Printable View
When running diodes wired in series, doesn't it cut in half the voltage going to each diode? So if you are using 0-5 volts to modulate 1 diode, if you put 2 diodes in series wouldn't you need 0-10 volts? Or, do I have that backwards and 2 diodes in series would only need 0-2.5 volts input to give each diode 0-5 volts?
No, laser diode drivers are current limiting, so as long as your supply voltage is 2 times the diode voltage plus a little for the driver, the driver will push the required current through the diodes.Quote:
Originally Posted by Phredy1
Modulation voltage is still 0-5v
Ok, I will buy that. So if you were using say a flexmod to power 4 diodes in series, would you need to supply the input voltage to the flexmod at a little over 20 volts?Quote:
Originally Posted by Doc
If a person was to just use a PSU to test diodes, for 1 diode you could use up to 5 volts. If you had 2 diodes in series you would use up to 10 volts to power both diodes, correct? Or am I missing the boat here?
It depends on the forward voltage of the diodes, if they're reds that will probably be around 2v, if they're the 445 diode it would be around 5v.
I run my dual 445 in series using a flexmod 2, I use a 12v supply.
The only reason I decided on series was because the Flexmod 2 offered more diode protection when configured for its low (up to 2 Amps) current range.
When running in series it doesn't matter how many you have in the string; the current doesn't increase, you just need enough voltage to push the current. I don't know about the Flexmod 3, but the 2 only dropped a little over a volt itself.
Ian
would a combination work?
i.e. i have 12 LOCs
to drive them in series i would need more than 12*2 = 24volts (24 + Vdrop at the psu). to drive them in parallel i would need more than 12*250mA = 3amps. both solutions look quite demanding in terms of psu (a flexmod p3 can take it easily but i don;t want to stress things so much)
i was thinking about an intermediate solution, to drive them in parallel in groups of 4 and then have all groups wired in series, so i would need overall 1 amp (4*250mA) and 6 volts (2+2+2+Vdrop at the psu).
For 12 diodes I would go with parallel and balancing resistors, the flexmod will be fine with a decent heatsink, also you are not running them in CW, they will be run at a percentage duty cycle.