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Regulators filters out ripple?

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TommyF

May 18, 2015
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How does a Linear or switching Regulator chip filter out ripple?

The ripple percentage is filtered out even more when it passes through a regulator chip. I don't see any filtering components inside a regulator chip to filter out ripple.
 

davenn

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Sep 5, 2009
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lets take the 78/79xx series linear reg

here's the block diag

78xx series block.GIF

The error amplifier using the reference voltage is going to do all it can to keep any variations in the output voltage to a minimum
it will compensate for variations in voltage on the input. And that is all ripple is ... a slight variation in the DC voltage


Dave
 

TommyF

May 18, 2015
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Yes the error amplifier is a comparator , it compares the reference voltage with the output voltage. If there is an difference it will adjust the series pass transistor.

So it's not filtering out the ripple, it's leveling out the variations to keep it steady
 

TommyF

May 18, 2015
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Some power supplies are low impedance and other power supplies are high impedance. What is the difference between them and when do you use a low impedance power and when do you use a high impedance power supply?
 

davenn

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So it's not filtering out the ripple, it's leveling out the variations to keep it steady

and that also (as I said earlier) effectively filters out the ripple

do you really not understand what ripple is ?
 

TommyF

May 18, 2015
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Yes it's Smoothing out the ripple by an error amplifier and the series pass transistor

LDO low drop out regulators use a series pass FET which has no voltage drop and other advantages which i don't know about.
 

TommyF

May 18, 2015
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Each power supplies technology has different line or load regulation methods.

When I turn down the AC line voltage under 90VAC until the power supply turns off. The cutting off voltage is between 80vac to 90vac. I'm not sure what sets the cutting off voltage in a power supply.
 
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