【作者】 胡双平；

【导师】 杨思乾；

【作者基本信息】 西北工业大学 ， 材料加工工程， 2004， 硕士

【摘要】 逆变式点焊电源是电阻焊领域研究的重要方向之一。采用软开关技术的点焊逆变电源，可减小开关损耗、电磁干扰及对电路寄生参数的敏感性，并从根本上改善电路的输出特性，提高电路的效率、稳定性和可靠性。 论文详细分析了带辅助网络的零电压脉宽调制DC／DC全桥变换器的工作原理，并利用Pspice电路仿真软件进行了仿真研究。主要对软开关滞后桥臂和超前桥臂的零电压开通、关断过程，功率变压器的工作波形及整流换流过程进行了详细的仿真分析，并重点讨论了逆变器的谐振电感、谐振电容以及负载变化对软开关过程的影响。 通过仿真结果与软开关点焊逆变器试验结果的对比分析，得到了如下主要结论：①采用辅助网络可以完全拓宽全桥软开关逆变器的滞后桥臂软开关范围，减小了次级占空比丢失，降低了逆变电阻点焊电源的开关损耗；②谐振电容是影响软开关工作状态的重要因素，其大小不仅影响开关管的零电压关断，同时也影响开关管的零电压开通范围，因此，谐振电容应该综合考虑；③功率变压器漏感越大，越容易满足滞后桥臂的软开关条件，但是大的漏感也使变压器的通态损耗增加，降低了软开关逆变器的效率。 此外，论文还对软开关逆变器峰值电流控制系统的原理、特性及补偿进行了深入的分析；设计了以UC3875为核心的移相PWM控制及输入过压、欠压保护等电路。更多还原

【Abstract】 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.更多还原