Light-emitting diode array current power supply including switched cascode transistors
US5289112A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 21, 1992 |
| Grant date | Feb 22, 1994 |
| Priority date | — |
| Expiry date | Sep 21, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05F3/24
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A programmable power supply for driving LEDS is disclosed that includes a reference current leg and a number of output current legs. Both the reference current leg and the output current legs are further comprised of a plurality of parallel driver FET-control FET pairs, in which the driver and control FETs are connected in series. The driver FETs are biased by a reference voltage that provides a predetermined maximum output current. The control FETs are individually selected to provide a controlled output current. The individual control voltage is either a positive voltage, which disables the control FET, or a predetermined cascode voltage that places the control FET at or into the high output impedance saturation conduction region. By placing the control FETs into the saturation region, the output current is substantially insensitive to voltage fluctuations at the output
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.