Patent ID: 8866460

Claim:
A power supply comprising: a power converter operative to convert an input voltage into a regulated voltage by referencing to a first DC voltage; a low dropout (LDO) regulator including an output transistor having an input terminal receiving the regulated voltage, a control terminal receiving a control voltage, and an output terminal sourcing an output voltage, and an LDO controller generating the control voltage by referencing to a second DC voltage, and modulating the control voltage responsive to an AC tone signal; and a reference voltage generator connected to the power converter and the LDO regulator, configured to adjust the first DC voltage according to the regulated voltage and the control voltage, wherein the reference voltage generator comprises: a detector connected to the input terminal and the control terminal of the output transistor, configured to compare a difference between the regulated voltage and the control voltage to a first threshold and a second threshold, respectively, to determine a detection signal; and a dynamic dropout controller connected to the detector, responsive to the detection signal to adjust the first DC voltage.