The adjustment tube of the linear power supply | regulator works in an amplifying state, resulting in high heat generation and low efficiency (around 35%). It requires a large volume of heat sink and also a large volume of power frequency transformer. When multiple sets of voltage outputs need to be made, the transformer will be even larger.

The adjustment tube of the switching power supply operates in saturation and cutoff states, resulting in low heat generation, high efficiency (over 75%), and the elimination of large transformers. However, a large ripple (50mvat 5vo output typical) will be superimposed on the DC output of the switching power supply, which can be improved by connecting a voltage regulator diode in parallel at the output end. In addition, due to the significant spike pulse interference generated by the operation of the switching transistor, it is also necessary to connect magnetic beads in series in the circuit to improve it. Relatively speaking, linear power supplies do not have the above defects, and their ripple can be made very small (below 5mv).

For places where power efficiency and installation volume are required, switch mode power supplies are preferred. For places where electromagnetic interference and power purity are required (such as capacitor leakage detection), linear power supplies are often used. In addition, when isolation is required in the circuit, nowadays most DC-DC is 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 transformer used in switch mode power supplies may be difficult to wind.