High-current, low-impedance systems need advanced current sensing technology

The global demand for power supplies is expected to exceed USD 46.5 billion by 2031. This growth is fueled by the proliferation of EVs, renewable energy systems, and industrial automation, particularly for AC-DC power supplies.

These applications require current sensors with high accuracy, low noise, and fast response times. As the demand for higher power densities increases, so does the need for advanced current sensing technologies. These technologies enable real-time control and monitoring.

In this article, we explore the advantages of current monitoring. We also examine the drawbacks of traditional open-loop current sensors and the evolution of sensor technologies that address these challenges.

The need for real-time current monitoring

Accurate current monitoring and control in power supply systems help optimize performance. This ensures the longevity of energy storage systems, converters, and other system-critical components. In applications like UPS systems and energy storage, maintaining the correct balance of current flow prevents overheating, overcurrent conditions, and unexpected system shutdowns.

Additionally, in renewable energy systems where power generation may be intermittent, real-time current measurement enables the dynamic adjustment of power flow, resulting in greater efficiency. In EV charging stations, precise current measurement helps maintain optimal charging rates without an overload. In data centers, precise current monitoring helps ensure that power is distributed evenly across all devices, preventing hotspots and extending the lifespan of the equipment.

However, achieving accurate current measurement in high-current, low-impedance systems is not always straightforward. These systems often operate at very high power levels, and inaccuracies in current sensing can lead to inefficiencies, operational instability, and even safety hazards such as fire or electrical failure. This is why finding the ideal current sensing solution is so important.

Open-loop and closed-loop current sensor modules

Traditionally, open-loop current sensors have been used in power supply applications. These sensors measure current by indirectly detecting the magnetic field generated by the current flowing through a conductor. While this method is useful in some cases, it has significant drawbacks, particularly for high-current applications.

One of the primary issues is size. Open-loop sensor modules require large magnetic cores or external components to function effectively, leading to bulky designs that are why difficult to integrate into space-constrained applications.

Cost is another limiting factor, especially when high precision is required. The need for external components, such as compensation circuits, increases both the complexity and the total bill of materials (BOM) for the system.

Finally, the accuracy of open-loop current sensors is often insufficient for applications that require precise real-time monitoring.

An alternative approach is to use a closed-loop transducer. These include a compensation circuit that improves performance and accuracy compared to their open-loop predecessors, but they require additional components such as signal conditioning circuitry. Therefore, like open-loop current sensors, this makes them a more expensive and bulky option.

Analog sensors

Addressing these shortcomings, the integrated current sensor (ICS) has an enhanced performance through advanced integration technology. ICSs, such as those shown in Figure 1, combine analog sensing elements and signal conditioning circuitry into a single, compact package, thereby reducing size, cost, and complexity.

One key advantage of ICSs is their small footprint. By eliminating the need for large magnetic cores and external components, these sensors can fit into space-constrained systems. This makes them ideal for high-density power supplies, UPS systems, and energy storage applications. This compactness also simplifies the overall system design, reducing the number of components required and, therefore, the overall system cost.

ICSs also use advanced algorithms for temperature compensation and drift reduction, ensuring high-precision current measurements across a wide temperature range.

Additionally, these sensors offer higher bandwidth and faster response times than their traditional counterparts, allowing for real-time current monitoring and control in high-frequency switching applications. The improved system stability and more efficient power management make them a valuable component for energy-efficient designs.

By integrating multiple functions into a single package, as shown in Figure 2, these sensors reduce the need for additional compensation or signal processing circuits. This lowers the overall BOM and cost, as well as simplifying the manufacturing process.

Selecting the right ICS for power supplies

When choosing an integrated current sensor for low-impedance, high-current-capacity power supplies, the priorities go beyond basic measurement accuracy. Primary conductor resistance should be kept well below a milliohm to minimize power loss and heating in high-current systems. Values around 100 µΩ or lower are preferable. Continuous current ratings need to comfortably exceed the expected load. For many high-power designs, this means sensors that can sustain in the region of 200 A without derating.

In applications involving high voltages, the insulation system must be robust. Creepage distances should be in the range of 6.5 mm — ideally, a little more — and a tested isolation rating should be approximately 5 kV_rms. This ensures long-term reliability and safety compliance. The output stage should deliver a stable and predictable signal that remains unaffected by moderate supply fluctuations. This reduces the need for complex external voltage regulation and eases the analogue front-end design.

Precision over temperature is equally important. For demanding environments, sensors should have a total sensitivity error within ±1% across a broad temperature range, from at least −40^oC up to 120^oC, ideally 150^oC. This ensures that readings remain consistent in both outdoor installations and high-density enclosures.

When these characteristics are combined with a compact package and the integration of necessary signal-conditioning functions, the result is a current sensing solution that supports accurate, real-time monitoring without excessive footprint or bill-of-materials cost.