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Class D Switching Power Amplifiers and Power D/A conversion

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Old 13th March 2018, 07:05 PM   #21
DreadPirate is offline DreadPirate  United States
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I don't believe I had anything connected up to the amp, it was just powered with no connected load. The C34 chip was not damaged at all.
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Old 14th March 2018, 02:25 AM   #22
forestsgump is offline forestsgump
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[QUOTE=voltwide;5370798]To clarify this problem: The output LC-tank has a resonant frequency in the range of 50 kHz. If you connect a 50kHz-signal with the input, the output of the amp sees a very low impedance of the series resonant tank. In that case
1) The voltage at the resonant cap (680nF) may rise far above supply voltage thus destructing the cap.
2) Output current exceeds limits and over-current protection trips.

But...
If you do not connect 50kHz to the input, the resonant tank is not excited../QUOTE]

What mean, if i have the op-amp input shorted, its output to TPA wld be muted, thereby no way to excite resonant frequency. Then in this case no danger at all even without load?
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Old 14th March 2018, 03:18 AM   #23
voltwide is offline voltwide  Ireland
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Quote:
Originally Posted by forestsgump View Post

What mean, if i have the op-amp input shorted, its output to TPA wld be muted, thereby no way to excite resonant frequency. Then in this case no danger at all even without load?
Yes
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Old 15th March 2018, 04:00 PM   #24
forestsgump is offline forestsgump
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Quote:
Originally Posted by Khron View Post
I'm a bit surprised of 1N400x's being recommended. If anything, i'd rather expect some fast-recovery diodes in those positions (since you have the several-hundred-kHz switching waveform going on, before the output filter). Something like UF400x's or MUR1x0's or something.
Quick question: on these clamp/catch fast-recovery diodes

Any reference specs suitable?
~ Peak Reverse Voltage, Maximum Current, How fast-switching?

I found some high efficiency recifier HER501~508, not sure suitable to do the job?
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File Type: pdf her501-508.pdf (30.5 KB, 6 views)
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Old 15th March 2018, 04:29 PM   #25
Khron is offline Khron  Finland
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Reverse voltage, 50-100% greater than the supply voltage; current, 1-2A should suffice, i'd reckon; switching speed, anything rated for fast switching.

Those HER50x's might be a bit overkill, actually
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Old 15th March 2018, 06:07 PM   #26
voltwide is offline voltwide  Ireland
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I guess the 100V type should be fine.
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Old 15th March 2018, 06:12 PM   #27
DPH is offline DPH  United States
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Quote:
Originally Posted by DreadPirate View Post
I don't believe I had anything connected up to the amp, it was just powered with no connected load. The C34 chip was not damaged at all.
RF ingress is a real possibility depending on what sort of input filtration you have. Shorted inputs to ground *should* obviate this concern, though. (Unless things go really badly)
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Old 15th March 2018, 11:35 PM   #28
forestsgump is offline forestsgump
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Thanks these are cheap - even found some HER208 (2A1000V) are 1/3 cost of HER50x's
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