caramoan tour package

caramoan tour package

caramoan tour package

Author Topic: 150W+150W Class D Amplifier Design Secrets: How PCB Layout affect performance  (Read 5698 times)

Offline Born2BeWired

  • Technical People
  • Diesel Generator
  • *****
  • Posts: 1514
  • Pogi/Ganda Points: 212
  • Gender: Male
  • De omnibus dubitandum
Before we start, I enjoined you readers to try out this experiment aimed at preventing the main body of this thread from being fragmented to pieces. Keeping the main body flowing uninterrupted will make the thread more readable, and easier for us to track back for information. ;)

This is how I propose we do it:

1. This will be our main thread, it will be build piece by piece. Do not post anything until the main thread article is completed. I will let you know when it is completed.

2. Questions, reactions, and comments will surely come as the discussion progress. A separate Q&A thread running in parallel with this main thread is opened for this purpose. Please post your questions and other concerns related to this thread through this link:

http://www.electronicslab.ph/forum/index.php?topic=28009.msg506818;topicseen#msg506818
Electronics <- Once you got a taste of it, you will never get enough.

Insanity <- Doing the same thing, expecting different results.

"The more I learn, the more I am humbled."

Philippine Electronics Forum


Offline j a y k e z

  • Gas Turbine
  • **
  • Posts: 2032
  • Pogi/Ganda Points: 185
  • Gender: Male
  • gimmegaggigsss
+1 sis at pa sub na din thanks

Philippine Electronics Forum


Offline Born2BeWired

  • Technical People
  • Diesel Generator
  • *****
  • Posts: 1514
  • Pogi/Ganda Points: 212
  • Gender: Male
  • De omnibus dubitandum
Abstract:

Class D audio power amplifier circuits, once upon a time, needed to be very complex and hard to build. For some time, it was treated more as an intellectual curiosity, rather than a practical circuit that you can build as a product.

Todayís high integration ICs not only made the Class D amplifier design process simple, it practically took the fun out in designing one. Gone were the days when you have to work complex math with literally each component in the circuit.  There is little work left to do for the circuit designer, other than following the application circuit recommended by the IC manufacturer, and then perhaps tweaking a component or two in an attempt to fine tune the performance.

Given the high efficiency advantage and ease of design now offered by class D amplifier ICs, one should expect a horde of hobbyists building their own class D amplifiers by now. But that is not happening.

In my opinion, this lack of acceptance from the hobbyists can be attributed to two things: One is the rarity of success stories from builders. Class D amplifier earned a reputation as hard to tame, hard to build circuit.  Those who did made their class D ďworkĒ, on the other hand, usually laments about the apparent poor audio quality of class D compared to traditional analog amplifiers. This so-called poor audio quality already sunk deep into the psyche of a large number of hobbyists. The truth is, a well designed Class D can achieved performance that can rival its analog counterpart. 

These misconceptions (and failures) are largely to blame due to our lack of understanding to the special PCB LAYOUT requirement of class D amplifiers. It is the aim of this article to share with you experiences and difficulties I encountered in building one - a 150W + 150W Class D amplifier based on TDA8950J  IC. I will show you how my initial PCB layout led to a number of problems, and what modifications were made to fix these. I hope this article will provide you a working knowledge and realization on the importance of PCB layout to circuit performance.

To be continued...


No questions and reactions will be entertained in this thread. Please post your concerns in the Q & A thread using the following link:

http://www.electronicslab.ph/forum/index.php?topic=28009.msg506818;topicseen#msg506818

Electronics <- Once you got a taste of it, you will never get enough.

Insanity <- Doing the same thing, expecting different results.

"The more I learn, the more I am humbled."

