User manual

LM3445 - 230VAC, 6W- 15W
Isolated Flyback LED Driver
National Semiconductor
Application Note 2069
Montu Doshi
November 23, 2010
Introduction
This demonstration board highlights the performance of a
LM3445 based Flyback LED driver solution that can be used
to power a single LED string consisting of 4 to 10 series con-
nected LEDs from an 180 V
RMS
to 265 V
RMS
, 50 Hz input
power supply. The key performance characteristics under
typical operating conditions are summarized in this applica-
tion note.
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 se-
ries connected LEDs that are driven and the switching fre-
quency. Refer to the LM3445 datasheet for detailed instruc-
tions.
A bill of materials is included that describes the parts used on
this demonstration board. A schematic and layout have also
been included along with measured performance character-
istics.
Key Features
•
Drop-in compatibility with TRIAC dimmers
•
Line injection circuitry enables PFC values greater than
0.94
•
Adjustable LED current and switching frequency
•
Flicker free operation
Applications
•
Retro-fit TRIAC Dimming
•
Solid State Lighting
•
Industrial and Commercial Lighting
•
Residential Lighting
Performance Specifications
Based on an LED V
f
= 3.4V
Symbol Parameter Min Typ Max
V
IN
Input voltage 180 V
RMS
230 V
RMS
265 V
RMS
V
OUT
LED string voltage 13 V 20 V 27 V
I
LED
LED string average current - 350 mA -
P
OUT
Output power - 7.2 W -
f
sw
Switching frequency - 67 kHz -
Demo Board
30126904
Dimming Characteristics
30126924
© 2010 National Semiconductor Corporation 301269 www.national.com
LM3445 - 230VAC, 6W- 15W Isolated Flyback LED Driver AN-2069