Patent ID: 7375491

Claim:
A charge circuit for charging at least one battery comprising: a first current generating circuit for generating a first charge power having a first charge current in pulse form with a first frequency and a first charge voltage to charge the at least one battery, wherein the first charge current in the first charge stage remains substantially constant, and the first charge voltage remains a first constant voltage; a voltage generating circuit connected to the first current generating circuit for controlling the first charge power; a voltage control circuit connected to the voltage generating circuit for generating a first constant voltage or a second constant voltage; and a second current generating circuit connected to the voltage generating circuit for generating a variant power comprising a variant current in pulse form with a second frequency, wherein a charge voltage included in the variant power varies with the second frequency, wherein the voltage control circuit comprises: a second transistor and a third transistor; an eleventh resistor and a twelfth resistor connected in series; a thirteenth resistor having a terminal that is connected to the second transistor; a fourteenth resistor connected to the third transistor; a fifteenth resistor is connected to the second transistor; and a sixteenth resistor is connected to the second transistor; wherein when the third transistor turns on, the first constant voltage is generated, and when the third transistor turns off, the second constant voltage is generated.