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| 型号： | LM3445M/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 13/40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： | 是 |
| 拓扑： | PWM，降压（降压） |
| 输出数： | 1 |
| 内部驱动器： | 无 |
| 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 |
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SNVS570L – JANUARY 2009 – REVISED MAY 2013
VALLEY-FILL CIRCUIT
V BUCK supplies the power which drives the LED string. Diode D3 allows V BUCK to remain high while V+ cycles on
and off. V BUCK has a relatively small hold capacitor C10 which reduces the voltage ripple when the valley fill
capacitors are being charged. However, the network of diodes and capacitors shown between D3 and C10 make
up a "valley-fill" circuit. The valley-fill circuit can be configured with two or three stages. The most common
configuration is two stages. Figure 18 illustrates a two and three stage valley-fill circuit.
V+
D3
V BUCK
V + D3
V BUCK
C7
+
D9
R6
C7
+
D6
D9
R6
D8
R8
C10
D8
R8
C10
D4
+
C9
R7
D4
D5
C8
D7
C9
+
R7
Figure 18. Two and Three Stage Valley Fill Circuit
The valley-fill circuit allows the buck regulator to draw power throughout a larger portion of the AC line. This
allows the capacitance needed at V BUCK to be lower than if there were no valley-fill circuit, and adds passive
power factor correction (PFC) to the application. Besides better power factor correction, a valley-fill circuit allows
the buck converter to operate while separate circuitry translates the dimming information. This allows for dimming
that isn’t subject to 120Hz flicker that can be perceived by the human eye.
VALLEY-FILL OPERATION
When the “input line is high”, power is derived directly through D3. The term “input line is high” can be explained
as follows. The valley-fill circuit charges capacitors C7 and C9 in series (see Figure 19 ) when the input line is
high.
V BUCK
V+
D3
+
C7
+
V BUCK
2
-
D8
+
C10
D4
V BUCK
2
+
C9
-
Figure 19. Two Stage Valley-Fill Circuit When AC Line is High
Copyright ? 2009–2013, Texas Instruments Incorporated
Product Folder Links: LM3445
13
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3445MX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Triac Dimmable Offline LED Driver |
| LM3445MX/NOPB | 功能描述:板上安装温度传感器 RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
| LM3445TRIACEVAL | 功能描述:BOARD EVAL LM3445MM RoHS:否 类别:编程器，开发系统 >> 过时/停产零件编号 系列:PowerWise® 标准包装:1 系列:- 传感器类型:CMOS 成像，彩色（RGB） 传感范围:WVGA 接口:I²C 灵敏度:60 fps 电源电压:5.7 V ~ 6.3 V 嵌入式:否 已供物品:成像器板 已用 IC / 零件:KAC-00401 相关产品:4H2099-ND - SENSOR IMAGE WVGA COLOR 48-PQFP4H2094-ND - SENSOR IMAGE WVGA MONO 48-PQFP |
| LM3445TRIACEVAL/NOPB | 制造商:Texas Instruments 功能描述:TRIAC Dimmable Offline LED Driver Evaluation Board |
| LM3447 | 制造商:TI 制造商全称:Texas Instruments 功能描述:Phase Dimmable, Primary Side Power Regulated PFC Flyback Controller for LED Lighting |
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