Patent ID: 8283898

Claim:
A battery charging circuit, comprising: an output transistor that supplies a battery with charging current; a control transistor including a control terminal connected to a control terminal of the output transistor and a current input terminal connected to a current input terminal of the output transistor; a first switch circuit that switches connection of the current output terminal of the control transistor between a first terminal and a second terminal, the first terminal being connected to a first resistor that determines charging current in a trickle charge mode, and the second terminal being connected to a second resistor that determines charging current in a fast charge mode; a second switch circuit that selectively outputs voltage from the first terminal and the second terminal; a third switch circuit that lowers a current restriction reference voltage before the trickle charge mode is switched to the fast charge mode and returns the current restriction reference voltage to its original value after switching the modes; a first error amplifier that compares an output of the second switch circuit and an output of the third switch circuit; and a current amount determination unit that determines a gate voltage of the output transistor based on an output of the first error amplifier.