Thermoelectric modules and systems provide a solid state method to achieve programmable heating, cooling or temperature cycling by converting electrical power to heat pumping capability. In thermoelectric applications, the power supply, or electrical power source, provides a DC current (Amps) at a regulated output, or working voltage (VDC).
Power Adapters for Thermoelectric Coolers (TECS) are Key in TEC Based Temperature Control Systems
This must be sized and specified to match the thermoelectric cooler (TEC) with other components, or methods, that comprise the thermal system. These components or methods may include heat sinks, cold plates, forced air/fans, natural convection, seals, thermal coupling and any other engineered materials. The overall performance of the system is both enabled and constrained by the maximum power output (Watts) of the power supply. Thus, power supply, or power source, capability can make or break the performance of TEC based temperature control systems.
Key Power Source Specifications
Power supplies are complex multi-variable sub-systems. Power supply performance can adversely influence overall temperature control performance of TEC based temperature control systems. Considerable effort and attention to detail must be applied to match the power supply specifications to the specific needs of a given thermoelectric based application to ensure that the overall integration is safe, robust and fit for purpose. Some of the more important performance attributes of a power supply for a TEC module application include the following.
- AC Input Voltage Range
The AC Input Voltage Range only applies to standalone TEC based systems such as Point of Sale (POS) Beverage Coolers. The geography of the installation often dictates the AC input voltage range. For example, the typical electrical output voltage in the USA, Canada and Puerto Rico is 120VAC, while Italy, France and Germany operate from 230VAC. Given the proliferation of products targeted for international applications, universal power supplies with input ranges inclusive of 100-240VAC for both 50 and 60 Hz are commonly available.
- DC Output Power
The overall DC output power capability is captured in specifications for voltage accuracy, maximum current, voltage regulation, transient stability, ripple, noise, turn-on delay, rise time, hold-up time, temperature coefficient and maximum total power. The worst case performance in actual operation of the thermoelectric based temperature control application for all of these power supply attributes should be verified under actual operating conditions including temperature and humidity extremes.
The safety requirements for a power supply are application dependent. Compliance with the applicable regulatory standards for UL, CE and FCC is often required and provides assurance for safe operation for worst case internal and external fault conditions. Several geographies have requirements unique to their regions. Consultation with experts and notified regulatory bodies from the countries of interest will often be required to assure that the mandated safety requirements and government directives are being followed. The original equipment manufacturer (OEM) is responsible for assuring product safety.
Power supply protection schemes add fault tolerance and immunity to the overall thermoelectric system design for both internal and external fault conditions. Protection schemes may include over voltage, over current/overload, short circuit and over temperature protection. The protection scheme requirements may be integrated with the safety requirements for some applications. Laboratory testing to support regulatory certifications may include tests to challenge the robustness and effectiveness of the protection mechanisms.
Pay very close attention to power supply performance, both transient and steady state, when developing and testing thermoelectric based temperature control systems. A variation in current demand versus time, operating temperature and heat load is to be expected.
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