1. An apparatus, comprising:a voltage regulator configured to generate an output voltage for supplying a lighting controller;
a current power train comprising a power FET and coupled to the voltage regulator;
a gate drive circuit coupled to a gate of the power FET;
a logic circuit coupled to the gate drive circuit and configured to operate the power FET as a switching-mode power supply; and
a comparator coupled to the logic circuit, wherein the comparator is configured to provide a signal to the logic circuit proportional to a difference between an auxiliary output node voltage and a reference voltage.