Sizing MOSFET Heat Sink
12 volt solid state relay. Parallel MOSFETS opto coupler driver. MOSFETS are 100 ampere 3 milliohm 50 volt. TO220 case. Ham Operators.... Any ideas for proper heat sink selection? Individual ...
Forum Discussion
Here's how to calculate heatsink.
1. Get specs from MOSFET. For example:
http://www.onsemi.com/pub_link/Collateral/EN9050-D.PDF
R_DS_on = 4.5 mohm @ 50A & 100C
Max power at 50A is: P_max = 4.5 mohm * 50A = 2.25 W
50A is a reasonable assumption.
2. Calculate heatsink spec:
The goal is to keep fet under 80 C. Assume max ambient temp is 35C.
Max fet & heatsink temperature rise is 80 - 35 = 45 C
The heatsink must be less than
Theta = 45C/2.25W = 20 C/W
You can use this:
http://www.aavid.com/products/standard/507222b00000g
It has 9.6 C/W
All you need is one fet. No isolation is needed. Drive the fet with 10V, not 5V.
1. Get specs from MOSFET. For example:
http://www.onsemi.com/pub_link/Collateral/EN9050-D.PDF
R_DS_on = 4.5 mohm @ 50A & 100C
Max power at 50A is: P_max = 4.5 mohm * 50A = 2.25 W
50A is a reasonable assumption.
2. Calculate heatsink spec:
The goal is to keep fet under 80 C. Assume max ambient temp is 35C.
Max fet & heatsink temperature rise is 80 - 35 = 45 C
The heatsink must be less than
Theta = 45C/2.25W = 20 C/W
You can use this:
http://www.aavid.com/products/standard/507222b00000g
It has 9.6 C/W
All you need is one fet. No isolation is needed. Drive the fet with 10V, not 5V.
MEXICOWANDERER wrote:
MOSFETS are 100 ampere 3 milliohm 50 volt. TO220 case.
