Electricity plays a fundamental role in our daily lives, allowing us to charge smartphones or power industrial machinery. With so many devices reliant on electricity it is important that they can manage this power efficiently, but what makes this possible? One solution that we are going to look at is ferrite. In this blog series ‘Ferrite for Beginners’ we will explore the world of ferrite – starting here by understanding why ferrite is used in the first place.
Linear vs Switching Power Supplies
To understand why ferrite is used within electronics, it can be useful to start by looking at power supplies, which help to bring electronic devices or circuits to life by providing them with the right type and amount of power. The two that we will be discussing are ‘linear power supplies’ and ‘switching power supplies’ (also known as switch mode power supplies). These are both types of regulated power supplies, which allow the output voltage of a circuit to be kept at a stable level.
Linear Power Supplies
A linear power supply takes in an AC (Alternating Current) voltage, from a source such as a wall outlet, and uses a transformer to reduce the voltage. It then uses a series of capacitors, diodes, and a regulator to convert this high voltage AC into a lower voltage DC (Direct Current) output.
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Advantages
Simplicity: Linear power supplies have a simpler design, making them easier to understand and troubleshoot.
Less EMI (Electromagnetic Interference): They generally produce less electrical noise, making them suitable for applications where interference can be a concern, like in audio equipment.
Stable Output: Linear power supplies provide a stable and continuous output voltage, which is beneficial for devices that require a consistent and reliable power source.
Disadvantages
Lower Efficiency: Linear power supplies are less efficient compared to switching power supplies. They can waste more energy as heat, especially when converting high voltages to lower ones.
Bulkier and Heavier: Due to the use of transformers for voltage reduction, linear power supplies tend to be bulkier and heavier than switching power supplies.
Limited Voltage Range: Linear power supplies are less suitable for applications requiring a significant reduction in voltage, as they become less efficient and more wasteful when stepping down high voltages.
Switching Power Supplies
Switching power supplies also begin with an AC current which is converted into DC. Whereas linear power supplies use a transformer to reduce voltage, switching power supplies use a high-frequency switching technique. This rapidly switches the DC on and off using electronic switches (typically transistors), generating a high-frequency signal which is then fed into a transformer. These transformers can be much smaller in size compared to those in a linear power supply due to the higher frequency. Once the DC has passed through the transformer, it is smoothed out using capacitors and inductors to remove the high frequency and produce a stable DC output. The output voltage is then continuously monitored and adjusted to maintain a constant output even if there are variations in the input voltage.
Advantages
High Efficiency: Switching power supplies are generally more efficient than linear power supplies. They waste less energy as heat during the voltage conversion process, making them more energy efficient.
Compact and Lightweight: Due to their design without bulky transformers, switching power supplies are smaller and lighter than linear power supplies. This makes them ideal for applications where space and weight are critical factors.
Versatile Voltage Regulation: Switching power supplies can efficiently adjust voltages up or down, making them versatile for various applications with different voltage requirements.
Disadvantages
Complex Design: Switching power supplies have a more complex design involving semiconductors and high-frequency components. This complexity can make them more challenging to design and troubleshoot.
EMI: Switching power supplies can introduce high-frequency switching noise into the system, potentially causing electromagnetic interference. This may require additional filtering and shielding measures.
Higher Cost: The components and technology used in switching power supplies can make them more expensive to manufacture compared to linear power supplies.
Ferrite Core Transformers
Now that you can see the difference between linear and switching power supplies, we can look at where ferrite fits into the equation. Ferrite is commonly used within switching power supplies for the transformer that reduces the voltage. Ferrite works well at high frequencies and has properties that allow power supplies to operate efficiently whilst maintaining a compact design. Here’s how a ferrite core transformer works:
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Ferrite Core
The heart of the transformer is the ferrite core, these are available in different shapes such as “E” cores or “POT” cores and can be purchased in different sizes and materials.
Primary and Secondary Windings
Around the ferrite core, there are two sets of wires called “windings.” The first set is called the “primary winding” – this is where the electricity from the power source flows through. The second set is called the “secondary winding.” This is where the transformed electricity comes out, ready to power your device.
Along with being used for transformers, ferrite is also commonly used in inductors and for minimising EMI. Let’s start by looking at inductors.
Introducing Inductors
Inductors are electrical components designed to store energy in a magnetic field. When an electric current flows through the coil of wire in an inductor, it creates a magnetic field around the coil. A key function of inductors is to resist changes in the flow of an electric current, and this resistance is created due to the energy stored in the magnetic field.
Inductors have several important applications, including:
Energy Storage: Inductors store energy in their magnetic fields, and this stored energy can be released back into the circuit when needed.
Smoothing Signals: Inductors can help smooth out variations in electrical signals, acting like a filter to stabilise the flow of current.
Filtering: Inductors can be used as a filter to allow some frequencies to pass through a circuit whilst blocking other frequencies.
Transformers: Inductors can be used in transformers to help transfer electrical energy between circuits by creating a changing magnetic field.
Whilst there are a few different kinds of inductors, we are going to be looking specifically at two – air core inductors and ferrite core inductors.
Air Core Inductors
An air core inductor is a device that stores electrical energy using coils of wire – they are called ‘air’ cores because there is no solid material at the centre of the coil, unlike some other types of inductors. They rely on the surrounding air to generate the magnetic field when an electric current flows through the coil.
