Chip inductors, also known as power inductors, high current inductors and surface-mounted high power inductors. Features: miniaturization, high quality, high energy storage and low resistance.
In general, the inductance of an electronic circuit is a hollow coil, or a coil with a magnetic core. And the power inductor also has the hollow coil, also has the magnetic core, the main characteristic is with the thick wire winding system, can withstand tens of amperes, hundreds of thousands, even tens of thousands of amperes.
The power SMT inductor is divided into two types: magnetic housing and without housing, mainly composed of magnetic core and copper wire. It mainly plays a filtering and oscillating role in the circuit.
There are four main types of chip inductors: wound, laminated, braided and film chip inductors. The two types commonly used are wound type and laminated type. The former is the product of traditional winding inductor miniaturization. The latter is made by the multi-layer printing technology and the lamination production process, the volume is smaller than the wound plate inductor, is the key product in the field of inductor components.
It is characterized by a wide range of inductance (mH ~ H), high accuracy of inductance, small loss (i.e. The ceramic core wound chip inductor can maintain a stable inductance and a fairly high Q value at such a high frequency, so it occupies a place in the high frequency circuit.
The NL series inductance of TDK is linear, 0.01~100uH, precision 5%, high Q value, which can meet the general requirements.
NLC type is suitable for power supply circuit, rated current up to 300mA; NLV type has high Q value, environmental protection (recycled plastic), and can be interchanged with NL; NLFC has a magnetic screen, suitable for power cords.
It has good magnetic shielding, high sintering density and good mechanical strength. The disadvantages are low pass rate, high cost, small inductance and low Q value.
Compared with the winding inductor, it has many advantages: small size, conducive to circuit miniaturization, closed magnetic circuit, will not interfere with the surrounding components, will not be affected by the adjacent components, conducive to the components of high density installation; Integrated structure, high reliability; Good heat resistance and weldability; Neat shape, suitable for automatic surface installation and production.
MLK inductor of TDK, small size, good solderability, magnetic screen, high density design, monolithic structure, high reliability; MLG type has small sensitivity and adopts high frequency ceramics, suitable for high frequency circuits; MLK operating frequency 12GHz, high Q, low sensitivity (1n~22nH)
Thin film chip
It has the characteristics of keeping high Q, high accuracy, high stability and small volume in microwave frequency band. Its internal electrodes are concentrated in the same layer, and the magnetic field distribution is concentrated, which can ensure that the device parameters change little after mounting and present good frequency characteristics above 100MHz.
The weaving type
The characteristic is that the inductance per unit volume at 1MHz is larger, smaller and easier to install on the substrate than other chip inductors. A miniature magnetic element used for power processing.
1, surface mount high power inductance.
2. Features of miniaturization, high quality, high energy storage and low resistance.
3. Mainly used in computer display board card, laptop, pulse memory program design, and dc-dc converter.
4. Scroll packaging is available for automatic surface mount.
The characteristics of
1. Flat bottom surface is suitable for surface mounting.
2. Excellent solderability with good end strength.
3. High Q value and low impedance.
4, low magnetic leakage, low direct resistance, resistance to large current characteristics.
5. Braided packaging can be provided to facilitate automatic assembly.
The main products
Power inductance, pressure inductance, integrated inductance, magnetic adhesive inductance, laminated inductance, SMD inductance, power inductance, inductance, adjustable inductance, chip inductance, high power inductance, high current inductance and so on. Products are widely used in digital products, PDA, laptop, mobile phone, network communication, video card, LCD backlight, power module, automotive electronics, security products, office automation, home appliances, walkie-talkie, electronic toys, sports equipment and medical equipment.
The three most important points to consider when choosing an inductor for a portable power supply application are size, size, and third, size. The size of a mobile phone’s circuit board is tight, especially as MP3 players, televisions and video are added to the phone. Increased functionality will also increase the battery’s current consumption. Therefore, modules that have previously been powered by linear regulators or connected directly to batteries require more efficient solutions. The first step to a more efficient solution is to use a magnetic step-down converter. As the name implies, an inductance is required.
