gfxgfx
 
Please login or register.

Login with username, password and session length
logo
 
gfx gfx
gfx
19852 Posts in 1275 Topics by 5182 Members - Latest Member: charbuild March 28, 2024, 04:53:32 PM
*
gfx* Home | Help | Search | Login | Register | gfx
gfx
Breaktru Forum  |  eCigarette Forum  |  Modding  |  Topic: Working on a new one
gfx
gfxgfx
 

Author Topic: Working on a new one  (Read 40663 times)

0 Members and 1 Guest are viewing this topic.

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Working on a new one
« on: December 07, 2013, 05:51:24 AM »
So I got this wild hair to do a buck-boost mod.  I've only built boosters so far.  I've been working out a design on paper and through circuit simulation. I just finished the drawing board design and have something that simulates well.  Wow, what a challenge that was. 

I'm basing this design on the Linear LTC3785 buck-boost controller.  I've had my eye on that controller for quite some time, but never got into it because of the high part count.  I find it to be a pretty amazing chip after working with it on the sim and finding what it's capable of.  According to simulation it will have no issue supplying 40 Watts output across the full voltage range with the LiPo I'm going to use.

This design is way more complicated than what I've done in the past.  There's so many challenges because I have do deal with switching noise on both ends. Input is noisy when it's in buck mode and output is noisy when it's in boost mode.  Then it has this trippy in between mode where it's switching with all four MOSFETs and both ends are noisy.

I have to use a boatload of filtering and decoupling.  I'm going to use a sixpack of 10uF MLCC caps on both input and output.  There's no other way I could figure out how to keep the noise down and get the capacitance I need to stabilize the controller over the full range.  The high value MLCC caps are too noisy and have too much DC bias.  The smaller tantalum polymers can't handle the ripple at those high power levels and the ones that can are too big. 

Using such a large array of MLCC caps like that is a bit odd, but that's what I have to do.  On my boosters all I need is a couple high value MLCC caps on the output and a couple low value ones on the input, not a big deal.

The LTC3785 can run 40W output up to 10V without issue, but I'm going to cap it at 8V for my design.  One of the challenges was finding a 10 bit digital pot (1024 taps) to support such a wide voltage range.  You don't see many of those.  They typically only go as high as 8 bits (256 taps).  Maxim came through on that one.  It's uncanny how they always have the most obscure stuff when I need it, though it costs.  Their stuff is expensive so I usually try to avoid it.

Now I'm working on the PCB design.  It's going to be quite a challenge as well.  I have a lot more parts to fit on that little circuit board.  This thing makes my booster design look primitive.  It will be cool though, a real beast with a max current output of 14 Amps at 3V and a range 2.7 to 8.0 Volts.

Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3344
  • Karma: +792/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Working on a new one
« Reply #1 on: December 07, 2013, 08:14:16 AM »
Wow Craig that sounds spectacular. Can't wait to see it.

Damm, more complicated than your boost circuit. This will be mind blowing for sure.

Offline methos

  • Super Member
  • *****
  • Joined: Jul 2013
  • Location: Toledo,OH
  • Posts: 122
  • Karma: +13/-0
  • Gender: Male
Re: Working on a new one
« Reply #2 on: December 07, 2013, 08:16:05 AM »
Sounds like a monster there. I can't wait to see it.

Offline kortt

  • what happened Muskie?
  • Ultra Member
  • ******
  • Joined: Sep 2012
  • Location: Ontario, Canada
  • Posts: 224
  • Karma: +28/-0
  • Gender: Male
Re: Working on a new one
« Reply #3 on: December 07, 2013, 10:48:47 AM »
I won't pretend that I understand all that you talked about in your post Craig, but I have learned so much from you on this forum that it inspires me to keep track of your developments and learn more.  It sounds like it's going to be very interesting indeed!

