Although this is highly mathematic, you see how the curve changes in the watts calculations while linear in the input values. Not only that, the cell’s internal resistance will barely hold 4V with the best of cells for only a short period of time. At lower current draws, this will be closer to the 4.2V than at higher draws for longer periods of time. At 5 amps, I suspect this driver will be at direct drive into a single emitter within minutes unless multiple IMR parallel cells are used. Only the FET’s internal Vf losses will be added to the heat source.
So the primary yield will be in a light that might need 5A for Turbo level but will be used the majority of the time in a lower capacity, which will gain longer net run times at the lower end by almost 2X, right? A general purpose light or a walking light, seems ideal for that.
Trying to adapt my way of thinking from Absolute Max to...well, whatever else someone would want to use a light for. ;)
My wife and I were walking last night and she had her 501B with an XP-G and I had the SK68. We were having fun pointing at building to find that the Sk68 was great for lighting up distant signs where the 501B scattered before it got there. By the time we got home, the sk68 was still really cool and lit up the path just fine… but my wife, a non-flash-a-holic (or closet flashy?) was complaining of the 501B getting warm. I think a conservative “normal” mode is a good thing for unsuspecting users.
First,I apologize if I didn't answer to some questions(thread and PM),I'll do that ASAP.
@Texas , if you want to drive 2 xm-l2s at 5Amps,you can use expander board. Order PCBs from OHSpark,you'll need MOSFET and sense resistor.You can use sense resistor from LD-1 PCB since it must be removed,actually if you have hot air station and skills(or you have a friend who has that),you can "transplant" even MOSFET from LD-1 board,because if you use expander pcb,mosfet on LD-1 doesn't have any function,but it's impossible to remove it without hot air,so you can leave it on board and buy other MOSFET for expander board.
It's interesting that this driver is actually less efficient on all currents compared to direct drive pwm DD type.
But "here's the whole picture": imagine that you have two identical lights,one with LD-1,other with PWM DD driver,and both run at x.xx Amps and with identical battery.
Total (average) power consumed from battery is Vbatt*I,so total dissipated power is the same both lights.But, in case of pwm DD driver VledDD~Vbatt,so ALL power is dissipated in LED: VledDD*I (well,let's say that resistance of DD driver is negligible so dissipated power is ~0),while LD-1 takes (Vbatt-VledLD)*I part of power and dissipates that in heat,and LED only has to dissipate VledLD*I.
Note that total flashlight heat is the same because:
So,one of good things that LD-1 does is that takes that extra heat on itself("sacrifice" itself),and this way helps LED by reducing its heat dissipation.And it's much better idea to dissipate that extra heat in mosfet,than in those tiny gold wires,sensitive GaN die and phosphor(LEDs efficiency drop at high current proves that).
So when you combine facts that LEDs are much more efficient on lower currents,and that linear drive reduces heat generated in LED ,overall lm/W efficiency is better with linear drive.
The DD is a “convergence” between battery resistance and LED current. The cell itself becomes the passive R-device and I am sure it generates heat accordingly. But it has a better heat dissipating mass and surface area than the little FET.
I guess there really is no better driver than one with a true voltage converter with a current sense to determine output. Of course, by its very nature, this is a pulsed output set by the frequency of the switching control circuit.
We are fortunate enough to have reached the point of designing to “convergence” in single emitter, single cell (and parallel source) lights. but the advent of the 6V MT-G2 has asked for more. A 1.2-2.4V overhead is something to contend with when using 2 cells. Or better yet, a robust boost driver.
I like the LD-1 as an elegant solution including the innovative coding on the firmware. With all the new e-switch host offerings out there, it is a great alternative. I would want one just to have one even though I have no e-switch hosts (yet).
Just curious… how hard is to isolate the low voltage components from the power circuit in the LD-1? I would think you need a low power step-down converter to drive the logic circuit and a low power step-up converter to drive the output up to drive the FET gate pin. The step-up may even be do-able with a divider network.
Got the proto still in a Y3, ordered 3. Look'n forward to get 1 or 2 in a e-switch EDC. Like'n the ZY-T11 clone (UltraFire) as of late, so one is destined there, probably a SupFire L5, and not sure yet on the third.
Led4power, please take an unbiased look at your driver.
As LED- and LED+ are not marked, and neither the sales thread nor this thread give any hint about it: Where would you - quite intuitively - solder the LED wires to…
Solution is only to be found in the preliminary thread… you might update the Connection Diagram section.
just imagine my immediate reaction when I connected the wires, the LED, the shunt, the battery, and then…
nothing…
took me some minutes to figure out what went wrong
but it seems the driver has survived this, all 3 show similar behaviour
it might just be helpful to prevent others from doing the same
just a theoretical question: what if someone did a horrible job soldering the eswitch negative connection? Would the resulting solder bridges fry anything permanently?
And what if you just bridged the sense resistor? would you loose all modes?
Would LifePo’s come into play with their lower charge?
This is in thinking with an MT-G2 needing 6V and then some, would a pair of 3.2V LifePo cells with their closer total Voltage work well with this driver? Then the large overhead would not be in place.
I’m looking at a pair of LifePo4 cells with the capability of 70A continuous discharge, 120A pulse, 2500mAh capacity. Capacity isn’t good but they’d be 6.4V to an MT-G2 that also uses about that at around 7A draw. So would this work at 5A to the MT-G2 without creating excessive heat being as how the overhead is so low?
Is this a good driver for the Y3 Tom? I like the buck on the Y3 because it does support up to 3 batteries. I’ll have to order 3 if you have a good experience with this. I was going to mess with the 4 color led but using a mini switch on the back of the driver itself.
Fully charged li-fepo4 are 3.6x2=7.2V volts,too high for this driver.
There is one possible solution,if you really want use LD-1 with more than one cell,it's op-amp buffered voltage divider:
This circuit behaves like normal resistive divider with very low R1 and R2 resistors(much lower output impedance,and that means you can use high value-low current consumption R1 and R2 resistors,and still have load independent output voltage).
Input is connected to battery pack (2x li-ion),output(1/2Vin if R1=R2) is connected to LD-1 +Vcc.
But,this gets quite complicated,you need LD-1+expander board+another small pcb for upper schematic.
Sorry bout that…