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.p...ok=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++?
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?
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?
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.
The hand wound inductors work great for me, I think someone mentioned larger capacitors are better? 50uf +? MrAl is the man to ask...
Do a search on posts from me "gpk", I got some great answers to my questions...