ZLT-CCR2 PCBs

operator_smooth

Newly Enlightened
Joined
Feb 13, 2005
Messages
64
Does anybody have a PCB design for the ZLT-CCR2 regulator circuit that is the subject of this thread: http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=90380&page=&view=&sb=5&o=&fpart=1&vc=1 ?

I want to make an inductor for this circuit, but my knowledge about electromagnetics is very limited. I was looking at some toroid cores at http://www.elfa.se/elfa-bin/dyndok.pl?vat=0&dok=2011480.htm - can anybody see which toroid, if any, of the ones described there can be used to make a suitable inductor for the ZLT++?
 

Leeoniya

Enlightened
Joined
Sep 27, 2002
Messages
376
Location
Northbrook, IL
i was thinking of building a CCR2 sammie myself. I was reading up on some old and some recent ZLT discussions, lots of options described but no official "final parts list" thats proven to work well. it seems the Isense wire is very hard to adjust. that and inductor size are the biggest source of options and variation. i'm not sure if there is much choice as far as diodes or transistors, i think the FMMT618 was discussed but i'm not sure if anyone made the swap or the results.

If a final parts list can be produced, i can route the board and post it for those who need to. I'm thinking the indcutor can be fairly large cause i'll just route in onto the bottom of the heatsink on the other side. but i'll need to have the footprints for the components so i know how much area and volume i'm working with...

if MrAl or Newbie or pb wants to post a proven parts list and some alternatives for the inductor in varying but relatively close sizes in order of preference, i'll be more than happy to autoroute the PCB since i'm going to be doing that soon anyhow.

is there a good source for Coilcraft inductors yet? other than sample orders?

Leon
 

operator_smooth

Newly Enlightened
Joined
Feb 13, 2005
Messages
64
Actually I managed to get hold of quite a few parts for this circuit:
- zxsc300 chips
- fmmt617 transistors
- zhcs500 Schottky diodes
- some tiny x5r 10uF capacitors (ceramic)

For the inductor I was looking at the Ferroxcube TN 10/6/4 toroid core in the 3F3 material series, as it looks like it is small enough and has good permeability at ZLT circuit's operating frequency, 200kHz (?). I am not sure, however, that I understand the formula for inductance calculation. If N is the number of turns, does this mean that with 12 turns I get (12*12*740)nH = 107uH? How can I calculate the saturation current of an inductor made this way?
 

MrAl

Flashlight Enthusiast
Joined
Sep 9, 2001
Messages
3,144
Location
New Jersey
Hi there,

The toroid i used had a mu of about 5000 and it was 1/2
inch in diameter. If you select the 6000 mu toroid core
you'll probably be close enough.
The FMMT617 was used in most designs, along with the
Zetex 2000 Schottky diode (see their site).

As far as inductance and max sat current, you'll calculate
and inductance value but that will change because the tiny
core saturates for a short period of time.
The sat current will be fairly low for a small toroid like
this so it will look 'bad' at first, but the circuit
triggers on current so it's not quite as simple as with
a regular switcher with a linear inductor.

I'll post some more if you're interested.

Take care,
Al
 

Leeoniya

Enlightened
Joined
Sep 27, 2002
Messages
376
Location
Northbrook, IL
so you have to wind your own inductors these days to get good results eh?

well, no matter, as long as the parts can be sourced. it'd just be nice to plop a ready made one in there and let it rip.
 

gpk

Newly Enlightened
Joined
Jan 11, 2005
Messages
35
Location
Montreal, Canada

Leeoniya

Enlightened
Joined
Sep 27, 2002
Messages
376
Location
Northbrook, IL
wow, the "lost" page i was looking for... i always wondered what was on this google-found missing page everyone talked about.

is it just me or is it missing the 2 extra resistors for the Rsense network that was devised in the later development process of the circuit???

Leon
 

operator_smooth

Newly Enlightened
Joined
Feb 13, 2005
Messages
64
gpk, I was looking for a PCB design for the CCR-2 version of the ZLT - I can only see designs for the regular ZLT on the pages you refer to.
 

Leeoniya

Enlightened
Joined
Sep 27, 2002
Messages
376
Location
Northbrook, IL
...yeah, what he said....where's the Rsense network? i can just add them to the schematics and layout pretty easily i think based on MrAl's thread.

but a question....is it necessary to use the very long and narrow toroidal inductor? given the same material and a ferrite bead core, would it be possible to substitute the core for something stubbier and maybe wider? how would that affect the number of windings and wire guage? are there "donut" shaped choices for winding that inductor? what's the reasoning behind the selection posted in the article?

thanks
Leon
 

operator_smooth

Newly Enlightened
Joined
Feb 13, 2005
Messages
64
I don't think that the shape of the inductor matters that much, at least not at these frequencies. I bet that both toroids and solenoids of different lengths will do as long as they do not saturate at or below the peak current, as MrAl noted. By the way, check out this page http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/indtor.html - it has inductance calculators for both types.

