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Why switch power supply? Instead of linear power?

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Why switch power supply? Instead of linear power?
Issue Time:2020-04-21
Why switch power supply? Instead of linear power?



Common power supply and switching power supply are the same voltage adjustment tube, using the feedback principle to stabilize voltage, the difference is that the switching power supply USES the switch tube to adjust, the common power supply generally USES the triode of the linear amplifier to adjust. Comparatively speaking, switching power supply has low energy consumption, wide application range of ac voltage, good ripple coefficient of output dc, and its disadvantage is switch pulse interference.

Ordinary half bridge on the main working principle of switch power supply is under the bridge and bridge switch tube (high frequency switch tube VMOS) conduction in turn, the first switch tube into the current through the bridge, use of inductance coil storage function, the electricity agglomeration in coil, finally close the switch tube on the bridge, open the switch tube under the bridge, inductor and capacitor continued to external power supply. Then close the lower bridge switch, and then open the upper bridge to let the current in, and so on and so on, because to turn on and off the two switches in turn, so called switching power supply.

And the linear power supply is not the same, because there is no switch to intervene, so that the upper pipe has been in the discharge of water, if there is more, will leak out, this is we often see some of the linear power supply of the adjustment tube heat is very large, with endless electric energy, all converted into heat energy. From this point of view, the conversion efficiency of linear power is very low, and when the heat is high, the life of the component is bound to decline, affecting the final use effect.

Why switch power supply? Instead of linear power?

The power regulating tube of the linear power supply always works in the discharge area and the current flowing through is continuous. As a result of the large loss of power on the adjustment tube, so the need for a larger power adjustment tube and a large volume of radiator, heating, efficiency is very low, generally in 40%~60%(also have to say that a very good linear power supply).



The working mode of linear power supply makes it necessary to have a switching device from high voltage to low voltage, which is generally a transformer, and there are other sources like KX power supply, and then output dc voltage through rectification. In this way the volume is also large, relatively bulky, inefficient, heat is also large; But there are also advantages: small ripple, good adjustment rate, small external interference, suitable for use with analog circuits/various amplifiers.

Switching power supply its power device work in the switching state, in the voltage adjustment energy is through the inductor coil to temporary storage, so that his loss is small, high efficiency is high, the requirements for heat dissipation is low, but it also has higher requirements for transformers and storage of energy inductance, to use low loss high permeability material to do. Its transformer is one word small. The total efficiency is in 80% ~ 98%, the switching power supply is high in efficiency but small in size, but compared with the linear power supply ripple, the voltage and current adjustment rate has a certain discount.

Kulon electronics is the global distributor of MeanWell switching power supplies, providing all MeanWell switching power products and models.

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