Switching power supply, which is short for high frequency switching power supply, is able to convert AC input from a battery or electronic grid into lower DC volts. They are considered power converters, which transmit power from a source to a load, which can be a personal computer, VCR or other electronic device.
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Switching power supply units provide a regulated output at a different level than the input, and are alternative to linear power supplies, which use transformers to lower the voltage instead of change it from AC to DC. Linear power supplies are ideal for small, low voltage and frequency electronics like cell phones because the higher the voltage or frequency, the larger and heavier the power supply unit. A linear power supply for a PC would be massive and therefore impracticable. For higher voltage electronic devices, linear are replaced with switch mode power supplies because they are able to remain small and portable regardless of the voltage or frequency level. Desktop computers, laptops, cell phone chargers, compact fluorescent lamps, DC powered industrial trucks, large aircrafts, some submarines and television sets all employ switching power supplies to transform the AC input to DC output.
All switching power supply units are classified into four different categories-rectifier, which are AC in, DC out, voltage or current converters, which are DC in DC out, frequency changers or transformers, which are AC in, AC out, and inverters, which are DC in, AC out; AC to DC is by far the most common for switching power supplies. Compared to linear power supplies, they are smaller in size, a lighter weight and generate lower heat because of higher efficiency. However, they are more complex, generate higher amplitude and frequency energy, and must always avoid electromagnetic interference. Switching power supplies rectify and smooth AC voltage using diodes and capacitators. The result is a high voltage DC output that must then be converted by small ferrite transformers or transistors into safe, low voltage with high frequency that is suitable to use on a wide variety of common electronic devices and appliances. The switch that takes place between the input and output is able to control energy flow with low losses. When the switch is on, it has low voltage drop and will pass any current imposed on it; when off, the switch will block the current flow.
