Designs a passive filter ( input filter ) for power applications

Optimal design of passive filters, also known as input filters, EMI filters

function [ stg_Ld, stg_Rd, att ] = filter_damping_design( stg_L, stg_C, fs, Zmax)

Written by Dr. Yoash Levron

for a quick start: copy all files to your Matlab directory and run the attached example file.

Attached files:
filter_damping_design - This is the main function
filter_circuit_sketch.pdf - A sketch showing the filter circuit.
filter_damping_design_example - An example file.
tf_filter - An auxiliary function that computes the transfer function of a given filter.

This function designs the optimal L-R damping network for a multistage passive filter, a network that achieves the best attenuation at a desired switching frequency fs, and has an output impedance smaller than a specified threshold Zmax, over all frequencies. The number of stages may be 1,2 or 3.
The damping inductors, if placed at all, are chosen to be equal, so practical filters can be built using the same inductor, reducing cost. The attached PDF file shows the topology and component names.

Inputs:
stg_L - [H] specifies the primary inductors at each stage. This is a vector with 1, 2 or 3 components.
stg_C - [F] specifies the primary capacitors at each stage. It is the same length as stg_L.
fs - [Hz] desired switching frequency to attenuate.
Zmax - [ohm] desired maximal output impedance (over all frequencies).

Output:
stg_Ld - [H] the resulting damping inductors.
stg_Rd - [ohm] the resulting damping resistors.
att - [dB] the resulting optimal attenuation at frequency fs.