A circuit for controlling a switch in a power converter in which peak current is regulated to achieve a specified average current through a load. The circuit can include a first input to receive a voltage corresponding to a pre-specified target average current through the load, and a second input to receive a voltage corresponding to a voltage across a sensing resistor immediately after the switch turns ON. The circuit generates a threshold value that is approximately equal to twice the voltage corresponding to the pre-specified target average current through the load, minus the voltage corresponding to a non-zero voltage across the sensing resistor just after the switch turns ON. Control logic is operable to monitor a voltage across the sensing resistor such that when the voltage across the sensing resistor reaches or exceeds the threshold value, the control logic generates a signal that causes the switch to be turned OFF.