LLCC resonant inverter for piezoelectric ultrasonic motor drive

An LLCC resonant circuit is implemented in this study to build a high-frequency two-phase voltage source inverter for the piezoelectric ultrasonic motor (USM). A single-phase equivalent model of the USM is described. The operating principle and detailed analysis of the proposed driving circuit, in which the inherent parasitic capacitances formed by the polarized piezoelectric ceramic of the USM are parts of the two LLCC resonant circuits, are introduced. Since the dynamic characteristic of the USM is greatly influenced by the variation in the Q of the RLC resonant tanks, the drive will be operated about a geometric frequency where the amplitude and phase of the two-phase output voltages of the resonant inverter would not be influenced by the variation in Q. Detailed experimental results are provided to demonstrate the effectiveness of the proposed driving circuit.