Philippine Electronics Forum


Offline Born2BeWired

  • Technical People
  • Diesel Generator
  • *****
  • Posts: 1514
  • Pogi/Ganda Points: 212
  • Gender: Male
  • De omnibus dubitandum
Gentlemen, Ladies, and those who are having trouble knowing what they are, I take the pleasure to present to you:

150W + 150W Class D Amplifier based on NXP TDA8950J
(Photo showing prototype using initial and uncorrected PCB Layout)





To prepare yourself for this discussion, please chant this mantra repeatedly as you wait for the next installment:

PCB layout is a hidden circuit in my schematicÖ.
PCB layout is a hidden circuit in my schematicÖ.

This mantra will clean your mind and soul of any prior prejudice that may bar you from accepting some of the truth about to be discussed in this article. You will also find it a great way to annoy people around you. ;D

To be continued.....

--------------------------------------------------------------------------------
No questions and reactions will be entertained in this thread. Please post your concerns in the Q & A thread using the following link:

http://www.electronicslab.ph/forum/index.php?topic=28009.msg506818;topicseen#msg506818
Electronics <- Once you got a taste of it, you will never get enough.

Insanity <- Doing the same thing, expecting different results.

"The more I learn, the more I am humbled."

Philippine Electronics Forum


Offline labgruppen

  • Diesel Generator
  • *
  • Posts: 1061
  • Pogi/Ganda Points: 110
subscribing.

Philippine Electronics Forum


Offline Born2BeWired

  • Technical People
  • Diesel Generator
  • *****
  • Posts: 1514
  • Pogi/Ganda Points: 212
  • Gender: Male
  • De omnibus dubitandum
Things you need to know before proceeding:

Parental Guidance suggested. Some contents of this article may contain disturbing assertions that may elicit violent responses.  Those who still dream in an ideal world will be in for a rude awakening.

PCB layout effects, at first encounter, may appear subtle and distasteful to common sense. You canít always trust common sense. Temporary suspension of disbelief is oftentimes necessary to keep your mind open towards understanding it.

Getting TDA8950J. Samples? Forget it. NXP does not entertain request samples from ordinary mortals like us. I brought mine from mouser electronics. I am not sure if you can get this part from Raon. But I am told e-Gizmo may have this on stock in limited quantity.

Patience needed. I have to beg for your patience. Pressing matters will conspire to keep me from making regular updates, but I will try my best to make updates as frequent as possible.

Anti-bragging task force. When I sense people are awed over my intellectual prowess, ;D ;D I usually get carried away, and will likely indulge myself into an orgy of bragging over nothing to impress even more.  I hope that analog & audio gurus such as tita labgruppen (he's here), Tony, TintopHack, Danny (enumerated in the order of increasing age) and switching gurus like Ate Glutnix,  rdpzycho , Tiktak, and the rest of the gang, will be here to restrain and correct me.

TDA8950J datasheet can be downloaded from www.nxp.com. Donít look for application notes and examples. There is none.

Thread hijackers: Die! Die! Die!  ;D ;D ;D Seriously, I beg you to stay on the topic if you can. Ok, ok, Iíll say it:  pleaaaseee!

To be continued.....

--------------------------------------------------------------------------------
No questions and reactions will be entertained in this thread. Please post your concerns in the Q & A thread using the following link:

http://www.electronicslab.ph/forum/index.php?topic=28009.msg506818;topicseen#msg506818
Electronics <- Once you got a taste of it, you will never get enough.

Insanity <- Doing the same thing, expecting different results.

"The more I learn, the more I am humbled."

Offline rdpzycho

  • Technical People
  • Solar Power Satellite
  • *****
  • Posts: 11369
  • Pogi/Ganda Points: 694
  • Gender: Male
  • Respect Begets Respect
    • rdpzycho
No questions and reactions will be entertained in this thread. Please post your concerns in the Q & A thread using the following link:

http://www.electronicslab.ph/forum/index.php?topic=28009.msg506818;topicseen#msg506818


first things first tita Born, 'yung link din nito ang na-copy niyo. ;D

eto 'yung Q&A thread:

http://www.electronicslab.ph/forum/index.php?topic=28011.0
‎"Divide each difficulty into as many parts as is feasible and necessary to resolve it."
- Rene Descartes

