Chips blow up when powering the amp. - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 25th December 2006, 08:21 PM   #1
diyAudio Member
Join Date: Apr 2006
Location: buenos aires
Default Chips blow up when powering the amp.


a couple of years ago i was building a 6w+6w amp using tpa1517, and it kept burning the chip every time i'd turn it on.
after blowing a couple of them i changed the power switch from "after the PS" to "after transformer, before diodes". it stopped burning, i never knew exactly why this happened.
see figures 1 and 2.

this new era finds me building a small sub woofer plate amp using TDA2040 and a switching power supply (the one HP printers use, 16v@650mA + 32v@950mA).
apparently i made the same mistake at my first desing. as a result of this, the chip is history (short circuit between output and Vs).
this time, as we are talking about a SMPS, i don't know if the same change i did before will fix it. any way, it would be quite a mess trying to place an interruptor between transformer and diodes inside the SMPS.
the first design (the one burning the chip) is fig. 3.
will interrupting the mains save me ?see fig. 4.
or should i replace the 220uF for a 1000uF or 2200uF instead?
i don't know. you tell me...

i'd appreciate a lot your helping me with a solution, just a piece of advice, or an explanation of this burning chip problem.

thanks a lot in advance!

Click the image to open in full size.

PS: the amp circuit is ok. it's the one found in the TDA2040 datasheet as a typical application for single supply and i've seen it working well with a linear PS interrupted "after transformer, before diodes", and with another one interrupted at the mains.
  Reply With Quote
Old 25th December 2006, 08:50 PM   #2
teemuk is offline teemuk  Finland
diyAudio Member
Join Date: Nov 2004
Location: Suomi, Finland
I don't know about SMPS but I guess the reason why your chips blew in the first scenario was the sudden voltage and current introduced to them: The potential will shift very fast from 0 to whatever and I guess the chips just could not take the transient. If you place the switch before the rectifier it will introduce a delay since the supply voltage will have to rise ("smoothly") from 0 to whatever as the reservoir capacitors charge.

In my opinion it's always best (safest, less power consuming) to just switch off the mains as in figure 4.
  Reply With Quote
Old 25th December 2006, 08:58 PM   #3
diyAudio Member
Join Date: Apr 2006
Location: buenos aires
thanks a lot!

i thought something like that was the problem, but then another question arises in my ignorant brain.

as SMPS oscillation is way faster than 50Hz, won't tension go up fast anyway? maybe not fast enough to kill the chip. maybe frequency has nothing to do and the time required to fill the caps is related to the energy required. so. it's related to the power delivered by the transformer (amplitude of voltage and current delivering capability, not frequency).

thanks a lot indeed.
  Reply With Quote
Old 25th December 2006, 09:21 PM   #4
Duo is offline Duo  Canada
diyAudio Member
Duo's Avatar
Join Date: Jun 2002
Location: Victoria, BC, Canada
Send a message via ICQ to Duo
in your original 6W amp, with the linear power supply, how close was the power supply voltage to the voltage limit of the chips?

I'm thinking of the fact that linear supplies, when powered up and unloaded, will reach a much higher voltage in some cases than when loaded. When you throw that output switch, this high voltage appears at the chip until the chip discharges the capacitor down to a normal level. If the chip was rated for less than this higher voltage, it could have fried.

The above is unlikely, but then again, it's seemingly unusual for circuits like yours to fry the way yours did.
  Reply With Quote
Old 25th December 2006, 09:35 PM   #5
lineup is offline lineup  Sweden
diyAudio Member
lineup's Avatar
Join Date: Dec 2005
Location: the north
I suppose
it is your TDA2040 chip that is blowing up.

You would imagine to draw PCB for such a simple
but not bad amplifier as the good old TDA2040
wouldn't be difficult - not be at all critical with Layout.
But I have read several TDA2040 projects at websites (Search)
as well as read posts from Chip Amps builders,
saying you have to be careful when layout boards for TDA2040.

You should study this PDF ( I guess you have it ).
Why do you think they have bothered
to show you layout suggestion - for EVERY CIRCUIT in that PDF???
... you do not often see this is datasheets ...
My Guess it is more important with layout, than usual.

Especially you should notice:
- How the ground is drawn.
- How the connections +V, 0V and LSP-GND and Input-GND are done.
- In what order components are joined to Ground plane and rails.
- How supply bypass capacitors are put
- These Caps are in my attached diagram: C3(220uF), C5(100nF)
- Also R6 + C6 can be of great importance. To stop oscillation burn outs

Attached Images
File Type: png tda2040-singlesupply-layout.png (46.7 KB, 343 views)
  Reply With Quote
Old 25th December 2006, 11:53 PM   #6
diyAudio Member
Join Date: Apr 2006
Location: buenos aires
actually i'm using that same PCB.

  Reply With Quote
Old 26th December 2006, 12:13 AM   #7
diyAudio Member
Richard Ellis's Avatar
Join Date: Sep 2006
Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.
Default Sizzle..

Yes the switching should be at the mains on the primary side....I would bet you are indeed over the limit on the B+ supply voltage, there is really no reason for it to blow with a proven design with the switching as described.
Regards from the"Ocean of silver"___________
_______________________________________Rick....... ......
  Reply With Quote
Old 26th December 2006, 12:45 AM   #8
diyAudio Member
Join Date: Apr 2006
Location: buenos aires
maximun ratings are 22V and 40V, for TPA1517 and TDA2040.
i'm feeding them with 14V and 32V respectively. i don't know if that's too close.

thanks from "good airs", in the neighbourhood of "slaughterhouses".
  Reply With Quote
Old 26th December 2006, 01:01 AM   #9
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
Zen Mod's Avatar
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
use circ No.4 and try putting shunt resistor from smps output to gnd

calculate it for some 3 to 5 W will do the job
ya know that PC power supply is fully and safely operational only with some nice and predictive load across 5V output?
I think that same case is here
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 26th December 2006, 01:17 AM   #10
diyAudio Member
Join Date: Apr 2006
Location: buenos aires
this PS has a 32V/950mA and a 16V/650mA output, would it be the same placing in one or another outputs? or must it be connected to the output that's burning the chip?

i ask this because i'll be using the 32V output of the PS close to its limit when playing loud, but the 16V will be feeding only a filter preamp with negligible power consumption.
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
NAD fuses, slow blow or fast blow? AllCaster Solid State 3 25th October 2009 06:11 PM
pcb layout for powering 24 THAT 1240 chips audio_moksha Parts 3 1st September 2008 08:53 PM
(Loaded) THE CHIPS DO BLOW impsick Chip Amps 0 2nd January 2007 01:13 PM
Blow up once, Blow up twice and Blow up somemore S.C Chip Amps 14 6th March 2005 12:09 AM
Will This Blow Up? Trout Instruments and Amps 8 6th February 2005 12:52 PM

New To Site? Need Help?

All times are GMT. The time now is 12:25 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2