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Old 1st July 2009, 07:58 PM   #71
Bootstrapper is offline Bootstrapper  Finland
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Hello folks,

I have been designing a 1.2kW CCM boost PFC as well, based on TI UCC28019. Texas provides a handy spreadsheet to help with the design, I used it to define the compensation/feedback stuff, all the semiconductors and magnetics I designed myself.

Since this project is about to be completed soon, someone might be interested in the schematics/PCB artwork. There is always something to learn in other diyers projects - and plenty of mistakes to correct. This design might contain some flaws and some component values in the files have been changed. Still, here's one view to this subject:

Top assembly
Bottom assembly
Top copper
Bottom copper
Drill drawing

The drill drawing shows the holes that are cut on the board between mosfet and startup diode legs. I will add more details as well as the spreadsheet file tomorrow.
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Old 1st July 2009, 08:53 PM   #72
richwalters is offline richwalters
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What is your approach in dealing with hard switching charge injection spikes ? this is important in reducing EMI and the mosfet # heatsink assembly construction is important in reducing this: Why no CM EMI filter on o/ps.?

Be careful with the 15V controller supply common grounding: the EMI can travel back and re-radiate.

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Old 2nd July 2009, 01:10 AM   #73
Eva is offline Eva  Spain
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Nice 8-pin control IC, how did you find about it?

This PFC is hard switched but it uses an hyperfast diode, this improves reverse recovery losses somewhat...

Have you done any efficiency measurements? Could you post pictures of gate waveforms at high current? In the next few months I will have to face the development of a 350V 20-30A hard switched buck converter, but all my previous high voltage designs are soft switched...
I use to feel like the small child in The Emperor's New Clothes tale
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Old 2nd July 2009, 05:10 AM   #74
Bootstrapper is offline Bootstrapper  Finland
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Hi, to be honest: I haven't put a lot of effort in EMI issues. I do know the basics about reducing EMI but since I have no access to proper measuring equipment, I intend not to concentrate on them. If this design would be done in the right way (a commercial product) these should be taken seriously. The heatsinks will be connected to the circuit common.

One remark: This is purely an experimental project, and therefore the controller will be supplied from an external power supply. If I ever make a second version, that will be standalone one, with auxiliary winding on inductor to generate the supply voltage.

Eva: I found this one from TI website and ordered some samples. These controllers seem to be available from RS Electronics webshop and naturally from Farnell etc.

What comes to reverse recovery losses and the total efficiency, without the reverse recovery the efficiency (calculated) should be around 97-98 %. I'm still finding out a proper way to approximate the reverse recovery losses. The ultimate goal is to use a SiC diode instead of RURG3060 that is on the schematic. Basically I merely do some test runs with this setup until I can afford buying those SiCs (roughly 15 each - you don't want to burn them just for fun!).

Since I am not aware of the reverse recovery losses, the FET heatsink is quite huge. It will be big anyway, I want the FETs to run as cool as possible with natural convection.

I haven't build this yet, some of the parts are still on their way. Once I get this up and running, scope pictures will be shared!

p.s. This design was intended to feed a 1.1kW full-bridge converter - the main transformer design simplifies a lot when the input voltage range gets narrower. More on that later =)
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Old 19th December 2009, 10:32 AM   #75
Disney_SK is offline Disney_SK  Slovakia
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Location: Slovakia (middle of Europe :-))
Originally Posted by richwalters View Post
That 92% efficiency figure seems a bit low for 230 AC line. Have you carefully measured every bit of energy ? At high line volts using the SGS L4981A and hard switching, I'm getting repeatedly 95-97% efficency rate using an IGBT at 100KHz. Although my design isn't for 88-120VAC, the low line 88V AC is a sure efficency test for any SMPS boost converter..(The IGBT is lossy at low line)
You may find the ZVT reactor will recover the 2% efficiency at low line volts. Again, have you done precise measurements ?Otherwise at high Vin, it's hardly worth implementing it and it certainly shouldn't be sucking valuable efficency..What operating freq are you using ?

We used 250kHz, that's because we used that ZVT circuit which should minimize switching losses so we are able to increase frequency and reduce inductor size.
No, there are no measurement errors. But it was hitting 94,3% at about 300W output, at 1kW it was 94,0 (see figures). But it must be said that we did measure the input power BEFORE the mains rectifier, so the rectifier losses are counted in the overall efficnency. The rectifier power loss at full power was, by simulation, about 20W at 350Vac. If we would measure the input power AFTER the rectifier, the efficiency would be higher by about 2% which is in good agreement with the measurement made by Texas Instruments in UC3855 app. note (slua146a) where they measured the DC input power and got about 96% efficiency with similar measurement conditions (see figure - "Conventional").
So how are you measuring the input power? Are the rectifier losses accompanied in your efficiency calculations?
Attached Images
File Type: png without resonant switching.png (11.8 KB, 353 views)
File Type: png quasiresonant switching with resistive damping.png (14.9 KB, 349 views)
File Type: png TI slua146a.png (15.2 KB, 353 views)

Last edited by Disney_SK; 19th December 2009 at 10:37 AM. Reason: small typo
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Old 23rd May 2011, 07:55 AM   #76
AutoClassA is offline AutoClassA  Ireland
Join Date: Oct 2010
Another 1KW PFC.

comments welcomed

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