A shunt regulator for use in a power converter having an energy transfer element for regulating a transfer energy of the output signal delivered to the load. An auxiliary winding of the energy transfer element being utilized to produce an internal bypass voltage, VBP, at a bypass pin coupled to an external capacitive load, the shunt regulator including a two-mode operational amplifier that produces an output signal that controls a shunt current through the shunt switch. At power-up, or at low load conditions, the operational amplifier operates in a low-power mode of operation with low quiescent current. When a current comparator circuit senses that the shunt current exceeds a predetermined level, the current comparator circuit sets a latch which produces a logical signal that causes the operational amplifier to switch to a high-power mode of operation.