Patent ID: 7923858

Claim:
An electric power source system comprising: a first voltage conversion device that selectively switches between voltage conversion in a first direction from a first voltage system to a second voltage system, and voltage conversion in a second direction from the second voltage system to the first voltage system; and a second voltage conversion device, connected in parallel with the first voltage conversion device, that converts voltage in the second direction; wherein a direction of current flowing via the first voltage conversion device switches from the first direction to the second direction after current begins flowing in the second direction via the second voltage conversion device; wherein the electric power source system further comprises a circuit in which the current begins to flow in the second direction via the second voltage conversion device, when a voltage on the first voltage system is below a target output voltage of the second voltage conversion device, which is set to be lower than a voltage of an electric power source contained in the first voltage system; and wherein a load connected to a first power source line of the first voltage system is connected to an output terminal of the circuit via a second power source line which is different from the first power source line.