Power Supply Unit(PSU)
We collectively name all the devices to supply power to electric/electronic device as power supply unit.
They mean the device to supply power such as generator, battery but they also indicate power converter which includes various device(rectifiers, inverters, power stabilizer, various protective devices, etc) to be suitable to the type of power for loading(direct current, alternating current), voltage, current, power level, stability.
Switched-Mode Power Supply(SMPS)
As a kind of power converter, using semiconductor device such as transistor for power as switch, converting
direct current input voltage into square wave shaped power, controlling through filter, it can obtain direct current input voltage.
At this time, to adjust ON,OFF term of switch, you can control direct current output voltage.
As its operation has DC-DC Conversion function from direct current(input) to direct current(output) as basic option, we can call SMPS as DC-DC converter.
SMPS consists of four major parts.
First, it is input electromagnetic interference(EMI) filter part.
It prevents the noise of AC input line from flowing into PSU, also prevents
the noise inside of PSU from flowing into AC input line.
Second, it is the rectifying section of AC-DC.
It include the process where power already passed electromagnetic
interference filter is converted to temporary DC power before converting to
direct current power required to computer or peripherals.
Third, it is switching converted section of DC-DC.
Converting DC power which converted at AC-DC rectifying section into
square wave voltage by switching semiconductor device, accumulating
energy in inductor, converting them into DC, it can obtain desired output
level such as 5V, 12V, which is the most important process of SMPS.
Fourth, it is output rectification and filter section.
As the last process of SMPS, we remove ripples and noises of DC power
which are generated during switching operation by using low band pass
filter in this process. through this process, we can get DC power such as
5V,12V which are suitable to standard.
For its biggest advantage of SMPS, it can maximize the power-conversion efficiency compared to output/input by utilizing various circuit. But not to prepare noise problems which are generated during switching process, it might affect out external device as well as self-malfunction. Therefore, you should prepare EMI countermeasure in SMPS for sure.
※ power : It contains direct current power and alternating current power.
For direct current power, there is battery for typical example, household power supply for alternating current power..