An Improved Converter Design for Ultrasonic Welding Systems

An ultrasonic welding system typically consists of four components: power supply, PZT converter, booster and horn. Among them, PZT converter converts electrical power into mechanical power. To improve the power delivery, the input electrical impedance of converter should be reduced. In the present study, influences of piezoelectric ring thickness and thickness of matching and backing layers on the bandwidth of a converter were investigated. The results showed that the input electrical impedance can be reduced by 1) employing more active piezoelectric layers and 2) increasing the number of piezoelectric rings. Furthermore, widening the bandwidth of piezoelectric converter at its resonant frequency is also desired because of the possible variance of mechanical impedance of workpieces. In summary, new design methodology for converter in ultrasonic welding systems have been proposed and developed based on minimizing input impedance through the concept of transduction matrix.