In this paper, a three-level Boost and integrated LLC multi-module input series output parallel (ISOP) auxiliary power supply topology is proposed, which integrates the DC110V charger and the front LLC converter. Firstly, an IGBT switch circuit driving two LLC resonators is realized as a DC transformer (DCX) by reasonable LLC parameter design. As the switching circuit of the charger is cancelled, and the charger does not need two-stage conversion, the product efficiency is greatly improved. Secondly, an ISOP auxiliary power supply scheme based on Boost+LLC is adopted, and the natural input-voltage sharing (IVS) and the natural output-current sharing (OCS) can be realized, without complex voltage and current sharing control algorithms. Finally, a 180 kVA auxiliary power supply platform is built to verify the feasibility of the proposed integrated circuit topology and control algorithm.