# High current (SST-90) driver



## DIWdiver (Jan 28, 2010)

Hi everyone,

I have been ghosting this board for quite a while, and learning a lot, for which I am grateful. I finally think I may have something to contribute.

There seems to be a shortage of high current drivers for the newest high power LEDs. As a result of a recent conversation, I have designed a driver capable of up to 10A. I'm an engineer by profession and have built several LED drivers, but in the area of flashlights I'm a hobbyist. Since I don't need this driver myself, the question of whether it's worth building is more a question of whether folks would use it than whether I could make money. I'm posting now to see whether people would be interested in this driver if I built a few of them.

The characteristics would be:
Max current:10 A (or less if desired)
Max input voltage: 12V (16V available at higher cost).
Dual-level output: Selectable high/low output, via SPDT switch
Adjustable output: "high" output adjustable from 1A to 10A and "low" output adjustable from 1A to 2.5A by adding series resistors, 10A/2.5A with no resistors.
Size: 1.0 inch diameter by 0.35 inch thick
Heatsink: This is a linear regulator, so it will require heatsinking to protect from overheating. Connection to heatsink would be by one screw, #4, #6, 2.5mm or 3mm, or by thermal epoxy. Heatsink compound recommended if using screw.

This would be a 0-mode driver, meaning it's on whenever you apply power. There's no 'clicky' switch interface. The High/Low switch could have a center off position if you want to turn it off that way. The switch is low current, so it could be a miniature or subminiature switch, not necessary to handle the output current. The driver would be compatible with PWM boards I have seen.

This driver was originally intended for driving a single SST-90 at 7A from a 4-cell Ni-MH battery pack. Though it could be use over a wide range, it would be most efficient when the input voltage is 0.4 to 1.0 volts above the output voltage. With proper heatsinking , the driver could handle up to 30W dissipation, up to 100 watts output. Higher power levels could be made available if necessary.

If there's enough interest, I will make some of these, available at around cost, in the appropriate B/S/T area. If not, then I'm sorry to bother you.

D


----------



## The Dane (Jan 28, 2010)

As of now demand is high and supply is nill, so work on mate

Be aware that another similar project is ongoing and ahead of you by sector_cleared

:welcome:


----------



## SUBjohan (Jan 28, 2010)

Actualy there is antoher one in progress:
By FPPF

I am verry intrested in a driver wich allows me to driver 2 SST90's in series from a 4 series Li-Ion pack (nominal 14,8V max 16,8V).

For me dimming should be ideal via a potentio meter.

Greetz Johan


----------



## KuKu427 (Jan 28, 2010)

Interested! I can't contact you via PM. Can you email me [email protected]


----------



## Techjunkie (Jan 28, 2010)

DIWdiver said:


> "I will make some of these, available at around cost..."
> 
> D


 
Appoximately how much would that be?


----------



## Codiak (Jan 28, 2010)

Theres a market for a 10A and a 5A if the price is right....


----------



## mash.m (Jan 29, 2010)

mhh, i linear regulator for a single sst-90 with a maximum input voltage at 12 volts? are you shure?

my calculations: the sst-90 have 4.0 volts forward voltage at 10 amps, so the regulator must must destroy 8 volts at 10 amps = 80 watt?!?

if you have 4 eneloops then they have 4.8 volt under load maybe a little less. 0.8 x 10 amps = 8 watt also to much for a portable flashlight.

just my two cents...

markus


----------



## Aircraft800 (Jan 29, 2010)

Besides the other drivers in design now (mentioned above), I would be definitely be picking one of these linear regulators up. I have a 4 NiMh project already to go, but never finished it because of all the low resistance mods I did would the LED at full charge. I just didn't want to risk it with a $50 LED.


----------



## HarryN (Jan 29, 2010)

mash.m said:


> mhh, i linear regulator for a single sst-90 with a maximum input voltage at 12 volts? are you shure?
> 
> my calculations: the sst-90 have 4.0 volts forward voltage at 10 amps, so the regulator must must destroy 8 volts at 10 amps = 80 watt?!?
> 
> ...



