Battery charging circuit
AssigneeFreescale Semiconductor, Inc.
InventorMasami Aiura
Life of this patent
Estimating the term…
Abstract
A battery charging circuit that stabilizes operation when switching between charge modes includes first and second transistors. The first transistor has a source connected to a first switch circuit. The first switch circuit connects the second transistor to either one of first and second external terminals. A mode switch circuit generates a switch signal for switching from a trickle charge mode to a fast charge mode. The mode switching circuit provides the switching signal to a comparison circuit. After a predetermined time elapses, the mode switching circuit provides the switching signal to the switch circuit. The comparison circuit lowers a current restriction reference voltage, which determines a charging current value, and returns the current restriction reference voltage to its original value after switching modes.
Claims5
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.
Dependencies are inferred from the claim text.