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Old 28th October 2012, 02:06 AM   #31
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What voltage/current will this thing now work at/provide?
It currently runs at 50 volts and 3 amps.
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Old 29th October 2012, 01:21 AM   #32
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Now that you've solved the apparent problems, would you say that the transformer is running cooler then it was before, or does it just run hot? And have you measured the efficiency of the thing?
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Old 29th October 2012, 02:16 AM   #33
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Now that you've solved the apparent problems, would you say that the transformer is running cooler then it was before, or does it just run hot? And have you measured the efficiency of the thing?
It is still running hot. I have also found the transformer to be very noisy on full power.
Its not quite there yet, I still have a bit of work to do.
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Old 29th October 2012, 05:19 PM   #34
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I have returned to the ETD54 core and added a 1mm gap and the transformer whistles just slightly, should be ok in a enclosure.
I am now getting 40 volts at 3.2 amps which is passable.
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Old 13th November 2012, 11:45 PM   #35
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Latest update.

I tidied up the design and ordered some new pcb's.
They arrived and I built one up.
I had problems previously with the transformer whistling so I wrapped the turns tighter this time then applied lacquer to hold the turns together.
Fired up the new pcb and it still whistles like mad !
I had another look at my software and it looks at the voltage feedback and if a pulse is required it gives a full power pulse. The gap between these was a bout 5KHz hence the whistling.
I tried adding a very short pulse to the transformer if a large pulse wasn't needed and the transformer suddenly went very quiet.
I am getting 50 volts and 3 amps which was my target so happy now.

I should have added I went back to an ETD54 transformer. I couldn't source any gapped cores so I added 1mm spacers to the core.
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Old 15th November 2012, 12:17 AM   #36
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I did a full test of my SMPS with different loads tonight and the whistling is there again.

So I have altered the software to measure how long between feedback pulses and output a pulse proportional to the current required.
While this hasn't cured the whistling it has spread the whistling spectrum a bit so it isn't so loud.

The L6565 outputs pulses depending on the current taken by the transformer primary and so doesn't have this problem.
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Old 18th November 2012, 12:04 AM   #37
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I found I got an improvement in current output by giving the transformer a larger gap.
This reduces the inductance a little and allows a longer drive pulse to the primary of the transformer.
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