It's size is relatively small (~9x12mm).
Side A



Side B






As some of you already know it's a constant voltage driver for Red/IR Laser diodes.
To set the current you must rely on the current/voltage characteristics of the diodes.

This is not that easy as the temperature is pretty much a factor which you don't want to have to deal with when setting your current.
This is why I prefer constant current to constant voltage output.

I don't have a spare laser diode to torture so I used my test load as a ..um.. a LOAD!


I made a video showing how the current varies at a constant voltage output with temperature.

At the beginning of the video I am showing a constant current buck driver set at 0.5A for reference. (the voltage is stable at 2.75V so I set the voltage of the Inferno to this)

Next I hook up the inferno and see what current will I get at 2.75V.
As you can see as the driver and load heat up the current rises.
If the temp decreases the current drops as well. While at constant current the current is stable over wide temperature range.

Now although it's been researched you can't be sure what current the diode will draw at a specific voltage. Efficiency varies with each diode and won't be a constant.

It's not a big difference after 10minutes of use 506mA vs 516mA on a heated load. But on a chilled load the current is almost 100mA less.
Maybe that's acceptable for Reds as for what this driver is intended.


Never the less efficiency is great - ~95% when outputing 2.75V@~0.5A and input is 3.6V/~0.4A

I like the driver a lot - it's small,efficient and adjustable(2.8V-3.12V on mine).
Mine could output slightly above 1A.
It has a low battery output for a LED (see the video),
Nice work!

BUT I wouldn't rely on it for any of my laser builds. Simply because I don't find the constant voltage a preferable choice.
I think that with constant current the diode will live a lot longer (at safe currents of course )



Thanks for the driver. HTV let me know when you need something. I will be glad to help!

Nice review! good to see points proven in theory and in practice! +1

There were a lot of heated arguments about choosing voltage for LD’s supply in due time. And all the same, we had chosen voltage. Now, voltage makes rustle and in your forum. Same story was always. One people cite arguments in favor of voltage’s supply; corroborate its by diagrams, theory and practice. Another people fear to use original solution because of conservative considerations.

Yes, current supply prefer for semiconductor element because it is main parameter. But, red LD has sufficiently soft and stable current-voltage characteristic. Voltage supply’s scheme is simplest. It hasn’t typical problems for current supply: poor contact; remnant charge in output capacitor (it will kill LD by carelessly using); isolate case of LD from ground; complication with current regulation; creating soft start; low efficiency because of current sensor (resistor); off-scale reading of error signal, that is a cause for unstable work of any chips; etc. There are some imperfections, but advantages of supply in original modes are more than compensated in portative solutions. Current supply is better for stationary solutions because of its universality at least.

Unfortunately, this type of supply doesn’t for all types of LDs. Red LD is pleasant exception to the rule. Its thermo stable and soft current-voltage characteristic enables to use voltage supply. Because of it, we can obtain pleasant bonuses:
- High efficiency.
- High thermo stability (yes, current varies in some range, but optic power varies in larger range and in reverse direction).
- High frost resistance. Cold LD radiates with more efficiency, but it consumes lower current under voltage supply. Under that, crystal is warmed up quick and works in standard mode. We live in cold region, but it isn’t a difficulty for normal work our lasers with this driver. Quite the contrary.
- Soft start makes LD’s life easier and looks pleasant. It turns on quick but soft (doesn’t beat on eyes).

History of this driver started more, than 2 year ago. This driver became a classic scheme at our forum long time ago. Look at laser pointers with red LD at our forum, this driver is in each of them. What were our first schemes? Those were bulky irons with LM317 or other current supplies that always have some problems. Every now and then LD was killed because of poor contact; every now and then LD was killed because of frost; every now and then hard to choose accumulators; every now and then heat in driver more than in collimator. Last version of this driver is circle with 10mm of diameter. However, there are slots for LD's pins in middle of board. The driver is not only stable and efficient, but it is very compact. This is all owing to feedback by voltage.
By the way, question of driver’s efficiency face sharply not because of accumulator’s capacity. It is so because of heating which influences at driver’s dimensions. Difference in 5% influences at driver’s heating more than 2 times when its efficiency is 90%. It is actual problem for heat generating device like our lasers.

