How to choose input filter component value for power supply

Question

I understand that normally we'll modify the input filter after some measurement to meet the emission standard, but does anyone know on how we can estimate the initial value of this filter components especially during initial design stage (before the emission measurement was done)? Do we have any calculation reference to estimate this part value?

I read a lot of power supply guidelines from supplier however they don't cover so much on this item.

What I know is improper LC design could lead to oscillation to power supply, can anyone suggest any good method/approach to design the input filter?

Thanks

Answer 1

To handle the very fastest of spikes, which likely will be what causes failure, you need some sort of ground plane under the filtering components.

100 microH inductance (size dependent on current) and 100 microF will produce 1,600 Hertz resonance followed by attenuation.

Place a ONE ohm resistor in series, for near optimal dampening. Size the resistor to handle the current.

Common-mode chokes may work better.