FAQ

Inductors & Coils Application Notes

What is a Inductor?
The inductor also called for coil, choke or reactor. Is a passive component with two two-terminal, designed to resist changes in current.

Inductors are often referred to as "AC resistors". The ability to resist changes in current and store energy in its magnetic field account for the bulk of the useful properties of inductors. Current passing through an inductor will produce a magnetic field. A changing magnetic field induces a voltage which opposes the field-producing current. This property of impeding changes of current is known as inductance.

In general, the relationship between the time-varying voltage v(t) across an inductor with inductance L and the time-varying current i(t) passing through it is described by the differential equation:

v(t) = L \frac{di(t)}{dt}

When there is a sinusoidal alternating current (AC) through an inductor, a sinusoidal voltage is induced.

What is difference between each core materials?
Ferrite Core

Ferrite is a magnetic material which consists of a mixed oxide of iron and other elements that are made to have crystalline molecular structure. The crystalline structure is created by firing the ferrite material at a very high temperature for a specified amount of time and profile. The general composition of ferrites is xxFe2O4 where xx represents several metals. The most popular metal combinations are manganese and zinc (MnZn), and nickel and zinc (NiZn). These metals can be easily magnetized.



Ceramic Cores

Ceramic is one of the common materials used for inductor cores. Its main purpose is to provide a form of the coil. In some designs, it also provides the structure to hold the terminals in place. Ceramic has a very low thermal coefficient of expansion. This allows for relatively high inductance stability over the operating temperature ranges. Ceramic has no magnetic properties. Thus, there is no increase in permeability due to the core material. Ceramic core inductors are often referred to as "air core" inductors. Ceramic core inductors are most often used in high-frequency applications where low inductance values, very low core losses, and high Q values are required.



Kool Mu® Core

Kool Mu® is a magnetic material that has an inherently distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials, such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates. Kool Mu material is an alloy that is made up of nickel and iron powder (approx. 50% of each) and is available in several permeabilities. It has a higher permeability than powdered iron and lowers core losses. Kool Mu performs well in power switching applications. The relative cost is significantly higher than powdered iron.



MPP Core

MPP is an acronym for molypermalloy powder. It is a magnetic material that has an inherently distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials, such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates. The basic raw materials are nickel, iron, and molybdenum. MPP stores higher amounts of energy and has a higher permeability than Kool Mu. The core characteristics allow inductors to perform very well in switching power applications. Since higher energy can be stored by the core. The cost of MPP is significantly higher than Kool Mu, powdered irons, and most ferrite cores with similar sizes.



Powdered Iron Core

Powdered iron is a magnetic material that has an inherently distributed air gap. The distributed air gap allows the core to store higher levels of magnetic flux when compared to other magnetic materials, such as ferrites. This characteristic allows a higher DC current level to flow through the inductor before the inductor saturates. Powdered iron cores are made of nearly 100% iron. The iron particles are insulated from each other, mixed with a binder (such as phenolic or epoxy) and pressed into the final core shape. Powdered iron cores are typically the lowest cost alternative and their permeabilities typically have a more stable temperature coefficient than ferrites.



Laminated Cores

Cores constructed by stacking multiple laminations on top of each other. The laminations are offered in a variety of materials and thicknesses. Some laminations are made to have the grains oriented to minimize the core losses and give higher permeabilities. Each lamination has an insulated surface which is commonly an oxide finish. Laminated cores are used in some inductor designs but are more common in a wide variety of transformer applications.

Useful term for Inductors
AC

Alternating current (AC) is an electrical current that continually reverses direction. This change in direction is expressed in Hertz (cycles per second).



ADSL

Asymmetrical Digital Subscriber Line uses DMT (Discrete Multi Tone) modulation and supports speeds of 6 to 8 Mbps downstream and up to 640 Kbps upstream. (Refer to DSL for further info.)



Ambient temperature

The temperature of the medium surrounding a component or circuit.



ATM

Asynchronous Transfer Mode is a comprehensive connection-oriented transmission protocol based on fixed length cells or packets of 53 bytes. The protocol is independent of transfer rates so that it can seamlessly scale from a few megabits to multiple gigabits per second.



Attenuation

The relative decrease in amplitude of a given parameter. Attenuation measurements are common for voltage, current, and power. It is usually expressed in units of decibels (dB).



