Chip inductors, also known as power inductors, high-current inductors and surface-mounted high-power inductors. It has the characteristics of miniaturization, high quality, high energy conservation and low resistance. Power chip inductors are divided into two types: magnetic shield and magnetic shield, which are mainly composed of magnetic cores and copper wires. It mainly plays the role of filtering and oscillation in the circuit. The main parameters of SMD inductance include inductance, allowable deviation, distributed capacitance, rated current and quality factor.
The five important parameters of patch inductance are explained as follows
I. inductance
Inductance: no-load measurement (theoretical value) and measurement in actual circuit (actual value). Because inductance uses too many practical circuits, it is difficult to classify them. Only the measurement under no-load condition will be explained.
The amount of inductance mainly depends on the number of turns, the winding method, the presence or absence of the core and the material of the core. Generally, the more coils are wound, the denser the coils are wound, and the greater the inductance is. Coils with cores have a larger inductance than coils without cores. The greater the magnetic permeability of the core, the greater the inductance. Therefore, there are many factors that determine the inductance. The basic unit of inductance is Henry, which is represented by the letter "H". Commonly used units are milliheng (mH) and micro-heng (μH), and the relationship between them is: 1h = 1000 MH; 1mH=1000μH。
Second, the allowable deviation
Allowable deviation: the allowable deviation is expressed by English letters behind the inductance unit, and the allowable deviation expressed by each letter is shown in the following table. For example, 560uHK means that the nominal inductance is 560uH, and the allowable deviation is 10% of the soil. The character symbol is French character symbol method, which marks the nominal value and allowable deviation value of the inductor on the inductor by combination of numbers and characters according to a certain rule. In this display method, the unit of some low-power inductors is usually nH or pH, and N or R represents the decimal point. For example, 4N7 means the inductance is 4．7nH, and 4R7 means the inductance is 4．7uH; 47N indicates that the inductance is 47nH, and 6R8 indicates that the inductance is 6．8uH
The allowable error value of the marked induction quantity and the actual induction quantity. The chip inductance generally used for vibration or filter circuit requires high precision, and the allowable deviation is 0.2% ~ 0.5%; The precision of coupling or high frequency choke is not high, and the allowable deviation is 10% ~ 15%.
Third, distributed capacitance
Distributed capacitance: the capacitance existing between turns of the coil and between the coil and the magnetic core. The smaller the distributed capacitance, the better its stability. Generally, the nalog circuit area and the digital circuit area are reasonably separated, the power line and the ground line are separately led out, and the power supply points are slightly concentrated. In addition, in the home comprehensive wiring, the 220V power line must be wired separately from the telephone line, network line, audio and video line, and should not be laid in parallel as far as possible.
IV. Rated current
Rated current: Rated current refers to the current when the product equipment runs at rated voltage and rated power. The maximum current allowed to pass through when the chip inductor works normally. Burned when working current exceeds rated current.
V. Quality factor
Quality factor: also known as Q value or excellent value, it is the main parameter for measuring inductance quality. It refers to the ratio of inductance to equivalent loss resistance when the chip inductor works under AC voltage with a certain frequency. The higher the Q value, the smaller the loss and the higher the efficiency.
