Technical Article

Exploring the Electrification Shift: Current Sensing Technologies Adapt to New Challenges

March 07, 2024 by Bodo Arlt

As electrification trends evolve, so must current sensing technology.

This article is published by EEPower as part of an exclusive digital content partnership with Bodo’s Power Systems.


LEM recently announced a collaboration with TDK on next-generation tunnel magneto-resistance-based (TMR) integrated current sensors (ICSes) for electrification applications, recognizing the rapid growth in demand for current sensing technologies, which requires high volumes and cost-effective products. Bodo spoke with Thomas Hargé, LEM’s vice president of global product management, about shifting industry trends and how this partnership adds value to customers.


Bodo: How have electrification trends impacted the current sensing market and technologies?

Hargé: Global decarbonization is a major factor, with countries embarking on what is nothing less than an electrification revolution. We are heading inexorably toward an electrified planet, which is impacting a wide range of markets.


Thomas Hargé. Image used courtesy of Bodo’s Power Systems [PDF]


Of course, one of the biggest areas is the electrification of passenger vehicles. Transportation has been a massive contributor to excessive CO2 emissions, and the automotive sector is predicted to represent half of the current sensor market within the next five years. That’s a game changer in terms of the technological advances that need to be developed within a very short timeframe.


Bodo: How has LEM adapted its products or strategies to align with the electrification trend?

Hargé: Since the very beginning of power electronics, LEM has been developing current sensing technologies for the rail, automotive, and industrial sectors. The company works closely with customers and within key markets, optimizing existing technologies and co-designing solutions with end users.


Image used courtesy of Adobe Stock


For at least the past decade, LEM has developed application-specific current sensors for electric vehicles (EVs) and hybrid electric vehicles (HEVs). As the market has accelerated, LEM has focused on working with customers to improve the integration of these sensors within inverters, onboard chargers (OBCs)—which convert AC to DC to charge a vehicle’s battery pack—and battery management systems.


Bodo: What are the technical requirements for current sensing in various applications, and what trends are emerging?

Hargé: Size is always a factor due to the limited space within an electric vehicle. Also, all components need to be of minimal size to make a vehicle as light as possible to minimize energy usage and extend the distances cars can drive between charges.

Improved integration within customer systems can lead to breakthrough semiconductor solutions. That’s why LEM invests substantially in semiconductor development capabilities to create integrated current sensors. These are essentially a ‘current sensor on a chip,’ enabling users to build smaller systems.

Smaller power conversion systems can also be developed using silicon carbide (SiC) or gallium nitride (GaN). These new transistors can switch faster and allow users to reduce the size of the magnetic components (i.e., chokes). Consequently, current sensors need to be much faster and smarter than previously required while making it possible to measure higher-frequency currents.

Again, integration is the key to compact designs, so the current sensing function is getting smaller and smaller. There is also more and more integration of software to simplify operations, provide additional features, and minimize the amount of hardware in an EV.

Last but equally important is the fact that several automotive applications require a ‘safe’ current measurement. That’s why LEM has developed ISO26262-compliant sensors with safety levels that include quality management and Automotive Safety Integrity Level (ASIL) C.


Bodo: How do you stay ahead of evolving technical demands across different applications?

Hargé: Working with key customers and co-developing innovative solutions is vital to staying ahead in the market and satisfying demand. As mentioned earlier, LEM’s investment in semiconductor technology has enabled the company to accelerate the miniaturization of its sensors.

By investing in new sensing technologies such as TMR through its collaboration with TDK, LEM can develop faster, more accurate, lower-power sensors. At the same time, LEM has significantly invested in software capabilities to make the systems it develops smarter than their predecessors. Examples of such investment include a purpose-built R&D center in Lyon, France, and setting up a dedicated team in Bulgaria.


Bodo: What is your assessment of today’s landscape in the current sensing market?

Hargé: Over recent years, we have seen how the growth in the automotive market through increased electrification has attracted several companies from the semiconductor industry who are expanding their input in the sector. There has also been some growth in the number of classical automotive tier 2 producers (i.e., component manufacturers who supply the OEM automakers) providing some solutions.


Bodo: What strategies allow you to stay competitive and adapt to changing market dynamics?

Hargé: Besides the efforts on the technology side described above, LEM is the only player in the sector focusing solely on current sensors. That has resulted in the company having the broadest portfolio of current sensors today, which means it has been able to pick the right technology for every new challenge. TMR is another technology that will expand this portfolio of solutions. Furthermore, LEM has accumulated a tremendous level of know-how in the area of current measurement. This has played a key role in enabling LEM’s engineers to develop accurate and reliable sensors in customers’ applications.


Bodo: How does LEM use integrated current sensors to solve the challenges of ‘smaller, smarter, cheaper’ devices?

Hargé: LEM considers ICSes to be the natural evolution of current sensors. In fact, integrated sensors are actually just smaller versions of their predecessors. Something often misunderstood is that all the challenges involved in measuring current are amplified through miniaturization. This means it is absolutely critical for players operating in this sector to have a deep understanding and experience on critical parameters such as di/dt, dV/dt, and partial discharges, to name a few.


Bodo: Can you provide examples of how ICS technology addresses specific challenges in the market?

Hargé: One of the biggest attributes of ICSes is their size. For example, a typical application where a traditional LEM sensor would be too big would be in electric bikes. Thanks to ICS technology, 8-SOIC (3.90 mm wide) sensors such as GO 20 SME Hall effect current transducers are now small enough to fit into an e-bike motor while delivering precise torque control. The extremely low profile sensors feature galvanic separation between the primary and secondary circuits, an insulated test voltage of 2500V RMS, and low power consumption. They also have high immunity to external interference, superior insulation capability, no magnetic hysteresis, and low electrical resistance (0.9 mΩ).


Bodo: Within its integrated circuit sensor range, how does LEM’s use of TMR technology specifically address application challenges?

Hargé: Most ICSes today use Hall elements to sense the magnetic field generated by the current to be measured. After spending many years improving Hall sensors, LEM had reached a point where making one parameter better (such as speed) meant compromising on others (including accuracy and power consumption). The beauty of TMR is that it delivers all three—better speed and accuracy and lower power consumption—all at the same time. The compromises have been removed and will go a long way towards meeting the challenges of specific applications.


Bodo: What applications benefit the most from TMR technology, and why?

Hargé: Onboard chargers in EVs will be the first application to benefit from TMR technology because they require very fast current measurement. Second in line will be solar inverters, with integrated current sensors providing an excellent offset drift over temperature, which is essential on the AC side.


Bodo: How does the TDK partnership enhance LEM’s ability to deliver solutions to the market?

Hargé: TDK has developed a very deep know-how in TMR technology over time. The combination of the company’s TMR knowledge and LEM’s experience in ICS development will make it possible to set a new standard in ICS performance for OBCs, solar inverters, and other applications such as autonomous mobility. LEM selected TDK as a partner based on its best-in-class technology performance as well as reliable supply, automotive quality, and process maturity. The collaboration has been created to produce a TMR-based sensor that is faster, more accurate, and with lower noise than existing solutions.


Bodo: How does the collaboration contribute to time-to-market and the reliability/quality of LEM’s solutions?

Hargé: It takes many years to develop a good TMR and a top-quality ICS. By joining forces, the two companies will use their existing technologies to shorten significantly the time it would have taken for either of them to bring a top-class, game-changing product to the market. TDK develops TMR dies for LEM, incorporating them into integrated current sensors for the sectors mentioned earlier. The current sensor market requires high volumes and cost-effective products, and this collaboration will deliver those.


This article originally appeared in Bodo’s Power Systems [PDF] magazine.