1100W 450V Powersupply - Topology and Core - diyAudio
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Old 21st June 2013, 10:24 PM   #1
cjk2 is offline cjk2  United States
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Default 1100W 450V Powersupply - Topology and Core

I am currently working on the design of a 450V powersupply. I need 2.5A at 450V as the output. The input is 400V from a PFC circuit.

Is an ETD44 core large enough for this application? I calculated that a 30 turn primary at 70kHz gives <0.2 Tesla flux. I have rarely seen people push 1100W through an ETD44 though so I am questioning if there is some other problem I will run into. I can fit enough wire on the core for 500 circular mils per amp so perhaps all will be ok.

I originally wanted to do an LLC topology with the resonant inductors as part of the main transformer. If I go this route I want to use a UCC25600 controller and possibly a gate drive transformer. Switching frequency would be in the range of 80kHz to 120kHz. I found an online LLC calculator and it gave Ls = 25uH, Lp = 126uH, and Cs = 100nF. I also did some calculations by hand and found that the results were similar. I have no idea if it will be practical to reach these values in a real transformer.

One possible complication is that I intend to use a 20uF film cap for the output filter. This cap will have very low ESR on the order of a few milliohms. For this reason the ESR zero that the cap causes will be at a very high frequency. I am unsure if this could cause stability problems.

I also considered using a full bridge but I like the fact that the LLC only needs two transistors.

Does an LLC with ETD44 core sound reasonable for 1100W? With such a high output voltage, will the capacitance of the output rectifiers be a problem?
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Old 22nd June 2013, 12:22 AM   #2
DUG is offline DUG  Canada
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What material? Mfg?

ETD44 tells me the size only.
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Old 22nd June 2013, 01:49 AM   #3
cjk2 is offline cjk2  United States
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Ferroxcube ETD44 3C94 Material
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Old 22nd June 2013, 04:32 PM   #4
DUG is offline DUG  Canada
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From what I read on the data sheets you should keep your frequency down towards 25KHz.

At 100KHz the core losses are 8 times higher.

If you can fit the copper in then it should work.

I don't know about your copper losses though.

http://www.ferroxcube.com/prod/assets/etd44.pdf
http://www.ferroxcube.com/prod/assets/3c94.pdf
http://www.ferroxcube.com/prod/assets/etd_frnt.pdf

Good ap note

http://www.ferroxcube.com/prod/assets/sfappl.pdf

my $.02 worth.

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Last edited by DUG; 22nd June 2013 at 04:40 PM.
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Old 22nd June 2013, 05:28 PM   #5
DUG is offline DUG  Canada
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another note

http://www.ferroxcube.com/appl/info/HB2009.pdf
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Old 22nd June 2013, 07:57 PM   #6
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CJK2, the numbers for this design work out so perfectly i was wondering if this is a homework assignment.
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Old 22nd June 2013, 08:02 PM   #7
cjk2 is offline cjk2  United States
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Haha this is no homework assigment, I am wanting to build a variable frequency power supply and this is the isolation stage.

I am thinking I need an ETD49 now. 25kHz will not work as far as I know because the flux density in the core will be too high.
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Old 22nd June 2013, 08:53 PM   #8
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An ETD-44 at 50khz will give you just enough power for 1.1KW watts. 70khz will give you approximately 1.6KW.

At 70khz you will have 1600G with 26 turns

I played around with transformer margins a little and wire size and 2mm margins on each side will let you have a primary of 5 strands of 25awg, 320 Circ mills each. At 500 Cir Mills / A you would be good for 3.2 pri amps.

Sec turns = 62, and oops, it looks like i made a mistake after this. I mixed up my numbers and gave myself 2x as much room as there really is. Hmm best case i can see is 62 turns of 26awg at 254 Circ Mils for about 1/2 amp at 450vdc.

I would say the secondary may end up driving the transformer core choice.
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Old 22nd June 2013, 10:34 PM   #9
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Oh boy i made a mess out of this. I even did the primary wrong. Assuming half bridge it would see 200vdc out of the 400vdc PFC circuit. 3.2A x 200vdc = 640W.

We need about 2x more room on pri and secondary.
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Old 22nd June 2013, 11:28 PM   #10
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ETD-49 looks way to small also. Best i could do is 3.55A on the primary, we need a minimum of 5.5A
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