Electromagnetic compatibility

 

Power supplies generate Electromagnetic Interference inherently, and such interference can have an effect on other components in the circuit and on other electronic equipment in the system’s vicinity.

EMC regulation aims to solve two classes of electromagnetic issues. These are:

·        Emission

·        Immunity

Emissions are electrical noise generated by the power supply or its electronic load. This electrical noise can be transmitted along input and output cables from a source to a victim system causing EMI. Switching power supplies (SMPS), whilst characterised by its high efficiency, the fast-switching frequencies of SMPS’s can generate electronic noise that could affect its operations if not addressed.

A common method to reduce emission is metal shielding, placing noise-generating sources within a ground metal housing. Whilst this method is effective for large projects and systems, products with size constraints and low-cost goals may find the additional material cost and space requirements too high of a price to pay for EMC.

Conducted EMI is noise that is generated by a subcircuit that is transferred to another component or device via cabling or PCB traces. Power supplies can easily conduct interference in this way. 

System designers can use layout optimisations to better manage electromagnetic interference. If power inputs and outputs are separated from each other, line conduction can be minimised. We can also advise on the use of external filtering to better shield your components from noise.

Power supplies can use EMI filters to mitigate conducted EMI. They can be placed at the input or output to filter noise from the mains or output. Different types of EMI filters can be used to solve differing conducted noise. For differential mode conducted EMI filters, the filters are made of either electrolytic or ceramic capacitors to attenuate differential mode current. Whereas with common mode conducted EMI filtering, this is achieved by connecting capacitors between the power input and outputs and ground. If you’re unsure of what filtering is needed for your specific power requirements, we can help designers resolve their unique challenges.

Immunity describes how a component will behave when subjected to a source’s electromagnetic influences in the form of electrical noise. In our everyday environment, there are many sources of EMI that can affect the operation of noise-sensitive systems. Radiated susceptibility to EMI can come from natural sources like lightning and solar radiation but can also come from radio or mobile transmissions or emissions from other power components. For systems with high sensitivity, the EN61204-3 standard exists to give system designers solace that their power component selections can withstand the aforementioned radiated interference alongside immunity to conducted EMI.

If you’re concerned with the electromagnetic compatibility of your power component selections, get in touch with our experts to discuss how best to keep mindful of EMC in your next system.

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