High-Accuracy Current-Sensor IC Enhances Power Conversion

Allegro MicroSystems’ latest high-accuracy, Hall-effect current sensor targets fast, tightly regulated control loops in automotive and industrial high-voltage power-conversion systems.

The magnetic current sensor is specifically designed to perform high-precision current sensing, integrating high-voltage isolation to deliver a sensitivity error of only 0.55%. The ACS37017 runs with 750 kHz of bandwidth and 1-µs response times. Thus, it’s positioned for fast-switching topologies in high-voltage power converters, where rapid and accurate current sensing is critical to maintaining the stability of control loops in power supplies and their overall efficiency.

The chip joins the company’s portfolio of high-performance current-sensor ICs that aim to address the biggest design challenges in power electronics: high speed with the ACS37100, high power density with the ACS37200, and high accuracy with the ACS37017.

“Our philosophy is simple — we want to give engineers the right tool for the job,” said Matt Hein, head of the current sensor business at Allegro. “We don’t force a compromise.

The Criticality of Current Sensing in Power Supplies

Current sensors are vital to a power supply’s safe and efficient operation. They can deliver protection against short circuits and other transients; support real-time control, such as peak-current-mode or average-current-mode control loops; and enhance power management, as in safely and reliably charging and discharging high-voltage batteries.

By continuously and accurately measuring current flow, the power supply can run tight control loops that regulate output, improve efficiency, and prevent potential dangers.

Real-time current sensing enables the dynamic adjustment of power flow in solar inverters and renewable-energy systems, resulting in more efficient power conversion. In battery energy storage, monitoring and maintaining the correct balance of current opens the door to short-circuit overcurrent protection and prevents overheating or other faults that could shut down the system. Careful current measurement within EVs helps maintain optimal charging rates and ensure safe power distribution under the hood.

Moreover, in data centers, current sensors with high accuracy, low noise, and high speed ensure power is evenly distributed across power-converter stages, so that the maximum current reaches the processor before being lost as heat.

However, sensing current accurately in these situations can pose challenges to designers. Such systems tend to handle high power levels, and inaccurate current sensing can lead to inefficiencies and instability in the power supply. The challenge is compounded by the rise of gallium-nitride (GaN) and silicon-carbide (SiC) power devices that run at significantly higher frequencies than silicon, requiring faster current sensors to keep pace.

Under these conditions, even small measurement errors can translate to excess power losses and overheating.

Addressing the Drift in Conventional Current Sensors

Conventional current sensors tend to degrade or “drift” as temperatures change or as the device ages. Allegro said the ACS37017 delivers highly stable performance largely due to its proprietary compensation architecture. The technology maintains precise capture of current and precise signal conditioning, ensuring that control loops remain stable and efficient over the lifespan of the power supply or the entire system, according to the company.

The current-sensor IC also simplifies system architectures by integrating a stable, non-ratiometric voltage reference that eliminates the need for external precision voltage-reference components on the PCB. Allegro said that this not only reduces the cost of components and saves valuable space, but it also removes a source of system-level noise and error. This allows the current sensor to deliver a pristine signal directly to the MCU in the power supply.

It also features reinforced isolation, ensuring safety and reliability in high-voltage automotive and industrial systems. The surface-mount, leaded package brings robust isolation in a smaller form factor than existing current sensors.