步进追频及恒振幅控制的超声电源设计

针对超声金属焊接过程中出现的负载变化导致谐振频率漂移和焊接振幅失恒问题，设计了一种基于步进追频及恒振幅控制的超声电源。在负载变化对谐振频率影响的研究基础上，根据FPGA-DDS步进追频原理设计了负载变化追频逻辑；结合全桥逆变电路的移相控制方式，研究了不同占空比下的最大输入电流与最大焊接振幅的关系，提出了基于输入电流反馈下的步进移相恒振幅控制方案；实验结果表明，负载变化追频逻辑实现了谐振频率快速变化下的动态实时追踪，解决了因频率失谐导致的焊接振幅非线性下降问题。同时，在加入了振幅闭环控制后，实现了焊接振幅相对极差稳定在10%以内。

Ultrasonic power supply design based on FPGA-DDS stepping frequency tracking technology

Aiming at the problems of resonance frequency drift and weld amplitude loss caused by load changes in ultrasonic metal welding, an ultrasonic power supply based on step chasing and constant amplitude control is designed. Based on the study of the effect of load change on resonant frequency, the load change tracking logic is designed according to the principle of FPGA-DDDS step chasing, and the relationship between the maximum input current and the maximum weld amplitude under different duty cycles is studied, and the step-shift phase constant amplitude control scheme based on input current feedback is proposed. Solved the problem of nonlinear decrease in weld amplitude due to frequency detuning. At the same time, after adding the amplitude closed-loop control, the relative amplitude of the welding amplitude is stabilized within 10%.