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Introduction to Fanless Power Supply for Harsh Environment



#Technical Article#AC-DC Power Supply#Medical#Industrial / ITE#Baseplate-cooling / Fanless

May 26, 2023




What is a harsh environment?

      A harsh environment generally refers to extreme temperatures, such as extremely hot or cold conditions, that can be challenging for humans to endure. In terms of power supply, a harsh environment can be defined as one where the power supply may be exposed to conditions such as heat, moisture, cosmic rays, and vibration. Thermal management is always a common challenge to the power supply in harsh environments.


Major cooling techniques for power supplies:

      There are three main techniques for cooling in power supplies:

      1. Natural convection:

      When a power supply is heated, the surrounding fluid (such as air) near the heated surface becomes warmer and less dense, causing it to rise. As it rises, cooler fluid from the surroundings replaces it, creating a natural circulation pattern.



      2. Forced air cooling:

      It is a method of heat transfer that relies on the use of mechanical devices, such as fans, to enhance the natural convection process and increase the rate of heat dissipation from a power supply.



      3. Conducted cooling:

      It is a method of heat transfer that happens through direct physical contact between two objects at different temperatures. Heat generated by components is transferred from the hotter object to the cooler object (metal case) through molecular interactions, without the involvement of fluid motion.




  Pros Cons
Natural convection Low/No noise
Simple design and construction
Low power density
Forced air cooling Low cost
Greater thermal dissipation capability
Excellent power density
Requirement of external fan
Higher maintenance cost
Noise and vibrations
Low life span and reliability
Conducted cooling High power density
Low/No noise
Suitable for harsh environment
Good thermal dissipation capability
High reliability
A little bit higher cost

      From the table above, it can be seen that conducted cooling would be the most cost-effective and reliable solution, making it ideal for use in harsh environments.


How can a fanless power supply be designed?

      Traditionally, industrial power supplies dissipate heat to on-board heatsinks or a U-channel chassis. The basic structure is shown below as Fig.1. However, the majority of the heat still remains in the power or system, which can have a significant impact on overall system reliability and over temperature protection.



Fig.1 Conventional open-frame power supply structure design


      The solution to this problem is to effectively transfer the heat source to the outside of the system. The heat generated by power supply mainly comes from critical components such as power devices, magnetics, and capacitors. By mounting these components directly onto a metal base (baseplate) and attaching them to the metal case of the system, heat can be successfully delivered to the outside. The following Fig.2 shows one of the examples and how the concept works.



Fig.2 Baseplate cooled power supply structure design


      The CFM500S series offers the similar baseplate cooling method, and users can add an extra metal plate with the size of 480mm * 248mm * 1.2mm under the baseplate of the CFM500S to enhance the heat dissipation performance. Please refer to the photos below for installation and more details are specified in the official application note.



      When used with the baseplate cooling solution, the CFM500S series can deliver 500W (full load) without a fan. The power derating curve is shown as below.




      Cincon's AC-DC fanless power solution, which includes baseplate-cooling open-frame, cover, and brick types, is suitable for a variety of systems. The power range starts from 70W to 750W. The baseplate cooling design makes all series in the fanless category achieve higher power density and improves heat dissipation performance under fanless condition and higher ambient temperature. If you are looking for a power supply with all of the aforementioned features, Cincon fanless power supply would be your ideal choice.


Check the product portfolio and contact for more support.


ITE/Industrial Fanless Power Supply:

Model Type Input Voltage Output Voltage Power
CFM130S Open frame 80~264Vac 12V, 18V, 19V, 24V,
36V, 48V
CFM150S Open frame 90~264Vac 12V, 24V, 28V,
36V, 48V
CFM202S Open frame 90~264Vac 12V, 24V, 28V, 36V,
48V, 56V
CFM260S Open frame 85~264Vac 12V, 24V, 36V, 48V 260W
CFM300S Open frame 90~264Vac
12V, 24V, 36V, 48V 300W
CFM400S Open frame 80~264Vac 12V, 18V, 24V, 36V,
48V, 54V
CFM500S Open frame 80~264Vac 12V, 18V, 24V, 36V,
CBM70S Half-brick 90~264Vac
12V, 24V, 36V, 48V 70W
CBM101S Full-brick 90~264Vac
12V, 24V, 28V, 36V,
CBM150S Full-brick 90~264Vac
12V, 24V, 28V, 36V,
48V, 54V
PDF700S Full-brick 90~264Vac 12V, 24V, 28V, 48V,
PFC750 Half-brick PFC module 90~264Vac 390V 750W


Medical Fanless Power Supply:

Model Type Input Voltage Output Voltage Power
CFM130M Open frame 80~264Vac 12V, 18V, 19V, 24V,
36V, 48V
CFM200M Open frame 90~264Vac 12V, 24V, 48V 200W
CFM300M Open frame 90~264Vac 12V, 24V, 36V, 48V, 300W
CFM500M Open frame 85~264Vac 12V, 18V, 24V, 36V,



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