Hi markus,

More or less, you are correct. The SST-90 all by itself is far to much heat for a hand held "flashlight" for regular use. The SST-90 already draws something like 4V x 10 A = 40 watts, so far above the more practical 15 - 20 watts max for heat generation.

With a linear regulator adding 10 Watts of heat per volt of battery voltage above the LED Vf, this adds up fast.

The 4 - 5 NiMH cells might be a practical use of this linear approach, but even 2 x Li type cells would force the user to wear gloves just with the driver's heat.

As a practical matter, a quality, efficient, reliable, inductor based current mode driver will have a hard time coming to market for much under $75-100 in hobby quantities, at least based on my simple spreadsheet of parts list and pricing. Anyone wanting to play with SST-90s with other than direct drive or resistor limiting for under $ 30 - 40 worth of even a crude driver will have few other options, at least IMHO.


----------



## Sun (Jan 30, 2010)

I would pay 70 bucks for a good one.

If you build it, they will come.


----------



## DIWdiver (Jan 30, 2010)

Sun said:


> I would pay 70 bucks for a good one.
> 
> If you build it, they will come.


----------



## DIWdiver (Jan 30, 2010)

Sun said:


> I would pay 70 bucks for a good one.
> 
> If you build it, they will come.


 
At $70, I would make a killing (which would be cool, but is not my goal). They will be a lot less than that. I'm about ready to order prototype boards and parts.

Can you define good? I expect these will provide full current down to about 4.0V input, 3.6V output. They won't be well protected against surges, transients, ESD, or reverse battery voltage, so they won't be good for automotive applications (intended for battery applications) and could fail with careless handling, but should be pretty rugged once installed in a system. With sufficient heatsinking, they should survive shorted output for any duration.

D


----------



## DIWdiver (Jan 30, 2010)

SUBjohan said:


> Actualy there is antoher one in progress:
> By FPPF
> 
> I am verry intrested in a driver wich allows me to driver 2 SST90's in series from a 4 series Li-Ion pack (nominal 14,8V max 16,8V).
> ...


 
4s Li-Ion would be a lot of extra voltage for a linear driver, all of which would be wasted as heat. For that pack you'd be better off with one of the swithching drivers under development by other members. 

For two LEDs in series. a 7s NiMH or 3s LiIon pack would be better with a linear driver. Even a 2s LiIon would be okay (and much more efficient), if it were acceptable that light output would begin to drop near end of battery life.

Dimming with a potentiometer would work well with my driver. 500K audio taper would be best, I think.

D


----------



## DIWdiver (Jan 30, 2010)

KuKu427 said:


> Interested! I can't contact you via PM...


 
I'm not sure why you can't PM me. I can't log into PM area either. Is that something that gets approved after you turn out to be a good member? I didn't see anything that suggested that in the rules.


----------



## Sun (Jan 31, 2010)

Good for me would mean adjustable in some way thru the range, 5 to 12V input, high efficiency, setup/recall power up,& pwm input.


----------



## HarryN (Feb 1, 2010)

DIWdiver said:


> I'm not sure why you can't PM me. I can't log into PM area either. Is that something that gets approved after you turn out to be a good member? I didn't see anything that suggested that in the rules.



Hi DIWdiver, I think you are right about there being some minimum number of posts / time for PMs to work.

Your idea is good for what it is, a linear driver. It will take some education for people to understand what this means, and the importance of balancing the input voltage, LED Vf, and thermal management. I routinely use resistors to manage LEDs (as well as more advanced drivers) but I understand the trade off. Sometimes, a resistor really is a good way to go.

Possibly a good place to start is to tell them to limit the battery voltage to no more than 2 volts higher than the LED Vf. I can just imagine someone attempting to use a 12 volt battery voltage with an LED with 4 Volts Vf, and then complaining about run time and heat generation at 10 amps. :candle:

Good luck with your project and please keep us updated.

