Current Sensing

Issue & Solution

Current Detection for Inverter & Servo

Issue ...

Making an Ultra-compact High Efficiency Motor

High precision current detection is essential when there is limited board real estate when constructing integrated drivers/controllers for vector control of motors in factory automation.

What is the best current sensor when board space is limited?

Motor manufacturers, many that are AKM's customers, are faced with the persistent challenge to downsize the board in each successive generation. Miniaturization of the cored current sensor cannot be achieved due to the required size of the core. There is also the issue with heat generation from circuits with shunt resistors and photo-couplers.

Then what is our solution…

Coreless current sensor suppresses heat generation

Low primary conductor resistance and low heat generation

Downsizing the board while maintaining high accuracy

Coreless current sensors from AKM provide excellent overall accuracy with response characteristics and S/N ratios comparable to III-IV compound semiconductor materials used in closed type current sensors.

We are able to replace traditional shunt resistor + photo-coupler units due to the isolation space between primary and secondary. Primary conductor resistance is small, which suppresses heat generation which help downsize the PCB board significantly.

Current Detection for Inverter and Servo

Core-less Current Sensor

A core-less current sensor has been developed based on AKM's experience of over thirty years in magnetic sensor. It is housed in an ultra small package with dielectric strength, ideal for drive current detection up to 35A for motors and power conditioners.

Smaller and Less Heat than Shunt Resistor Circuit

A current detection solution with a shunt resistor needs insulation between the primary side and the secondary side by using an insulating element such as optocoupler that is large and expensive. Current flows in the shunt resistor also generates heat.

AKM's small magnetic current sensor can shrink the board size since the output signal can be transmitted to an A/D converter directly. It reduces heat generation in current detection since it does not use a resistor.

Current Detection with Shunt Resistor
Board size can be smaller since the heat generation is suppressed by a magnetic current sensor

Digital Output Module for Current Sensor

A digital output reference module of current sensor, that is suitable for AC Servos, Robots and General Inverters, is available.


'CQ' series are open-type current sensors which have the world's smallest package(*1), high accuracy, high S/N ratio, and the world's fastest response time(*2). With these advantages, we will offer the best current sensing solution to wide-ranging applications, such as inverter control, overcurrent detection, and electrical power detection.

*1 AKM's own investigation, among the current sensors with core in the world

*2 AKM's own investigation, among the open-type current sensors in the world

* Currentier is a trademark of Asahi Kasei Microdevices Corporation (under registration review).