An innovative DC busline active snubber-assisted soft switching PWM DC-DC power supply with high frequency transformer for high performance arc welder

This paper presents three novel circuit topologies of voltage source soft switching PWM inverter with full-bridge or half-bridge configurations suitable for either utility ac 200 V-rms or ac 400 V-rms input arid line. The proposed power converters are composed of typical full-bridge or half-bridge inverter and additional power semiconductor switching devices for dc busline PWM series switching with the aid of lossless capacitive snubbers. Under the newly-proposed soft switching PWM dc-dc power converter circuits with high frequency transformer, all the active power switches in the full-bridge arms or half-bridge arm and dc busline can actively achieve ZVS turn-off and ZCS or ZVS/ZCS turn-on commutation operation and consequently the total turn-off switching losses can be significantly reduced. As a result, a high switching frequency for used IGBTs can be actually realized more than about 20 kHz. It is proved that the more the switching frequency of full-bridge or half-bridge inverter increases, the more soft switching PWM dc-dc power converter with a high frequency transformer has remarkable advantages for its power conversion efficiency and power density as compared with the conventional hard switching PWM inverter type dc-dc converters. The effectiveness of this new converter topologies are proved for low voltage and large current dc-dc power supplies as arc welding machine from a practical point of view.