Design of a novel ZVT soft-switching chopper

This paper presents a simple soft-switching chopper scheme with fixed timing control. A near-zero-voltage transition (near-ZVT) switching condition is realized by adding one auxiliary resonant snubber branch to a full-bridge two-quadrant chopper. The turn-off loss is reduced by lossless snubber capacitors in parallel with the main switches. The proposed design approach is to realize true ZVT at the rated load and near-ZVT under all other load current conditions. Computer simulation and hardware experiments have been implemented to verify the proposed concept, and the resulting voltage and current waveforms are shown from 30% to 150% load conditions in this paper. Under near-ZVT switching, the switching loss and dv/dt of the power device can be significantly reduced, and the reverse recovery problem of main switches can be avoided as compared to the hard-switching case. The design criteria for the resonant components are described with a practical example that has been used in a commercial magnetic levitation system. Under different load current conditions, the proposed design methodology has been fully verified with simulation and experimental results.