Voltage boost DC to DC converter

[rkcstr]

Hey wannaburn,  not intended as an attack on your work, but that assembly looks horrendous.  PWM/PFM circuits, unlike linear circuits, don't just require the proper parts to work well, but component and trace layout can have a significant impact on function.  For all I know, your design *could* work well (would say out of luck, in that case), but it more than likely is impacting efficiency and possibly inducing oscillations into the circuit.  Have you looked at the output on an o-scope?

As I said, I don't want to attack your work, but to make you aware of the potential problems of improper layout, not to mention that any of those joints may weaken over time leading to catastrophic failure.

 

[phoenix3200]

Got a link w/ more info on that rckstr? I'm quite close to ordering some double-sided demo boards for use with a PWM chip and would rather get it right the first time.

 

[rkcstr]

Well, basically because of the high-frequencies of operation, those leads or thin traces may act like an antenna, and when you basically have radio frequencies emitted from one "antenna" it can then be picked up at another "antenna", which can induce noise or other effects into the circuit that should not be there.

Layout should be so that traces are as wide as possible to avoid the "antenna" effect and there should be a ground plane to absorb any self-generated RF or even outside interference. There are also other considerations, but here's some articles I found on Google which talks about some of this stuff:

http://www.egr.msu.edu/classes/ece480/goodman/spring08/group05/docs/High_Freq_PCBlayout.pdf

http://www.analogzone.com/acqt0729.pdf

A very in depth article from National Semi:
http://www.national.com/an/AN/AN-1229.pdf#page=1

 

[yag-222]

I will recommend you the fantastic drlava FlexDrive which will boost up a mini of 2.5V to the required voltage at a selectable current in order to drive red or blu-ray diodes...

Here is to the order page :

Just add h1t2t3p4:5/6/7
hacylon.case.edu/ebay/laser_diode/Micro_FlexDrive.php

and here is the link to the driver I will soon use in my next blu-ray pointer, using a wickedlasers "core" housing with two AAA batteries (this one is a bit more expensive but seller will provide you all the help you may need, trust my experience ;-) :

Just add        h1t2t3p4:5/6/7
cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWNX:IT&item=320307467684

It will remember you something lasersbee and jake21...

Good luck in your project !

 

[rkcstr]

I think everyone here knows what the Lavadrive is... its designed/sold by DrLava, a well-known member here.

The second one is the same as the one Wannaburn has up there... I'm assuming that's his Ebay selling account.

 

[JLSE]

Thanks for the compliment?

This boost is the same as the one (similar as in the IC) as what IgorT uses in his builds. He obviously does not use the same layout, or parts, but none the less, you may want to ask him the advantages of this IC over that of Dr.Lavas when it comes to the 803's.

From what he has decribed to me is that Lava's drive is excellent under perfect conditions for a 6x diode. But the flexdrive has one near flaw, that is when driving an 803t it is pushing its absolute max voltage to the diode. Where as this diver can boost up to 24v The 6x diodes need only 4.5v or something along those lines, where as the 803t requires around 5.5v. I have had three flexdrives kill 803's with an unexpected flicker of death. That driver is meant to operate under perfect conditions IIRC. I have about 60 PM's from Igor discussing this driver vs the flexdrive and help in developing which he so kindly assisted. If im missing any facts, you could just as well ask him as he is much more well versed on the topic.


As for my layout, it is the same as Woop's, I have made my own adjustments to it, as his original post was for 15mW or so. I also have a sample out to another member, who has offered to test for ripple and other annomalies one would expect from this type of driver.

I have an 803t in a pointer putting out 185mW, tested 5x a day using it appox 15hours a week for durability tests. I have made 25 different lasers using this setup and test them daily also,

I am still waiting for the first one to fail

 

[rkcstr]

I never said anything about Dr Lava's driver being any better than yours or any comparison at all.  I know his driver has limitations that may not be very explicitly stated, which I am sure many DIYers would probably never figure out otherwise.

