What is the difference between linear power supply and switching power supply?
The adjustment tube of a linear power supply operates in an amplifying state, resulting in high heat generation and low efficiency (around 35%). It requires a large volume of heat dissipation fins and also a large volume of power frequency transformer. When multiple sets of voltage outputs need to be produced, 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 (50mVat5Vtypical) 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 caused 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, 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 transformer used in switch mode power supplies may be difficult to wind.
Switching power supplies and linear power supplies have completely different internal structures. As the name suggests, switching power supplies have switching actions, which use variable duty cycles or frequency conversion methods to achieve different voltages. The implementation is more complex, and the biggest advantage is high efficiency, generally above 90%. The disadvantage is that there is high ripple and switching noise, which is suitable for situations where ripple and noise requirements are not high; Linear power supplies, on the other hand, do not have switching actions and belong to continuous analog control. Their internal structure is relatively simple, and the chip area is also small, resulting in lower costs. The advantages are low cost, low noise, and the biggest disadvantage is low efficiency. They each have their own shortcomings and complement each other in application!
