Laser diode voltage, how important? Driver recommendations?

[telmnstr]

Quick question: When I'm researching laser diodes everyone always talks about current. I understand that current limiting is important with laser diodes. But what about voltage?

I just took delivery of an Opnext HL63133DG which I plan to use in my projector. My current drivers I have laying around are two FlexMod P3 and two "whatever" china things(TTL). The china things I've got hooked to 445nm diodes -- the potentiometer on it doesn't seem to do anything.

I had intended to use the flexmod p3 to drive my Opnext, but after looking at specs the P3 is a 1.5vdc driver while the Opnext spec sheet calls for 2.7 to 3.2(max) vdc power supply.

I'm assuming if I drive it at 250-300ma on 1.5vdc I won't get the full power output? When I'm looking at drivers it doesn't always seem common to list the actual output voltage -- so I decided to ask :-) How much loss on the wrong voltage?

I'm after projector / show use, so analog modulation and non-pointer-mount are needed.

[VDX]

... the current is essential -- the voltage has only to be high enough to support the voltage drop across the drivers and the diode when running ...

[swamidog]

the flexmods will work fine.

Quick question: When I'm researching laser diodes everyone always talks about current. I understand that current limiting is important with laser diodes. But what about voltage?

I just took delivery of an Opnext HL63133DG which I plan to use in my projector. My current drivers I have laying around are two FlexMod P3 and two "whatever" china things(TTL). The china things I've got hooked to 445nm diodes -- the potentiometer on it doesn't seem to do anything.

I had intended to use the flexmod p3 to drive my Opnext, but after looking at specs the P3 is a 1.5vdc driver while the Opnext spec sheet calls for 2.7 to 3.2(max) vdc power supply.

I'm assuming if I drive it at 250-300ma on 1.5vdc I won't get the full power output? When I'm looking at drivers it doesn't always seem common to list the actual output voltage -- so I decided to ask :-) How much loss on the wrong voltage?

I'm after projector / show use, so analog modulation and non-pointer-mount are needed.

[Stiffler]

Hi telmnstr,

I too have been curious about this, since voltage and current depend on each other. Hopefully someone smarter than me can answer the question for both of us.

[telmnstr]

@Stiffler - sounds like not too important (I wouldn't over voltage though?)

@VDX / @Swamidog - thanks! I'll set it up on the flexmod then!

Thanks!

[swamidog]

excess voltage into the flexmod will not be passed to the diode. it will be dissipated as heat. it's always a good idea to heat sink your laser diode drivers.

i tend to bolt them, via the transistor tab, to my baseplate.

@Stiffler - sounds like not too important (I wouldn't over voltage though?)

@VDX / @Swamidog - thanks! I'll set it up on the flexmod then!

Thanks!

[telmnstr]

On the one flexmod I tested I bolted a standard to-220 heatsink to the transistor, but I've never had it on for more than a few minutes (set it up with the LPC-818 diodes or something, wasn't impressed with them.)

When it goes in the projector it should be running on a 5vdc switch-mode supply and I'll probably mount it to something solid and metal. Plastic case on the transistor so no need to worry about mica and screw insulators and all that (hooray!)

[swamidog]

the old flexmods had metal drain tabs and had to be electrically insulated, but the current generation is much easier.

On the one flexmod I tested I bolted a standard to-220 heatsink to the transistor, but I've never had it on for more than a few minutes (set it up with the LPC-818 diodes or something, wasn't impressed with them.)

When it goes in the projector it should be running on a 5vdc switch-mode supply and I'll probably mount it to something solid and metal. Plastic case on the transistor so no need to worry about mica and screw insulators and all that (hooray!)

[Stiffler]

Ok, bear with me for a second....Doesn't the input voltage directly determine the current that the diode will pass, or do diodes act differently than that? I have been assuming that diodes act like resistive loads once their forward voltage has been reached, please correct me if this is not the case.

[tadawson]

A diode looks more like a short circuit once it conducts - hence the need to regulate current. Voltage drop is largely due to the particular semiconductor composition that makes up the diode.

- Tim