PhD Thesis Presentation
Novel 3D TSV Transformers for High-Voltage Gate Driver Applications

by Mr Lulu PENG

 :  29 Nov 2013 (Fri)
 :  9:30am
Venue  :  Room 3315, 3/F (Lifts 17-18), HKUST

Examination Committee
Prof Long QUAN, CSE/HKUST (Chairman)
Prof Johnny K O SIN, ECE/HKUST (Thesis Supervisor)
Prof Z. John SHEN, Department of Electrical and Computer Engineering, Illinois Institute of Technology (External Examiner)
Prof Patrick YUE, ECE/HKUST
Prof Lilong CAI, MAE/HKUST
Higher level system integration and miniaturization has become a big trend for future power electronic systems development. Doing so will have the advantages of lower cost, reduced size, smaller parasitics, and improved reliability. As a key component in high-voltage (HV) power electronic systems, a compact, high performance HV gate driver is required. In order to achieve that, monolithic transformers to provide a fully integrated solution along with HV galvanic isolation capability are needed. However, previously reported monolithic transformers either suffer from high operating frequency (at several hundreds to thousands of MHz) or have poor isolation capability. In this thesis, novel 3D TSV (Through-Silicon-Via) transformer technologies for HV gate driver applications are proposed and demonstrated experimentally.
First, a novel fully integrated 3D TSV transformer is proposed, demonstrated, and characterized. The transformer enables complete 3D system integration and features both high galvanic isolation of > 4 kV DC and high voltage gain of > 0.7 (-3 dB) from 10 MHz to 100 MHz. Second, design optimization of the 3D TSV transformer has been experimentally demonstrated by varying the coil sizes, winding turn numbers, coil shapes, and metal track spacing. By changing these geometric parameters, tradeoffs between the different electrical performance can be made. This provides design flexibility for the transformer technology to be used in HV gate driver applications. Third, a simple, low cost monolithic 3D TSV transformer is designed and fabricated. Results show that the transformer achieves a voltage gain of 0.41 (-7.7 dB) over a frequency range of 4 MHz to 45 MHz using a chip area of 2 mm2 and with a galvanic isolation voltage of > 4 kV DC. Compared with those transformers with both coils built on the front-side or at the backside, this structure has the advantages of area-saving, cost-effectiveness, and simple fabrication process. Finally, in order to demonstrate the usefulness of the 3D TSV transformer technology for HV gate driver applications, discrete implementation of a digital isolator gate driver system using the proposed transformer technology is performed. In the system implementation, successful signal transfer through the transformer is clearly illustrated with a short delay time of 41 ns between the input and output of the system. Results show that the transformer technology is very promising for HV gate driver system-on-chip applications.

*** ALL ARE WELCOME !! ***