Distorsions in class D

[ChocoHolic]

Hi ClassD !

I plan to check that thread since one week, but I am getting afraid more and more by the horrible length....
....but I know, I really SHOULD !!!

Who can read- takes advantage! .... an already experienced topic....

Thanks
Markus

[classd4sure]

Hi

Don't be afraid of the length of it we went to alot of effort to work things out so life could be easier for people interested in class d..

I have looked at all these IC's before and I found it hard to nail it down to anything workable as they are all designed for such things as power supplies or pfc, I'm sure there must be one out there somewhere that could be made to work but the time required to find it is more than I can stand. Some are current feedback some voltage some both some phase some hysteresis some both...It's very confusing. Then you see Bruno's nice little UCD comparator..and you'll feel it's pull sucking you in.

I think it's likely safe to skip the first few pages at least, but there's good info throughout. Not saying you should give up and start over with a new design but I'm sure you'll get some good ideas from it, I think you'll really like the comparator from it for one thing. Dual floating outputs 180 deg. out of phase with a nice low part count. Would likely take less time making that than in finding a suitable PSU chip that could be adapted. I've looked high and low for one before but they either lacked features or speed..or something. Even the fabled Mueta IC will require 4 op amps, transformer...etc.

Best Regards,
Chris

[Pafi]

Hello Chris!

You are very lucky! For some months Fairchild doesn't send free samples to Hungary, I don't know why! Furthermore it seems to be impossible to buy from them via distributor either.

Any idea?

[john curl]

Pafi, rules exist, usually for good reason. Get your friend in Canada to get you samples.
For example: About 1980, I had to supply Fairchild transistors to the University of California, Berkeley for a real project, to try. They were only 50 miles away! Still, they were a university, not a real company. You are not being excluded without a general guideline being in place.

[classd4sure]

Originally posted by Pafi
Hello Chris!

You are very lucky! For some months Fairchild doesn't send free samples to Hungary, I don't know why! Furthermore it seems to be impossible to buy from them via distributor either.

Any idea?

Hi, I must say I haven't actually tried obtaining any of their samples yet. Maybe I should try monday morning and see....Might not look too good if i tried to order them at 4am sunday
Have you tried emailing them to find out what the problem is?
Regards,
Chris

[Pafi]

Thank both of you!

Chris!

The registration done by computers, so you can order at any time! They deny my requests immediately as I log on. They write: "We are currently unable to process your samples request." "Currently", but this is permanent.

Please inform me, if your order is accepted!

I haven't try to email them. I asked their local distributor, who said that this is a world-wide problem, there aren't enough SMPS semiconductor device produced to satisfy needs. But then how can they send samples to others?

[classd4sure]

Hi, yeah sounds like something is up.

Have you tried creating a new account, new email..etc?

What is they allow? Two samples per device? Maybe they only let you try two or three.. I will let you know but I'll wait until business hours just in case it red flags me for ordering at an oddball time or something.

[Pafi]

"Have you tried creating a new account, new email..etc?"

I met others who experienced the same thing.

They used to allow 10-25 samples per device, depending on part number. Now I can't reach the point where I could specify quantity, or anything. I quess you just believe that you will order sample. I'm really sorry! Their products are (would be) really good!

[classd4sure]

It took half a dozen tries but I got through the order process. Don't know if it will be approved though. 4 FDP3682's...nice!

[Bruno Putzeys]

4 samples... jeez. Getting an amplifier circuit from the first sketches to something useful requires upward of 50pcs.

IMO, manufacturers of class-d-esque components (fets, coils, drivers etc) would do well to have a flexible sampling regime towards hobbyists and students.

The whole world is currently bracing for an onslaught of new class D products, but the developers aren't there! Schools no longer teach analogue electronics (let alone power) and companies can't or won't invest in proper r&d (quarterly result fixation).

Many audio companies are simply reassigning their "AB" designers to "D", with predictable end results. We're even seeing a backswing in the Deep East where companies are moving back to class AB because they even can't handle application of class D IC's (the local app engineers aren't helping much either).

The only chance we have at getting class D off the ground is facilitating enthousiasts to do their hobby so some can become pros in due time. For the companies to provide easy access to samples is a small investment, and the returns could be huge.