BTW - this would be a good thread to have in the "electronics and battery" section, along with with several other current regulation circuits threads in this section. Perhaps a mod will consider this?


----------



## The Dane (Feb 1, 2010)

A boost driver would be nice 
Driven by a single LiFePO4 cell that can deliver lots of current






http://www.batteryspace.com/lifepo442120emsizecell32v10ah50arate32wh.aspx


----------



## DIWdiver (Feb 1, 2010)

Sun said:


> Good for me would mean adjustable in some way thru the range, 5 to 12V input, high efficiency, setup/recall power up,& pwm input.


 
Unfortunately, "High efficiency, 12V input", and "one LED, linear driver" are mutually exclusive.

Being a linear driver means that the input and output current are the same. The input voltage is dropped across a lossy element (like a resistor) to reach the desired current. A linear driver differs from a resistor in that the lossy element (a transistor) is constantly adjusted to keep the current constant. In a resistor, the value is fixed, so the current changes with input voltage changes.

To calculate the efficiency of a linear driver is very simple, and the equation will reveal a serious drawback of this type of driver:

Eff = Vout/Vin

From this you can easily see that the efficiency tanks as the input voltage goes up.

However, if you carefully match the input and output voltages, the efficiency can be quite good. For example, this driver was intended to be run at Vin of 4.0-4.8V and Vout of 3.6V (that's a 4-cell NiMH pack running one SST-90 at 9A). When the battery is fully charged, the efficiency is 

Eff = 3.6/4.8 = 0.75, or 75%

That's not great, but not terrible. But watch what happens as the battery voltage falls. The efficiency rises to

Eff = 3.6/4.0 = 0.9, or 90%

On average, you'd expect something in the low 80's for percent efficiency. That's pretty respectable for a simple driver like this. But if you were to use 2 LiIon cells, efficiency would range from 43% to 49%. Not many users would be happy with that! In that case you'd really want a switching driver like some others are working on. With those you'd expect efficiencies of 85% and higher all the time. However those are more complex and likely more expensive.

As far as your other desires, there isn't anything to set up in this driver. There is a toggle switch input to turn on high or low setting. Settings can be adjusted down with an external resistor. A PWM input could be implemented, but I didn't include that. I could tell you how to do it externally if needed.

D


----------



## DIWdiver (Feb 1, 2010)

The Dane said:


> A boost driver would be nice
> Driven by a single LiFePO4 cell that can deliver lots of current


 
Yeah, that would be nice. Maybe in a while, if nobody else does it, and if my experience with this one is happy. However you'd need two LEDs in series to use a boost convertor off LiIon (because the output can never be less than the input voltage). Otherwise it would need to be buck-boost, which is more complex and less efficient.

You could boost off one or two NiMH cells...

D


----------



## DIWdiver (Feb 1, 2010)

DIWdiver said:


> I'm not sure why you can't PM me. I can't log into PM area either. Is that something that gets approved after you turn out to be a good member? I didn't see anything that suggested that in the rules.


 

PM now works.

D


----------



## The Dane (Feb 2, 2010)

DIWdiver said:


> Yeah, that would be nice. Maybe in a while, if nobody else does it, and if my experience with this one is happy. However you'd need two LEDs in series to use a boost convertor off LiIon (because the output can never be less than the input voltage). Otherwise it would need to be buck-boost, which is more complex and less efficient.
> 
> You could boost off one or two NiMH cells...
> 
> D


A LiFe is only 3.3V and directly from the charger never more than 3.7V at rest. So under discharge the boost ville be from 3.3V to 3.7V and by the time 11A are used the cell will sag to @3.2V.
No problemo


----------



## Linger (Feb 2, 2010)

simple linear regulator, two modes (I'd prefer low / high) sounds good.

simple reliable and accessable alternative to people running DD could fit a niche

If losses are low enough, possible secondary application would be for those running from 3xnimh, basically introducing low mode. (though this could be an expensive alternative to a 3way switch and resistor.)


