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| 主题：LED的相關應用及驅動技術 | ||
| 在线问答： | ||
| [问：chentianyu321] | 採用PWM來調光,如何降低LED的低頻閃爍? | |
| [答：Tony] | For the PWM dimming control, the dimming frequency should be at least 100Hz or above. Otherwise, eyes may observed the flashing of the LEDs. The National LM3402/LM3404 buck LED regulator can be operated PWM dimming frequency from 100Hz to 20KHz, and provide the very fast rise & fall time of LED current during PWM dimming because of COT control architecture. | [2007-8-23 10:33:36] |
| [问：brbl] | LCD TV中的背光照明驅動,對色彩和對此度要求都很高,請問NS有什麽好的解決方案? | |
| [答：Sam] | LM3430+LM3432 is a good solution for LED backlight application. http://www.national.com/pf/LM/LM3430.html http://www.national.com/pf/LM/LM3432.html | [2007-8-23 10:36:01] |
| [主持人：ChinaECNet] | 各位聽眾（網友），上午好！歡迎參加中電網線上座談。今天，我們有幸邀請到美國國家半導體公司的專家就“LED的相關應用及驅動技術”舉行線上座談。在座談中，您可就您關心的問題與美國國家半導體公司的專家線上進行直接、即時的對話交流。中電網衷心希望通過大家的共同努力，不僅能夠增進各位聽眾（網友）對“LED的相關應用及驅動技術”的瞭解和掌握，而且能夠為大家事業的發展帶來裨益。 | [2007-8-23 10:36:12] |
| [问：brbl] | 驅動高亮度LED的輸出電容容量和驅動電流有什麽關係?容量根據什麽來確定? | |
| [答：Honsun] | 在用Buck Topology来做LED的驱动时例如LM3404,因为流过输出电感的电流等于输出的电流,另外LED是一个定电流的LOAD.所以在此电路下输出可不接輸出電容,这样同时对Dimming有好处. | [2007-8-23 10:36:24] |
| [主持人：ChinaECNet] | 我們已經進入問答階段如果聽眾想重溫演講或內容可以點擊下面“回顧演示”重看演講。 | [2007-8-23 10:36:36] |
| [问：fusijun] | 不同廠家的LED的參數不同,要達到相同的亮度和色彩,請問NS的驅動電路如何進行調整? | |
| [答：Alan] | LED brightness depends on current, so NS applies current source to fix LED current, all LEDs keeping same current, LED brightness will be uniform. If different LED supplier, Vf has different value, it"s necessary to have total system view. | [2007-8-23 10:36:45] |
| [问：sduboy] | 目前LED技術的發展的瓶頸主要是哪些方面？ | |
| [答：Hector] | Our understanding is that main issue now is how to get rid of the heat generated in the LED. | [2007-8-23 10:38:56] |
| [问：lengyuezhu] | 请问LM3489降压控制器目前市场价格定位在多少？ | |
| [答：Hector] | Thanks for your inquiry. You can check the #1K price from our web and contact our distributor for high volume pricing. | [2007-8-23 10:42:11] |
| [问：wyxcx] | LM3404 过流保护关断的时间是多少, PDF上好像找不到. | |
| [答：Tony] | The LM3404/LM3402 use the cycle by cycle current limit, not the hiccup / latch mode. As the peak current of LED hits the current limit threhold of 1.2A min, the LM3404 should stop the driving pulses. As the fault of overcurrent limit releases, the drving pulses resume. | [2007-8-23 10:42:43] |
| [问：liweijiang] | OLED的驅動和一般LED的驅動有何不同?NS有那些産品可以驅動OLED? | |
| [答：Ken] | Basically OLED need high voltage for biasing, normally an inductive boost regulator is used. National offer many inductive booster, LM3509 and LM3520 are inductive booster that dedicated for OLED. | [2007-8-23 10:42:56] |
| [问：eeprom] | LED目前是以定電流方式點亮，是否可以以Pulse方式來點亮呢? | |
| [答：Tony] | Yes, as discussed in this presentation, we can use the PWM dimming signal to control the brightness of LED. The advantage of using PWM dimming is the color-tune of LEDs current should be kept stable. | [2007-8-23 10:44:56] |
| [问：lengyuezhu] | LM3404驱动器输入电压在多大的范围内，都能保证输出稳定电流？ | |
| [答：Alan] | LM3404 can have uniform current from 6~42V input voltage. If you need higher Vin, LM3404HV has 75V rating. | [2007-8-23 10:46:11] |
| [问：xianjzhang] | LED均具有隨著工作時間的增加而亮度衰減的特性.請問,使用NS驅動電路對這方面有什麽樣的處理措施嗎?謝謝 | |
| [答：Honsun] | 这是因为白光LED是由蓝光的晶片加荧光粉而成,这个亮度衰減原理和现在的日光灯的亮度衰減原理一样.这一方面,LED厂家会给出方案. | [2007-8-23 10:49:14] |
| [问：zhenjin] | 我們知道不同公司的LED産品,其Vf電壓,亮度,色差都不同.在溫度變化的時候這些參數也有不同的變化.請問NS的專家,如何來處理這些問題以達到照明的穩定和一致性的?謝謝 | |
| [答：Tony] | yes, that"s why for driving LEDs , the constant current regulator should be used, in order to keep the LEDs current constant at different temp. | [2007-8-23 10:49:56] |
| [主持人：ChinaECNet] | 各位觀眾，現在用戶提問很踴躍，專家正在逐一回答。請耐心等待您問題的答案，同一問題請不要多次提交。 | [2007-8-23 10:52:30] |
