Conducted interference suppression for Switched-Mode power supplies based on an impedance resonance design of piezoelectric ceramics

Suppressing low-frequency conducted interference noise in switched-mode power supplies (SMPS) often presents a challenge. Therefore, this paper proposes a piezoelectric ceramic impedance resonance design method for suppressing conducted interference in SMPS. The advantage of piezoelectric ceramics lies in generation of a lower impedance path near their resonant frequency than capacitors of the same capacitance. In contrast to traditional filtering approaches, the proposed method selectively provides greater attenuation to the peak of conducted interference in SMPS, resulting in increased power density for the SMPS. Additionally, a model correlating the impedance of piezoelectric ceramics to their sizes is established. Based on this model, the sizes of piezoelectric ceramics are designed for the flyback converter. Finally, the interference suppression effect of the designed piezoelectric ceramics is experimentally verified. The experimental results demonstrate the effectiveness of the proposed resonance point design method. In addition, compared to the traditional filter, the method proposed in this paper reduces the weight of the filter by 43.3% and its size by 45.2%.