Integrated backlight display system for a personal digital assistant
US5736973A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 1, 1995 |
| Grant date | Apr 7, 1998 |
| Priority date | — |
| Expiry date | Nov 1, 2015 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02B20/30
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A backlighting system is placed in an elongated interior space within a personal digital assistant (PDA) which normally houses a stylus used to touch a liquid crystal display (LCD) touch and display screen. A backlight driver circuit is constructed on a printed circuit board (PCB) which fits within the elongated space, and an on-off switch extends from the PCB to an exterior hole formed in the PDA housing. An on-time control turns off power to the backlight driver circuit after a predetermined time has elapsed following activation of the on-off switch, and a dimming control controls the amount of energy delivered to the electroluminescent film. A torroidal switching transformer of a high voltage power supply minimizes noise, and a switching controller switches adjustable width current pulses through the transformer to regulate the high voltage level. A flyback circuit captures and uses a portion of the back EMF energy created when the current pulses are switched through the switching transformer. A H bridge of transistors alternately connects the high voltage positively and negatively to energize the electroluminescent film.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.