Convoy S2+ "10%" Mode

EDCba · 2018-11-04T12:19:38.000Z

My S2+ is the 7135*4 output current 1400mA, (mode option 4)10%low—–100%high—strobe.

I just managed to do some measurements. On high it draws 1.4 A, exactly as designed. But on low it only draws 0.076 A, which is closer to 5% than 10. Brightness is the same - mine is uncalibrated but low is 5 the lux of high. Has anyone else with 10% in their UI done measurements? Is it actually 10%? I don’t mind, just finding it interesting (and learning to use my meters).

Lighted tailcap draws 8 mA btw.

jr2017 · 2018-11-05T00:44:22.000Z

The current is limited by pulse-width-modulation, or PWM.

It’s not drawing 140mA 100% of the time. Instead, it’s drawing 1.4A 10% of the time, and 0mA 90% of the time.

There are a few reasons the driver might not get it perfect when using this technique to aim for 10%. But another issue is that not all equipment can accurately measure this, or it measures somehow but doesn’t average/report the way you expect it to.

EDCba · 2018-11-05T01:49:49.000Z

jr2017:

The current is limited by pulse-width-modulation, or PWM.

It’s not drawing 140mA 100% of the time. Instead, it’s drawing 1.4A 10% of the time, and 0mA 90% of the time.

There are a few reasons the driver might not get it perfect when using this technique to aim for 10%. But another issue is that not all equipment can accurately measure this, or it measures somehow but doesn’t average/report the way you expect it to.

Yes I thought my meters might be measuring instantaneously or time averaged or some combination. But maukka’s PWM measurements show it doesn’t fluctuate between 0% and 100%: Convoy S2+ measurements (7135*8 3B) | Candle Power Flashlight Forum

It’s an odd coincidence that mine has half the chips of the 8*7135, and draws half the current. Could the driver be directing power to chips that aren’t there?

Barkuti · 2018-11-05T03:27:55.000Z

7135 regulators do not like to be fast PWMed, their slow turn on and turn off times leads to lowered effective output most notably on low duty cycle modes. This Pratik Panda AMC7135 PWM LED control – works? article gives a good hint, though I would thank if someone were to explain me how do the article's given figures fit with the provided graphs:

Is this 10% duty cycle at ≈2KHz?

And this looks like ≈36% duty cycle at 30.864KHz… ?

Cheers :-)