General Impedance Representation of Passive Devices Based on Measurement

Noise propagation from power stages of power converters to their low-voltage control boards depends on multiple complex paths, generally created by parasitic capacitors across isolation barriers. These barriers can be easily crossed by the high frequencies (up to 100 MHz [5]) generated by new semiconductor technologies such as SiC and GaN resulting in compromised signal integrity on the control side. A common approach to overcome this problem is by using filter. However, due to the presence of several complex propagation paths, DM and CM modes are not properly defined at board level, causing difficulties to predict filter's performance. To cope with this issue, the node-to-node impedance function (NIF) is proposed to identify the impedance of all possible propagation paths in the filter. In the considered frequency range (>30 MHz), NIF parameters identification precision is altered by the impedance of shorting paths used in measurement procedure. In this paper, an optimization procedure based on Newton-Raphson algorithm is proposed to remove these errors. This improved version of NIF is named General Impedance Representation (GIR). Thanks to its generality, the GIR can also applicable for all kinds of passive devices. Experimental results are presented to confirm the effectiveness of GIR.