SMD inductance and current are converted into electrical energy and stored, and then can be released, which is why the capacitor discharges.

　　The resistance consumes electrical energy and converts it into heat, which can no longer be released. Capacitors convert electrical energy into electric potential energy, while chip inductors convert electric energy into magnetic energy. The electric potential energy is discharged, and magnetic energy generates electricity, while heat energy cannot be converted back through resistance. So the resistance consumes energy. Both inductance and capacitance have an obstructive effect on the current, the inductance is to maintain the current, the inductance is direct resistance to AC, because the direct current through the inductance is meaningless, because the magnetic field does not change. The capacitor is to maintain the voltage, it is through the flow to isolate the AC, because the capacitor in the DC circuit is equivalent to an open circuit, the capacitor is to maintain the voltage.

SMD inductance and current are converted into electrical energy and stored, and then can be released, which is why the capacitor discharges.

　　The resistance consumes electrical energy and converts it into heat, which can no longer be released. Capacitors convert electrical energy into electric potential energy, while chip inductors convert electric energy into magnetic energy. The electric potential energy is discharged, and magnetic energy generates electricity, while heat energy cannot be converted back through resistance. So the resistance consumes energy. Both inductance and capacitance have an obstructive effect on the current, the inductance is to maintain the current, the inductance is direct resistance to AC, because the direct current through the inductance is meaningless, because the magnetic field does not change. The capacitor is to maintain the voltage, it is through the flow to isolate the AC, because the capacitor in the DC circuit is equivalent to an open circuit, the capacitor is to maintain the voltage.

　　Regarding the shelf life of chip inductors, I believe everyone knows it. It is usually 6 months. It depends on the production process and storage environment. In terms of service life, we must start with the characteristics of the magnetic material, usually ferrite. The material is cast at a high temperature of more than 1000 degrees, so it has high strength and can be guaranteed forever; then enameled copper wire. Generally, when selecting an inductor, it will be evaluated based on inductance, DC resistance, DCR, and DC current IDC. Usually it is halved. The smaller the resistance, the better. If all parameters are met, the coil will work easily. Once the inductor is installed on the PCB, it can be permanently guaranteed. Of course, working in harsh environments, or not used as required, the life will be reduced accordingly.

　　The inductance functions respectively to filter high frequency signals and form a DC conversion circuit with MOSFET tubes and capacitors. If the inductance itself is affected by the outside world, it will inevitably affect the stability of the CPU voltage, which will affect the overclocking performance of the CPU and even the stability under the default frequency.

　　The difference between inductance and magnetic beads:

　　Magnetic beads have been explained in more detail in the previous blog post. I believe everyone should have some understanding of magnetic beads. Let’s start with inductors.

　　Inductance is one of the three most commonly used passive components including resistors and capacitors. Functionally, it is mainly used as energy storage components in power conversion circuits, inductive loads and noise filter components in radio frequency circuits.

　　Inductors are classified into winding, film and laminated inductors from the production process; they are divided into shielded and unshielded inductors from the structure; they are mainly divided into surface mount SMT and perforated two types from the installation method; from the application, there are mainly low frequency Signal, power and radio frequency inductance, etc.; from the material, there are mainly magnetic and non-magnetic materials. Magnetic materials include ferrite and iron-based magnetic powder cores. Non-magnetic materials mainly include non-magnetic ceramics. Among them, ferrite and iron-based Magnetic powder core inductors are mainly used in low, medium and high frequency, and non-magnetic ceramic inductors are mainly used in radio frequency applications.

　The technical indicators of inductors mainly include inductance L, DC resistance DCR, saturation current Isat and temperature rise current Irms, self-resonant frequency SRF and quality factor Q, etc.

　　What needs to be explained here is the definition of saturation current. When the current flowing through the inductor gradually increases, the magnetic core will gradually enter a saturated state, and the inductance value will gradually decrease. When the magnetic core is fully saturated, the inductance value will drop to a very small inductance value equivalent to the hollow winding. Saturation current is usually defined as the current value when the inductance drops by 20%. In the inductor shown in the figure below, the saturation current Isat is about 3.6A. Some manufacturers define saturation current as a 10% or 30% drop in inductance. Need to pay attention to this point when choosing the inductance of different manufacturers for comparison.

The temperature rise current Irms of the inductor refers to the operating current of the inductor when the temperature of the inductor rises by a certain temperature compared with the ambient temperature when the inductor is working. Because the temperature rise is related to the energy consumed by the inductor, and the energy is related to the effective value of the current, the temperature rise current is usually marked as Irms. Usually most manufacturers define the temperature rise current value of the inductor when the temperature rises 40C. Some manufacturers will give the current value of 20C and 40C respectively, and even give the following temperature rise current curve.

　　From the above temperature rise current curve, we can see that the temperature rise current of this inductor is about 1.8A when the temperature rise is 20C, and the current is 2.9A when the temperature rise is 40C.

　　It should be noted that the size and curve of the temperature rise current are closely related to the actual measurement conditions, and there is no uniform test method and standard in the world. Usually the temperature rise current of the inductor is measured by welding the inductor to the tested PCB board. Therefore, the line width on the PCB board, the thickness of the PCB copper foil and the test time will all affect the test result of the temperature rise current. In addition, the use conditions of the inductor in the system will also have a great impact on the performance of the inductor, especially the temperature rise characteristics. For example, if the inductor is close to a device that generates a lot of heat in the system, such as a CPU or a heat sink, the temperature rise current of the inductor will decrease accordingly. If the inductor is close to the ventilation hole of the system, the temperature rise current will increase accordingly.

　　Therefore, the temperature rise current is only to provide a reference for the system designer, and it is best to do an actual temperature and temperature rise test on the inductor during use.

　　The saturation current and temperature rise current of the inductor provide designers with more technical information about the inductor from two different technical aspects. The designer has an in-depth understanding of these two indicators, which can improve the performance and performance of the system design. Reliability helps a lot.