----------



## Fulgeo (Feb 2, 2010)

Wanted to pipe in and say I think the low setting should be about 3.2-4.2 amps. I have built two 3D Mag mods using both the SST-50 and the SST-90 emitters. I have found that 4.2 amps is a good compromise taking heat and output into consideration. In a 3D Mag running both these emitters at 4.2 amps you can still tolerate the hand temperature after an hour run. 75%-80% efficiency would be great. The perfect SST-90 driver IMO would be a 2 mode with a low setting of 4.0-4.2 amps and a high setting of 9.0 amps driven by 5 -12 volts. You could also make two circuits. One 5 - 9 volts for flashlight builds and a 12 volt model.

On a side note I have noticed that at 4.2 amps and all other factors being equal the hot spot of my SST-50 build although smaller is slightly brighter than my SST-90 build?:thinking: Now the SST-90 does seem to put out more overall light. Its hotspot is almost twice as large as the SST-50's at 4.2 amps. I am also sure at higher currents the SST-90 would spank the SST-50. The SST-90 has much more spill.

Great thread can not wait to see how it develops!


----------



## Linger (Feb 2, 2010)

3.2A is low? wow.
While OP said adjustable, I do like the reference 1A, something almost useable for physical tasks, like tying your boot, while you're out looking for whatever 9A is used for.


----------



## DIWdiver (Feb 2, 2010)

Hi all,

Parts should be here for prototype build over the weekend. I'm picking up a borrowed 20A power supply tomorrow for testing. I'm probably more excited than any of you!

At the moment I'm thinking of offering it in 4 versions. Hi/Lo settings would be:
5A/1.25A
5A/5A
10A/2.5A
10A/10A

The reason for offering high and low modes the same is that then the user can pick his own low mode by simply adding a resistor to one of the switch terminals. Note that the switch and external resistor are very low current.

If there's some consensus on a setup other than those 4, I might offer that instead or in addition.

I expect the driver to regulate nicely and predictably down to about 10% of the max setting (5 or 10A). Somewhere below that the behavior would get flaky.

D


----------



## Sun (Feb 4, 2010)

Is there a way to have the output adjustable by resistor change on the board? I also am leaning toward running the ssr-90 at 4.2A.


----------



## Codiak (Feb 4, 2010)

DIWdiver said:


> Hi all,
> 
> Parts should be here for prototype build over the weekend. I'm picking up a borrowed 20A power supply tomorrow for testing. I'm probably more excited than any of you!
> 
> ...


 
10A and 5A... would allow driver to work with SST-50 and SST-90


----------



## DIWdiver (Feb 4, 2010)

Sun said:


> Is there a way to have the output adjustable by resistor change on the board? I also am leaning toward running the ssr-90 at 4.2A.


 
Yes, you could change a resistor on the board. The one that's large and easy to change is readily available in only a few values, which would give max currents of 10, 8, 6.7, 5, 4, 2.9 and 2.5A (I could go lower but that would be silly - who wants such a puny light?).

There are two other resistors, one for high and one for low, that can be used to set the current anywhere below the max value. Unfortunately, these two are tiny - only 0.06" x 0.03", so you have to have good eyes and good hands. 

Info will be available with the boards.

D


----------



## DIWdiver (Feb 7, 2010)

So I tested the prototype yesterday. It works pretty well. I ran it for a while at 6V input, 3.6V output, 10A. It seemed to handle that okay.

There are two problems, both easily solved:

I was in a hurry to order the boards so they'd be here for the weekend, and didn't notice that the copper areas didn't fill, so several high-current connections were missing. That was easily solved with some foil and wire. I'll make sure the next boards are right!

To keep the price low, I spec'd a FET that seemed adequate, but not overkill. In practice, it's a bit wimpy. That's always a problem with FETs - the specs say what it will do in ideal laboratory conditions, and you have to figure out how much worse they will be in real life. This one wouldn't give the full 10A at less than 4.7V input, and I melted two of them by pushing the power dissipation too high. It also doesn't seem to transfer heat to the heatsink very well. Tomorrow I'll order some beefier FETs and I should be testing again at the end of the week.












