Mosfet device selection for LED dimming.

Thread Starter


Joined Oct 31, 2017
Hello everyone,
I am thinking of developing a controller that can adjust the brightness of 12V, 50A, and 600W LED.

- Mosfet 1 Spec

Model : NTBLS0D7N06C
Datasheet :
Rds(on) : 0.75mΩ

- Mosfet 2 Spec

Model : IRFP1405PbF
Datasheet :
Rds(on) : 5.3mΩ

I made a prototyping board using Mosfet 2. (below)


I installed a heat sink, but the heat is worse than I thought, so I'm considering a bigger heat sink.

I learned that Rds(on) levels must be low to reduce fever.
I'm comparing and exploring the core element, Mosfet.
And I found a Mosfet that looked good. (Mosfet 1)

The power dissipation of Mosfet 1 is as follows.

I = 50A
R = 0.75mΩ
V = 37.5mV
W = 1.875W
The power dissipation of Mosfet 2 is as follows.

I = 50A
R = 5.3mΩ
V = 265mV
W = 13.25W
Calculating the power dissipation ratio of the two Mosfets is about 7 times.
Even if Rds(on) is increased due to the increase in the junction temperature, I think the dissipation can be reduced a lot compared to Mosfet 2.

I'm very happy now, but I can't believe it's so magical.
I'd like to ask everyone to confirm if what I understood is correct.