Method and circuit for an efficient and scalable constant current source for an electronic display
US7598800B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 22, 2007 |
| Grant date | Oct 6, 2009 |
| Priority date | — |
| Expiry date | Jun 26, 2027 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG05F3/205
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
The present invention uses two transistors instead of a sensing resistor to provide a constant current source for a load such as an array of light emitting diodes (“LEDs”). In the present invention, a bias current is applied to a branch of the circuit. The drain-to-source voltages of two transistors are matched. The voltage at the gate of both transistors is controlled based on the bias current and the drain-to-source current of the first of the two transistors. The second of the two transistors is sized such that source current of the second transistor is a multiple of the source current of the first transistor for a given gate voltage. By the techniques of this invention, the load current in a circuit is efficiently kept constant at a multiple of the input bias current.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.