Research articles, presentations, and other scholarship

Recent Submissions

  • Structural Resemblance Between Droop Controllers and Phase-Locked Loops 

    Zhong, Qing-Chang; Boroyevich, Dushan (IEEE, 2016)
    It is well known that droop control is fundamental to the operation of power systems and now the parallel operation of inverters, while phase-locked loops (PLLs) are widely adopted in modern electrical engineering. In this ...
  • Parallel devices having balanced switching current and power 

    Virginia Tech Intellectual Properties, Inc.; Toyota Motor Engineering & Manufacturing North American, Inc.; Wang, Chi-Ming; Mao, Yincan; Miao, Zichen; Ngo, Khai D. (United States Patent and Trademark Office, 2018-10-30)
    A power circuit includes a power source for providing electrical power and two driving transistors being disposed in parallel and receiving electrical power from the power source. Each of the two driving transistors includes ...
  • Low profile coupled inductor substrate with transient speed improvement 

    Virginia Tech Intellectual Properties, Inc.; Li, Qiang; Lee, Fred C.; Su, Yipeng; Hou, Dongbin (United States Patent and Trademark Office, 2018-10-23)
    A low profile inductor structure suitable for use in a high power density power converter has one or more windings formed by vias through a thin, generally planar body of magnetic material forming the inductor core and ...
  • Transient performance improvement for constant on-time power converters 

    Virginia Tech Intellectual Properties, Inc.; Li, Qiang; Liu, Pei-Hsin; Lee, Fred C.; Bari, Syed (United States Patent and Trademark Office, 2018-10-23)
    Response of a variable frequency switching constant on-time or adaptive on-time controlled power converter to a large step-up or step-down change in load is improved with a simple circuit that detects magnitude and polarity ...
  • Multi-step simplified optimal trajectory control (SOTC) based on only Vo and I load 

    Virginia Tech Intellectual Properties, Inc.; Li, Qiang; Lee, Fred C.; Fei, Chao; Feng, Weiyi (United States Patent and Trademark Office, 2018-09-11)
    A resonant power converter is disclosed with a driving circuit generating a switching signal connecting power to a resonant tank circuit, with a voltage monitoring circuit measuring a voltage output and a load current. A ...
  • Semiconductor module arrangement 

    Virginia Tech Intellectual Properties, Inc.; DiMarino, Christina; Boroyevich, Dushan; Burgos, Rolando P.; Johnson, Mark (United States Patent and Trademark Office, 2018-07-24)
    In a switching module structure that includes a low-impedance path to ground, such as a parasitic capacitance of an insulating substrate, a further insulating substrate presenting a parasitic capacitance placed in series ...
  • Hybrid interleaving structure with adaptive phase locked loop for variable frequency controlled switching converter 

    Virginia Tech Intellectual Properties, Inc.; Li, Qiang; Liu, Pei-Hsin; Lee, Fred C. (United States Patent and Trademark Office, 2018-07-03)
    In a multi-phase power converter using a phase-locked loop (PLL) arrangement for interleaving of pulse frequency modulated (PFM) pulses of the respective phases, improved transient response, improved stability of high ...
  • Power-cell switching-cycle capacitor voltage control for modular multi-level converters 

    Virginia Tech Intellectual Properties, Inc.; Wang, Jun; Boroyevich, Dushan; Burgos, Rolando P.; Wen, Bo (United States Patent and Trademark Office, 2018-05-08)
    In a modular multi-level power converter, additional switching states are interleaved between main switching states that control output voltage or waveform. The additional switching states provide current from a DC-link ...
  • Power switch drivers with equalizers for paralleled switches 

    Virginia Tech Intellectual Properties, Inc.; Miao, Zichen; Ngo, Khai D.; Zhang, Lujie (United States Patent and Trademark Office, 2018-06-12)
    Capacitors connected between gate terminals of a plurality of parallel-connected power transistors are charged and discharged in each switching cycle to provide a plurality of power transistor control waveforms from a ...
  • Energy storage for power factor correction in battery charger for electric-powered vehicles 

    Virginia Tech Intellectual Properties, Inc.; Wang, Hui; Ngo, Khai Doan (United States Patent and Trademark Office, 2018-03-13)
    Switches of a switching circuit used to control operation of an electric motor such as in an electrically powered vehicle connect respective windings of the electric motor as a single phase inductor during battery charging. ...
  • Method and apparatus for current/power balancing 

