Thermal dimming has always been there, just need to test that it works correctly with threemode/trimode - so far it appears to be working correctly.sergio_pt said:
That's not a new function, it's supported in the current drivers. I'm pretty sure he just needs to test it to make sure the software changes didn't break that function.sergio_pt said:
It would shutdown if you are at the point of destroying the switcher IC, which means you have inadequate heatsinking or badly applied thermal paste. I've written a decent document regarding the thermal issues that need to be addressed and you can find it in the maxflex tech section on www.taskled.comsergio_pt said:
Woo Hootroutie-mtb said:
who would have thought the end result from a chance comment .
The thermal management white paper is a highly recommended read, too. I find both it and the manual a great help with my insomnia...georges80 said:
You have no heatsinking at all? If that's the case what do you expect... the switcher IC WILL overheat unless you're running pretty low current and minimal LEDs etc.sergio_pt said:
The information to calculate the actual IC failure temperature doesn't exist in a useful format unless you have a LOT of extra information. The Absolute Max Junction temperature is specified as 150C. The datasheet shows the thermal resistance of the package to the thermal pad. But then it goes through the PCB material and that has its own thermal resistance, then you have the thermal paste/epoxy you used with its thermal resistance, then the aluminium or whatever you used and finally to the body of the light itself.sergio_pt said:Well in fact I remember reading all that boring stuff before I assemble everything.
And I remember reading this in the thermal guide:
"At power levels with driver heat losses in the 2W range, it is sufficient to utilize a single heatsink attached to the gold thermal attachment area. As heat losses increase beyond 2W it may be necessary to provide heatsinking of the inductor to prevent shutdown and possible damage of the switcher IC. "
After reading everything and this conclusion you make it sound like losses higher than 2W are the worst case scenario, and you make it sound like IC heatsinking is just optional. As a newbie I just skipped that heatsinking and made a very good thermal path for the golden rectangle thinking it was enough.
Indeed the driver works well at sub-maximum levels but at max it shuts down in a couple of minutes.
You don't have any information about the IC failure temperature, that could be important info for the light designs.
Anyway I'll try to get a way to heatsink the IC with everything assembled
Good work with the programming.
By your description maybe the thermal epoxy is badly applied. I have used arctic alumina two part epoxy as you recommended on the pdf.georges80 said:
That's NOT a good combo - 3 li-ion to drive 7 LEDs will hurt the maxflex efficiency. That will cause overheating especially at 1A or 1.2A levels. Running 4 li-ion (series) is pretty well essential to push 1A or 1.2A to those 7 LEDs. 7 x 3.3V typ Vf means around 23V output and at 1A that's 23W to the LEDs. You likely have the driver running maybe 90% efficient depending on the state of charge of the 3 li-ion and any voltage losses in the wiring from the battery pack to the driver.sergio_pt said:
