User's Guide
SNVA485B – June 2011 – Revised May 2013
AN-2150 LM3450A Evaluation Board
1
Introduction
The LM3450A evaluation board is designed to provide an AC to LED solution for a 30W LED load.
Specifically, it takes an AC mains input and converts it to a constant current output of 700mA for a series
string of 1 to 13 LEDs (maximum LED stack voltage of 45V). There are two assembly versions designed
to operate from two different nominal AC input voltages, 120V
AC
or 230V
AC
. .
The board employs a two stage design with an LM3450A flyback primary stage and an LM3409HV
secondary stage. The LM3450A provides an isolated 50V regulated output voltage and a power factor
corrected input current. The LM3409HV uses the 50V flyback output as its input and provides a constant
current of 700mA to the LED load. This two stage design provides excellent line and load regulation as
well as isolation. The board is comprised of two copper layers with components on both sides and an FR4
dielelctric.
The two-stage design has several key advantages over a single stage design including:
•
No 120Hz LED current ripple
•
Better dimming performance at low dimming levels.
•
Better line disturbance rejection
•
Better efficiency using small LED stack voltages
2
Specifications
120V
AC
30W Version
•
Input Voltage Range: V
IN
= 90V
AC
– 135V
AC
•
Regulated Flyback Output Voltage: V
OUT
= 50V
•
Maximum LED Stack Voltage: V
LED
< 45V
•
Regulated LED Current: I
LED
= 700mA
230V
AC
30W Version
•
Input Voltage Range: V
IN
= 180V
AC
– 265V
AC
•
Regulated Flyback Output Voltage: V
OUT
= 50V
•
Maximum LED Stack Voltage: V
LED
< 45V
•
Regulated LED Current: I
LED
= 700mA
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1
SNVA485B – June 2011 – Revised May 2013
AN-2150 LM3450A Evaluation Board
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