This article proposes a single-phase two-stage three-level AC/DC converter using variable DC bus voltage control. This topology structure is a new combination of cascaded three-level totem-pole power factor correction circuit and three-level LLC half-bridge converter. This article calculates the power loss of the system in detail, describes the control strategy of the topology, and provides corresponding simulation waveforms. Compared with traditional two-level converters, the overall efficiency of the PFC side has been improved by about 0.7%, and the peak efficiency of the entire converter has reached 96.84%.