| [问：dengwuquan_751] | 在LED限流保护方面如何做得才更好 | |
| [答：Honsun] | 例如使用LM3404来设计LED的驱动线路,就可很好的对LED定电流和限电流.这是因为LM3404检测LED的电流来控制LED的定电流! | [2007-8-23 10:52:36] |
| [问：liweijiang] | 請問專家,如何降低LED的低頻閃爍和電磁干擾的? | |
| [答：Tony] | For the LED PWM dimming control, the min. dimming frequency requires to set at least 100Hz or above, in order to reduce or eliminate effect of flashing of LEDs. If you use the switching current regulators to drive LEDs, the switching current loop should be minimized in the PCB layout, in order to reduce conducted & radiated EMI. | [2007-8-23 10:55:15] |
| [问：eeprom] | LED的反向耐壓一般是多少? 反向電壓操作在多少電壓內其壽命不會降低太多? | |
| [答：Sam] | In general, the reverse voltage is about ~5V. It should be no problem when operating within SOA. | [2007-8-23 10:55:24] |
| [问：eeprom] | LED是否可以用Sin Wave current驅動? Color-tune會如何呢? | |
| [答：Alan] | If your sine wave has negative current, LED is not able to turn on. If min. current is positive (>0), it"s possible. But LED brightness is not same at different time, for human eye"s it maybe fine. Color should be depended on which color LED, need check LED supplier. | [2007-8-23 10:57:27] |
| [问：fusijun] | LED的色溫和那些因素有關?如何控制? | |
| [答：Honsun] | LED在工作时只能将其中的一部分的电能转化成光能,还有一部分的电能转化成热能.这部分的热能很容易使LED的温度上升.从而影响LED的colour.所以加Heatsink来控制! | [2007-8-23 10:57:50] |
| [问：msncnnet] | 贵公司有生产85-265V交流输入电压的LED恒流驱动芯片吗？输出功率在3－5W的 | |
| [答：Tony] | I suggest to use LM5021, the PWM controller, to step down to 12V/24V first. And, then use LM3401 to drive the 3W-5W high brightness LEDs. | [2007-8-23 10:58:14] |
| [问：eeprom] | LED是否與一般二極體一樣有反向恢復電流損耗的問題? | |
| [答：Sam] | No, LED is used to operate at forward bias. | [2007-8-23 10:58:51] |
| [问：dengwuquan_751] | 在实际使用中，发现白光LED长时间连续使用1W的电力情况下,会造成连续使用后半段时间的亮度逐渐降低的现象,此种情况采用何种手段才能有所改善？ | |
| [答：Alan] | It"s difficult to solve by LED driver, since it"s LED issue. If more current goes through LED to keep same brightness, more heat is generated. LED life decreases quickly. It"s not recommended to use. | [2007-8-23 11:00:42] |
| [问：SINNY] | 請問LM3489降壓控制器目前市場價格定位在多少？ | |
| [答：Hector] | Thanks for your inquiry. You can check the #1K price from our web and contact our distributor for high volume pricing. | [2007-8-23 11:01:15] |
| [问：sduboy] | 發光二極體中散熱片主要是用什麼材料製成的? | |
| [答：Sam] | Copper or Aluminum polymer. | [2007-8-23 11:01:42] |
| [问：liliyan] | 高壓驅動電路用哪種IC比較適合用在E27燈頭里 | |
| [答：Honsun] | 你可用LM5021+LM3404! | [2007-8-23 11:03:52] |
| [问：Allen Zhang] | 如何应对多颗串并联设计中单个LED提前损坏? | |
| [答：Tony] | The LM3430 + LM3432 solution, which is the LED driving can support 6 channels of LED string. Each string can operates up to 40mA. And LM3430+LM3432 can detect the single fault of LEDs (open/ short LED), while other string of LEDs can still operates normally. | [2007-8-23 11:04:42] |
| [问：SINNY] | LM3404具有幾個獨立的PWM？功率能到多少？ | |
| [答：Ken] | LM3404 is an inductive buck LED driver driving a series string of LED, only one PWM pin available. The maximum output current is 1A. | [2007-8-23 11:05:04] |
| [问：zhengyingjun] | LM3489 芯片可以用于计算机供电电源吗？ | |
| [答：Hector] | Yes. LM3489 is a general purpose buck controller. | [2007-8-23 11:06:07] |
| [问：ghayx] | LM3404与其他同类产品相比优势在哪里？ | |
| [答：Honsun] | LM3404是COT方式的控制器,用户不需要做Loop Compensation,使用方偏简单,效率高,Reliability 高. | [2007-8-23 11:07:02] |
| [问：hnxxzkx] | 輸出電流可以调节吗，还是必须用典型的1.2A? | |
| [答：Hector] | I suppose you are referring to LM3404. Yes, the output current is adjusting by fine tuning the sensing resistor. For details, please refer to LM3404 datasheet. | [2007-8-23 11:08:02] |
| [问：jewmerchant] | PWM控制的優點是什麽？ | |
| [答：Tony] | The major advantage of using PWM brightness control is to keep the colour tune of LEDs stable, as using the duty cycle of PWM signal to alter the brightness of LEDs. | [2007-8-23 11:08:53] |
