Everything You Need To Know About Resistor EMI Filter

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Electromagnetic interference is a major issue in most electronic applications. It is likely to interfere with the transmission of signals and the flow of current. Think of devices such as phones computers and radios. These are just some of the electronic devices known to generate electromagnetic waves within their systems. Different devices have been invented to deal with this problem, including the resistor EMI filter.

The resistor EMI filter is designed to minimize electromagnetic interference in different devices. As the name suggests, its main component is a resistor though it also features a capacitor in its system. In this article, we are going to discuss the basics and details of resistor EMI filters.

Resistor EMI Filter Definition

A resistor EMI filter is an electrical component whose core purpose is to reduce and even cut off the electromagnetic interference  (EMI) that is generated by a target electronic device. The filter comprises of resistors and capacitors which are arranged in a particular order to maximize the effectiveness of the filtering process.

EMI resistor filters are used in a wide range of applications ranging from small electronic devices such as mobile phones to home appliances such as electric cookers, and even to industrial machinery.

The working principle of a resistor EMI

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The working mechanism of a resistor EMI entails generating a low-impedance path for the high-frequency noise to move to the ground. At the same time, the filter provides a high-impedance path for electromagnetic noise.

To accomplish this goal, a resistor filter EMI utilizes a combination of resistors, inductors, and capacitors for a network and is arranged in a specific configuration.

The main function of resistors in this network is to minimize the effects of high-frequency signals. In doing so, they are able to cut down the amplitude of the noise. This function is quite vital as in most cases the high-frequency signals are responsible for generating EMI signals.

The capacitors, in the resistor EMI filter supply a low-impedance path through which the high-frequency noise can flow to the ground. This means that the noise will be dissipated to the ground in the safest way.

The main function of inductors in the filter is to prevent high-frequency noise from getting back to the circuit.

Whenever electromagnetic signals enter the filter, they are blocked by the conductors. The remaining high-signal frequency will be shunted to the ground by the capacitors hence protecting the main circuit.

The result of the filtering job is a clear signal that guarantees the overall performance of the system. Also, the main power signal will be devoid of noise interference.

Despite this working mechanism, the performance of a resistor EMI filter is not always smooth or constant. There are different factors that can affect performance. One of them is the design of the filter.

A well-designed EMI filter will deliver optimum performance when it comes to filtering the EMI signals and other unwanted signals. You cannot get such a level of performance from a poorly designed filter.

You should also consider the filtering capacity of the filter. It should match the frequency of the signals that are being filtered. Otherwise, no matter how good the filter may be, it will not be able to deliver the desired filtering performance.

Difference between active vs passive EMI filters

Electromagnetic interference noise filters are divided into two main categories: active EMI filters and passive EMI filters. What is the difference between these two types?

Active  EMI filters are designed to work with both active and passive electronic components to minimize the frequency of the noise signals so as to achieve optimum filtering. A typical active EMI filter will detect the noise current coming from a power source such as a transformer and inject it back into the circuit in the form of a compensation current.

Active EMI filters are mainly found on low-level circuits and tend to have lower bandwidth than their passive EMI filters. Examples of active EMI filters include voltage sensing voltage cancellation (VSVC) and current sensing current cancellation(CSCC).

Passive filters comprise components such as resistors, inductors and capacitors. They are directly connected to the circuits in order to achieve a specific level of filtering. They are quite effective both for low and high-frequency applications. This explains why they can be used on small devices as well as large electronic machines. Passive filters make it easy to achieve noise attenuation without incurring too much cost.

So, which type of EMI filter is perfect for my application?

To get the answer, you will need to analyze the pros and cons of both EMI filter types. Overall, the passive EMI filter is better than the active filter in terms of strength, capacity, and reliability.

It is also versatile implying that it can easily serve different types of applications. If your device is expected to generate strong EMI signals, then you will be safer with a passive EMI filter. From this comparison, it is clear that a resistor EMI filter should be in your bucket list.

Applications of the resistor EMI filter

Resistor EMI filters are used in the following application areas:

• In energy management systems
• Aerospace systems
• Military installations
• Medical imaging devices
• Industrial automation systems
• Computers
• Mobile phones
• Automotive battery chargers
• MRI rooms
• Exercise equipment

Many other modern devices are embedded with the EMI filters in their systems. As long as the device generates electromagnetic signals, it will be a smart idea to get this filter.

Conclusion

Well, that is all the essentials that you should know about resistor EMI filters. They are part and parcel of modern electric devices and appliances thanks to their ability to effectively block electromagnetic interference noise.

Are you building a device whose operation will involve the generation of the EMI? You know the type of filter to buy. Or, are you in the business of importing EMI filters from China in bulk? Ensure you get them from the best electronic components suppliers. However, you should still ensure that the resistor EMI filter that you want to buy matches your application needs in terms of power and signal bandwidth.

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