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Ben Solon

Fri Jan 06 2012, 12:28AM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600

Hey, i am starting to build this drsstc, and i need a few tips before i buy the parts.

Based on my gdt calculations, this: B64290L0618X830[epcos] core will work assuming 12v, 1uS, .2T, and 105mm^2. Can anyone tell me if this works? And then there is the secondary feedback. What specs should I use for those cores? Can I use more B64290L0618X830's?

Then there are the zener diodes. If my igbts, safe Gate to Emitter Voltage Pulsed rating is +-30, should I use 30v zeners? And if I have some 16v ones lying around, they wonâ€™t hurt because the threshold is 6v max?

And last, the bus cap, primary cap, and tvs diodes. Is there a place I can get all of them together cheaply? 30$ max? I donâ€™t need a huge 5000uF cap, only around 1.5-3mF. And the tvs only needs to be 400-500v, as I plan on the max bridge voltage being 340 and the normal voltage being 170.

Thanks, Ben.

edit: and for the gate driver, can i get away with dip package, or do i need to heatsink it?

Matt Edwards

Fri Jan 06 2012, 03:53AM

Registered Member #2838 Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333

CDE caps have proven to work vary well for most people I know. I have used them for several applications. Just make sure to properly calculate the needed voltage/current rating for series/parallel strings. Also, Stick with the 940-942 series polyester film.
Here is a link to the 940 datasheet

As for the bus caps I have only used RIFA so I cannot vouche for anything else.
As far as $30 for everything... Good luck!

Matt Edwards

Fri Jan 06 2012, 04:28AM

Registered Member #2838 Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333

Sorry to double post but I thought this might be helpful. I used TVS diodes 1.5ke220

as used by Steve Ward in his DRSSTC5.

teravolt

Fri Jan 06 2012, 06:09AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

hi Ben, I would recomend the to-220-5 drivers or you could have over heating. the ixdd414 has been replaced by

Goodchild

Fri Jan 06 2012, 06:22AM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

As already said the 940C caps are really the way to go even if your going to do it cheap. Your not going to find another option that is cheaper that will work in a DRSSTC effectively.

12V is not a good voltage to drive gates at all, in a DRSSTC you want a nice fast rise/fall times and a low Vsat in your IGBTs. I would recommend a 15V gate voltage minimum, 24V recommend.

Expect to spend a lot more than $30 for all of those items, even if you went with the cheap of the cheapest. I would check ebay for your bus cap the CDE and UPE (REFA) caps can usually be found for <$20 if you are lucky. Rell has been the cheapest place I know of that sells the 940C caps, but you usually have to buy in bulk. Mouser and digikey also sell the 940C caps but at a large mark up.

TVS across the bridge it's self is kinda pointless in my experience, usually all that is needed is a nice low inductance bus layout and a decent capacitive snubber.

Dr. ISOTOP

Fri Jan 06 2012, 06:58AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

A cap like so

should do, though shipping from that particular seller is sort of expensive.
If you're on a tight budget I would recommend sampling UCC37321/2's from TI.

Ben Solon

Fri Jan 06 2012, 09:11PM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600

Goodchild wrote ...

12V is not a good voltage to drive gates at all, in a DRSSTC you want a nice fast rise/fall times and a low Vsat in your IGBTs. I would recommend a 15V gate voltage minimum, 24V recommend.

OK, thanks for the tip. without any modifications to the circuit, can i drive everything off 24v? i am pretty sure that 40xx series cmos chips have a max of around 16v. if not i'll just throw in a vreg.

And i didn't think i'd get off that easy on cheap parts but its worth a try right =)

anyways thank for the help. but if anyone can tell me about the ferrites i would greatly appreciate it.

Thanks, Ben

Matt Edwards

Fri Jan 06 2012, 10:00PM

Registered Member #2838 Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333

You are going to want to use a voltage regulator for the IC's

Ben Solon

Sat Jan 07 2012, 01:16AM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600

Here is a quick schematic I made for board layout. Any new eyes to catch errors? I am PRETTY sure this is ok, and I had to make the ixdd614 part myself. But I know from experience that it is a pain when you finish etching a board only to find out you left out some simple but crucial detail.

Thank you everyone who is tolerating my questions, this is my first duel resonant!

edit: the 1n4004's replace the 4007's because they don't have a part lib in eagle

Goodchild

Sat Jan 07 2012, 01:18AM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

The GDT can be calculated using the universal transformer equation by throwing in 0.3T in for the the ferrite core. If you have that number in a datasheet use that instead as you will get better results from your math.

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