    Virginia Tech Intellectual Properties, Inc.; Toyota Motor Engineering & Manufacturing North American, Inc.; Wang, Chi-Ming; Mao, Yincan; Miao, Zichen; Ngo, Khai D. (United States Patent and Trademark Office, 2018-03-20)
    Aspects of the disclosure provide a system having a power circuit. The power circuit includes a first switch circuit having at least a first transistor and a second switch circuit having at least a second transistor. ...
  • Universal system structure for low power adapters 

    Virginia Tech Intellectual Properties, Inc.; Li, Qiang; Lee, Fred C.; Huang, Xiucheng (United States Patent and Trademark Office, 2017-12-19)
    A two-stage power converter architecture including an isolation transformer and rectification of the isolation transformer output by an LLC resonant circuit and methodology for operating the same feeds an output voltage ...
  • Avoiding internal switching loss in soft switching cascode structure device 

    Virginia Tech Intellectual Properties, Inc.; Li, Qiang; Lee, Fred C.; Huang, Xiucheng; Du, Weijing (United States Patent and Trademark Office, 2017-08-15)
    In a cascode switching device, avalanche breakdown of a control transistor and loss of soft switching or zero voltage switching in a high voltage normally-on depletion mode transistor having a negative switching threshold ...
  • External ramp autotuning for current mode control of switching converter 

    Virginia Tech Intellectual Properties, Inc.; Liu, Pei-Hsin; Lee, Fred C.; Mattavelli, Paolo; Yan, Yingyi (United States Patent and Trademark Office, 2017-06-13)
    Peak current, valley current or average current mode controlled power converters in either digital or analog implementations obtain a stabilized feedback loop and allow high system bandwidth design by use of an external ...
  • Maximum power point tracking for solar panels 

    Virginia Tech Intellectual Properties, Inc.; Lee, Fred C.; Wang, Feng; Wu, Xinke; Wang, Zijian (United States Patent and Trademark Office, 2017-06-20)
    Approximately one-half of the loss of delivered power from a solar panel having photovoltaic (PV) cells connected in series to form sub-panels due to shading is recovered at low hardware cost by connecting sub-panels in ...
  • Colossal tunability in high frequency magnetoelectric voltage tunable inductors 

    Yan, Yongke; Geng, Liwei D.; Tan, Yaohua; Ma, Jianhua; Zhang, Lujie; Sanghadasa, Mohan; Ngo, Khai; Ghosh, Avik W.; Wang, Yu U.; Priya, Shashank (2018-11-27)
    The electrical modulation of magnetization through the magnetoelectric effect provides a great opportunity for developing a new generation of tunable electrical components. Magnetoelectric voltage tunable inductors (VTIs) ...
  • Correlation between tunability and anisotropy in magnetoelectric voltage tunable inductor (VTI) 

    Yan, Yongke; Geng, Liwei D.; Zhang, Lujie; Gao, Xiangyu; Gollapudi, Sreenivasulu; Song, Hyun-Cheol; Dong, Shuxiang; Sanghadasa, Mohan; Khai Ngo; Wang, Yu U.; Priya, Shashank (Springer Nature, 2017-11-22)
    Electric field modulation of magnetic properties via magnetoelectric coupling in composite materials is of fundamental and technological importance for realizing tunable energy efficient electronics. Here we provide ...
  • Zero-current transition PWM converters 

    Center for Innovative Technology; Intellectual Properties | Kft; Virginia Polytechnic Institute and State University; Lee, Fred C.; Hua, Guichao C. (United States Patent and Trademark Office, 1996-01-23)
    A zero-current transition pulse-width modulated (ZCT-PWM) d.c.-d.c. converter allows minority-carrier semiconductor devices such as, for example, bipolar junction transistors (BJTs), insulated gate bipolar transistors ...
  • A diffusion-viscous analysis and experimental verification of defect formation in sintered silver bond-line 

    Xiao, K.; Ngo, K. D. T.; Lu, G. Q. (Cambridge University Press, 2014-04-01)
    The low-temperature joining technique (LTJT) by silver sintering is being implemented by major manufacturers of power electronic devices and modules for bonding power semiconductor chips. A common die-attach material used ...