This page explains what a coreless current sensor IC is with its principles and features. With understanding of its principles and features, you can understand more deeply about how to use and its advantages.
(Currentier, which is the brand name of AKM's coreless current sensor IC, has its unique features and it is featured on the link "Currentier is...".)Get more news about Current sensor core,you can vist our website!
A current sensor is the device that generates a signal proportional to the amount of current using the output of a magnetic sensor that detects the current flowing through the board and wiring. A Coreless current sensor is one of the current sensor types, without a magnetic core. Other current detecting methods, such as a cored current sensor, are explained in more detail in the link "Types and Characteristics of Current Sensors".
Coreless current sensor IC has a very simple configuration; magnetic sensor detects the magnetic field generated by the measured current flowing through the primary conductor, and ASIC corrects and amplifies signals from magnetic sensors. In the later of this page, we would like to explain about the role of these three components in more details.
The primary conductor is involved in the generation of a magnetic field. The primary conductor is the path of measurement current and has a role of magnetic field generator. The measurement current flows into the primary conductor from the printed circuit board and generates a magnetic field B around the primary conductor in proportion to the current amount. The primary conductor is made of the package lead frame as it is.
Shunt resistor + isolation amplifier / isolation ADC is another main current sensing method which is commonly used, but this method has a disadvantage that thermal design is difficult. This is because this method is based on I to V conversion, and the resistance R needs to be large enough to ensure the output voltage V.
In contrast, as for coreless current sensor IC, the primary conductor is just the path of the measured current, and the resistance R can be sufficiently small because the primary conductor only needs to create a magnetic field. Coreless current sensor IC with a small resistance value R generates less heat because the power P is proportional to the resistance R. As a result of low-heat generation, the system downsizing ( reducing size of substrate and equipment ) can be achieved.
Coreless current sensor ICs have another advantage that it's easy to ensure insulation. Figure 2 shows the schematic of general coreless current sensor's package (See through view / Cross sectional view).
Inside the package of a general coreless current sensor IC, an insulation film is placed on the primary conductor and the ASIC is placed on top of it. And outside the package, the specified insulation performance is achieved by allocating the creepage and clearance distance between the the primary conductor and the secondary terminal.
A magnetic sensor has its role to measure magnetic field which is generated from the primary conductor. Hall elements are mainly used as magnetic sensors, which use hall effect and output a voltage proportional to the magnetic fields. The magnetic field generated by the flowing current through the primary conductor is proportional to the current. Therefore, the output of the hall element and the flowing current through the primary conductor is also proportional.
The hall element reacts to magnetic field and is not connected, so that it can ensure insulation between the primary conductor ( high voltage side ) and the output of the current sensor.
General coreless current sensor ICs ensure insulation by insulation film, as explained in 2-2. There are two types of hall element, Si hall element and compound semiconductor hall element. Other than AKM, hall element is put inside ASIC and is made of Si. The hall effect depends on the electron mobility of the hall element material, and Si is about 1450 ( cm2/Vs ). This value is considerably smaller than the electron mobility of InAs ( Currentirer uses InAs ), which is about 1/24 of that of Si hall element, and this causes a problem in terms of resolution (Table 1).