In the ultrasonic welding process, the impedance matching of the ultrasonic plastic welding machine is very important. During the ultrasonic work, it is often encountered that the equipment does not have enough power to complete the process. The reason is that the best load of the ultrasonic power supply is equivalent to the transducer The resistance is not matched, resulting in the ineffective transmission of energy. At this time, impedance conversion is required, that is, the equivalent resistance of the transducer is matched with the output impedance of the ultrasonic power supply through impedance conversion to ensure the propagation of energy. This is ultrasonic impedance matching, and impedance matching is also a function of the matching circuit. , Usually we use the output transformer or parallel capacitor method to achieve.

What has been mentioned above is only some basic theoretical and practical knowledge of circuit matching in power ultrasound technology. The design and debugging of the actual matching circuit is more complicated. There are many reasons for this!

First, in terms of the ultrasonic generator circuit itself, the output impedance of the generator is different due to the different formats of the amplifying circuit and the different operating points of the designed circuit. The output impedance of the generator is different and changes with the state of the circuit during operation. Changes must also occur, making it difficult to guarantee a permanent ideal match of the ultrasonic transducer.

Second, ultrasonic transducers have many characteristic frequencies, such as series resonance frequency, parallel resonance frequency, resonance frequency, anti-resonance frequency, minimum admittance frequency, and maximum admittance frequency. In actual work, due to the boundary of the transducer Different conditions (including electrical and mechanical boundary conditions), it is difficult to ensure that the transducer works at a certain resonance frequency.

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

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