US 6,472,849 B1 · Reverse blocking function integrated into charging circuit

Abstract

An apparatus and method is provided that blocks reverse currents. A PMOS device prevents reverse currents from draining the battery. The PMOS device is activated when a light load is detected on the cell. The light load detected may occur when the device is connected to the charger but the charger remains disconnected from a power source. A sense circuit is used to determine the voltage across a switch circuit. The reverse blocking function is activated when the cell voltage is a few millivolts above the charging signal. The reverse blocking function apparatus removes an external component from a conventional charger and integrates the function of the component onto the battery charging IC. The apparatus uses a lower compliance “on” voltage as compared to a conventional battery charger circuit that is intended to block reverse currents. The reverse blocking function apparatus integrated onto the battery charging IC requires less operating headroom as compared to a Schottky diode.

Claims17

Dependent claims

An apparatus for a battery charging integrated circuit (IC) that blocks reverse currents from draining a battery, comprising:

a switch circuit that includes a first input that is coupled to a power signal, a second input that is coupled to a feedback signal, and an output that is arranged to provide a charging signal;
a sense circuit that includes an input that is coupled to the power signal and an output that is arranged to output a sense signal relating to the charging signal through the switch circuit;
a reverse blocking circuit integrated onto IC that includes a first input that is coupled to charging signal, a second input that is arranged to receive a blocking signal indicating when to activate and deactivate the reverse blocking circuit, and an output that is arranged to couple the charging signal in response to the blocking signal;
a charge circuit that includes an input that is coupled to charging signal, a first output that is coupled to the second input of the switch circuit and that is arranged to provide the feedback signal, and a second output that is arranged to couple the charging signal to the battery;
and
a charger detect circuit that includes a first input that is coupled to a cell signal relating to a current charge level of the battery, a second input that is coupled to the sense signal, and an output arranged to provide the blocking signal.

3 more elements

Dependencies are inferred from the claim text.

Reverse blocking function integrated into charging circuit

Life of this patent

Reverse blocking function integrated into charging circuit

Life of this patent

Abstract

Claims17