Great read you guys!
great read. if only I had read this a few months ago. would have saved me a lot of time :bigsmile:
What a great wealth of information. Thanks for taking the time to compile it and share it with us who are light challenged. 
Carl
Excellent resource. 
Thank you lagman for your great explanation!! I’m new to this forum and have been searching for a completed guide about flashlight driver but I haven’t found yet.
Could you draw simple circuit diagrams of some popular drivers and explain its components/ how it’s work…?
I have some knowledge in electrical physics but not in electronic components, the driver boards are too complicated to me :person_facepalming:
So will a linear regulator have better efficiency when using a IFR (LiFePO4) cell than ICR,IMR or INR since it is about 3.2V nominal?
A boost converter (step-up converter) is a DC-to-DC power converter that steps up voltage (while stepping down current) from its input (supply) to its output (load). Step-up switching converters, also called boost switching regulators, provide a higher voltage output than the input voltage. The output voltage is regulated, as long as the power draw is within the output power specification of the circuit. Many of our step-up switching regulators are designed for driving strings of LEDs.
If your step-up/boost application is not power intensive (IOUT < 0.5A), you may prefer a different power conversion technology for boost applications.
I would like to build a quad for solarforce with an extension tube. What driver can I use? Is it possible? Planning on buying my parts from mtn. Thank you.
What size driver would you need? Is it a 3volt LED quad your building? Is it for a P60 drop-in type (17mm driver)?
You can get a 2S 3volt 17mm driver @ 5.5amps as long as you have 6+mm of clearance for the Coil Craft Inductor from RMM.
@joker145, use a buck driver.
This will allow for fully regulated brightness with 2S over the course of the entire runtime.
Yes 3 volt led, and a P60 drop in that I bought from Kiriba-ru
Would like to use nichia led.
Thank you, also I can use one cell if needed?
The driver I linked is the one you want. You have to go with the Coil Craft Inductor to get 5.5amps 3amps is Max for the standard inductor.
does a boost driver at 9Amps Turbo, go into direct drive?.
am I wrong ?.
A boost driver cannot go into direct drive.
Few words about linguistic, psychology and marketing
In pure electronics, word “buck” and “boost” converters have no emotional content, simple engineering: must lower voltage, must increase voltage.
In flashlight area, “boost” has totally wrong build associations, to be “uber-flashlight” , be better by mere existence.
Every word catched in hands of marketers is lost for precise communication.
BTW increasing voltage isn’t for free. Perpetuum mobile does not exist.
This is exchange bigger current , small voltage to opposite (and loses in device)
“Constant current for much of the discharge of the battery”
So when is the current constant and when it’s not?
Moon Meteor Storm with parallel cells seems to have linear driver but the current with fully charged cells is 1.3A when paired with SST-20 (originally XML2) and then steadily drops.
Just found this posting. Informative and well-explained. Thanks.
1 Thank
Literally never seen that. If anything, buck drivers are generally regarded as more efficient, and FET drivers more powerful, on average, even though for each of those it depends more on design than anything else. Zebralights use boost drivers and are the most efficient lights around, but in general boost is IMO not implicitly better. Are you thinking of “turbo”? (i.e. a high, thermally unsustainable brightness, often outside the usual levels)
linear drivers are usually constant-current - LEDs receive the same current all the time (which depends on the LEDs, could be between 1 and 12+A), and brightness is controlled through changing the voltage.
I’m more used to opamp-based linears, but as I understand it, the 7135 chip will allow constant-current until the battery is very low, as eventually, as the battery voltage drops, current will increase to compensate, leading to more current to the LED. Too much voltage or current will destroy an LED, so this could theoretically be bad with a fragile LED and too many stacked 7135s.
Not sure what Moon Meteor Storm is, but I’d like to hear more.
Current will not increase to compensate.
Linear drivers such as 7135 always have the same current at the input and the output, unlike boost or buck converters.
As you said, the current is regulated to be constant regardless of battery voltage.
If the led needs 3v at the set current, the excess voltage will be dissipated in the linear driver. That way, the led always receives 3v and constant current.