In June 5, 2018, Professor Dong Cao of North Dakota State University was invited by the IAS Wuhan Section to make a speech about "High density and High conversion ratio resonant switching capacitor converter applied to the data center". Quite a number of professors, doctor students and graduate students attended the meeting and had enthusiastic discussion and communication with the three engineers throughout the whole forum.

Firstly, the development process of resonant converter with high conversion ratio and the design of conventional switched capacitor converters are reviewed. In order to meet the high efficiency, high power density, high conversion ratio and low-cost demand of the future 48 V Data Center DC transmission system structure, a new topology of the transformer based on broadband band gap devices (GaN high frequency operation) has been proposed. Although GaN has relatively low power consumption because of the properties of materials and soft switching, the core loss and copper loss of the transformer will increase with the increase of switching frequency, which has become a bottleneck restricting of the efficiency and the increase of power density. More importantly, the topology based on the transformer also has problems about manufacturability and scalability ,  which needs to be optimized ,designed and verificated.. It is difficult to meet the fast pace of the new CPU release of new power requirements. Therefore, the output of DC power in the future 48V data center needs modular, scalable and non-transformer high conversion ratio solution.

The report presents a new solution for future 48V data center power supply, high conversion ratio, no resonant switching capacitor DC to DC converter. It has the characteristics of modularity, scalability, high efficiency and high power density. The report also introduces the latest development of a converter for the 48V bus application of the Google data center, discussing some solutions about the large-scale production problems.

Professor Dong Cao, got his bachelor's degree at Zhejiang University in 2005 and got a master's and PhD degree in electrical engineering at the Michigan State University in Eastern Lansing during 2010-2012 years. He worked as a core engineer of power electronics at Ford motor company and he was in charge of the hardware development of the electric drive system of hybrid electric vehicles from 2012 to 2014. In August 2014 he joined North Dakota State University as an assistant professor.

Professor Dong Cao lead / CO lead a lot of projects from different government agencies or companies, including NASA, NSF, North Dakota Department of Commerce, Google, Ford, John, etc. He has more than 50 articles which were published in IEEE journals and major conferences. His research direction includes resonance and soft switching technology, switched capacitor DC-DC converter, multilevel converter, wide band gap device (GaN/SiC), 48 volt to 1V data center DC-DC, high power density converter for EV application, power converter for distributed energy, monitoring and life prediction of power rate converter, and great power Smart gate drive for rate devices and Z source inverters / converters. Because of his contribution to the resonant switched capacitor DC-DC converter, he won the paper award which was awarded by the industrial power converter Commission of the IEEE Industrial Application Association from 2010 to 2011.At the same time, he won the outstanding Report Award for the APEC in 2010, and he was also an Excellent poster display winner in the 2011 IEEE energy conversion conference and the Fair (ECEE). He is also a special co-editor for the IEEE special issue.