Kemite
December 05, 2019
Blog
When selecting the best components for a given application, it can be said that capacitors receive more attention than other passive component types.
When selecting the best components for a given application, it can be said that capacitors receive more attention than other passive component types. However, where there is a capacitor, there is usually an inductor, because the electrical system usually needs to use the electrostatic characteristics of the capacitor and the electromagnetic characteristics of the inductor to work properly.
Now, the latest developments in ferrite cores and metal composite inductors provide designers with more choices and more power to optimize the performance, reliability and cost of their circuits.
In its most basic form, an inductor can be as simple as a wire coil. By forming wires around the magnetic core, the inductance can be multiplied. The material characteristics of the magnetic core have a great influence on the inductance, and the shape can also be designed to optimize the characteristics of the inductance.
When a voltage is applied across the inductor, the current rises at a rate that depends on the voltage and inductance value. The 1V potential on the 1-Henry (1H) inductor causes the current to increase at a rate of 1A per second. formula:
Inductors have important characteristics that engineers can use to manage energy and manipulate signals. The main characteristics of inductors include:
Utilizing these characteristics, inductors are often used in analog filter circuits and used to manage the energy flow in switch-mode power conversion applications.
When circuit designers try to pack more functions into smaller and smaller spaces or increase power density, inductors are required to provide high inductance values in smaller component sizes. At the same time, in order to avoid power loss and efficiency reduction, unnecessary parasitic effects such as DC resistance (DCR) must be minimized, and the parameters should remain relatively stable over temperature changes and the entire operating current range. Improved core material performance enables inductor manufacturers to meet these requirements.
As with any engineering challenge, optimizing the performance of core materials involves trade-offs, which improve performance in some areas, but trade-offs in others. Despite the development of new core material technologies, such as sintered metal powder cores, traditional ferrite cores continue to provide attractive benefits. As manufacturers find new ways to optimize device characteristics and more stringently control parameters through finer manufacturing tolerances, ferrite core inductors are constantly evolving and improving.
Currently, two main conventional ferrite material formulations are usually used: nickel zinc (Ni-Zn) and manganese zinc (Mn-Zn). Ni-Zn ferrites tend to have better core resistance, while other component parameters (including saturation characteristics with respect to size, thermal performance and inductance) are less favorable. On the other hand, Mn-Zn magnetic core allows high inductance and high efficiency per volume, while saturation characteristics, thermal performance and core resistance are not so strong.
In order to significantly reduce the DCR and core losses associated with Mn-Zn ferrite inductors, KEMET has created a new type of inductor called assembled ferrite. As shown in Figure 1, they consist of a two-part core and a flat wire direct terminal conductor. These devices combine the high inductance and high efficiency advantages of Mn-Zn inductors with low DCR and low iron loss.
This structure makes the vertical inductor appear, such as
Narrow to 6.0mm. It is 2.0mm smaller than traditional inductors and can save a lot of space in high-power applications, such as the DC optimization of CPU point-of-load (POL) converters, which require multiple inductors in the area between the POL and CPU pins. Although the space becomes extremely limited near the device, it is still desirable to place the inductor close to the pin to minimize DC line losses. In the same PCB area, four narrow TPI inductors can replace three conventional inductors.
On the other hand, a new type of metal composite core material has been developed, whose saturation and thermal performance are better than ferrite devices. The magnetic core of the metal composite inductor is composed of iron powder, which is mixed with a binder and pressed into a core shape.
In addition, the high magnetic permeability of the core material reduces the DCR of the inductor, so the self-heating when working under high current is reduced. This can not only improve system efficiency, but also reduce dependence on thermal management components such as heat sinks (Table 1).
Material type
Ferrite inductor
Metal inductor
Nickel zinc
Manganese
Iron base
inductance
fair
well
not good
Magnetic saturation
Thermal properties
effectiveness
Core resistance
When comparing the inductance and saturation characteristics of Mn-Zn ferrite and metal composite inductors, Mn-Zn ferrite shows a higher nominal inductance value. This is usually stable under current, and once the saturation current is reached, the inductance drops sharply. At higher temperatures, the saturation current will also decrease significantly. Although metal composite inductors show a lower nominal inductance relative to the component size, they have more gradual saturation characteristics and exhibit higher temperature stability (Figure 2).
KEMET recently launched a new
It contains more than 100 devices, ranging from 0.10µH to 47.00µH, with DCR values as low as 1.5mΩ. The inductor can work in the temperature range of -55°C to +155°C, and the footprint is as small as 5.3mm x 5.00mm x 2.0mm, making it suitable for densely packed power applications, and can operate from minus zero to zero High-zero temperatures are deployed in challenging environments for industrial or automotive hoods.
In a typical established inductor structure, the coil is wound on the core, and the METCOM core is formed around the coil (Figure 3). This creates a non-conductive outer layer that acts as a shield to contain the magnetic flux in the inductor body. As a result, work efficiency is improved. EMI performance has also been improved, thereby minimizing interference to surrounding circuits.
METCOM inductors have excellent stability over a wide operating temperature range, which enables them to provide excellent performance in automotive applications where components in these applications can withstand high temperatures, such as under the hood or exposed to direct sunlight Inside the cabin.
On the other hand, where high inductance is required and space constraints are very strict, ferrite inductors (such as the TPI series) can provide space-saving solutions that meet important electrical performance requirements.
The arrival of direct-end assembled ferrite inductors and the development of metal composite inductors that benefit from excellent saturation and thermal characteristics and inherent EMI shielding advantages have blurred the traditional gap between inductor core technologies. Now, designers have more choices to deal with power conversion problems, from efficiency-centric, size-constrained computing and data center applications to size-constrained and temperature-sensitive applications in the automotive space.
Field application engineer for passive components. Industrial, automotive, medical, and commercial applications. OEM and distribution support.
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