If you could make some layouts that include the two additional resistors that would be really sweet.

As for the inductor... I am not sure if this is complete nonsense, but isn't it true that the saturation current through a cored inductor with a given size and number of turns of wire is descending linear function of the relative permeability of the core (air-cored inductors never saturate?), while the inductance is an increasing linear function of the same? In that case choosing a core with lower mu value and adding a few more turns should help increase the sat. current while maintaining the same inductance? What do you think MrAl?
 

MrAl

Flashlight Enthusiast
Joined
Sep 9, 2001
Messages
3,144
Location
New Jersey
Hello again,

I have a couple formulas i'll present for your use.
I also have a new calculator on the way which was originally
intended for the EE course as i dont like the way most
available free calculators are set up. It doesnt do
everything yet, but it does quite a lot so i'll be
releasing one version in a day or two or three...
that way folks will be able to enter things in and get
quick answers to problems like these.
For example:
Calculate_L(N,Ae,Mu,Length,Height)
(or something similar)
will calculate the inductance from the toroid core
with a number of turns N. You'll have to enter in
the dimensions but that's all.

But before we get to the formulas, i just want to
stress that these calculations are not that important, really,
because the small toroid saturates for a short time
and it stops because the ic chip turns the transistor
off, so it's not quite the same as most switchers that
use a linear inductor. Not that you cant use a linear
inductor instead...it's been done with success...but
you'll have to try a few or else talk so someone who
found inductors that work well with this circuit.
I found some that worked but the efficiency wasnt as
high as with the hand wound coil on the small toroid.

That said, here's the formula for inductance:
L = 1.26*N*N*mu*Ae*1e-8 /(gap*mu+ml)
where
L is inductance in Henries
N is the number of turns
mu is the permeability of the core (typically 10 to 25000)
Ae is the area of the core in square cm
gap is the length of the gap (single gap in toroid) in cm
ml is the average (mean) magnetic path of the core in cm


Since your toroid will not have a gap, this reduces to:

L = 1.26*N*N*mu*Ae*1e-8 /(ml)

If you want to know about the saturation, you'll have to
look at the manufacturer's data sheet on the type of
material the core is made from. You'll find some level
of flux (B) that will represent the max allowing some
temperature rise. You can use the following formula
to determine if the inductor will saturate...

Bdc=1.26*Idc*N*mu/(gap*mu+ml)

where
Bdc is the flux due to the dc current in gausses
Idc is the dc current in amps
N is the number of turns (wire goes through the center)
mu is the core material's permeability
gap is the gap length in cm
ml is the mean magnetic path in cm

With a gap of zero this reduces to:

Bdc=1.26*Idc*N*mu/(ml)

After looking at the magnetic data you'll determine that
there is some max B (which we'll call Bmax) where the
core is saturated enough to be called in saturation.
Then, you can determine if the level of Bdc goes over Bmax
or not by simply comparing Bdc to Bmax. If Bdc is greater
than Bmax then it saturates.

If instead AL is given, you can calculate Bdc from:
Bdc=N*Idc*AL/(10*Ae)
where everything is the same as above, and
AL is the value of inductance (L) for 1000 turns on the core.

By examining the above formulas and doing a few calculations
we can show that it is true that a core with lower mu will
be harder to saturate, but it's also true that it will take
more turns to produce a given value of inductance.
Same with adding a small air gap.



Ok, now that we're done talking about the calculations
I'd just like to remind anyone who's interested that
the small toroid will most likely always saturate, but
that's not always a problem in a circuit that senses
inductor current directly (as with the Zetex 300 chip).


Take care,
Al
 

operator_smooth

Newly Enlightened
Joined
Feb 13, 2005
Messages
64
What unit is the resulting Bdc in your formulas? I think that there is something in the datasheet but it is in mT (millitesla?) It says 330 mT?

EDIT:
Sorry, did not notice the line where you wrote that it is in Gauss. So I guess that an inductor made with this core with 6 turns (22 uH) will saturate at around 1 Amp or so...



By the way, what was the efficiency of the circuit that you made with your inductor? What was its inductance?
 

Leeoniya

Enlightened
Joined
Sep 27, 2002
Messages
376
Location
Northbrook, IL
okay, looks like i'm gonna wait for the calc.

is there something wrong with using an inductor design like the following picture instead of the long inductor core that's mentioned in the article? can I use this kind of inductor (possibly with more windings) and get the same results or are there factors that prevent this (saturation problems maybe or available core materials)?

p89-f4.jpg


i figure it would be easier to make into a pill than the oddly-shaped Mostaccholi one. and since i'm gonna route the board for the ZLT+CCR-2, i want to see how i can space the pads.

thanks,
Leon
 

operator_smooth

Newly Enlightened
Joined
Feb 13, 2005
Messages
64
To have something to experiment with I ordered an SMD inductor from Farnell (3631B220ML made by MEGGITT) - they have the datasheet here: http://www.farnell.com/datasheets/31236.pdf I will let you know if it works well for the ZLT... though it is not tiny, it may be worth the extra space if the circuit efficiency is decent.