The main specifications of inductance include inductance at switching frequency, dc impedance (DCR) of coil, rated saturation current, rated RMS current, ac impedance (ESR) and Q factor. Depending on the application, the choice of inductance type – shielded or unshielded – is also important.
Similar to the dc bias in capacitors, manufacturer A’s 2.2db H inductance may be completely different from manufacturer B’s. The relationship between inductance and dc current in the relevant temperature range is a very important curve and must be obtained from the manufacturer. The rated saturation current (ISAT) can be found on this curve. ISAT is generally defined as the dc current when the inductance drop is 30[[%]] of the rated value. Some inductance manufacturers do not specify ISAT. They may have only given the dc current at temperatures higher than the ambient temperature of 40 ° c.
With iron powder cores, they provide better temperature stability and are less costly than other alternative cores. The SMT inductor profile provides flexibility and variability when necessary, but at a higher cost. High flux loops are usually found in filter inductors rather than in power conversion circuits. Another performance tradeoff can be seen in the typical waveforms of inductive current, inductive voltage (pins 14 to 16) and output voltage ripple. The small inductance fdv0620-0.47h inductance is used to generate a high peak current, and the output voltage ripple is lower than the peak value of 18mv.
The SMT inductor produces a ripple peak of just over 12mv. The peak current charges the output capacitor and supplies the load current. Large currents will flow in and out of the capacitor, which will produce higher output voltage ripple. SMD inductor is mainly used in power filter circuit. Inductor is an energy storage element, which focuses on restraining conductive interference. SMT inductors use inductive elements and EMI filter elements extensively in PCB circuit of electronic equipment. In the resonant circuit, the inductance must have high Q, narrow inductance deviation, stable temperature coefficient, in order to achieve the resonant circuit narrow-band, low frequency temperature drift requirements. High Q circuits have sharp resonant peaks.
The SMD inductor is an electromagnetic induction element made by winding an insulated wire. It is a common inductance element. The function of SMD inductor: dc resistance ac this is a simple way of saying that the ac signal isolation, filtering or with capacitors, resistors and other resonant circuit. Functions of tuning and frequency-selecting inductors: an LC tuning circuit can be formed by connecting an inductor coil in parallel with a capacitor. Any current in the SMT inductor generates a magnetic field, the magnetic flux of which ACTS on the circuit.
When the current through the SMT inductor changes, the dc voltage generated in the SMT inductor will prevent the current from changing. When the current through the inductance coil increases, the self-inductive electromotive force generated by the inductance coil is the same as the current when the current through the inductance coil decreases. Flow in the opposite direction, to prevent the increase of the current, at the same time to convert part of the electrical energy into magnetic field energy stored in the inductor; Therefore, after inductance filtering, not only the pulsation of load current and voltage decreases, the waveform becomes smooth, but also the conduction Angle of rectifier diode increases.
SMD inductor with general SMD inductance shielding, average patch of inductance in the circuit is not to bring a mask, use up in the circuit inductance don’t want to, the effect of shielding SMT inductance can block out some of the current in the circuit is not stability, good have the effect of blocking, shielding inductive complete metal shield will positively charged conductor surrounded by at the inner side of the shield will be induced with a charged conductor equal amounts of negative charge, the outer appearance and charged conductor of the same amount of positive charge, if the metal shield grounding, the outside of the positive charge will flow into the earth, the lateral electric field will not exist, That is, the electric field with a positive conductor is shielded in a metal shield.
The shielding inductance also plays a coupling role in the circuit. To reduce the coupling interference voltage of the alternating electric field to the sensitive circuit, the shielding inductance can set a metal shield with good conductivity between the interference source and the sensitive circuit, and grounding the metal shield. The coupling interference voltage of ac field to sensitive circuit depends on the product of ac field voltage, coupling capacitance and grounding resistance of metal shield. As long as the metal shield is well grounded, the coupling interference voltage of the ac field to the sensitive circuit can be minimized. Electric field shielding is mainly reflection, so the thickness of shielding body need not be too large, but the structural strength is the main factor.
