Patent ID: 7629709

Claim:
A method for regulating a second DC to DC converter of a battery powered portable electronic device comprising a first DC to DC converter and a second DC to DC converter to provide a substantially constant internal supply voltage, wherein the first DC to DC converter is configured to provide an internal supply voltage for the battery powered portable electronic device that is derived from a non-battery power source and the second DC to DC converter is configured to provide an internal supply voltage for the battery powered portable electronic device that is derived from a battery voltage, the method comprises: sensing deactivation of the first DC to DC converter; obtaining an initial regulation value for an initial duty cycle of the second DC to DC converter, wherein the initial regulation value is based on the battery voltage and the internal supply voltage; and enabling the second DC to DC converter with the initial duty cycle based on the initial regulation value, wherein the second DC to DC converter converts the battery voltage into the internal supply voltage such that transitioning from the non-battery power source to a battery power source provides the substantially constant internal supply voltage.