1.5A Constant Current Linear Regulator for LEDs For

So there are a ton of instructables covering the use of high brightness leds. Many of them use the commercially available Buckpuck from Luxdrive. Many of them also use linear regulation circuits that top out at 350 mA because they are highly inefficient. This instructable serves to let people know that there are other options out there to drive high power leds. We came upon this project in the work we are doing with a customer for a high power led strobe [www.ohararp.com/blog.html]

The heart of this project is the STCS1 from STM Electronics:
http://www.st.com/stonline/products/literature/ds/13415/stcs1.htm

Warning: Some parts of this project were designed and fabbed using professional software and hardware. However, all aspects of this design could be done using open source products or some perf board and wire wrap.

Step 1: Read the Data Sheet!

First step with any electronics project is to read the data sheet:

http://www.st.com/stonline/products/literature/ds/13415/stcs1.pdf

From this we can easily see some of the key features of this chip:
■ Up to 40 V input voltage
■ Less than 0.5 V voltage overhead
■ Up to 1.5 A output current
■ PWM dimming pin
■ Shutdown pin
■ LED disconnection diagnostic

Step 2: What Else Do We Need? How Bout 5V@20mA

Because I wanted this design to have a nearly identical pinout as the BuckPuck from Luxdrive I decided to add a simple 5V@20 mA

Step 3: Layout the PCB!

Using the connectivity of the schematic layout your board for the simplest wiring configuration as possible. This might take some time but your patience here will serve you well. This applies to all layout methods. Here you can clearly see we are using 1206 packages for all of our resistors, capacitors, and diodes.

Step 4: Wired Up!

Here's everything wired up. Unfortunately we had to use the bottom plane and some vias to completely route this board.

Here are the Gerber Files of this board.

Step 5: Order and Assemble the Board

Using your favorite pcb vendor and assembly method you can put together the board pretty quickly. We prefer http://www.goldphoenixpcb.biz/ for our boards and then we use kapton stencils, kester solderpaste, and a reflow skillet or oven to assemble our boards.

Step 6: Let the Blinding Begin!

With the .1" spacing on the pinout of this board you can very easily breadboard your project. Here we are powering a string of 3 x K2 Luxeons (140 lumens per led) from a 12V wall wart capable of supplying 3000 mA.

The performance of this chip is pretty amazing. At 1500 mA the driver board is barely warm to the touch when driving leds continuously.

Note: This design is for a strobe light where the leds do not stay on very long. For continuously running the leds you MUST mount them to a heatsink to dissipate the heat that is produced.

All parts for this design can be found at Mouser or Digikey:
Here's the BOM

Driver IC - STCS1