# AMC7135 Specs Inside **UPDATE**



## Drewfus2101 (Mar 22, 2008)

1050mA version:






1400mA version:





Pretty good boards, as long as your in they're small voltage range. DX recommends that you stay within 3.6V to 4.5V. I read that is because between 4.6V to 6.0V (which it can take up to 6.0V) it gets very hot. In my testing I used a small fan to keep the board cool so this did not affect me. 

These are a great alternative to resistors, even though resistors are cheaper. The best thing to do here is order 20 of the 1400mA version and you can remove each of the black AMC boards and each one you remove will cut down the output current by 350mA. I tested this and it does work. 

Where these boards beat resistors is that these give you a semi-regulated output. If you use resistors and alkalines (for example) the flashlight will never be brighter than when you first fire it up. After that, the batteries will start to dim. If you chose your resistor based on the fresh battery voltage, as the batteries start to drain, your output will drop. With these, as long as your voltage stays above about 4.0V you get the full output. The 700mA version should need a lower voltage and the 350mA an even lower voltage. So that semi-regulation is worth the extra money to me. I can't tell you how much time and headache direct drive / resistors / alkalines have caused me. 

I definitely love a good boost/buck convertor more than these, but these things are not bad little boards. I thought others could benefit from these numbers.


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## TorchBoy (Mar 22, 2008)

*Re: AMC7135 Specs Inside*

Nice results. I'd be more interested in graphs of output current for input voltage, though. (I don't quite see the point of efficiency graphs for linear regulators.)

On the subject of them being linear regulators, how did you get more current out that current in?


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## Drewfus2101 (Mar 22, 2008)

*Re: AMC7135 Specs Inside*

I'd say that the current in and current out are probably equal its just that my accuracy in measuring them is slightly off. 

Charts as requested:


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## TorchBoy (Mar 22, 2008)

*Re: AMC7135 Specs Inside*

Wow, _awesome_! That shows just when the thing drops out of regulation. Now, why wouldn't it be completely flat when in regulation? Temperature effects in the AMC7135s?


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## Drewfus2101 (Mar 22, 2008)

*Re: AMC7135 Specs Inside*



TorchBoy said:


> Wow, _awesome_! That shows just when the thing drops out of regulation. Now, why wouldn't it be completely flat when in regulation? Temperature effects in the AMC7135s?



Not this time, at least I doubt it anyways. I had a small 12V fan running off of a separate power source an inch from the board running full out the whole time. It was moving more than enough air to keep the thing cool and the board was very cool to the touch when I picked it up as soon as I turned off the power. But I wouldn't run the same test without the fan, at least not up to 6V and I probably won't use these boards up to 6V without some testing first.


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## ktronik (Mar 23, 2008)

*Re: AMC7135 Specs Inside*

Great info...

I did a test by mistake 

I had a 3d [email protected] with some AMC's in... by mistake I put 3/ 3 AA carriers, way over voltage spec...

The light worked fine, until the AMC's heated up enough to melt the solder holding them on the board & slid off...

After re-solding them back on they still seem to work ok on normal voltage.

I would say they are pretty tough.

with in the right voltage range, they a great cheap circuit to work with...

Great for 4 nimh's, as by the time they are drained (3.2v min) the AMC's are draining very little, a great low batt warning.


K


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## TorchBoy (Mar 23, 2008)

*Re: AMC7135 Specs Inside*

I knew they were tough, but that's amazing. You're talking 180-190 °C. It sounds like a very easy way to get them off the board.

I thought the thermal protection cut in at 150 °C. :thinking:

On a multiple AMC7135 board and too many volts they'll presumeably starting blinking, but they'll all be blinking out of sync with each other. Would it even be noticeable?


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## ktronik (Mar 23, 2008)

*Re: AMC7135 Specs Inside*

I think you may be right... they started blinking a bit, so I tapped the light head...thats when the AMC's slid off the board... 

K


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## mike2g (Mar 24, 2008)

*Re: AMC7135 Specs Inside*

I've been thinking about using these boards in a single li-ion powered light but am concerned with the loss drop in output current after the voltage drops below 4 volts. The reason I like these boards is that the efficiency of the boards is above 90% for most of the life of a single li-ion. However, the output doesn't seem to be very well regulated. According to this, for the case of the 1400ma version, the output current can be expected to drop substantially, 1.28A -> 0.85A, after the battery capacity has dropped to 80% of its' capacity. Basically, a 1/3 drop in out put after a 1/5 drop in battery capacity.

It strikes me that these drivers would be much improved if there were a way to shift the graph over so that the current output could be maintained at a lower battery voltage. Is there a way to do this? 

Also, I'm wondering how the graph could be expected to change if the emitter had a lower Vf. For example it has been rumored that the Q5s have relatively high Vf, so would using a lower Vf emitter such as a SSC P4 shift the graph and increase the range where the output current could be regulated?

Thanks for putting this together, it's been very helpful!


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## SnowplowTortoise (Mar 24, 2008)

*Re: AMC7135 Specs Inside*

Great post! Thanks for passing on the info. 60% efficiency at 6V is pretty scary.

Craig


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## CampingLED (Mar 24, 2008)

*Re: AMC7135 Specs Inside*

Great review. Read a post from "Download" once stating that the diodes on the boards should be shorted out to improve output. This makes sense after checking the data sheets of the 7135s. Will appreciate it if you could do a simple test when the diodes are shorted out.


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## Mr Happy (Mar 24, 2008)

*Re: AMC7135 Specs Inside*



mike2g said:


> I've been thinking about using these boards in a single li-ion powered light but am concerned with the loss drop in output current after the voltage drops below 4 volts.


This is unfortunately to be expected. The board is apparently a buck regulator, which means it can reduce the battery voltage but cannot increase it. Regulators of this type also need an extra margin of input voltage over output voltage to operate properly. In this case that margin is only about 0.3 V, so I think it's doing pretty well.



> The reason I like these boards is that the efficiency of the boards is above 90% for most of the life of a single li-ion. However, the output doesn't seem to be very well regulated. According to this, for the case of the 1400ma version, the output current can be expected to drop substantially, 1.28A -> 0.85A, after the battery capacity has dropped to 80% of its' capacity. Basically, a 1/3 drop in out put after a 1/5 drop in battery capacity.


When the voltage drops below 4 volts the unit has dropped out of regulation due to insufficient input voltage. To obtain good results, the battery used should provide more than 4 volts until fully discharged. [Edit: For the particular LED tested in this case.]



