Modulating a constant current driver
For years I've been using CW drivers and have never needed to modulate one... until now. It needs to support a modulation frequency of up to 10kHz, as well as a variable pulse width. While the venerable DDL (Daedal) driver - virtually world famous and ubiquitous - is great, I am not sure about how well it would take to being wiggled at 10kHz.
I have attached a schematic of a simple two-transistor circuit that functions as a constant current regulator, and is modulatable. Theoretically. I'm going to be using the PHR diodes on this - I only need about 200mW output in the 635nm region.
Can those of you with greater experience with the intricacies of LD driving take a quick look and let me know if I'm headed down the right path, or am I doomed to cooking my LDs with this circuit?
The source will be battery, 6V, probably 4 x AA cells. I will not be driving the diode at max CW, probably somewhere about 80% max I at most.
I will probably also be using 2N2222As instead of the BC547s, since the 547s have a max Ic of 100ma, and the 2222s have a max Ic of 600ma, which can support the 220ma drive current for which I am designing.
Thanks for your wisdom and help!
Dave
Last edited by xanatos; 07-26-2011 at 11:19.
Awareness, Perception, Intent.