LM3450EV120V15W: 350mA @ 45V Max, 120V in

The LM3450 evaluation board is designed to provide an AC to LED solution for a 15W LED load. Specifically, it takes an AC mains input and converts it to a constant current output of 350mA for a series string of 1 to 14 LEDs (maximum LED stack voltage of 45V). There are two assembly versions designed to operate from two different nominal AC input voltages, 120VAC or 230VAC.

The board employs a two stage design with an LM3450 flyback primary stage and an LM3409 secondary stage. The LM3450 provides an isolated 50V regulated output voltage and a power factor corrected input current. The LM3409 uses the 50V flyback output as its input and provides a constant current of 350mA 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.