State-Space Modeling of a Novel 2-output, single-L Driver for PZT Actuators with Charge Recovery

The growing need for larger transduction forces to be applied by piezoelectric actuators leads to the increase of their footprint, capacitance and voltage level. This is in trade-off with low power dissipation needs, and thus new driving circuits shall be conceived. In this work a novel architecture based on a two-output, single-inductor, DC-AC converter is presented, which exploits a charge-recovery technique. It is of utmost importance to derive a linear time-invariant (LTI) model for such a switching circuit, so that a target driving waveform can be obtained on the piezoelectric actuators, depending on the duty cycle applied to the circuit switches. A state-space averaging technique and linearization is used to extract the LTI model of the proposed driver. The so computed equations are then exploited to predict the required duty cycles to generate, as a real-case scenario, a 56-V, 120-Hz sawtooth signal, typically used to drive MEMS micromirrors. The entire circuit model is finally validated by an open-loop behavioral simulation, showing a relative error deviation between the target and the obtained voltage waveforms smaller than 2.7%, with zero power dissipation in the assumption of ideal switches.