点焊逆变电源的恒峰值电流控制方法研究

摘要

Constant current peak control system of spot-welding inverter was designed with core of DSP. With the designed processing circuit, the current of medium welding transformer was rectified and processed in the entire range. Based on EV of DSP and software programming, dead-zero time and phase-shifting angle of PWM for spot-welding inverter was regulated. Timers of the EV operated in continuous increase and decrease model, then the output signal of the processing circuit was accurately sampled during comparing interrupts. The incremental digital PID algorithm with limitation was adopted to adjust phase-shifting angle of PWM real-timely, so that the constant current peak closed-loop control was achieved. The experimental results show that the designed circuit and algorithms can exactly produce phase-shifting PWM signal with dead-zero time to keep the current at a constant level, also assure the current symmetry, and the welding power operates stably for a long time.%介绍了一种点焊逆变电源恒峰值电流控制方法.其中包括信号调理电路完成对中频焊接变压器原边交变电流信号的全量程整流和调理；DSP事件管理器(EV)模块,结合软件编程,可实现点焊逆变电源主电路开关管PWM驱动信号死区时间和移相角的调节；EV模块中的定时器采用连续增/减计数模式,在比较中断中,对经过整流、调理后的电流信号峰值进行准确采样；增量式PID数字控制算法,实时调节PWM驱动信号的移相角,实现电流恒峰值反馈控制.实验结果表明,设计的硬件电路和软件算法可以准确产生带死区的移相PWM信号,实现了点焊逆变电源的恒峰值电流控制,保证了焊接电流的对称性,使焊接电源能够长期稳定工作.