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| 型号： | LM3445TRIACEVAL |
| 厂商： | National Semiconductor |
| 文件页数： | 8/40页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL LM3445MM |
| 标准包装： | 1 |
| 系列： | PowerWise® |
| 电流 - 输出 / 通道： | 770mA |
| 输出及类型： | 1，非隔离 |
| 特点： | 可调光 |
| 输入电压： | 8 ~ 12V |
| 已供物品： | 板 |
| 已用 IC / 零件： | LM3445MM |
| 相关产品： | LM3445MMX-ND - IC LED DRIVER TRIAC DIMM 10-MSOP LM3445MMDKR-ND - IC LED DRIVER TRIAC DIMM 10-MSOP LM3445MMCT-ND - IC LED DRIVER TRIAC DIMM 10-MSOP LM3445MMTR-ND - IC LED DRIVER TRIAC DIMM 10-MSOP |
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SNVS570L – JANUARY 2009 – REVISED MAY 2013
An RC network consisting of R1, R2, and C1 delay the turn on of the triac until the voltage on C1 reaches the
trigger voltage of the diac. Increasing the resistance of the potentiometer (wiper moving downward) increases the
turn-on delay which decreases the on-time or "conduction angle" of the triac ( θ ). This reduces the average power
delivered to the load. Voltage waveforms for a simple triac dimmer are shown in Figure 13 . Figure 13 a shows the
full sinusoid of the input voltage. Even when set to full brightness, few dimmers will provide 100% on-time, i.e.,
the full sinusoid.
(a)
(b)
DELAY
?
?
DELAY
(c)
Figure 13. Line Voltage and Dimming Waveforms
Figure 13 b shows a theoretical waveform from a dimmer. The on-time is often referred to as the "conduction
angle" and may be stated in degrees or radians. The off-time represents the delay caused by the RC circuit
feeding the triac. The off-time be referred to as the "firing angle" and is simply 180° - θ .
Figure 13 c shows a waveform from a so-called reverse phase dimmer, sometimes referred to as an electronic
dimmer. These typically are more expensive, microcontroller based dimmers that use switching elements other
than triacs. Note that the conduction starts from the zero-crossing, and terminates some time later. This method
of control reduces the noise spike at the transition.
Since the LM3445 has been designed to assess the relative on-time and control the LED current accordingly,
most phase-control dimmers, both forward and reverse phase, may be used with success.
8
Product Folder Links: LM3445
Copyright ? 2009–2013, Texas Instruments Incorporated
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相关代理商/技术参数 |
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|---|---|
| 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 |
| LM3447-A19-120VEVM | 功能描述:LED 照明开发工具 LM3447 Eval Mod RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: |
| LM3447-A19-230VEVM | 功能描述:LED 照明开发工具 LM3447 Eval Mod RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: |
| LM3447MT | 制造商:TI 制造商全称:Texas Instruments 功能描述:a Phase-Dimmable, Primary-Side Regulated LED Driver |
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