High Efficiency PWM Switching Mode with High Accuracy Linear Mode Li-Ion Battery Charger
A battery charger includes: a step-down switching converter connected to provide power at a predetermined average current from an input voltage V+ to an output node V OUT ; a regulating switch connected to provide power at a predetermined voltage from the input node V+ to the output node V OUT ; a mixed mode control circuit configured to charge a battery connected to the output node V OUT in a predetermined sequence that includes: a preconditioning phase where the regulating switch provides power to the battery; and a constant current phase where the switching converter delivers power to the battery.
1 . A battery charger that includes:
a step-down switching converter connected to provide power at a predetermined average current from an input voltage V+ to an output node V OUT ;
a regulating switch connected to provide power at a predetermined voltage from the input node V+ to the output node V OUT ;
a mixed mode control circuit configured to charge a battery connected to the output node V OUT in a predetermined sequence that includes:
a preconditioning phase where the regulating switch provides power to the battery; and
a constant current phase where the switching converter delivers power to the battery.
2 . A battery charger as recited in claim 1 where the predetermined sequence includes:
a first constant voltage phase where the switching converter delivers power to the battery; and
a second constant voltage phase where the regulating switch provides power to the battery.
3 . A battery charger as recited in claim 1 where the step down switching converter includes:
a high-side switch connected between an input node V+ and a node V X ;
a low-side switch connected between the node V X and ground; and
an inductor connected in series between the node V X and the output node V OUT .
4 . A battery charger as recited in claim 2 that further comprises a switch connected in parallel with the inductor to bypass the inductor when the regulating switch provides power to the battery.
5 . A battery charger as recited in claim 2 that further comprises a switch connected in parallel with the inductor to bypass the inductor when the regulating switch provides power to the battery.
6 . A method for charging a battery that includes:
activating a regulating switch during a preconditioning phase to provide power at a predetermined voltage from the input node V+ to an output node V OUT ;
activating a step-down switching converter during a constant current phase to provide power at a predetermined average current from an input voltage V+ to an output node V OUT ;
7 . A battery charger as recited in claim 1 where the predetermined sequence includes:
a first constant voltage phase where the switching converter delivers power to the battery; and
a second constant voltage phase where the regulating switch provides power to the battery.
8 . A battery charger as recited in claim 1 where the step down switching converter includes:
a high-side switch connected between an input node V+ and a node V X ;
a low-side switch connected between the node V X and ground; and
an inductor connected in series between the node V X and the output node V OUT .
9 . A battery charger as recited in claim 2 that further comprises a switch connected in parallel with the inductor to bypass the inductor when the regulating switch provides power to the battery.
10 . A battery charger as recited in claim 2 that further comprises a switch connected in parallel with the inductor to bypass the inductor when the regulating switch provides power to the battery.