"For every difficult problem there is always a simple answer and most of them are wrong."
- Clayton Paul

Offline BANNEDMemberAccount

  • Gas Turbine
  • **
  • Posts: 2747
  • Pogi/Ganda Points: 130
  • You have No GOD?, You have No Peace of mind.
    • Hay tita lengwahe mo bading na bading halata na talaga, napaka-awkward! gack!!!
sir tanong ko lang kapag ba IC ang ginamit nde transistorize diba required sa circuit yung spider/star grounding para iwas sa humming?
Wag HIHITHIT ng Katol para hinde Tamang Hinala  Account is permanently BANNED due to Accumulation of forum rules and violations.

Offline _basura_man()

  • Diesel Generator
  • *
  • Posts: 1102
  • Pogi/Ganda Points: 45
  • Think outside the box
up!+100 tita born,subscribing:-)
PICMicro Afficionado

Offline kinyo

  • Size D Battery
  • ******
  • Posts: 376
  • Pogi/Ganda Points: 31
150W X2 pero anliit ng pcb? ayus!

subscribing   ;D

Offline lovehack

  • Size AAA Battery
  • ***
  • Posts: 66
  • Pogi/Ganda Points: 4
  • Error 105 (net::ERR_NAME_NOT_RESOLVED): Unable to
150W X2 pero anliit ng pcb? ayus!

subscribing   ;D

yan ang uso ngayon kahit kasing liit na posporo...... nakakaproduce na nang 1000w....hehehe :)
.
The server at yahoo.com can't be found, because the DNS lookup failed. DNS is the web service that translates a website's name to its Internet address. This error is most often caused by having no connection to the Internet or a misconfigured network.

Offline _basura_man()

  • Diesel Generator
  • *
  • Posts: 1102
  • Pogi/Ganda Points: 45
  • Think outside the box
yan ang uso ngayon kahit kasing liit na posporo...... nakakaproduce na nang 1000w....hehehe :)
.
ha?saan ito link naman please  ;D ;D ;D
PICMicro Afficionado

Offline cosmo

  • Diesel Generator
  • *
  • Posts: 1073
  • Pogi/Ganda Points: 102
  • Gender: Male
  • I will always believe in You.
150watts @4ohms 37volt split power supply sabi sa datasheet
100watts @6ohms 39volts supply..

pwede rin btl mono 300watts @8ohms 37volts supply

galing....
ďA man is but the product of his thoughts. What he thinks, he becomes."
--Mahatma Gandhi

Tindog Tacloban, Tindog Sinirangan Bisayas

Offline cosmo

  • Diesel Generator
  • *
  • Posts: 1073
  • Pogi/Ganda Points: 102
  • Gender: Male
  • I will always believe in You.
meron din typical application dun sa datasheet...wala nga lang pcb layout..

http://www.nxp.com/documents/data_sheet/TDA8950.pdf
ďA man is but the product of his thoughts. What he thinks, he becomes."
--Mahatma Gandhi

Tindog Tacloban, Tindog Sinirangan Bisayas

Offline zrehtiek/keitherz

  • Lead Acid Battery
  • *******
  • Posts: 772
  • Pogi/Ganda Points: 45
  • Gender: Male
  • PhilRoboKit Anito
mga pasaway -_-

Offline rdpzycho

  • Technical People
  • Solar Power Satellite
  • *****
  • Posts: 11369
  • Pogi/Ganda Points: 694
  • Gender: Male
  • Respect Begets Respect
    • rdpzycho
sir tanong ko lang kapag ba IC ang ginamit nde transistorize diba required sa circuit yung spider/star grounding para iwas sa humming?

narito ang sagot:

http://www.electronicslab.ph/forum/index.php?topic=28011.msg506958#msg506958
‎"Divide each difficulty into as many parts as is feasible and necessary to resolve it."
- Rene Descartes

"For every difficult problem there is always a simple answer and most of them are wrong."
- Clayton Paul

Offline Born2BeWired

  • Technical People
  • Diesel Generator
  • *****
  • Posts: 1514
  • Pogi/Ganda Points: 212
  • Gender: Male
  • De omnibus dubitandum
More Reminders

I will not delve into the details of class D circuitry to keep this article as short as possible. We will focus our study to the PCB layout effects. Baka kasi humaba ng humaba and discussion tuloy di natin matapos. ;)

Schematics, initial measurements, and other technical info, including PCB layout, will be published later when we start tackling the technical details of this amplifier.

