Using a dual-inductor line filter as a DC-DC transformer?

CMCs are only good for about 1-2W. If that's all you need, then go for it.

Hardly any need for current limiting either, thanks to the huge leakage. Just make the driver a little oversized. It's "impedance protected" like all those tiny AC motors! ;-)

Wowww, that schematic is laughable. ATtiny instead of a 555. Driving an IXDD604. Guessing they don't know their asses from their stack of cookbooks. Wait, the fine print says "from Instructables"? The closer you look at it, the harder you laugh...LOL!

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:

You could buy a complete pottted dc/dc converter for a few dollars. There are also reasonably priced converters rated for kilovolts of isolation.

It's fun to design stuff, but dc/dc bricks are cheaper than you can buy the parts.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

I like the +20,-4V 100mA modules from MornSun (QA01C) and MPD (IG120-20). 3.5kVac. Same pinout. Only 3.5pF of I/O capacitance! Nice. About $6 qty 10.

--
 Thanks, 
    - Win

That's nice, two high-isolation supplies in one brick. Just right for powering opamps, too. Sometimes just a little negative voltage is all you need.

I use the single and dual CUI bricks even when I don't need isolation. This one is slick:

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Actual gate current about 200-300 mA with 12 VDC open circuit. So maybe

2.4-3.6 watts, but if the impedance causes the output voltage to drop (without much power due to inductance) then it might be fine.

That is actually an earlier version of the AC controller sold by PaulAndSabrina, for DIY EVs, and apparently they work quite well:

The ATtiny (or an equivalent Microchip PIC) is really a much better choice than a 555 because you can program the dead time between alternate square wave pulses. The cost is comparable, and rather insignificant. The IXDN604, with 4A output and only about $1.80, is also a pretty good alternative to a four-MOSFET bridge.

Paul

The 480 VAC mains presents a special problem, which requires a "reinforced" isolation having a physical barrier between the windings capable of safe operation. Here is more information:

Previously, the only DC-DC converters I found with such specifications were these, which are $40 or more:

or

Note that only the first one is rated at 4800 VAC and suitable for up to

1000 VRMS working voltage. A 3000 VAC rating is supposedly only rated to 300 VRMS continuous working voltage. That unit is 5VDC output at 600 mA, which should be fine for SCR gates that typically are about 1 volt at that current.

For IGBTs, SIC, and MOSFETs, Murata has some good modules for about $24 each:

Paul

Murata also makes some nice 2W DC-DC converters for IGBTs, MOSFETs, and SiC devices (about $8):

Paul

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Lots of choices. Quote: "Ultra low coupling capacitance", but they don't give a value. 3.5pF is sweet spec value.

--
 Thanks, 
    - Win

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I think you'll find the choke cores don't have much of a volt-time product because in the typical application the differential voltage induces zero co re flux and the common mode operation is at relatively small voltages. Anot her problem is they should be using core material formulated to be lossy at high frequency- similar to suppression beads.

I posted a comment on the DIYelectricCar forum and got a reply saying that these chokes worked for him and he found they handled a hipot test up to 6 kV. However, he seems to be using a larger version, something like this:

Here is an image of the populated board showing these inductors:

Paul

The worst parameter is going to be the high loss factor. Let us know how it works out for you. A design note on KoolMu CMC design with leads to other references:

I provided test results in my other thread, but just for continuity and relevance, here they are again:

Here are the results for the KEMET common mode chokes:

L(10 kHz) = 1.28 mH L(leak) = 15.8 uH R(10 kHz) = 2.41 ohms R(100 Hz) = 0.225 ohms

At 90 kHz:

12V 0.22A 2.64W 9.31V 0.282A 2.62W 99%

At 71 kHz:

12V 0.24A 2.88W 9.66V 0.293A 2.83W 98%

I added 0.01A to the input current to avoid going over unity ;)

Seems like this common mode choke is actually quite capable of being used as a 2W DC-DC converter for a current souce like the

SCR gate drive, or the low average draw application of MOSFET or IGBT drive. And it is also a cheap $0.89 part.

Thanks,

Paul