The difference between SMPS and transformer

The difference between SMPS and transformer

To clarify what is power switch: switch power supply is relatively linear power supply,linear power supply is the use of linear region of power semiconductor devices, by adjusting the linear impedance to adjust the output end; and the switching power supply is the use of power semiconductor devices of the saturated zone by adjustinghis opening time or frequency to achieve the output adjustment objective.

SMPS’s advantages :

1, high efficiency, small size. Due to the voltage control switch power supply is the use of the saturated zone of power semiconductor devices by adjusting his opening timeor frequency to achieve, so there is no iron loss and copper loss, components of theloss can be neglected, compared the transformer with high efficiency; because it onlyelement device and circuit board, so the volume is small, weight is light.

2, a wide range of input voltage. General can reach 160V-270.

Its drawbacks:

1, look at the small switching power supply, the power and the magnetic core transformer and control method, electromagnetic interference, ripple coefficient. In particular, audio, video category, is very sensitive to electromagnetic interference, in the audio performance for the tone impure thick, there may be the sizzle; as shown in the video, ripple image may be small, not exquisite.

2, the design of complex, inconvenient maintenance repair. The more often the possibility of complex equipment problems is larger, and the switch power supply when problems arise, the general non professionals can not repair, find someone else torepair, the cost is too high, not abandoned.

3, small size are the advantages of the switching power supply, but the design is notgood has its disadvantages. In the pursuit of a smaller, a lot of components are squeezed into a small shell, the heat is not good, I will appear the phenomenon ofcasing deformation.


1, linear look bulky, power depends entirely on the transformer and the adjusting tube, efficiency is low but does not introduce additional interference, that is to say little electromagnetic interference, ripple coefficient is very low, is negligible. Formonitoring, no better than this advantage, the quality of the relationship of image quality and power is very big. Especially for the analog signals of small amplitude(audio source and video source) on the power requirements are very high, so somehave a fever acoustics in power are used instead of switching power supplytransformer.

2, the high rate of voltage, simple design, convenient maintenance repair, failure,slightly understand electronic technicians to repair, repair cost much less than theswitching power supply.

3, the anti lightning performance. Because the transformer structure is the two coil and iron core, add in the voltage across the coil not mutation, it has strong inhibitionon the instantaneous high pressure. So in a lightning strike accident, transformersurvived, and switching power supply without exception burned.

The disadvantage:

1, low efficiency. The transformer is an “electric conversion — Magnetic — power” of the process, can not avoid the existence of iron loss and copper loss, low efficiency.

2, the input range is narrow. Generally only between 200V – 240V, less than the rangeof output voltage, not, larger than this range, the transformer may be burned. Thevoltage range is enough for most occasions, need not consider too much. Moreoverthe volume of the transformer is switching power supply large, bulky.