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The Inductor

An Inductor is a passive electrical component consisting of a coil of wire which is designed to take advantage of the relationship between magentism and electricity as a result of an electric current passing through the coil.

In our tutorials about Electromagnetism we saw that when an electrical current flows through a wire conductor, a magnetic flux is developed around that conductor. This affect produces a relationship between the direction of the magnetic flux, which is circulating around the conductor, and the direction of the current flowing through the same conductor. This results in a relationship between current and magnetic flux direction called, “Fleming’s Right Hand Rule”.

But there is also another important property relating to a wound coil that also exists, which is that a secondary voltage is induced into the same coil by the movement of the magnetic flux as it opposes or resists any changes in the electrical current flowing it.

In its most basic form, an Inductor is nothing more than a coil of wire wound around a central core. For most coils the current, ( i ) flowing through the coil produces a magnetic flux, ( NΦ ) around it that is proportional to this flow of electrical current.

An Inductor, also called a choke, is another passive type electrical component consisting of a coil of wire designed to take advantage of this relationship by inducing a magnetic field in itself or within its core as a result of the current flowing through the wire coil. Forming a wire coil into an inductor results in a much stronger magnetic field than one that would be produced by a simple coil of wire.

Inductors are formed with wire tightly wrapped around a solid central core which can be either a straight cylindrical rod or a continuous loop or ring to concentrate their magnetic flux.

The current, i that flows through an inductor produces a magnetic flux that is proportional to it. But unlike a Capacitor which oppose a change of voltage across their plates, an inductor opposes the rate of change of current flowing through it due to the build up of self-induced energy within its magnetic field.

In other words, inductors resist or oppose changes of current but will easily pass a steady state DC current. This ability of an inductor to resist changes in current and which also relates current, i with its magnetic flux linkage, NΦ as a constant of proportionality is called Inductance which is given the symbol L with units of Henry, (H) after Joseph Henry.Because the Henry is a relatively large unit of inductance in its own right, for the smaller inductors sub-units of the Henry are used to denote its value.

Power inductor characteristics

There are complex trade-offs that engineers need to understand regarding power inductors’ characteristics and the parameters of how they are used.

This difficulty originates from the many characteristics of power inductors and their applications. These may include factors such as temperature and current magnitude.

To illustrate some of these factors, the inductance property of power inductors causes a decrease of inductance as the current increases. This is known as the DC superimposition characteristic. Temperature increases that result from a rise of current, affect changes in inductor core magnetic permeability and saturation magnetic flux density. Noise characteristics is also affected by the magnetic shield structure. DC resistance can also change with the same inductance value depending on the thickness and number of windings. This may cause affect how heat is generated.

Power inductors are normally categorized as wire-wound, thin-film and multilayer inductors. This is based on their design and production differences. Manufacturers often utilize magnets, ferrite or other metallic magnets as power inductor cores. Ferrite cores exhibit high inductance and a high magnetic permeability value, whereas metallic magnetic cores exhibit exceptional saturation magnetic flux density. This makes them ideal for larger current applications.

In addition, power inductors work with two main types of ranted currents: allowed current for DC superimposition, and allowed current for temperature rise.

The inductance of the power inductor core will drop when the core becomes magnetically saturated.

The maximum recommended current that should eb transmitted without reaching magnetic saturation is the same as the allowed current for DC superimposition. The current that is defined by the heat generation of the electrical resistance in the inductor’s windings is the allowed current for temperature rise. The rated current for the inductor is should be equal or less that these two types of allowed currents. For example, there may be a drop of 40 percent from the initial inductance value and a rise of temperature of 40℃ due to self-heat generation.

Each of these parameters are co-dependent with each other and very complex, making each power inductor unique and uniquely suited for different applications. Consequently, the selection of the right inductor for each application is critical to it success.

In addition to the application in which they will be placed, the size, cost and efficiency of DC-DC conversion should be considered when selecting the most appropriate power inductors for any application.

Advantages and Disadvantages of Common Mode Chokes

Current compensated chokes and common mode chokes are different terminologies for the same thing. One point to consider when talking about CMC’s is the economic advantages and disadvantages.

Disadvantages

What is the advantage of using common mode chokes? These parts suppress unwanted signal interference, or noise. But what are the disadvantages of using common mode chokes over something else, such as a chip bead?

