Patent ID: 7602082
Filing Date: 2009-10-13
Classification: H02J

Abstract:
1. A power supply apparatus employing a backup battery configured to supply a load with a voltage in place of a main battery when a voltage of the main battery decreases to a prescribed level, said power supply apparatus comprising: a first terminal connected to the main battery; a second terminal connected to the backup battery; a diode having an anode connected to the first terminal and a cathode connected to the second terminal, wherein the diode is configured to output the voltage of the main battery to the load through the second terminal; a switch circuit configured to short the diode; a voltage monitor circuit configured to monitor and determine if the main battery voltage decreases to a prescribed level; a voltage comparison circuit configured to compare the main battery voltage with the backup battery voltage; and a circuit responsive to the voltage monitor circuit and the voltage comparison circuit for controlling the switch circuit such that: