Research On Accurate Ultrasonic Welding Power Source

Ultrasonic metal welding has been widely applied in micro-electronics、 electricequipment, tube processing and other fields for its high efficiency, low-loss and cleanness, thefrequency tracing speed of Ultrasonic Welding Power Source(UWPS) and power adjustingfunction have an essential effect on welding process. Combined with direct digital synthesis（DDS）technology, phase shift pulse width modulation (PS-PWM), the design scheme whichis controlled by the core of digital signal processor（DSP） was proposed.The research work of this paper mainly includes:1）a full bridge inverter with MOSFETas switching devices is designed, as well as the isolating driven circuit;2）aimed at thedisadvantages of the traditional inductor matching method, an improving T-Matching networkis presented, which could achieve the impedance transforming and power transmission moreeffectively;3）in the aspect of frequency tracing，based on PI-DDS which combines therapidity of PI control and the precision of DDS，the frequency tracing system could realizequcik tracing of the transducer’s resonant frequency;4）phase-shift chip UC3879is adopted toadjust the output power of UWPS by shifting the phase shifting angle of the full-bridgeinverter. Meanwhile, with dsPIC33FJ64GS610as the core of the controlling system, thedeveloped UWPS could improve the response speed and control accuracy of the powersource.The experiment platform of UWPS is finally built as well as the software debuggingwork. The results demonstrated that the frequency-tracing system based on PI-DDS couldrealize the tracing of the transducer’s resonant frequency in0.44ms, which ensure the stabilityof the output amplitude. Besides, the PS-PWM could make the output voltage and currentcontinuous and adjustable. The developed UWPS can be applied in nonferrous metals such asC1100Copper and possesses engineering application value.