为了满足市场的需要，特研制了ＷＳ－１２０Ａ直流氩弧焊机。本文对该焊机的电路结构及工作原理进行了简单的介绍和分析，对主回路、控制回路（锯齿波电路、移相触发电路及反馈电路等）做了较为详细的分析。试验结果表明：该焊机起弧容易，稳弧效果好，结构紧凑，重量轻，调节方便。 In order to meet the needs of the market, special development of the WS-120A DC TIG welder. In this paper, the circuit structure and working principle of this welding machine are briefly introduced and analyzed. The main circuit, control loop (sawtooth circuit, phase shift triggering circuit and feedback circuit) are analyzed in detail. The test results show that the arc welding machine is easy to arcing, good arc stabilizing effect, compact structure, light weight and convenient adjustment.