> It strikes me that these drivers would be much improved if there were a way to shift the graph over so that the current output could be maintained at a lower battery voltage. Is there a way to do this?


Not inexpensively, no. If you look at the voltage in vs. voltage out tables, you can see how the unit would have to boost the voltage to achieve what you wish, and this would be extra circuitry.



> Also, I'm wondering how the graph could be expected to change if the emitter had a lower Vf. For example it has been rumored that the Q5s have relatively high Vf, so would using a lower Vf emitter such as a SSC P4 shift the graph and increase the range where the output current could be regulated?


I think it would help, yes. Anything that lowers the required output voltage would extend the range of regulation.


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## Marduke (Mar 24, 2008)

*Re: AMC7135 Specs Inside*

Does anyone know if these can be ran two in parallel to provide the 2.8A required for a P7?


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## Drewfus2101 (Mar 24, 2008)

*Re: AMC7135 Specs Inside*



CampingLED said:


> Great review. Read a post from "Download" once stating that the diodes on the boards should be shorted out to improve output. This makes sense after checking the data sheets of the 7135s. Will appreciate it if you could do a simple test when the diodes are shorted out.



Wow, I almost forgot about that trick. I bookmarked some info about that, but forgot to try that when I was running this test. I should have a night this week to run more tests and I'll add this to my list.


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## Drewfus2101 (Mar 24, 2008)

*Re: AMC7135 Specs Inside*



Marduke said:


> Does anyone know if these can be ran two in parallel to provide the 2.8A required for a P7?



I'm pretty sure they can not. They are "buck" type boards so they can only reduce the voltage in. Notice how the current in and current out are practically identical (not counting multimeter accuracy error)? It would be pretty much the same as direct driving. The only benefit of using two of these (assuming that worked) was to buck the voltage down. But you can't go higher than 6.0V with these and DX recommends no higher than 4.5V due to heat.

I'm sure someone with a P7 will try it and it might just work, but I can't figure out how and it won't be efficient.


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## Drewfus2101 (Mar 24, 2008)

*Re: AMC7135 Specs Inside*



Mr Happy said:


> I think it would help, yes. Anything that lowers the required output voltage would extend the range of regulation.



I'll try and repeat the test with an SSC Z-power. Its the only other emitter I have that is star mounted and will work with my setup. I'll double check the emitter first and make sure it has a lower Vf too.


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## TorchBoy (Mar 24, 2008)

*Re: AMC7135 Specs Inside*



mike2g said:


> It strikes me that these drivers would be much improved if there were a way to shift the graph over so that the current output could be maintained at a lower battery voltage. Is there a way to do this?


Use a lower voltage (Vf) LED.



mike2g said:


> Also, I'm wondering how the graph could be expected to change if the emitter had a lower Vf.


In the way that you want. The AMC7135 needs at least 2.7V and white LEDs have a Vf above that, so you'll be fine.



CampingLED said:


> Read a post from "Download" once stating that the diodes on the boards should be shorted out to improve output. This makes sense after checking the data sheets of the 7135s.


Let's see... The voltage drop across one of those diodes will be ~0.6V so if your input voltage is less than 3.3V it might make a difference, since the AMC7135 needs 2.7V to stay in regulation, but would your LED Vf be that low? Quite possibly - I've got one Cree with a Vf of 3.3V at 1A. Drewfus, it wouldn't have made any difference to your test, because your operating voltages were higher than that.



Mr Happy said:


> The board is apparently a buck regulator, which means it can reduce the battery voltage but cannot increase it.


No - it's a linear regulator - and yes respectively.



Mr Happy said:


> When the voltage drops below 4.0 volts the unit has dropped out of regulation due to insufficient input voltage. To obtain good results, the battery used should provide more than 4.0 volts until fully discharged.


That will depend on what the LED wants. For the particular LED tested, with a reasonably high Vf of 3.7V @ 1A, you do need at least 4V.



Marduke said:


> Does anyone know if these can be ran two in parallel to provide the 2.8A required for a P7?


Yes, not a problem. Someone recently even figured out how to connect a multimode board to a single mode multi-AMC7135 board to get lots of current and multiple modes. The efficiency, Drewfus, comes from running these things with a Vin a little higher than the Vf of the LED. Whether that's 3.3V for a low Vf Cree P4 or 4.2V for a SSC P7 doesn't matter.


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## TorchBoy (Mar 24, 2008)

*Re: AMC7135 Specs Inside*

Here we go - multimode driver for P7. It has also has a diagram of how to connect two 4xAMC7135 boards in parallel. Easy.


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## Supernam (Mar 24, 2008)

*Re: AMC7135 Specs Inside*

Darn, I found this post a little too late. I wanted to use this for 3D NiMH's, but I they provide probably a max total of 4v rested off the charger. I'm thinking the best would be 4D NiMH's or 3D Alkalines. Alkalines shouldn't sag much at only 1A, so I'm thinking I'd get some ridiculously long runtime right?

I guess I can't complain since they're less than $2 each!


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## TorchBoy (Mar 24, 2008)

*Re: AMC7135 Specs Inside*

Supernam, if you're going with alkalines I'd definitely recommend 4 instead of 3. Their voltage really doesn't hold up and most of their life is with a lower voltage than would do the job if you only had 3.

With NiMH, it would depend what the Vf of your LED is and when you wanted the thing to drop out of regulation. Drewfus' test above showed his LED needed 4V for the board to stay in regulation, so 4 NiMH cells would probably work better in that situation, and drop out of regulation at a loaded 1V per cell. Note though that the board might get quite hot when the NiMH cells are freshly charged.


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## Mr Happy (Mar 24, 2008)

*Re: AMC7135 Specs Inside*



TorchBoy said:


> No - it's a linear regulator - and yes respectively.


Very well, I bow to common parlance. Though I don't see why the term "buck" has to be confined only to step-down regulators that use switching technology


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## TorchBoy (Mar 24, 2008)

*Re: AMC7135 Specs Inside*

Yeah, I don't know why that is. It certainly caused a bit of confusion for me before I figured out what people meant by it.