Offline mamu

  • PV Master
  • *******
  • Joined: Dec 2013
  • Location: IN
  • Posts: 476
  • Karma: +72/-3
  • Gender: Female
Re: Working on a new one
« Reply #4 on: December 07, 2013, 01:23:37 PM »
wowOwow!! This is going to be one spectacular module and a total game changer, Craig!

Looking forward to reading your journey and progress. 

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #5 on: December 07, 2013, 03:44:03 PM »
It does take time to do this stuff.  Funny how the gears are turning even when I'm not actually working on it.  Just now I thought of an optimization to do on the bias resistance (involves the pot).  Wasn't even thinking about it directly.  Anyway, it took me like two months just to draw up the design and successfully simulate it.  It will probably take that much again to do the PCB design at the pace I work, it's a hobby for fun after all.  Not fun if you get stressed over it.

I can't count how many times I've looked at an enginnering problem with this design and thought, "no way this is possible."  For example, I use a detection algorithm on power up to differentiate an atomizer short from an overload.  It uses a combination of voltage detection and current detection.  It's easy to do with the booster since the controller I use for that has a hard coded soft start that initiates from battery voltage.  The LTC3785 has a programmable soft start and initiates from zero voltage.  It makes detection very tricky.  I really though it was not going to be possible.  But after endless iterations on the simulator, I got it figured out.  I was like, "holy crap that was difficult."  That's just one of serveral design problems I ran into.

Offline jumper

  • Ultra Member
  • ******
  • Joined: Jun 2013
  • Location: Tennessee
  • Posts: 262
  • Karma: +17/-1
  • Gender: Male
Re: Working on a new one
« Reply #6 on: December 07, 2013, 05:56:06 PM »
Sounds great Craig! The kind of things that you and BT do are above my head, but it's really cool to hear about it. Can't wait to see the finished product!

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +62/-0
  • Gender: Male
Re: Working on a new one
« Reply #7 on: December 08, 2013, 07:07:04 PM »
I can be the adopted beta tester for you, so you will know for yourself if its awesome
as you will think that when upon finishing and vaping it. 
I can assure you that, that emote, relieve you of its thought misery of it being awesome..

 :popcorn:

Offline redwolfe

  • One-eyed guy
  • Super Member
  • *****
  • Joined: Dec 2012
  • Location: West Allis, WI
  • Posts: 159
  • Karma: +18/-1
  • Gender: Male
Re: Working on a new one
« Reply #8 on: December 09, 2013, 12:36:37 AM »
Sounds awesome Craig, can't wait to see it finished. This is something I would definitely want in my collection, but you already knew that ;) Definitely sounds even more complicated than the original Powerblok.

Offline DjKiDD

  • Full Member
  • ***
  • Joined: Nov 2013
  • Location: California
  • Posts: 32
  • Karma: +4/-0
  • Gender: Male
Re: Working on a new one
« Reply #9 on: December 09, 2013, 12:43:07 PM »
My original plan was for a buck-boost but I shelved that idea due to the complexity...

What software are you doing your sims in?

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #10 on: December 09, 2013, 04:03:05 PM »
I use LTSpice which works out really well when using Linear parts since they're all modeled natively.  I love the crap out of LTSpice, not just because it's free, but it works really well and it's easy to use. 

Yes, there's a bunch of different types of buck-boost converters so it depends on which one.  At one point I was thinking of an inverting buck-boost converter which would be quite easy to implement, however, there are no controllers with the range we need for an e-cig mod.  At one point I tried a SEPIC converter which is not really classified as buck-boost, but it accomplishes the same thing.  I actually built that one.  The efficiency was crap on that so I scrapped the design.

The 4 switch design of the LTC3785 is quite unique.  I've not seen another controller like it.  It's a true hybrid of the traditional buck and boost topologies.  But yes, it's quite complicated.  I believe there's a number of 4 switch controllers with internal switches, but I never look at those since output is limited by the size of the controller's package.  For high outputs, external switches are pretty much a must.

