Buffer capacitor on class D design

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I bought an ICE Power 500ASP + 500A module and while reading the design manual, I noticed they use a buffer capcitor of 10000uF/150V for (star) ground and Im wondering, what’s the reason for this?

https://www.parts-express.com/pedocs/manuals/icepower-asp-series-manual.pdf page 44

They also mention this at page 12
“Adding an optional capacitor on the main DC-bus will significantly increase t150 as evidenced by the numbers given. This can be exploited in subwoofer applications, where it results in improved ability to handle transients”
But cant figure out what does it means
 
t150 is the time at 150% of continuous rated output before the rail drops too much and protection kicks in with soft clipping.

More rail capacitance allows the rail voltage to hold up for longer. The tables seem to show situations where 250ASP and 250A modules are running together, and one is stepped to 150% - the times in milliseconds indicate how quickly each amp lasts before protection kicks in.

With low frequency tones increasing the t150 from 20ms to 45ms makes a big difference.
 
t150 is the time at 150% of continuous rated output before the rail drops too much and protection kicks in with soft clipping.

More rail capacitance allows the rail voltage to hold up for longer. The tables seem to show situations where 250ASP and 250A modules are running together, and one is stepped to 150% - the times in milliseconds indicate how quickly each amp lasts before protection kicks in.

With low frequency tones increasing the t150 from 20ms to 45ms makes a big difference.

yea I saw those, but in real life terms, what does it means “150% of continuous rated output.”. You mean going over the 500W? (on the 500ASP)
 
yea I saw those, but in real life terms, what does it means “150% of continuous rated output.”. You mean going over the 500W? (on the 500ASP)
If you read the small print, 500W or whatever "RMS Power" they claim, is available only for a few seconds :eek:, it is not continuous by any means. :rolleyes:

By the classic definition those amps (and many other Class D type) should be derated A LOT

Won´t use the word "scam" but it´s rolling in my tongue.

From another (very realistic and practical) point of view, "the amplifier is that thingie between power supply and speaker" (Enzo tm), it´s the faucet that controls how much water comes out of a bucket but can´t supply more than what´s available inside it.
Adding a large capacitor increases the size of that bucket.

I guess the "150% increase" means they will hold the 500W rating longer, maybe for 150% of the original time.

Don´t have your datasheet available, but I cut/paste from the "170W"
ICEpower50ASX2
2x50W or 1x170W ICEpower Amplifier
which is used by many respected Bass amplifier factories (Fender, Gallien Krueger, etc.) in their 150 to 200W rated amplifiers (Fender Rumble 150, GK200, etc,)

On page 3 they proudly state
Key Specifications
• 170W @ 1% THD+N, 20Hz – 20kHz, 4W, BTL
Looks good, isn´t it?

BUT on page 9 (who reads that far? :cool: ) they clear:
tPmax Time of maximum rated output power 170W out. No preheating. - 120 - s
That´s right: it can supply 170W RMS for one-hundred-twenty-seconds = TWO MINUTES

And that if starting from cold.

And then, what continuous power can they REALLY deliver, no thermal muting?:

PT Continuous output power4) without
thermal shutdown. (BTL, 4)
Thermal stab. @ Ta = 25 OC. - 50 - W

or if you don´t push it (using higher than rated load impedance to lose rated power and make it easier for the module):

PT Continuous output power4) without
thermal shutdown. (BTL, 8)
Thermal stab. @ Ta = 25 OC. - 100 - W

Again: didn´t read your specific datasheet but would not be surprised at finding equivalent statements.

And makes me think that mentioned "150% improvement" refers to increase respective to the *attenuated* ouput, not going beyond "official" 500W by any means.



On page
 
For subwoofer duty it matters a lot. There are plenty of dead 200asc modules precisely for this reason. Often chosen for mid budget consumer sub applications the module is placed inside a box, so has poor thermal conductivity to the outside world and is asked to provide significantly higher levels of continuous power Vs what usually happens when people listen to music with normal speakers.

Adding to this the fact that people like to turn up the bass, with action heavy movies, or electronic music, the modules simply overheat.

With regular music listening, no problem, with other duties? Dead amp modules.
 
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