Hi colleagues, long time no c .. I was busy with reprap.org project so was bit more into software and mechanics then into electronics for quite some time now ...
At the moment, I'm trying to make a driver for 40W laser diode (max voltage 2.2V, min current 11A, max current 60A) and I need to make a current regulator to drive it.
I need to
- have max voltage limited at 2.2V
- have fine tuned current regulator between 10 and 60A
I have
- 10 of BUV48 transistors
- 2 MJ802 transistors
- 100 0R47 5W resistors
- 10 47R 50W resistors
- 5 2R2 100W resistors
- 9VAC 60A source
- 5VDC 60A source
- 3v3DC 50A source
- 3VAC 50A source
- whole bunch of other stuff that is not "high current"
For the "fixed current source" I'd go with simple opamp driving paralleled transistors with leads over shunt resistor.
Code:
VIN +------------\ />----[ LOAD ]---+---[ SHUNT ]---GND
| --- |
[ RES ] | |
| [OP-out] |
+-----[ OP+ ] [ OP- ]--------+
|
zener
|
GND
and then the current trough LOAD would be V(zener)/R(shunt) but since I want to go with 60A I cannot make Rshunt variable and I want to have fine regulation of current between 10 and 60A, and I don't know a pot that will pass trough 60A
nor one that is in the ballpark of 0.1R or less...
What I figured so far is that putting few (let say 6) BUV48 in parallel and driving them with another buv48 I will have the "driving" power. Using 20x5W 0R47 will get me shunt with low resistance and high power.
What I don't know how to do is - how to drive that initial BUV48 to get me the current I want. Mine initial idea was just to use 10K pot as a voltage divider (ends on + and gnd and center to base of transistor) to act as rudimentary voltage regulator, but the problem here is that small voltage changes can cause big jumps in current and that's not what I can afford (as I'm driving expensive laser with it).
Additional problem I didn't even scratch is whether the 2V will be enough to even open transistors ...
Anyone have any ideas?