Abstract: A circuit (100) is provided that is connectable between input lines (150, 152, 154) and output lines (160, 162). The circuit is comprised of a primary battery (103) and a hold-up battery (101). The hold-up battery is connected in parallel with the primary battery. The circuit is further comprised of an RC circuit (180) connected in parallel with the primary battery and is isolated from the hold-up battery by unidirectional current valves (108, 110). A comparator is provided with a first input (130) coupled to the RC circuit and a second input (132) coupled to a voltage reference. A switching device (104) is provided that is controlled by an output of the comparator. The switching device connects the hold-up battery to output lines in a first state and disconnects the hold-up battery from output lines in a second state. The unidirectional current valves prevent reverse leakage current from the hold-up battery from charging a capacitor during a discharge period of the RC circuit.

Abstract: A circuit (100) is provided that is connectable between input lines (150, 152, 154) and output lines (160, 162). The circuit is comprised of a primary battery (103) and a hold-up battery (101). The hold-up battery is connected in parallel with the primary battery. The circuit is further comprised of an RC circuit (180) connected in parallel with the primary battery and is isolated from the hold-up battery by unidirectional current valves (108, 110). A comparator is provided with a first input (130) coupled to the RC circuit and a second input (132) coupled to a voltage reference. A switching device (104) is provided that is controlled by an output of the comparator. The switching device connects the hold-up battery to output lines in a first state and disconnects the hold-up battery from output lines in a second state. The unidirectional current valves prevent reverse leakage current from the hold-up battery from charging a capacitor during a discharge period of the RC circuit.