Direct drive backlight system
US5930121A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 13, 1998 |
| Grant date | Jul 27, 1999 |
| Priority date | — |
| Expiry date | Mar 13, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B41/3927
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A power conversion circuit drives a cold cathode fluorescent lamp (CCFL) while requiring minimal number of external components. The circuit includes a controller, a direct drive network responsive to control inputs from the controller and coupled to receive a power signal, and a secondary network coupled to the CCFL. The direct drive network is low Q circuit comprising a plurality of switching transistors and a primary winding of a transformer such that an impedance of the direct drive network consists essentially of an inductance of the primary winding and capacitance of the direct drive network consists essentially of parasitic capacitance reflected from the secondary winding. The Q of the direct drive network is less than about 0.5 so that a square wave voltage signal is provided across the primary winding of the transformer. However, the inductance of the transformer is sufficiently high such that the voltage across a secondary winding of the transformer is sinusoidal. The secondary network comprises the secondary winding of the transformer coupled to the CCFL through a connector to provide a sinusoidal current to the CCFL. The controller controls the current passing through th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.