Switch Mode Power Supply Vout: 650Volts @ 10A

I need to convert a DC voltage of 120Volts (can be less but not more) to feed the bus of a 3 phase motor controller. I'm by-passing the input rectifier, as I am source power from a battery stack.
I have on hand some step up transformers 1:17 that I was planning on using [edit: for a flyback design]. I am curious if I should take the time to achieve zero volt switching on my boost power supply.
I half expect that I will have multiple 1KW SMPS circuits in series to hit my 650 Volt target. Can anyone recommend a particular app-note or topology for this type of supply?
:?::?:

You can achieve your goal by using Phase shift full bridge or Resonant LLC topology rather than flyback topology . Most of the app notes are for buck converters to convert 400V to some 3.3 or 12V , it is very rare to find appnotes for your particular type of application. you need to design a transformer which can handle this kind of power first.

You can use UCC28950 from TI , ISL6753 from Intersil for PSFB and a number of controller chips are available from TI and Fairchild for Resonant LLC topology which can be scaled upto 4KW /unit easily with a good selection of switching components and Diodes.

A three level LLC resonant converter is proposed by combining three level technique and LLC resonant technique.MLC/LLC cache miss, branch misprediction and TLB miss are crucial to the power management discussed here within.
:wink:

sofiar said:

A three level LLC resonant converter is proposed by combining three level technique and LLC resonant technique.MLC/LLC cache miss, branch misprediction and TLB miss are crucial to the power management discussed here within.
:wink:

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Huh? 8-O




Joel

Implementing a LLC converter at such a high power level seems like a huge challenge. Probably not worth it unless you know what you're doing and you really need the extra bit of efficiency. With an interleaved boost converter you could probably get about 90% without much trouble.

mtwieg said:

Implementing a LLC converter at such a high power level seems like a huge challenge. Probably not worth it unless you know what you're doing and you really need the extra bit of efficiency. With an interleaved boost converter you could probably get about 90% without much trouble.

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After reading about 15 papers on LLC converters from IEEE, I was thinking the same thing. It is still on the table, but I am hungry for a simpler solution.

I was looking at a full wave converter with a center tapped secondary transformer or a non-center tapped with a full wave rectifier at its output. I haven't come across the term "interleaved" yet, so I searched and found an app-note that might suit me here: Powered by Google Docs
I haven't yet gone through it all so bear with me, but I'm curious to know what advantages are there to using a 2 inductor interleaved approach? This app-note makes use of an "auxiliary transformer" and I like this as my voltage differential is at least 6:1.

Something else that I am wondering. I'm looking for a transformer that will suit this application and have been able to find lots of 60Hz AC transformers that can handle 10KW and are quite large. If size isn't a problem for me, is it feasible to use these bulky low frequency transformers? Re-winding an existing transformer or winding one from scratch is on the table and I am gathering information to make this decision. Any comments on this here would be helpful if you have a thought.

Thanks for taking an interest.

Joel

By interleaved, I mean that there are essentially two boost converters working in parallel, but are controlled by the same controller. The two converters are operated 180 degrees out of phase, which reduces ripple currents and allows you to use smaller power components (though you need two of each). For example I've built a 20KW interleaved PFC using the UCC28070, which is meant for interleaved converters (though not anywhere near that power level). You may need PFC as well at your power level. [edit: wait no you don't you have a DC source, nevermind]

Interleaving is nice, but not really a requirement unless you want to make things really small and cheap. The interleaving in that paper you linked is a more exotic type of converter... I would stay away from academic papers on bizarre topologies; most of them are completely impractical.

Do you need isolation for your application? 60Hz transformers won't work in high frequency SMPS. Too much loss due to eddy currents.

Brilliant!
I do not require isolation but was concerned, due to lack of experience, about the large boost in voltage required using only inductors.

With 120V in and 650V out you're looking at ~80% duty cycle, which is high but not extremely so. If you use peak current mode control then you'll want to use plenty of slope compensation.

I'm working on a solution using power Stage Designer from TI and it doesn't have the Interleaving option. Would it suffice to develop a single boost regulator and then interleave them? I would then assume some power handling requirements will be in the neighborhood of 60% of what is required from a single boost converter.

With interleaving, the multiple boost circuits aren't completely independent. If they use current mode control, then they will have independent current control loops, but the voltage control loop will be shared between them. That ensures inherent power sharing. That's why there are specialized ICs for current control loop (they also handling the splitting of the clock for each phase). It's generally possible to make two completely independent converters with their own control ICs work in an interleaved fashion, but you have to ensure power sharing and phase shift yourself.

I wouldn't get too hung up on the whole interleaving thing, it's just an idea I tossed out there. To be frank, if you don't understand what the benefits and drawbacks are, then you can't really justify using it for yourself. Also there are very few suitable controller ICs, and most of them will be pretty sophistocated and specialized. With some quick searching the closest thing I was able to find was the UCC28220, which might work for your application. I don't have time to browse the entire datasheet myself though.

mtwieg said:

To be frank, if you don't understand what the benefits and drawbacks are, then you can't really justify using it for yourself.

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Good thing none of the above applies to me :-| . I am having fun and appreciate the discussion, but do not feel obliged to participate. I certainly don't expect you to do any research for me.


Thanks for the UUC28220 tip though, I'll check it out.