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## Supernam (Mar 25, 2008)

*Re: AMC7135 Specs Inside*



TorchBoy said:


> Supernam, if you're going with alkalines I'd definitely recommend 4 instead of 3. Their voltage really doesn't hold up and most of their life is with a lower voltage than would do the job if you only had 3.
> 
> With NiMH, it would depend what the Vf of your LED is and when you wanted the thing to drop out of regulation. Drewfus' test above showed his LED needed 4V for the board to stay in regulation, so 4 NiMH cells would probably work better in that situation, and drop out of regulation at a loaded 1V per cell. Note though that the board might get quite hot when the NiMH cells are freshly charged.



The more I look at the data, the more I wonder what WAS this board designed for? One LiIon would mean that there would be no regulation for the most part. 2 CR123's is too much. 3 Nimh's would present the same problem as 1 LiIon. It seems as though the only way to go with this board is to use 4 NiMH's. I think 3 D sized Alkalines would work fairly well, at least with the 1050mAh board. 4 would bring you to at least 6v which will run the board pretty darn hot when you're using new batteries. 

I was planning to use this with a SSC P4 with a Vf around 3.3 in 3D Nimh host, but I'm going to just kill my wallet with a buck/boost GD1000 instead (about $25 shipped for 1!). Perhaps this board will be better with a 4C or 4 SubC mag.


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## Drewfus2101 (Mar 25, 2008)

*Re: AMC7135 Specs Inside*



Supernam said:


> The more I look at the data, the more I wonder what WAS this board designed for? One LiIon would mean that there would be no regulation for the most part. 2 CR123's is too much. 3 Nimh's would present the same problem as 1 LiIon. It seems as though the only way to go with this board is to use 4 NiMH's. I think 3 D sized Alkalines would work fairly well, at least with the 1050mAh board. 4 would bring you to at least 6v which will run the board pretty darn hot when you're using new batteries.
> 
> I was planning to use this with a SSC P4 with a Vf around 3.3 in 3D Nimh host, but I'm going to just kill my wallet with a buck/boost GD1000 instead (about $25 shipped for 1!). Perhaps this board will be better with a 4C or 4 SubC mag.



I bought these specifically for modding Mags with alkalines and P4s. Like you said, 3 alkalines are pretty perfect. The 700mA setting is slightly lower than you really want, but still plenty bright and works great for 3 C batteries. And the 1050mA setting works well for 3 D batteries that can handle that current draw better than the C size batteries.


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## mike2g (Mar 25, 2008)

*Re: AMC7135 Specs Inside*



Supernam said:


> The more I look at the data, the more I wonder what WAS this board designed for? One LiIon would mean that there would be no regulation for the most part. 2 CR123's is too much. 3 Nimh's would present the same problem as 1 LiIon. It seems as though the only way to go with this board is to use 4 NiMH's. I think 3 D sized Alkalines would work fairly well, at least with the 1050mAh board. 4 would bring you to at least 6v which will run the board pretty darn hot when you're using new batteries.
> 
> I was planning to use this with a SSC P4 with a Vf around 3.3 in 3D Nimh host, but I'm going to just kill my wallet with a buck/boost GD1000 instead (about $25 shipped for 1!). Perhaps this board will be better with a 4C or 4 SubC mag.


 
I completely agree. Efficiency and regulation occur in two separate parts of the voltage curve, with only a small overlapping area. If you want efficiency greater than 90%, then you have to stay below 4.2V. If you want, regulation you need to stay above 4V. This leaves a 0.2V window to get good regulation and efficiency.

If you are willing to have an efficiency down to 80% the voltage must only stay above 4.6V/4.8V for the 1050ma/1400ma version respectively. Regulation still requires 4V so the window for regulation and efficiency is now 0.6V/0.8V (1050ma/1400ma).

From the battery perspective however, this is difficult to achieve. Li-ions will start at 4.2V and quickly drop below 4V and out of regulation. Regarding alkaline D batteries, it seems that the voltage drop is roughly linear from 1.4V to 0.8V, resulting in a 0.6V change. However because there are multiple cells the change is now 1.8V for 3 cells, and 2.4V for 4 cells. Both of these are much larger than the 0.8V window allowable for 80% efficiency.

Nimh may be the best solution however for it's ability to maintain voltage up to the bitter end. At the 1A draw rate for AA, the discharge is primarily between about 1.35V to 1.15V giving a change of 0.2V. This change is 0.6V and 0.8V for 3 and 4 cells respectively. This range seems reasonable for the 80% efficiency minimum and the best compromise from the available battery choices.

The only optimism I have left for this board is in the coming SSC P4 test with the lower Vf. Hopefully the regulated range will increase. Thanks Drewfus2101 for doing the meticulous testing! :thumbsup:


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## freedom2000 (Mar 25, 2008)

*Re: AMC7135 Specs Inside*



Drewfus2101 said:


> 1050mA version:
> 
> I definitely love a good boost/buck convertor more than these, but these things are not bad little boards. I thought others could benefit from these numbers.



Hi Drewfus2101,

Many thanks for this nice technical review. (I have just bought such a driver, and you already helped me a lot).

You mentionned however that you prefer boost drivers...
Would you have a recommendation for me to find a good (and cheap) driver to drive a Q5 Cree led at 1A with one or two Nimh ?

My intention is to mod this flashlight, which has curerntly a rather inefficient driver see here

Again, thanks for your help
JP


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## TorchBoy (Mar 26, 2008)

*Re: AMC7135 Specs Inside*



Drewfus2101 said:


> And the 1050mA setting works well for 3 D batteries...


Why?







(That Energizer Max doesn't do too well compared to the others.)

Within a handful of minutes the cells are down to 1.4V, and by the time they hit 1.2V there's, what? 75-80% of the life left. And even 3x1.2 V would be enough only if the Vf of the LED is <=3.4V. Yeah, they exist in quite a few P4s, but I don't think many Q5s. From 1.2V onward, even a 3.4 Vf LED would be out of regulation.

I still say three alkaline cells are not suited for this driver (unless you want to just use the top 20% of each cell's capacity).

mike2g, your point of voltage difference is very good. I'll still say 4 alkaline cells will work quite nicely, though, with a qualifier or two. Because of the way alkaline cells discharge, the board when used with the LED tested above would be in the higher efficiency area (median would be 84.5%) for four times longer than it would be in the low efficiency area. So for efficiency, it would work nicely. If regulation is your goal, however, you'll have to use a low Vf LED to have it stay in regulation until 0.8 V per cell, and that would push the median efficiency down (to ~75%), which I'd still be happy with for efficiency as well. I don't deny you might have trouble finding the right LED though.



mike2g said:


> Efficiency and regulation occur in two *separate* parts of the voltage curve, with only a small *overlapping* area.


