The purpose of the power supply and its function

Published: 9 June 2022

The purpose of the power supply and its function

The purpose of the power supply is to convert the power from the DC or AC mains (110 V in North America, 220-240 V in most of Europe) to the DC voltage level required by the equipment.  

A switch mode power supply can have various topologies depending on the design, and output requirements. The most common types of power converters are regulated, which use some form of feedback system to maintain a constant output voltage level even if the input voltage varies. Another common feature is isolation, this isolated the input from the output often through a transformer or coupled inductor. However, not all applications require these features, additionally they generally increase the size and cost of the system.  

The function of the power supply is to provide power at the required voltage level to the system, sometimes this is done by an initial converter providing a DC voltage bus. Then a point of load (PoL) or point of use converter is used to further step down the voltage for the load.  

Power converters also containing filtering elements, these are used to smooth out the energy coming into the converter and coming out. This increases the losses but protects the supply, components, and equipment, additionally some equipment behaves unpredictably without smooth power.  

For some power supplies, natural cooling through convection or conduction is enough. However, some power supplies require forced cooling. Forced air cooling is the common type of forced cooling, a fan is used to circulate air through the power supply, and it is usually located on the power supply itself, but a system fan can also be used.  

Power supplies are rated for the maximum amount of power they can deliver, this can change depending on the input and output voltages. Some converters are rated for the power handling capability when naturally cooled, and separately for forced air cooled. It is important to make sure that the power converter can deliver the power required by the load.  

Another important specification of the power supply is the efficiency. The efficiency is a measure of how much power is converted to the required DC power. Most of the power lost is in the form of heat, typically this is due to conduction and switching losses.

A power converter is a key component is any electrical system because it provides power to all other components. Without a working power supply, the application will not function. It is important to choose a power supply that can deliver enough current to meet the needs of all the components. Additionally, it is important to choose a power supply that is efficient to minimise the amount of heat generated and complies with any EMC/EMI and safety requirements.

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