Influence of Spurious Modes on the Efficiency of Piezoelectric Transformers: A Sensitivity Analysis

An analysis of the efficiency degradation resulting from spurious modes in piezoelectric transformers (PTs) is presented in this article. Circuit analysis is performed on PT equivalent circuit models with both a single resonant branch and with two resonant branches (spurious mode included), allowing the efficiency degradation from a spurious mode to be analyzed. Multiple sensitivity analyses were then performed, highlighting frequency difference (between modes) and characteristic impedance of the spurious resonant circuit ({\sqrt {{L_2}/{C_2}} {}}) as critical design parameters for minimizing efficiency degradation from spurious modes. These two parameters are further analyzed to determine optimum design conditions to ensure minimal efficiency degradation. Results of this analysis provide a method of estimating whether a spurious mode will degrade efficiency and consequently provide a method for improving PT designs.