Axial-lead

Wire terminals that exit from opposite ends of a component along a common line (axis).



Bobbin

The receptacle (usually plastic) around which magnet wire is wound. A core is inserted through the bobbin after the wire has been wound.



Boost regulator (DC/DC)

A basic DC/DC switching converter topology that takes an unregulated input voltage and produces a higher, regulated output voltage. This higher output voltage is achieved by storing energy in an input inductor and then transferring the energy to the output by turning a shunt switch (transistor) on and off.



Buck regulator (DC/DC)

A basic DC/DC switching converter topology that takes an unregulated input voltage and produces a lower, regulated output voltage.



CAP

This is a special type of modulation technique called Carrierless Amplitude Phase.

(Refer to HDSL for further info.)



Ceramic cores

Ceramic is one of the common materials used for inductor cores. Its main purpose is to provide a form of the coil. In some designs, it also provides the structure to hold the terminals in place. Ceramic has a very low thermal coefficient of expansion. This allows for relatively high inductance stability over the operating temperature ranges. Ceramic has no magnetic properties. Thus, there is no increase in permeability due to the core material.



Choke

Another term for an inductor which is intended to filter or choke out signals.



Coils

Another common name for inductors. (See Inductor.)



Common-mode noise

Noise or electrical interference that is common to both electrical lines in relation to earth ground.



Copper loss

The power lost by current flowing through the winding. This power loss is transferred into heat.



Core

The material used to concentrate and conduct the magnetic field in an inductive component in most cases. Ceramic does not have magnetic properties. In some cases, magnet wire may be wound directly around the core, eliminating the need for a bobbin.



Core losses

Core losses are caused by an alternating magnetic field in the core material. The losses are a function of the operating frequency and the total magnetic flux swing. The total core losses are made up of three main components: Hysteresis, eddy current and residual losses. These losses vary considerably from one magnetic material to another. Applications such as higher power and higher frequency switching regulators and RF designs require careful core selection to yield the highest inductor performance by keeping the core losses to a minimum.



Curie temperature

The temperature above which a ferrite core loses its magnetic properties.



Current rating

The maximum value of current at which an inductor will continue to operate without possible damage.



DC

Direct current (DC) is the electrical current that flows in one direction. Example: battery in a flashlight.



DC/DC converter

A circuit or device that converts a DC input voltage to a regulated output voltage. The output voltage may be lower, higher or the same as the input voltage. Switching regulator DC/DC circuits most often require an inductor or transformer to achieve the regulated output voltage.



DCR (DC resistance)

The resistance of the inductor winding measured with no alternating current. The unit of measure is ohms, and it is usually specified as a maximum rating.



Distributed air gap

Air gaps are distributed throughout the core structure with an adhesive material to insulate the core particles.



Distributed capacitance

In the construction of an inductor, each turn of wire or conductor acts as a capacitor plate. The combined effects of each turn can be represented as a single capacitance known as the distributed capacitance.



DSL

Digital Subscriber Line is a fairly new modem technology using very sophisticated modulation techniques. There is virtually no restriction on the used frequency spectrum, therefore converting existing pair telephone lines into high-speed access paths allowing the transmission of voice, music, video and high-speed data.



EMC

This is an acronym for electromagnetic compatibility. An electronic device is said to have a high EMC when it doesn’t cause problems for its electronic neighbors (radiated emissions) and all EMI is successfully filtered or shielded from its own electronic circuits.



EMI

EMI is an acronym for Electromagnetic Interference. It is unwanted electrical energy in any form.



Eddy current losses

Eddy current losses are present in both the magnetic core and winding of an inductor. Eddy currents in the winding (or conductor) contribute to two main types of losses: losses due to proximity effects and skin effects. As for the core losses, alternating magnetic flux generates an electric field around the flux lines in the magnetic field.

Ethernet (IEEE 802.3)

It is a 10/100/1000 Mbps CSMA/CD network that runs over thick coax, thin coax, twisted pair or fiber optic cable.



Ferrite core

Ferrite is a magnetic material which consists of a mixed oxide of iron and other elements that are made to have a crystalline molecular structure. Firing the ferrite material at a very high temperature within a defined profile creates the crystalline structure.



Frequency

The rate of change from positive to negative, and back again, of an alternating current (AC) measured in Hertz.



HDSL

High bit rate Digital Subscriber Line uses 2B1Q or CAP (CarrierlessAmplitude/Phase) modulation techniques and has a fixed line speed of 2 Mbps. (See DSL for further info.)



