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Help me understand how these cheap LED drivers work


Jun 22, 2012
I've heard many of these cheap LED drivers can be used for constant-current applications with laser diodes. I'm trying to grok the way one like this works:

1.5V~4.2V 3W Cree Circuit Board for Flashlights (16.7mm*5.6mm) - Free Shipping - DealExtreme

- 1*Cree 3W regulated power output
- Output current: 1.5V 600±50mA; 4.2V 1.2A
- 16.7mm diameter base, 5.6mm overall depth
- Voltage: 1.5V-4.2V
- Fully regulated circuit design

Specifically - how do you set the output voltage? How do you do that with any board? I mean, some diodes need higher voltages than others, regardless of the current sought.

To me, it looks like this board does not cause a hit on the voltage, that is, 3.7V in would be 3.7V out and in the case of this board, something around 1A.

Is there a good cheap way to drive a wide range of diodes? I have several ranging from 300mW reds to the 1~2W 445.

Thanks in advance.