Breaking diodes? How easy is it?

[mikkojay]

I had bad experiences with a bad PSU, killing opnext diodes, so I can only agree

Owchie! My condolences.. Good point to remember though.

[heroic]

I had bad experiences with a bad PSU, killing opnext diodes, so I can only agree

a good PSU has an isolated output and there's no voltage between V+ and earth expect the regulated DC output voltage if you ground both V- and earthing

That's why I love these- they are current limited, 5kV isolated, soft start and guaranteed shutdown characteristics:

[ElektroFreak]

It could also be you power supply, some Switched PSU's gives a small voltage spike when mains is cut and kills the diode as the driver has no protection. (have killed many diodes this way!)

better drivers have there own regulated PSU on board.


Make sure you cut the secondary side of the PSU first before cutting the primary mains.

I asked drlava about whether or not the flexmod has any protection against transients and he stated that there is a diode/capacitor combo on the input which should protect against almost all spikes, but since I've killed one 445nm diode so far from a voltage spike of some sort I'd say that the protection might not be 100% effective. Of course a lasorb would make this issue moot.

[norty303]

would make this issue moot

YAY YOU!!

You wouldn't believe how angry I get when I have to read 'mute' in the same context....

[mccarrot]

I asked drlava about whether or not the flexmod has any protection against transients and he stated that there is a diode/capacitor combo on the input which should protect against almost all spikes, but since I've killed one 445nm diode so far from a voltage spike of some sort I'd say that the protection might not be 100% effective. Of course a lasorb would make this issue moot.

A capicitor and/or diode will protect agains very short spikes, but a bad psu can give a higher voltage then you want for a longer time causing a huge current trough the diode and killing it. the driver does not protect against this.

See it like you adjusted the driver for 5V operation, and you run it for a very short time at 24V. this way you will have 5x the current trough the diodes and will kill it. the driver will just deliver the current for a short period in this case. no capicitor will help you.


A 5,1V zener to clamp the voltage would help in this case, but this would limit the driver to 5V only.

A good driver will have it own independent PSU for the laserdiode driver, so it will be indepandant from the bad outside world.

[mccarrot]

That's why I love these- they are current limited, 5kV isolated, soft start and guaranteed shutdown characteristics:

this in combination with a flexmod would make a very nice driver for the 445nm diode.

for LOC's (with the cathode connected to the case) I would still recommend a high side driver (sorry drlava)

[DanBarlow]

Well, I did a dirty press fit mount just to get an idea of the thermal response, and it survived. ;-) I did see the threshold movement as it warmed up. I need a mill though, concentric drilling leaves an angled shoulder that doesn't have as much contact as I want. Thanks Daniel B.!