That's a contradiction. I suppose the efficiency area isn't quite a subset of the regulated area, so you could say the areas are in different, but not separate, places.



mike2g said:


> Thanks Drewfus2101 for doing the meticulous testing!


It's a great test, and both very interesting and very useful, but meticulous probably means something other than what you intend. You can't have 1.24 A in and 1.28 A out with a linear regulator - no disrespect intended to you Drewfus.

(Actually, one definition for meticulous I found is "ridiculously obsessed with extreme minutiae" - which would be me posting this.  )



freedom2000 said:


> Would you have a recommendation for me to find a good (and cheap) driver to drive a Q5 Cree led at 1A with one or two Nimh ?



freedom2000, I don't think such a driver exists, if $20 (for a GD1000) doesn't come into your idea of cheap. Have you seen the driver list?


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## Drewfus2101 (Mar 26, 2008)

*Re: AMC7135 Specs Inside*



freedom2000 said:


> Would you have a recommendation for me to find a good (and cheap) driver to drive a Q5 Cree led at 1A with one or two Nimh ?



I wish I did. I've bought the only two single mode boost drivers that DX sells but have only had time to test one. I'm trying to do the same thing.

This is the one that seems better, but I havn't had a chance to test it. I'll post the results when I get a chance:
http://www.dealextreme.com/details.dx/sku.4735

Here is the other one. You can see my post at the bottom of the page. These boards are useless as boost boards. Maybe they are just mislabeled. 
http://www.dealextreme.com/details.dx/sku.4382


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## Drewfus2101 (Mar 26, 2008)

*Re: AMC7135 Specs Inside*



TorchBoy said:


> Why?
> 
> 
> 
> ...



To your first question about using the 1050mA with 3 D alkalines, I should have said that was my choice OVER direct driver or resistors. As I said, DD with resistors was always a headache. These are better, but definitely not perfect. 

For the Mag that I made for a friend, I used a SSC P4 and the 700mA version with 3 D alkalines. It was that or a 1 ohm resistor.


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## Drewfus2101 (Mar 27, 2008)

**UPDATE**

Following the suggestions, I tried a few different things. First I found a SSC Z-Power P4 emitter and tested it:






So it has a more lower Vf than a Cree Q5 does.

Then I hooked it to the 1050mA version of the AMC7135 and re-ran the normal test the exact same way as before. Next I took out the diodes and soldered in a leg from a resistor in place and re-ran the same test. Both tables are below followed by the graphs.











Removing the diodes didn't seem to make much of any difference at all in the efficiency:


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## freedom2000 (Mar 27, 2008)

*Re: AMC7135 Specs Inside*



Drewfus2101 said:


> I wish I did. I've bought the only two single mode boost drivers that DX sells but have only had time to test one. I'm trying to do the same thing.
> 
> This is the one that seems better, but I havn't had a chance to test it. I'll post the results when I get a chance:
> http://www.dealextreme.com/details.dx/sku.4735
> ...



Thanks !

The first one is backordered ...

So I have ordered this one (it has good reviews... I couldn't resist :thinking

What seems to be nice is that it has a pot to trigger the output level (left side of the pic)





JP


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## TorchBoy (Mar 27, 2008)

This test just gets better and better. You the man! :bow:

Those output current figures are sometimes still a bit high compared to the input current (as much as 4.4%). What can be done about that?

It looks like taking out the diodes has not made a significant difference for the voltage range tested. That supports what I said in post 17, but even your SSC P4 doesn't have a low enough Vf at 1 amp to know for sure if it will make any difference at even lower voltages. But what you've basically done is Mythbusted the idea for any except possibly the very lowest Vf LEDs, or low VF LEDs run at lower current.  Could you the test with just one AMC7135 on the SSC? That would show what happens to regulation at a slightly lower voltage.

Of course, using the diodes will mean the board could be used at up to 6.6V in.


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## CampingLED (Mar 28, 2008)

Thanks again for your great info/review. On the morning of your first post I purchased a 3D to use for a quad Cree Q5 mod. The intention was to use these drivers. Now I know I need another solution. I should have gone for the 4D instead, but like the size and feel of the 3D.


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## Drewfus2101 (Mar 28, 2008)

TorchBoy said:


> This test just gets better and better. You the man! :bow:
> 
> Those output current figures are sometimes still a bit high compared to the input current (as much as 4.4%). What can be done about that?
> 
> ...



I think the current figures _are _the same but that my readings methods add some error in there. The current in reading is coming straight off my power supply. The current out in a multimeter with the leads spliced into the wiring of a setup that I made to test emitters and driver boards. So I feel that the current is the same and the error is coming from my method of reading, although there is no other way of reading. I did try and use the largest guage wire that I could find, but couldn't use the thickest stuff in my entire setup. I'll try and snap some pics when I get a chance. 

I can re-run the test at the 350mA level. It will be early next week before I get a chance, but thats no problem. I'll start a new thread at that time. I might even see what happens at 6.6V.


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## Drewfus2101 (Mar 28, 2008)

CampingLED said:


> Thanks again for your great info/review. On the morning of your first post I purchased a 3D to use for a quad Cree Q5 mod. The intention was to use these drivers. Now I know I need another solution. I should have gone for the 4D instead, but like the size and feel of the 3D.



Glad I could help. Thats the whole point after all. To help educate myself and whoever else will listen and hopefully help other people make the right choice in they're projects.


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## TorchBoy (Mar 29, 2008)

I guess the only ways to get around that current measuring problem would be to repeat the test run with all voltages measuring the current in with your multimeter - lot more work - or get a second meter.

I don't think there's much need to test the high voltage limit of the poor thing, although knowing a bit more about failure modes might be useful. Your call on destructive testing.


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## Supernam (Mar 31, 2008)

Awesome update! 

***Off topic plug. If anyone would be willing to trade some of the 1400mA versions for 1050mA version, please PM me. I need 2, but can trade up to 6. (Don't feel like ordering another set of 10).


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## TorchBoy (Mar 31, 2008)

Supernam, why don't you just pull a couple of AMC7135s off a board and put an extra one on a couple of boards? Or piggyback them and just have one board with lots and lots.

Edit: Not unlike this doubled board from KD, which arrived in just the last week.


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## TorchBoy (Apr 9, 2008)

Drewfus2101 said:


> I can re-run the test at the 350mA level. It will be early next week before I get a chance, but thats no problem. I'll start a new thread at that time. I might even see what happens at 6.6V.


