Driver Types, Please Help

Last One Left · Feb 22, 2011

Hey everyone i need to know how different drivers work..
I know that some drivers need voltage to work so therefore the output voltage is lower that the input..can someone please tell me which drivers do this..
I know the Lm317 driver needs voltage to work so therefore its output is lower than the input..but what about the flexdrive, microdrive and rckstr drivers..
Also i notice Jib77 selling these "LM1117 Based Linear Driver - 1.3A Fixed", are these good for 445nm diodes? and if so, can it work well off of one 18650 battery, or will i need two batteries to accommodate the voltage being used by the driver itself..
What are the benefits of using one that take voltage and one that doesnt? Please help me with these questions..

bluuray · Feb 22, 2011

i dont understand you but there are two different types of drivers ... linear and boost drivers
linear = lm317 and rckstr which can will work with 2 cells ( lithium ) or more
and boost = flex ( there are more ) and they can work with 1 cell , they " boost up" the voltage to what you need for your diode to work
and you can find all this and more by SEARCHING

and NO the jibdrive wont work with 1 cell! he clearly says that

Coherent Light · Feb 22, 2011

4 types actually if you count direct drive.

1 = Linear Driver
2 = Boost Driver
3 = Boost/Buck Driver
4 = Direct Drive...not recommended.

rhd · Feb 22, 2011

Some that come to mind. I think I have these in the right place.

1 = Linear (rckstr, Groovedriver, Jib77's, DIY LM317 or LM1117, $1.99 DX thingy, lots of assorted Aixiz, OdicForce, and noname eBay drivers)

2 = Boost (Microboost, $4 DX and Kai LED driver, $14.99 O-Like driver, OdicForce OFL74 and OFL122)

3 = Boost/Buck (Flexdrive, others?)

Last One Left · Feb 22, 2011

Thanks guys..can u explain the difference between boost and boost/buck..
Also is anyone better than the other? Or all are best at different type of builds..thank you..

rhd · Feb 22, 2011

Boost can raise the voltage higher than the voltage supplied by the batteries.

Boost/buck can do this too, but it can also LOWER the voltage supplied by the batteries (in case you're supplying more voltage than the diode needs)

It all depends on your build/host. How many batteries does the host fit, etc.

anselm · Feb 22, 2011

There's also the matter of efficiency.

Most linear drives are somewhat wasteful, in the way that extra voltage is simply
dissipated as heat and not taken advantage of.

A properly designed buck driver will give better runtimes.

From what I've read, the FlexDrive is a very efficient boost driver, whereas others
might be pulling way more mAs from the battery than they provide on the output.

rhd · Feb 22, 2011

anselm said:
Most linear drives are somewhat wasteful, in the way that extra voltage is simply dissipated as heat and not taken advantage of.

A properly designed buck driver will give better runtimes.

Aren't they the same thing? Doesn't buck driver = linear driver?

I don't know this for certain, so it's a legit question, I'm not challenging your knowledge

I thought "buck" meant it was a driver that cut down excessive input voltage. In that sense, it's the same thing we usually label a "linear" driver, right?

chipdouglas · Feb 22, 2011

something i always tell people is get a driver based on your host. if your host can only take enough batts to get to 3.7v then go boost, buck/boost. if you can get to over 7.2 then you can go with linear. but if you only care about efficiency then you will probably need to plan your host around your driver (boost)

anselm · Feb 22, 2011

@rhd
It's a good thing you challenge my knowledge, keeps me from talking out of my ass, like
some people like to do...

wikipedia said:
The simplest way to reduce the voltage of a DC supply is to use a linear regulator (such as a 7805), but linear regulators waste energy as they operate by bleeding off excess power as heat. Buck converters, on the other hand, can be remarkably efficient (easily up to 95% for integrated circuits), making them useful for tasks such as converting the 12–24 V typical battery voltage in a laptop down to the few volts needed by the processor.

Buck converter - Wikipedia, the free encyclopedia

rhd · Feb 22, 2011

Alrighty

So do we actually have any pure buck drivers? (here - used as laser drivers)

To my knowledge, Groove Drivers, Rckstr, and Jib77's LM1117 would all fall under the linear classification then, not the buck driver category. Correct?

chipdouglas · Feb 23, 2011

as far as i know, in this hobby, a pure buck type drive isnt in demand. excess voltage isn't a problem with all the battery and host configurations available.

Last One Left · Feb 23, 2011

Thanks for all this information guys..This is why i decided to open this thread..yeah according to the first reply, the guys said i should search for my answers but the truth is there is hardly any answers to these questions and sometimes one thread contradicts the other..here we can discuss these question to the point..

Anyways, from these information im thinking that a boost/buck driver is kinda like a combination of a linear plus a boost driver so im thinking that its the perfect driver..in the sense, is voltage is to high it will break it down and if it is to low it will boost it..sounds like a all round winner..is this so?
Are there any boost/buck drivers easily available? what are the brands?

Coherent Light · Feb 23, 2011

The MicroFlex Driver from Dr. Lava is the only Boost/Buck Driver I'm familiar with, but supposedly Dr. Lava is out so you'll have to search here and on Ebay to find one.

Lumin · Feb 23, 2011

most DC-DC converters that I've seen are optimized for certain power ranges... how much power do you need? The farther you get from optimal the less efficiently your converter will convert, and wasted energy is usually wasted in the form of heat...
I THINK that a buck / boost converter traditionally requires a tad more overhead for being able to go both ways, and is as such a little less efficient than an application-specific buck or boost.
Also, there's a few ways you can go about converting dc levels, some are intrinsically more efficient than others... if your power in & out requirements are fixed you can go with more efficient methods....

If I'm wrong about anything I apologize, I'm not an electrical engineer and all my knowledge is the result of experiments and datasheet readings.

A good place to start might be:
DC-to-DC converter - Wikipedia, the free encyclopedia

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