<DocScrutinizer05>
in bthe end you'll end with somthing that has 5 diodes in series, plus birdseed to make them work when in series, and that will look damn similar to villard
<DocScrutinizer05>
then come the capacitors ;-P
<whitequark>
hmmm right, I wonder how fat should they be
<whitequark>
1nF@2kV is trivial
<whitequark>
seems enough for my purpose...
<DocScrutinizer05>
what the heck became of diodes and transistors during last 30 some years?
<DocScrutinizer05>
anyway SMT and high voltage doesn't go together well. That diode has an isolation gap of <4mm. Sounds scary for a 2kV
<DocScrutinizer05>
and ideally you should use a graetz bridge. A flyback diode if you feel lucky and don't worry about efficacy
<eintopf>
hi
<DocScrutinizer05>
also you know that output voltage of those CCFL critters is absolutely not stabilized or warranted in any way? It may be 5 times overvoltage without rated load
<DocScrutinizer05>
maybe more
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<DocScrutinizer05>
either you want to stabilize the 2kV DC with a simple secondary->primary feedback, or you dimension your cascode ladder so it can cope with whatever your power supply feeds to it, and you use a feedback from output to control input there
<DocScrutinizer05>
I'd suggest the latter since you want it anyway to get a clean signal at output
<DocScrutinizer05>
anyway make sure your CCFL booster is at least specified to survive operation without rated load
<DocScrutinizer05>
for sec->primary feedback don't fall for the idea I just had for 3 seconds: abusing the cascode basis voltage divider. The cascode introduces massive load to that one, it's not stable
<DocScrutinizer05>
you need a dedicated high-Z R-divider sth 10:1 or 20:2 and an according 100..200V Zener
<DocScrutinizer05>
you could build a somewhat decent lod for your CCFL booster with that divider as well
<DocScrutinizer05>
load*
<DocScrutinizer05>
you don't want "floating" outputs with undefined or zero load when it komes to kV
<DocScrutinizer05>
comes*
<DocScrutinizer05>
((output voltage of those CCFL critters is absolutely not stabilized)) that's actually by design, they are meant to provide a certain current or a certan power, depending on what you want them for. Neon is constant current, FL is constant power
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<whitequark>
DocScrutinizer05: ah I see, thanks
<whitequark>
I was going to surround it with an overall feedback loop
<DocScrutinizer05>
feedback sawtooth to 220V input of CCFL converter?
<DocScrutinizer05>
;-)
<whitequark>
feed the primary with voltage-controlled PWM from opamp output. feedback from divider to - input, filtered PWM from controller via optical isolation to + input
<whitequark>
divide it 1000:1
<DocScrutinizer05>
you cannot "dim" those CCFL converters
<whitequark>
no, not a CCFL converter
<whitequark>
a CCFL *transformer*
<DocScrutinizer05>
that's the same
<whitequark>
how so?
<whitequark>
it's just a regular transformer
<whitequark>
I've seen the DS
<DocScrutinizer05>
well, you cannot PWM a transformer, right?
<DocScrutinizer05>
I mean it's meant to work with 50Hz sine wave
<whitequark>
hm
<whitequark>
I don't know how this mode of operation is called in english
<DocScrutinizer05>
you can try to dim it with usual phase-end-enabling triac dimmer
<whitequark>
ah, what I want to make is essentially a class D amp that feeds the primary
<DocScrutinizer05>
but I strongly discourage that
<whitequark>
what do you think of my class D amp feeding sine to trafo idea?
<whitequark>
so, then it would have two feedback circuits. one to keep 2kV DC, another for the cascode ladder
<whitequark>
DocScrutinizer05: anyway I already decided against using CCFL trafo
<whitequark>
for the reasons you have listed above
<whitequark>
but it applies just the same to the balun thing
<DocScrutinizer05>
I'd use a simple on/of feedback for the Vdd, however you build it
<whitequark>
hmmm, so feed it with fixed sine, then use a comparator to enable?
<whitequark>
that makes sense
<DocScrutinizer05>
yeah, and a triac/dimmer to only switch in zero crossing
<DocScrutinizer05>
if you feed it with AC. Simple on7off for any balun-thing
<whitequark>
talking about sine, do you think I could use the primary itself as half of LC filter, and feed the filter with rectangular pulses from a FET?
<whitequark>
I don't have AC
<DocScrutinizer05>
when you don't want to use the half-bridge balun-thing, you prolly want to go for a traditional SPSU primary side design
<DocScrutinizer05>
using any chip of your choice made for that
<DocScrutinizer05>
there are like a million to choose from
<DocScrutinizer05>
I'd not build some unique homegrown solution for that
<DocScrutinizer05>
we discussed that recently here, with err I forgot who planned to build a power supply for 12V or sth
<whitequark>
hm, I never used any SPSUs with a trafo
<whitequark>
only with an inductor
<DocScrutinizer05>
add a second coil and you got a trafo
<whitequark>
well yeah, that's essentially same thing as I want
<whitequark>
could reuse an existing chip, maybe even with integrated FET
<whitequark>
and feed it back via a bigger divider
<DocScrutinizer05>
yep, exactly
<whitequark>
for 200V should be simple
<whitequark>
I think in computer PSUs they optically isolate the secondary from primary? not sure how to do that
<DocScrutinizer05>
there are also pretty cheap 12V->220V-AC converters ready made out there
<whitequark>
I mean, optically isolated feedback
<DocScrutinizer05>
optocoupler
<whitequark>
ah, no, I think it goes the other way
<whitequark>
they only have FET on primary side and everything else is on secondary side
<whitequark>
ehh, I'll do my own, it doesn't seem very hard
<whitequark>
also will get SMPS experience :p
<whitequark>
one more thing to debug, but it's not like I have a deadline
<DocScrutinizer05>
fine then, taking pride in DIY is the right spirit ;-)
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<whitequark>
DocScrutinizer05: I just realized one thing
<whitequark>
you were saying you need to drive a trafo with sine
<whitequark>
however an SMPS doesn't do that even nearly
<DocScrutinizer05>
I said it's supposed to be powered by sine in your particular component
<DocScrutinizer05>
when you don't use sine, you get differing results on behavior
<whitequark>
ah, yes, I understand that
<whitequark>
but does it really matter if I have feedback anyway?
<DocScrutinizer05>
trafos and inductivities have a number of properties and those determine what you may and may not do with them and what are the results you see
<whitequark>
as in, it will work in a drastically different mode than it is supposed to