TDA7052A - power, & (real world) heat levels ...Sanity Check sought! - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

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
Reply
 
Thread Tools Search this Thread
Old 9th August 2009, 09:32 AM   #1
diyAudio Member
 
Join Date: May 2008
Default TDA7052A - power, & (real world) heat levels ...Sanity Check sought!

I'm using a TDA7052A to drive a coil that's 9.2 Ohms (the end device isn't important here!)

OK, so I put a 330Hz sinewave into the chip & crank the input level until the signal is showing 3V peak to peak output across the coil - which is about the level I need it at. But at this level, the TDA7052A gets very hot (ie I can only press my finger firmly on the chip's top surface for a second or two).

So, are these following figures correct...

3V peak to peak = 1.062V RMS (ie multiply by 0.354 )

Current flowing through coil = V/R, therefore 1.062/9.2 Ohms = 118mA

Total power = VI, therefore 1.062 x 0.118 = 125mW

So with a 3V peak to peak sine wave across the coil, this TDA7052A is only running at about 125mW, the datasheet says it can output 1W (which is about 8X the level where I already think it is getting too hot!)

Have I stuffed up with my calculations...or am I just underestimating what this tiny little package can disappate safely?
  Reply With Quote
Old 9th August 2009, 09:41 AM   #2
MaxS is offline MaxS  France
diyAudio Member
 
Join Date: Mar 2006
Location: France
Default Coil use : welder ?

Hello,

If I'm right : you are driving a coil in sinusoidal current.

A coil has complex impedance : Z = R + j L 2 Pi 330.

But have a look, a coil is charged by current and gives back some voltage in the chip. I do not know how fine is your electronic knowledge but I want let you know it is like get a punch in your head. We do not like that !



Regards,

MaxS
__________________
Ca marche pas ! Tu ne l' as pas branché non plus ....
  Reply With Quote
Old 9th August 2009, 11:58 AM   #3
diyAudio Member
 
Join Date: May 2008
Ok, I've solved my problem - doh, of course, it's a BTL chip & I was only scoping the positive leg - therefore the output signal is not 3V peak to peak, but 6V peak to peak.

therefore (if my figures are correct)...

6V sine signal peak to peak = 4.24V RMS (ie peak to peak voltage x 0.707)

Coil DC resistance is 9.2 ohms and its inductance is 1.7mH , but at 330Hz, overall resistance (impedance) is 9.98 ohms. (http://www.cvs1.uklinux.net/calculators/ )

Therefore current = Voltage/resistance, 4.24V/9.98 ohms = 425mA

Power = VI, 4.24V x 0.424mA = 1.8W

No wonder it's getting hot ...I need a more powerful chip!
  Reply With Quote
Old 9th August 2009, 04:19 PM   #4
mjf is offline mjf  Austria
diyAudio Member
 
Join Date: Jan 2009
Location: Austria
hello.
what power supply voltage do you use with this opamp?
have a look at the datasheet..........with 6v supply and 8 ohm you will get around 1w.........and with 10ohm probably 0,9w .
greetings........
  Reply With Quote
Old 9th August 2009, 05:08 PM   #5
diyAudio Member
 
Join Date: Dec 2002
Location: Hungary/ Budapest
Quote:
Originally posted by HankMcSpank
Ok, I've solved my problem - doh, of course, it's a BTL chip & I was only scoping the positive leg - therefore the output signal is not 3V peak to peak, but 6V peak to peak.

therefore (if my figures are correct)...

6V sine signal peak to peak = 4.24V RMS (ie peak to peak voltage x 0.707)

Coil DC resistance is 9.2 ohms and its inductance is 1.7mH , but at 330Hz, overall resistance (impedance) is 9.98 ohms. (http://www.cvs1.uklinux.net/calculators/ )

Therefore current = Voltage/resistance, 4.24V/9.98 ohms = 425mA

Power = VI, 4.24V x 0.424mA = 1.8W

No wonder it's getting hot ...I need a more powerful chip!

Hi,

6V p-p is 3Vpeak, which is 2.12Vrms
With this voltage you get ca 0.45Wrms...

Tamas
  Reply With Quote
Old 9th August 2009, 05:23 PM   #6
diyAudio Member
 
Join Date: May 2008
mjf - I was using 9V to the TDA7052A as supply voltage.


ttako - yes, I think I made a mistake in my previous calculations (I'm rusty which is why I'm posting here for the sanity check!). Let me walk through this with you....

I concur with the 2.12Vrms, but to work out the RMS power, we need at least one more bit of data - either current or resistance.

The coil is 9.2 ohms, but at 330Hz the actual total impedance is 9.98 Ohms.

So we have a 2.12V RMS signal across an impedance of 9.98 ohms, therefore the current through the coil must be 0.212mA.

Power = V x I

therefore power through the coil is 450mW

(which I guess concurs with your 0.45W!)

Have I got it now then?

If so, then perhaps I don't need a different (beefier) audio power chip, but at 0.45W it seems very hot - I can't imagine that being twice this hot (1W) is going to be good for it!
  Reply With Quote
Old 9th August 2009, 06:00 PM   #7
diyAudio Member
 
Join Date: May 2008
Just a quick typo in that last post (& the edit button seems to have gone?), it should have read...

So we have a 2.12V RMS signal across an impedance of 9.98 ohms, therefore the current through the coil must be 212mA.
  Reply With Quote
Old 11th August 2009, 01:46 AM   #8
wwenze is offline wwenze  Singapore
diyAudio Member
 
Join Date: Mar 2008
This thing is rated for 85 degrees, which would be pretty hot if you touch it. Best to check with a thermometer.

And if you're paranoid, just heatsink it. Though I doubt it'd be necessary.
  Reply With Quote
Old 11th August 2009, 12:17 PM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
go and read some literature on power amplifier driving an inductive load.
Start with ESP site.
He shows just how bad the amplifier dissipation can become when the reactance starts to exceed 30degree phase.
__________________
regards Andrew T.
  Reply With Quote

Reply


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
Circuit Sanity Check: +15V, -15V, +9V Power Supply miallen Power Supplies 4 18th July 2009 07:18 PM
F1 Voltage sanity check rpafenberg Pass Labs 7 28th March 2009 10:42 AM
Sanity Check ..... please Lostcause Digital Source 0 16th October 2008 06:19 PM
This model can't be right... need sanity check NogginBoink Subwoofers 4 30th July 2005 09:14 PM
Sanity check planet10 Multi-Way 14 7th March 2004 10:15 PM


New To Site? Need Help?

All times are GMT. The time now is 03:37 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2