LINEAR VERSUS SWICTHING POWER SUPPLIES

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Switching and linear regulator use fundamentally different techniques to produce a regulated output voltage from an unregulated input.Each technique have advantages and disadvantages.So the application will determine will determine the moist suitable choice.

Linear power supplies can step-down an input voltage to produce a lower output voltage.This is done by operating a bipolar transistor or MOSFET pass unit in its linear operating mode.

Operating in this mode means that there is always a headroom voltage.Vdrop,between the input and the output.The linear regulators are 35 to 65 percent efficient and linear are cost-effective in step-down applications.

A low drop-out (LDO) regulator uses an improved output stage that can reduce VDROP to considerably less than 1.0V.This increases the efficiency and allow the linear regulator to be used in higher power applications.Designing with a linear regulator is simple and cheap,requiring few external components.A linear design is quieter than switcher since there is no high-frequency switching noise.

Switching power supplies operate by rapidly switching the pass units between two efficient operating states that is CUT OFF,where there is a high voltage across the pass unit but no current flow.

And the second is SATURATION,where there is high current the pass unit but at very small voltage drop.Switching power supplies are much more efficient,ranging from 65 to 95 percent.

The downside of a switching design is that it is considerably more complex.In addition,the output voltage contains switching noise,which is must be removed for many applications.

Although there are clear differences between linear and switching regulators,many applications require both types to be used.For examples,a switching regulator may provide the initial regulation,and then a linear regulator may provide post-regulation for a noise-sensitive part of the design,such as a sensor interface circuit.

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