Battery charger where the charge current rate is set by a switch modulated with a variable duty cycle

DETAILED DESCRIPTION To address the above-discussed deficiencies of the prior art, the present invention provides, for use in a battery-powered electronic device, a battery charging circuit, a method of charging a battery and a battery-powered electronic device employing the circuit or the method.
In one embodiment, the battery charging circuit includes a charging switch, coupled between a base interface of the battery-powered electronic device and a battery thereof to be charged.
When closed, the charging switch provides a conductive path for charge current from the base interface to the battery.
The charge current is based on an input voltage of the battery charging circuit and a voltage of the battery.
The battery charging circuit further includes a controller that modulates the charging switch at a duty cycle that at least in part determines a rate at which the charge current is delivered to the battery thereby to compensate at least in part for variations in the input voltage.
The present invention introduces, in one aspect, the concept of providing a battery charging circuit that employs a charging switch associated with a battery-powered electronic device to charge the battery in a more accurate manner.
The battery charging circuit is sensitive to both its input voltage and the actual voltage of the battery.
This allows the battery charging circuit to apply an appropriate charge current that will charge the battery in an effective manner while limiting the possibility of battery damage due to overcharging.
This strategy provides a minimal charging time while protecting the battery.
Additionally, the present invention can advantageously employ portions of a controller that are already in place to control the electronic device.
In one embodiment of the present invention, the battery charging circuit further includes a trickle charge resistor, coupled in parallel with the charging switch, that provides a trickle charging conductive path for a trickle charging current.
The trickle charging current represents a minimum value of charge current for the battery