| Ultrasonic metal welding technology has been widely applied and developed due to its advantages of low energy consumption,high efficiency,and environmental friendliness.With the development of new energy vehicle technology,the demand for high-stability,high-reliability,and fast battery component welding technology has become increasingly urgent.Currently,most of the large-scale electric vehicle battery welding equipment in China is based on foreign ultrasonic power technologies such as Branson and Herrmann,which are expensive and have high maintenance costs.In this paper,a metal welder ultrasonic power supply based on a dedicated frequency-locking chip technology is studied.Firstly,in response to the problems of slow frequency tracking speed and poor reliability in traditional ultrasonic power supplies,this paper designs a control scheme based on a dedicated resonant frequency-locking chip.Using a microcontroller and peripheral auxiliary circuits,an intelligent frequency locking control module is implemented,and the corresponding VCO circuit is designed.Combined with DDS technology,this module can intelligently track the working frequency of the transducer,improving the frequency control accuracy,tracking speed,and reliability of traditional ultrasonic metal welding power sources.The designed frequency tracking module achieves a frequency tracking time within 33 ms within the frequency range of 27～29 k Hz.Secondly,to address the problem of large voltage and current fluctuations of the ultrasonic vibrator during frequency tracking,a new matching circuit parameter selection scheme is studied.By modeling the electrical equivalent model of the transducer and the matching circuit and expanding the input signal into a Fourier series,a three-dimensional graph is calculated using Matlab to show the voltage and current changes of the ultrasonic vibrator with different matching parameters and working frequencies.The goodness of fit between the actual voltage curve and the theoretical voltage curve during no-load operation is 0.74.To address the problem of poor welding stability in traditional ultrasonic power supplies,a PFC circuit and energy control mode are added to the design.The PFC circuit can reduce the influence of grid fluctuations on the output power of the ultrasonic vibrator and,under the same load,increase the input power by 79.9%,and the power factor from 0.642 to 0.992.In order to realize the energy control mode,a welding energy calculation model is constructed by comparing and analyzing commonly used energy calculation algorithms.Accordingly,hardware-targeted phase-shifting circuits,multiplication circuits,filtering circuits,and DC bias circuits are designed,while software mainly adopts DMA storage technology.Test results show that the relative error fluctuation of the model is within-2.28% to 3.00%,and when working in energy mode,it can reduce the standard deviation of the actual energy consumption of ultrasonic welding from 49.5 to12.4.Finally,this paper verifies the ultrasonic metal welding power supply scheme based on the dedicated frequency-locking chip,and first compared and tested the performance of different ultrasonic power supplies.Then,the welding effect of double-layer 0.3mm thick copper sheets was studied,and the effects of welding pressure and time on the quality of copper welding were experimentally studied by measuring shear force and peeling force.The strength test results show that the ultrasonic metal welding equipment based on the optimized control scheme reduces the standard deviation of the shear force from 112.5 to 79.8,and the standard deviation of the peeling force from 41.8 to 27.6. |
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