| [问：brbl] | 驅動高亮度LED的亮度隨溫度而變化,請問NS專家,如何採用溫度感測器來控制?還有其他的辦法嗎? | |
| [答：Sam] | The brightness control could be easy to achieve by adjusting the duty cycle of dimming pin. | [2007-8-23 11:09:53] |
| [问：peng-kai@163.com] | 请问:国半的LED驱动芯片是否可以应用在LED的大功率驱动中,是否有很好的解决方案;以及在应用中,散热的处理,以及在同时驱动几组LED时,更好的保证亮度均匀的处理! | |
| [答：Alan] | For multiple LED, NSC has LM3430+LM3432, LM50xx famile to support LEDs numbers up to 120(6 series, 20 parallel or more). If you need more power, check with our local FAE or distributor. LM3432 builts in current source and matching function to maintain current on each channel, 2% accuracy between min. and max. You can get good brighntess uniform. | [2007-8-23 11:09:59] |
| [问：SINNY] | LM3404驅動器輸入電壓在多大的範圍內，都能保證輸出穩定電流？ | |
| [答：Alan] | LM3404 is able to keep same current at 42V input. | [2007-8-23 11:10:54] |
| [主持人：ChinaECNet] | 各位觀眾，現在用戶提問很踴躍，專家正在逐一回答。請耐心等待您問題的答案，同一問題請不要多次提交。 | [2007-8-23 11:12:31] |
| [问：xxtaotao] | 这款产品電源轉換效率比同类产品高吗？ | |
| [答：Hector] | Sorry, I don"t know which part number are you referring to. In general, National offers many differnt types of high efficiency power products. | [2007-8-23 11:13:11] |
| [问：njtornado] | 請問：TFT-LCD Monitor或TV中的背光模組若使用RGB LED背光源，並使用色序法(Sequential Color)或無彩色濾光片(Color Filter-Less)的顯示技術，如何達到同步控制呢? | |
| [答：Alan] | You need check with main chipset and LED vender. NSC porvides LED driver to maintain LED brightness, but we cannot do synchronous by ourself. We need external control signal to ask synchronous. | [2007-8-23 11:13:15] |
| [问：ghayx] | ESD保护使用的那种模式？能达到多少？ | |
| [答：Honsun] | LED的驱动IC在IC design时已将ESD的保护已考虑了!在具体的应用中,依使用的环境再考虑ESD的设计! | [2007-8-23 11:13:52] |
| [问：zhurocky] | 1.如果led中短路，怎么处理。 | |
| [答：Honsun] | 如果LED短路,LED的驱动线路会保护整个系统! | [2007-8-23 11:16:25] |
| [问：dengwuquan_751] | 有关LED温升问题想问下你们是如何降低的，;要维持LED的使用寿命如何处理更好 | |
| [答：Sam] | Take care the heat dissipation of LED, such as add heatsink or airflow. Using the proper driver (high efficiency) is important, too. | [2007-8-23 11:16:26] |
| [问：hnzhengshasha] | 过热停机是靠什么实现的？ | |
| [答：Tony] | Our National LED drivers have internal over-temp protection. As the junction temperature is higher than pre-defined threhold, the LED driver shutdown. To protect LEDs exceed its max. allowable, u can attach PTC (temperature dependent resistor)to the baseplate / heatsink of LEDs, and comparator can be added in the protection circuit. As the temperature rises to certain level, the comparator trips low, and this signal uses to pull the DIM/enable pin to low, in order to shutdown the operation of LED driver | [2007-8-23 11:18:55] |
| [问：Lee001234] | 如何把網絡設計工具的設計成果轉化成真實成果? | |
| [答：Hector] | Our webench provides a highly reliable simulation environment. After the simulation, a BOM list will be generated. One can construct the ciruit for actual testing afterwards. | [2007-8-23 11:19:57] |
| [问：cyberxx] | LM3404 1.0A LED驅動器对温度要求怎样？ | |
| [答：Sam] | The junction temperature range of LM3404 is -40C~+125C. | [2007-8-23 11:20:06] |
| [问：liguang169] | 贵公司提供的LED驱动芯片是否需要外置的传感器提供闭环的温度控制？ | |
| [答：Alan] | Yes, so far, there is no tempperature compensation inside IC. IF you need very tight accuracy on different temp., NSC provides many temp. sensor products also. | [2007-8-23 11:20:53] |
| [问：sduboy] | LED共有哪幾種驅動方法？各自的特點是什麼？ | |
| [答：Honsun] | LED有电阻限流法,线性和开关电源驱动.电阻限流法简单但不能保证LED定电流!线性驱动功耗大.开关电源驱动效率高能保证LED定电流! | [2007-8-23 11:23:18] |
| [问：ghayx] | 在实际应用中，LM3404的效率可达到多少？ | |
| [答：Honsun] | 在实际应用中，LM3404的效率可达到85% | [2007-8-23 11:23:38] |
| [问：yws1234252] | LED共有哪几种驱动方法？ | |
| [答：Hector] | Please refer back to our presentation, thanks. | [2007-8-23 11:23:54] |
| [问：zhanggeni] | lm3404的輸入電壓可以在24v嗎?? | |
