Patent ID: 7262585

Claim:
A power supply system comprises: a transistor having an input, a substrate, a first node, and a second node, the first node operably coupled to a non-battery power source; a linear regulator operably coupled to the second node to produce a regulated output voltage based on the non-battery power source, when enabled; a DC-DC converter operably coupled to produce the regulated output voltage based on a battery power source, when enabled; and a control circuit operably coupled to the input node and the substrate of the transistor wherein when the DC-DC converter is enabled, the control circuit controls a reverse leakage current of the transistor, and when the linear regulator is enabled in a zero load-state, the control circuit controls a forward leakage current of the transistor, and when the linear regulator is enabled in a non-zero load-state, the control circuit provides a current limit for the linear regulator.