US Patent 8981673 Power supply that maintains auxiliary bias within target range

A power supply includes a switch configured to control flow of current output from an inductor to an output of the power supply. The switch receives a switching signal from a control circuit. An auxiliary bias is generated to power the control circuit. A bias circuit outputs a bias signal that is used to generate the auxiliary bias. The bias circuit senses a level of the auxiliary bias to control output of the bias signal. Output of the bias signal may be controlled to maintain the level of the auxiliary bias at a target level or within a target range.