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Old 18th September 2006, 07:01 PM   #51
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I might appear irritable to some.. but some of us seasoned power supply designers MUST workout solid state device heating especially when switching IGBT and mosfets are used in the high power range. So many designs are now in the open for all to see. It's not just simply lashing up another device and seeing if it works and might explode. The idea that the switcher may be running cool is one thing....the other is the boost diode my be overheating.
ST has a homepage on boost converters with a download with magnetics sizes.

djQUAN> got a PFC module made by astec for cheap and it puts out 380VDC and 950W from 100-240VAC in. should be useful but haven't touched it yet. the voltages are scary.

I wonder what the efficency is at low line 100V as claimed 950W output ?
Anyone worked it out ?

richj
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Old 20th September 2006, 03:25 AM   #52
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I had another look and it said 950W at 240V and 550W max at 100V input. my bad.
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Old 20th September 2006, 01:09 PM   #53
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Quote:
Originally posted by richwalters
I might appear irritable to some.. but some of us seasoned power supply designers MUST workout solid state device heating especially when switching IGBT and mosfets are used in the high power range. So many designs are now in the open for all to see. It's not just simply lashing up another device and seeing if it works and might explode. The idea that the switcher may be running cool is one thing....the other is the boost diode my be overheating.
ST has a homepage on boost converters with a download with magnetics sizes.

djQUAN> got a PFC module made by astec for cheap and it puts out 380VDC and 950W from 100-240VAC in. should be useful but haven't touched it yet. the voltages are scary.

I wonder what the efficency is at low line 100V as claimed 950W output ?
Anyone worked it out ?

richj
I can easily measure if my PFC is running OK. If all wave shapes are OK. If there are no excessive load conditions. Thermal behaviour as well. But with my normal home equipment I am far away of any chance to figure out the efficacy.
For the input side measurement one can completely forget normal DMM. Scope is not really nice... even if there is a way to come around the reading error of the phase shift. Pick the instantanious power (voltage x current) and integrate it over 10ms....
Still then I have to consider an error of +/-3% in the voltage and -/+4% in the current. The DC output I can measure more accurate. Say 1% in voltage and 1.5% in current.
...if my measurements tells me efficacy=94% this means 94% +/- 9..10% - ah well, we can be sure that we do not exceed 100%...
In the end I am just able to say my efficacy is between 85%...100%,

And sometimes people are trying to convince me that their PFC has 99.97427 % efficacy

djQuan:
Sorry, nothing availabe up to now. But I think a halfbridge will easily do the job. Take care for the isolation in the transformer !!!! And also in voltage measurement with monster isolation optocoupler or well isolated auxiliary winding....
At 400V EN60065 table 11 is demanding for most normal material surface properties (100<CTI<400) creepages between 8mm up to 12.6m. 8mm or 12.6 mm are depending on the applicable degree of dirt. In most home audio applications 8mm should be sufficient.
According table 8 the clearances have to be 4mm. Depending on interpretation of table 9 you would need to add another 0.2mm.
According chapter 14.3.4.1 the min thickness of isolating parts in the bobbin must be at least 0.4mm.
If you discuss isolation of mechanically stressed wires, then even higher thicknesses might be required.... also you have to make sure by mechanics that the creepages/clearances are still guaranted if a copper track gets off the PCB, or a wire soldering might open....
Last but not least it is known that the isolating robustness of most isolators is affected by HF. EN60065 is stating up to 30kHz, but allows application above 30kHz until proper values for higher frequencies will be defined.... But I would expect even more stringend demands within a few years...
And you can be sure that there are many more pifalls in the 158 pages of that safety standard!! Quite inconvinient stuff! Everybody who deals with off line isolation circuits should spend some time with this, or other relevant safety standards.
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Old 20th September 2006, 01:26 PM   #54
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I have thought about a half bridge setup but thought that it would require more primary windings (not good for cores with not enough space) and that I would need higher voltage fets.

another problem was the supply for the oscillator. I could use a resistor to drop the main 380V rail to the low voltage required by a TL494 but that would give a lot of heat! another option was to power it with an auxiliary winding from the main trafo but how would it run at startup? another was by having an auxiliary linear supply but it also increases size a bit. my best option so far is to power the oscillator with a resistor at startup and disconnect this and power it via an aux winding when the SMPS is running all done automatically by some HV low current transistors....

comments?
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Old 20th September 2006, 05:02 PM   #55
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Default HV Start-up Circuit

DJ,

Look at this thread.

Offline full-bridge SMPS....need help

We discussed, at length, various start-up circuits.look at post #122 and beyond.

Steve
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Old 25th September 2006, 06:09 AM   #56
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Just as a note, be careful of those HAMers, the FCC will come out and hunt you down with a signal tracker and FINE YOU. So if this PSU actually does emit RF, don't use it very long at a time and be careful...

I may not know what everybody is talking about but this is something I do know...

Just be friendly and you'll be OK...
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Old 25th September 2006, 11:33 AM   #57
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Quote:
Originally posted by keantoken
Just as a note, be careful of those HAMers, the FCC will come out and hunt you down with a signal tracker and FINE YOU. So if this PSU actually does emit RF, don't use it very long at a time and be careful...

I may not know what everybody is talking about but this is something I do know...

Just be friendly and you'll be OK...
You are perfectly right. Especially the gapped choke is some sort of antenna. I am also interested in low radiation and will encapsulate the entire beast. May be I should check it then in our EMI lab... for conductive EMI (probably fine) and radiated EMI... At least I cannot see any influence in my TV, radio or WLAN when running my PFC even without shield.
When you live in China, then you start getting sensible on such things. It is an EMI-hell here. If you want to get your WLAN running you have to spend some efforts in finding a less poluted power plug for the router/acces point ... and search some 'magic points' to position the antennas....
And even then you don't bridge more than one wall + 7m ! Do I have mu-metal walls here?
...in Germany it bridges roughly three times more...
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Old 25th September 2006, 09:28 PM   #58
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Thanks! You make me feel proud...

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Old 9th September 2007, 05:07 PM   #59
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Hi friends,

I'm trying to construct a 1.2kw PFC prototype. I selected IGBT with TO-247 package and I planned to mount IGBT and boost diode on circuit board. But now I have some doubts about mounting them on board because current above 10 amps will pass through them and I think soldering between IGBT and board may be damaged due to high current. What do you think, do you have some practical experince about the subject?
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Old 9th September 2007, 09:37 PM   #60
mzzj is offline mzzj  Finland
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Quote:
Originally posted by corcbest
Hi friends,

I'm trying to construct a 1.2kw PFC prototype. I selected IGBT with TO-247 package and I planned to mount IGBT and boost diode on circuit board. But now I have some doubts about mounting them on board because current above 10 amps will pass through them and I think soldering between IGBT and board may be damaged due to high current. What do you think, do you have some practical experince about the subject?
Not any problem, just use enough wide copper traces on pcb and keep your layout tight.
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