AC-DC power supply thermal management patent enables more efficient design-in

The new thermal strategy covered by the patent leads to power supplies that are flexible in their cooling requirements, keep audible noise to a minimum, and are easy for customers to integrate into their systems.

“Thermal management is one of the main technical challenges to overcome in the design of any system,” explains Martin Coates, Engineering Director, TDK-Lambda UK. “Very often, there are hot spots within systems that require a disproportionately high airflow over them to keep component temperatures within acceptable limits. This, in turn, often leads to excessive audible noise from fan cooling, and/or limitations in the system’s thermal performance.”

There are two established techniques for overcoming the thermal management challenge. One method is to increase unit dimensions to allow for better airflow. Driving up efficiency is another technique, thereby minimising internal heat dissipation. Increasing unit size is often unacceptable, as units are seen as uncompetitive and excessively large, making them difficult to integrate into systems. Also, as power supply efficiencies increase, the law of diminishing returns applies, and incremental improvements become excessively expensive. Above all, both techniques come with an increased bill-of-material cost.

The new thermal management strategy used in manufacturing the CUS400M series of AC-DC power supplies, covered by the patent, overcomes these issues by utilising existing system metalwork for cooling. Through careful PCB design and the use of thermally conductive plastics, the heat generated by the electronic components is spread and transferred into the system chassis. This means that good thermal performance can be achieved with substantially lower airflow, resulting in reduced audible noise from the slower fan.

Many medical and industrial applications require a peak output power for a few minutes but relatively low continuous quiescent output power. “The design methodology also means that the unit is more resilient to peak loading since the thermal time constant is substantially longer than traditional designs,” adds Coates. “This means that the internal component temperatures do not rise as rapidly for peak loading, decreasing the stress on the components and increasing the power supply lifetime. This enables us to offer the CUS400M series with a five-year warranty. In addition, the CUS400M can replace larger, more expensive convection cooled products that are rated continuously for the peak requirement, translating into a cost saving for the customer.”