A power supply switching circuit 100 according to the present invention is a power supply switching circuit for switching between a first power supply and a second power supply, at least one of which is a battery power supply, and connecting it to a load, the first power supply and the second power supply. Provided between the first power supply connection portion and the second power supply connection portion configured to be connectable to each other, a load connection portion configured to be capable of connecting a load, and each power supply connection portion and the load connection portion. The first switch unit and the second switch unit, and a switching control unit that performs switch control of each switch unit. Each switch unit has a plurality of FETs connected in series in the same direction so that the cathode side of the body diode is on the load connection side. The number exceeds the difference between the full charge voltage and the discharge voltage of the battery power supply. The power supply switching circuit of the present invention realizes power supply switching with high reliability.本発明の電源切換回路１００は、少なくとも一方がバッテリー電源である第１の電源及び第２の電源を切り換えて負荷に接続するための電源切換回路であって、第１の電源及び第２の電源の接続が可能に構成される第１の電源接続部及び第２の電源接続部と、負荷の接続が可能に構成される負荷接続部と、各電源接続部と負荷接続部との間に設けられる第１のスイッチ部及び第２のスイッチ部と、各スイッチ部のスイッチ制御を行う切換制御部とを含む。各スイッチ部は、ボディーダイオードのカソード側が負荷接続部側となるように同一方向に直列に接続される複数のＦＥＴを有し、その個数は、各ＦＥＴのボディーダイオードの順方向降下電圧の総和がバッテリー電源の満充電電圧と放電電圧との差を超える個数である。 本発明の電源切換回路は、高い信頼性で電源の切り換えを実現する。