Hertz

Unit of change for the alternating waveform. 1 Hertz = 1 cycle per second.



HF

High signal Frequency from 3 to 30 MHz.



Impedance

The impedance is the total resistance to the flow of current, including the AC and DC component, and is given in ohms.



Inductance

Once the current in an inductor changes, it produces a varying magnetic field, which will cut across any other inductor nearby, thereby inducing a voltage into these inductors. The induced voltage is proportional to the inductance value and the rate of current change.



Inductor

A passive component designed to resist changes in current. Inductors are often referred to as “AC resistors”. The ability to resist changes in current and the ability to store energy in its magnetic field are the significant, useful properties of inductors.



Insertion loss

The loss of voltage introduced into a circuit by the transformer. Although a transformer may approach an efficiency of 99 %, a small loss of voltage across it is expected.



Interwinding capacitance

The capacitance that exists between the windings of a transformer (or multiple winding inductor). A low value of capacitance is desired in inductive components.



ISDN

The Integrated Services Digital Network is commonly called the ISDN and is simply an all-digital communications network. It is an invisible rebuilding of the old telephone network that will allow simultaneous voice and data communication over ordinary telephone lines.



Leakage inductance

Those lines of the magnetic field that do not link the coils of a transformer.



Litz wire

Wire whose conductor consists of multiple strands. Litz wire provides superior performance at high frequency.



LAN

Local Area Network. A LAN is a group of computers, each connected to the appropriate network adapter card and software, connected by cable or wireless media to enable users to share applications, data, and peripherals.



Magnet wire

Wire used to create a magnetic field such as those in magnetic components (inductors and transformers). Magnet wire is nearly 100 % copper.



Matched impedance

The condition that exists when two coupled circuits are adjusted so that the output impedance of one circuit equals the input impedance of the other circuit.



Medium frequency

Signal frequency between 300 KHz – 3 MHz.



Multilayer inductor

An inductor constructed by layering the coil between layers of core material. The coil typically consists of a bare metal material (no insulation). This technology is referred to as “non-wirewound”. The inductance value can be made larger by adding additional layers.



Noise

Unwanted electrical energy in a circuit that is unrelated to the desired signal.



Non-shielded inductor

An inductor whose magnetic field radiates around the inductor, and may contact adjacent components or current paths on a PC board.



Ohm

The unit of measurement for resistance and impedance. Resistance is calculated by Ohm's Law: R = V/I where R = resistance V = voltage I = current



Operating temperature range

The span of temperature over which a device will perform with power applied.



PAM

Pulse Amplitude Modulation is a modulation technique used in xDSL technologies.

Permeability

The ability of a material to concentrate lines of magnetic flux comprising a magnetic field. Air has a permeability of 1; nickel-iron alloys have a permeability as high as 100,000.



POTS

The normal voice band telephony network is commonly referred to as the “Plain Old Telephone Service”.



Primary (winding)

The winding of the transformer into which current is flowing from an outside source.



QAM

Quadrature Amplitude Modulation



Q

The Q value of an inductor is a measure of the relative losses in an inductor. The Q is also known as the “quality factor” and is technically defined as the ratio of inductive reactance to effective resistance.



Radial-lead

Wire terminals that exit from a common side of a device. These terminals are usually parallel to each other.



Rated current

The level of continuous DC current that can be passed through the inductor. This DC current level is based on a maximum temperature rise of the inductor at the maximum rated ambient temperature.



Saturation current

The DC bias current flowing through the inductor which causes the inductance to drop by a specified amount from the initial zero DC bias inductance value. Generally, specified

inductance drop percentages include 10 % and 20 %.



Secondary (winding)

The winding of the transformer into which current is induced by the magnetic field generated by the primary.



Semi-shielded inductor

Inductor utilizes epoxy-ferrite powder mixture resin applied to the perimeter of winding forming a magnetic shield. The shielding effectiveness is less than the conventional shielded inductor. However, it has lower radiation than the non-shielded inductor.



Sendust core

Core has distributed air gap that is made from the mixture of 85 % iron, 6 % aluminum and 9 % silicon powders.



S-HDSL

Symmetric High bit rate Digital Subscriber Line. Technology still undergoing standardization with speeds up to 2 Mbps.



