Constant brightness liquid crystal display backlight control system
US5272327A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 26, 1992 |
| Grant date | Dec 21, 1993 |
| Priority date | — |
| Expiry date | May 26, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG09G2360/145
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A LCD backlight system which regulates the light generated by the lamp by controlling the intensity of the light using a photoresistor cell. The current provided to the lamp is controlled by a pulse width modulation (PWM) signal. The PWM signal responds to brightness adjustments by the user and to a photoresistor exposed to the light from the lamp. An operational amplifier circuit controls the PWM signal so that if the lamp is too bright, the current to the lamp is reduced, and if the lamp is too dim, the current to the lamp is increased. When the lamp brightness reaches the appropriate intensity, the output of the operational amplifier is unchanging, causing the intensity of the lamp to remain stable.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.