Have you had a chance to run that test yet? (I don't think I've missed any new threads about it.)


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## Drewfus2101 (Apr 9, 2008)

TorchBoy said:


> Have you had a chance to run that test yet? (I don't think I've missed any new threads about it.)



No not yet. I'm hoping tonight or tomorrow night I will get a chance. I'll add the info in this thread when I do.


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## Drewfus2101 (Apr 9, 2008)

Here is a picture of my graphs from todays test:







I used the "modded" board with the removed diodes because it was handy and had the wires soldered on. But my tests showed that it doesn't make a difference. 

The emitter checked out, running straight off the bench power supply, at 3.0V and 0.29A. Just for reference. 

You can see that this thing has to obviously burn off much more current so the efficiency is lower. It's still not horrible considering though.


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## TorchBoy (Apr 9, 2008)

*Re: AMC7135 Specs Inside*

Ahem:



TorchBoy said:


> Let's see... The voltage drop across one of those diodes will be ~0.6V so if your input voltage is less than 3.3V it might make a difference, since the AMC7135 needs 2.7V to stay in regulation, ...



At 3.4 V the single AMC7135 would still have enough volts on its Vdd pin to stay in regulation even _with_ a diode. 

You don't even drop out of regulation in that test. Your conclusion is premature.


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## jar3ds (Jul 16, 2009)

*Re: AMC7135 Specs Inside*

for real... i want to keep seeing this graph going as it reaches 2.5v

i'm confused because it would seem that per the 1st page after about 3.9v the regulation is gone....

on this test it stays completely fine all the way to 3.4?


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## Justin Case (Jul 17, 2009)

*Re: AMC7135 Specs Inside*



jar3ds said:


> for real... i want to keep seeing this graph going as it reaches 2.5v
> 
> i'm confused because it would seem that per the 1st page after about 3.9v the regulation is gone....
> 
> on this test it stays completely fine all the way to 3.4?



The tests are different. The one on Page 1 with the Cree Q5 uses a 3xAMC7135 board to deliver 1050mA nominal to the LED. This latest test uses a 1xAMC7135 board to deliver 350mA nominal.

The deal is that at the lower 350mA drive current, the SSC P4's Vf is also lower -- ~3.0V vs 3.4V at 1050mA drive current. Unfortunately, Drewfus2101 didn't go low enough in voltage for his test of the 1xAMC7135 case. He needed to get below 3.3V at least to see if there is a difference when removing the diodes. With the diodes installed, to run in regulation you need Vf > Vdd min of an AMC7135 + Vdrop of a typical diode = 2.7V + 0.6V = 3.3V (I've measured ~0.55V drop for the diodes on my AMC7135 boards). Thus, your typical LED's Vf probably already meets this requirement and removing the diodes does nothing for you.

However, if you have a low Vf LED (e.g., a 4P MC-E, which I've measured at 2.96V at 1000mA nominal drive current; or an SSC P4 driven at 350mA), then you need to remove the diodes to satisfy the requirement of Vf > Vdd + Vdiode, where Vdiode = 0V since you've removed them. Thus, the requirement becomes Vf > Vdd, or Vf > 2.7V, which is satisfied for the low Vf 4P MC-E and SSC [email protected]

Since you also need Vbatt > Vf + AMC7135 drop (=0.12V) for the board to run in regulation, the test should go down to at least ~3.1V. For completeness, you may as well go down to at least 3.0V to see what output current you get when the driver does fall out of regulation.

From this latter requirement for Vbatt, you can see the effect of Vf on your input voltage requirements. For the P.1 test using the Cree Q5, Vf~3.70V-3.75V and thus Vbatt has to be at least about 3.8V-3.9V to run in regulation. For the P. 1 test with the SSC P4 @1050mA nominal, Vf~3.4V, and Vbatt has to be at least ~3.5V. For the P. 2 test with the SSC [email protected] nominal, Vf~3.0V, and Vbatt has to be at least ~3.1V. The first two tests go low enough in voltage that you can see this behavior (although the 0.2V voltage input intervals aren't quite fine enough to specifically pinpoint Vbatt for regulation, the tests certainly bracket Vbatt,reg to where you'd expect it to be). The third test doesn't go low enough in input voltage.


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## zxcasd (May 30, 2010)

*LM317 ok with AMC7135-based drivers?*

Hello all,

I apologize for the Thread Necromancy, but I've been lurking for a very long time, and am finally starting to dive in, and I have a general question regarding these drivers. 

I'm hoping to use various of the AMC7135-based boost drivers from DX in an automobile. I just purchased one of their SKU 3178 1400ma drivers, but in reading this thread, the max input voltage is 6V, and preferred is closer to 4V for efficiency reasons. That being the case, and given that nominal full-charge auto voltage is 13.8, I've been thinking about various ways to reduce that voltage. The simplest method to me would just to be to use a regulator, say an LM317, but I'm curious whether this would cause any problems with those drivers - has anyone done this? The 1.5A rating on a 317 should be sufficient according to the charts here, I'm more wondering about the inherent design of voltage regulator circuits in combination with the driver boards - any weird oscillations, peaks, and so forth that might cause the Magic Smoke to come out of either the VR or the driver.

Thanks, all. 

Regards,

Tom


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## TorchBoy (May 31, 2010)

*Re: LM317 ok with AMC7135-based drivers?*



zxcasd said:


> I'm hoping to use various of the AMC7135-based boost drivers from DX in an automobile. I just purchased one of their SKU 3178 1400ma drivers, but in reading this thread, the max input voltage is 6V, and preferred is closer to 4V for efficiency reasons.


:welcome: zxcasd

The AMC7135 driver is a linear regulator, not a boost driver. There appear to be some boost drivers which MAY have linear regulators to help cope with situations where the input voltage is above the output voltage, but they are NOT what you should be using, because they're designed for a single Li-ion cell.

Are you committed to using an AMC7135 driver? If so, why? There are buck drivers that work very well and very efficiently on automotive voltages.


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## wquiles (May 31, 2010)

*Re: LM317 ok with AMC7135-based drivers?*



zxcasd said:


> Hello all,
> 
> I apologize for the Thread Necromancy, but I've been lurking for a very long time, and am finally starting to dive in, and I have a general question regarding these drivers.
> 
> ...



