Class D amplifiers have very little phase shift


Too many diagrams to post here, so I just blogged it:

https://inatinear.blogspot.com/2020/02/class-d-amplifiers-do-not-have-horrible.html

The 20 degrees at 2 kHz argument is bunk.
erik_squires
I meant ,misleading the way someone was trying to use the graph by saying ice 1200 modules had a huge frequency phase drop at 2khz.
I meant ,misleading the way someone was trying to use the graph by saying ice 1200 modules had a frequency phase drop at 2khz.

@djones51

You are right.

I just meant to say that the geek who put it together never intended it to say what is being claimed. I make a lot of plots, so I feel sympathy for having your data ripped off to mean something you never intended. :)
Somewhere out there is a person who is so concerned with this thread his digestion is in serious danger of shutting down. 



into almost negative numbers
Not almost, negative. When a voice coil is flying backward (relative to the now-changed drive signal), it is a generator of back emf.

We can argue about how long it is out of phase, but the fact remains.
Just agreeing and reinforcing what you said. You were too timid :-)

Now, the practical question is "how well does the amp control the voice coil (aka damping)?" If its very, very good, this overshoot and negative emf will be less. Not zero, but less. No i have not measured - its very hard to do so with non-repetitive signals which is where the problems would likely lie.

BTW i found the blog interesting but need to go backa nd think about what the (other party’s) original chart really meant. Unloaded? Hard to say what it is. Amps frankly are pretty easy if it weren’t for the damned loads :-)
I've seen that graph used on DIY and ASR to claim the same thing. Most of the stuff posted there is way over my head, I never post on those sites just read them so I was trying to figure out what the deal was with this graph and why is didn't  mean what the guy was saying.