Patent ID: 6841973

Claim:
Method of charging a rechargeable device, comprising the following steps: a) connecting the rechargeable device to a battery connection port and ground; b) feeding a current reference value to a control unit; c) feeding a voltage reference value to the control unit; d) determining a duty cycle in accordance with the current reference value and the voltage reference value fed to the control unit; e) switching, using the duty cycle, an output voltage applied to the rechargeable device between a minimum output voltage and a maximum output voltage dependent on the current reference value and the voltage reference value by means of a charging switch; and f) disconnecting the charged rechargeable device; wherein the method further comprises the following step: g) connecting an external DC source having an input voltage to an input resistor of a charging apparatus, wherein a transistor voltage drop across the charging switch is minimized in order to reduce a power dissipated by the charging switch-transistor; h) wherein the duty cycle provided by the control unit is determined by the input voltage and the charging state of the rechargeable device.