Patents by Inventor Petrus A. M. Weerdestein

Petrus A. M. Weerdestein 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).

  • Switching arrangement for increasing the white life of a high pressure sodium lamp
    Patent number: 5103141
    Abstract: The invention relates to a switching arrangement for operating a high-pressure sodium lamp which radiates white light in stable operating conditions. The switching arrangement is provided with switching means for switching current through the lamp by means of a drive signal generated in a drive circuit, which signal is based on a comparison between a reference value C and drive signal V+.beta.I, in which V is the lamp voltage, I is the lamp current, and .beta. is a constant. According to the invention, C may be adjusted in steps in dependence on the lamp voltage. Thus the duration over which the lamp radiates white light can be prolonged and brought into better accordance with the electrical lamp life.
    Type: Grant
    Filed: February 7, 1991
    Date of Patent: April 7, 1992
    Assignee: U.S. Philips Corporation
    Inventors: Robertus A. J. Keijser, Petrus A. M. Weerdestein