大單元50和穩疋器6〇之間的情況下’切換訊號之延遲可以被可 靠地阻止。 這將詳細被描述如下。 第5圖」係為依照本發明之一另一實施例之一背光單元之 一電路圖。 除了位於放大單元50和穩定器6〇兩者之間之第二切換單元 SW2 ’「第5圖」之背光單元係類似於「第1圖」之背光單元。第 二切換單元SW2餘置㈣過PWM贼峨*被切換。 八有位於放大單元50和穩定器60兩者之間之第二切換單元 SW2之帛5圖」之背光單元之操作將被描述如下。 如多考第2圖」和「第3圖」所描述，既然在pwM調光 訊號之低週射，在LED _ 1G上沒有負載，則在電壓產生單 ㈣之輸出終端之驅動電壓vled上升，進而甚至儘管差動放大 器2〇輪出具有低電勢之一放大訊號，因為第二切換單元SW2在 PWM調光訊號之低週射被酬穩定㈣之第二電容C2浮動， 並不被放電。 而且賴不需要充電第二電容ο，儘管在調光訊號 15 201250351 從一低狀態升至一高狀態之時間點第二切換單元SW2被打開，從 差動放大器20被提供至比較器30之訊號之延遲不會出現。 因此，既然延遲不會出現，從比較器30所輸出之切換訊號與 PWM調光訊號同步。即’切換訊號在PWM調光訊號之上升沿被 輸出’而在PWM調光訊號之下降沿不被輸出。 在PWM調光訊號之上升沿之驅動電壓vled之一瞬間降落可 以被阻止，以及在PWM調光訊號之下降沿之驅動電壓¥1以之一 瞬間上升可以被阻止。同樣，背光單元可以在pwM調光訊號之 上升沿阻止驅動電壓Vied之一波紋，能夠實現LED驅動電流之 穩定維持。 以及在「第1圖」中，切換訊號之延遲在第三切換單元SW3 被進一步包含在放大單元5〇和穩定器6〇之間的情況下可以被可 罪地阻止。 這將詳細被描述如下。 第6圖」係為依照本發明之一又一實施例之一背光單元之 一電路圖。 w除了進一步位於玫大單元50和穩定器60兩者之間之第三切 換單TCSW3 ’「第6圖」之背光單元細似於「第丨圖」之背光單 疋第二切換早元SW3係配置以透過pwM調光訊號而被切換。 μ進—步具有第三切換單元SW3之「第6圖」之背光單元之掉 作包含「筮1园i r i 」°第5圖」中所示之背光單元之操作因此，「第 6 _㈣切織謝。 與「第1圖，「& 第5圖」之實施例比較，在「第6圖」之 201250351 貫施例中’在PWM調光訊號之上升沿之驅動電源Vled之一瞬間 降落可以纽阻止’以及在PWM調光喊之上升封鷄傾 Vied之上升可以更被阻止。同樣，背光單元可以在剛^ 調光訊號之上升沿阻止驅動電壓Vledi一波紋，能夠實現led 驅動電流之穩定的維持。 如已經被描述，本發明之背光單元及其驅動方法具有以下優 勢。 依照本發明之背光單元之實關，切換訊號之轉發延遲在調 光訊號從低狀紅升至高絲之時間點被阻止，致使維持驅動電 源Vied恒定，能夠維持L]ED驅動電流穩定。本領域之技術人員 應當意識到在不脫離本發明所附之申請專利範圍所揭示之本發明 之精神和範圍的情況下，所作之更動與潤飾，均屬本發明之專利 保護範圍之内。關於本發明所界定之保護範圍請參照所附之申請 專利範圍。 【圖式簡單說明】 第1圖係為依照本發明之一實施例之一背光單元之一電路 圖； 第2圖係示出假設第i圖之背光單元不包含一第二切換單元 之用於描述在一放大單元和一比較器之發生的延遲之波形； 第3圖係示出在第2圖中部份被放大之波形； 第4圖係示出第丨圖中之背光單元之驅動波形； 第5圖係為依照本發明之一另一實施例之一背光單元之一電 17 201250351 路圖； 第6圖係為依照本發明之一又一實施例之一背光單元之一電 路圖。 【主要元件符號說明】 10 LED陣列 20 差動放大器 30 比較器 40 電壓產生單元 50 放大單元 60 穩定器 C1 第一電容 C2 第二電容 C3 第三電容 ch 通道 D 二極體 FB 反饋電壓 GND 接地 L 感應器 LED 發光二極體 R1 第一電阻 R2 第二電阻 18 201250351 R3 第三電阻 Ramp 參考波形 SW1 第一切換單元 SW2 第二切換單元 SW2 第三切換單元 T1 第一切換裝置 Vin 輸入電壓 Vied 驅動電壓 Vref 參考電壓 19As shown in "Fig. 3", due to the delay, the switching signal output from the comparator 30 is delayed by a constant time when compared with the PWM dimming signal. That is, the switching signal is not output on the rising edge of the pwM dimming signal, but is output on the falling edge of the PWM dimming signal. Therefore, since the switching tiger is not output, although the PWM dimming signal in the rising edge of the dimming signal has a load occurring on the LED array 1, the driving voltage Vied immediately drops. Since the switching signal is output, although the pwm dimming signal in the falling edge of the PWM dimming signal does not have a load occurring on the led array 10, the driving voltage Vied rises immediately. For the above reasons, in the rising edge of the PWM dimming signal, the driving voltage is temporarily formed into a ripple having a low potential. The ripple of the drive voltage Vied affects the LED drive current, resulting in one of the defects in brightness. In order to solve the above problem, the embodiment of "Fig. 1" suggests providing a second switching unit connected to one of the output terminals of the comparator 30. The second switching unit is configured to switch in response to the PWM dimming signal. A method for driving an embodiment of a backlight unit having an "i-th diagram" for switching a single SW2 at an output terminal of the comparator 30, which is described below; "Fig. 4" shows the driving waveform of the backlight unit in "ith diagram". According to the embodiment of the "Fig. 1" of the present invention, the backlight unit 13 201250351 is in the PWM dimming signal 5 when the tiger rises from a low state to a high state and at the PWM dimming signal The time delay from the low state to the high state prevents the forwarding delay of the switching signal, so that the sustain driving power supply Vied is constant, and the LED driving current can be maintained stable. That is, as mentioned above with reference to "Fig. 2" and "Fig. 3", due to the delay, the switching signal output from the