Power source selection systems

Abstract

A power source selection system can include a primary source line configured to be connected to a primary source having a primary voltage, a backup source line configured to connect to a backup source having a backup voltage, and a voltage divider and limiter connected to the primary source line to receive the primary voltage and to provide an sense signal on a sense line. The system can include a NAND gate connected to the voltage divider and limiter to receive the sense signal. The NAND gate can be configured to provide a gate signal to a gate line based on the sense signal. The system can include a switchover circuit connected to the backup source line and the gate line to receive the backup voltage and the gate signal. The switchover circuit can be configured to output the backup voltage to a switch line in a first state, and to prevent backup voltage to the switch line in a second state. The switchover circuit can be configured to switch between the first state and the second state based on the gate signal. The system can include an ORing circuit connected to the primary source line and to the switch line. The ORing circuit can be configured to select between the primary voltage and backup voltage and to output the selected voltage as the output voltage.