Patent ID: 6265809
Filing Date: 2001-07-24
Classification: H02N

Abstract:
A drive circuit for an ultrasonic motor comprising:a DC power source;a transformer for applying to the ultrasonic motor two phase high frequency voltage alternating currents having a predetermined phase difference for driving the ultrasonic motor;a switching device interposed between the DC power source and the transformer for allowing a direct current from the direct DC power source to flow to the transformer at a predetermined timing;a first temperature detecting device situated near the switching device for monitoring a temperature rise of the switching device; anda CPU connected to the switching device for controlling the switching device at the predetermined timing and to the first temperature detecting device, said CPU, when a temperature of the switching device detected by the first temperature detecting device is higher than a first set temperature, operating to stop driving of the ultrasonic motor or to lower an output of the ultrasonic motor less than a first predetermined output, and when the temperature becomes lower than a second set temperature lower than the first set temperature, the ultrasonic motor being re-started at an output higher than the first predetermined output.