Power supply device

A power supply device comprising:

• n configuration stages, n being an integer equal to or greater than 2, each configuration stage including:
• a unit including one or more power storage devices;
• a step-down switch having a drain-side terminal connected to a positive electrode of the unit;
• and a step-up switch having a drain-side terminal connected to a source-side terminal of the step-down switch;
• a voltage measurement device to measure voltage of each unit;
• a power storage mechanism to store electric energy and capable of receiving and outputting power;
• a reactor connected in series to the power storage mechanism;
• and
• a control operation section to switch each of the step-down switch and the step-up switch between a conductive state and a non-conductive state, wherein
• the positive electrode of the unit in an m-th configuration stage of the configuration stages is connected to a negative electrode of the unit in an (m−1)-th configuration stage of the configuration stages, m being an integer satisfying 2≤m≤n,
• the drain-side terminal of the step-up switch included in the m-th configuration stage is connected to a source-side terminal of the step-up switch included in the (m−1)-th configuration stage,
• a source-side terminal of the step-up switch included in an n-th configuration stage of the configuration stages is connected to a negative electrode of the unit included in the n-th configuration stage,
• the n step-up switches connected in series are connected in parallel to a series circuit including the power storage mechanism and the reactor, and
• the control operation section refers to the voltage of each unit measured by the voltage measurement device, and when any of the units has such voltage that an absolute value of a difference from an average value of the voltages of the plurality of units is greater than a reference value, the control operation section performs control so as to reduce the difference.