Modeling and Measurement of Conducted EMI Suppression Elements for Switch-Mode Power Supplies Based on the Inverse Piezoelectric Effect

To suppress interference peaks in the low-frequency range of switch-mode power supplies (SMPSs), passive electromagnetic interference (EMI) filters typically require the use of common-mode inductors (CMIs) with higher inductance values. This results in an increase in the volume and weight of SMPSs, as well as a decrease in their efficiency. Therefore, this article proposes a method for modeling and measurement of conducted EMI suppression elements for SMPSs based on the inverse piezoelectric effect. When piezoelectric ceramics undergo the inverse piezoelectric effect, they vibrate in different modes and generate multiple resonances. At the resonance frequencies, piezoelectric ceramics can provide low-impedance propagation paths for conducted EMI, thereby leading to the attenuation of discrete interference peaks. This article establishes a model between the resonance frequencies and the dimensions under multiple vibration modes of piezoelectric ceramics, based on their equivalent electrical circuits and resonance properties. The established model enables the synergistic design of resonance frequencies for multiple vibration modes by altering the dimensions of piezoelectric ceramics, thereby achieving significant attenuation of interference peaks at multiple specific frequencies in SMPSs. According to the measurement results, under the same EMI standard, using the piezoelectric ceramics to replace the Y-capacitors as a conducted EMI suppression element in the passive EMI filter can reduce the volume of the CMI by 88% and its weight by 83%, thereby lowering the cost of the SMPS and improving its efficiency.