comparator 30 is delayed by a constant time when compared with the PWM dimming signal. In other words, the switching signal is not output on the rising edge of the PWM dimming signal, but is output on the falling edge of the PWM dimming signal. However, since the second switching unit SW2 is switched (turned off) by the PWM dimming signal, the dimming signal is not output from the comparator 30 to the first switching device T1 of the voltage generator 40. Therefore, at the falling edge of the PWM dimming signal, while the LED array 1 is not loaded, the rise of the driving voltage Vied is blocked by the delay. Therefore, since the driving voltage Vied does not rise instantaneously during the low period of the PWM dimming signal, the feedback voltage FB of the amplifying unit 50 does not rise, and the amplifier 2 持续 continuously outputs an amplification signal having a high potential. Therefore, since the differential amplifier 20 outputs a high-potential one of the PWM dimming signals with a high potential, the capacitor C2 of the stabilizer 60 is not discharged. Further, since the PWM dimming signal rises from a low state to a high state, the second capacitor C2 of the charging stabilizer 60 is not required. Therefore, the delay of the amplified signal from the differential amplifier 20 to the comparator 30 does not occur. As mentioned above, since the delay does not occur, the switching signal output from the comparator 30 is synchronized with the PWM dimming signal. That is, the switching signal is output on the rising edge of the PWM dimming signal and is not output on the falling edge of the PWM dimming signal. 201250351 *·* Therefore, on the rising edge of the PWM dimming signal, an instantaneous drop of the driving voltage Vied can be prevented, and at the falling edge of the PWM dimming signal, the instantaneous rise of the driving voltage can be prevented. Similarly, the backlight unit can block one of the driving voltages Vied on the rising edge of the PWM dimming signal, thereby achieving stable maintenance of the LED driving current. And in the "Fig. 1", even in the case where the second switching unit SW2 is located between the amplification unit 50 and the stabilizer 6A, the delay of the switching signal can be reliably prevented. This will be described in detail as follows. Figure 5 is a circuit diagram of a backlight unit in accordance with another embodiment of the present invention. The backlight unit of the second switching unit SW2' "Fig. 5" located between the amplifying unit 50 and the stabilizer 6 is similar to the backlight unit of "Fig. 1". The second switching unit SW2 is left (four) over PWM thief 峨 * is switched. The operation of the backlight unit having the second switching unit SW2 between the amplifying unit 50 and the stabilizer 60 will be described as follows. As described in Figure 2 and Figure 3 of the multi-test, since there is no load on the LED _ 1G in the low-cycle of the pwM dimming signal, the driving voltage vled at the output terminal of the voltage generating single (four) rises. Furthermore, even though the differential amplifier 2 rotates out of the amplification signal having a low potential, the second switching unit SW2 is not stabilized because the low capacitance of the PWM dimming signal is stabilized (four) and the second capacitor C2 floats. Moreover, it is not necessary to charge the second capacitor ο, although the second switching unit SW2 is turned on at the time point when the dimming signal 15 201250351 rises from a low state to a high state, the signal from the differential amplifier 20 is supplied to the comparator 30. The delay does not occur. Therefore, since the delay does not occur, the switching signal output from the comparator 30 is synchronized with the PWM dimming signal. That is, the 'switching signal