Difference between switch mode power supply and transformer
First of all, the switching power supply is DC - DC, the transformer is AC - AC; Secondly, the switching power supply works at a higher frequency (generally in the dozens of kilohertz), while the transformer has a high-frequency, there are also low-frequency, switching power supply used in the pulse transformer is a high-frequency transformer, the iron core is a ferrite such as the core, the volume is small, high efficiency (the higher the frequency of the high efficiency will be the higher), said that transformer we first think of the Is the industrial frequency transformer, its operating frequency of 50 hertz, belongs to the low-frequency transformer, the core must be stacked up with soft magnetic material silicon steel sheet (to prevent eddy currents produce joule heat); again: the two functional categories are not the same, switching mode power supply contains a pulse transformer, but also contains a rectifier part of the upper and lower ends, regardless of the frequency band of the transformer is just a voltage converter, there is no rectifier function;
If we talk about cases, let's talk about the power supply circuit of the TV set! The power supply part of the colour TV is a typical switching power supply; in the past, the power supply circuit part of the black-and-white TV set is the industrial frequency transformer plus the rectifier, filter and voltage regulator circuit composition. Colour TV power supply is 220V AC power directly rectified to 300V DC, and then cut by the switching transistor into high-frequency pulse, and then through the pulse core transformer step-down, and then rectify the filter output low-voltage DC (it is the whole process of regulating the problem of the solution); the sum of these processes is said to be affordable switching power supply. The black and white TV sets in the industrial frequency transformer old brother a representative of the transformer you said, it does not contain rectifier filter circuit. So the two do not have the same functional scope.
