| 摘要 |
PURPOSE: To reliably switch a main power supply and a sub-power supply by preventing error operation of a PMOS transistor for supplying the main power supply to a load. CONSTITUTION: A PMOS transistor 3 is for supplying a main power supply 1 to a load 7. A high potential power supply and a low potential power supply are supplied as operation power supplies to a control circuit 4, and the PMOS transistor 3 is turned on and off by outputting a second control signal S2 of a voltage of the high potential power supply and the low potential power supply based on a first control signal S1. A comparing circuit 5 compares a voltage Vm of a main power supply 1 with a voltage Vs of a sub power supply 2. A selection circuit 6 selects a power supply having a higher voltage value as a high potential power supply for supplying to the control circuit 4, and the power supply selected is supplied to the control circuit 4 while maintaining its voltage. |
