An FPGA- based multiple-output PWM pulse generator for ultrasonic cleaning machines

This paper presents design and implementation of a multiple-output 48 kHz PWM-controlled pulse generator for ultrasonic cleaning machines. The complete digital part including frequency and PWM-controlled pulse generator and display driver unit to drive four independent ultrasonic power units has been implemented on a single FPGA core. As a result, more precise (5Hz step) frequency adjustment and four independent but fully-parallel cleaning process control have been achieved. These are the advantages of the FPGA based solution when compared to the traditional microcontroller-based counterparts. The proposed generator has also been equipped with a feedback circuitry to recover the resonance frequency deviated by unstable cleaning tank loadings. A unique mathematical algorithm has been developed for this purpose. Although there are a few PWM generator designs based on FPGA technology, this work is believed to be the first attempt to employ the well-known concurrent hardware design advantages of FPGA technology especially in designing ultrasonic cleaning systems.