Let’s look at some features of air core inductors:
Size: They tend to be larger in size compared to inductors with magnetic cores. This is because air doesn’t concentrate the magnetic field as effectively as magnetic materials.
Interference: Air core inductors produce less magnetic interference, making them suitable for applications where minimising interference is important, such as in high-frequency circuits or radio-frequency devices.
Applications: Commonly found in applications where size is less critical, and maintaining signal clarity is more important. For example, they might be used in radio antennas.
Ferrite Core Inductors
A ferrite core inductor, on the other hand, uses a coil of wire wound around a core made of ferrite. The reason for using a ferrite core in an inductor is to enhance its performance – it does this by increasing the inductor’s ability to store energy in the magnetic field.
Here are a few reasons why using ferrite is beneficial:
Increased Inductance: The presence of a ferrite core in an inductor increases its inductance. Inductance is a measure of how much energy the inductor can store. So, by using a ferrite core, we can have a more efficient and powerful inductor.
Higher Efficiency: Ferrite cores help in reducing energy losses. When an electric current flows through the wire in the inductor, some energy is lost as heat. Ferrite cores help to minimise these losses, making the inductor more efficient.
Frequency Stability: Ferrite cores are particularly useful at high frequencies. They can maintain their performance better than some other materials, making them suitable for applications like radio frequency (RF) circuits.
Size and Weight Reduction: Ferrite core inductors can often be more compact and lighter than their counterparts without ferrite cores. This is especially important in electronic devices where space and weight are critical factors.
So, in summary, the ferrite core in an inductor improves its ability to store energy, increases efficiency, and can be more suitable for certain applications, especially those involving higher frequencies.
Electromagnetic Interference (EMI)
As mentioned above, we have introduced the concept of Electromagnetic Interference (EMI) which occurs when electronic devices or electrical systems create “noise” or disturbances in the electromagnetic field, affecting the normal operation of other nearby devices. We can break it down like this:
Electromagnetic: This refers to anything related to electricity and magnetism, which are two fundamental forces in nature.
Interference: Imagine you’re trying to listen to your favourite radio station, but there’s a lot of static or noise that makes it hard to hear the music clearly. That interference could be caused by various things, including other electronic devices nearby.
Minimising EMI is crucial to ensure that different devices can work together without causing disruptions. Ferrite has a unique ability to absorb high-frequency EMI, meaning that it can reduce the amount of noise produced and in turn minimise the interference on other devices or systems. This is all well and good, but how do we use ferrite to manage EMI? Let’s look at some common ferrite solutions for reducing EMI.
Ferrite Beads
Ferrite beads are small cylindrical components with a hole in the centre. Placed around cables, they act as filters for high-frequency signals by introducing impedance (opposition to electrical flow), reducing EMI. They are commonly used on power cords and data cables in electronic devices to prevent unwanted signals from causing interference.
Ferrite Cores
Ferrite cores come in various shapes and are versatile components used in inductors, transformers, and cables to enhance inductance. By concentrating and guiding magnetic fields, ferrite cores contribute to efficient energy storage and transfer, leading to a reduction in EMI. Widely used in power supplies, audio equipment, and cables, ferrite cores play a key role in maintaining the integrity of electronic signals and preventing interference.
Ferrite Sleeves (Cable Cores)
Ferrite sleeves, also known as cable cores, are cylindrical devices designed to slide over cables. By absorbing and reducing unwanted noise, ferrite sleeves help to ensure that signals stay contained within the cables, preventing interference with other electronic equipment. Ferrite sleeves are commonly used on power cords, USB cables, and communication cables.
Ferrite Plates and Sheets
Ferrite plates and sheets are used in electronic devices or enclosures to address interference issues. Positioned on the surfaces of electronic devices or enclosures, they serve as barriers against electromagnetic radiation. This allows them to absorb or reflect radiation, reducing the likelihood of interference. Ferrite plates and sheets are frequently used in electronic devices and industrial equipment, contributing to effective EMI shielding and ensuring proper operation.
Ferrite Snap-On Cores
Ferrite snap-on cores (also referred to as clamp-on cores, clip-on cores, and ferrite clamps) are split cores that are easily snapped onto cables, without the need to disconnect them. They introduce impedance to high-frequency signals, reducing EMI without requiring major modifications to cables. Snap-on cores are used for EMI suppression on existing cable installations in computer systems, audio equipment, and electronic devices.
Ferrite Chip Beads
Ferrite chip beads are small, surface mount components used on printed circuit boards (PCBs). Acting as low-pass filters, they allow DC and low-frequency signals while reducing high-frequency noise. Ferrite chip beads are commonly used on PCBs in electronic devices like smartphones and computers for EMI suppression.
Ferrite Balun Cores
Ferrite balun cores are used in balun transformers for impedance matching and EMI suppression in RF circuits. These cores help convert between balanced and unbalanced (hence the name “balun”) signals while reducing common-mode noise (electrical interference that affects both the signal and ground conductors simultaneously). Ferrite balun cores are widely used in RF applications, antennas, and communication systems where impedance matching and EMI suppression are crucial.
Why We Need Ferrite
Efficient management of power is essential when it comes to electronics. As we have discovered, electronic circuits can produce electromagnetic interference (EMI) which may cause disruption to other nearby devices and systems. Ferrite not only helps to reduce this EMI, but also offers a way of managing power efficiently through the use of inductors. We hope that this first blog in our series has given you an insight into why there is a need for ferrite – next we will be looking more in depth at ferrite as a material itself, exploring its origins and the different types available.