Badpip driver failure?

[kovacika]

So...the other day I was working on aligning my new build that uses bad pips 2ch driver to power a red diode (p73) and a blue diode (9mm 445). I was powering it with a 24v meanwell power supply and running the red at ~800ma and the blue at about ~2000ma. I had just checked the red blue alignment at full intensity, and was backing the intensity down to ~30% when with a small "fzzt" sound the red diode stopped lasing. I measured the output voltage of the blue driver channel at 30% and it was fairly low (cant remember for for sure, but a couple volts or so). When I measured the red channel at 30% output, it was reading 24v. Now I don't know if those values are helpful for me, but I was hoping someone could shine some light on where I went wrong. PS: the red diode died as well as the driver channel.

Thanks,
Aaron

[Fotobysw]

So...the other day I was working on aligning my new build that uses bad pips 2ch driver to power a red diode (p73) and a blue diode (9mm 445). I was powering it with a 24v meanwell power supply and running the red at ~800ma and the blue at about ~2000ma. I had just checked the red blue alignment at full intensity, and was backing the intensity down to ~30% when with a small "fzzt" sound the red diode stopped lasing. I measured the output voltage of the blue driver channel at 30% and it was fairly low (cant remember for for sure, but a couple volts or so). When I measured the red channel at 30% output, it was reading 24v. Now I don't know if those values are helpful for me, but I was hoping someone could shine some light on where I went wrong. PS: the red diode died as well as the driver channel.

Thanks,
Aaron

Did you have a heavy heatsink on it. I found that when I ran my diodes at 75% on 12v that the driver gets extremely hot. The way it sounds it did about what mine did although mine still works fine. I shut it off as soon as I saw the drop in brightness. It needs a really good heatsink and maybe active cooling like a fan or a pielter chip. Even now I have a good heatsink on mine and it is still quite hot. So it sounds like it may have gotten too hot.
Steve Wall

[norty303]

24v sounds very high! You will have a LOT of heat to dissipate.
I run my red and blue combo on 6v specifically to keep the heat down

[kovacika]

It was on quite a large heatsink that is fan cooled. The heatsink was barely even warm. Norty, you say that you run your red/blue off 6v, what kind of amperage are you supplying to your diodes? I was under the impression that you needed higher voltage to gain the higher amperage out of the bad pip driver. It says in his add that "it will drive a 445nm diode to 900ma off a 5v supply". Is that the max you can get out of a 5 volt supply?

[norty303]

The 445 is 1.5A (1400mW) and the 637 is 800mA (650mW) and they run fine down to 5.35v at which point they start to current limit the blue. This is using a dual channel badpip driver.

[kecked]

If you go over 12v on any of these diodes you are dumping major heat for no reason and stressing the driver. Vf green is 8.4 Vf blue is 4.85 ish Vf reds 2-3v so the drop on the control element is insane as it has to suck up the excess. look at it this way for say a blue 24v-5v=19v 19v*2a=38W best case. 12v-5v=7v*2a=14w 1/3 the heat same job done. drop to 6v and you have 6v-5v=1v*2a=2W. Higher voltage doesn't serve a purpose unless the driver is badly designed and needs a large volatge drop on the control element. The only reason to go to 12v is for the greens and then its 12v-9v=3v*0.3a=0.9W. You need typically 5V to drive the opamps so even for reds stay at 5v

Red=5V
Blue=6V
Green=12v

One other point to bear in mind is pcb trace size. these are typically 0.6mm and are not able to take more than about 2.5-3a. You need 2.5mm trace for 6a and 7mm for 15a. That's not on a pcb I've seen so keep the currents below 3-4a.

I think you made a thermal run away mess that killed you.

[kovacika]

kecked, that makes sense. I guess I just never thought of the extra voltage as just extra heat. Oh well. Lesson learned. Time to buy a smaller supply.

Thanks guys!
Aaron