Effect of spurious resonant modes on the operation of radial mode piezoelectric transformers

This paper analyses both the intentional and unwanted resonant modes of radial piezoelectric transformers (PTs). lnitially, finite element analysis is performed to discover the type of spurious modes prevalent is radial mode PTs. From this, analysis is performed on these modes and a relationship between resonant frequency and geometry is found. The effect of spurious modes on the efficiency of a typical PT is simulated using an equivalent circuit model in LTSpice and Simulink. A number of design rules are generated based on the findings. Results show that, in most cases and by careful design, spurious modes can be avoided.