| 摘要 |
PURPOSE:To apply a constant voltage to a load circuit by detecting voltage generated by the first or second power supply circuit, and controlling the operation of a switching circuit. CONSTITUTION:When an electronic equipment body is in a normal operation mode, the output voltage VB2 of the second power supply circuit 4 is detected by a voltage detector circuit 5, keeps a selector switch 6 in the opened state, and applies the output voltage VB2 of the second power supply circuit 4 to the lead circuit 2 of a microcomputer, etc. When the electronic equipment body is in a standby operation mode, the voltage detector circuit 5 detects low-level output voltage VB2 of the second power supply circuit 4, changes the selector switch 6 over to the closed state, and applies the output voltage VB1 of the first power supply circuit 3 to the load circuit 2 of a microcomputer, etc. This makes it possible to switch over power sources so as to make the output voltage constant automatically, and a voltage switching circuit of simple constitution can be provided. |
