HEATSINK QUESTION
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Solid State Talk all about solid state amplification.

 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
 28th January 2012, 11:33 AM #1 east electronics   diyAudio Member     Join Date: Jan 2006 Location: Athens GREECE HEATSINK QUESTION I am working in one application where one amplifier class AB will be placed in a specific housing outputs will be 1943 5200 power supply will be 35+35 volts and the duty will be casual low listening probably something like 10-15W at the very maximum Bias for the amplifier will be no more than 70 ma ( rough calculation i can even go lower ) Problem is that the heatsink will be one aluminum size 35cm x45 cm 2mm thick do you think that i might get away with it ? __________________ SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
 28th January 2012, 11:37 AM #2 KatieandDad   diyAudio Member     Join Date: Nov 2011 Location: UK As a rule of thumb that's not going to be enough. Your application wont need a big heatsink but it will still get quite warm. You are trying to dissipate 70V x 0.07A under no load = 5W. For reliability try to keep the output transistors below 65 Degrees C - they can run far hotter. Lets take a lovely summer day where the air temperature is 35 Degrees (I wish). The heatsink calculation is Tj = Ta + ( Tjc + Tcs + Tsa)P P is the power being dissipated - 5W in this case. Tjc can be gained from the transistor data sheet but is nominally in the order of 1.5 Tcs is down to the mica washer and is generally about 0.3 Tsa is the figure that we are after - Transfer of Heatsink to Air Tj is the maximum temperature that we want the transistor to reach (as stated 65 Degrees) Ta is the maximum air temperature (as stated 35 Degrees) Transposing the formula that gives us ((Tj-Ta)/P)-Tjc-Tjs = Tsa Or ( ((65-35)/5)-1.5-0.3 = 4.2 Degrees C/Watt Now if you do a bit of homework you can see what sort of heatsink you would need to meet this requirement. This is with NO SIGNAL applied. You will need to increase the figures when the amp is at FULL SWING. Last edited by KatieandDad; 28th January 2012 at 11:52 AM.
 28th January 2012, 11:38 AM #3 AndrewT   diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders 15W from a 50W amplifier will just about hit the worst case heat dump from the transistors to the heatsink. If you had said "normal music" levels of 1/2W to 2W, then I would point you to using the Pq as the heatsink load. From there you could estimate the Tc of the devices. But at 10W to 15W for domestic listening the heat load is going to be far greater than Pq. __________________ regards Andrew T. Sent from my desktop computer using a keyboard
 28th January 2012, 11:51 AM #4 east electronics   diyAudio Member     Join Date: Jan 2006 Location: Athens GREECE ok got it will make some tests and see how far i can go Due to the nature of the application i have to go like that ...one think i can change though is the thickness of the metal from 2mm to 3mm any comments on that ? also the shape of the aluminum is not flat ...its something like a W ...with the transistors located in the inner sides of the W ( i am trying to say that obviously a V or W shaped piece of metal will be more effective than a flat one Will also post pictures as we speak __________________ SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
 28th January 2012, 11:59 AM #5 KatieandDad   diyAudio Member     Join Date: Nov 2011 Location: UK The thickness of the plate will make little difference. It is how much alluminium is available to dissipate heat to the air around it. Hence the design of heatsinks. If you are limited in space available then you might have to consider forced cooling. (Fans - Water - Peltier )
 28th January 2012, 12:07 PM #6 KatieandDad   diyAudio Member     Join Date: Nov 2011 Location: UK Have a read of these articles. DIY Heatsink http://sound.westhost.com/heatsinks.htm Last edited by KatieandDad; 28th January 2012 at 12:09 PM.
 28th January 2012, 12:56 PM #7 geraldfryjr   diyAudio Member   Join Date: Feb 2008 Location: Jackson,michigan Here are a few online Heatsink Calculators that I think you may find useful, Heat Sink Calculator - heatsink design tools Heatsink Surface Area Calculator. enjoy !!! jer
Michael Chua
diyAudio Member

Join Date: Jul 2006
Location: Calais, ME
Quote:
 Originally Posted by sakis I am working in one application where one amplifier class AB will be placed in a specific housing.....
One option is to forced fan cool the heatsink. A 40x40mm 12V case fan may fit into your housing.

Another possibility is to use the housing as heatsink, provided it's possible.
__________________
ampslab

 28th January 2012, 05:33 PM #9 east electronics   diyAudio Member     Join Date: Jan 2006 Location: Athens GREECE hey Michael !!!! always very good to see you ...i will e mail you pictures ( if you have the time to see ) kind regards sakis __________________ SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
 28th January 2012, 09:26 PM #10 Michael Chua   diyAudio Member     Join Date: Jul 2006 Location: Calais, ME Hello sakis Look forward to your mail. __________________ ampslab

 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 Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Aussie Amplifiers         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post Apogee Pass Labs 195 23rd July 2008 08:07 PM xdissent Solid State 13 18th June 2004 02:44 AM kheldar Chip Amps 8 30th January 2004 02:50 PM tpenguin Solid State 3 23rd December 2003 09:47 PM BrianGT Pass Labs 3 19th September 2002 07:55 PM

 New To Site? Need Help?

All times are GMT. The time now is 07:34 PM.