Patent ID: 7382080

Claim:
A piezoelectric ultrasonic motor driver comprising: a piezoelectric ultrasonic motor including a metal body having a desired shape to serve as a stator, and a plurality of piezoelectric plates attached to surfaces of the metal body, wherein the piezoelectric plates contracts and expands to rotate the metal body if electrical signals are applied to the piezoelectric plates; a self-oscillation unit for oscillating at an electromechanical resonant frequency of the piezoelectric plates and allowing a frequency of an electrical signal applied to one of the plurality of piezoelectric plates to be maintained at the electromechanical resonant frequency of the piezoelectric plates; and a delay unit for delaying an oscillation signal of the self-oscillation unit in phase by 90 or −90 degrees according to a desired rotational direction, and applying the delayed signal to another of the plurality of piezoelectric plates, wherein the plurality of piezoelectric plates include first and second piezoelectric plates opposing each other and third and fourth piezoelectric plates opposing each other, the first to fourth piezoelectric plates being provided on the surfaces of the metal body, and wherein the self-oscillation unit comprises: a first capacitor provided between the first piezoelectric plate and the ground; a second capacitor provided between the second piezoelectric plate and the ground; a feedback resistor provided between a node between the first capacitor and the first piezoelectric plate and a node between the second capacitor and the second piezoelectric plate; and a first inverter connected in parallel to the feedback resistor, and wherein the direction of polarization of the first to fourth piezoelectric plates is from a center of the metal body to the outside.