On-board charge (OBC) is one of the key components in new energy vehicles. The auxiliary power supply is used to provide stable power to gate drivers, voltage and current sampling, MCU, and so forth. This document first introduces the two main architectures commonly used for OBC auxiliary power supplies. Based on the power requirements of the auxiliary power supply of the mainstream 11KW OBC on the market, using a low-voltage 12V battery as the input of the auxiliary power supply. Low-cost, high-performance auxiliary power solutions are introduced, and the system block diagram, system BOM cost, Pros and Cons of the solutions are analyzed in detail.