| [答：Ken] | Can, LM3404 can support 6~42V input. If higher input voltage needed, LM3404HV can support 6~75V input. http://www.national.com/pf/LM/LM3404.html | [2007-8-23 11:24:13] |
| [问：shian0551] | 現在LED還沒有完全替代的真正原因或者瓶頸在哪里？ | |
| [答：Tony] | Two main reasons: 1) the price of high brightness LED is still higher than other lighting solutions 2) need to tackle the thermal issue of high brightness LEDs As technologies of HB LEDs grow rapidly and become more mature in future, the application of HB brightness in general lighting will become much popular. | [2007-8-23 11:24:39] |
| [问：msncnnet] | LED在寿命期间，灯泡老化后的工作电流和管压降是否会有变化，驱动芯片如何去和进行控制和适应这种变化， | |
| [答：Honsun] | LED在寿命期间，灯泡老化后的工作电流和管压降一般不会有变化，因为LED有高可靠性和长寿命! | [2007-8-23 11:25:33] |
| [问：liguang169] | LED在设计时电流设定点一般如何设定？是否可以提供编程设定？ | |
| [答：Sam] | In general, current sensing resistor is easy to implement for constant current contorl. Please find the detail (calculation formula) in LM3402/LM3404/LM3405 datasheet. | [2007-8-23 11:27:44] |
| [问：renyuling] | 关于变色发光驱动电路,国半有没有相应的驱动芯片? | |
| [答：Alan] | LMU (Lighting Management Unit)is one of products in NSC to give you the brightness of RGB three different LEDs depending on audio, or signal. You can refer to LP3943/44, LP5527. | [2007-8-23 11:28:44] |
| [问：ghayx] | LM3404的封装类型是什么样的？有没有同类产品可以与之PIN TO PIN？ | |
| [答：Ken] | LM3404 offer in SOIC narrow 8pins package and PSOP 8pins package. LM3402 offer pin-to-pin to LM3404 on PSOP package. | [2007-8-23 11:30:02] |
| [问：dengwuquan_751] | 高亮度LED在使用上还存在一个问题是ESD(静电)的影响,国半在这方面是如何处理的？ | |
| [答：Honsun] | 国半使用的是100V的ABCD的工艺在设计和生产LED驱动!IC设计工程师已考虑ESD并在IC设计时已放了ESD的对策! | [2007-8-23 11:30:55] |
| [问：msncnnet] | LED操作在PWM调光，工作电流的是否会有较大的变化，会影响LED的寿命吗？ | |
| [答：Alan] | PWM method can offer wide brightness range, and no influence on LED life. It"s popular on LED driver market. PWM is an average way to average current and duty cycle. Since it works on max. current at each cycle, then average duty. You will have 10~100% to adjust brightness. | [2007-8-23 11:33:06] |
| [问：yws1234252] | 对于LED的驱动,恒流与恒压方式分别适合哪些应用场合? | |
| [答：Sam] | For LED application, constant current is the better method. The light output and color will vary by constant voltage control. | [2007-8-23 11:33:22] |
| [问：yws1234252] | LED用恒流驱动是否最佳?是否一定要用驱动模块? | |
| [答：Tony] | yes, the constant current is best control scheme as it keeps the brightness of LED stable & constant over temperature. And, National Semiconductor offers various LED current regulators as the simple & easy to use solution (such as LM3401,LM3402, LM3404, LM3405, LM3432+LM3430) to drive different types of LEDs. | [2007-8-23 11:33:49] |
| [问：Lee001234] | 我們一直使用lumiled產品, 應如何與national的一同使用? | |
| [答：Hector] | One easy way is to use our LED webench. A lot of Lumileds LEDs part can be selected in our webench simulation environment. With the configuraion information entered, the tool will select the most suitable driver for you. In addition, a lot of reference design and LED related technical document can be downloaded from LED.national.com/CHT | [2007-8-23 11:33:54] |
| [问：Lee001234] | 我現在是使用osram的產品,可以如何跟您們的產品配合. | |
| [答：Hector] | One easy way is to use our LED webench. A lot of Osram LEDs part can be selected in our webench simulation environment. With the configuraion information entered, the tool will select the most suitable driver for you. In addition, a lot of reference design and LED related technical document can be downloaded from LED.national.com/CHT | [2007-8-23 11:35:39] |
| [问：liguang169] | 应用于室内环境时，LED驱动芯片在AC/DC和DC/DC转换器下需要考虑哪些方面？及如何应用？ | |
| [答：Honsun] | 应用于室内环境时,依Input Voltage, 串并LED的方式,LED的数量,LED的瓦数,调光的要求来选用LED驱动芯片.例如输入电压高于LED的电压,用LM3404 Buck线路,如果输入电压底于LED的电压,用L嘸430 Boost线路. | [2007-8-23 11:36:29] |
