An EMI suppression method based on impedance characteristics modeling and measurement of piezoelectric ceramics

Abstract

To ensure that the low-frequency conducted interference of switch-mode power supplies (SMPSs) meets electromagnetic compatibility standards, it typically requires the use of chokes with high inductance values. This approach not only increases the size and weight of SMPSs but also reduces their power density. Therefore, this paper proposes an electromagnetic Interference (EMI) suppression method based on impedance characteristics modeling and measurement of piezoelectric ceramics (PZTs). A PZT can generate a low-impedance propagation path for conducted interference at its resonance frequency. Based on this impedance characteristic, this paper establishes a model between the resonance frequency and the dimensions under the contour vibration mode of PZTs. By using this model, the resonance frequency of piezoelectric ceramics can be accurately predicted by designing their dimensions, thereby achieving targeted suppression of specific frequency EMI. Based on the measurement results, the PZT suppresses the interference peak at the switching frequency of the SMPS by 25.1 dB, which is 12.5 dB better than the traditional method. Additionally, using the PZT as a conducted interference suppression component in the passive EMI filter can reduce its volume by 68.18 % and weight by 70.52 %. This paper also analyzes the anti-resonance phenomenon generated by PZTs and how to utilize the method of parallel-connected capacitors to offset their negative impact. Finally, this paper investigates how to use the method of parallel-connected PZTs to suppress EMI at multiple frequencies in SMPSs to further improve the filtering efficiency of PZTs.