The difference between linear power supply and switching power supply
The adjustment tube of the linear power supply works in the enlarged state, so it generates a lot of heat and has low efficiency (about 35%). It needs to add a bulky heat sink, and also needs a large-scale power frequency transformer. When making multiple sets of voltage output The transformer will be even larger.
The adjustment tube of the switching power supply works in the saturated and cut-off state, so the calorific value is small, the efficiency is high (over 75%) and the large-volume transformer is saved. However, a large ripple (50mVat5Voutputtypical) will be superimposed on the DC output of the switching power supply, which can be improved by connecting a Zener diode in parallel at the output end. In addition, because the switching tube will produce a large spike interference, it also needs to be connected in series in the circuit. Even magnetic beads to improve. Relatively speaking, the linear power supply does not have the above defects, and its ripple can be made very small (below 5mV).
It is better to use switching power supply where there are requirements for power supply efficiency and installation volume, and for places where there are requirements for electromagnetic interference and power supply purity (such as capacitance leakage detection), linear power supply is mostly used. In addition, when isolation is required in the circuit, DC-DC is now mostly used to supply power to the isolated part (DC-DC is a switching power supply in terms of its working principle). Also, the high-frequency transformers used in switching power supplies may be cumbersome to wind.
Switching power supply and linear power supply are completely different in internal structure. As the name suggests, switching power supply has switching action. It uses variable duty ratio or frequency conversion to achieve different voltages. The realization is more complicated. The biggest advantage is high efficiency. More than 90%, the disadvantage is that the text wave and switching noise are relatively large, which is suitable for occasions that do not require high text wave and noise; while the linear power supply has no switching action, which belongs to continuous analog control, the internal structure is relatively simple, and the chip area is also small. The cost is low, the advantages are low cost, low text wave noise, and the biggest disadvantage is low efficiency. They have their own shortcomings and complement each other in application!
