rishi.iitk Posted October 17, 2006 Report Share Posted October 17, 2006 hey i have built a 12V to 4.5V dc voltage converter for my Discman to be use in my car.i have used there a 5.1V regulatorof TO3 package.and it works fine but during working it is getting hot.so wat to be use as heat sink for that. Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 17, 2006 Report Share Posted October 17, 2006 In my part of the world, a 7805 regulator is in a TO-220 package and many heatsinks are available for them. A TO-3 package is used for very high power and large heatsinks are available, few small ones. Quote Link to comment Share on other sites More sharing options...
rishi.iitk Posted October 17, 2006 Author Report Share Posted October 17, 2006 actually i can use 7805 of TO-220 package but i need high load current about 700mA.so i used TO-3 package Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 17, 2006 Report Share Posted October 17, 2006 12V - 5V= 7V. 7V x 700mA= 4.9W. A fairly small heatsink is needed with a TO-220 package for only 4.9W. When the car is running then its votage could be 14.4V. Then the regulator will dissipate 6.6W. The heatsink can be much smaller if you don't use an insulator. Then insulate the heatsink from ground.Use the TO-3 regulator if you can find a heatsink small enough. Quote Link to comment Share on other sites More sharing options...
ante Posted October 18, 2006 Report Share Posted October 18, 2006 The LM7805 has its tab connected to ground so cooling it can be done by bolting it to the car chassis as it then also will be connected to negative. (Not applicable on some older British cars though!) ;D Quote Link to comment Share on other sites More sharing options...
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