Method and system for tracking resonant frequency of ultrasonic power supply

Abstract

The invention relates to a method and a system for tracking the resonant frequency of an ultrasonic power supply. The method comprises the following steps: S1, carrying out matched initial adjustment on the output frequency of the ultrasonic power supply and the resonant frequency of a transducer; S2, detecting a current signal output by the transducer; S3, constructing a differential link phase-locked loop; taking a current signal output by the transducer as an input signal of a differential link phase-locked loop; generating a driving signal according to the output signal of the differential link phase-locked loop; and S4, enabling the driving signal to control the output frequency of the ultrasonic power supply to change along with the change of the resonant frequency of the transducer. The differential link phase-locked loop is constructed, a DDS signal generator is combined with the differential link phase-locked loop to realize closed-loop control, and the output frequency of the ultrasonic power supply can quickly track the change of the resonant frequency of the transducer, so that the ultrasonic power supply works in a resonant state, the conception is ingenious, the tracking performance is good, and the implementation is easy.

Description

technical field [0001] The invention relates to the technical field of ultrasonic power supplies, in particular to a method and system for tracking the resonant frequency of ultrasonic power supplies. Background technique [0002] Ultrasonic power supplies are widely used in ultrasonic welding, ultrasonic processing, ultrasonic cleaning, ultrasonic motors and ultrasonic medical treatment. The ultrasonic power supply outputs a high-frequency AC signal that matches the transducer at the load end through rectification and filtering, full-bridge inverter, matching circuit, etc., and the function of the transducer is to convert the output electrical energy into mechanical energy. . [0003] However, as the transducer changes in temperature, vibration amplitude, and load during operation, its frequency characteristics will change slightly, resulting in a change in the center frequency, a decrease in the working efficiency of the transducer, and even damage to the transducer. ene...

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Problems solved by technology

Among them, the maximum current search frequency tracking method is based on the characteristic that the load impedance is the smallest and the output current is the largest in the resonant state. The frequency corresponding to the maximum current is searched by means of frequency sweep and variable step size, which is the resonant frequency. Due to the long sweep period, As the number of steps increases, the amount of feedback required also increases, resulting in longer start-up time and lower tracking accuracy; the matching inductance method is to change the output voltage by changing the size of the inductance in the matching circuit while keeping the output frequency constant and current phase difference to realize frequency tracking, this method has low tracking accuracy

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