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Class D Switching Power Amplifiers and Power D/A conversion

Odd question - Class D as low-voltage AC supply
Odd question - Class D as low-voltage AC supply
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Old 29th January 2018, 09:59 PM   #1
geezertron is offline geezertron  United States
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Default Odd question - Class D as low-voltage AC supply

Not sure this is the best place to take this odd idea to, but I'll take my chances. If I wanted to construct a 28V (RMS) 400 Hz power supply, could I just feed a class D amp the signal and treat the output the same way I would treat a regular AC power source?

One concern would be that the loads could be pretty reactive, for example a motor or transformer. I'm kind of dubious myself but these amps are so cheap. I just bought one for our living room for about $25 bucks. Stuck it in an old jewelry box. Works fine, the board looked like it was assembled by hand very late into the third shift but no problems yet.

Last edited by geezertron; 29th January 2018 at 10:00 PM. Reason: format
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Old 29th January 2018, 10:04 PM   #2
29285 is offline 29285  Europe
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I would expect there is a good chance to do it that way. Just check it out, these modern class-d-chips are quite robust and fail-safe.
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Old 29th January 2018, 10:07 PM   #3
DPH is offline DPH  United States
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Have you looked on Digikey/Allied/Mouser/Jameco/etc for their SMPS modules?

As an example, I picked up a Meanwell LRS 350-48 (350 watts, +48/0) for something like $32; it's actually built for the job, and very cost effective.
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Old 29th January 2018, 10:19 PM   #4
FauxFrench is offline FauxFrench  France
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If you look at an ordinary motor drive it is often a push-pull stage (single or double) using the motor winding as the inductance.
Buck power converters, class D amplifiers and bridged motor drives are based on the same idea.
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Old 30th January 2018, 12:29 PM   #5
DUG is offline DUG  Canada
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28Vrms is almost 40V peak.

You need an amplifier that is a BTL with a supply higher than the 40Vp.

TPA3255 would fit this requirement.

For a SE drive look at TDA8954. ( +/- 42.5V supplies )
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Old 1st February 2018, 01:17 AM   #6
whizgeek is offline whizgeek  Ireland
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In a BTL does the PSU need to be only 20V ??
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Old 2nd February 2018, 11:08 PM   #7
DUG is offline DUG  Canada
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28Vrms is almost 40V peak.

You need an amplifier that is a BTL with a supply higher than the 40Vp.
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Old 3rd February 2018, 02:11 AM   #8
theAnonymous1 is offline theAnonymous1  United States
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Something like a TAS5630 mono board with a 48V supply.
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