1. What is the difference between ordinary ferrite inductors, laminated choke inductors and laminated power inductors?
　　From the ferrite material used, the DC bias characteristics of the three are sequentially increased, that is, the DC bias current loaded when the permeability decreases by the same amplitude increases in sequence;
　　From the DC resistance RDC, for products with the same inductance, the three RDCs decrease in turn;
　　Judging from the rated current Ir, the ordinary ferrite inductance Ir is generally lower than tens of milliamperes, the laminated choke inductor Ir is generally tens to hundreds of milliamperes, and the laminated power inductor Ir can reach about 1A;
　　In terms of structural design, on the one hand, the stacked choke inductor and the stacked power inductor need to design a wider and thicker electrode to make the RDC smaller, on the other hand, the stacked choke inductor and the stacked power inductor need to optimize the electrode Structure so that the internal magnetic field of the product is more uniform, improving the magnetic saturation characteristics of the product, that is, increasing the current loaded when the inductance decreases by a certain amplitude;
　　From the perspective of product application, ordinary ferrite inductors are generally used for resonance filtering of signal lines below tens of MHz, and stacked choke inductors are generally used for power line choke and isolation between digital and analog areas, and stacked power inductors It is generally used in the DC-DC circuit to play the role of energy storage and reduce ripple current.
　　2. I now need 1608 size 220nH inductors. Your company's ferrite inductors and ceramic inductors have this specification. I don't know how to choose?
　　Our company's inductors are divided into ferrite inductors and ceramic inductors. The main differences between the two are as follows:
　　(1) The application range is different: ferrite inductors are used at low frequencies, generally below 100MHz; and ceramic inductors are used for high frequencies, and different inductances use different frequencies, ranging from hundreds of megabytes to several gigabytes.
　　(2) Different measurement frequencies: the measurement frequency of ceramic inductors is generally 100MHz; the measurement frequency of ferrite inductors is 50, 25, 10, 4MHz, etc. according to different inductances.
　　(3) The Q value is different: the ceramic inductor has a smaller Q value at the measurement frequency, which is about 10, and the Q value gradually increases as the frequency increases; the Q value of the ferrite inductor is larger, both at the measurement frequency There are about 40, and it becomes smaller as the frequency increases.
　　(4) The DC resistance is different: the resistance of the ferrite inductor is smaller, and the ceramic inductor is larger.
　　(5) Different rated currents: different definitions. The ferrite inductance is defined as the change in inductance, and the ceramic inductance is defined as the temperature rise current.
　　3. What are the main performance parameters of power inductors?
　　(1) The main performance parameters of power inductors are inductance L, DC resistance DCR, DC overlap current Isat, temperature rise allowable current Irms and self-resonant frequency SRF.
　　(2) The inductance is the nominal inductance of the inductor. Due to the existence of magnetic permeability and distributed capacitance, the inductance will change with the change of frequency; the accuracy of the inductance is generally M (±20%) or N (±30 %)files.
　　(3) DC resistance DCR refers to the total DC resistance of the enameled wire used between the product electrodes.
　　(4) The DC superimposed current Isat means that the inductance of the inductor will decrease when the inductor is continuously fed with DC current. Generally, the specifications are set according to the current value when it drops by 30%.
　　(5) The temperature rise allowable current Irms means that the inductor surface temperature will rise when the inductor is continuously fed with DC current. Generally, the specifications are set according to the current value when the temperature rises by 40°C.
　　(6) The self-resonance frequency SRF means that due to the interaction of the inductor and the distributed capacitance of the inductor itself, the inductor will resonate at a certain frequency. This resonance frequency is the self-resonance frequency of the inductor, and the power inductor needs to be used below the self-resonance frequency.
　　4. How to choose the power inductor?
　　When designing new models, we mainly look at the following aspects:
　　(1) First look at the use of power inductors, such as what kind of circuit, general power inductors can be used in DC-DC power supply circuit, audio power supply circuit, CPU circuit and other circuits;
　　(2) If it is a DC-DC loop, the self-resonant frequency of the power inductor is required to be greater than the frequency of the loop;
　　(3) Select the appropriate inductance value according to the design of the circuit. For example, in the DC-DC loop, the main function of the power inductor is energy storage and filtering. Generally, a large inductance corresponds to a strong filtering characteristic, but at the same time, a large inductance will increase the inductance. The RDC of the inductor affects the rated current and response rate of the inductor, so the inductance should be selected reasonably;
　　(4) Select the power inductor according to the size of the loop current. The power inductor generally has two kinds of current, DC overlap current and temperature rise allowable current. When selecting the model, the smaller of them should be used as the rated current value.
　　(5) Finally, select the corresponding size of power inductor according to product size, pad, etc.