I am trying to control a 12V Peltier (6A maximum current, but I am unlikely to need to use anywhere near that) element with a 5V PWM supply (from an Arduino at the moment).
I am using a logic level MOSFET (IRLZ44N) to allow the 5V (low current) to control the 12V (high current) load. That seems to work ok and the MOSFET stays cool even without a heatsink.
One side of the Peltier is getting hot as expected. However, the other side is not getting very cold. I am given to understand that powering a Peltier element by PWM is not ideal, and a steady DC voltage would be much better.
My first thought is to use a low pass filter, however, I am having difficulty choosing the correct type and components to use.
As standard the Arduino produces PWM frequencies of 490Hz and 980Hz, although it can produce up to 65KHz with a bit of additional work.
Am I correct in thinking that a higher frequency would be better and make it easier for a low pass filter to smooth out the pulses? As long as the MOSFET can handle the higher frequency (I believe the IRLZ44N is for switching below 100kHz).
I have been told an inductive low pass filter would be best for this application, but I don't know how to choose the values for the resistor or inductor. I know they are dependant upon my desired cut-off frequency, but I don't understand how I should be determining that. I'd assume that I'd want as low a cut-off frequency as possible for a steady DC voltage? 1Hz? And then, I would also assume that I want a high value resistor, but that results in needing a huge inductor (several Henrys).
Please can someone tell me how I should be choosing these variables? Or should I be approaching this from a different direction entirely?
I have considered just turning the Peltier fully on/off for set time intervals but that doesn't provide a stable temperature and there is suggestion that it even damages the Peltier element.