Powering an LD to MAX

So I’ve learned that the initial start up of a laser diode is where it undergoes the most amount of stress, given that it is given a safe current, then even leaving them run for long periods of time. So, if you were to let a laser diode run for hours at a time, would be less stress on the diode then if you were to turn it on and off over and over with a few seconds between for 5 minutes. This being said, I set my driver to power a 405nm LD at 160mA, and it ran good for my first few tests. Then, (after about 1 min. usage) I set it to 180mA and the LD blew immediately as I switched it on. I also know some people push their diodes to even higher mA and haven’t had problems…yet. Now, we all want the most power of our laser diodes, and for 20-30 USD usually we aren’t too afraid to push them. But, through my experiences, they always die, sooner or later (not nearly as long when they are set to 150mA or lower current settings). So, when we switch on the power, it goes from 0 to 100% voltage/current immediately. Could you imagine how much stress your engine would undergo if it went from 0 to 7000RPM in a fraction of a second? I think that we could get allot more power and reliability if the driver ramped up, meaning gradually increasing current from the initial switch on. We could set it for the highest mA and wouldn’t need to fear that every time we switch it on it’s going to die. Any thoughts?

Peace, Ace

you could probably make a very simple device to do this, by adding a resistor off the driver, and connecting a large (read >1000uf) value capacitor to the leads of the diode - the capacitor absorbs the initial voltage and ramps up power to the diode more slowly than being immediately turned on

I believe the FlexDrive 2 has a soft start-up and delay.

So you're saying it may be possible to start your laser at a low current, let it warm up, then you'd be able to safely drive it at currents at which it would normally die with a harsh start-up...

Makes sense.

Yes you are right RA_pierce.

I started my open can diode on potentiometer full ratings and battries are connected already then I connect two wires from the driver output to my open can diode and it never light bright even in the first time. but dim light is comming.

I think it was fried in micro second.

then what about cd/dvd burners? don't those make the diode go on and off a few billion times? maybe the powers were at are a bit different than what it uses to burn...

sad_sagi said:

then what about cd/dvd burners? don't those make the diode go on and off a few billion times? maybe the powers were at are a bit different than what it uses to burn...

Click to expand...

Yes, but they don't need to deliver 200+mW every time, 80 - 120mW should be plenty sufficient for that, so it isn't necessarily powering it to MAX every time, or ever for that matter.

estvin said:

Yes you are right RA_pierce.

I started my open can diode on potentiometer full ratings and battries are connected already then I connect two wires from the driver output to  my open can diode and it never light bright even in the first time. but dim light is comming.

I think it was fried in micro second.

Click to expand...

I had a (estimated) 180mW blu ray running well for a short while (3 days of pretty good use) and that sucker was so powerful that no focusing was ever needed to burn, easily melt a plastic red cup from several feet away! Easily burn someone from accross a room, was very freaken powerful. I turned it on played with it, turned it off. a few seconds later, turned it on, and dim violet led light. must have fried in a fraction of a second.

well i was thinking if u had a one turn trim pot after the driver. then before u turn it on set the pot to max resistanse and turn it on. then turn on the diode and slowly let it warm up and slowly turn the pot.  

i think this may work becuase the max mA would be wat the driver is putting out and the min mA would be wat the lowest setting of the pot would be or the max resistance. 

Ace82 said:

[quote author=estvin link=1223400559/0#3 date=1223840685]Yes you are right RA_pierce.

I started my open can diode on potentiometer full ratings and battries are connected already then I connect two wires from the driver output to  my open can diode and it never light bright even in the first time. but dim light is comming.

I think it was fried in micro second.

Click to expand...

I had a (estimated) 180mW blu ray running well for a short while (3 days of pretty good use) and that sucker was so powerful that no focusing was ever needed to burn, easily melt a plastic red cup from several feet away!  Easily burn someone from accross a room, was very freaken powerful.  I turned it on played with it, turned it off.  a few seconds later, turned it on, and dim violet led light.   must have fried in a fraction of a second.  [/quote]


Some diodes are stronger then others. I don't push my diodes past 125 even though I know they can take it but I just don't want to have to replace them.

Anybody know the RATED current for the 6x? :-/ LOL I'll probably not use it but I would really like to know.

--hydro15