一种频率可调超声波发生器设计

不同清洗物所需的清洗频段不同，需要接入的超声波换能器也不同。为了提高超声波发生器对不同频段换能器的适应性，设计了一种由上位机进行频率给定、锁相环电路进行频率跟踪的闭环控制系统。整个系统由STM32主控制器产生脉冲宽度调制(PWM)脉冲信号，控制EXB841优化驱动电路，驱动高频全桥逆变电路；通过阻抗匹配和输出电流的检测，保证作用于换能器输出的功率值最大。同时对于不同频段的超声波换能器，需要调整给定输入，保持发生器在频率基准值的一定范围内进行频率跟踪。超声波换能器测试样机工作频率点为28.8 kHz，最大功率1 500 W，将本系统接入后谐振频率保持在28.8 kHz左右，输出功率近似为最大值。经测试，该系统对于工作频率点为20~40 kHz的超声波换能器都具有较好的适应性。

Design of an adjustable frequency ultrasound generator

In view of the different cleaning frequency ranges required by different cleaning materials in the industry, the ultrasonic transducers that need to be connected are also different. In order to improve the adaptability of the ultrasonic generator to transducers of different frequency ranges, this paper designs a closed-loop control system for frequency reference and frequency-locked loop circuit tracking by the upper monitor. The whole system generates Pulse Width Modulation(PWM) pulse signals by STM32 main controller. It controls the EXB841 optimized driving circuit, driving high frequency full bridge invert circuit, and ensuring the maximum output power of the transducer through impedance matching and output current detection. At the same time, for different frequency ranges of ultrasonic transducers, it is necessary to adjust the given input and keep the generator in a certain range of base-value for frequency tracking. The working frequency of the ultrasonic transducer test prototype is 28.8 kHz and the maximum power is 1 500 W. The resonant frequency of the system is kept around 28.8 kHz after the system is connected, and the output power is approximately the maximum. The test results show that the system has good adaptability to the ultrasonic transducer whose working frequency is 20-40 kHz.