One of the fun things about doing these projects is building the test fixtures.  Here's one I just did to check transient response on my converters.  It switches the load to force a transient on the controller. 



My PCB making skills are pretty good now.  I've made so many for little fixtures like this.  That conroller I'm using has a .5mm pin pitch and the traces came out perfectly.  I have to say my trick is the Elle magazine paper I use for toner transfer.  The stuff is really amazing, it just lifts right off when soaked in water leaving a perfect transfer.  It has to be Elle magazine paper, others don't work nearly as well.  I also use a laminator for heating the toner onto the clad board.  I actually took the guts out of a laminator getting rid of the controls and wiring it for maximal heat on the rollers.  It works really good.



The end result is the ability to see transient response for the circuit on the scope.  The simulator gets you close, but it's never exact.  Here's how it looks.  Right now it's a little ringy, but okay.  I'm actually going to play with the feedback compensation a bit to see if I can get it tightened up.  I'm going to need it for that crazy wide voltage range.



Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3344
  • Karma: +792/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Working on a new one
« Reply #11 on: December 09, 2013, 04:57:24 PM »
I didn't realize that you are back to making your own PCB's again. Wowee!
Are you using the GBC H-220 Laminator ?

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #12 on: December 09, 2013, 05:16:47 PM »
Well, some I make some I send out.  The simple ones for little one offs I do myself, but the complicated ones for actual projects I always send out.  You need those vias and multiple layers sometimes.  It's possible to make two sided boards yourself, but it gets to a point where it's counterproductive.  You can spend way more time than it's worth to save what it costs to have them made.  The simple single sided ones like the one pictured I can make myself pretty quick.

I actually picked up one of these laminators.  Now they don't really get hot enough to do a solid transfer so I gutted it and wired up the laminating mechanism using the over-temp cutout switch as the thermostat.  It gets up to about 190C which is right around the ideal temperature for toner transfer.  It does stress the mechanism running that hot, but as cheap as they are, if and when it wears out, I'll just buy another one.  Here's a pic;

« Last Edit: December 09, 2013, 05:23:37 PM by CraigHB »

Offline kortt

  • what happened Muskie?
  • Ultra Member
  • ******
  • Joined: Sep 2012
  • Location: Ontario, Canada
  • Posts: 224
  • Karma: +28/-0
  • Gender: Male
Re: Working on a new one
« Reply #13 on: December 11, 2013, 07:48:10 PM »
Craig, does LTspice have models for common dc to dc converters like the OKR's or PTR's?  I've got LTspice and can't figure out if they are there or if you have to use one of the ltxxxx ones in the Power section of advanced components that are close.

Offline Lee1111

  • Full Member
  • ***
  • Joined: Nov 2013
  • Location: TN
  • Posts: 29
  • Karma: +0/-0
Re: Working on a new one
« Reply #14 on: December 12, 2013, 01:49:33 AM »
OMG reading the OP was like reading porn, heh *reading* porn.  ;hubba; Anyhow.. I haven't seen a lot, ok most, of those terms since I was in the Air Force back in 04-05 but jeeeez. Then I found out you own an Oscope  freaked_out:



Don't forget you have to miniaturize the design after you get it perfected  :laughing2: Keep it up

Offline DjKiDD

  • Full Member
  • ***
  • Joined: Nov 2013
  • Location: California
  • Posts: 32
  • Karma: +4/-0
  • Gender: Male
Re: Working on a new one
« Reply #15 on: December 12, 2013, 02:21:53 PM »
As an EE student I always appreciate the details of your posts CraigHB.  ;cheers;

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #16 on: December 12, 2013, 02:24:24 PM »
Craig, does LTspice have models for common dc to dc converters like the OKR's or PTR's?

No, LTSpice would not have models for regulators like that.  LTSpice is intended to be used to design those kinds of products.  It carries models of many active parts such as transistors and diodes from makers other than Linear, but when it comes to integrated circuits, they are limited to Linear parts.