Right now I can barely wait to get my hands on this and some other parts I ordered (zhcs2000 Schottkys, fmmt618 transistors and some resistors). I think I might start with the simpler ZLT design to test the inductors and then build the ZLT++.
 

MrAl

Flashlight Enthusiast
Joined
Sep 9, 2001
Messages
3,144
Location
New Jersey
Hello again,

operator_smooth:
Yes, the units for Bdc are gausses. 330mT would be 330 milliteslas, which equals
3300 gausses as you probably already know /ubbthreads/images/graemlins/smile.gif (1 Tesla = 10,000 Gausses)
If you post all the dimensions of your core and the permeability i'll double
check your calculations if you like.
The efficiency was about 85 percent or maybe 86. All the other inductors
came in around 80 percent, but it may be that i didnt get to try enough
other ones to make a good comparison. The mu of that core was 5000.
I also recommend building up a standard Zetex 300 circuit before converting
it into a ZLT-2, just so you know everything is working beforehand (as
you already intended to do).
Couldnt get your link to work however...it said the file
was not there or something.


Leeoniya:
Hi again, im not sure what inductor your talking about, perhaps post a pic?
That pic you already posted looks more like what i used. The number of
turns depends on what the mu of your core is...do you know what kind of
material that core is made of (the one in your pic)? And the exact
dimensions

Dimensions for the core are:

Outside diameter
Inside diameter
Height (as when layed flat on a table)


I'll try to find one of the cores i used and then i'll post the dimensions.


Take care,
Al
 

operator_smooth

Newly Enlightened
Joined
Feb 13, 2005
Messages
64
MrAl, the core I ordered is 10.6 mm outer diameter, 5.2 mm inner diameter and 4.4 mm in height. The relative permeability is 1800 (the 3f3 material) and the core factor Al is specified to be 740.

As for the link, apparently I put a dot at the end of the URL, I just edited that earlier post to correct this.
 

operator_smooth

Newly Enlightened
Joined
Feb 13, 2005
Messages
64
I have just built my first converter. I used a small toroid core left over from some earlier project. I have taken a picture and put it here: http://zhat.dk/pics/my1stzetex.jpg - I appologize for the poor resolution, my camera cannot focus at very short distance, that's why...

From some rough measurements with a DMM on the 10A scale (and the 20V scale for voltage) I calculated the efficiency to be 0.86, which rather surprised me. I believe that the core is MMG Neosid, material F19, I know I bought a few of these once... the mu is 1000 and the saturation flux density is 250 Gauss if the data I found is correct. So the inductor most definitely should saturate.

By the way, the capacitors on both in- and output are 10uF multilayer ceramic, and seem to suffice. Maybe even smaller input capacitor would do.

EDIT:
I forgot to mention that this is NOT the CCR-2 but more or less the standard circuit from Zetex Lighting Handbook design note 61.
 

MrAl

Flashlight Enthusiast
Joined
Sep 9, 2001
Messages
3,144
Location
New Jersey
Hi there operator smooth,

I'll go over the calculations and post results here either
a little later tonight or tomorrow morning.

86 percent sounds good /ubbthreads/images/graemlins/smile.gif

The sat flux being 250 on that material sounds way too low,
but im not familiar with F19 material so i'd have to
look that up too...i would have guessed 2500 instead or
in that region. The bottom line however is...
what is the efficiency...which appears to be very good for
your core. I'd use it! /ubbthreads/images/graemlins/smile.gif

BTW very nice pic even though your camera isnt set up to
take close ups. Sometimes if you need a really close
pic if you have a magnifying glass large enough to
cover the entire lense of the camera you can tape it
on or something, then using a tripod, get a decent
close up that way. Color isnt 100 percent, but it
works to some degree. I took many close up pics of ic's
where the ic filled the whole photo frame using a normal
50mm camera and an old magnifying lense i had laying around.

Cant wait to hear your results using the CCR-2 too.

I'll post again later or tomorrow as early as possible.

Take care,
Al
 

operator_smooth

Newly Enlightened
Joined
Feb 13, 2005
Messages
64
Thank you MrAl, I will try the trick with the magnifying glass tonight.

You were right: I misread the F19 specs table - it says 260 mT and not 260 Gauss.

Just got my stuff from Farnell and the toroids from ELFA, can't wait to try those parts.

MrAl, do you have any comments on the capacitors? Can smaller input caps (e.g. 2.2 uF) be used? As I see it, the input caps improve efficiency by reducing current peaks through the battery, but how much does this matter in practice?
 
Top