As for your driver, I didn't say anything about how it ACTUALLY DOES function, just that it looked like it could potentially have some issues associated with high frequency operation and component placement (you have components soldered over other components).  Also some of those solder joints look like they could weaken over time (specifically the leaded components soldered to surface mount pads).  You've been making these for what?  6 to 12 months?  The failure I'm talking about could be years down the line.  Sure, most don't think that far ahead and who knows if they will even be using the thing that far down the road, but its better to assume that to be true than not.

Trust me, if a real circuit engineer (which I am not) looked at that, he would probably have much more to say than I did.  What I said was meant to be a constructive criticism and if you don't want to take it into consideration, that's fine, I just thought it could be helpful.

 

[IgorT]

You know, i never did say i found the reason for your problems. For a while you had me convinced it's the drivers, and i asked an engineer friend why it would happen, and he proposed some theories, which i passed on to you as possibilities...

I had some problems initially too, but it was my mistake for not using an extra input cap when powering from a PSU. It really scared me to see the current jumping all over the place, and it made me think you were right. But a simple input cap and/or using a battery solves it. Besides it can not happen inside a laser. As for the voltage, i have since verified that it works up to 6.5V reliably.

I mostly use FlexDrives in my red builds, but also in some blu rays. I leave the extra input cap on and by now i trust them as much as any other driver. I haven't had any problems with any of them yet.. There are numerous possibilities for something to go wrong, it's not necessarily the driver. Not least of all, it can be operator error, which i have been guilty of myself quite a few times. And if you think back you will remember that was my first suggestion.. And the second, and the fifth.


I still don't know what was wrong with your diodes or drivers, i told you about many different possibilities. One of them was the dummy having a too high Vf, or powering without a load, none of which is good for a boost driver.

 

[JLSE]

Its weird because the same problem I was having happened to a handheld many days and many hours of use after a dummy load was connected.

BTW the problem I was experiancing with the dummy load as you recall was with the woop circuit. I had not noticed the blown fuse in the meter there was no load on the drive, and the other thing was not enough diodes in the dummy.

All the same, I enjoy my DIY drivers much more.

 

[IgorT]

The dummy load could have a Vf so high, that it could damage the driver. The driver will always try it's best to push the set current through the load. If the Vf of the dummy is too high for the driver, the driver can damage itself by boosting too high. It gets even worse, if such a driver is left running unloaded, because then it wants to push the current through air, and no driver can boost that high.

In that case, the damage could theoretically show up at a later time, under more stressfull conditions, like when the Vf of the load is high due to low temperature.

Another reason for the Vf being too high is of course the high currents we use on these diodes. The higher the current the more voltage the diode will need. If you overdo it, you can push a driver to it's limits. But this one time i made a mistake, and i forced a FlexDrive to push 450mA through a >6.5V dummy load for a long time, while adjusting it. I forgot to switch the dummy into the "red range". And surprisingly enough that driver is still alive. So i still don't have a clue why you were having so many problems with them.


The diode Vf being too high theory was suggested by an engineer friend of mine, when i asked him what the problem with your setup could be. But it was just from reading the datasheet, not from actual tests. When you told me it's the drivers fault at around the same time, i started believing it and looking for reasons. It worried me even more, because i recommended it to numerous people before that. But i have since done many tests (on purpose or by accident), and everything still works just fine.


I enjoy making my own drivers too. But occasionally it's easier for me to use a ready made one.

And for people, who don't have the required tools to make and then trouble-shoot their own high frequency switching driver (like a digital scope), it's definitelly a lot safer to use one, that was designed and troubleshooted by somebody with the required knowledge and experience. So when someone asks me for a boost driver, i still recommend the FlexDrive, but now i also tell them what not to do, based on my experience.

I don't know what the problem was with with your setup.. I was proposing different theories before testing the drivers myself. But except for when i did something wrong (too long wires, PSU instead of battery, no input cap), i couldn't replicate what you reported to me in my tests. My main theory was and still is, that your dummy was too much for your drivers.. Or you were making the same mistakes as me. I doubt i will ever know for sure.

But i have a FlexDrive powering a 4x diode here, and even tho this one needs more voltage than a PHR, it's been working fine for almost 60 hours continuously by now. I wouldn't use it in a test setup if i didn't trust it.

I used several of them by now, and i have not seen a problem with them yet. I just ordered five more for various builds a few days ago. Mostly for red lasers, or for when i don't have much time and have to make something quickly.

