US Patent 7969127 Start-up circuit for a shunt regulator

A method and circuit for controlling the start-up of a shunt regulator that uses an error amplifier for normal operation in a linear range of a target value output voltage set by a reference voltage upon circuit start-up clamps the output voltage to a first level value below the target value, next applies regenerative positive feedback independent of the error amplifier to force the output voltage through a range where adverse conditions can occur to a second level value below the target value, and then releases the positive feedback near the target value where the error amplifier assumes control of the regulation.