drive peltier element

Question

Hi People... I`m working on a Project to create a Colling controled box using peltier elements..

The circuit above works as a voltage follower, dropping DC voltage on the peltier. Allthough its working, when i reach 5Vdc at the input The peltier cell(2 in parallel) only drives 5amps. Even when i increase the dc input tô 6 or 8 volts, mosfet is still delivering 5amps at Max(remember its 2 cell in parallel) . Why is that? I wish i could work at full power these cells...

Here it is a test I was able tô reach 8 degress celsius

Answer 1

OK so your max output on the op-amp is about 9V and the MOSFET needs 4V to turn on.... 9-4 = 5V. That sounds about right to me for what you are seeing.

Ditch the MOSFET and use a regular NPN transistor or Darlington. Since you are running it in linear mode anyway, the MOSFET does not buy you much other than low gate current.

Or better, change your circuit to use a P channel MOSFET like so.

^{simulate this circuit – Schematic created using CircuitLab}