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Class D Switching Power Amplifiers and Power D/A conversion

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Old 8th January 2008, 02:18 PM   #61
djQUAN is offline djQUAN  Philippines
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my brother went on vacation and took the camera with him so no pictures for now.

update:

I have completed the powersupply

the transformer I used has 6T+6T pri and 28T+28T sec. one of them has an aux 4T for 5V supply and the other has aux 9T for +/-15V supply.

output voltage is +/-68V idle with 15V input just before input overvoltage prot kicks in. (Tripath chipset max input is 70V)

freq is 40kHz idle current is 200mA (entire supply draw including gate drive and TL494 circuit) with output rectifiers and snubbers not yet installed.

edit: I installed the snubbers and realized the ones at the secondary is too small. increased the resistance then all is well.

also, the gate drive is 16V peak and maintains regulation down to 10V.
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Old 8th January 2008, 02:42 PM   #62
luka is offline luka  Slovenia
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hi

how much wire did you use this time?
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Old 8th January 2008, 03:12 PM   #63
djQUAN is offline djQUAN  Philippines
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A LOT!!!!


all used #22 magnet wire

each primary has 15 wires.
each secondary has 12 wires.

you can barely see the core in all that copper.
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Old 8th January 2008, 03:18 PM   #64
luka is offline luka  Slovenia
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Hi

HAHA,will you be able to lift them? and watch that you don't break the board
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Old 8th January 2008, 03:33 PM   #65
djQUAN is offline djQUAN  Philippines
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hopefully the board doesn't break.

I will use silicone around the trafo's so that vibration won't knock them off.

knowing that the trafo's will be heavy, I added mounting holes on the PCB right under the trafo's.


a few more measurements:

over voltage cutoff is lowered to 14.5V. above that, the supply shuts off.

at 14.5V input just before the supply shuts down, output voltage is +/-68V (+/-70V = maximum voltage of the tripath chipset)

with everything installed, current draw is 390mA idle

waveforms are near perfect square waves with sloping sides. absolutely no spikes or ringing of any sort.
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Old 8th January 2008, 03:44 PM   #66
luka is offline luka  Slovenia
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Hi

Great to hear that. So power test soon, do I hear that? Also will you heasure input and output voltage at few power levels? This is unregulated supply right?
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Old 8th January 2008, 03:49 PM   #67
djQUAN is offline djQUAN  Philippines
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yup it is unregulated to keep things simple.

power test? I think that would not be anytime soon. I still have to finish wiring the fan, VPP and VNN lines to amp8 and mounting the terminal blocks.

then we can do power testing.
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Old 8th January 2008, 07:11 PM   #68
luka is offline luka  Slovenia
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Hi

I was thinking that you would test supply only, just to see how things are standing right now. Anyway good luck even if you won't
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Old 10th January 2008, 03:39 PM   #69
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the camera is back so time for pictures.

completed SMPS:
Click the image to open in full size.

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terminal blocks:
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mounting of fets and rectifiers:
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toroid mounting locations:
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approximate look of completed amp:
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Old 10th January 2008, 03:44 PM   #70
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BTW,

has anyone tested amp8 above +/-65volts? because I'm afraid of blowing up the driver chip. the chipset is rated at +/-70volts and the SMPS goes up to about +/-68.

how do the other tripath chips handle a bit of supply overvoltage?
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