User manual

www.ti.com

Design Calculations

Z(D7)

=12V

R8=49.9kΩ

GS(Q1)

=0.7V

14.2 Preliminary Calculations

Nominal peak input voltage:

(29)

Calculate minimum on-time and verify it's greater than 200ns:

(30)

Calculate off-time:

(31)

From Figure 29, choose R14=2.0Ω for 6.5W output power with 12 LEDs.

14.3 FLTR2 AC-LINE Injection

Choose V

INJECT(NOM)

=1.0V

Choose R2=R7=274kΩ

Calculate R15:

(32)

or,

(33)

Calculate maximum FLTR2 pin voltage and verify it is less than 1.25V:

(34)

Calculate minimum FLTR2 pin voltage:

(35)

SNOA559B–October 2011–Revised May 2013 AN-2127 LM3448 A19 Edison Retrofit Evaluation Board

Submit Documentation Feedback