This Mathcad worksheet is offered to predict the stability of a voltage-sense, current-inject active EMI filter (AEF) circuit, in particular with respect to TI's TPSF12C1/3/-Q1 family of AEF ICs, and to assist with component selection. The model is inclusive of most parasitc effects and can be used as a quick check of the loop gain and insertion loss prior to simulation, bench measurement and fine tuning.
The worksheet functions for single- and 3-phase AC systems and facilitates two ways of entering the CM choke parameters:
1. Using an equivalent circuit model with (a) resistive and capacitive parasitics – suitable for ferrite-core chokes; (b) a ladder network of three parallel RL circuits -- suitable for nanocrystalline chokes
2. Using measured impedance data (magnitude and phase).
The worksheet is ideal for knowledge capture, unit-aware calculation reuse and for engineering collaboration amongst design, systems & application engineers.