Series-parallel load-resonant converter for controlled-current arc welding power supply

An are welding power supply requires the ability to limit the load current under short circuit conditions and limit the load voltage under open circuit conditions. The series-parallel load-resonant converter is a circuit configuration which can achieve this. The potential for high frequency operation in these converters minimises the size of the magnetic components in the converter and reduces output current ripple. The paper presents the theoretical and practical aspects of the design and construction of a series-parallel load-resonant converter, for use as a controlled current are welding power supply. A converter with an output voltage of 25V and output current of 200A operating at 85kHz is designed and constructed. A novel method of control of the resonant converter is described. Output power control is achieved by using an active rectifier modulating the DC supply voltage to the converter. Practical results of the converter in operation supplying 200A to a low inductance load are presented.