The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 09, 1996
Filed:
Sep. 10, 1993
Daniel B Reents, Spring, TX (US);
Patrick R Cooper, Houston, TX (US);
James H Garrett, Spring, TX (US);
Philip J McKenzie, Houston, TX (US);
Compaq Computer Corporation, Houston, TX (US);
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.