Clipping Class D ?

Status
Not open for further replies.
Jump to Latest
#3
This will mostly depend on the feedback topology used. Some additional soft-clipping measures can be taken as well.

If no soft-clipping tricks are used the following applies:
The least nasty (i.e. cleanest) clipping is from non-NFB topologies closely followed by first order loops with a high dominant pole freqency.
Higher order loops have the habit to "stick to the rails" when driven into clipping.

Regards

Charles
 
#4
Greet's

I was running my amp into clipping for a prolonged time over the new year ( celebrations and all that ). The amp is a home built self osc classD of my own design. The first thing that goes is the bass, this is followed by audiable clipping across the rest of the spectrum that sounds quite soft in comparison to A/B clipping. I would say the amp sounds like it backs down during clipping. I would not describe it as a harsh or damaging clip sound. I was rather drunk but it can't have sounded that harsh as i let it carry on like that for a large part of the early morning celebrations, i wouldn't delibratly harm my baby LOL

I can't speak for the other amps on here but i think the clipping is certaintly no worse than A/B. I gather you are worried about the amp self destructing at clip or somthing. I know i was, but after a few partys my confidence has grown and i now know it is rarther hard to damage these amps. The only time mine is destroyed nowadays is when i'm hot pluging and removing components from the breadboard.

Regards
Mad.P

P.S The amp was running 80RMS into 8R when clipping. Lasted all night!
 
#5
Nitrate,

i now know it is rarther hard to damage these amps.
Click to expand...

Try short circuiting the output, your output MOSFETs and fuses will blow faster than you can blink an eye. For added effect do this at a high output rating, i.e. driving the amplifier and connected loudspeaker at considerable volume, now you will see sparks fly 😀

Best regards,

Sander Sassen
http://www.hardwareanalysis.com
 
#10
Nothing Fried in the amp...but it fried a 20MFD cap connected as a shunt to check out capacitive load drivabilty...that all....

One question...In my POST filter feedback amp when no load connected..i.e. open circuit ..does the feedback automatically take cares of Q of Filter.... when no load is connected...I have cliiped the amp with open circuit and nothing happened...
amazed...

K a n w a r
 
#12
LOL,

Don't worry folks i've already tried that one! Not by intent, i was running the amp into a dummy load with wobbly croc clips on the output terminals, of course they wobbled toward each other then the power supply decoupling resistors fried open circuit ( saved most of the amp ). Even the smallest signal on the output instantly blows these amps due to the very high damping factor. The amp just stuffs more and more power into the output terminals to try and get it to reproduce the input signal ( it does on mine anyway ). You could say our amps are TOO good for their own good LOL And yes, i take back my statement of these amps being almost undestructible, they are extremly delicate when it comes to short circuits or capacitive influences in the modulator section ( your fingers for instance ). However i will say that under normal operation the classD amplifier is very robust and almost impossible to damage by overdriving or overloading ( as long as its not a sudden short ).

Have fun all,
Mad.P
 
#14
Nitrate,

Indeed, that's the culprit with these amplifiers, they'll continue to try and drive even a 0-ohm load with resulting excessive currents that'll either blow the fuses, or the MOSFETs. I've been using current restricting resistors as well, and have seen them glow red-hot after a shortcircuit. As for fuses, I'm currently using 6.3A Slow on my PSU and they're too slow, I lost two pairs of MOSFETs already due to crocodile clips touching each other and a woofer shortcircuiting its voice-coil.

Anybody thought up a effective short-circuit protection already? I like the way Hypex does it, but I'm a little reluctant to try and find out of it works, as that'll mean shorting a perfectly fine UcD180 under load. Any ideas?

Best regards,

Sander Sassen
http://www.hardwareanalysis.com
 
#15
One question...In my POST filter feedback amp when no load connected..i.e. open circuit ..does the feedback automatically take cares of Q of Filter.... when no load is connected.
Click to expand...

The most accurate answer is: It depends !

This simple feedback topology is still prone to instability with critical loads. You seem to be on the safe side when it survived 20 uF of capacitive load and clipping into open output.

Regards

Charles

Edit: The most interesting question: How does it sound ?
 
#16
Thanks Charles....

I have tested both pre & post filter feedback topologies under your guidance....During LIVE Vocal singing midrage test..pre-Filter feedback has more tranperancy with defining the image of vocals...I dont know it why...maybe you have some thoughts on this too....

K a n w a r
 
#18
Hi Sander,

Mine is External Clocked..3 Level PWM SWFQ@270KHZ ..2KW@2Ohms.....
I have implemented a resistor in series with lower rail which is connected to FET source terminal of Bridge amp for sensing and activating 555 timer for 5 seconds for muting the input signal of amplifier ....

K a n w a r
 
Status
Not open for further replies.
Top Bottom