An energy-efficient circuit for driving PZT actuators using a charge recovery technique is explored in this paper. Mobile and wearable devices for physical assists requiring extended battery life and/or minimal battery weight will benefit from this technology. PZT is a capacitive transducer and can produce constant force for extended periods with little power consumption. Furthermore, energy can be saved by moving charge from one PZT stack to another instead of draining to ground. This paper describes an efficient charge-recovery circuit that can capture 40∼65% of the energy in one PZT unit by transferring it to another PZT unit. The battery then must only supply the remaining charge thereby increasing battery life. First, the basic principle of the charge-recovery technique is described. The idealized circuit architecture and possible implementation are presented. Then, the electrical circuit behavior is analyzed. PZT hysteresis is discussed, and results are presented.

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