Coreless current sensor for power inverters

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By Nick Flaherty

Allegro Microsystems uses differential Hall-elements in the AC37612 current sensor to measure the magnetic field provide high immunity to stray magnetic fields without the need of a laminated shield required by competing solutions, which reduces the design size and bill of materials (BOM).

This makes the coeless current sensor suitable for electric vehicle applications such as high-voltage traction inverter phase current measurement, 48V starter generators and battery disconnect.

“It is the first solution that provides a truly coreless method of accurately measuring hundreds of amps in a very small form factor, solving a key challenge for automotive engineers,” said Georges El Bacha, Product Line Manager at Allegro.

During acceleration, hundreds of amps flow through the traction motor inverter of an electric vehicle. A precise measurement of such high currents is vital for safe performance. Engineers have traditionally relied on a low hysteresis, laminated core for such measurements — using three to six cores, depending on the number of phases in the motor.

Eliminating these cores with the ACS37612 allows manufactures to reduce the space and weight of the inverters, thus increasing the efficiency of the electric vehicle. This non-invasive, contactless current sensor is designed to improve thermal efficiency relative to shunt solutions and is therefore ideal for reducing system energy consumption in 48V e-motor platforms.

The ability of the ACS37612 to be used in either busbar or PCB designs provides engineers with mechanical flexibility and simplifies their system level solution. The system coupling factor is determined by the sensitivity level of the ACS37612, as well as the shape and location of the busbar, making it easy to increase the current sensing range at any phase of the design.

The sensor is available in a TSSOP8 package (LU-8) that has a 3mm x 6.4mm total PCB footprint. Together with the coreless design, the ACS37612 enables a very small and light current sensing solution.



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