input filter - goose1987/buck-CC-CV GitHub Wiki

Assumption

make some arbitrary assumption to constrain design

• output ripple : 20mVpp
• input current ripple : 50mVpp

Since high voltage(100V+) ceramics are difficult to procure, use an parallel R+L damping to minimize input capacitance requirements. Use the same planar core design as output inductor to keep BOM simple.

calculations : https://github.com/goose1987/buck-CC-CV/blob/master/stability/input_filter.m

filter impedance and converter input impedance @ different output loading

keep filter impedance lower than converter input impedance over operation range

current attenuation through filter

Components

• 8 X 2.2uF 250V ceramic
• 5T EQ25/6 N87 inductor
• 1 ohm 0.5W resistor
• 6.8uH 1A inductor