Impedance Matching Of Ultrasonic Plastic Welder

In the ultrasonic welding process, the impedance matching of the ultrasonic plastic welder is very important. In the process of ultrasonic work, it is often encountered that the equipment does not have enough power to complete the process. The reason is that the optimal load of the ultrasonic power supply does not match the equivalent resistance of the transducer, resulting in the energy cannot be effectively transmitted. At this point, the need for impedance transformation, the equivalent resistance of the transducer through impedance transformation and ultrasonic power output impedance matching, to ensure the transmission of energy, this is the ultrasonic wave impedance matching, impedance matching is also the matching circuit to complete a function, we usually use the method of the output transformer or shunt capacitance.

The above is just some basic theoretical and practical knowledge of circuit matching in power ultrasonic technology. The actual matching circuit design and debugging is quite complicated. There are many reasons for this!

First, from the ultrasonic welding generator circuit itself, adopt the different formats of amplifying circuit and the design of circuit working point is different, the output of the generator impedance is different and change as the work state of the circuit, the output impedance will change, thus it is difficult to ensure the permanent ideal match ultrasonic transducer.

Second, there are many characteristic frequency ultrasonic welder transducer, such as series resonance frequency, parallel resonant frequency and resonant frequency, anti-resonant frequency and minimum admittance frequency and maximum frequency admittance, etc., in actual work, due to the different boundary conditions of transducer (including electrical and mechanical boundary conditions), it is difficult to guarantee the ultrasound transducer working on a particular resonant frequency.

Third, in the high power state, the matching becomes more complicated due to the change of load and the change of the parameters of the transducer itself (among which the change of frequency and impedance is the most important). In view of the above considerations, it can be said that electrical matching is the most complicated work in the development of high-power ultrasonic equipment.

In the actual matching debugging process, on the one hand, we must first understand the performance parameters of the transducer, on the other hand, we must find the best matching conditions in the actual work, so as to achieve the best matching.

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