Motivations for building the project

-   I was inspired by recent surge of interest to class D amplifiers and audio amplifiers in general by members of this forum.
-   I thought it is a good excuse for me to indulge myself once again into the exhilarating and magical world of analog electronics.
-   It will make a good case study for the benefit of our young and uninitiated designers.
-   I am jealous and green with envy to the attention other members get with their accomplished amplifier projects.  ;D

--------------------------------------------------------------------------------
No questions and reactions will be entertained in this thread. Please post your concerns in the Q & A thread using the following link:

http://www.electronicslab.ph/forum/index.php?topic=28011.0

Salamat sa correction ate rdp ;D

Electronics <- Once you got a taste of it, you will never get enough.

Insanity <- Doing the same thing, expecting different results.

"The more I learn, the more I am humbled."

Offline Born2BeWired

  • Technical People
  • Diesel Generator
  • *****
  • Posts: 1514
  • Pogi/Ganda Points: 212
  • Gender: Male
  • De omnibus dubitandum
The TDA8950J has elaborate protection built-in. It will protect itself from damage to just about anything you throw at it, except my PCB layout.  ;D Here is the story behind it.

The Killer PCB Layout

I made a PCB layout and  built on it the 150W+150W class D amplifier essentially using the application circuit recommended in the datasheet. After a thorough visual inspection of the finished prototype, it was time to power up the circuit, and that I did.

Whenever I power up an amplifier the first time, I do it as a matter of routine with the load (speaker or dummy load) disconnected. This initial step will (usually) save some of my precious components from total annihilation in case I went remiss in parts of the circuit. If no smoke or explosion occurred, I measure the idle current and amplifier output DC voltage as a matter of procedure.  If something is seriously wrong with the amplifier, in will usually reveal itself within these first few steps.

Round 1: First blood

And so as a matter of fact it did. There was no explosion, but one channel has its output stucked on one of the supply rail. The TDA8950J is equipped with protection circuitry that will automatically shut down everything in case it detects this kind of fault. And so the other channel is out too. I looked for the source of the short, it turned out, the output of TDA8950J IC itself shorted out, and has to be replaced. What caused the failure? No definite idea at this point, but ESD came to mind. I was not wearing any ESD prevention when I was handling the TDA8950J. Maybe, thatís what killed it.

Round 2: The face of Opportunity

I replaced the TDA8950J with a new one. I was concerned that my PCB, which is handmade, may not survive another IC replacement cycle. I fashioned a socket for the TDA8950J so that no soldering will be necessary in case the IC needed to be replaced again. This extra step proved its worth later.

This time, I checked the IC output and the rest of the pins for any short or low resistance path using a DMM. When everything checked well to my satisfaction, I hooked up an oscilloscope to monitor one amplifier output and then applied power once again.

The exact same thing happened! One output shorted out as soon as power is applied! I got excited by the development (believe it or not!), it is clear to me now that this class D amplifier is not as boring as I initially expected. I will learn something new on this one. After all, this is what project building is all about- learn new things, donít you agree?

to be continued...

--------------------------------------------------------------------------------
No questions and reactions will be entertained in this thread. Please post your concerns in the Q & A thread using the following link:

http://www.electronicslab.ph/forum/index.php?topic=28011.0

Electronics <- Once you got a taste of it, you will never get enough.

Insanity <- Doing the same thing, expecting different results.

"The more I learn, the more I am humbled."

