| 摘要 |
PROBLEM TO BE SOLVED: To reduce a power loss and to surely switch from a second power source to a first power source without using a step-down circuit that is large-scaled in area and cost, even if a voltage of the second power source of which the voltage precision is deteriorated unexpectedly exceeds a voltage of the first power source, in a power source switching circuit for switching the first power source and the second power source.SOLUTION: A power source switching circuit A for switching a first power source 11 of high voltage and a second power source 12 of low voltage includes: a transfer contact 15b for switching input terminals 21 and 22 from the power sources with respect to an output terminal 24; a voltage discrimination circuit 14 for driving a relay when the voltage of the first power source exceeds a specific value; and a mechanical relay 15 for switching the transfer contact 15b from the second power source side to the first power source side in accordance with an instruction from the voltage discrimination circuit 14. It is better to provide a series regulator 16 for bypass connection of the transfer contact 15b between an input terminal and an output terminal at the second power source side.SELECTED DRAWING: Figure 1 |
