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What is a Power supply?
A power supply is a device which converts alternating current into direct current. Most electronic devices require a stable, pure, consistent energy source to function correctly. These have many names (and the name varies depending on the sector/environment). They are also called rectifiers, transformers, or converters,... These are used in an interchangeable fashion (although this is not always correct).
The increase in electronic products has driven the growth and development of power supplies.
Linear power supplies
The first power supplies were linear. A transformer which reduced an input voltage of 220 VAC to another voltage, followed by a diode bridge and a filter of some kind to stabilise the output.
One of the problems with linear power supplies is their considerable size, which causes the dissipation of a large part of the energy as heat. Thus the lifetime of nearby or incorporated electronic components is reduced. Moreover, the output voltage varies depending on the load. They are still used as they generate less ripple and noise. In addition, given that they have little electronics, they have higher immunity to electromagnetic radiation.
We stated that all linear power supplies tend to be heavy and have low efficiency, but with respect to what exactly? Space race requirements for the reduction of weight and consumption in all electronic components resulted in the development of the first switch mode power supplies. The system basically consists in transferring energy in a controlled manner between the primary and secondary circuits. Thus, in the forties NASA tried out switch mode systems for the first time.
At first the technology was expensive and widely unknown. Gradually the miniaturisation of the components and their fall in price has seen switch mode power supplies become more accessible, offering greater stability, safety, and efficiency at a price similar to that of linear power supplies.
The entry into force of the EN 60555-2 regulations in 2001 concerning Power Factor Correction brought about new developments. The main motivation behind the introduction of this norm was the following: due to the manner in which switch mode power supplies consume energy they tend to distort the electrical line, which can affect the operation of other electronic devices which are connected. This standard was an attempt to improve the quality of the electrical flow. Power supplies with PFC (Power Factor Correction) reduce harmonics re-injected into the mains supply using an active filter which corrects the input wave strength converting it into a sinusoidal wave in phase with the voltage.
And what else?
And this continues evolving. If you think that it has all been done, then the next few years may hold a number of surprises. Electronics are so important in our lives that we cannot do without them. A day at home or in the office without electricity practically paralyses our activities. For this reason redundant systems and failure detection systems are evolving rapidly. This means that we now use two power supplies where before just one was used. If one fails then we continue to use the other (redundant system). In addition, power supplies will be capable of detecting possible internal problems or the approaching end of their lifecycle. These systems are still too expensive for many, but as demand grows and consequently the number of units produced increases, there will be more economical solutions for redundant power supply systems.
What should we look for in a switch mode power supply?
It is important that they have high efficiency. This reduces consumption, dissipated heat and increases the lifetime of our entire system.
We should also remember to determine the correct power supply for our system, anticipating the worst possible conditions. The equipment should be protected from all possible problems. If something can go wrong then it will go wrong. Murphy's law also applies to our daily life. Short-circuits, overloads, excess temperatures, electromagnetic emissions, radiated interference, conducted interference, harmonics, variations in input voltage etc., are all potential enemies threatening our equipment...and you can be sure to run up against them at some time!
Protect yourself - place yourself in our expert hands; we will find solutions for your every need.