Piezoelectric EMI Filter

Due to the potential negative effects of EMI on neighboring components or devices, manufacturers have legal responsibilities to fulfil strict EMI standards, such as the CISPR 22 standard. This is typically addressed by means of filters consisting of capacitors and chokes. These cannot selectively target specific disturbance peaks and are rather ineffective at low frequencies. Thus, conventional EMI filters lead to a considerable increase in the cost and size of an electric device.

As EMI typically arises at higher harmonics of the switching frequency of an electric device, its frequency composition is largely predictable. The geometry of the PISC, and thereby its resonance frequency, can thus be tuned to fit a desired disturbance peak. By specific design, several peaks can even be resonantly attenuated by the same element or group of elements. Thereby, the PISC will typically be smaller than the regular capacitor it replaces. Moreover, the choke used to reduce residual high-frequency EMI not sufficiently addressed by the PISC to below the CISPR 22 boundary can also be smaller than for a regular capacitor.