Views:2112 Author:Site Editor Publish Time: 2020-04-05 Origin:Site
Power supply is an important part of circuit, and the stability of power supply determines the stability of circuit to a great extent. Linear power supply and switching power supply are two common power sources, which are very different in principle, and the difference in principle determines the difference in the application of the two.
The principle of linear power supply: After the transformer is lowered, the electricity becomes low voltage AC, then through rectifier and filter into DC, and finally through the voltage regulator circuit into output stable low voltage DC and the adjusting elements in the circuit work in the linear state.
The principle of switching power supply: The switching power supply can rectify the AC directly into DC at the input end, and then control the on-off of the current with the switch tube under the action of the high frequency oscillation circuit to form the high frequency pulse current. Finally, with the help of high frequency transformer, the switching power supply outputs stable low voltage DC.
The regulator of the switching power supply operates in the saturated state and cut-off state, so it has low heat and high efficiency (over 75%). At the same time, the switching power supply does not require transformers in large volume. However, large ripple will be superimposed on the DC output of the switching power supply, and the ripple can be reduced by connecting the voltage regulator diodes at the output end. In addition, because the switch tube will produce a large spike pulse interference, it is also necessary to connect magnetic beads in series in the circuit to reduce the interference. The linear power supply has no above defects, and the ripple it produces can be very small or even no ripple. The main terminals used in switching power supply are barrier type terminals, such as 9500, 825, 611 and so on.
The advantages of linear power supply are relatively simple structure, small output ripple and low high frequency interference. Because of its simple structure, linear power supply is very convenient in maintenance. The difficulty of repairing a linear power supply is often far lower than that of repairing a switching power supply, and the success rate of maintenance of linear power supply is also much higher than that of switching power supply. The regulator of the linear power supply operates in the amplification state, so it has high heat and low efficiency (about 35%). The Linear power supply often requires heat sink in large volume and power transformer in large volume. The main terminals used in linear power supply are XH2.54 terminals and so on.
The switching power supply is suitable for use in places with high requirements for power efficiency and installation space. The linear power supply is suitable for use in places where electromagnetic interference and power purity are required (e.g. leakage detection of capacitance).