The Simulation And Test Study Of Soft-Switching Spot-Welding Inverter Power Source

Inverter spot welding power source is one of important directions in the studies of the resistance-welding field. With soft-switching technology, inverter spot-welding power source has lower switching dissipation, lower electromagnetic interference and lower sensitivity to parasitic parameters of power circuit, contribute to inverter output characteristics and circuit efficiency, stability and reliability.The basic working principle of the phase-shifted PWM soft-switching topology DC/DC full bridge with assistance network is presented and analyzed in detail, and the circuit simulating software of Pspice is used for simulation in this paper. Zero-voltage turn-on and zero-voltage turn-off in lagging arm and leading arm of soft-switching topology, working waveform of power transformer and process of rectifier and transition are presented in detail. The influence of resonant inductance of the power transformer, resonant capacitor and variation of load to the process of soft-switching are given.By compared with the simulation results and the experiment results, we come to the conclusions that: (1) circuit with assistant network can widen soft-switching extent in lagging arm, reduces duty-cycle loss on the secondary, diminishes switching dissipation of inverter spot-welding power source. (2) The range of resonant capacitor, the important factor to soft-switching process, not only affects zero-voltage turn-off of power switches, but also affects the range of zero-voltage turn-on of power switches. So resonant capacitors must be considered according to many aspects; (3) It easily fulfils soft-switching condition in lagging arm as leakage inductance of power transformer increases, but bigger leakage inductance of power transformer increases opening dissipation of transformer and decreases efficiency of soft-switching inverter power source.In addition, the working principle, characteristics and compensation of the control system of current peak are deeply discussed; the PWM control circuit of using UC3875 as the core, the inputting over-voltage protecting circuit and owe-voltage protecting circuit are given, etc.