Electrical – Amplify current from a 4-20 mA temperature controller to drive a Peltier module


I have a temperature controller (Chino DB1000) which has a PID output of 4-20 mA. With this, I want to control the current going to a Peltier thermoelectric module (15V, 6A).

I am doing this via an ON-OFF circuit with a DC solid state relay, a 15 VDC power supply, and a temperature controller for SSR. But I don't want to keep doing this since the ON-OFF is not good for the thermal control or for the Peltier itself.

Is there any simple circuit to convert the 4-20 mA from controller to a regulated current to the Peltier? The 4-20 mA are not the sensor signal, but the processed PID control signal from the controller

After searching similar questions, I think that the answer might be towards PWM or MOSFETs.

Thanks a lot!

Best Answer

When you PWM a peltier you run an already relatively low-efficiency device at an even lower efficiency. The heat pumped across the peltier is \$\propto I_p\$, while the losses due to joule heating are \$ \propto I_p^2\$, namely (\$ I^2R\$).

If you don't need to run your peltier at its peak efficiency for your application PWM is a much simpler approach.

You will have to decide if you wish to have a bi-polar output, namely source/sink current or uni-polar where it just sources current in one direction proportional to your 4-20 mA control signal.

A 4-quadrant programmable power supply like some of the Kepcos is one approach.

An LED constant current driver with a dimming input would be a lower cost approach.

Of course you can design a full custom amplifier with a bipolar output stage, or run the peltier as a bridge-tied-load.


If you go the pwm route, a sample PWM modulator LTC6992 simulates directly in LTSpice, and has a component configuration to make life easy.