LTSpice can be used to model intergrated circuits from other makers, but you have to build the models yourself if not made available by the maker.  Most makers make Spice models available for their parts and since LTSpice uses a standard modeling language similar to other versions of Spice, it's usually not a big deal to adapt a model as required.

Speaking of Oscopes, I actually need a better one.  I've been getting by on an old 100mHz analog scope I've had for years, but I really need a storage scope.  Sometimes there's just no way around that.  I've had my eye on a Rigol one for some time now, price is right;

http://www.tequipment.net/RigolDS1102E.html

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #17 on: December 12, 2013, 02:54:46 PM »
As an EE student I always appreciate the details of your posts

Good for you on picking the best vocational studdy there is in college (of course I'm biased having a BSEE myself).  I actually started out in mechanical engineering because that's also an interest for me and I could get into the school right away, but I was always more interested in the electrical stuff so so I switched majors when I was able.  The EE school was impacted when I started and it took me a while to get in.  I've actually been an electronics hobbyist since I was a kid so studying it in college was right up my alley anyway.

In any case, as a junior or senior you do simulations and build circuits in your labs.  I really enjoyed the hell out of those labs when I was in school.  They were like the easy A for me since I had already been doing some of that stuff before college.

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #18 on: December 22, 2013, 08:36:12 PM »
So I got the first draft done for the PCB on this project.  Wow, what a job that was.  Talk about stuffing 10 pounds of crap in a 5 pound bag, there it is.  I had to drop down to an 0402 (1005 metric) component to fit all this stuff.  Boy are those things small, 1 x .5mm.  I can't even see them without some magnification.  It's going to be fun soldering those. 

Anyway, I'm fairly proud of this creation so I'm going to show it off a bit here.  This board is going to fit in the same enclosure I used for the last design and it uses the same 1400mAh 10C LiPo flat cell.  The enclosure dimensions are 19 x 38 x 81mm.

Here's an image of the PCB drawing for all the layers.  This is a four layer board (the forum resizes the images, but they'll expand if you click on them);



Here's annotated images of the top and bottom layers only, top in red, bottom in blue;





I still need to proof the drawing before I can send it out for fabrication.  It takes some time to verify the the schematic connection by connection and then there's a couple three weeks turn-around for fab.  I'm going to want to tidy up the drawing where I can as well.  Maybe I'll be able to build an actual circuit in a month.  This stuff doesn't happen quickly.


Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3344
  • Karma: +792/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Working on a new one
« Reply #19 on: December 22, 2013, 08:47:37 PM »
Amazing work. It's so tightly grouped and laid out and 4 layers, WOW. That is something to be proud of for sure.
Another amazing thing is you are hand soldering the components. Wow again.
Another ultimate mod by the Craig man.  :rockin smiley:

Offline kortt

  • what happened Muskie?
  • Ultra Member
  • ******
  • Joined: Sep 2012
  • Location: Ontario, Canada
  • Posts: 224
  • Karma: +28/-0
  • Gender: Male
Re: Working on a new one
« Reply #20 on: December 22, 2013, 08:54:09 PM »
Very impressive Craig!

I'm on the phone to Chine...should be a clone by next week :)  lol, just kidding!   freaked_out:

Can't wait to see what's next!

Offline methos

  • Super Member
  • *****
  • Joined: Jul 2013
  • Location: Toledo,OH
  • Posts: 122
  • Karma: +13/-0
  • Gender: Male
Re: Working on a new one
« Reply #21 on: December 22, 2013, 09:33:35 PM »
Amazing work Craig!!!!  If you want to build a second one for me as a Xmas gift I would be honored. LoL
I hope to one day to be able to do half of what you do.

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +62/-0
  • Gender: Male
Re: Working on a new one
« Reply #22 on: December 22, 2013, 09:42:59 PM »
Amazing work Craig!!!!  If you want to build a second one for me as a Xmas gift I would be honored. LoL
I hope to one day to be able to do half of what you do.