| [问：yyyhqing] | 液晶屏的燈管是不是已經開始被LED所替代？前景如何？ | |
| [答：Alan] | For high end market, CCFL is replaced by LED. It"s very good future for LED, but price is still higher than CCFL. LED backlight has good sharp image, longer life, no mercury, and lower power advantages. | [2007-8-23 11:37:37] |
| [问：zhengfei] | 贵公司提供何种设计工具？ | |
| [答：Ken] | National have online webench to help our customer on analog design, including power, amplifier, data conversion, audio, wireless and interface. LED webench is include in power webench, and can access using below link. http://www.national.com/appinfo/power/led.html | [2007-8-23 11:39:42] |
| [问：zhanggeni] | 如何搭建電路以確定發光二極體的穩定工作電流？ | |
| [答：Honsun] | 使用LM3404检测LED的电流并控制LED定电流工作! | [2007-8-23 11:39:48] |
| [问：jiunnlin] | 溫度對LED的性能有一定的影響，NS如何解決這個問題？ | |
| [答：Sam] | Most of NS HB LED drivers are high efficiency switching regulators. Its thermal performance is better than linear regulator. | [2007-8-23 11:40:13] |
| [问：zhengfei] | 高亮度LED正向電流高，功耗也高很多是吗？ | |
| [答：Alan] | For higher brightness LED, it needs more power to drive. I think efficiency is close between high and low power LED. The advantage is samll space. | [2007-8-23 11:40:53] |
| [问：cyberxx] | 贵公司的高亮度LED驅動器相比同类产品价格有优势吗？ | |
| [答：Hector] | We offer high performance LED drivers at a reasonable price. Please contact our distributors for quote, thanks. | [2007-8-23 11:41:33] |
| [问：xxtaotao] | LM3489 芯片功耗有多少？ | |
| [答：Honsun] | LM3489只是一个控制器,他需外加P-MOSFET.这样在驱动10-20瓦的LEDs,Efficiency 在88%左右! | [2007-8-23 11:42:10] |
| [问：jewmerchant] | LED驅動器的能耗一般會達到多少？ | |
| [答：Alan] | The efficiency on LED driver is around 75%~93% depending on LED configuration and input voltage. | [2007-8-23 11:42:40] |
| [问：dengwuquan_751] | 交通诱导信息LED显示屏必须要使用专门的LED驱动芯片来实现,恒流驱动芯片选择问题？？ | |
| [答：Sam] | LM5021+LM3432 may be a solution for your app. | [2007-8-23 11:42:52] |
| [问：peng-kai@163.com] | 请问:国半的LED驱动器中,采用定电流的方式那种,在LED正向电压差异所带来的相关问题,是怎样处理的? | |
| [答：Tony] | They are the constant current regulators. The constant current regulator keeps the brightness of LED constant and stable as the input voltages & temperature varies. And, the brightness of LEDs is depends on the its current. That"s why we use the constant regulator to drive the LEDs, rather than voltage regulator. | [2007-8-23 11:43:05] |
| [问：shian0551] | LM3489最適合用於什麽場合，請舉出具體例子，LM3404呢 | |
| [答：Honsun] | LM3489最適合用在降压,对调光要求不高价钱底的应用場合.LM3404最適合用在降压,对调光要求高高性能的应用場合 | [2007-8-23 11:45:43] |
| [问：Allen Zhang] | 在LCD TV中如何实现LED的电流平衡? | |
| [答：Alan] | LM3432 is a good part for LCD TV, since LM3432 has current source built-in, and offer 2% current matching on min. and max. current LED string. LM3432 provides 6-channels current matching, OTP, analog and diming control brightness. | [2007-8-23 11:46:23] |
| [问：jewmerchant] | 輸出電容怎麽選擇型號？ | |
| [答：Honsun] | 在LED的驱动中,常用的电容有Ceramic Capapacitor和电解Capacitor.依ouput的电压选电容的耐压.电容的容量依IC的Datasheet选! | [2007-8-23 11:46:51] |
| [问：yws1234252] | 如果仅限于单个LED的高亮度光源,用哪一种芯片比较合适？ | |
| [答：Sam] | LM3402, LM3404 or LM3405 are good for single HB LED lighting. LM3402: good for 1W LED LM3404: good for 3W LED LM3405: good for battery source | [2007-8-23 11:47:19] |
| [问：hnzhengshasha] | 外置電阻有特殊要求么？ | |
| [答：Honsun] | 此电阻是用来设定LED的工作电流的要求高精度,温度特性好! | [2007-8-23 11:48:47] |
| [问：ncueeleo] | LED 照明技術確實是未來照明方向，但是LED本身和驅動電路成本也是不可忽視的，請問LED照明技術成本問題有望在多長時間內能爲市場廣泛接受？ | |
| [答：Hector] | Price of LED is dropping at about 15% year on year (from $/Lumens perspective) and Lumens/W is also growing very fast. LED used in lighting has already started but only for special lighting purpose,eg. decorative lighting. We expect LED lighting will see considerable market share 5 to 10 years down the road. | [2007-8-23 11:49:55] |