As you can see, the tab of the transistor is between the board and the heatsink. This allows direct contact to the heatsink, while a single screw secures the board and the transistor; it also raises the board off the heatsink a little. This gives room for the components to be on the back of the board, and allows the wires to stick through the board a little.

The prototype board is square (because it's cheaper that way). The final board will be round. You can see the circle that will eventually be the board edge.

The large potentiometer that is mounted on the heatsink is a current control. I happened to have a 1 Megohm pot available, and it adjusts the current from 10A down to 0.6A. A 500K pot would get you down to 1.1A and give better resolution at the high end.


----------



## Aircraft800 (Feb 7, 2010)

Nice to see progress so quickly! Thanks for the update!


----------



## Linger (Feb 8, 2010)

I presume, because you know what you're doing, that there is a reason thermal paste wouldn't improve the transfer of heat from the FET to the board.

Glad the proto went well for you. Sounds like it will roll out no trouble


----------



## DIWdiver (Feb 8, 2010)

Linger said:


> I presume, because you know what you're doing, that there is a reason thermal paste wouldn't improve the transfer of heat from the FET to the board.
> 
> Glad the proto went well for you. Sounds like it will roll out no trouble


 
Actually, there was thermal paste between the FET and the heatsink. The problem is the FET. Its thermal resistance, junction-to-case, is 3.6K/W, while the one I ordered today is only 0.59K/W. At 10W dissipation, that's a reduction of 30 degrees C in the junction temp. When you've only got 100 to play with, that's a big deal.

The first one is actually okay thermally if you don't push it, but I would rather spend an extra dollar on the FET and not have to worry about it. I know someone is going to hook a 2 cell LiIon pack to it. Plus, I had to change it anyway to get the current capacity. If it were only a 5A driver, I'd be spinning new boards and calling it a wrap!

D


----------



## moviles (Feb 9, 2010)

what circuit?

some months ago I was thinking about a circuit as this but it did not I build because it need two batteries


----------



## DIWdiver (Feb 14, 2010)

Hi gang,

New FETs came in yesterday and I've been beating on them today. Actually, I've only been beating on one, 'cause it hasn't failed! Even running the input voltage up to 10V with 3.6V out at 10A (only left it there 10-20 seconds).

I made one minor tweak to the circuit, which won't even require a board change. Looks like it's a go!

I'll be ordering production boards on Monday, parts later in the week. I'll be opening up a sales thread shortly.

Moviles, I'll post the circuit after production devices are ready. It's similar to yours except it uses an op-amp instead of Q2 and a FET for Q1.

D


----------



## DIWdiver (Mar 7, 2010)

Sales thread is now open.

https://www.candlepowerforums.com/threads/264687

D


----------



## DeeperDeeper (Mar 28, 2010)

Sun said:


> I would pay 70 bucks for a good one.
> 
> If you build it, they will come.



For a linear regulator I would pay $2, if I'd need one. I don't.

I don't want use my batteries mostly to warm the water.


----------



## Aircraft800 (Apr 1, 2010)

*I don't know what that guy's crying about, if you don't want it, don't buy it!*


----------



## painfreak76 (Apr 3, 2010)

I'm looking for a driver for my 6 D mag with an SST90. running 10AH NiMH 7.2v pack(6 cells)...


----------



## Al Combs (Apr 3, 2010)

DeeperDeeper said:


> For a linear regulator I would pay $2, if I'd need one. I don't.
> 
> I don't want use my batteries mostly to warm the water.


Nothing wrong with linear regulators. Lots of people use the AMC7135's with no problem. This is the same thing just much bigger.


Aircraft800 said:


> *I don't know what that guy's crying about, if you don't want it, don't buy it!*


What happened to the pictures?:thinking: Nice looking build BTW.
[Edit: I just noticed you moved them to the sales thread.]


painfreak76 said:


> I'm looking for a driver for my 6 D mag with an SST90. running 10AH NiMH 7.2v pack(6 cells)...