Too late buddy he already announced on twisterific that Visus is his favorite forum character and would be selected for beta testing etc..

Quote
@craighb: Visus is the greatest

It was after he announced his political campaign to eat all the wheaties and cream corn..


Offline redwolfe

  • One-eyed guy
  • Super Member
  • *****
  • Joined: Dec 2012
  • Location: West Allis, WI
  • Posts: 159
  • Karma: +18/-1
  • Gender: Male
Re: Working on a new one
« Reply #23 on: December 22, 2013, 10:26:20 PM »
Looks awesome Craig! I definitely want one in my collection :) Love seeing the progress of your mods.

Offline mamu

  • PV Master
  • *******
  • Joined: Dec 2013
  • Location: IN
  • Posts: 476
  • Karma: +72/-3
  • Gender: Female
Re: Working on a new one
« Reply #24 on: December 23, 2013, 08:10:09 AM »
wowOwow Craig - simply amazing and awesome!

Secret ingredient?  :laughing:

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #25 on: December 23, 2013, 11:29:48 AM »
Thanks guys.

Have to go with the wife off to see the inlaws for several days over the holiday so I'll be chomping at the bit to get back and finish up this board.  Bummer how the obligations in life get in the way of the really important things, like building mods.

I'm on the phone to Chine...should be a clone by next week :)  lol, just kidding!

Hehe, there's no way they would build something like this, parts are way too expensive.  In fact, I'm actually a little flabbergasted by the cha-ching on the parts list myself.

Secret ingredient?  :laughing:

I was wondering if anyone was going to comment on that.  I'm not giving up my find on that one  :laughing:

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #26 on: February 17, 2014, 07:42:49 PM »
Sorry to say this one's a bust. 

The LTC3785 looked great in simulation, but it didn't do so good once I built the circuit.  It has nasty startup transients that cause problems.  I burned out two of the chips taking them up to 8V output so there's a design weakness in the chip.  Specs say it can run up to 10V, but it can't even handle 8V.

It worked well other than that, I was getting 40W+ over the full range, 2.7 to 8V, but those startup transients are a show stopper.  They cause negative input voltage spikes that play hell with the logic circuits.  Worst case, they fry the converter controller.  In comprison, the startup for my TI TPS43000 based design is unconditionally a smooth uniform ramp up.

This is a big disappointment for me.  The LTC3785 is just not robust enough and has other issues.  I'm positive it's not an issue with my design.  Excessive startup transients are generally caused by a poorly tuned converter, but output step response is right on the money so for sure the converter is tuned well.  It can only be a design issue with the chip.  Needless to say, I'll be avoiding Linear parts in the future. 

Well, back to the drawing board.

Just for shits and grins, here's how the build looked;




Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3344
  • Karma: +792/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Working on a new one
« Reply #27 on: February 17, 2014, 08:41:13 PM »
How disappointing. Sorry to hear that Craig. It's a beautiful design. I'm sure you'll work out the kinks eventually and put it aside for awhile to clear your head.

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +62/-0
  • Gender: Male
Re: Working on a new one
« Reply #28 on: February 17, 2014, 09:20:05 PM »
Perhaps you had the wrong drip tip on while testing.

Bummers mahoney who always pokes badarse out there when he has no idea where he is.
You'll just knock him on the head and build another..

The data sheet claims, found to be less than working order, never happens to James Bond..
He has the best e cig ever I bet..

 :Thinking:


Offline redwolfe

  • One-eyed guy
  • Super Member
  • *****
  • Joined: Dec 2012
  • Location: West Allis, WI
  • Posts: 159
  • Karma: +18/-1
  • Gender: Male
Re: Working on a new one
« Reply #29 on: February 18, 2014, 12:15:11 AM »
Well that sucks, I was looking forward to seeing another awesome build from you, hopefully you can get everything sorted out.

