Electronics > Power/Renewable Energy/EV's

Totem Pole PFC is over-hyped?

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SlimEddie:

--- Quote from: temperance on April 27, 2024, 02:25:55 am ---What is your experience with the TTPL PFC in terms of efficiency and mains filters?

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So far this is my first time working with TTPL PFC. Now where do I begin...

First and foremost, TI's reference design code can be a mess, and the documentation is often skipping some steps.
From the get go I had issues with the code running from main processor, it would compile just fine and run on CLA (the co-processor on C2000 MCU family), but would fail on the main C28x core.
After some digging I found that they forgot to copy ISR functions into ram and the CPU just couldn't find the code where it expected it to be. Apparently TI discontinued the reference design that I was using and I think that the state of firmware was one of the reasons for it. Anyhow, after finishing my fight with the code, I successfully managed to run in in PFC mode whilst supplying it from DC supply instead of AC, I managed to verify that all measurements make sense and all the legs switch correctly.
Next issues came when I had to run TI's SFRA to get an open loop frequency response, since at that point I was still running from CLA instead of the main core that ended up being the bottleneck, which got resolved as soon as I was able to run somewhat stable fw on main core. Although the frequency response matched TI's reference in terms of shape, the gain was a tad lower than it should be. I shrugged it off and moved on to test with AC, where I am currently stuck, after fixing another bug in fw that had wrong defines used, I managed to get it switching with AC, but I am facing an issue with current loop instability, the shape of the curve has a dip which is not present in TI's reference design and overall gain is lower than it should be, so currently I am trying to figure out the root cause of this issue, which is difficult considering there is 3x switching frequency noise everywhere  you try to measure. Over all I expect to have a lot of issues with conducted and radiated emssions when I get to solving those issues in the future.

temperance:
Thanks for your reply. So in short the TI solution doesn't work properly. I haven't had time to play around with the Infineon XMC solution. Maybe around summer or so.

Regarding the noise.

I have no idea about your level of experience with developing switching power supplies so I might suggest something you all ready know. If probing around with normal probes when almost no output power is delivered indicates to me that there is something wrong with how the power components are switching. If there is a problem, it is visible when probing the gate wave forms and inspecting the gate source miller plateau voltage at turn on. Any kind of wrinkles or sings of oscillations must be "cured" before you can continue because it will cause common noise all over the place.

SlimEddie:

--- Quote from: temperance on May 03, 2024, 04:31:24 am ---Thanks for your reply. So in short the TI solution doesn't work properly. I haven't had time to play around with the Infineon XMC solution. Maybe around summer or so.

Regarding the noise.

I have no idea about your level of experience with developing switching power supplies so I might suggest something you all ready know. If probing around with normal probes when almost no output power is delivered indicates to me that there is something wrong with how the power components are switching. If there is a problem, it is visible when probing the gate wave forms and inspecting the gate source miller plateau voltage at turn on. Any kind of wrinkles or sings of oscillations must be "cured" before you can continue because it will cause common noise all over the place.


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Well this is one of a few solutions advertised as bidirectional, there are not many of those around and it fits our needs, so I am gonna have to fight with it till it works.

I have a bit experience with SMPS design, but most of those were <150W. The jump to 3.3kW is a tad scary and expensive in regards to equipment used.

On the bright side,I had some success fixing the shape of the current loop frequency response from this:

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To this:

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While it finally matches the shape of frequency response I was hoping for it is still 10dB lower in terms of magnitude compared to what should have been. Gonna need some work tweaking the values.

Faringdon:
Sounds like you are fighting some good winning battles in getting it working.
You say you need bidi, and yes, for this reason the Totem pole PFC sounds good.

Otherwise, at 3.3kW , i wonder how much more efficient that would be when compared to a Dual interleaved PFC with UCC28070?
https://www.ti.com/product/UCC28070

...thats two PFC's each with  just 4.125A of output current.

Make the rectifier bridge synchronous and its even more efficient.
I doubt the totem pole is going to be much , if at all, more efficient than that.

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