A charger control circuit (CC) comprises a first charger terminal (CT1) and a system terminal (ST) and is configured to assign a voltage applied at the first charger terminal (CT1) to one of at least three voltage ranges by performing at least one voltage comparison. The charger control circuit (CC) is configured to determine and distinguish, based on the assignment, whether an external charger (EXC1) or a secondary battery (SBAT) is connected to the first charger terminal (CT1). Furthermore, the charger control circuit (CC) is configured to, depending on a predetermined operating state of the first charger terminal (CT1), supply power from the secondary battery (SBAT) or the external charger (EXC1) to a portable electronic device via the system terminal (ST) when the secondary battery (SBAT) or the external charger, respectively, is connected to the first charger terminal (CT1).