Temperature monitoring of components is a vital function to help ensure the reliability and efficiency of power electronics. Magnetic components, like inductors and transformers, are prone to internal temperatures that can degrade performance and, in extreme cases, cause thermal runaway. Traditional methods that use thermocouples and NTC thermistors often miss critical hotspot temperatures. That’s because these devices are surface-mounted, and any induced eddy currents in the sensor can lead to inaccuracies.

A breakthrough presented at the 2023 IEEE ECCE conference by David Menzi and colleagues from ETH Zurich introduced a new way to monitor temperatures in magnetic components. Their Core-as-a-Sensor¹ method leverages the temperature-dependent resistivity of ferrite materials in magnetic components to provide more accurate core temperature measurements.

A New Approach to Temperature Sensing

Ferrite materials used in high-frequency magnetics have a semiconductor-like property, which means their electrical resistance decreases as temperature increases. By measuring this resistance, the Core-as-a-Sensor approach can more accurately estimate internal core temperature, which is often higher than surface temperatures captured by traditional sensors.

The method was tested with a Bourns® 10 μH Shielded Power Inductor (Model PQ2614BLA-100K). Bourns’ test results showed that this approach outperforms traditional sensors, especially under thermal stress, providing more precise data. Importantly, the resistance-based temperature measurement remained stable despite nominal operating conditions like DC and high-frequency AC magnetic fields.

Bourns applied the Core-as-a-Sensor method in a 1.6 kW DC-DC converter, where it showed core temperatures consistently more than 10°C higher than those from traditional sensors. This makes it a game-changer, offering a more accurate picture of thermal conditions inside magnetic components.

For power electronics, this advancement is truly a breakthrough in helping to create more efficient, longer-lasting products. Designers are invited to read the related Design Note Bourns engineers created that provides more detailed information, and how this method provides additional application advantages while also paving the way for smarter, self-monitoring magnetic components. And, more information about Bourns® high current shielded power inductors is available on the website:  https://bourns.com/products/magnetic-products/power-inductors-smd-high-current-shielded.

¹D. Menzi, G. Eðvaldsson, J. E. Huber and J. W. Kolar, “Core-as-a-Sensor: Ferrite DC-Resistance-Based Core Temperature Measurement of Magnetics,” 2023 IEEE Energy Conversion Congress and Exposition (ECCE), Nashville, TN, USA, 2023, pp. 6532-6534, doi: 10.1109/ECCE53617.2023.10362938.