How to balance an ultrasonic transducer

What’s ultrasonic transducer

Ultrasonic transducers are devices that convert sound energy and electrical energy. Sound energy and electrical energy can be converted to each other.

Ultrasonic transducers can be divided into two categories according to material, one is a magnetostrictive transducer, and the other is piezoelectric transducer.

The main circuit of the ultrasonic transducer includes: a rectifying and filtering circuit, a DC chopping (steady) voltage circuit, a half bridge inverter circuit, a matching circuit, and an ultrasonic transducer. The control circuit is composed of a voltage regulation control circuit, an inverter control and a protection circuit.

Circuit design is an important part of the design. The circuit of the generator inverter power supply and the selection of the main circuit switching device are different. It is necessary to have different design of the inverter main circuit, drive circuit, sampling circuit, startup circuit and protection circuit. Program.

The transducer should have the following features:

1 A good matching circuit ensures that the generator supplies enough power to the transducer and converts the most efficient conversion of electrical power into acoustic energy.

2 Frequency adaptive function. Because the mechanical resonance frequency of the transducer itself is sensitive to load changes, heat generation, and other external influences, their changes cause the resonant frequency of the transducer to change, resulting in vibrational detuning and amplitude reduction of the system.

3 power adaptive function. In the working process, the output power can be automatically changed with the load. The ideal state is that the output voltage of the generator is constant, the output power is minimum at no load, and the output power is also increased when the load increases. This is beneficial to the operation of the ultrasonic device. This can be achieved by analyzing the load characteristics of the ultrasonic transducer and selecting the appropriate resonant frequency point. Alternatively, a chopper circuit can be used to control the input to the inverse by changing the duty cycle of the switching tube. The voltage of the variable circuit makes the duty ratio become larger as the load becomes larger, the output power can be kept constant, and the switch can be turned off when a fault occurs.

The ultrasonic generator matches the transducer include two ways:

First, make the generator output the rated electric power to the transducer by matching. This is because the generator needs an optimal load to output the rated power, and the impedance of the transducer is converted into the optimal load, that is, the impedance transformation. effect.

Second, the generator output efficiency is maximized by matching. This is because the transducer has electrostatic resistance, which causes a certain phase difference between the output voltage and current at the operating frequency, so that the output power cannot obtain the desired maximum output. The output efficiency of the generator is reduced, so that an opposite resistance is applied to the generator output or on the string, so that the generator load is pure resistance, that is, tuning.