Shielded inductor

An inductor whose magnetic field is held within the boundaries of shielding material that surrounds the inductor, thus eliminating the majority of its magnetic field radiation to the adjacent surroundings.



SMT

Surface Mount Technology



SRF (self-resonant frequency)

The frequency at which the inductor's distributed capacitance resonates with the inductance and therefore cancel each other. It is not an independent parameter, since the other parameters of Q, DCR, and L are also specified.



Skin effect

Alternating (AC) current has the tendency to flow near the surface of the conductor instead of utilizing the entire cross-sectional area of the conductor. This phenomenon causes the resistance of the conductor to increase. The current flow is forced further to the outer surface of the conductor as the frequency increases. Eddy currents are also induced into the center of the conductor, which in turn opposes the main current flow (near the surface).



Storage temperature range

The span of temperature to which a non-operating device can be exposed and still be expected to function.



Surface mount

The method of attaching a device to a board by means of metalized pads on the surface of the board that aligns with terminals on the bottom of the device.



Temperature rise

The increase in temperature of a component in the free-standing air due to its power dissipation.



Through-hole

The method of attaching a device to a board by means of the terminal pins of the device passing through holes in the boards, then bonding the pins inside the holes. Axial-lead and radial-lead devices are through-hole components.



THT

Through-hole Technology



Tolerance

The allowable variation from the specified value. For example, an inductor whose value is specified as 10 µH ±10 %, has a specified value of 10 µH and a tolerance of 10 %. It is acceptable for the value of the inductor to deviate from 10 µH by as much as ±10 %.



VDSL

Very high bit rate Digital Subscriber Line. The standards for this type of technology have not been finalized yet. The operational bandwidth is in excess of 10 MHz with speeds of up to 52 Mbps (in asymmetrical mode) and up to 26 Mbps (in symmetrical mode).



Volt-microsecond constant

The measure of the energy handling capability of a device. The energy is described by a waveform with an area defined in volt-microseconds. This area is the product of the amplitude in volts and the duration in seconds.



Winding

The term for the coil of wire wrapped around the bobbin or core of an inductive device.

What is the Market Segments & Applications for different inductors?
Chip Beads



* Market Segments

Computer

Consumers

Industrial

Instrumentation

Medical electronics

Power management

Telecom

* Applications

EMI noise filtering

Power supply lines

IC power lines

Signal lines



Common Mode Inductors



* Market Segments

Computer

Consumers

Industrial

Instrumentation

Medical electronics

Telecom

* Applications

EMI noise filtering

Signal lines

CAN bus



SMD Power Inductors



* Market Segments

Computer

Consumers

Industrial

Instrumentation

Medical electronics

Power management

Telecom

* Applications

Switch-mode power suppliers

DC/DC converters

Output chokes

EMI filters



Chip Inductors



* Market Segments

Computer

Consumers

Industrial

Instrumentation

Medical electronics

Telecom

* Applications

EMI noise filtering

Signal lines



Through-Hole Inductors (T coil inductor)



* Market Segments

Computer

Consumers

Industrial

Instrumentation

Medical electronics

Power management

* Applications

Switch-mode power suppliers

DC/DC converters

Output chokes

EMI filters



Data Tarnsformers



* Market Segments

Consumers

Industrial

Instrumentation

Telecom

* Applications

Isolation

Impedance matching

Modems

Network cards

Audio and digital signal processing

How to select inductor?
Inductors, also called a coil or reactor, are passive two-terminal components which have the different function, such as for filtering, timing, and power electronics applications. Power Inductor (SMD / Pin type of inductor) store energy in the form of magnetic fields as long as a current is flowing. The unit of inductance is Henry (H). Moreover, the inductor can be approximated as an open circuit for AC signals and as a short circuit for DC signals.   

The inductance value will affect by several factors, the most common one is like below, the size of the coil area, the number of turns in the coil, coil length and the most important one the material of the core. Coilmaster Electronics have strong engineer team, most of our engineers have ferrite core design background, this advantage could assist our customer to design/amend the core material to fulfilled customer’s expectation. The inductor have several types of structure, some is SMD inductor (shielded, semi shielded or unshielded) / Leaded inductor(shielded or unshielded) normally have a Magnetic core made of iron or ferrite inside the coil, which serves to increase the magnetic field and thus the inductance. On the other hand, inductors with a magnetic core have losses such as hysteresis and eddy currents 

Normally, when selecting an inductor, several parameters that are crucial to take into consideration. Self-Resonant Frequency (SRF) , Q factor, DC Resistance (DCR) and Saturation Current. We will try to explain each factor as below.



