Electrification has created a new paradigm in automotive power systems; whether the design is a hybrid electric vehicle (HEV) or fully electric vehicle (EV), there are new design challenges to address. This technical article highlights some of the primary challenges in high-voltage current sensing and shares additional resources to aid and simplify your design process.

For an introduction to current sensing, see our e-book, “Simplifying current sensing.”

High voltage, high current (>200 A or, more commonly, 1,000 A)

High voltage (≥400 V) fully electric systems aim to lower the current consumption for the traction system that moves the vehicle. This requires isolating the solution so that the “hot,” high-voltage side can provide current measurement to the “cold” side (attached to low-voltage ≤5-V microcontrollers or other circuitry). The high current presents an issue when trying to measure with a shunt resistor due to the I2R power dissipation.

To use a shunt in these conditions means that you must select a sub-100-µΩ shunt resistor, but these resistors tend to be larger and costlier than more common milliohm resistors. One alternative is to use magnetic-based solutions, but these are less accurate and have higher temperature drift than shunt-based solutions. Overcoming these performance drawbacks will dramatically increase the cost and complexity of a magnetic solution as well.