The benefits of closed loop control with secondary sensing can be seen in the performance charts shown on this slide, which compare iCoupler  isolated switching regulators to primary-side sensing flyback regulators. In the upper left corner, load regulation for output currents from 50mA to 500mA is shown. The output voltage of the iCoupler device is nearly unchanged, whereas the primary-side flyback controller experiences a 50mV change in the regulated voltage. Temperature performance, shown in the upper right chart, is also better for the iCoupler device. The iCoupler solution maintains better than 70% efficiency over most of its specified load range, and is particularly efficient under light load conditions, as seen in the bottom chart. This is due to the use of MOSFET switches as the transformer drivers.