The ultrasonic generator generates a signal with a specific frequency, which can be a sine signal or a pulse signal. This specific frequency is the frequency of the ultrasonic transducer. Generally, the ultrasonic frequencies used in ultrasound equipment are 25KHz, 28KHz, 35KHz and 40KHz；. 1OOKHz, the frequency above 100KHZ has not been widely used, but with the continuous development of technology, it is believed that the application area will gradually expand. A relatively perfect ultrasonic generator should also have a feedback link, which mainly provides feedback signals from two aspects:  

      First of all, the output power signal is provided. We know that when the voltage of the ultrasonic generator changes, the output power of the ultrasonic power supply will also change. At this time, the mechanical vibration reflected on the ultrasonic transducer is big and small, resulting in unstable cleaning effect. Therefore, it is necessary to stabilize the output power, and adjust the power amplifier accordingly through the power feedback signal to make the power amplification stable.  

      The second is to provide the frequency tracking signal. When the ultrasonic transducer works at the resonant frequency point, its efficiency zui is high and its working zui is stable, but the resonant frequency point of the ultrasonic transducer will change due to assembly reasons and aging. Of course, the frequency of this change is only drift, and the change is not great. The frequency tracking signal can control the signal ultrasonic power supply, so that the frequency of the signal ultrasonic power supply can track the resonant frequency point of the ultrasonic transducer within a certain range, and the ultrasonic power supply can work in the * state.  

      Ultrasonic generator is divided into self-excited power supply and separately excited power supply according to design. Self-excited circuit has no signal source, which integrates oscillation, power amplifier, output transformer and transducer to form a closed loop. The loop meets the amplitude and phase feedback conditions to form an oscillator with power amplification. And resonates at the mechanical resonance frequency of the transducer. Generally applied to small equipment with a small number of ultrasonic transducers; However, in the case of a large number of ultrasonic transducers, it can't be debugged to achieve resonance effect. Therefore, at present, the ultrasonic generators of industrial ultrasonic cleaning equipment mostly adopt separate excitation mode. Ultrasonic generator of welding machine generally adopts self-excited ultrasonic generator.