Direct vs. Regulated Drivers ?

[Bob96]

I have lights with regulated drivers. They appear to have the same brightness reguardless of size & number of batteries as long as within the voltage limits of the driver. The larger, or more, batterys do give longer runtimes though
How does a direct driver work? Does it just pull as many amps as the LED can use from the batteries? As cell size increased say from a 16340 < 18650 < 26500 < 26650 will a high power LED pull more amps and be brighter? Just wondering the pros & cons between Direct & Regulated circuits?

 

[alpg88]

there is no such thig as direct driver, direct drive is actually absence of any driver
direct drive is cheap easy way to build a light, not always the best, actually even dd you still wanna use a resistor or a diode with right resistance to limit amps, my latest build was dd 3 cell p7, p7 needs 3.6v and 1.2x3=3.6 so it looks like perfect solution, voltage wise it is but on fresh cells p7 was pulling 3.5 amp, too much for the led, so i had to use 2 diodes in series (had to work with what was available, and used dmm to figure resistance needed), to bring amps to needed range. the light would dim gradually as cells discharged, regulated ones don't do it, at least not as much.
so to answer your question, dd has advantage of being cheap, easy, and reliable.(less parts to brake) also when v of the batteries and the led match, that driver might not work right, they need voltage difference to work ,at least most of drivers i had were like that.
there is however a driver sold by member here that works, i used it in my 3xp7 build that was powered by 6x18650,3s2p voltage wise i had perfect match(3p7 in series and 3 li ion cells in series), but amps had to be regulated.
regulated led is better way to build a light 95% of the times.

 

[Bob96]

Good informative answer. I knew that over-voltage can burn out things. I thought amps were just there to be used as needed? I figured that if voltage was correct more potential amps would be a good thing like increased run times.

 

[John_Galt]

There's nos such thing as a "direct" driver. Usually when someone refers to direct-drive in a light, they're referring to the absence of a driver or regulator.

Most direct driven lights use battery combinations, such as 1x Li-ion, 3x Ni-MH, and 3-4x alkaline AA/AAA. Basically, the light source is connected to one or more resistors, to limit current draw from a battery pack (usually to extend runtime, but also to limit current to the emitter to keep the emitter from frying from too much current).

An example of a direct driven light is any common incandescent based light. Basically you have a light source, and batteries. With incandescents, you can tailor bulbs to handle certain amounts of current and voltage, but with LED's, you really can't (as far as voltage is concerned). Most LED's have a rather odd forward voltage ( the energy it takes to light an LED up, as LED's are current driven, not voltage driven, as with incand.) of ~3.7v.

Most battery combinations will not meet this forward voltage, they will be either above or below it, thus necessitating the need for resistors, or drivers. Now, it is easy to fudge a little bit on the voltage front, which is why manufacturers lije Coast/LEDLenser use combinations of 3-4 ALKALINE ONLY batteries in their flashlights. The internal resistance of the alkaline cells automatically limits the current that can be drawn from them, and when pulling anything over 100mA, the voltage sag is bad enough to limit the voltage to the LED, as well...

A lot of people like to do direct drive mods with Li-ion batteries, as the voltage of Li-ions is nominally 3.6v, but when charged, ~4.2v. And good quality Li-ions can handle high current draws without damage or negative side-effects. Which is why they are very popular in high power P7/MC-E/SST 50/90 mods.

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Both direct-driven and regulated lights have their individual pro's and con's. One may be appropriate in one situation, and innapropriate in another.


Generally speaking, most direct-driven light state run-time figures from the original output to too-dim-to-use. Most regulated lights state runtime figures from original brightness, to the 50% mark.