The 317 is a linear voltage regulator. If you set the output voltage at 6 volts (to power your AMC7135 regulator), you then have a voltage difference across the input and output of the 317 of 13.8-6= 7.8 volts. This times the 1.4Amps, give you a very high power loss as heat. Since in a linear regulator the input and output current is the same:

Power input = Input voltage * Input current = 13.8 * 1.4 = 19.32 watts
Power output = output voltage * input current = 6 * 1.4 = 8.4 watts

Power lost as heat in the 317 = Voltage Differential * Current = 7.8 * 1.4 = 10.9 watts
Power lost as heat = Power input - Power output = 19.32 - 8.4 = 10.9 watts

Efficiency = (Power Input - Power lost as head) / Power input = (19.32 - 10.9) / 19.32 = 0.435 => 44% efficient
Efficiency = Power output / Power Input = 8.4 / 19.32 = 0.435 => 44% efficient

=> 44% efficiency is just plain horrible due to the heat being dissipated by the 317.

So, you better have a large and efficient package and heatsink combo for the 317 or it will either fry itself in short order, or it will shut down (assuming it has a built-in temp cut-off). Either way a not so good solution.

A much better way would be to buy a DC-to-DC driver LED converter that is designed from the ground up to work with higher voltages and to be highly efficient while doing so, typically 85-90% or better, like the LED drivers from TaskLED: http://www.taskled.com/

Just my 2 cents


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## Fallingwater (Jun 1, 2010)

After toying with them a bit, it seems to me that AMC boards are less useful than many people think.

If you use a high Vf LED then they're quite efficient, but they don't provide useful regulation for long; they basically serve as a protection to the LED when the battery is fully charged, and then just direct drive.
On the other hand, if you use a low Vf LED (say, a XP-G) then they regulate for a long time (possibly all the time if powered with a LiIon), but their efficiency drops significantly - all they're doing is essentially burning off everything that's above what the LED wants.

Man, I wish there was such a thing as self-regulating batteries... *sigh*


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## milkyspit (Jun 1, 2010)

Fallingwater said:


> After toying with them a bit, it seems to me that AMC boards are less useful than many people think.
> 
> If you use a high Vf LED then they're quite efficient, but they don't provide useful regulation for long; they basically serve as a protection to the LED when the battery is fully charged, and then just direct drive.
> On the other hand, if you use a low Vf LED (say, a XP-G) then they regulate for a long time (possibly all the time if powered with a LiIon), but their efficiency drops significantly - all they're doing is essentially burning off everything that's above what the LED wants.
> ...




The main virtue of the AMC7135 is that it's cheap.


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## kramer5150 (Jun 1, 2010)

Fallingwater said:


> After toying with them a bit, it seems to me that AMC boards are less useful than many people think.
> 
> If you use a high Vf LED then they're quite efficient, but they don't provide useful regulation for long; they basically serve as a protection to the LED when the battery is fully charged, and then just direct drive.
> On the other hand, if you use a low Vf LED (say, a XP-G) then they regulate for a long time (possibly all the time if powered with a LiIon), but their efficiency drops significantly - all they're doing is essentially burning off everything that's above what the LED wants.
> ...



x2... I have found this to be the case with my 1.4A boards. Works better with the XPG than XRE. Its probably the simplest component & trace layout of any board I know. There is some degree of built in redundancy too, which is a good thing. With diodes bypassed its just a bunch of 7135s protecting the emitter from the cell.


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## TorchBoy (Jun 1, 2010)

Fallingwater said:


> On the other hand, if you use a low Vf LED (say, a XP-G) then they regulate for a long time (possibly all the time if powered with a LiIon), but their efficiency drops significantly - all they're doing is essentially burning off everything that's above what the LED wants.


With a low Vf LED they work out quite nicely with 3x NiMH because the initial voltage drop of NiMH (from fully charged) is quite rapid. By the time the battery voltage settles down (normally not very long) the AMC7135 is much more efficient, so the _average_ efficiency is quite a bit higher than if you calculate it assuming a linearly dropping battery voltage - NiMH cells don't work that way.

AMC7135s are extremely simple to use, and they can be quite versatile if you get creative - for example, my latest headlamp uses one multimode board driving two other single mode boards, and each driving one of three high power LEDs.

Of course the AMC7135s have limitations. One issue that is starting to come up more often now is the amount of battery power required to drive the latest high power LEDs at high current, like 2.8-3.0 A or so. AMC7135s scale up very easily but voltage sag in the battery and parasitic resistance in the circuit makes it harder to get a good voltage from the same batteries that work fine at lower currents. That's not the fault of the drivers, it's an issue with getting an appropriate battery/driver/LED combination. When it came up with my headlamp I solved it by adding another NiMH cell.

Like any driver, the AMC7135 is better suited to some situations than others, but it has a lower voltage overhead than any buck driver you're likely to come across.


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## bitslice (Jun 2, 2010)

Instead of modding all these little AMC7135 boards from DX,
isn't it possible to just buy the 3 pin AMC7135 regulator chip itself ?

then we could make our own driver boards in whatever form factor was appropriate and whatever current regulation was required


I've had a look but I didn't see a supplier in the UK


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## TorchBoy (Jun 3, 2010)

bitslice said:


> Instead of modding all these little AMC7135 boards from DX,
> isn't it possible to just buy the 3 pin AMC7135 regulator chip itself ?


Sure, if you want 10,000 of them.  Occasionally someone gets a bunch; probably not quite in quantities of 10,000. Do you feel like organising a group buy? Or put in a product request at DX?

I recall a CPFer bought a bunch of AMC7150 chips.


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## eatkabab (Dec 23, 2011)

Drewfus2101 said:


> I can re-run the test at the 350mA level. It will be early next week before I get a chance, but thats no problem. I'll start a new thread at that time. I might even see what happens at 6.6V.



I know this thread is old, but I would be VERY interested to see the test results from a single 350ma version. I'm hoping to use this chip to run an XR-E at a steady 350ma and would like to be sure the Vf of the chip would be above the LED's required 3.3v throughout the life of a single lithium battery.

Many thanks, and happy holidays


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## Justin Case (Dec 24, 2011)

eatkabab said:


> I know this thread is old, but I would be VERY interested to see the test results from a single 350ma version. I'm hoping to use this chip to run an XR-E at a steady 350ma and would like to be sure the Vf of the chip would be above the LED's required 3.3v throughout the life of a single lithium battery.
> 
> Many thanks, and happy holidays



Just remove the reverse polarity diode that is typically present on these Chinese 7135 boards. Then your Vf requirement is Vf > ~2.7V, which is undoubtedly the case for your XR-E at 350mA drive. When you say that you are going to power your XR-E with a "single lithium battery", I hope you mean Li-ion.


