DC voltage regulator

[rishi.iitk]

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.

 

[audioguru2]

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.

 

[rishi.iitk]

actually i can use 7805 of TO-220 package but i need high load current about 700mA.so i used TO-3 package

 

[audioguru2]

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.

 

[ante1]

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