§  Q factorall called a Quality Factor, refers to the ratio of an inductor’s reactance to effective resistance. This value is frequency dependent and test frequency is often specified in datasheets. Q factor impacts the sharpness of the center frequency in an LC circuit. Usually, a high value of Q factor is preferred. Moreover, according to the formula, Q=wL/R, the high Q air core inductors often have large diameters and many turns.

§   Self-Resonant Frequency (SRF), the inductor will have no function beyond specific frequency, this frequency is called self-resonant frequency (SRF). The inductor has low distributed capacitance between terminal electrodes or the turns of a wire-wound conductor, and its inductance with such distributed capacitance resonates at a certain frequency. Therefore, when selection of SMD inductor/ high current inductor/ shielded SMD inductor or pin type inductor for RF circuits, the higher value of SRF (self-resonant frequency) should be chosen. The SRF value should exceed the operating frequency of the circuit. As the inductance is zero at the self-resonant frequency, the Q factor is zero also.

§  Saturation Current refers to the DC current which result in the drop inductance to specified inductance value, normally the percentage of decreasing will be from 5% to 30% (more strict standard, such as 2% is still available) compare to original inductance value. At the specific current which the core is completely filled with magnetic flux, that will result in the inductance drops. While saturation current is related to the magnetic properties of the inductor, rated current is related to physical properties, and it describes the maximum DC current that can be passed in an inductor.

§  DC Resistance (DCR) refers to the resistance inherent in the metal conductor of the inductor, and it can be modeled as a resistor in series with the inductor. DC resistance is an important parameter in DC-DC converters design as the resistance leads to I2R losses thus reducing the efficiency.

§  Tolerance is the variation in the inductance value of an actual inductor compared to the specified value in the datasheet. This could result in an unwanted shift in frequency selection of an RF filter.

 



INDUCTOR TYPES  

The engineers will choose the“choke”inductor for blocking or decoupling higher frequencies. Here are several types of core material will be used in cores and construction. The most famous type is Ferrite core inductor, Iron powder inductor(molded inductor / high current inductor), the Toroidal inductor (Leaded inductor/Pin type inductor), Axial inductor, Semi-shielded inductor (Cost effective solution product).



I. Air Core Inductor / RF Inductors / Spring Air Core Inductors 

Air-core inductors, RF Inductor or Spring Air Core Inductor usually is the same type of inductors. Normally is SMD surface mount type. From these product, it does not use any magnetic core. The advantage for the air-core inductor is that have a high Q factor value and low losses. On the other hand, as the RF inductor, to gain the same value of inductance result in the bigger size (compare to the inductor with magnetic core). The air core inductor is mainly used in high-frequency applications such as resonant circuits where low inductance values are sufficient. 

Part Selection: Coilmaster SS series 

II. Ferrite Core Inductor
Ferrite core inductors are made of a ferromagnetic material which has high permeability. These inductors have much wilder inductance range compare to other types of SMD inductor. And the advantage of ferrite core inductor is low power losses. Ferrite core inductor is used in noise filters, high-quality transformers, and DC-DC converters

Part Selection: Coilmaster MW series

III. Iron Core Inductor 

Iron core inductors(molded inductor / high current inductor) can have very high saturate current(soft saturation). Molded SMD inductor / High current inductor can handle very high power but are limited in high-frequency capacity and limited inductance value also, usually be used in low-frequency applications such as audio equipment, DC-DC converter. Coilmaster Electronics have the complete production line in the field of high current power inductors could use to design in power supply inductor, SMD high current inductorshigh saturate current inductorhigh power inductorsurface mount inductor, or other circuits which may require a high saturate current inductors. 

Part Selection: Coilmaster SEP series    

IV. Toroidal / Leaded / Pin type Inductor

When inductors are wound around a ring or circular toroid, they are referred to as toroidal inductors. The Toroidal / Leaded / Pin type Inductor possess the higher inductance and Q factor than an inductor with the straight core. Toroidal / Leaded / Pin type Inductor structure is suitable for large current, high inductance or high Q factor applications. These inductors are used in DC-DC switching voltage regulators, medical and refrigeration equipment, telecommunication circuits and more. Coilmaster Electronics could offer customize item to meet customer’s requirement. Since we have the strong background at ferrite core, we could adjust the core material and winding condition.

