LEDs for photographic applications

Linear has announced a two terminal constant current device.

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1040,C1055,P88400

This is a programmable current source that can be set to anything up to 200ma and upwards of 40 volts.

It's a good, cheap power controller for LEDs.

http://cds.linear.com/docs/Datasheet/3092p.pdf

Cost is in the $2.00 range. It might be necessary to parallel them or to use a current mirror to get the right current for specific LED strings.

Cypress has released a version of the PSoC that includes up to 4 MOSFETs for the purpose of controlling LEDs. Paired with the Cree LEDs this is a powerful tool for control of the devices. It would support calibration with a reference sensor, and accurate timing. Lots of options.

PowerPSoC® Embedded Power Controller
http://www.cypress.com/?id=2109

Labels: PSoC for LEDs

Power Supply

Switching regulator might be LM2700... http://www.national.com/ds/LM/LM2700.pdf

Interesting app note about a constant current switched supply variant in EDN.
April 14, 2005 number page 95 has design idea...

High-side current-sensing switched-mode regulator provides constant-current LED drive.

http://www.edn.com/article/CA514965.html

Op-amp Varieties

Site with summary of op amp circuits.

PSpice Application Notes Notes on how to PSPICE an LED from Orcad

Voltage-To-Current Converter Works From A Single-Supply RailSuper simple two op-amp constant current power supply.

Driving LEDs with Constant Current Port Expander Outputs

LED driver from Maxim

A linear Constant Current LED Lamp Dimmer

Interesting "built up" constant current supply for LEDs

Linear Technology

App Note on Linear LT1970 power op amp with current limiting/

Linear LT1970 Power Op Amp with current limiting.

Alternative to LM723 type regulator.

LM723 Data sheet in HTML...
ST Micro

LM723 data sheet -- National Semi