Analysis and design of a power converter for high-power density adapters.

The growing demand to reduce the size of chargers/adapters for mobile electronic devices such as laptops, tablets, smartphones, etc., motivates the increasing interest in the research for the development of high power-density adapters. Another important need of today’s society is to minimize the waste of energy. To guarantee this request, high efficiency adapters must be designed. The most used circuit topology for this type of application is the conventional flyback power converter. It has been widely used for low power application due to its simple design, as it requires few components, low cost, and insulation feature. However, in this topology, switches operate in hard-switching mode resulting in increased switching losses and high electromagnetic interference (EMI) noise. In this case, snubbers are needed to protect primary and secondary switches from voltage spikes and to reduce the EMI noise. To overcome these problems, three main solutions have been presented in literature: Active Clamp Flyback converter, Asymmetrical Half Bridge Flyback converter and LLC resonant power converter. All these circuit topologies can work under soft-switching mode making snubbers no more needed. Moreover, the dimensions of the electronic parts present in the power converters can be reduced by operating them at high switching frequency to reduce the size of the transformer, the volume of the capacitors and the size of the switches. To operate the converters at high switching frequency (i.e., larger than MHz), Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) devices are adopted because they are more suitable for these applications than Silicon MOSFETs and this help to improve the power-density as well as the performance of power converters.