Part Selection: Coilmaster TC series

V. Axial Leaded Inductor 
Axial lead inductor is wound on a cylindrical bobbin and can be both axial leaded or radial leaded, Coilmaster offer various size to our customers, such as 0204,0307,0410,0510,0612. The lager or customized one is also available at Coilmaster. The axial lead inductor (RF Inductors) are mostly used for printed circuit boards (PCBs).  They vary widely in terms of power rating, operating frequencies, size and other parameters.

Part Selection: Coilmaster AL series

VI. Ferrite Beads 
Ferrite Beads are passive components that use to remove high-frequency electromagnetic interference (EMI) noise from a circuit. It is a specific type of electronic choke. Ferrite beads are used as inductors to form a passive low-pass filter. Normally, Ferrite beads are placed in series with the signal source. When selecting the ferrite beads, it is preferred to have low values of DCR (dc resistance). However, some application will need high impedance value over some defined frequency range to suppress the noise. 

Part Selection: Coilmaster SMB series

How to select the Inductor for LED application?
Buck Circuit

A buck circuit regulates input DC voltage down to the desired DC voltage.

Buck circuits usually require one inductors. The following series and part number are typical Coilmaster inductors

used in buck circuits.

SEP Series: SEP0412, SEP0402, SEP0603, SEP1004

SDC Series: SDC103R, SDC104R, SDC105R,

SDS Series: SDS1608, SDS0805, SDS5020, SDS5030, SDS6020, SDS6030, SDS73, SDS74, SDS124, SDS125,

SDS127

SDR / SRS Series: SDR54S, SDR75S, SRS74R, SRS105R

SD Series: SDC2D14, SDC3D16, SDC3D18, SDC3D28, SDC4D18, SDC4D22, SDC4D28, SDC5D18, SDC5D28,

SDC5D33, SDC6D28, SDC6D38, SDC8D38, SDC8D43,

For more information go to:

https://www.coilmaster.com.tw/s/2/product-c66906/Shielded-Power-Inductor.html



Buck-Boost

The output voltage generated from Buck-Boost circuit that is either higher or lower than the input voltage. The

polarity of the output is opposite to that of the input.

Normally, will be one inductor used on the Buck-Boost circuits. The following part number series are typical Coilmaster

inductors used in buck circuits from our customer.

SEP Series: SEP0412, SEP0402, SEP0603, SEP1004

SDC Series: SDC103R, SDC104R, SDC105R,

SDS Series: SDS1608, SDS0805, SDS5020, SDS5030, SDS6020, SDS6030, SDS73, SDS74, SDS124, SDS125,

SDS127

SDR / SRS Series: SDR54S, SDR75S, SRS74R, SRS105R

SD Series: SDC2D14, SDC3D16, SDC3D18, SDC3D28, SDC4D18, SDC4D22, SDC4D28, SDC5D18, SDC5D28,

SDC5D33, SDC6D28, SDC6D38, SDC8D38, SDC8D43,

For more information go to:

https://www.coilmaster.com.tw/s/2/product-c66906/Shielded-Power-Inductor.html



Single Ended Primary Inductance Converter (SEPIC) Circuit

The SEPIC circuit is a popular Buck-Boost topology that allows the output voltage to be higher or lower than the

input voltage. The SEPIC output polarity is the same as the input.

SEPIC circuits generally need the two identical inductors. It could be 2pcs of individual inductors or a one dual-winding inductor.

Dual winding inductors are preferred due to it's bifilar wound. Because this technique uses less space, reduces

leakage inductance, and increases the coupling of the windings which results in overall increased circuit

efficiency.
. Most important one, the dual winding inductors is cost effective solution.
SDSBQ Series: SDS73BQ, SDS74BQ, SDS125BQ, SDS127BQ, SDS129BQ



Boost Circuits

Boost circuits are power converters with an output DC voltage greater than its input DC voltage.

Boost circuits generally require one inductor. The following part number series are typical Coilmaster inductors

used in boost circuits.

