It would actually be interesting if you could do comparative measurements of classic BLF-type drivers with 1+n+fet topology and fet only topology.
I’ve seen pictures of theory, how having multiple different 7135 channels affects effiency, but never any measurements.
Freeman this is a really great contribution! Great thread and thank you for putting all the time into this and sharing with us.
I’ve got the SC64 LE left and then I’ll have been through all my flashlights with switching drivers 
Problem is PWM affects LED efficiency so I would need compare lm/W instead of just the driver efficiency, it would be interesting but a bit more complicated.
Thanks.
Yeah,it is more complicated. Great work so far.
I agree with the others. Thanks for this. And looking forward to the sc64 LE
Zebralight SC64c LE
Uses the TLV62085, a 3A synchronous buck converter, 2.4 MHz. I thought the driver would be 3A but it’s 2.8A instead.
Coilcraft XEL 4020 1uH inductor, 14.6 mΩ
2x2mm RPP PFET, 13.5~15mΩ.
Nice job!
Noctigon KR4 12V 2A :
It uses the MP3429, 600kHz synchronous boost converter with integrated switches, ~12V output.
6030 1.5uH inductor, 11.5mΩ (Haukkeli’s measurement)
RPP PFET WSD20L120DN56, 2.5~3.5mΩ
I also measured it at 2.54A after increasing Vsense from 40mV to 50.8mV.
I don’t understand any of these numbers. When do you know it’s good/great/amazing?
Higher efficiency is better, it means longer runtimes and less heat to dissipate, so higher sustained output on temperature regulated lights.
On a KR4/D4v2 I would assume the sustained output is around 0.5~0.8A (5.5~10W) depending on the LEDs, maybe up to 1A with low CRI cool white LEDs(12W), at these output level the efficiency is >93.5% which is very good.
At maximum stock output (2A-25W) and low battery level the efficiency drops to 88.5% with is okay and 3.2W power dissipated which is manageable.
After modification to 2.5A-32W (in red) the efficiency drops and the power dissipated nearly double with a low battery. It will still work but may stepdown quickly. It’s understandable they stayed at 2A with the inductor chosen.
If they had used a lower resistance inductor of the same size with 1uH inductance instead of 1.5uH, (lower inductance means lower resistance), then I guess the efficiency at 2.5A would be similar to what it is at 2A now.
This would be an easy upgrade for Emisar/Noctigon to do without having to redesign their driver for a larger inductor.
^ Super info, thefreeman!
Sure looks like the data you collected for the Zebralight SC64c LE is very positive. Of course that’s with a modded 519a swap. I have to wonder how close the data is to the original LH351D. Is it the most efficient light you’ve tested thus far?
Are the data line items in red on the KR4 to highlight a power loss you deem below average or acceptable for the given battery charge level?
For the SC64 I measured with a 519A because that’s what I had mounted on the heatsink, the drivers are all tested outside the flashlight, on the bench, with high precision current sensing shunt to measure the input and output current, it would be difficult to test in the flashlight (if that’s what you were assuming). The results with a LH351D as test LED wouldn’t be really different.
The red was just to mean that it’s not the stock output.
Thanks man. It makes more sense with your explanation. Makes me feel sad for the lone Acebeam you tested and happy that I’m getting some more Bobralights.
Good to know, thanks!
Curious to know your thoughts about the design of Firefly Lite’s “High efficiency 6A constant current buck driver plus FET Turbo,” and what you’d suggest for improvements if any?
Pros :
Cons :
Personally I don’t really like unregulated output so I haven’t made any of these types of drivers.
An improvement would be to get smooth dimming from turbo. The problem is that they can’t be ON at the same time, it’s not like linear+FET where the FET channel is in parallel to the linear channel, and we don’t know when to switch from the FET channel to the regulated one since the output current is unknown in direct drive,
It should be possible to read the FET current with the sense resistor if it was wired to an ADC pin and switch to the regulated channel when the average direct driver current reaches the max regulated current. But that’s for the code guys to do as I don’t have any programing skills.
Yes. I’d personally rather have a low resistance high efficiency buck driver over a FET driver at this point.
At this point, I’d rather have 6A buck + 12A linear.
The firmware would be weird, but it would work.
No problem doing buck+linear firmware (Anduril) wise, and that would solve the abrupt stepdown. But it’s an additional regulated channels with all the components that come with it.
Linear drivers can be problematic when there are a lot of LEDs (very low VF), as the power dissipated in the FET can be significant, it needs to be able to withstand it.
The linear channel current could be higher like 20A and it would have direct drive like output.
^ Thanks for the explanation! Given the component sourcing problem, I expect they won’t change revise the E12R in the near term… assuming it’s something on the books to address.
Well they are apparently releasing an updated version but I don’t know the details.
I could really go for high-output Buck drivers with 519A these days
shame about inductor size limitations