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## eatkabab (Dec 24, 2011)

Justin Case said:


> Just remove the reverse polarity diode that is typically present on these Chinese 7135 boards. Then your Vf requirement is Vf > ~2.7V, which is undoubtedly the case for your XR-E at 350mA drive. When you say that you are going to power your XR-E with a "single lithium battery", I hope you mean Li-ion.



Yeah I was wondering what that reverse polarity diode does. Does it have any real purpose other than maybe protection from applying a voltage the wrong way? And yeah, I'm using Lipo batteries. Two small 590ma ones in parallel to drive an XR-E at ~1watt for hopefully about 5hours.




Th232 is being super helpful in another thread, but here seems like a good place to ask this as well:

I read a lot about the AMC7135 chip and while it simplifies everything I'm doing, I have a hard time believing it's as efficient as a buck regulator or any step down converter. Unfortunately I haven't been able to find any such chip that operates on the voltage of a single Lipo. I'm guessing because there is little demand for the modulation of 3.7 -> 3.3v.

The LTC3490 Buck boost is the closest thing I've found that meets all my requirements (even dimming!) but the data sheet says Vin is 1-3.2v. Considering I don't need a 'boost' this wouldn't make sense anyways.

I know that the AMC7135 burns off excess power but it's somehow claiming >90% efficiency, even >95% at times. Buck Pucks claim 95%. If this is true, then I don't really have any reason to go after anything more complex than the AMC7135 as run-times wouldn't change significantly. I'm trying to maximize run-time with this little bit of power that I have to work with (6hrs would be great, 5hrs will do). Unfortunately I cannot make the batteries much larger in my application.


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## eatkabab (Dec 24, 2011)

I just noticed the latest chart posted by Drewfus2101 is for a single 350ma AMC7135. I'ts showing ~80% efficiency around a Lipo's ~3.7v voltage range. I'm not sure if the chart is just a plain AMC7135 because it was a modded board but if so, that's not too great.

Are there any other driver alternatives that run off a Lipo's voltage range, supply ~1W (350ma), and have >90% efficiency? Simple high/low pin voltage dimming would be a wonderful but not absolutely necessary addition also.



Studying the chart readouts in this thread, it seems multiple AMC7135's on a single board is more efficient than just a single chip. Since I would like to produce ~350ma, is there a 120ma version of the AMC7135 that I could use 3 of in parallel to achieve higher efficiency rates?


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## Justin Case (Dec 24, 2011)

eatkabab said:


> I just noticed the latest chart posted by Drewfus2101 is for a single 350ma AMC7135. I'ts showing ~80% efficiency around a Lipo's ~3.7v voltage range. I'm not sure if the chart is just a plain AMC7135 because it was a modded board but if so, that's not too great.Are there any other driver alternatives that run off a Lipo's voltage range, supply ~1W (350ma), and have >90% efficiency? Simple high/low pin voltage dimming would be a wonderful but not absolutely necessary addition also.Studying the chart readouts in this thread, it seems multiple AMC7135's on a single board is more efficient than just a single chip. Since I would like to produce ~350ma, is there a 120ma version of the AMC7135 that I could use 3 of in parallel to achieve higher efficiency rates?



7135 efficiency is basically Vf/Vbatt. At low drive current, you have a low Vf and less battery sag so that Vbatt is higher. With more 7135 chips, you have higher drive current. Thus, Vf is higher and Vbatt is lower (more sag), and efficiency goes up.

Using three 120mA linear regulator chips in parallel most likely won't help your efficiency. It'll still be Vf/Vbatt and Vf and Vbatt will essentially be the same (I doubt there will be much difference between 360mA vs 350mA drive).

Why are you so concerned over 80% vs 90% efficiency at 350mA drive? For heat sinking equivalent to a P60 type drop-in application, waste heat from the lower efficiency won't be an issue. And you'll draw about 1.2W vs 1.1W, so unless your Li-ion capacity is really limited, I doubt you'll notice an impact on run time either. Do you need a 17mm diam driver, which is the typical size of these 7135 drivers? If not, you could use a 14mm diam GD400 from The Sandwich Shoppe. But the price will be a lot higher than for a 7135 board.


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## moderator007 (Dec 24, 2011)

The effeciency is not a constant unless the voltage is constant. The battery will continue to have a lower voltage as it is drained. While the effiency will increase as the battery is drained. Battery sag will also play a part in the voltage seen by the regulator effecting effiency increase. If you look at this test you can see the exact voltage the cell has at different load test for a given time. By looking at the cell test charts and the amc7135 test charts you should be able to figure out how the efficiency will be over your entire run time given you use a similar battery. The battery you use will determine alot of how efficient the amc7135 will be. If you can find a test graph of your particular battery at a 350ma load. Then you should be able to predict the effiency through the run time.


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## eatkabab (Dec 24, 2011)

So I'm beginning to understand...

My battery capacity is very limited (mainly due to weight). I don't have more than 1200ma to work with at MOST. The setup is two ~600ma Lipo cells in parallel running a single XR-E LED at ~1watt. I would be shocked if I could find a chart showing the efficiency of exactly that setup with this particular cell, so I'm basically asking if in your(s) experience, would you know of anything that might be more efficient than a single AMC7135 chip for my setup?


I'm going to be getting a few 17mm boards for testing but ultimately I'll be putting the actual AMC7135 chip on my own custom board.
As always, I am eternally thankful for everyone's help in this community.


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## moderator007 (Dec 24, 2011)

Its going to be hard to beat the cost and simplicity of the amc7135. There are other drivers as Justin Case mentioned but with additional cost and for maybe a very small improvement in run time if any.


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## Justin Case (Dec 24, 2011)

eatkabab said:


> So I'm beginning to understand...
> 
> My battery capacity is very limited (mainly due to weight). I don't have more than 1200ma to work with at MOST. The setup is two ~600ma Lipo cells in parallel running a single XR-E LED at ~1watt. I would be shocked if I could find a chart showing the efficiency of exactly that setup with this particular cell, so I'm basically asking if in your(s) experience, would you know of anything that might be more efficient than a single AMC7135 chip for my setup?
> 
> ...



