How to choose the right current sensing technology for your high voltage system?

“From self-driving cars to airplanes to factory floors, advances in electrification and automation are rapidly changing our world. Previously manual, mechanical or hybrid systems are moving towards full automation and electrification due to improved performance and reliability, as well as reduced total lifetime cost. In fact, we are in the fourth industrial revolution focused on automation and intelligent monitoring, also known as the era of Industry 4.0. As the electrification revolution is in full swing, the role of high-voltage systems in achieving greater efficiency and performance is becoming increasingly prominent.

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From self-driving cars to airplanes to factory floors, advances in electrification and automation are rapidly changing our world. Previously manual, mechanical or hybrid systems are moving towards full automation and electrification due to improved performance and reliability, as well as reduced total lifetime cost. In fact, we are in the fourth industrial revolution focused on automation and intelligent monitoring, also known as the era of Industry 4.0. As the electrification revolution is in full swing, the role of high-voltage systems in achieving greater efficiency and performance is becoming increasingly prominent.

In high-voltage systems, signal and power isolation helps protect personnel and critical circuits from high-voltage AC or DC power supplies and loads. Efforts are currently underway to further reduce the size of these systems as more electrical functions are integrated into the system. How to reduce the system cost and design complexity while reducing the size and maintain the high performance of the system is a new challenge for engineers.

Current sensing is commonly used for overcurrent protection, monitoring and diagnostics, and closed-loop control in high-voltage systems. Current sensing often requires high-accuracy load monitoring and control to maximize efficiency. For example, power factor correction circuits need to accurately sense AC current to improve system efficiency and monitor energy consumption. High voltage motors also require accurate motor phase current sensing for precise motor torque control. Since the characteristics of each system will have many different requirements, this article will focus on how to choose the right current sensing technique for your high voltage application.

The three main options for measuring current in high-voltage applications are to use shunt-based isolation amplifiers, closed-loop Hall-effect current sensors, or open-loop Hall-effect current sensors.

As shown in Table 1, isolated current sensors and closed-loop Hall-effect current sensors have higher accuracy and isolation, but they are more expensive and bulkier than open-loop Hall-effect current sensors. So, if high accuracy is your primary concern, either of these two approaches will suit your needs.

If size and cost are critical to your design, an open-loop Hall-effect current sensor may be the answer. As described in Table 1, they enable high-voltage isolated measurements in a simple, small form factor and require no external components, but traditional open-loop Hall current sensors drift significantly over time and temperature, which limits their usefulness precision.

TI’s newest TMCS1100 zero-drift Hall-effect current sensor solves this problem — TI’s first open-loop Hall-effect current sensor that offers a good balance of accuracy, size, and cost. Its zero-drift architecture, real-time sensitivity compensation, and reliable 3-kV isolation provide consistent, accurate measurements over time and temperature in high-voltage systems.

	Shunt-Based Isolated Current Sensor	Closed Loop Hall Effect Current Sensor	Open Loop Hall Effect Current Sensor
			existing equipment	TMCS1100
Solution size	C	CC	+ +	+ +
Required External Components	1 – 3	2 – 5	0	0
Solution cost	C	CC	+ +	+ +
precision	+ +	+ +	C	+
Offset and Sensitivity Drift	+ +	+ + +	CC	+
Isolation life	+ +	+ +	C	+

Table 1: Comparison of Isolated Current Sensing Test Solutions

The TMCS1100 provides less than 1% total error current measurement, and its zero-drift, high-accuracy signal chain structure improves device temperature drift and eliminates the need for additional multi-point calibration. In addition, this accuracy makes the system more efficient, enabling more precise control while reducing the design complexity that requires high-accuracy isolated current measurements, as shown in Figure 2. In addition, the TMCS1100 provides 600-V basic operating isolation and 3-kV dielectric isolation between the current path and the circuit.

Figure 2: The TMCS1100 enables consistent, accurate measurement of time and temperature.

You can learn more about the benefits of this magnetic-based current-sensing approach, including higher accuracy, lower drift, and reliable 3-kV isolation.