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Topic: Question: Shunt voltage regulator... (Read 1 time) previous topic - next topic

Voidugu

Hey guys i would like to know what is the difference between a shunt voltage regulator (example tl431) and a normal adjustable voltage regulator (example lm317)(Not between the actual two examples but generally.The examples are used as examples only).
What exactly is a shunt voltage regulator?

Thanks in advance

Dima

jackrae


dc42

Think of a voltage regulator as a potential divider, where the regulator constantly adjusts one of the resistors in the potential divider to maintain the desired output voltage.

A shunt regulator is like a precision Zener diode. It is used in place of the resistor to ground in the voltage divider. The other resistor (between it and the power supply) must be provided externally. The regulator works by shunting excess current through itself, so that the voltage drop across the external resistor is exactly the right amount to reduce the supply voltage to the voltage required.

A series regulator goes in place of the upper resistor in the potential divider. The load takes the place of the lower resistor. The series regulator also needs a ground connection to monitor the output voltage. The regulator works by adjusting the current flow through itself to give the desired output voltage.

So a shunt regulator wastes power by shunting excess current to ground, while a series regulator wastes less power by only letting through the current required. That is why these days, shunt regulators are only used for voltage references and similar very low current applications.
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Voidugu

Emmmmm... Why use a shunt voltage regulator instead of a simple zener diode?

Docedison

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dhenry

Quote
What exactly is a shunt voltage regulator?


Both types of regulators can be considered as "variable resistors". The series regulators increase their resistance to lower the voltage on the load. The shunt regulators decrease their resistance to divert away current from the load.

As a result, unlike the series regulators, there has to be some resistance between the load / shunt regulator and the voltage source. Because of that, most high current regulators are series regulators.

Vs. a zener, a regulator, series or shunt, has much sharper knees, so their output voltage is far less dependent on external factors.

Docedison

What?
Quote
Vs. a zener, a regulator, series or shunt, has much sharper knees, so their output voltage is far less dependent on external factors.

How? the same structures are present in an adjustable Zener as are in a series or linear regulator..
All of it starts life as a variant on the band gap device invented by Robert Widlar @ National Semiconductor.

Bob
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"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

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