| 摘要 |
PROBLEM TO BE SOLVED: To obtain a power source switch circuit which alternately switches a plurality of power sources having different power source voltages and can supply power to loads, by applying larger one out of power source voltages applied to a first and a second battery connecting ends to back gates of a first and a second power transistors. SOLUTION: A power source switch circuit alternately outputs power source voltages applied to a first and a second battery connecting ends 10A, 10B from an output end 50. A first power transistor QP1 is turned into the state of ON corresponding to a first switch control signal and introduces the power source voltage applied to the first battery connecting end 10A to an output end G. A second power transistor QP2 is turned into the state of ON corresponding to a second switch control signal and introduces the power source voltage applied to the second battery connecting end 10A to the output end G. Larger one out of the power source voltages applied to the first and the second battery connecting ends 10A, 10B is applied to back gates of the power transistors, so that a current does not flow in a parasitic diode. |
