Investigation Into Static and Dynamic Performance of the Copper Trace Current Sense Method

This paper investigates the static and dynamic performanceof current sense methods, which exploit the resistivevoltage drop across the current carrying copper trace. This approachpromises very low cost since no dedicated shunt resistor isrequired, no additional power losses occur and no extra space onthe printed-circuit-board (PCB) is necessary. A microcontrollercan be used to calibrate the copper trace resistance and implementa temperature drift compensation by means of a temperaturesensor. Given that today almost every electronic device has atleast one microcontroller that can provide the small computationpower required for this current sensing technique, the additionalcost of such a technique is small.While the proposed technique appears straightforward, theoreticalmodeling and hardware experiments revealed two unexpectedobstacles. First, the thermal resistance between the busbar andthe temperature sensor notably alters correction for the temperaturedrift. We found that it is possible to rectify this behaviorby implementing a more sophisticated temperature compensationmethod inside the microcontroller. Second, it is demonstrated thatthe self-inductance of the busbar arrangement is not important forthe dynamic behavior (frequency response) of this measurementmethod, and the response is determined by the mutual inductancebetween main loop and sense loop. Based on simulation and measurements,we demonstrated that a simple RC-compensation networkcan significantly improve the frequency response.