参数资料
型号: LM3445M/NOPB
厂商: National Semiconductor
文件页数: 26/40页
文件大小: 0K
描述: IC LED DRIVER TRIAC DIMM 14SOIC
特色产品: LM3445 TRIAC Dimmable LED Driver
标准包装: 55
系列: PowerWise®
恒定电流:
拓扑: PWM,降压(降压)
输出数: 1
内部驱动器:
类型 - 次要: 高亮度 LED(HBLED)
频率: 30kHz ~ 1MHz
电源电压: 8 V ~ 12 V
安装类型: 表面贴装
封装/外壳: 14-SOIC(0.154",3.90mm 宽)
供应商设备封装: 14-SOICN
包装: 管件
工作温度: -40°C ~ 125°C
产品目录页面: 1285 (CN2011-ZH PDF)
其它名称: LM3445M
SNVS570L – JANUARY 2009 – REVISED MAY 2013
V +
θ = 45°
V PEAK
t
V +
θ = 90°
V PEAK
t
V +
θ = 135°
V PEAK
t
Figure 31. AC Line with Various Firing Angles
V PEAK
V PEAK
V DC
V +
V DC
t
V +
V DC
t
Figure 32. V BUCK Waveforms with Various Firing Angles
To determine how many LEDs can be driven, take the minimum voltage the buck converter will see (42.5V) and
divide it by the worst case forward voltage drop of a single LED.
Example: 42.5V/3.7V = 11.5 LEDs (11 LEDs with margin)
OUTPUT CAPACITOR
A capacitor placed in parallel with the LED or array of LEDs can be used to reduce the LED current ripple while
keeping the same average current through both the inductor and the LED array. With a buck topology the output
inductance (L2) can now be lowered, making the magnetics smaller and less expensive. With a well designed
converter, you can assume that all of the ripple will be seen by the capacitor, and not the LEDs. One must
ensure that the capacitor you choose can handle the RMS current of the inductor. Refer to manufacture’s
datasheets to ensure compliance. Usually an X5R or X7R capacitor between 1 μF and 10 μF of the proper
voltage rating will be sufficient.
SWITCHING MOSFET
The main switching MOSFET should be chosen with efficiency and robustness in mind. The maximum voltage
across the switching MOSFET will equal:
V DS(MAX) = V AC-RMS(MAX) 2
The average current rating should be greater than:
I DS-MAX = I LED(-AVE) (D MAX )
(31)
(32)
26
Product Folder Links: LM3445
Copyright ? 2009–2013, Texas Instruments Incorporated
相关PDF资料
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NLC453232T-3R9K-PF INDUCTOR WW PWR 3.9UH 700MA 10%
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