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Constant current vs PWM efficiency -

[URL unfurl="true"]https://www.ti.com/lit/an/slua979a/slua979a.pdf[/URL]

Switch mode efficiency, interesting graphs in this Maxim solution -

[URL unfurl="true"]https://www.analog.com/media/en/technical-documentation/data-sheets/MAX1968-MAX1969.pdf[/URL]

[URL unfurl="true"]https://electronics.stackexchange.com/questions/28634/how-to-drive-a-peltier-element[/URL]

One could think, in terms of simplicity, using a power opamp to drive the peltier....with appropriate

interface to Arduino to close the loop. There are discussions online about stability of this approach,

if oscillation is evident. Note PWM approach lower cost overall I think, unless one uses standard

OpAmp and adds power transistors to handle current. Eg. power opamps are pricey. Example

circuit shown below.

[ATTACH=full]198303[/ATTACH]

This is rough example creating a power opamp out of a generic opamp Ignore input circuitry (Q1) and transformer load.

[ATTACH=full]198304[/ATTACH]

Insofar as the "sine" modulation, I wonder if thats just the consequences of the

PWM filtering prior student used and the rest of the control loop response

shaping......eg. filtering the pulse waveform .....