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Old 12th March 2009, 08:15 AM   #1
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Default +/-80V 7Amp SMPS

Helo.

I am working at schematic below. this supply will be used in audio amplifier, and must pass such test.

Output voltage +/- 80 V DC

Load used, Halogen lamp 1000W 220V.

Connected the load (one lamp) for 5 hours with no problem, stable,
Output voltage +/- 80 V DC, 3.5AMP

Connected two lamps 1000W Mosfets Blown in 7 minutes.
Output voltage +/- 76 V DC, 6.65AMP

The transformer temperature is 85C when connecting the two lamps as the load.

I need help in:


1- Is it normal for the transformer to heat that much?
2- Is there any way to minimize the heat of the transformer?
3- Why the mosfets blow up?
4- Primary Turns 20 1mm , Secondary 12, 12 Turns 1.2mm

Appreciate the help
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Old 12th March 2009, 05:23 PM   #2
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I don't know the exact reason, butyou may like to correct some thing:
- mosfets may need individual D-S RC snubbers
- bootstrap capacitance is very high
otherwise it looks OK for me, nice design (unless I overlooked something)
The things you describe may have something to do with winding technique and transformer parasitics.
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Old 12th March 2009, 08:29 PM   #3
luka is offline luka  Slovenia
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I would use 2x 1mm pro primary and secondary

Can you say that does heat, core itself or wires and core with it?
half power, does core heat up?

If you really have edt59, use 2x 1mm primary, 3x 1mm secondary, more wire the better in terms of heat, I think core itself does not heat up..

Also that 1uF cap in series, you could add one more

And yes, do use 100uf instead 22uf for IR

You could use snubber right on trafo, not behind rectifiers

What is your freq.?
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Old 12th March 2009, 08:37 PM   #4
star882 is offline star882  United States
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Most likely an overheating issue.
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Old 13th March 2009, 07:09 PM   #5
mflorin is offline mflorin  Romania
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although it may have nothing to do with your problem, I really don't like the zener-opto combination in the feedback path. A more appropriate solution will be a TL431+opto configured as a type 2 error amplifier....
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Old 14th March 2009, 08:29 AM   #6
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Default Transformer

Heloo.


Thanks for you all,




I think that I have some problems with the transformer winding, I am not an expert in transformers, but will Re wind it as LUKA recommends.

Also, there is a snubber circuit for mosfets, and protection diodes at the gates for transients and surge protection.


I have noticed that the Upper mosfet in the schematic, the one connected to the +320V line, Heats more than the other one.

I think that the transformer design in any SMPS is 70% the success and efficiency of it.


I have a design from professional Amplifiers manufacturer using two IGBTs, and delivers 3000W RMS, with a few components, really simple.
but the transformer in there is not simple. (other wise any one can do it)

Any advice about transformer winding?
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Old 14th March 2009, 11:38 AM   #7
luka is offline luka  Slovenia
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Hey

What I think you should try is, 1/2PRI, all sec,1/2PRI, then some aux or some low current if you have them
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Old 19th March 2009, 12:19 AM   #8
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Can you send me your working layout i did but not worked.
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Old 19th March 2009, 10:14 AM   #9
Fob is offline Fob  Bulgaria
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I think that ETD59 is small for this design. Change to E65 or greater.

N=Bsat*le/u*I
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Old 19th March 2009, 08:25 PM   #10
luka is offline luka  Slovenia
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Quote:
Originally posted by Fob
I think that ETD59 is small for this design. Change to E65 or greater.

N=Bsat*le/u*I
EDT44 can put 1kw easy, hell 59 is for several kw
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