High power density and high efficiency SMPS for adaptor applications


The adaptors are widely used in commercial electronic devices, such as mobile phones, laptops, etc.

Nowadays, the adaptors are developing toward higher power density and high efficiency, especially with the application of wide bandgap semiconductors, such as the GaN MOSFETs.

However, the volume of the adaptors are still very large and the reduction of the volume is very attractive. Furthermore, the wide-input range of the adaptors makes it less efficient when the input is either too low or too high. Therefore, both the volume and the efficiency need further improvement.Recently, GaN devices are increasing popular in power converters, mainly because of its faster switching speed and lower switching loss compared with the Silicon devices. With the GaN devices it is possible to push the switching frequency to the MHz range while keeping high efficiency.


This project aims at designing a high power density and high efficiency SMPS for adaptor applications.

In order to achieve high efficiency over the wide-input range, a new topology with variable gain is proposed. In this way the wide-input range is divided into several sections and each section can be optimized to maximize the efficiency.

The efficiency at the low input voltage and the high input voltage will be improved as well.

Besides, in order to reduce the volume, the switching frequency is pushed to 2.5 MHz.

In order to operate at high switching frequency, the switches must operate at soft switching conditions.

In this case the active clamp circuit is utilized to achieve soft switching.


The adaptor is expected to be improved with higher efficiency and lower volume.

Furthermore, it is expected that the topology in this project may provide a general solution to wide-input range problems, which means the topology in this project can be custom designed to solve other wide-input range applications.

Completed: 2018.