A novel half-bridge drive circuit for ultrasonic motor based on FPGA

A switching circuit system based on FPGA is designed and implemented in this paper to provide high- frequency adjustable-phase voltages for the ultrasonic motor. For the existing drive systems of the ultrasonic motor, the bus voltage is usually 12 V DC or 24 V DC supporting by an external adapter, the driving voltages of the ultrasonic motor, however, are required to be boosted yet. Then, the step-up transformers are always necessary. Different from that, the novel half-bridge based drive designed in this paper directly applies grid voltage of 220V, 50Hz as the AC input; that is, the external power adapter and the transformers are not necessary anymore. The cost and volume of the drive are subsequently reduced. Furthermore, the input voltages of the ultrasonic motor can be adjusted easily by changing the switching frequency and the conducting time. Meanwhile, a high-order matching circuit is introduced for stabilizing the voltage gain within its operating frequency bandwidth, which leads to a more stable speed regulation performance.