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Old 12th April 2010, 03:41 PM   #1
durwood is offline durwood  United States
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Default Bus pumping

I'm aware that half bridge designs can suffer from power supply bus pumping with poorly designed/operating class D amps, and this is associated with dead time of the FETs.

-If minor bus pumping occurs, what does it sound like? Does it sound like crackling/static distortion when playing lower frequencies?

-If the answer is yes to the above question, what particular components are responsible for this? Body diode? Output filter inductor? Driver?
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Old 13th April 2010, 10:19 AM   #2
Eva is offline Eva  Spain
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Pumping on power supply rails has no effect on output signal, at least in modulators with feedback, either pre-filter or post-filter.

Study the phenomena in terms of currents and voltages, it's self explaining. And you won't get it right in any other way.
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Old 14th April 2010, 07:21 AM   #3
ssanmor is offline ssanmor  Spain
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As you know, bus pumping is more important with higher output currents and lower frequencies. For this reason, it may become a seriuos problem with high-power subwoofer amplifiers, for instance. A simple practical solution is to use two half-bridge channels in BTL mode. In stereo systems, you can drive both channels out of phase and then undo the phase inversion by connecting one of the speakers out of phase again. This effectively cancels most bus pumping, as most of the low frequency information is common to both channels.
As Eva said, a moderate variation in rails shouldn't have almost any effect in the output quality due to feedback, but if it is large enough it can cause problems with the biasing of the internal supplies of the amplifier, or even cause a voltage rise large enough to damage some components.
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Old 16th April 2010, 10:10 AM   #4
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Pierre,
Is it next month already?
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Old 16th April 2010, 10:25 AM   #5
ssanmor is offline ssanmor  Spain
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Please don't hijack this technical thread, Workhorse. If you have anything personal against me or my company, please PM me.

I ask the moderator to act against these kind of attitudes as he has acted against other incorrect ones before (mea culpa).
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Old 16th April 2010, 11:04 AM   #6
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Old 16th April 2010, 11:13 AM   #7
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Default Help

You Sergio..

Taking help from non-commercial forum and using that help to produce commercial products and then selling the same product to diyers of same forum, not even a single word of apology comes from ssanmor neither he gave any credit to Phase_accurate




If you cant do something, don’t ask here, I had no knowledge in SMPS, now I have solid Knowledge



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Old 16th April 2010, 11:15 AM   #8
ssanmor is offline ssanmor  Spain
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Don't want to do this, we are ruining the thread and all I wanted to do is help the durwood, the guy who started it in search for help
I DID apologize and also talked to phase_accurate, so for me everything is solved. If some others want to take advantage of this incident, that's not my problem.

Sorry, won't help anybody else in this forum, even when sometimes I feel I can provide useful information to other DIYers.
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Old 16th April 2010, 11:27 AM   #9
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Quote:
Originally Posted by ssanmor View Post
Don't want to do this, we are ruining the thread and all I wanted to do is help the durwood, the guy who started it in search for help
I DID apologize and also talked to phase_accurate, so for me everything is solved. If some others want to take advantage of this incident, that's not my problem.

Sorry, won't help anybody else in this forum, even when sometimes I feel I can provide useful information to other DIYers.
You love to help people because you are nice guy, isnt it
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Old 16th April 2010, 12:16 PM   #10
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Quote:
Originally Posted by durwood View Post
-If minor bus pumping occurs, what does it sound like? Does it sound like crackling/static distortion when playing lower frequencies?
Minor Bus Pumping I am not sure of. A lot of Bus pumping (lol) causes the speaker to lose it. You won't hear music no more. You hear this big awful low freq noise. When I initially tried my amp in half-bridge and poorly designed it (well more poorly than my final product) , I got this effect.
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