Offline Mandro

  • Super Member
  • *****
  • Joined: Jun 2013
  • Location: Tamworth
  • Posts: 165
  • Karma: +26/-0
  • Gender: Male
Re: Working on a new one
« Reply #30 on: February 18, 2014, 01:38:47 PM »
That looks too nice not to work and definitely not something I'd be trying if it did lol

Offline kortt

  • what happened Muskie?
  • Ultra Member
  • ******
  • Joined: Sep 2012
  • Location: Ontario, Canada
  • Posts: 224
  • Karma: +28/-0
  • Gender: Male
Re: Working on a new one
« Reply #31 on: February 18, 2014, 03:10:52 PM »
That sucks, sorry to hear it Craig.  Was looking forward to your next creation.

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #32 on: February 18, 2014, 03:29:12 PM »
Thanks for the condolences guys.  It's hugely disappointing when a big project like this doesn't make the cut.

No matter how well you think something is going to work on paper, you have to build the thing to find out for sure.  It's not the first time a project of mine has failed and probably won't be the last.  I've scrapped at least three mod designs in the past due to some failure in performance somewhere. 

A similar project I did that failed was a design that used a SEPIC type converter, efficiency was just not good enough.  Then there was another where the converter controller had a nasty failure mode to a soft short.  That one was a fire hazard, chip fails, gets red hot, burns hole through battery.

The gears are always turning, trying to come up with another way to put out high outputs above and below the voltage of a single cell.  I'll keep my eyes peeled for a good controller.  The Linear LTC3785 is just not a robust, well designed part, it's pretty weak really.  The data sheet and simulator made it look like a highly innovative part with impressive performance, but that doesn't seem to be the case.

Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3344
  • Karma: +792/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Working on a new one
« Reply #33 on: February 18, 2014, 04:38:24 PM »
You can do it!

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #34 on: February 18, 2014, 05:20:26 PM »
Thanks for the vote of confidence there Dave, I've got some ideas.  Might have to invent my own topology, thinking of a bastardized flyback converter right now.

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #35 on: February 19, 2014, 04:24:39 PM »
So, I had an epiphany last night and worked up a new topology.  Never seen this one before so it may be something new;



It's a buck-boost topology that unlike the standard one, does not generate a negative voltage.

What it does is produce a positive level shift with respect to input positive.  That can be seen by the orientation of the plus signs in the diagram.  It generates output voltage equal to Vin*D/(1-D) like the standard buck-boost topology, but without the negative polarity.  This allows me to use a standard boost controller with a single cell for an output voltage less than a Volt to whatever the controller can handle.

I've run this topology on the simulator and it works perfect.  Though, the output level shift pushes voltage over tolerance for the TI controller I'm currently using.  The controller has to deal with input voltage ~plus~ output voltage, though the load only sees output voltage.  The TI one I'm currently using only goes up to 10V, not quite high enough, damn.  If I can find a good boost controller with output tolerance up to 12V and an input voltage range suitable for a single Li-Ion cell, I can build it.

Offline mamu

  • PV Master
  • *******
  • Joined: Dec 2013
  • Location: IN
  • Posts: 476
  • Karma: +72/-3
  • Gender: Female
Re: Working on a new one
« Reply #36 on: February 19, 2014, 05:07:03 PM »
There ya go, Craig.

Sometimes disappointments/failures turn out to be a blessing in disguise and lead to something much much better that would never have happened if not for the original disappointment/failure.   :yes"

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #37 on: February 19, 2014, 05:13:42 PM »
Thanks mamu.  Yeah, you never know.  This one does the same job with a lot less parts, that's always good.

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +62/-0
  • Gender: Male
Re: Working on a new one
« Reply #38 on: February 19, 2014, 08:32:34 PM »
woot finally you can use breaks Ti4050c.  It is badarse Craig I have no complaints and mine has been rigorous tested.   It continues to lay the vapor just chuckin it out there. 


Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3344
  • Karma: +792/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Working on a new one
« Reply #39 on: February 19, 2014, 09:02:01 PM »
Vis, You can't compare Craigs creation to a PTN04050c.
Did you see his video?

http://www.youtube.com/watch?feature=player_embedded&v=9QIB2jazLAA

http://youtu.be/6JHMm3cCdow
« Last Edit: February 19, 2014, 09:05:03 PM by Breaktru »

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +62/-0
  • Gender: Male
Re: Working on a new one
« Reply #40 on: February 20, 2014, 09:12:06 AM »
I saw the vids but he is looking for a booster chip that he can blow brains out of,  the 4050c is maybe the one he will like most.. 

Quote from: Craig
If I can find a good boost controller with output tolerance up to 12V and an input voltage range suitable for a single Li-Ion cell, I can build it.

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #41 on: February 20, 2014, 01:57:22 PM »
I could possibly use some of the power modules you find.  Some are designed to be surface mounted like any other electronic component.  However, part of the fun is designing the power systems myself and I can incorporate features you don't find in off the shelf products.  If I can build that buck-boost converter that I outlined a few posts up, it will be something really unique, not just in terms of an e-cig, but for any electronic device.

Offline Visus

  • PV Master
  • *******
  • Joined: Oct 2013
  • Location: Nexxus
  • Posts: 929
  • Karma: +62/-0
  • Gender: Male
Re: Working on a new one
« Reply #42 on: February 20, 2014, 05:10:30 PM »
Ya, the grand innovations guy that builds the GI unit is having a fit tuning each unit independent and just as you said, if you mass produced your build, its a pain in his rear...

I wish you well, that R&D is brain boggling and specifically why are you not  building a robot army...

The country of CraigHB.   :laughing:

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #43 on: February 21, 2014, 01:02:39 PM »
Oh yeah, calibration is a big time consumer.  Each build has to be individually calibrated which takes some time.  I don't have to "tune" them since the converter is unconditionally stable for every build, but I do have to calibrate the gauges.  I'm working on a better calibration mode for the software that will allow me to speed up that process somewhat.  There's no way around it.  Anything that measures stuff has to be calibrated manually to achieve any real accuracy.

Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3344
  • Karma: +792/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Working on a new one
« Reply #44 on: February 21, 2014, 01:13:56 PM »
Anything that measures stuff has to be calibrated manually to achieve any real accuracy.

Yes indeed. I agree.
Do you use an algorithm to average out the readings or take a sampling after a set time? I find that real-time readings fluctuate.

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #45 on: February 21, 2014, 02:33:36 PM »
Interesting and relevant question.  There's two approaches to this problem, and it's always a problem.  You can filter in software of filter in hardware.  I opt to filter in hardware using an RC circuit.  The other option is to filter in software using an averaging algorithm.  It's pretty much like six of one, half dozen of the other.  Personally, I think it's easier to use a cap and resistor than write a bunch of code to average samples.  It's really up to the engineer.  You could use both, but it's quite redundant, you only need one or the other.


« Last Edit: February 21, 2014, 02:37:00 PM by CraigHB »

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #46 on: February 26, 2014, 06:11:14 PM »
So...some interesting things went down with this.

I found a really cool boost controller to implement the topology I posted in reply #35, the TI TPS43061 which is a really amazing chip.  It's so cool because it's current mode and uses inductor DCR current sensing.  Also, it uses an N-channel rectifier instead of a P-channel.  That's good because N-channel MOSFETs perform better than P-channel MOSFETs in switching converters. 