With a switching regulator you'd get more runtime from the extra batteries. But in this case you get 30 watts to the emitter and another 30 watts to the FET. DIWdiver mentioned in the sales thread that 4*NiMH was probably the best setup. You could try using a brass threaded rod or a carriage bolt if you can find one that long. Some nuts and washers will take up the missing 120 mm of space. Same runtime, less weight and much less heat. Here is a picture as an example of how to fit an IMR26650 in an uncut 2C Mag.


----------



## gerstl_ossi (May 1, 2010)

DIWdiver said:


> Hi everyone,
> 
> I have been ghosting this board for quite a while, and learning a lot, for which I am grateful. I finally think I may have something to contribute.
> 
> ...


Hi I want to make two LED underwater torch using SST 90 LED. I have just two canister 9Ah Litium Ion, one with 3 cell and one with 4 cells. Can Your driver handel this voltage? If Yes can You sell me two?
Best Regards Ossi


----------



## DIWdiver (May 1, 2010)

gerstl_ossi said:


> Hi I want to make two LED underwater torch using SST 90 LED. I have just two canister 9Ah Litium Ion, one with 3 cell and one with 4 cells. Can Your driver handel this voltage? If Yes can You sell me two?
> Best Regards Ossi


 
If your cells are all in series (about 12V for the 3-cell pack, and about 16V for the 4-cell pack) then the driver can not handle those voltages. The maximum input voltage is 12V, and right off charge, the 3-cell pack would be about 12.6V, the 4-cell pack about 16.8V

If you have the 3 or 4 cells all in parallel then it would work but you probably have too little voltage to driver the SST-90 to 9A. The driver would protect the LED from overcurrent,but after a short time the current would start to fall, and the light would gradually dim as the batteries discharge.

You can run 4 cells in a series-parallel configuration, getting around 8V. The driver would handle this, and your light would be constant until the batteries were completely discharged, then it would suddenly go out when the battery protection circuits kick in. In this configuration, you would expect around 50% efficiency, which means the driver will generate as much heat as the LED, and would need the same kind of heatsink you need for the LED.

If you still want to order, I have some I can ship within a day or two of receiving payment. The sales thread is here: https://www.candlepowerforums.com/threads/264687

D


----------



## curlyfry562 (Sep 28, 2010)

Hey there is a nice instructable on this:

http://www.instructables.com/id/Circuits-for-using-High-Power-LED-s/


----------



## bigterk (Mar 27, 2012)

I am working on a sst-90 lamp as we speak ! I will be powering the unit with a 18v pack , 2.5 amp low and 10 amp high sounds perfect for my unit. e-mail me contact info at [email protected]


----------



## DIWdiver (Mar 27, 2012)

I have a bit of bad news for you, that my driver may not be suited for your project.

The IS1006 is a linear driver, which means if the input and output voltages aren't close, it dissipates a lot of power and the efficiency is very poor.

If you are talking about an 18V (15-cell) NiMH pack, you could run 4 SST-90's in series, and the voltages would work out not too bad.

But if you are talking about a LiIon pack, I guess that would be a 5-cell pack, and the actual voltage would range from 15-21V. At full power and full charge, that would dump over 60W into the driver. It's possible to manage that, but it's a challenge. 

Either of these, you would HAVE to run it with 4 LEDs in series, which would mean dumping something like 170W into the heatsink, between the LEDs and the driver. That will heat it up FAST.

If you want to run only 1-3 LEDs, take a look at this driver instead. It's a switcher, and can handle the input/output differential much better.
http://www.candlepowerforums.com/vb...icient-5A-9A-Buck-Converter-for-SST-50-SST-90

Here's a link to a page that has a whole list of driver suppliers you could check out: http://www.candlepowerforums.com/vb/showthread.php?292465-DIVE-LIGHTING-LIBRARY


----------