| [问：niuniuniu2020] | 这两款芯片对环境要求高吗？ | |
| [答：Honsun] | 我想你是指LM3430+LM3432.他们能在工业级环境下应用! | [2007-8-23 11:50:07] |
| [问：wyxcx] | LM3404 的供货周期是多长 | |
| [答：Hector] | In general, our lead time is around 6 weeks. | [2007-8-23 11:50:29] |
| [问：niuniuniu2020] | 采用高亮度LED的照明系统是将来的大趋势吗？最终将代替传统的照明系统吗？ | |
| [答：Tony] | As price of HB LEDs become lower and its technologies become mature, I think the HB LEDs in general lighting application will be much popular. Because the HB LEDs lighting have many advantages over traditional lighting solution, such as longer life, no UV radiation, more easy to drive.. | [2007-8-23 11:50:37] |
| [主持人：ChinaECNet] | 由於時間關係，本次中電網“線上座談”馬上就要結束了。雖然各位聽眾（網友）已與美國國家半導體公司的專家討論了許多問題，但是還有許多提問沒有來得及進行交流。本次線上座談結束後，中電網將請美國國家半導體公司的專家繼續答復所有的來自各位聽眾（網友）的提問，然後整理上載到中電網網站上，以便大家查閱。 | [2007-8-23 11:50:56] |
| [问：zorro2774] | 你好 请问贵公司的技术对于LED的使用寿命方面有什么影响？ 谢谢 | |
| [答：Sam] | NS solutions have higher efficiency (switching regulator) and good thermal performance. | [2007-8-23 11:51:36] |
| [问：jobnj0bn] | Does NS offer a LED driver chip for AC 110~220V input? | |
| [答：Tony] | We can use LM5021/LM5022, the PWM controller to step down to 12V-36V output, and then use LM3402, LM3404 to drive the LEDs. | [2007-8-23 11:52:53] |
| [问：jiunnlin] | 高功率LED所能達到的最大功率是多少？主要應用？ | |
| [答：Hector] | Please refer to our presentation, thanks. | [2007-8-23 11:54:08] |
| [问：aeoncom] | 以燈具應用而言 串聯到多少數量比較經濟 | |
| [答：Honsun] | 依安全电压来考量可驱动线路的Efficiency来讲,串聯到10-12數量比較經濟. | [2007-8-23 11:54:32] |
| [问：sduboy] | LED的恒流驅動與恒壓驅動方式各自的應用場合分別是什麼? | |
| [答：Alan] | Most popular way in market is constant current driver, since LED brightness varys current. If we use constant voltage, it"s difficult to get same brightness on different supplier LED different Vf. | [2007-8-23 11:54:49] |
| [问：lengyuezhu] | 请简要讲述一下LED的应用和驱动 | |
| [答：Hector] | Please refer to our presentation, thanks. | [2007-8-23 11:56:02] |
| [问：zhurocky] | 如果有open怎么处理，电路有什么设计避开。 | |
| [答：Honsun] | 在LED OPen时,LED的驱动线路有过压保护! | [2007-8-23 11:56:08] |
| [问：cjltw] | 1.LED的驅動如何控制在最小電力需求下進行? 2.LED的背光如何降低耗電? | |
| [答：Alan] | It seems like PC power saving mode. You can use different brightness or performance to reduce power. Of course, efficiency improvement is always good on power saving. | [2007-8-23 11:57:08] |
| [问：Allen Zhang] | LED与CCFL相比的优缺点是什么? | |
| [答：Sam] | Advantages of LED- 1. high efficiency 2. small size 3. shock resistance 4. long life 5. environment free | [2007-8-23 11:57:12] |
| [问：wuzhiwen36] | 需要LM3430，LM3432，3404，3402, 3401技术资料样品如何联系wuzhiwen36@vip.sina.com | |
| [答：Ken] | Pls goto National web page, type in the part number and search, it will link you to each product page. Inside the product page, you can found datasheet and application note. http://www.national.com/ | [2007-8-23 11:57:20] |
| [问：cjltw] | LED的背光如何降低耗電? | |
| [答：Alan] | Normally, higher brightness has higher poower disspation. One is efficiency improvment. The other one is improvement on light filter and reflector. | [2007-8-23 11:59:42] |
| [问：liweijiang] | 驅動電路的EMI和那些因素有關?NS驅動電路的EMI能達到什麽樣的標準? | |
| [答：Honsun] | 驅動電路的EMI和Switching Frequency, Rise time, Fall time,layout and circuit design有关!在NS的Datasheet中都有对有关NS驅動電路EMI的问题加以的说明! | [2007-8-23 11:59:52] |
| [问：renyuling] | LED的发光颜色,是因供给电流而导致颜色不同,还是因为工艺上不同而不同的.. | |
| [答：Sam] | yes, the color will vary when supply current change. | [2007-8-23 12:00:09] |
| [问：zhenjin] | 採用恒流源與恒壓源給LED供電,有些什麽不同的效果? | |
| [答：Tony] | If we use constant voltage regulator to drive the LEDs, as the voltage across the LEDs change slightly, the LED current will be increases signifcantly because the LED V-I characteristic is very similar to conventional diode. While use constant current regulator, the LEDs current keep stable as the input voltages & temperature varies. That means the constant regulator provide much stable control in the brightness of LEDs, as the input voltage / temperature changes. | [2007-8-23 12:01:21] |