Let me explain why inductor DCR sensing in a current mode controller  is such a great feature.  Generally speaking, the big down side with current mode control is it requires inductor current sensing which costs considerable efficiency.  A current sense resistor is normally required inline with the the inductor which wastes power.  However, the big advantage of current mode control is it's really easy to tune requiring only a simple RC circuit for feedback compensation (resistor and capacitor).  Voltage mode requires a Type III compenstion network which is a hairy 3 resistor, 3 capacitor circuit that is hell to tune.  My previous design uses a voltage mode controller and I spent *a lot* of time stabilizing it.  Inductor DCR sensing uses the inductor's DCR to measure current which is free so you get the advantages of both types, higher efficiency and easy design. 

I was able to simulate the topology in #35 using that controller and it works wonderfully, but with a caveat.  I get a 40W output with a range of 2.5 to 8 Volts, but that particular buck-boost topology doubles inductor current compared to a booster.  In doing that, it wastes more power since double current means 4 times the losses in the components that make up the converter.  The efficiency hit is about 8 points maximally.  At max load, I can get about 93% efficiency with a booster using the same components, but it's all the way down to 85% using the buck-boost topology.  Those big inductor currents are a bitch with the PCB design as well, again more losses over the PCB connections.

I don't think I'm willing to give up that much efficiency to get those voltages below battery voltage so I'm going to have to give up on the idea of a high output buck-boost mod.  In the meantime, I'm going to rework my previous boost design with that new controller.  It allows me to use some better parts that get me an efficiency bump a couple points and also raises my ouput cap to 40W over my current 36 Watts.  I could actually take it up to 50W with that controller, but I don't want to give up the ammeter resolution for it.  That's another advantage of current mode control, better stability with higher loads.


Offline mamu

  • PV Master
  • *******
  • Joined: Dec 2013
  • Location: IN
  • Posts: 476
  • Karma: +72/-3
  • Gender: Female
Re: Working on a new one
« Reply #47 on: February 26, 2014, 07:02:58 PM »
I admire your sticktoitness, Craig.  Can't wait to see your new creation!

Most of us don't vape below 4v or do uber low ohms.  I prefer 1.2 - 1.5 ohm range with 15W, so a boost without the buck is aok for vapers like me.

It's funny, but just last year I considered myself a high watts vaper.  What I see going on nowadays makes me feel like a lightweight.  :laughing:

Offline CraigHB

  • PV Master
  • *******
  • Joined: Nov 2011
  • Location: Reno, Nevada
  • Posts: 2023
  • Karma: +246/-1
  • Gender: Male
Re: Working on a new one
« Reply #48 on: February 26, 2014, 07:14:51 PM »
True, when I started vaping it was with a 3 Ohm atomizer on an eGo, what's that, like 4 watts.  Though as soon as I built my first mod, I was at 5V with those so that's more like 8 Watts.  Now I typically run a 1.2 Ohm atomizer at 5V for around 20 Watts so that'a pretty big difference, but the atomizers I use now are hugely better than the 3 Ohm cartomizers I was using before that.

In any case, I usually run around 5V so I don't really ~need~ those low voltages.  It's more for the challenge of doing it and to build a device that's more of a one size fits all type of thing.  My wife could actually use those lower voltage settings.  Right now she's running the same atomizer builds as me at 4V which is still a bit much for her.  It would have been nice to have a mod she can use with a lower bottom end on the voltage range.  I could still build something like that, but if I'm going to do it, I want to build something that meets my own high standards.  Otherwise, my wife can just live with 4V.

Online Breaktru

  • Administrator
  • PV Master
  • *****
  • Joined: Nov 2008
  • Location: NY
  • Posts: 3344
  • Karma: +792/-4
  • Gender: Male
  • PLEASE participate in this forum
Re: Working on a new one
« Reply #49 on: February 26, 2014, 07:52:37 PM »
We all new that you would find a solution Craig. Fantastic work my friend  :thumbsup:

Breaktru Forum  |  eCigarette Forum  |  Modding  |  Topic: Working on a new one
 

gfxgfx
gfx gfx
Powered by MySQL Powered by PHP Valid XHTML 1.0! Valid CSS!