Increasing power density of adapters by using DC link chopper

Flyback switch-mode power supplies (SMPS) are popular for low-power and medium-power external power adapters due to their light weight and low cost. While the demand for more compact adapters for notebooks, tablets and gadgets is continuously increasing, there are physical limitations in the efficiency and power density that can be achieved using the Flyback topology. One major issue is the DC link capacitor, also known as bulk cap; its volume represents a big part of the adapter, its power dissipation is a major loss and its life expectation is the main factor in the reliability of the adapters. This paper introduces an innovative solution for reducing the value, the volume and the power losses of the bulk capacitor; as an extra benefit of this solution, the power factor of the adapter is also improved and the conduction losses associated with the front end of the converter are significantly reduced.