Offline danny

  • Technical People
  • Solar Power Satellite
  • *****
  • Posts: 6497
  • Pogi/Ganda Points: 395
  • Gender: Male
nice tita +1 for you

subscribing  :)
danny

Offline Born2BeWired

  • Technical People
  • Diesel Generator
  • *****
  • Posts: 1514
  • Pogi/Ganda Points: 212
  • Gender: Male
  • De omnibus dubitandum
Round 3: Insulation Breakdown?

With my third TDA8950J nervously seated on its socket, I went more slowly and more careful this time. I want to catch what causes this problem. If the IC keeps shorting out as quickly as it did in the last two sorties, I may not get the chance to observe and determine the cause.

Post mortem analysis of the zapped ICs held some clues. The output did not completely shorted out, as in 0-ohm dead short. Instead, resistances in the order of 6 to 20 ohms were measured. The TDA8950 employs MOSFET at its output stage. Whenever a MOSFET fails and shows relatively high resistance short across its drain to source terminals, it is tell tale sign of insulation breakdown. Insulation breakdown can occur if the voltage across a MOSFET rises very rapidly, and overshoot past the maximum voltage the MOSFET can handle.

Armed with this suspicion, I applied power once again using power supply as voltage as low as the IC will allow, at +/- 12VDC. In a quick instant, a waveform showed up at the oscilloscope display! This is the expected waveform right at the IC outputs before the low pass filter, hence, it displayed the expected 380kHz PWM rectangular waveform. I touched the amplifier input with a bare finger as a quick test, and the output responded with a pulse modulated display. The amplifier is now working!  I zoomed the output PWM waveform, zeroing on the pulse edges where overshoots usually occurs. There are overshoots, put they seem low enough to cause any damage.

Slowly, I raised the power supply voltage. The ďoh f**kĒ level came at around +/-18VDC.

Round 4:  It ainít over yet

With only two TDA8950J left, I began to wonder whether I can make this work at all with the remaining pieces. I decided its time to connect the load, just to see what happens next.

Again, I powered up the circuit with +/-12VDC. There were signs of life. I fed a sine signal on one of the amplifier input. Sure enough, there is an output! The output waveform shows deformations indicative of a high distortion level, nevertheless, it is a significant progress over the three previous tries that resulted only in blowing up the ICs. Now I have something to work on. I slowly raised  the supply voltage. Parasitic oscillations showed up, but the amplifier kept working. I reached +/-20VDC and stopped there, deciding to investigate what causes the oscillations.

This is where things get even more interesting. During my probing and experimentation, which lasted for hours, the IC kept working. I figured out the distortion and parasitic oscillations that showed up is caused by problems with the PCB layout. I did not made any attempt to make and try any pcb layout modifications as yet, as my attention is fixed in finding out why the IC fails.  I can now examine the PWM output waveform in greater detail, but still, could not find the probable killer wave. And then, something happened. The wire connecting the load went loose and disconnected the load. This signaled the start of Round 5.

Round 5: A shocking realization

The IC amplifier self destroys when it is operated without load! This puzzling behavior is completely unexpected and not like anything I encountered working with audio amplifier. Lolo Danny was on line at that time, and I was able to open a short discussion with him. He did not believe me at first, even suspecting I am pulling a prank on him. Apparently, lolo Danny never encountered this problem either. In the end, he too would want to know.

With my last TDA8950 now in the death row, I proceeded with an all out effort to come up with a fix that will solve this problem once and for all. I redesigned the output filter, modify the output snubber network. Needless to say, these too failed. But I am not giving up. This just got so interesting that I canít quit now. I booked my order for another 5 pieces as I say my goodbye to the last TDA8950 I just put to death.

to be continued...

--------------------------------------------------------------------------------
No questions and reactions will be entertained in this thread. Please post your concerns in the Q & A thread using the following link:

http://www.electronicslab.ph/forum/index.php?topic=28011.0

Electronics <- Once you got a taste of it, you will never get enough.

Insanity <- Doing the same thing, expecting different results.

"The more I learn, the more I am humbled."

Philippine Electronics Forum


 

Privacy Policy

Contact Us: elabph@yahoo.com