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Old 7th April 2005, 06:39 AM   #1
kuda is offline kuda  United States
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Arrow Class D Power Supply

Have you guys seen any references to power supplies in Class D amplifiers. From other people's posts I've gotten the idea that this is usually a switching supply which does not produce interference in the audio band. I've never built one of these so I'd like to know if anyone knows any references to this topic.

I'm working on a class D design right now based on the HIP4080 driver IC from intersil and every time I turn on the benchtop power supply (HP E3631A) the quality of the audio and triangle waveforms gets more and more corrupt as the h-bridge voltage gets higher. Any ideas on what is done to correct this other than careful layout? Thanks.
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Old 7th April 2005, 03:55 PM   #2
hdoggz is offline hdoggz  United States
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I've also experienced that with the 1 classD amp that I've built. I used a HIP4081 driver. As the voltage went up, the noise increased and there was a certain limit (~40V) where there would be so much noise you wouldn't even heard the audio.
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Old 7th April 2005, 04:00 PM   #3
ted12 is offline ted12  Singapore
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idea of decoupling capacitor
but I don't have any information in hand
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Old 7th April 2005, 08:08 PM   #4
kuda is offline kuda  United States
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I have two 100uF caps on the bridge supply and bypass caps on all ICs so I think I've bypassed all I could. I'm not sure what could be happening now. The ripple on the bridge supply still gets worse and worse with increasing voltage so I think that is still the main issue.
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Old 8th April 2005, 07:02 AM   #5
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I have experinced some pretty severe noise problems with a design based on the HIP4080 driver IC. The use of separate supplies for the control- and output stage and propper decoupling with NPO ceramic capacitors close to every IC did not solve the problems. I think that a solid ground plane in combination with carfull layout of both the modulator/control section as well as the output stage will help to reduce the noise coupling. However I never tried to make a new layout to verify this....instead I build a new amp with the ZXCD1000 controller IC. The integrated triangle generator and pwm comparator of this IC solves a lot of those noise problems encountered with the more "discrete" approach.
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Old 4th May 2006, 02:04 PM   #6
ilge is offline ilge  Austria
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Wink class D Supply

Hi,

ive the same problems. I found a nice link from TI.

"Design considerations for Class-D Audio Power Amplifier"

Application report - www.ti.com

Hope that helps

ilge
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Old 4th May 2006, 09:15 PM   #7
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Hi,

Your lab supply may not be able to cope well with the recirculating currents (pumping). Just a thought.

Maybe if you posted your design schematic ..
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Old 12th May 2006, 07:58 AM   #8
Baldin is offline Baldin  Denmark
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Working on a design using HIP4080A, and experiencing noise problems as well!
Se my thread Noise problems in non discrete class-d amp

Not sure whether tis is actually the same problem at all, but maybe there is some relations anyway!

I'm using a small PSU of 16 V to feed the power stage (just for starters, and haven't tried to raise the voltage yet).

I have reduced the noise considerably by placing a 4p7 ceramic between pin 5 and 6 of the HIP (to slow down the comparator).

I have tried more decouplings on all stages (driver section, and analog section have each there own LM7812, but analog section is also using a virtual ground), vith no real result (well a large 10.000 uF in the main supply helped a bit).

Are you using snubbers on the output mosfets?
I'm not but, I'm thinking whether this might do any good?

Se diagram on my homepage for details



Sensible Audio, DIY Self Oscillating Class-D Amplifier (SODA)
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