A nominal 350mA 7135 driver will draw 350mA at the tail. So 1200mAh battery capacity in theory could last for 3 hrs or more. Are you sure you are battery-limited? Since you don't seem willing to tell us what batteries you are using, it is an unanswerable question as to how well your batts can hold their voltage so that you stay in full regulation for as long as possible.

As a worked example, assuming that your XR-E Vf at 350mA drive is 3.0V and adding some arbitrary amount of parasitic resistance due to flashlight contact resistances, I'd make a WAG and say that Vbatt has to stay above 3.3V to run in full regulation. If you used something like the AW IMR16340 cells (not a LiPo), you'd be able to stay above 3.3V for virtually the full capacity of the cell, or about 500mAh. See here for the data on these cells. For two parallel cells totaling 1000mAh capacity, that would give you an estimated run time of 1000/350 ~3 hrs.

If you have a hobby charger, you may be able to run a discharge test on your cells to see well they hold their voltage under a 350mA load.

A GD400 from The Sandwich Shoppe might give you 85% or better. But they are $18 each.


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## eatkabab (Dec 25, 2011)

Justin Case said:


> A nominal 350mA 7135 driver will draw 350mA at the tail. So 1200mAh battery capacity in theory could last for 3 hrs or more. Are you sure you are battery-limited? Since you don't seem willing to tell us what batteries you are using, it is an unanswerable question as to how well your batts can hold their voltage so that you stay in full regulation for as long as possible.




I'm trying to use two 590ma Li-po cells in parallel that are 5x20x60mm in size. I may have figured a way to use a single 1500ma cell though.

So from what I've learned, the 7135 is extremely efficient if the Vin almost equals Vf. Since the discrepancy between my likely required 3.3v Vin and battery voltage of 3.5-4.2v(mostly 3.8v because of 1/4C power draw per cell), the 7135 would burn off ~0.5v as heat which would equate to wasting about 13.5% batt (.5/3.7=.135). That's ~160mah of my 1180mah pack which would be ~28min of possible run-time lost as heat ----- in a perfect world.

What if I were to use a DC/DC to convert the batt voltage range to 3.3v then feed that into the 7135 to regulate it down to 350ma. Would you think efficiency would improve? Can't find a buck that meets my perimeters of a single Li-po cell and 1W output; trying to turn the lost voltage into usable energy...


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## eatkabab (Dec 25, 2011)

ooh! what about this thing: http://www.intersil.com/products/deviceinfo.asp?pn=EL7535

would that be more efficient than a 7135 at outputting 1W on a Li-po? Might it have some problems supplying ~3v 350ma when the battery drops to the 3.5v range? Would that be called the 'drop out voltage'?


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## moderator007 (Dec 25, 2011)

According to the data sheet "the output can be externally set from .8v to Vin with a resistive divider". So the V out could be set right down to the vf of the led used. Which is well below the battery recommended discharge voltage. Allowing you to drain the battery completly. For the safety of the battery it might be better to set the voltage output to the battery recommend lowest discharge voltage.


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## MikeAusC (Dec 25, 2011)

eatkabab said:


> What if I were to use a DC/DC to convert the batt voltag range to 3.3 then feed that into the 7135 to regulate it down to 350ma. Would you think efficiency would iCan' a buck that meets my perimeters of a single Li-po cell and 1W output; trying to turn the lost voltage intsable energy...




The DCDC will most probably only be 80% efficient in the real world, so there is no way adding a DC DC will improve efficiency. At these low voltages a 7135 is going to be your best solution.


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## Justin Case (Dec 25, 2011)

moderator007 said:


> According to the data sheet "the output can be externally set from .8v to Vin with a resistive divider". So the V out could be set right down to the vf of the led used. Which is well below the battery recommended discharge voltage. Allowing you to drain the battery completly. For the safety of the battery it might be better to set the voltage output to the battery recommend lowest discharge voltage.



Voltage regulator alone is probably not what you want to drive an LED.


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## eatkabab (Dec 25, 2011)

I'll be testing a few drivers for efficiency when I get them (few weeks), but in the meantime, I'm also looking for the highest energy density battery in the lightest package. 

New thread: http://www.candlepowerforums.com/vb...lls-that-are-actually-500-mah-or-R123-700-mah


Ideally a standard sized cell such as a CR2 or CR123 for cost effectiveness but lithium polymer will do as well. Wish I could use a single 18670 but that weighs too much (46g), unless a <30g 1800mah version exists.

- As close to ~3.5v average as possible (ending cell voltage ~3v).
- Ideally be looking for 1800ma out of 34g worth of any cell(s) (no more than ~17g/cell).
- Total power draw would be 350ma from the whole setup weather in parallel or just once cell.


Have looked at lots of information, the best of which being a CR123 brand comparison:http://www.candlepowerforums.com/vb/showthread.php?195712-Some-R123-li-ion-comparison-tests


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## moderator007 (Dec 25, 2011)

Justin Case said:


> Voltage regulator alone is probably not what you want to drive an LED.


According to the data sheet on the EL7535 Monolithic 350mA Step-Down Regulator (Iout Max .35 A)


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## eatkabab (Dec 26, 2011)

Can I use a 555 timer for PWM before or after a 7135 to get lower than 1W(350ma) output?


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## MikeAusC (Dec 26, 2011)

Yes, the 7135 is well suited to being controlled by a low power source. 

When the Minus input is pulled to ground the LED is on, if it's open or Positive it's off.


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## Walterk (Jun 24, 2012)

Can anyone tell or estimate how much current is passing through the VDD line for a single AMC7135 in use? 
I understood it is a low current compared to the total current draw. 
Want to figure out the smallest switch capable of doing the job.


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## wquiles (Jun 24, 2012)

Walterk said:


> Can anyone tell or estimate how much current is passing through the VDD line for a single AMC7135 in use?
> I understood it is a low current compared to the total current draw.
> Want to figure out the smallest switch capable of doing the job.



From the data sheet it looks like not even 1mA goes into VDD (IDD typical is 200uA):
http://www.micro-bridge.com/data/ADD/AMC7135.pdf

Will


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## Walterk (Jun 24, 2012)

Thanks William! And the number is fine. It means you can switch any AMC7135 driver by using a small reed-switch.


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## eatkabab (Oct 15, 2013)

Excellent tests. Has anyone made such a graph/output for a single AMC7135 through at least the voltage range of a single lithium (4.2v-2.7v)? Preferably operating a single xpg, xpe, xre...


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