In the paper, a novel AC/DC converter is proposed for the aging test of on-board charger in electric vehicles. This converter has advantages of unity input power factor, high efficiency, bidirectional energy flow, electrical isolation and wide range of output voltage. The converter consists of two identical topologies, which is made up of three cascaded converters. The front stage is a single-phase AC/DC rectifier and it realizes the unity input power factor. The next stage consists of a two-stage topology. The front stage of the two-stage topology is LLC resonant converter, which realizes electrical isolation, fixed voltage transfer ratio and natural bidirectional power flow. The back stage uses a bidirectional buck-boost converter to realize high dynamic performance and wide range voltage regulation ability. The feasibility and effectiveness of the proposed topology and control strategy are validated by the experimental results.