Application of chip inductors

Chip inductance can be used in two ways: through the chip inductor to ground or through (low-side low-side MOSFET ground). If it is the latter method, the converter is called "synchronous". Now consider the two-state current flow If the inductance changes. In this process, one end of the high-frequency inductor is connected to the input voltage, and the other end is connected to the output voltage. For a buck converter, the input voltage must be higher than the output voltage, which will form a positive effect on the inductance. In contrast, in the process of state 2, the end connected to the inductor is the input voltage to ground. For a buck converter, the output voltage will be positive, which will form a negative pressure drop on the inductor.

SMD inductors are characterized by a wide range of inductance (mH～H), high power inductance accuracy, low loss (that is, large Q), large allowable current, strong manufacturing process inheritance, simplicity, and low cost, but they have shortcomings It is restricted in further miniaturization. The ceramic core winding type chip inductor can maintain a stable inductance and a relatively high Q value at such a high frequency, so it occupies a place in the high-frequency circuit. 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 wire wound chip inductors, it has many advantages: small size, which is conducive to miniaturization of the circuit, closed magnetic circuit, will not interfere with surrounding components, and will not be interfered by neighboring components, which is beneficial to components High-density installation; integrated structure, high reliability; good heat resistance and solderability; regular shape, suitable for automatic surface mounting production.

 The internal electrodes of the chip inductor are concentrated on the same layer, and the magnetic field is concentrated, which can ensure that the device parameters after mounting do not change much, and show good frequency characteristics above 100MHz. What are the raw materials for inductor production? Iron powder core is mainly a kind of soft magnetic powder core, which is obtained by extrusion molding with pure iron powder added with insulating agent and binder. The general initial permeability is less than 75. This product has Very high saturation magnetic flux density, general products are not suitable for circuits above 200KHz due to their low surface resistance. With the advancement of technology, high-frequency materials continue to appear. Iron powder cores are generally used in power-type magnetic ring inductors, and are more commonly used in various switching power supplies.

Frequency-selective filter inductor: This type of material generally requires low loss, low temperature coefficient, high Curie temperature, and good high-frequency characteristics. It is generally used for color ring inductors. Choke inductors and power inductors: The magnetic core generally requires the characteristics of large saturation magnetic flux and high Curie temperature. It is generally used in magnetic rod inductors and some axial inductors of I-shaped inductors. Manganese-zinc magnetic core is also a kind of soft magnetic core with high initial permeability (2000~15000). The surface resistance of this product is low, and the higher the initial permeability, the lower the surface resistance, so it is generally used in circuits below 1MHz . SMD inductors supply different load transient responses (ic and compensation network also contribute to this response). Need external compensation, but other switching regulator ic contains internal compensation, they usually specify the allowable inductance value range. On the other hand, external compensation allows more flexibility in design options.