On the Self-Regulation of Piezoelectric Transformers When Driving Atmospheric Pressure Plasma Jets

Atmospheric pressure plasma jets are effective tools for treating various media, but their widespread use is often hindered by the complications that come with using high-voltage electronics needed to drive plasma production. Piezoelectric transformers (PTs) offer an inexpensive, small-footprint alternative to the typical step-up transformers used in high-voltage systems. However, operational characteristics of PTs require consideration. Of note is the high output impedance, which creates a load sensitivity that significantly impacts performance. In this work, we examine the output of a PT used to drive plasma jets produced in helium and argon using a capacitive probe. The PT’s voltage gain was found to exceed 100, but it is highly dependent on the applied voltage, frequency, and plasma impedance. In the absence of a plasma, when the load resistance is large, the voltage gain is large. When the plasma forms, thus reducing the load resistance, the voltage gain decreases. During high-current plasma events, the gain was observed to drop to a lower value for several milliseconds before recovering. This load-dependent voltage gain creates a self-regulating effect that can be advantageously utilized to produce plasma jets, initially providing high-voltage gain to form the plasma, reducing gain as the plasma strengthens and preventing mode changes or arcing.