1.More expensive than SMD ferrite (Chip Beads)

2.Larger size (more board space than ferrite)

Common mode chokes are more customized so there are various versions that you can have with common mode chokes. For example, you can wind a different amount of turns when you build them up and you can customize it to reduce (or knock down) the specific unwanted frequency ranges.

So, to customize a winding is a little bit more advantageous, as opposed to chip beads or any kind of catalog inductors where you are only able to have the single winding and a certain differential mode suppression levels. However, that versatility makes common mode chokes more expensive than alternatives. It's also larger, so that's a disadvantage as well

Advantages

There are, of course, technical advantages. If you use a common mode choke, it can attenuate the unwanted high frequency signals, while you would get better efficiency for knocking down the unwanted noise, and allowing your required signal to pass.

1.Better efficiency

2.High current with high inductance value

3.Only solution for some high speed signal

Also common mode chokes can operate at a high current with high inductance values. Because you're using specifically designed part, a customized common mode choke, you can go to heavier gauge wire, allowing it to run a higher current. Since whatever is going out on the line and returning on the neutral you now have gotten cross cancellation of the saturation current, you should not need to worry about the parts saturating. Instead, now pay attention to the heating of the part, the current flowing through the wire will cause the part to heat, but there is no saturation current in the common mode choke, (if operated correctly). With common mode chokes you can get higher current values than just simple chip beads or single wound inductance, because they are larger parts and have heavier wire size used in the construction.

Another technical advantage is for high speed signals (USB, CAN bus, etc). Common mode chokes are the only solution. Because you don't want to knock down your transmission signal (meaning distort your transmission signal), you only want to knock down the unwanted noise as you go.

The Basics of Class D Amplifiers

While there are a variety of modulator topologies used in modern Class D amplifiers, the most basic topology utilizes pulse-width modulation (PWM) with a triangle-wave (or sawtooth) oscillator. It consists of a pulse-width modulator, two output MOSFETs, and an external lowpass filter (LF and CF) to recover the amplified audio signal. The p-channel and n-channel MOSFETs operate as current-steering switches by alternately connecting the output node to VDD and ground. Because the output transistors switch the output to either VDD or ground, the resulting output of a Class D amplifier is a high-frequency square wave. The switching frequency (fSW) for most Class D amplifiers is typically between 250kHz to 1.5MHz. The output square wave is pulse-width modulated by the input audio signal. PWM is accomplished by comparing the input audio signal to an internally generated triangle-wave (or sawtooth) oscillator. This type of modulation is also often referred to as "natural sampling" where the triangle-wave oscillator acts as the sampling clock. The resulting duty cycle of the square wave is proportional to the level of the input signal. When no input signal is present, the duty cycle of the output waveform is equal to 50%.

Most audio system design engineers are well aware of the power-efficiency advantages of Class D amplifiers over linear audio-amplifier classes such as Class A, B, and AB. In linear amplifiers such as Class AB, significant amounts of power are lost due to biasing elements and the linear operation of the output transistors. Because the transistors of a Class D amplifier are simply used as switches to steer current through the load, minimal power is lost due to the output stage. Any power losses associated with a Class D amplifier are primarily attributed to output transistor on-resistances, switching losses, and quiescent current overhead. Most power lost in an amplifier is dissipated as heat. Because heatsink requirements can be greatly reduced or eliminated in Class D Amplifier Inductors, they are ideal for compact high-power applications.

In the past, the power-efficiency advantage of classical PWM-based Class D amplifiers has been overshadowed by external filter component cost, EMI/EMC compliance, and poor THD+N performance when compared to linear amplifiers. However, most current-generation Class D amplifiers utilize advanced modulation and feedback techniques to mitigate these issues.

GaN Choke for High Frequency Switching Mode Power Supply

With low power loss, high power factor correction and a small magnetic leakage, GaN Power Supply Choke plays an important role in the circuit of GaN Power Devices.

As a wide band-gap (WBG) semiconductor material, Gallium Nitride (GaN) is like a transistor, which shows crucial advantages over silicon in key areas. By using the inductor of this material, it increases efficiency of power supply production, while decreasing the size and weight of electronic devices. GaN Power Supply Choke is applied in GaN devices such as GaN-based RF power amplifiers.

We apply toroidal core winding machine to enwind the enamelled wire around the core. When it comes to soldering process, several sets of soldering machines manage the lead-free soldering compliant with RoHS and REACH regulations. We have fully automatic soldering machine, semi-automatic soldering machine, and manual soldering machine available to feed the need of production.

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