Joe McCauley wrote:
> Didn't know that Olin. I suppose you shouldn't PWM a peltier cooler
> then?

Right, at least not if the PWM pulses go directly to the Peltier cooler
without filtering.

The cooling effect of a Peltier device is directly proportional to current.
However, the effective cooling it performs externally is the amount it is
cooling minus the power you are dumping into it electrically.  At higher
currents the voltage drop accross the device will be higher.  Therefore as
current increases the cooling power increases linearly but the internal heat
generated goes up more than linearly.  This is why Peltier devices have a
maximum cooling current specification.  Increasing the current from there
adds more heat than the extra current can cool.

Efficiency monotonically decreases with increased current.  You therefore
want to run the Peltier device at the steady current to match the required
cooling power.


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