Off-Line TRIAC Dimmer LED Driver Demo Board
The demonstration board included in this shipment converts 90VAC to 135VAC input, and drives seven, or eight series connected LED’s at 350 mA average current. The LM3445 switching frequency is set at a nominal 225 kHz. This is a four layer board using the bottom and top layer for component placement. The demonstration board can be modified to adjust the LED forward current, the number of series connected LEDs and switching frequency. Refer to the LM3445 datasheet for detailed instructions. A bill of materials below describes the parts used on this demonstration board. A schematic and layout have also been included below along with measured performance characteristics.
PCB Layout
Top Layer
Bottom Layer
The above restrictions for the input voltage are valid only for the demonstration board as shipped with the schematic below. Please refer to the LM3445 data sheet for detailed information regarding the LM3445 device, and the application circuit.
Available also in Italian version: LM3445 - Driver per LED dimmabile a TRIAC senza fenomeni di Flicker
Read more: http://www.national.com/an/AN/AN-1935.pdf
- Ionela's blog
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why 90VAC?
I went through the application note and could not find any explanation really, why you would need to convert a value of 90VAC...
As far as I know, the US has 110VAC, and the normal countries have 220VAC so I was just curious where this value of 90VAC stems from...
Cristian
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