Rechargeable battery charging circuit

DETAILED DESCRIPTION Accordingly, it is therefore an object of the present invention to provide a novel battery charging circuit of a battery pack capable of charging a rechargeable battery quickly with high charging efficiency.
It is also an object to provide a battery charging circuit of a battery pack having an ambient temperature detector responsive to the ambient temperature for controlling charging current to insure a fully charged rechargeable battery.
It is another object to provide a battery charging circuit of a battery pack usable for portable computers to fully charge a rechargeable battery with a succession of charge current in a staircase wave form in response to ambient temperature variations.
These and other objects of the present invention can be achieved by a battery charging circuit of a battery pack which comprises a battery switch connected between a regulated source of DC voltage and the battery; a current detection circuit for detecting intensity of charging current flowing from the DC voltage source through the battery switch to the battery and generating a charging current detection signal exhibiting a magnitude varying substantially linearly with the intensity of the charging current.
A first controller having an input terminal enabled by a first control logic signal and a feedback terminal coupled to receive the charging current detection signal, is provided to control operation of the battery switch in accordance with a voltage level at the feedback terminal.
A second controller having an input terminal enabled by a second control logic signal, is provided to control operation of the battery switch by varying the voltage level at the feedback terminal in accordance with the second control logic signal.
A battery detection circuit is provided to detect a temperature of the battery and generate a battery temperature signal having a magnitude varying substantially linearly with the battery temperature.
A third controller is provided to generate the first and second control logic signals in dependence upon the magnitude of the battery temperature signal