Power source system

A power source system for use in a vehicle that includes an electric motor, the power source system comprising:

• a power source device;
• and
• a control device that controls the power source device, wherein:
• the power source device includes
• a main power source,
• an auxiliary power source, and
• a switching circuit configured to switch a power supply mode between a first power supply mode, in which power is supplied to a drive circuit for the electric motor by only the main power source, and a second power supply mode, in which power is supplied to the drive circuit utilizing both the main power source and the auxiliary power source;
• and
• the control device includes
• a switching circuit control unit that controls the switching circuit on the basis of a value that matches power consumption by the drive circuit,
• a determination unit that determines whether an operation state of the electric motor is a regeneration state or a power-running state, and
• a limitation unit that limits power to be supplied to the drive circuit when the power supply mode is the second power supply mode and it is determined by the determination unit that the operation state of the electric motor is the regeneration state.