Where there is a capacitor, there is an inductor.
When it comes to choosing the best components for a given application, it can be said that capacitors are more concerned than other types of passive components. However, there is usually an inductor where there is a capacitor. The reason is that in order to make the electrical system work normally, the electrostatic characteristics of the capacitor and the electromagnetic characteristics of the inductor are usually used.
The latest advances in ferrite cores and metal composite inductors now 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 winding the conductor around the core, the inductance value can be doubled. The material characteristics of the magnetic core have a great influence on the inductance value, and the shape of the inductor can also be optimized to optimize the characteristics of the inductance.
When a voltage is applied across the inductor, the rate of current rise is related to the voltage and inductance value. A 1V potential on a Henry (1H) inductor will increase the current at a rate of 1A per second. The formula applicable here is: V = L * di / dt.
Inductors have important characteristics that engineers can use to manage energy and control signals. The main characteristics of the inductor include:
Unlike resistors, the electrical energy associated with induced currents is not dissipated as heat, but is stored in the associated magnetic field. When the inductor current is interrupted, it returns to the circuit.
Inductor behavior is frequency dependent.
When the magnetic field stores the energy it can hold, the inductor "saturates". After that, if there is any increase in the current, the magnetic field strength will not increase, and the excess electrical energy will be dissipated as heat.
Using these characteristics, inductors are often used to simulate filter circuits and to manage energy flow in switching power conversion applications.
When circuit designers try to squeeze more functionality into smaller and smaller spaces or increase power density, inductors are needed to provide high inductance values with smaller component sizes. At the same time, in order to avoid power loss and efficiency reduction, harmful parasitic effects such as DC resistance (DCR) must be minimized, and the parameters should be kept relatively stable across temperature changes and the entire operating current range. Improved core material properties allow inductor manufacturers to meet these requirements.
As with any engineering challenge, optimizing the core material properties involves compromises, which, while improving performance in some areas, require trade-offs in others. Although the industry has developed new core material technologies, such as sintered metal powder cores, the advantages offered by traditional ferrite cores will continue to be attractive. As manufacturers find new ways to optimize device characteristics and more tightly control parameters through finer manufacturing tolerances, ferrite core inductors are constantly evolving and improving.
Two main conventional ferrite material formulations are currently used: nickel-zinc (Ni-Zn) and manganese-zinc (Mn-Zn). Ni-Zn ferrites generally have better core resistance, while other component parameters, including saturation characteristics, thermal characteristics, and size-dependent inductance, are less favorable. On the other hand, Mn-Zn cores can achieve high unit volume inductance and high efficiency, while saturation characteristics, heat dissipation performance and core resistance are not so strong.
New Ferrite Core Technology
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 an assembled ferrite. They consist of two parts of a magnetic core and a straight terminal flat wire, as shown in Figure 1. These devices combine the large inductance and high efficiency advantages of Mn-Zn inductors with low DCR and low iron loss.
This structure enables the emergence of vertical directional inductors, such as the TPI series with a width of only 6.0mm. This device is 2.0mm smaller than traditional inductors, which can save a lot of space in high-power applications. For example, a CPU point-of-load (POL) converter needs to use multiple inductors for DC optimization in the area between POL and CPU pins. . Although the space near the device has become extremely limited, it is best to place the inductor close to the pins to minimize dc line losses. Four ultra-thin TPI inductors can be placed in the same PCB area as three conventional inductors.
Figure 1: Assembling a ferrite inductor.
Metal composite core
On the other hand, the industry has developed a new metal composite core material that has better saturation and heat dissipation properties than ferrite devices. The magnetic core of a metal composite inductor is composed of iron powder, and the shape of the magnetic core is formed by mixing these iron powders with a binder and pressing.
In addition, the magnetic core material with high magnetic permeability can reduce the DCR of the inductor, so its self-heating is reduced when working under large current. This can not only improve system efficiency, but also reduce dependence on thermal management devices such as heat sinks (Table 1).
Table 1: Comparison of popular inductor core technologies.
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 for current, but once saturation current is reached, the inductance drops sharply. At higher temperatures, the saturation current is also significantly reduced. Although metal composite inductors exhibit lower nominal inductance relative to component size, they have more progressive saturation characteristics and exhibit higher temperature stability (Figure 2).
Figure 2: Comparison of saturation current and temperature stability of ferrite and metal composites.
GEM Electronics recently introduced a new METCOM inductor series, which includes more than 100 devices with inductance values from 0.10µH to 47.00µH and DCR values as low as 1.5mΩ. These inductors can operate in the temperature range of -55 ° C to + 155 ° C, and the package size is as small as 5.3mm × 5.00mm × 2.0mm, so they are suitable for densely packed power applications and can be used from far below zero to Deploy in challenging environments such as high temperature industrial or automotive engine rooms.
In a typical given inductor structure, the coil is wound on a magnetic core, and the METCOM core is formed on the coil (Figure 3). This will create a non-conductive outer layer, forming a shielding effect, while controlling the magnetic flux inside the inductor body. This can improve work efficiency. EMI performance can also be improved to minimize interference with surrounding circuits.
Figure 3: Structure of a METCOM inductor.
Meet automotive temperature and space constraints
Locations such as the engine room or cabin of a car are often exposed to direct sunlight, so the components used in this type of application can easily withstand high temperatures. METCOM inductors have excellent stability over a wide operating temperature range, so they can provide excellent performance in automotive applications.
On the other hand, where large inductance is required but space constraints are very strict, solutions such as TPI series ferrite inductors can save space and meet important electrical performance requirements.
to sum up
The advent of direct terminal assembled ferrite inductors, and-thanks to the excellent saturation and heat dissipation characteristics and advantages of inherent EMI shielding-the progress made by metal composite inductors has made the tradition between inductor core technology The divide has blurred. Designers now have more choices than ever before, whether for efficiency-centric, size-constrained computing and data center applications, or for space-constrained and temperature-sensitive applications like automotive space To meet the challenges of various power conversion.