Transformer as an element of household power supply units

While selecting a power supply unit, a consumer must often choose between a power supply unit and transformer. However, good choice is not a matter of buyer’s intuition, but depends on the knowledge regarding a given device and its power supply method. To make things easier for you, we describe power supply units and indicate the basic difference between power supply units and transformers.


How do the electric appliances we use every day work?

The majority of electric equipment used in our everyday lives and industry must be supplied with direct current (DC), which is not supplied from the mains. This requires providing a device which transforms the alternating current (AC) supplied from a socket into direct current of the required voltage value. A power supply unit is such a device.

While considering this topic, one should ask how it is possible to transform AC into DC and at what stage the voltage value is lowered. Shortly speaking, the answer to this question lies in the method of operation of a transformer, i.e. one of the most elementary components of a power supply unit. A transformer comprises a steel core and two (primary and secondary) windings. The primary winding is supplied with input voltage which, through the core, is directed towards the secondary winding in a form of a magnetic stream, which in turn results in the phenomenon called induction. The difference between the number of winding turns in the primary and secondary windings determines the output voltage value. Thus the transformer determines the output voltage value and is used to adjust it. The current frequency and type remain unchanged. Unchangeable frequency is desirable, however, the current type must be transformed. In order to rectify AC in power supply units, rectifiers with a filtering system and, if necessary, constant-voltage regulators are used. Therefore, similarly to a transformer, a power supply unit is responsible for lowering the input voltage value and, moreover, for stabilising it. Transformer as an element of household power supply units

Power supply unit types

Due to their specifications, power supply units can be divided into two main types:

  • linear power supply units whose design is based on transformer operation - hence the other name, i.e. transformer power supply units. In their case, the simple design does not translate into low weight. Moreover, their sizes are relatively large. These power supply units are used for low output voltage values, i.e. 5-25 V;
  • switch-mode power supply units operated by a voltage converter. This solution makes it possible to use much smaller transformers, which results in the lower weight and smaller size of power supply units. Nowadays, this solution is most commonly used to supply electronic equipment operated by the mains voltage.
    • computer power supply units are dedicated products for a specific application. Even though they are switch-mode power supply units, their design is adjusted to computer equipment operation characteristics. Using the TME website, users are able to filter products to find those meeting their individual requirements. The range of products on offer includes switch-mode power supply units, computer power supply units, linear power supply units and a large number of industrial power supply units from numerous manufacturers, where MEAN WELL power supply units constitute the largest group.


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