SEP Series: SEP0412, SEP0402, SEP0603, SEP1004

SDC Series: SDC103R, SDC104R, SDC105R,

SDS Series: SDS1608, SDS0805, SDS5020, SDS5030, SDS6020, SDS6030, SDS73, SDS74, SDS124, SDS125,

SDS127

SDR / SRS Series: SDR54S, SDR75S, SRS74R, SRS105R

SD Series: SDC2D14, SDC3D16, SDC3D18, SDC3D28, SDC4D18, SDC4D22, SDC4D28, SDC5D18, SDC5D28,

SDC5D33, SDC6D28, SDC6D38, SDC8D38, SDC8D43,

For more information go to:

https://www.coilmaster.com.tw/s/2/product-c66906/Shielded-Power-Inductor.html



Flyback Circuits

The Flyback transformer have several critical factor, isolation, energy storage, and voltage scaling. The Flyback allows

multiple output voltages as well as can provide plus and minus outputs by using tapped windings.

Flyback circuits require a custom-designed flyback transformer. Coilmaster designs and makes custom and semi-custom transformers to match flyback circuit design requirements.



Forward Circuits

The Forward transformer only provides isolation and voltage scaling. The Forward allows multiple output

voltages as well as can provide plus and minus outputs by using tapped windings. A separate energy storage

device (inductor) is needed.

Forward circuits require a custom-designed forward transformer and an output inductor Coilmaster

designs and makes custom and semi-custom transformers to match forward circuit design

requirements as well as have a number of output inductor offerings.

What kind of affect does the DC resistance have on the characteristics of the power supply?
This refers to the resistance value when the inductor is measured by DC. When the resistance value is larger, the power loss will increase.

How does the DC superimposing characteristics affect the characteristics of the power supply?
The DC superimposing characteristic is the inductance value generally decreases due to the magnetic saturation of the ferrite when DC is applied. Once this DC superimposing characteristic deteriorates, the ripple voltage which is a characteristic of the power supply may increase.

What is the limit of the storage period?
Some series of product must use within 6 months of delivery, and other series may up to 12 months of delivery. Please check with our sales department about the storage period for the part you wish to purchase. And if the products have been stored beyond the specified period, carefully check the soldering condition before use.

What is the storage method?
The following storage information is for the storage method(environment) of general inductors.
(1) Store the inductors in a room where the temperature is between -10 to +40 ºC, relative humidity of 15 to 85 %, and there is no sudden change in the temperature and humidity.
If inductors are stored where there are chemicals in the atmosphere, such as sulfur and chlorine gas, the electrodes will oxidize and defective soldering may occur, or cause corrosion and etc. of the wire winding portion of the chip inductors.
(2) Do not store inductors in a bulk state only in tape and reel. If inductors are stored in bulk, the inductors themselves, or chip inductors and other products may make contact. This may result in the chipping of the cores or wire breakage due to friction between products.
(3) Do not store products directly on a floor, should place the products on pallets to prevent effects from moisture and particles.
(4) Do not store products in locations where there is direct sunlight, or heat and vibrations are applied.

The wire wound inductor disconnected, what is the cause?
In order to focus on the performance, there are portions of the wire wound inductor which are coated with resin. Even if there is coating, the lead lines are not protected. For this reason, pay sufficient attention when handling the components, and be careful not to scratch the components with pincettes or etc. Also, if the board mounted with components is stored in a stack, the corner of the boards will make contact with the components of the other boards and cause wire breakage.

What is operating temperature range?
The temperature range refers allowable range of the ambient temperature when using an inductor. The self-heating of the inductor should take into consideration as well.

What can happen when a product is used beyond the operating temperature range?
When a product is used beyond the operating temperature range, the following failures can be considered.
(1) Case where the coil is disconnected and results in an open mode
(2) Case where the insulation between the coils could not be maintained, and the inductance deteriorates
*Please be careful "not" to use a product beyond the operating temperature range.

What is an inductor for a choke? Is it available to use for a power supply?
Generally, the inductor is utilized to suppress high frequency noise and stabilize the current in power supply lines. The power inductor for a choke can also be used for power supplies. Please contact our sales department for more information or suggestions.

What is a magnetic shield? If there is no magnetic shield, what happens to the ceramic?
The magnetic shield is to block the unnecessary magnetism. This shield blocks the external magnetism to the inductor, and also prevents magnetism inside the inductor from having any external affects. Coilmaster provide different types of power inductors consist of magnetic shields.
For inductors without a magnetic shield, please confirm whether the external magnetism particularly affects the inductor characteristics, or whether the magnetism of the component has any external affects.

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