TE Technology TC-36-25-RS485 - Manual (Page 12)

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Pulse‐Width Modulated Power Output
The TC‐36‐25 RS485 requires a constant‐voltage power supply to provide power for a thermoelectric (TE) device such as a
TE cooling assembly or a Peltier (TE) module. The controller regulates the power to the TE device using a method called
pulse‐width modulation (PWM). With PWM, the power is rapidly switched “ON” and “OFF” at constant frequency (2700
Hz for this controller). This creates a square‐wave “pulse” of power to the thermoelectric device. The “ON” time, or pulse
width, can be varied to create an average output voltage (Vaverage) that is required by the TE device to maintain the set
temperature.
How Pulse‐Width Modulation Works
The important advantage to PWM is that it does not cause the extreme temperature excursions that are experienced with
a thermostatic control system. This helps to extend the life and reliability of the TE devices. Added benefits are that the
controller does not generate a large amount of waste heat and it does not require a large heat sink.