A Single-Stage Fully Bridgeless Resonant Soft-Switched Isolated SEPIC-based Charger for LVEVs

A single-stage charger for low-voltage electric vehicles (LVEVs) based on a fully bridgeless, zero-voltage switching (ZVS), isolated single-ended primary inductor converter is presented in this work. On contrary to many of the converters of bridgeless type available, the presented charger consists of a completely bridgeless structure, and uses only one switch in the main circuit, while another switch, which is auxiliary, is used to incorporate ZVS through an additional resonant switch network. The charger, therefore, has the capability to operate at increased frequencies of switching, without having the risk of losses due to the switching of the semiconductor devices. The charger operation consists of both pulse width modulated (PWM) and resonant mode of operation within each switching cycle, which results in the zero-voltage switching-on of the switch in the main circuit, along with the auxiliary switch turning off at zero-current, thereby, diminishing the switching losses associated with them. Moreover, output diode current falls to zero at the end of the switching cycle, thereby, reducing the reverse-recovery losses incurred in the high frequency diode. In addition to this, the single-stage charger maintains the grid power factor, and is also capable of ensuring proper battery charging. This paper presents the detailed analysis and insight into the charger’s working, operational analysis, design and the results for a charger power, input AC voltage and battery nominal voltage of 450W, 220V (RMS) and 4SV respectively.