An off-line power supply receives power from an alternating-current (AC) source and provides a voltage-regulated, direct-current (DC) output that can be used to power a load. An exemplary off-line power supply includes a power factor correction (PFC) stage and a DC-to-DC converter stage. The PFC stage receives the AC input signal, performs rectification and maintains current drawn from the AC source substantially in phase with the AC voltage so that the power supply appears as a resistive load to the AC source. The DC-to-DC converter stage receives the rectified output of the PFC stage and generates the voltage-regulated DC output which can be used to power the load. The rectified output of the PFC stage is typically at higher voltage and is more loosely regulated than the output of the DC-to-DC stage.
Under certain conditions, a load that receives power from the power supply may present abnormally low impedance. If left unchecked, this condition could result in an excessively high level of output current.
It is desired to provide an improved power supply. It is also desired to provide an improved system and method for limiting output current in a switching power supply.