There is another striking example of LD's original supply. It is driver Indigo, where I use feedbacks by current and voltage at the same time. Violet LDs can’t be supplied by voltage. They have very unstable although soft current-voltage characteristic (blue LD’s have more bad one). But, we can use this effect as thermo sensor that measures LD’s temperature in its crystal. At the same time, we can use it as potentiometer that endeavors to keep LD’s optic power as stable as can. It is simple at practice, current’s drift is in range of 10mA (in case of PHR). Also, it gives some bonus too:
- Reduce voltage dips at current sensing resistor more than 2 times.
- Appear a possibility to add soft start.
- Converter works easier because of error signal of feedback goes off-scale less (It more actual for converters from line of TPS630XX).

In general, don’t be conservators in LD's supply task. For example, in theory pulse supply of LD can decrease temperature difference between active environment and crystal’s base. That fact allow to get more middle power from LD, etc.

Oh look - those wonderful "hobbi" folds copied my IRON 4D driver design (here) for an on-lead circular PCB for reds:
http://www.ebay.ca/itm/660nm-red-las...ht_1174wt_1396

Granted, they didn't copy the most important part - making it a proper CONSTANT CURRENT driver

But it's nice to know that Russia is a fan....

Oh look - those wonderful "hobbi" folks copied my IRON 4D driver design (here) for an on-lead circular PCB for reds:
660nm red laser diode driver (HTV Inferno 2.2) | eBay

Granted, they didn't copy the most important part - making it a proper CONSTANT CURRENT driver

But it's nice to know that Russia is a fan....

PS: Thank you to all those who brought this to my attention.

Seriously.. And how was the debate going on with their driver being very specific to the characteristics of the diode and all that rats bs..

It is our own scheme. This driver was created around year ago.

By the way, we noticed that someone from LPF use our ideas in his drivers. Because of that, we didn’t publish own new schemes on our forum for free access anymore.

The driver schematic was. Your concept of "on-lead" mounting it (as far as I'm aware) was a revision that happened this month. Version "2.12".

"By the way, we noticed that someone from LPF use our ideas in his drivers."

I doubt that. Nobody here is interested in building voltage regulators. Even the newest LPF-ers know not to take this approach

Yep, I agree with RHD. The "On-lead" concept was never seen before the 4D drive, as far as I am aware. And can you show some proof of the second statement? Which driver resembles yours exactly? It's good to bring out the facts when accusing someone.. Otherwise is just empty words.....

Our community used this driver from 08/05/2010: http://forum.hobbi.tv/showthread.php?t=290

It is your opinion. We know that it is one of best drivers for red LD. It passed test by time.

About the on-lead design: That looks legit. You're right, I'm wrong. Sorry to have mistakenly called you out for steeling something that it looks like you actually had first.

About voltage regulating being wrong: Well, we've had that debate already. The only argument in favor of voltage regulation is that the drivers are simpler to make. So are cars without airbags. Most of us would still rather be safe and complicated than unsafe and simple

Compare schemes and its publishing dates: http://forum.hobbi.tv/showthread.php?p=6203#post6203 and TPS63020 Based Driver.

@RHD....

They even posted pics of that "on-lead" round driver on
this Forum first back in Dec 29 2011 and you commented
on it.
It seems they were also the first to use the Mosfet circuit
input protection as well...

NCP1529 Driver For RED LASER DIODES - What do you think?

Your "on-lead" Thread was one months later on Jan 28 2012..

The "IRON 4D" Driver - Ultra Low Profile 1A Red Driver

Although I agree... I'm not crazy about using a Constant
Voltage Driver...

Man... you gotta drink less around the holidays. It wreaks
havoc with the memory....


Jerry

No kidding Jerry!

Your URL to where I commented didn't work though. Can you point me? I really don't remember having seen that.

Not at all. You are one of the few people in LPF that create really interesting things.

NCP1529 Driver For RED LASER DIODES - What do you think?

Oh yes - I commented on that, but I didn't think that was on lead. That thread was also about the square ones.

No matter though. You definitely had the idea first.

Oops.... Fixed...
You can clearly see the 3 holes for the LD mounting..

No... seriously... no kidding..

Jerry

Well - not from the thread that I replied to you can't. Those photos are like an inch wide on my screen.

But it doesn't matter - on their forum, they had on lead stuff back in 2010, and I'm happy to concede that.

Come on RHD....
All you have to do is click on the pics in that post to enlarge them...

Here is a "properties" copy from that post...




Jerry

Wow....

What is that, zero for three now?

I need a nap.

^^^

Jerry

Hehe, happens to us all, RHD. The old complicated network of organic wires can only operate for so long without misfiring a few times.

Yep. In my defense, it's the first week of warm weather in Canada, and my mind is still adapting to the humidity + heat

By the way, thank you for the compliment HTV

jeez you all could drive a man to drink lol.