Circuit for controlling bias voltage used to regulate contrast in a display panel
US5534889A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 10, 1993 |
| Grant date | Jul 9, 1996 |
| Priority date | — |
| Expiry date | Sep 10, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09G3/36
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.