is outputted on the rising edge of the PWM dimming signal' and is not output on the falling edge of the PWM dimming signal. An instantaneous drop in the driving voltage vled at the rising edge of the PWM dimming signal can be prevented, and the instantaneous rise in the driving voltage of ¥1 on the falling edge of the PWM dimming signal can be prevented. Similarly, the backlight unit can block one of the driving voltages Vied on the rising edge of the pwM dimming signal, and can stably maintain the LED driving current. And in "Fig. 1", the delay of the switching signal can be sinfully prevented in the case where the third switching unit SW3 is further included between the amplifying unit 5A and the stabilizer 6A. This will be described in detail as follows. Figure 6 is a circuit diagram of a backlight unit in accordance with still another embodiment of the present invention. The backlight unit of the third switching sheet TCSW3 '""Fig. 6", which is further located between the mega unit 50 and the stabilizer 60, is similar to the backlight unit of the "second diagram" and the second switching early element SW3 system. The configuration is switched by the pwM dimming signal. The operation of the backlight unit shown in the "figure 6" of the third switching unit SW3 includes the operation of the backlight unit shown in "Fig. 5". Therefore, "the sixth _ (four) is woven Thanks to the example of "Fig. 1, "& Figure 5", in the "2012 Figure 6", the example of the driving power supply Vled on the rising edge of the PWM dimming signal can be instantaneously dropped. New block' and the rise in PWM dimming can make the rise of Vied more blocked. Similarly, the backlight unit can prevent the driving voltage Vledi from ripple on the rising edge of the dimming signal, and can achieve stable maintenance of the LED driving current. As has been described, the backlight unit of the present invention and the driving method thereof have the following advantages. According to the backlight unit of the present invention, the switching delay of the switching signal is blocked at the time point when the dimming signal rises from the low state to the high wire, so that the sustain driving power source Vied is kept constant, and the L]ED driving current can be maintained stably. It will be appreciated by those skilled in the art that modifications and modifications may be made without departing from the spirit and scope of the invention as disclosed in the appended claims. Please refer to the attached patent application for the scope of protection defined by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a backlight unit according to an embodiment of the present invention; FIG. 2 is a diagram for explaining that the backlight unit of the second diagram does not include a second switching unit for description. a waveform of a delay occurring in an amplification unit and a comparator; a third diagram showing a waveform partially enlarged in FIG. 2; and a fourth diagram showing a driving waveform of the backlight unit in the second diagram; FIG. 5 is a circuit diagram of a backlight unit according to another embodiment of the present invention. FIG. 6 is a circuit diagram of a backlight unit according to still another embodiment of the present invention. [Main component symbol description] 10 LED array 20 Differential amplifier 30 Comparator 40 Voltage generating unit 50 Amplifying unit 60 Stabilizer C1 First capacitor C2 Second capacitor C3 Third capacitor ch Channel D Diode FB Feedback voltage GND Ground L Sensor LED Light-emitting diode R1 First resistor R2 Second resistor 18 201250351 R3 Third resistor Ramp Reference waveform SW1 First switching unit SW2 Second switching unit SW2 Third switching unit T1 First switching device Vin Input voltage Vied Driving voltage Vref reference voltage 19