Patent ID: 8569996

Claim:
A portable apparatus comprising: a system configured to receive a system current and perform a function; a charging battery configured to be charged with a charging battery current and supply power to the system; and a power management circuit configured to receive an externally supplied power, supply the system current to the system, and supply the charging battery current to the charging battery based on a sensed level of the system current, wherein the charging battery current decreases in proportion to the system current, and wherein the power management circuit comprises a first current mirror unit configured to output a proportional current used to determine the sensed level, wherein the power management circuit further comprises: a system power supply configured to directly receive the externally supplied power, supply the system current to the system, and output a proportional current that increases in proportion to the system current; a charging battery power supply configured to directly receive the externally supplied power and supply the charging battery current to the charging battery, wherein the charging battery current decreases in proportion to the proportional current; an input terminal to which the externally supplied power is applied; a system output terminal connected to the system and through which the system current is output; a sensing terminal connected to a sensing resistor and through which the proportional current is output; and a charging battery output terminal connected to the charging battery and through which the charging battery current is output, wherein the system power supply comprises: a first controller configured to maintain a voltage of the system output terminal at a first voltage level in response to a reference voltage and output a first signal in response to the reference voltage and the voltage of the system output terminal; and wherein the first current mirror unit is directly connected to the input terminal, and is configured to supply the system current through the system output terminal to the system in response to the first signal and output the proportional current to the sensing terminal.