US Patent 9018921 Battery charger architecture

A control circuit for use in a battery charger circuit that includes a switching voltage regulator, with the control circuit having a constant current charging mode and a constant voltage charging mode. A switcher controller is provided which configured to control a state of a top side switching transistor and a low side transistor of the switching voltage regulator in response to at least one error signal. A power path transistor switch is disposed intermediate an output of the switching voltage regulator and a first node for receiving a first terminal of a battery to be charged. Feedback circuitry is further provided to produce a first error signal relating to a difference between a first voltage and a first target voltage, with the first voltage being between the output of the switching voltage regulator and a second node for receiving a second terminal of the battery to be charged, with the first error signal being used by the switcher controller when the control circuit is in the constant voltage charging mode for controlling the top and low side switching transistors.