stands for switched mode power supply. It is a device in which energy conversion is provided by power semiconductors switching "on" and "off" with high frequency. Let's explain this in more details. We know that the electric energy is not normally used in the form in which it was produced or distributed. Practically all electronic systems require some form of energy conversion. A device that transfers electric energy from a given source to a given load using electronic circuits is referred to as power supply
. Of course, it does not really supply power, it just converts it, so "converter
" is a more accurate term for such a device. A typical application of a DC power supply unit (PSU) is to convert utility AC voltage into a set of regulated DC voltages required for electronic equipment.
The energy flow in a modern PSU is controlled with power semiconductors, which can operate in different modes. In legacy systems they operated in linear mode. Nowadays most PSUs are SMPS in which semiconductors are continuously switching on and off with high frequency. They offer greater efficiency compared with linear supplies because they can control energy flow with low losses: when a switch is "on", it has low voltage drop and will pass any current imposed on it; when it is "off", it blocks the flow of current. As the result, in such a switch the power dissipation which is the product of voltage and current, can be relatively low in both states. Switching mode units are also smaller in size and lighter in weight due to the reduced size of passive components and lower heat generation. The industry trend toward miniaturization, advancements in semiconductor technology, as well as various energy efficiency regulations have made "switcher" the dominant type of PSU across practically the full spectrum of applications. Most PSU manufactured today for AC input applications also include a PFC front end.
In general, SMPS converters can be classified into four types according to the form of input and output voltages: AC to DC (also called off-line DC power supply), DC to DC (voltage or current converter), AC to AC (frequency changer or cycloconverter), and DC to AC (inverter
).The field of engineering that deals with the design and analysis of power conversion circuits and devices is called power electronics
, although power supply design is a true cross-disciplinary task. It involves the circuit, magnetics, thermal management, control and compliance issues. This site is SMPS/power electronics information guide. Here you will find a tutorial, tools, reviews, schematics, and other free online resources on all aspects of switching power supply design and selection, information on other energy conversion devices, as well as basic electrical engineering
reference and electronic formulas