Voltage controlled light source and image presentation device using the same
US7456586B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jan 31, 2006 |
| Grant date | Nov 25, 2008 |
| Priority date | — |
| Expiry date | Dec 24, 2026 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B45/46
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A device (300) includes a driver circuit (200) having a field effect transistor (FET) (30), acting as a current sink, a current sense network (10), an operational amplifier (opamp) (20), and a light emitting diode (LED) (40). Current sense network (10) is connected to the source electrode (32) of FET (30), as well as to the inverting input terminal (22) of opamp (20). The non-inverting input terminal (24) of opamp (20) is coupled to a variable voltage control signal source (VDAC) (110). The output terminal (26) of opamp (20) is coupled to the gate electrode (36) of FET (30). LED (40) is connected to the drain electrode (34) of FET (30). The brightness of LED (40) is controlled by varying the amplitude of the VDAC control signal, and on/off status is controlled by a switch S1 disposed between the output terminal (26) of opamp (20) and the FET (30).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.