Patents by Inventor Philip J. McKenzie

Philip J. McKenzie 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).

  • Circuit for controlling bias voltage used to regulate contrast in a display panel
    Patent number: 5534889
    Abstract: A liquid crystal display (LCD) panel which has its contrast controlled through the use of a pulse width modulation (PWM) circuit contained in the video controller and a contrast control circuit. In response to a particular video refresh mode, the PWM circuit modulates the pulse width of a signal that is an input to the contrast control circuit. The pulse width is changed by the use of a base contrast register and two offset registers. Depending on the video mode, the base register is used alone or is combined with one of the offset registers to provide a signal to indicate the duty cycle of the signal. The pulse width modulated signal is converted to a DC bias contrast voltage which is provided to the LCD panel.
    Type: Grant
    Filed: September 10, 1993
    Date of Patent: July 9, 1996
    Assignee: Compaq Computer Corporation
    Inventors: Daniel B. Reents, Patrick R. Cooper, James H. Garrett, Philip J. McKenzie
  • Tapped inductor slave regulating circuit
    Patent number: 5336985
    Abstract: A tapped inductor slave regulating circuit provides a second slave output voltage derived from a tapped connection to the filter storage inductor of a first output voltage of a switching power supply converter. In the converter, an unregulated voltage is provided through a switching circuit to a storage inductor to develop a first output. The switching circuit is turned off and a synchronous rectifier is turned on to freewheel the current through the storage inductor and the load. The storage inductor is center-tapped and coupled to a switching circuit to provide a second slaved output. The location of the center tap is chosen to provide the proper voltage of the second output. In one embodiment, the switching circuit for the slaved output is turned on during the freewheel portion of each cycle to provide a proper voltage level for the second output. In another embodiment, a separate local feedback circuit is provided to further regulate the second output voltage level.
    Type: Grant
    Filed: November 9, 1992
    Date of Patent: August 9, 1994
    Assignee: Compaq Computer Corp.
    Inventor: Philip J. McKenzie
  • Technique for trimming photoresistors and trimmed photoresistors
    Patent number: 5309132
    Abstract: A technique for trimming photoresistors to change relatively high tolerance parts to relatively low tolerance parts by blocking out a portion of the photoactive area, and the so-trimmed photoresistors. The blocking out can be performed by placing ink over the photo-active area. This ink placement step can be easily added in the photoresistor assembly line after the initial calibration location.
    Type: Grant
    Filed: April 2, 1993
    Date of Patent: May 3, 1994
    Assignee: Compaq Computer Corporation
    Inventors: Nathan A. Mitchell, Philip J. McKenzie