 

[chopper]

I'm going to get a couple flexdrives, but I too would like to build my own boost driver.  Do you guys recommend any specific design?  i.e. the Kage schematic posted on page 1 or the Woop design?  I'd like to take a design and (while learning about it) design my own pcb to have made.  I was looking at the Woop design with current monitor for case grounded diodes, but I wanted to make it current adjustable.  My only problem is that I haven't figured out the circuit enough to know what resistor to replace (Rsense?) and what values to choose for Rin and Rout.  Any good resources to learn more about this type of circuit?   I have access to scopes and such at school, but I'm a physics major so my EE chops aren't quite polished.

Btw, Rkcstr thanks for the links about high frequency circuits too!

Thanks for the help!

This is the Woop circuit I was considering:

 

[phoenix3200]

You only need to worry about case ground if you're using a non-803T.  That being said, on the original Woop driver, if you used a 2 ohm resistor in series with a 10 ohm pot (look on Newark - I found a good one for $2), you can adjust the current to up to 250 mA, and down to 40 mA.

As for Rin and Rout, look up the datasheet on the LT6106 (link).

 

[yag-222]

Lol !! Hey rkcstr, was not claiming that nobody on this forum know the FlexDrive, I just saw it was not mentioned in last posts... I think every body here know his fantastic work...

Hello wannaburn, world is very litle... Nice to meet you on this forum, thanks for the explanations about the reliability of drLava driver for 803Ts, it support the choice I make for your driver. FlexDrive will be usefull as soon as I can found one of these 6x diodes. Your experiment with your driver reliability is very interesting too and... 185mW !! Impressive with the use you make of them.

Thanks for your support...

John

 

[IgorT]

Yag: I have a FlexDrive powering a 4x diode, which is a much heavier load, than any PHR, and it's been working for almost 70 hours continuously by now without any problems. I have also made several PHR lasers with it, and never had any problems. Unless of course the current was so high, that it killed the diode, but that is not the driver's fault.

The output voltage being too high was just one of the theories proposed by an engineer, when i asked him why WannaBurn could be having so many problems. For a while i believed that there really was a problem. But i have since tested 9 FlexDrives under much harder conditions, and i couldn't replicate the problem.

There are hundreds of people using it with a PHR daily, and they don't have a problem. If there was an issue with three out of five drivers, everyone would notice by now.

Another theory was, that the test setup was damaging the drivers, especially since there was a meter between the driver and the diode, which is not very safe. If multiple drivers fail in one test setup, but a hunded others work fine in other setups, the cause is usually in the setup itself.


There is nothing wrong with the driver you bought from WannaBurn, if he added the suggested filtering. But there is also nothing wrong with FlexDrives, when powering a PHR. The driver WannaBurn is using could power three PHRs in a row, but with only one, there is no practical difference.

 

[JLSE]

Really I cant remember in what order I had issues with the lava drives, but they were not all being tested at the time the issues began that was the woopdrive. You had also mentioned something of length of wire to the drivers input and out to the LD.  I set all of the drivers to 180ma, and powered them with 3.6v lithiums assembled and working in a host.

On the first handheld to fail, turned out the diode was okay and the driver was not. Another was the original lavadrive kits, twice the size as the ones we know now. That one was fine until I moved the laser into another host using 3 1.5v AAA's instead of a single 3.6v, all I heard was a high pitch squeel and that was it, no more nothing.

Im not sure with that one because it was assembled by me, and there is room for error on my end.  And the last one to go was in a DX greenie pointer case, I was using it many hours per week, and when its time came, flicker of death as you put it, and both the diode and driver no longer worked With that one, the diode could have failed followed by the driver, not sure. I have another that still works fine, just no soft start anymore. :-?

Now im nowhere near as fluent in electronics as some on this site, but honestly I never put much thought into the details of why, rather than how to do my own ;D.

What I dont understand is why all of a sudden you change your mind on the benefits on this arrangement, where you had me sold on how good it was. I didnt go this route with the idea of it being better, but chose to go through the fun of making my own, and of course to avoid the additional costs

As for others having the same problems, maybe some members who drive their 405s higher than 180ma could share their experiances? I know there are others who like to push the envelope as well, but as you said, may feel the failures came from the high current.

