Patents by Inventor Guichao C. Hua

Guichao C. Hua has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Zero-current transition PWM converters
    Patent number: 5486752
    Abstract: 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 (IGBTs), MOSFET controlled thyristors (MCTs), and gate turn-off thyristors (GTOs), to be used as switches for high-power, high frequency applications. The ZCT-PWM converter comprises a shunt resonant branch inserted into a conventional PWM converter circuit. The resonant branch comprises a resonant inductor (Lr), a resonant capacitor (Cr), an auxiliary switch (S1), and an auxiliary diode (D1). The resonant branch is only active during a relatively short switching time in order to create a zero-current switch condition for the main pulse-modulating switch (S) without substantially increasing voltage or current stresses.
    Type: Grant
    Filed: June 17, 1994
    Date of Patent: January 23, 1996
    Assignees: Center for Innovative Technology**, Virginia Polytechnic Institute & State University, Intellectual Properties, Inc.
    Inventors: Guichao C. Hua, Fred C. Lee
  • Soft-switching PWM converters
    Patent number: 5442540
    Abstract: A full-bridge zero-voltage-switching pulse-width-modulated converter employs a saturable reactor in place of the linear inductor in order to reduce current stress on the active switches, reduce voltage stress on the rectifier diodes, and reduce secondary parasitic ringing. The zero-current-switching full-bridge pulse-width-modulated converter embodiment of the invention contemplates the provision of active switches that are zero-current-switched and passive switches, such as diode switches, that are zero-voltage-switched.
    Type: Grant
    Filed: June 25, 1992
    Date of Patent: August 15, 1995
    Assignees: The Center for Innovative Technology, Virginia Polytechnic Institute & State University, Virginia Tech Intellectual Properties, Inc.
    Inventors: Guichao C. Hua, Fred C. Lee
  • Zero-voltage-transition pulse-width-modulated converters
    Patent number: 5418704
    Abstract: To date, soft-switching techniques applied to the PWM converters, with the exception of a few isolated cases, are subjected to either high switch voltage stresses or high switch current stresses, or both. This invention presents a new class of zero-voltage-transition PWM converters, where both the transistor and the rectifier operate with zero-voltage switching, and are subjected to minimum voltage and current stresses. Breadboarded converters are constructed to verify the novelty of the proposed new family of converters.
    Type: Grant
    Filed: May 24, 1993
    Date of Patent: May 23, 1995
    Assignee: Center for Innovative Technology
    Inventors: Guichao C. Hua, Fred C. Lee
  • Zero-voltage transition PWM converters
    Patent number: 5262930
    Abstract: A pulse-width-modulated, quasi-resonant, d.c. to d.c. converter that has an auxiliary switch that periodically kills the resonance.
    Type: Grant
    Filed: June 12, 1992
    Date of Patent: November 16, 1993
    Assignee: The Center for Innovative Technology
    Inventors: Guichao C. Hua, Fred C. Lee