Optimizing Thermistor Placement For Accurate Power-Plane Current Sensing

by Viktor Vogman, Power Conversion Consulting, Olympia, Wash., How2Power Today, Dec 18 2018

Focus:
When copper power planes or traces are used as current sensors for power monitoring, tolerances in the dimensions of the sensor (width and thickness) can be minimized with calibration. However, because copper trace and plane impedances are temperature dependent, such sensors also have thermal drifts that need to be considered. These drifts can be compensated through use a small surface-mount (SM) thermistor to sense the power plane temperature. However, in cases where the power plane has noticeable temperature variation across it, the question of where to place the sensor becomes important. This article describes a simple procedure to determine the optimum sensor location on the PCB, providing minimal temperature sensing error. Experimental results obtained with this method validate the theoretical prediction for the optimal sensor location.

What you’ll learn:

• How to accurately compensate the thermal drift of a power-plane current sensor using a surface- mount temperature sensor

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