Test/Review: LD-1 5A PWM-less driver - led4power (Tests in aYezl Y3)

I’ve been waiting for this. Get busy!

that package said authorized personnel only… can I see your ID please?

OSHpark do that all time,at least in my case.They trim 20mils from edge on all copper layers.

Ah, that explains why on some boards I see the top copper layer actually extending beyond the milling layer…to compensate for that cutoff by the manufacturers…thank led4power, can’t wait to see these hit production! :slight_smile:

Very interesting design, and I really like how you did the “stars” solder bridge locations…very cool!

OP update added - 07/23 dated, round #1: amps measured across all std modes.

I always made the copper bigger than milling because of laziness so I never had this problems…I also did some where the milling was in the middle of through holes(thought that would increase GND contact) and they milled perfectly through it.

Is this just a newer phenomenon from Oshpark, did I only had luck or was it the point that I made the copper ring bigger than milling the point?

Request for a run time comparison:
Same cell charged to same voltage
Match current output current between this driver and a Qlite 3A w/ one extra chip and pwm set to 1.1A.
Plot current vs voltage and time when each falls out of regulation.
Plot end of charge for both and calculate efficiency.
If you can get this driver up to 4A then add chips to a Qlite to match and then run the test.

It is a bit unfair to compare them at same current, the LD-1 will be brighter than the pwm driver.

If you compared it to a 5A pwm driver, then the lower settings will be about 50% brighter.

That’s a good point… perhaps if someone does this test, it should be compared at the same lumen level instead of the same current?

(seems like the current would probably not be a very interesting test anyway, since any two devices at the same current will tend to have similar runtimes regardless of what they actually do with the power)

Except that LD-1 can maintain full output to a lower battery voltage.

Agreed, I’m mostly interested in independent confirmation of efficiency differential at equivalent lower mode output modes.

As I wrote above, you get about 50% extra brightness compared to a 5A pwm driver. This is because the led has higher efficiency at lower currents.

You could also use a triple XPG2 as the test LED, to mostly avoid the high-Vf-limiting-max-current issue.

HKJ, I was agreeing that the comparison should be based on lumen output rather than just current but that does make for a more complicated test.

I also plan to do the comparison based on light output, but I’ve not receive my sample yet.

You can do a fairly good estimate without doing the test, but if you have a 5A pwm driver it is not that difficult to setup:

Mount the led and a luxmeter at some fixed position (A luxmeter with PC logging is preferred).

Run the test with the pwm driver.

Use the LD-1 in ramp mode and adjust it to same brightness on luxmeter.

Replace battery used for adjustment with fresh battery and run the test again.

It could be interesting to do, but I do not have a 5A pwm driver for it.

Hhmm, gotta check my driver stock. I could build up a Nanjg to ~5A, but I do have this driver from Richard: http://www.mtnelectronics.com/opencart/index.php?route=product/product&path=67&product_id=214, but it's 2-3 cells. Didn't realize you gained 50% over a PWM mode - I knew it was better, but not by that much - cool!

That is because the XM-L2 has low efficiency at 5A.

I wonder what the efficiency difference might be at 1.4A, or 1.5A, or 1.9A.

The 1.9A light I just put together with a Nichia 219B is really nice, and the PWM is fast enough it looks almost the same as full current control… but the runtime won’t be as long. I never really use it above 800mA or so (average), so I could reduce its overall power to increase efficiency, but it’s nice having a turbo mode once in a while. The higher power is also nice for strobes, because a 0.3ms pulse looks brighter at 1.9A than it would at 1.4A.

For a bike tail light, I went with 700mA because djozz’s measurements show that as more efficient than 350mA or 1050mA on a red XP-E2. I don’t need it that bright, but it should increase the overall runtime at the same brightness levels, even when using PWM.

The efficiency difference is because a 50% (or whatever) constant current requires a much lower Vf, compared to a PWM'ed 50% which is full current for half the time and none for half the time (assuming both drivers do the same current at 100%). The average current might be the same for both drivers but the voltage isn't and the total power used comes from both volts & amps.