• Q: 白光LED相較於傳統燈泡和HID燈泡是否照度較低?
• A: 現時已沒有大的分別,但是LED壽命比較HID長.

• Q: 一般来说，LED的热管理是当LED过热时，通过减少电流减低热量，但此时光通量也同时降低，这势必会影响灯照效果，不知贵司最佳方案是什么？
• A: 與其LED的壽命減短, 光度稍減應是比較可以被接受的.

• Q: 用LED照明，灯的寿命是多少？可以点多少小时？
• A: The life-time of LED much depends on its operating junction temp & its driving current. Some LED manufactures, such as LumiLEDs & Cree.., the datasheet of LEDs show the life time curve against junction temp & driving current. And, u can read these datasheets for more detail information.

• Q: 有无资料可说明可靠性方面的问题？
• A: All information regarding quality can be access at http://www.national.com/analog/quality Should you have any further enquiry, please contact our technical support.

• Q: LED 汽車照明， 對於環境的需求， 要注意的有那些， 電路方面能夠作到那方面的協助
• A: As presentation mentioned, load dump and cold crank are basical. For circuit, wide input voltage and more safety indicator are helpful.

• Q: 1. 會不會談到LEDfor 汽車頭燈？2. PowerWise drivers可不可以用到汽車頭燈？
• A: yes, as I know, now the wattage of low beam LED headlamp is in the range of 30W - 50W. And, we can use LM3421/3 to implement either floating buck-boost & boost topology for head-lamp application. Thanks!

• Q: 請問Diming 頻率為何需要到50kHz ？與對比度的關係？
• A: For human eyes, it's not necessary. But in automotive or some applications, higher Dim frequency will give you more selection to prevent EMI, auido problems. LM3431 has wide contrast ratio for automotive applications.

• Q: 請問現在汽車上用LED尾燈，brake light有沒有需要造到那麼光亮，對尾隨車輛造成危險
• A: Of course, safety is the best important thing. But LED brightness is able to control by requirement. Using HB LED by switching has high efficiency to save power.

• Q: 請問如何提高LED的性能？
• A: 1. 以色彩飽和度來說:以電流驅動:讓LED燈色溫~不要偏掉~ 2. Thermal來說:Feedback reference voltage 越低越好.可降低power loss. 3. 讓LED 工作在較低junction temperature 壽命較長. 4. LED driver topology 以Buck效率較高~一樣可以降低thermal impact. 5. layout 要有足夠銅箔~以及適當的placement~才可做到均溫散熱~最佳效果

• Q: LM3423晶片的峰值驅動電壓多少？
• A: LM3423 has 75V input voltage and drive output to 75V also.

• Q: 美國國家半導體會否推出更高性能的LED驅動產品？
• A: Yes, one of market focus in National Semiconductor is the driving solution for different application area. And, National have the devlopment road-map of LED drivers for different application, includinhg automotive. Thanks

• Q: 怎樣才可知道系統設計的準確度？
• A: LED driver 電流的準確度,請翻閱NS產品data sheet.

• Q: 请问LM3421可以实现光控功能？
• A: Yes, LM3421 provides fast PWM LED dimming up to 50KHz,thus enabling constant LED current for optimal color temperature. Please find the details in datasheet page 14.

• Q: 请问能否得到今天的演讲材料的DPF 文档资料？
• A: You can download the presentation from www.taiwanwebinar.com

• Q: 请问国半是否有单锂电池的LED升降压驱动解决方案？
• A: Yes, LM3410 is a 525kHz/1.6MHz, constant current boost solution. The input range is 2.7V to 5.5V. Please find more information from the link below, http://www.national.com/pf/LM/LM3410.html

• Q: 对于PWM调光系统来说，很多时候低调光占空比会使系统产生一些可闻噪音，这个国半是否有解决办法（我目前用的就是LM3402，低占空有音频噪声）？
• A: Audio noise 通常因陶瓷電容的壓電效應,或磁性元件的線圈震動所照成, 除了選用適當的元件外, 改變PWM dimming的切換頻率也可以改善.

• Q: 就目前PWM调光来说，LED是否会因为长期工作在脉冲电流下而缩短寿命？还有LED在自身允许的最大电流下往往 电-光 效率比较低，不及小电流时候的电-光 效率，国半公司是否有好的解决办法？比如更加先进的调光方式？
• A: 使用PWM dimming 是常用的調光方式之一, 應不至於縮短LED壽命 且有色溫不會跑掉的優點. NS solutions 通常均有支援PWM dimming, 也有部份支援 analog dimming.

• Q: 各种颜色的LED是否寿命相同，会不会出现寿命差异导致亮度和色差的问题
• A: Basically. different LED has different behavior, life and temp. characteristic. IF on RGB backlight, need temp. compensation to correct RGB. But if you use white LED, you will have familiar behavior

• Q: Use in can the LED system ，need pass what standard?
• A: Since different end customer of automotive has different requirments and criteria, it should be depend on standards from customer. In Taiwan,ISO7637 provides fundamental standard.

• Q: Is there LEDs failure detection mechanism?
• A: We got OVP, OCP, UVLO, OTP protections. Or shut down one series when one string over two LED damage. For example :LM3430 & LM3432