Patents by Inventor Lee H. Johnston

Lee H. Johnston 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).

  • Patent number: 7324356
    Abstract: A mechanism for reducing common-mode current in a system including a first subsystem and an isolated subsystem. The isolated subsystem may receive the common-mode current from the first subsystem via an isolation mechanism. The isolation mechanism (e.g., a transformer) may isolate the isolated subsystem from the first subsystem by blocking DC signals. The first subsystem may include a pulse generation unit and compensation circuitry. The pulse generation unit may provide a first pulse and a second pulse to the compensation circuitry. The phase and duty cycle of the pulses may be varied based on measured characteristics of the isolation mechanism. The compensation circuitry may generate a cancellation signal based on the first and second pulses. Furthermore, the compensation circuitry may provide the cancellation signal to a ground plane of the isolated subsystem to reduce the common-mode current received at the isolation subsystem.
    Type: Grant
    Filed: October 21, 2005
    Date of Patent: January 29, 2008
    Assignee: National Instruments Corporation
    Inventor: Lee H. Johnston