Three-Terminal Noise Source Extraction From a Qi-Based Wireless Power Transfer System for Predicting Conducted Emissions

An equivalent method to extract a three-terminal noise source from a Qi-based wireless power transfer system is proposed in this article. This method is capable of extracting a source for both the positive (P) and negative (N) lines with respect to the third terminal (the ground chassis or reference plane). The extracted sources are independent of the setup configuration and can be used to predict currents or voltages on the P and N lines on a setup that is different from the extraction setup. In the following article, a three-terminal model independent of the setup configuration is first extracted. The extracted sources are then verified by predicting currents on a setup that is different from the original setup (such as a different load impedance and height of the device above reference plane). Finally, the extracted sources are used to predict the voltages on a 1-m cable harness. The predicted currents and voltages agree within 5 dB against measurement data over a frequency range from 0.5 to 30 MHz. The proposed method can be used to predict currents and voltages on any power converter with a single-phase input configuration.