Vehicle power supply system and method for controlling vehicle power supply system

The invention relates to a vehicle power supply system and a control method of the vehicle power supply system. A vehicle power supply system includes a power supply control device (88) that performs a process of switching a connection state of a drive circuit (61a) with a main power supply (45) and an auxiliary power supply (81), the process including: a process of switching the connection state so as to transition to a standby state due to a voltage drop of the main power supply (45); and a process of switching the connection state so as to transition to a normal state because the voltage drop of the main power supply (45) is resolved. After a voltage drop of a main power source (45) occurs, a rotation-side control device (60) of a steering control unit (1) sets an output-limited state for a rotation-side motor (32). When the power supply control device (88) completes the switching of the connection state for transition, the output limited state is cancelled. 本发明涉及车辆电源系统以及车辆电源系统的控制方法。车辆电源系统包括电源控制装置(88)，该电源控