QLite Regulation vs. other 17mm Drivers

iamlucky13

Flashlight Enthusiast
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Oct 11, 2016
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Short summary: are there better regulated budget drivers than QLite, or a way to get better regulation from QLite?

Why I ask:

I'm thinking of building a couple car glovebox lights with the Convoy hosts Mountain Electronics sells. Just because I want to compare them, one would be a Nichia 219C light, and the other a 90 CRI Cree XP-L2 in the same CCT.

I'm planning on single emitter lights (no FET needed), and looking 3-4 widely spaced modes and the consistent performance of a regulated driver. I'm leaning away from a true moonlight for this use, but a minimum in the 1-5 lumen range would be nice.

I might keep half-charged batteries in them to prolong battery longevity in a hot car, as raw runtime probably won't be an issue. This increases the appeal of good regulation for consistent performance.

At a glance, the QLite driver looks like a solid choice as far as firmware and mode options and output goes, and the price is great.

However, I noticed HKJ has tested it and had some surprising findings. Hi mode looks fine - holding regulation to 3.6V, and dropping to half output at 3.2V. It seems pretty reasonable for a $4 component the size of a dime capable of 3 Amps to need ~0.6V of overhead to operate at its peak.

The lower modes are what give me pause. At 25%, it falls out of regulation all the way up at 4V, and at 2% it shows no regulation, and in both cases drops to half output at about 3.4V. This was a big surprise, as I'm used to seeing lights have no trouble regulating their low modes for nearly the whole battery life.

HKJ suggests the high frequency PWM (16.5 kHz) is the cause, as the 7135's don't appear to fully turn on in these short cycles, which his oscilloscope data shows.

In contrast, the D4 uses a similar 15.6 kHz PWM for it's 7135, yet seems to show excellent regulation on lower levels.

The stock Convoy S2+ driver, which also has 8 x 7135 regulators, seems to show the same behavior in 33% mode at 4.5 kHz in Maukka's test, and in fact visually appears to be the same hardware.

Muddying the waters further, another review of a high end Okluma with a QLite driver only includes data on high mode, but it drops to 50% on a timed thermal control stepdown, and regulates that 50% level almost perfectly.

I can't find similar information on the Moonlight Special or the H17F, but given their similarities, I'm expecting similar results. The H17F seems like overkill for this application anyways.

Does anybody have further info about this? Is it perhaps only certain firmware that experiences difficulty regulating the low modes on QLite? Okluma doesn't seem to have this issue on the same driver, nor did Emisar when using the same regulator.

Are there other 17mm drivers I should consider?

For what it's worth, this isn't a deal breaker. If there's nothing easily available with similar features but better regulation than QLite, it does look like it has the basic functions I need, and offers mode options I'd prefer over the stock Convoy driver.
 
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