Dr. Lee is a University Distinguished Professor at Virginia Tech and the Founder and Director of the NSF ERC – Center for Power Electronics Systems (CPES). He is a member of the U.S. National Academy of Engineering, an academician of Taiwan’s Academia Sinica, and a foreign member of the Chinese Academy of Engineering, China. As CPES Director, Dr. Lee leads a program that encompasses research, technology development, educational outreach, industry collaboration, and technology transfer. To date, more than 215 companies worldwide have benefited from this industry partnership program.
Dr. Lee has supervised to completion 84 Ph.D. and 93 M.S. students. He holds 82 US patents, and has published over 296 journal articles and more than 722 refereed technical papers. His research interests include high-frequency power conversion, magnetics and EMI, distributed power systems, renewable energy, power quality, high-density electronics packaging and integration, and modeling and control.
Dr. Lee is a recipient of the 2015 IEEE Medal in Power Engineering “for contributions to power electronics, especially high-frequency power conversion.”
Converging Power Supplies for LEDs, IT & Consumer Electronics with Integrated Magnetics
In today’s power electronics products, quality and reliability are given, Great emphases are placed on high efficiency, high power density and low cost. With recent advances made in wide-band-gap (WBG) power devices, I believe the new generation of switches will make significant impacts to all three areas mentioned above. It is evident that GaN switches are capable of operating at 10X or 20X higher switching frequency, comparing to their silicon counterparts. What has been taken for granted in our design practice is being challenged. Certain design trade off previously inconceivable can be realized with not only significant performance enhancement but also drastic reduction of the labor contents in the manufacturing and assembly process.
To illustrate this new design paradigm, a GaN based 1KW AC/DC switching power supplies for computer server is chosen as an example with an operating frequency above 1MHz. The transformer for the DC/DC converters are broken down into 4 or 8 pieces and then integrated into a matrix transformer structure with all windings embedded in a simple 6-layer PCB. This proto-type is able to achieve an efficiency greater than 97% and power density of 900W/in3, and with much reduced CM noises. Similar performance improvements can be realized with the PFC converter operating above 1MHz. Furthermore, the entire power supplies, with the exception of the filter inductor, can be manufactured in automation.
This new design and manufacturing paradigm is not unique for the chosen application. Similar conclusion can be drawn with other applications such as wall adapters, on-board chargers, consumer electronics and LED lightings.
Figure: Conventional 100KHz, 1KW design v.s. 1MHz design