SMT inductance is a property of closed loop. When the coil of the SMT inductor passes an electric current, the SMT inductor forms a magnetic field induction in the coil, and the induced magnetic field generates an inductive current to resist the current passing through the coil. The function of SMT inductor in the circuit is to produce the changing magnetic field when passing the unsteady current, which in turn will affect the current. SMT inductor is connected in the power supply loop, such as inductance, which is direct to dc and high resistance to high-frequency pulse, so it plays the role of blocking ac pulse through dc.
The resistance is used to control the current in the circuit, the capacitor is used to block the direct flow of the ac, the inductor is used to block the high frequency to the low frequency, on the other hand, the capacitor and the inductor are energy storage elements, so there is a filtering function in the circuit. The SMT inductor has the property of preventing ac current from passing through the circuit and allowing dc current to pass through smoothly. The characteristics of inductance are dc and ac resistance, the higher the frequency, the greater the coil impedance. Inductors often work with capacitors in a circuit
An inductor coil has the property of preventing current changes in an ac circuit. Inductance coil has similar characteristics with inertia in mechanics, which is named “self-induction” in electricity. When the SMD inductance is at low frequency, the inductance generally presents the characteristics of inductance, which only stores energy and filters high frequency, but at high frequency, its impedance characteristics are very obvious. There are energy dissipation and heating, reduced inductive effect and other phenomena. Different inductors have different high frequency characteristics.
Radio frequency (RF) and wireless communications, information technology equipment, radar detectors, automotive electronics, cellular phones, pagers, audio equipment, PDAs, wireless remote control systems and low-voltage power supply modules.
SMT inductor is a common electronic component. When the current through the wire, the wire will produce a certain electromagnetic field around the wire, and in the electromagnetic field in the wire induced electromotive force – self-induction electromotive force, we call this action electromagnetic induction. To enhance electromagnetic induction, an insulated wire is often wound into a coil of a certain number of coils.
The inductive reactance XL of SMT inductor, the inductive reactance XL is generally not found in the inductance element parameter table, but it is closely related to the inductance quantity, inductance element classification quality factor Q and other parameters, it is often used in the analysis circuit, so it is specially introduced here. As mentioned above, since the self-inductive potential of the inductor coil always prevents the change of current in the coil, the coil has a resistance effect on the alternating current. The resistance is expressed by the inductive reactance XL. It is not difficult to see that XL is small when the coil passes low frequency current. When passing through dc, XL is zero, and only the dc resistance of the coil ACTS as resistance. Because the resistance is very small, it is approximately short circuit. When passing through the high frequency current, XL is large; if L is also large, then it is approximately open circuit. This characteristic of the coil is the opposite of that of the capacitor, so it is possible to construct various high, medium, and low frequency filters, as well as tunable, selective, and stop-coil circuits, by means of inductive elements and capacitors.
Matters needing attention
1. Pay attention to the humidity and dryness of the inductor, the ambient temperature, the high frequency or low frequency environment, and the sensitivity or impedance characteristics of the inductor.
2. Frequency characteristics of the inductor
At low frequency, the SMT inductor generally presents the characteristics of inductance, that is, it only stores energy and filters high frequency. But at high frequencies, its impedance characteristics are obvious. There are energy dissipation and heating, reduced inductive effect and other phenomena. Different inductors have different high frequency characteristics.
3, inductor design to withstand the large current, and the corresponding heating situation.
4. When using the magnetic ring, compare the magnetic ring part above to find out the corresponding l value and the applicable range of materials.
5, pay attention to the wire (enameled wire, yarn wrap or naked wire), commonly used enameled wire. Find the most suitable warp.