| [问：evanfang] | LED在汽車照明方向上的應用前景如何？在這方面有沒有和LED競爭的材料？ | |
| [答：Honsun] | LED在汽車照明方向上的應用前景最广阔.LED在这方面最有競爭性! | [2007-8-23 12:02:05] |
| [主持人：ChinaECNet] | 在此，中電網特別感謝給予本次中電網線上座談巨大支持的美國國家半導體公司，特別感謝專門線上回答各位聽眾（網友）提問的美國國家半導體公司的各位專家們，特別感謝各位聽眾（網友）積極熱情的參與。 | [2007-8-23 12:02:50] |
| [主持人：ChinaECNet] | 祝大家事業有成、生活愉快！歡迎多提寶貴意見，歡迎關注中電網，下次再見。 | [2007-8-23 12:03:03] |
| [问：liguang169] | 贵公司提供的LED驱动芯片是否支持简单的通信协议？ | |
| [答：Alan] | Yes, LM27964, Lp3936 have I2C interface to adjust LED brightness by I2C commend. I think they are very good to meet your requirements. | [2007-8-23 12:03:07] |
| [问：sduboy] | 請問國家半導體公司的LED驅動產品在無線通信產品中是否有解決方案？ | |
| [答：Hector] | Yes, we have a lot of LED drivers specially designed for wireless applications. Please visit LED.national.com/CHT | [2007-8-23 12:03:18] |
| [问：dengwuquan_751] | 如何解决提高大电流对LED管的冲击保护问题,以便提高使用寿命？ | |
| [答：Sam] | The cycle-by-cycle current limit of LM3402/4 provide the fast protection. | [2007-8-23 12:05:07] |
| [问：evanfang] | 如何提高LED的對比度,又不大量增加功耗? | |
| [答：Honsun] | 在Sam的Presentation中有祥细的说明LED的对比度与哪些因素有关!请Refer to the Presentation. | [2007-8-23 12:05:37] |
| [问：easontsai] | 目前LED Backlight 運用在TV上之solution何者為最佳 | |
| [答：Alan] | LM3430 + LM3432 is a very good solution set on LCD TV. Since LED on LCD TV has many configurations, LM3430 is a boost regulator to offer power for LED. And LM3432 offeres good cuurent matching on each LED string (2%), max. output voltage up to 80V. If you have many series LED number, LM3432 is easy to operate in parallel, just put it on your board. | [2007-8-23 12:06:29] |
| [问：gengwang1220] | 目前NS的驅動電路能達到的輸出電流和輸出電壓最高有多大?是那個産品型號? | |
| [答：Sam] | LM3402: 6V-42V/75V, 0.5A LM3404: 6V-42V/75V, 1.0A LM3405: 3V-15V, 1.0A | [2007-8-23 12:07:27] |
| [问：xianjzhang] | 高亮度LED照明有哪些優勢？目前主要是用在那些領域?市場前景如何？ | |
| [答：Tony] | The HB LEDs become more popular in automotive, decoration lighting. Now the indoor general lighting, like MR16, also popular to use 1W /3W HB LEDs. | [2007-8-23 12:08:17] |
| [问：yyyhqing] | 升壓LED用的輸出電容是越大越好嗎?謝謝 | |
| [答：Honsun] | 如果不考量LED的调光,升壓LED用的輸出電容是大一点好,这样LED的纹波电压小! | [2007-8-23 12:08:23] |
| [问：jobnj0bn] | Does NS LED driver chip have any advantage (eg. power consumption or others) to other company? | |
| [答：Alan] | NS LED driver always has mini package (SOT23, LLP-6) and very small total solution space. Besides, NSC has good accuracy (1.5%~2%, over tempetature)and high efficiency (90%). | [2007-8-23 12:09:20] |
| [问：evanfang] | LED驅動晶片的尺寸大概爲多大,適合嵌入式應用場合嗎,謝謝 | |
| [答：Tony] | The package of our LED is quite small. For example, the package of LM3402 is only MSOP8 or MSOP8. Pls refer the datasheet of LM3402/LM3404. | [2007-8-23 12:10:23] |
| 非在线问答： | ||
| [问：chentianyu321] | 請問專家,如何進行比較容易的實現準確的色彩調試？謝謝！ | |
| [答：NS专家] | NS HB LED Drivers (LM3402, LM3404, LM3405, LM3401…) have fast dimming pin to achieve higher contract ratio compared with conventional power converters. | |
| [问：sduboy] | 如何保證LED的使用壽命？ | |
| [答：NS专家] | Thermal performance is the major concern. Besides take care of the heat dissipation of LED, using the right LED drivers is important, too. NS HB LED solutions (LM3402, LM3404, LM3405, LM3401..) are switching regulators and optimized efficiency by low feedback voltage. | |
| [问：zhengyingjun] | LM3404 1.0A LED驅動器功耗有多少？ | |
| [答：NS专家] | Besides, the loss of integrated MOSFET, the power dissipation on current sensing resistor is only 0.2W (1A x 1A x 0.2 ohm). | |
| [问：zorro2774] | 你好 请问贵公司的技术对于LED的其他性能方面有什么影响？例如LED的反应时间 谢谢 | |
