Patent ID: 6979915
Filing Date: 2005-12-27
Classification: H02J

Abstract:
1. A portable equipment including a backup battery charging circuit, said circuit comprising: a main battery; a regulator circuit for receiving electric power from said main battery so as to supply a charging current to a backup battery; a diode connected directly to said main battery, for preventing leakage of a current from said backup battery to said main battery; a direct charging circuit for supplying a charging current from said main battery to said backup battery without the intervention of said regulator circuit; and a charging mode determiner for determining an appropriate charging mode from the group consisting of a first charging mode, where the charging current is supplied through said regulator circuit to said backup battery, and a second charging mode, where the charging current is supplied from said main battery to said backup battery without the intervention of said regulator circuit, so as to charge said backup battery, wherein: said charging mode determiner compares the output voltage of said regulator circuit with the voltage of said backup battery, selects said first charging mode when the voltage of said backup battery is lower than or equal to the output voltage of said regulator circuit and selects said second charging mode when the voltage of said backup battery exceeds the output voltage of said regulator circuit.