Patent ID: 8890493

Claim:
A voltage regulator circuit comprising: a linear voltage regulator having a pass transistor and a first feedback configured to feedback from an output load to a control terminal of the pass transistor, wherein the pass transistor includes an input terminal, which is configured to be connected to an input voltage, and an output terminal; a switching regulator configured to operate temporally simultaneously with the linear voltage regulator and having: a second feedback from a voltage drop across the pass transistor; a high-side switch and a low-side switch, wherein the high-side switch is coupled between the output terminal of the pass transistor and the low-side switch, and the low-side switch is coupled between the high-side switch and ground, a mid-node of the high-side switch and the low-side switch is coupled to a circuit output; a digital duty cycle controller connected to the high-side switch and low-side switch and configured to control a duty cycle of the high-side switch and low-side switch based on the voltage drop; and an efficiency monitor coupled to the second feedback and configured to detect the voltage drop and control predetermined steps of the duty cycle of the switching regulator based on the voltage drop.