Advanced high frequency transformer linked soft switching PWM DC-DC power converter with utility AC dual voltage modes for low voltage and large current applications

This paper presents two new circuit topologies of dc bus line series active snubber assisted soft switching PWM full-bridge dc-dc power converter acceptable for either utility ac 200 V-rms or ac 400 V-rms input voltage source. One of proposed power converters is composed of a typical voltage source full-bridge high frequency PWM inverter using dc bus line side series switching devices with the aid of a parallel capacitive lossless snubber. All the active power switches in the full-bridge arms and dc bus line can achieve ZCS turn-on and ZVS turn-off 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 inverter increases, the more soft switching PWM dc-dc power converter with a high frequency transformer link has remarkable advantages for its power conversion efficiency and power density as compared with the conventional hard switching PWM inverter type dc-dc converter. The effectiveness of this new converter topology is proved for low voltage and large current dc-dc power supplies as arc welding machine from a practical point of view.

3. Introduction

Recently, a saturable inductor assisted ZVS-PWM full-bridge high-frequency inverter link dc-dc power converter [1] and lossless capacitors and transformer parasitic inductive components assisted soft switching dc-dc power converter with phase-shifted modulation control scheme in secondary-side of high frequency transformer [2] [5] have been developed and evaluated so far. These power converter circuit topologies are suitable for handling high output power more than about several kW, especially for high voltage and low current applications as new energy related power supplies. However, secondary magnetic switches or transformer secondary side semiconductor switching devices in these converter circuit topologies may cause large conduction loss when these power circuit topologies are adopted for low voltage and large current application as arc welding power supplies. Therefore, for the low voltage and large current application, a soft-switching dc-dc power converter with active switches in the primary side ofthe high frequency transformer is considered to be more suitable.