Heat Sink Design for Power Supply

Its not a word can be made clearly. At first you would know the transistor's joint max tempereature Tt. and know the shell of the unit themo-resistance Rs 3] the heat sinker themo resistance Rh; 4]touch themo resistance Rt; 5]circumstances temperature Tc; Then you can use formula Pw=[Tt-Tc][Rh+Rc+Rs] The result is the allowance power of the unit (transistor herein) In the switch power, 120w is power beared by a middle low power transistor or mosfet t If you need the power supply pls contact me at info@ndt.cn

Google "calculate and design the heatsink in the electronics power supply". There are lots of good tutorials out there.