Patent ID: 8222869

Claim:
A charging circuit for charging a battery, comprising: a pulse generator for generating a plurality of pulses to control an N-channel metal-oxide-semiconductor field-effect transistor (NMOSFET); a controller coupled to said pulse generator for controlling a pulse density of said plurality of pulses according to a status of said battery; a charge pump coupled to said pulse generator for receiving said plurality of pulses and for generating a driving signal; and a resistor coupled to a gate of said NMOSFET, wherein said resistor and a capacitance of said gate of said NMOSFET form a low pass filter, wherein said driving signal is filtered by said low pass filter to control a gate voltage of said NMOSFET, wherein a variation of a gate-source voltage of said NMOSFET is proportional to said pulse density, and wherein a variation of a charging current flowing through said NMOSFET to said battery is proportional to said pulse density.