| [答：NS专家] | NS HB LED Drivers (LM3402, LM3404, LM3405, LM3401…) have fast dimming pin (short delay time) to achieve higher contract ratio. | |
| [问：zorro2774] | 你好 请问贵公司的技术对于LED在强磁场环境下的工作有什么特殊的对应设计？ 谢谢 | |
| [答：NS专家] | Suggest taking care on PCB layout and shielding, and avoiding interference from electromagnetic. | |
| [问：yangao] | 用于外部时，LED驱动电路如何进行抗干扰防护？谢谢！ | |
| [答：NS专家] | Suggest taking care on PCB layout and shielding, and avoiding interference from electromagnetic. | |
| [问：yangao] | 国半的HBLE适用于哪些场合？ | |
| [答：NS专家] | 国半的HBLED的驱动方案适用于汽车,LCD-Panel,普通照明等等! | |
| [问：Betty] | 国办的Webench提供的参考设计以及电子方针都具有很高的可靠性，您可以直接采购样片通过Webench给出的电路及物料清单进行设计。 | |
| [答：NS专家] | 是的! | |
| [问：Betty] | webench.national.com/CHT or LED.national.com/CHT | |
| [答：NS专家] | 是的! | |
| [问：hnxxzkx] | 这两款芯片设计时候都可以采用外部元件吗？ | |
| [答：NS专家] | 你是指LM3430+LM3432.还是指LM3402和LM3404.这些IC的外围元件的设计你可参考IC的Datasheet. | |
| [问：lengyuezhu] | 我用这个芯片做电源，将12～24V输入变成5V输出。在输出电流100mA的时候纹波能达到20mV，输出电流到 | |
| [答：NS专家] | LM3404是COT控制器来控制LED恒电流工作.这个电流指的是平均电流.如果你设计的电感值偏小,流过LED的Ripple Current大.这Ripple Current 跨过LED和检测电阻就会产生大的纹波电压. | |
| [问：lengyuezhu] | 请问LM3404LED驱动器目前市场价格定位在多少？ | |
| [答：NS专家] | 在National的Website上有给出1K的参考价钱是USD1.5,详情请与NS的深圳,上海,北京Office联系! | |
| [问：njtornado] | NSC的發光二極體和其他公司的類似産品相比,突出的優勢在什麽地方?價格方面如何? | |
| [答：NS专家] | NSC is not the provider of HB LED, while NSC offers a wide variety of HB LED Driving Solution. Pls visit our website: led.national.com for more information | |
| [问：ncueeleo] | 如何達到同步控制(相關細節)? | |
| [答：NS专家] | ||
| [问：SINNY] | NS的LED驅動産品價格有優勢嗎? | |
| [答：NS专家] | Thanks for your inquiry. You can check the #1K price from our web and contact our distributor for high volume pricing. | |
| [问：yyyhqing] | 請問LED的發光率跟什麽有關係？ | |
| [答：NS专家] | Luminous flux is often used as an objective measure of the useful power emitted by a light source. The luminous flux of LED is proportional to the average current flowing through LEDs | |
| [问：renyuling] | 现在的LED手电,白光的那种,高亮,应该是3V供电,可是目前有的产品,只用一节1.5V的电池供电就可以.我研究了一下,是通过二极管＋电容倍压电路把电压提升到3V以上.还有极少数是使用倍压芯片供电的.我想问一下老师,这两种做法是规范的接法么?有没有这方面的规范的解决方案?谢谢您. | |
| [答：NS专家] | Besides these two approaches, boost switching regulator can also be used to step up the output voltage from 1.5V input. LM2623/A is the boost switching regulator that can operated at the min voltage of 0.8V. | |
| [问：renyuling] | 国半有专门能控制色温的芯片么? | |
| [答：NS专家] | So far, NSC doesn't have this kind of IC chipset. NSC has many temperature sensor to do compensation caused by temp. | |
| [问：renyuling] | 高亮度的LED的光强,波长会随温度的升高而变化么?如果是的话,这方面的控制是如何做的? | |
| [答：NS专家] | Temperatur has influence on LED color and brightness. It needs color management to keep same performance. But LED driver cannot achieve the feature. | |
| [问：ncueeleo] | 如果採樣三色LED進行視頻顯示，採用何種控制方案較爲合適？ | |
| [答：NS专家] | LM3430 + LM3432 is a good solution set for LCD TV backlight. The solution has good current matching. And build a protection for 1 LED failure, so total system safety remain stable and good operation. | |
| [问：Allen Zhang] | 目前如何解决LED老化变色问题? | |
| [答：NS专家] | You need check with LED vender, since LED driver is used to drive LED then maintain current. It cannot solve this problem. | |
| [问：jiunnlin] | 您好，貴公司是否提供LED驅動晶片的相應設計軟體？ | |
| [答：NS专家] | NSC can offer some SW calculation for LED driver design. You can check with local NSC FAE or distributor for details. | |
| [问：wyxcx] | LM3404 有没有跟 R2109一样的低压保护功能 | |
| [答：NS专家] | Since LM3404 uses COT topology, a min. ON time of 300ns is required. So min. Vout = Vin * 300nS / Tsw. | |
美国国家半导体致力开发各种高能源效率的模拟及混合信号半导体产品。该公司的PowerWise®系列产品旨在降低系统功耗，延长电池寿命，以及减少散热需求。美国国家半导体总部位于美国加州圣塔克拉拉(Santa Clara)，截至2008年5月25日为止的2008年财政年度的营业额达18.9亿美元。欲查询美国国家半导体的公司资料及产品信息，欢迎浏览该公司的网页，网址：www.national.com。
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