Wow the Fireflies driver is impressive! Iāve been using the Nov-MU on a daily basis and absolutely love it. Too bad they seem to be having difficulty sourcing components for the driver for the past year.
Itās pretty good yeah, what is disappointing is that there not enough input capacitance and when a higher DCIR cell is used like a 50E or an older cell then the output can be unstable, which when itās pronounced will lower efficiency, output and generate noise which several people have reported, it does it with my P42A that is not even that old.
It uses the amount of capacitance suggested in the datasheet (2x 10uF 0603) but in my experience of building drivers the suggested input capacitance for buck converters is usually not enough.
I added more caps, two 10uF 0603 stacked and one 0805 22uF farther away by removing some solder mask, but I havenāt reassembled it yet to fully test it.
Another (small) issue is the max current of 5.5A, the traces resistance on top of the sense resistance were likely not taken into account when deciding on the Vsense.
This data is really interesting, thanks for providing it. Seems like the E12R and SC700 do quite well. Do any of the other ZLs have the same high resistance negative ground spring issue, or is that just the H600? Does SC600?
SC64w HI also seems pretty decent. Do you know how SC64c LE would do? I wonder, since I would guess that would be a 3V buck or buck/boost, in contrast to the boost used by the other 3 models here.
Why do you think some of these drivers have lower efficiency than some of the driver designs Iāve seen around here on BLF (such as yours)? Are there particular design limitations involved for these companies?
hm
all that means to me is, i might need to charge in 8 days vs 8.34. with one light vs another. sometimes. if the LED efficiency doesn;t invalidate the driver efficiencyā¦
Seriously great topic, thefreeman! So fascinating to see how efficiency changes across the output selections. Iām impressed at how well the Skilhunt H04 does. In my anecdotal experience with my H03, I felt it was an efficient flashlight based on how long the battery charge would last with usage at a variety of brightness levels. The Zebralight is SC64c LE is rather disappointingā¦ Iād been under the impression that itās a nicely efficient design. Iām tempted to do a crude head-to-head test of mine with a few other 18650 flashlights all running the same 18650 cell spec, and see how it does.
Thanks
I havenāt tested the SC64c LE (3V), only the SC64 (12V), the former will likely be more efficient, Iām not sure what is exactly the issue with the TPS61088 used in the SC64 but the efficiency drops at 12V output, boosting to higher voltage (12V vs 6V) is a bit less efficient but not that much.
I havenāt disassembled my SC64 LE yet but I will measure it in the future, itās a 3A synchronous buck driver based on the TLV62085, it should be more efficient.
Regarding drivers having better efficiency itās mostly about using better components : lower resistance PFET (for the reverse polarity protection), inductor, sense resistor, switching/rectifier FETs, for converters IC theyāre integrated in the IC, so itās about choosing a good converter, and one with synchronous rectification i.e the rectifier is a FET and not a diode (asynchronous).
I hadnāt considered the relative efficiency here; yeah, the SC700 XHP50 rather trounces the H04. Thatās sad to hear theyāve cheapened out on components for the H04. I wonder how the M200 series fares in comparisonā¦
I upgraded my measurements setup, before I used 2 Uni-t UT210E current clamps (2+3) , an Uni-t UT139C (0.5+2) and a RDtech āprecisionā voltmeter.
Now I measure the current across 0.1% current shunts with a BM867s (0.032), Aneng AN870, Owon B41t and a RDtech precision voltmeter, the 3 later voltemeters are calibrated against the BM867s and are within 0.02.
Are losses in efficiency somewhat linear with output current when using Monolith boost converter? If Emisar/Noctigon driver has 95% at 2A, this has 92% at 2.5A then how probable is it, that this driver would have ~88% at 3A?
Well power losses are not linear (which would mean constant efficiency), a large proportion are conduction losses (I^2 x R), but you can see from my graphs (I should redo them with my new setup) that efficiency points arenāt linear either, but especially I think itās the temperature increase that greatly increases power losses at high currents and tanks the efficiency, because running simulations without temperature modelisation gives a fairly straight efficiency curve.
Anyhow the Emisar boost driver efficiency is lower than that according to Hankās measurements :
Which isnāt surprising since the inductor is smaller.
Edit : Vout is also higher.
The efficiency isnāt as good as it usually is with this converter, it has quite thin traces, fairly high current sense resistor and too low inductance.
Input capacitance is quite low (one 0805 capacitor), I had to add a bulk capacitor for making the measurements as it didnāt work properly in turbo.
For high power converters (integrated FETs) I donāt think so, Analog devicesā highest switch limit boost converter is 7A (and itās a dual phase, 6A for a single phase one), whereas TI has two 10A ones (TPS61088, TPS61178) and a 15A one (TPS61288) and MPS has several above 10A. But for lower power there are many manufacturers
What do you think would happen if using 2 boost converters in parallel or series? Is it viable to achieve higher output currents without hit to efficiency when using parallel setup for example?