A power system includes one or more notification circuits for powering notification devices, a backup power source, and a plurality of primary power supplies. The primary power supplies are configured to provide a combined current to the notification circuits. Each primary power supply regulates its output current to equal a highest output current provided by one of the primary power supplies so that each contributes approximately the same current to the load. The primary power supplies also include boost regulator circuits for boosting the voltage of the backup power supply.