buck/boost circuit with LTC3113, 1.8V-5.5V max 3A ~96% effectivity

[srolesen]

hey i'd like to make a single cell tube mod with LTC3113 found here:
http://www.linear.com/product/LTC3113
datasheet

anyone know'smore about this chip, or alternatives, and if it's good for creating vaping bliss ?

 

[jhonutz]

ltc3872 i use and is good.you may try some free sample and test

 

[srolesen]

looks good indeed!
how do you implement it, and do you get enough power for all applications ?

 

[jhonutz]

i use 1 batt 18650 2000mah.work good with atty 2 ohmi or higher.PCB was made by me, i use a mosfet with gatethresold 1 -3V.

 

[srolesen]

Dont know if it's bad form to ask for schematics and stuff here, hope it's not
If you could post schematics, pictures and parts specific info it would be super cool
Im sure many people here would be as thrilled as me

 

[jhonutz]

Dont know if it's bad form to ask for schematics and stuff here, hope it's not
If you could post schematics, pictures and parts specific info it would be super cool
Im sure many people here would be as thrilled as me

all i can do for you is :

 

[srolesen]

damn lol, thx tho

 

[CraigHB]

.....en part, but a couple comments on that.

One thing that's going to give you hell in realizing a circuit is the type 3 compensation network that part calls for. Having designed several myself, I can assure you that's it's a pain to tune those things. If you look at page 17 of the data sheet, you'll see some formula for that. However, the formula only give you a rough estimation of component values. You need to do simulations and bench testing to nail values down. It's not something for the faint of heart.

Efficiency is "up to 96%". For the input voltages and loads you'd see with an atomizer, it's probably going to be in the 85 to 90% range a most of the time based on the efficiency chart shown in the data sheet. That's not bad, but it's not particularly good either. On my latest e-cig mod, I'm using a boost converter of my own design that can do 95% at 10W output. I prefer to use boost only myself. It's less complicated and you can practically get a range of 4-6V. Personally, I've never found a need for anything less than 4V.

 

[srolesen]

yeah 96% aint gonna happen for me lol, but it's nice to have the high theoretical max none the less-maybe someone can design something better ?
sad to hear it's gonna be problematic to use the chip, because my sweet spot is usually 3.9V for ce2 and 4.2 for cartomizers, esp the ce2's are much more enjoyable when batteries are slightly used than fresh off the charger.

if this is the hard and unpratical way of regulating power what is the easy one ?

 

[CraigHB]

Yes, it can be hard to build a DC-DC converter yourself.

Voltage mode controllers like the one you linked to are hardest to use in design, but are the most efficient. There are controller chips that use methods like current mode control to eliminate feedback tuning on the designer's part. Those are relatively easy to build, but you take a hit to efficiency. I don't know of any current mode buck-boost controllers off-hand. If you look for them on Linear's site, you can probably find a few. Chip makers realize what a pain it is for designers to tune feedback so some have come up with ingenious ways of eliminating the need. Check out the offerings from Maxim and Microchip as well.

You can get switching regulators like the PTN04050C and OKR-T/6 which have been discussed ad-nauseum in this forum already, but there are no buck-boost modules available like that, at least that I'm aware of. If you want buck-boost, you have to build it yourself. The buck modules you use with a dual cell mod are going to be most efficient for lower voltages. Though, you can put a Schottky diode inline with a booster to drop a half volt, but that's a big hit to efficiency. The diode blows off some power to drop voltage which is power draining the battery that does not power the atomizer.

 

[jhonutz]

from my experience step- down regulator is easy to calibrate, for step-up is hard, however like he said @CraigHB, if you test, and calibrate wright value,work fine. Very important is Cout, inductor, and Mosfet.

 

[srolesen]

I'm using a boost converter of my own design that can do 95% at 10W output. I prefer to use boost only myself. It's less complicated and you can practically get a range of 4-6V. Personally, I've never found a need for anything less than 4V.

how do you get 4-6V with boost only, i'd thought minimum on range on a freshly charged battery would be 4.2V+0.6V= 4.8V for boost only ?

 

[CraigHB]

Well, you get a some voltage drop from the circuitry when the PWM generator is idle. The generator idles when input voltage is greater than or equal to output voltage. In that case, it's like a straight connection from the battery to the atomizer.

For a booster that uses a diode rectifier (instead of a MOSFET), you get around a half volt drop from the rectifier. That's in terms of the straight connection from battery to atomizer when the PWM generator is idle. Usable range for one of those is around 3.7V to whatever the limit is on the booster.

For a booster that uses a MOSFET rectifier, you don't get that big drop so with the PWM generator idle, you get around 4.05 to 4.1 volts at the atomizer with the battery at 4.2V. Since battery voltage normally falls off quickly from 4.2 to 4.1V, you can get away with a 4.0V setting.

With a freshly charged battery, the first couple drags may be somewhat above 4.0 volts until the battery discharges a little bit, but it also depends on the battery. For something like a 14500, you'll get a lot of sag so even the first drag off a freshly charged batt can drop down to 4.0V. For something like a LiPo batt that has little voltage sag, you'll be running out of spec longer. Of course, this is only for boosters that use a MOSFET rectifier. Most boosters use a diode rectifier so you have lower range, but a lot less efficiency.

 

[srolesen]

hmm, didnt know that, changes stuff a bit, what solution would you recommend with MOSFET rectifier for a 18650 tube mod ?

 

[CraigHB]

Depends if you want to brave building your own boost converter or not. There's tons and tons of controllers out there you can use. I use a voltage mode synchronous controller (MOSFET rectifier), but those are most difficult to design. There are others that are easier to work with, but have various advantages and disadvantages. There are too many variants to list.

For a boost converter ready to go, the PTN04050C is the one most people use. Not sure if that one uses a diode or MOSFET rectifier. There's a few boost converters on eBay I've seen, but they all use diode rectifiers. The eBay ones I've seen look pretty cheap from what I can tell.

 

[srolesen]

Maybe just list 3 small formfactor ones with mosgets if you got some names ?

 

[jhonutz]

mosgets for you, buy PTN04050C from Texas Instruments it`s the best way for newbies in electronics stuff

 

[Youssefa]

Need a BIG mod for this one!

4-Way output Buck-Boost DC Power Converter Module 3A | eBay

Or this one
DC-DC Buck-Boost Converter 3-35V to 1.2-30V Module 2A | eBay

 

[jhonutz]

lm2577 module is not a good solution for modd`s. have higher dropout voltage.