Magnetic current sensors are replacing sense resistors and current transformers

Modern cars have become increasingly power hungry. Even the "least electrified" vehicles include advanced electronics for infotainment, safety, and engine control. Fully electric vehicles further add high-voltage power domains to charge and drive. Each of these systems shares the need for power monitoring and control, and this is where current sensors are used.

Safety systems and powertrain electrification OEMs are implementing electrified steering and braking systems to increase vehicle safety and enable automated driving. These systems encompass one or more high-current motors to actuate the steering rack or brake caliper. Safety systems require current sensors to be small and have low heat generation.

A basic electric vehicle powertrain encompasses a charging system and a drive system. A charging system may experience 100A at 400V or 800V, while the drive system may need to deliver several hundred amperes of current to the traction drives. Current sensors require isolation and high current capability, while also operating from DC to a high bandwidth for efficient power conversion and system protection.

Sense resistors and current transformers Current sensing needs have historically been met using sense resistors and current transformers. The sense resistor (and associated shunt amplifier) provides V=I×R but suffers due to large size, high power dissipation, slow bandwidth, and no inherent isolation. The current transformer provides an isolated, high- speed measurement, but has drawbacks of large component height, no DC sensing, a narrow frequency band, and needing many external components to operate.