All I know, is as far as this driver goes, all the higher efficiency diodes that I set to 180ma (give or take the tolerance factor) are alive and kicking, putting out a more stable mW than any of my 405's using an LM317.  Everytime I test them, I graph them and compare the charts, and see a consistent flat line at the top of the graph with very little wandering and a nice stable output.

Apples and oranges I guess, and for the filtering I changed the cap to a 100uf across the LD, but have to get it tested on a scope. My original layout had 30uf total on the out and only came in at 10mV ripple, and did not summon alien beings

 I have changed the layout to include additional polarity protection and some other items suggested by IgorT. I will keep making the changes until I get this perfect, or as close as possible.  :

Lol !! Hey rkcstr, was not claiming that nobody on this forum know the FlexDrive, I just saw it was not mentioned in last posts... I think every body here know his fantastic work...

Hello wannaburn, world is very litle... Nice to meet you on this forum, thanks for the explanations about the reliability of drLava driver for 803Ts, it support the choice I make for your driver. FlexDrive will be usefull as soon as I can found one of these 6x diodes. Your experiment with your driver reliability is very interesting too and... 185mW !! Impressive with the use you make of them.

Thanks for your support...

John

I wondered why that name looked familiar : Good to see you on the forum,
lots of info for all and a great place to try some new things. The 6x diodes are
currently quite expensive, but the price is dropping, around 250. average for now.
It is a definate worth while project if you can shake the nerves of getting the diode out ;D
Hope to see your projects in the future, everyone hear loves a good beamshot and lots and lots of pics.









@IgorT below
Sales pitch? Ahhh, last time I checked, you were the one pedalling your wares on this forum, not me. But if that makes you feel better about it all, than enjoy [smiley=thumbsup.gif] I dont link to my sales, and come here to discuss LASERS, not how much I want for my sh!t.
 

 

[IgorT]

I didn't say there was anything wrong with the driver you are using now. I recommended it to you when you were looking for an alternative, and i told you how to use it. It is my favorite IC. I didn't say it's not good. If it wasn't, i wouldn't be using it. But i have four different versions of it running various lasers.

I'm just saying, that one of the proposed theories about your problem - the one you are using as a sales pitch now - was wrong. And you know that. After you told me what was happening, and pretty much convinced me it's the drivers, i ordered several FlexDrives myself to test and hopefully use them. At the first attempt, i thought "omg, he was right". But it turned out my switching PSU was causing problems, interfering with the driver, and making my dummy load blink (since it has a LED for visual feedback) - the blink reminded me of what you described and i thought there really was a problem.. But i asked Lava about it and he told me what i was doing wrong.

I have not had any problems since i started using only batteries and short wires. The worst thing that happened to me with a FlexDrive after that, was that the wiper fell off one pot. And that even tho i made one push 450mA through a >6.5V dummy load for a minute by mistake once! The driver not only survived this, it even managed to keep the current stable throughout this time. And that was a much heavier load than any diode we have available at the moment.

By now i trust the FlexDrives as much as i trust my own drivers. I was doubtful for a while, because of everything you told me, but you can be sure that i tested the drivers thoroughly before using them in any lasers. Now i'm even using one in a lifetime tester for a 4x diode.


Keep in mind, that your "WoopDrives" were dying too, one after another, until you found a problem in your test setup. The same thing could have harmed your FlexDrives and caused them to malfunction. Boost drivers like these are sensitive to certain things that linear drivers just don't care about. It's two completelly different worlds with different rules. Issues that wouldn't harm your 317, can make a boost driver go up in flames. The high pitch squeal is a sign of a boost driver working too hard. Like when it tries to push the current through an open circuit. The sound comes from the inductor vibrating as the IC changes the modulation. That's the same thing that killed your first batches of WoopDrives. That's why i kept telling you not to put the DMM between the driver and the load, but to use a 1ohm resistor instead..

Also, at 180mA there does not have to be a problem with anything, for a PHR to die. I had to kill 15 to find one that could survive 160mA.
I often saw these diodes flicker as they died. But it happened the same way on any driver.