A Novel Dual-Probe Method for Noise Source Impedance Extraction

Le résumé fourni par la source

The impedance of noise source is an important index of EMI research which is an indispensable part of both the study of the actual attenuation effect of EMI filter and the prediction of EMI interference. The PCB of the power supply, along with components such as heat sinks and cables, may exhibit parasitic capacitance, which can carry ripple voltage and generate significant interference. The un-certainty introduced by parasitic capacitance complicates the noise coupling mechanism, making it difficult to derive and establish a complete and accurate theoretical model. As a result, impedance extraction of power supply noise must be performed through testing. This paper proposes a method for impedance extraction based on the implementation of a spectrum analyzer. Compared to traditional impedance extraction methods, this approach offers the advantage of being non-invasive. The method does not require modifying the original circuit structure and allows impedance extraction while the power supply operates normally. Based on this method, an impedance extraction device for source impedance is designed, and the impact of test dynamic range and signal-to-noise ratio on the test results is discussed. To verify the accuracy of the proposed method, impedance extraction is performed on a known impedance network, a 50Ω signal source, and a DC-DC converter. This method provides significant guidance for EMI filter design. By using the extracted power supply noise impedance for EMI filter parameter design, efficient EMI filters can be developed that effectively eliminate noise while maintaining a small volume and size, thereby improving the power density of the power supply.

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