How Zener Diode is used as voltage regulator? Please explain with circuit diagram and in detail

 

Is this an assignment? Homework?

 

Hello,

Have a look at the following PDF:
http://www.eettaiwan.com/ARTICLES/2001JUN/2001JUN14_AMD_AN2002.PDF

This is one of the links from this page of the EDUCYPEDIA:
http://educypedia.karadimov.info/electronics/composemiconductordiode.htm

Bertus

 

Is this an assignment? Homework?

No this is not an assignment.

 

In addition to Bertus' links, here is another.

http://www.electronics-tutorials.ws/diode/diode_7.html

 

In addition to Bertus' links, here is another.

http://www.electronics-tutorials.ws/diode/diode_7.html

I've read the Article from Electronics-Tutorials. But a sentence from there is confusing me. First there written the voltage across R is always
the same as the zener voltage, ( Vz = Vr ). And at last The supply voltage Vs must be greater than Vz . So this means Vs is always greater than Vs due to initial voltage drop in Resistance. So is my speculation is correct that Vs is always greater than Vs due to initial voltage drop in Resistance.

 

To check this basic conception of zener diode first -
The Equivalent Circuit of Zener diode Using Diode and LED Protection.

 

I've read the Article from Electronics-Tutorials. But a sentence from there is confusing me. First there written the voltage across R is always
the same as the zener voltage, ( Vz = Vr ). And at last The supply voltage Vs must be greater than Vz . So this means Vs is always greater than Vs due to initial voltage drop in Resistance. So is my speculation is correct that Vs is always greater than Vs due to initial voltage drop in Resistance.

V sub R is not the voltage across the resistor it is the Reverse Bias voltage ACROSS THE ZENER DIODE. V sub z has a fixed value for each diode. It will vary a little bit from diode to diode in a lot of "identical" diodes. V sub R in a given circuit will vary from zero to some negative value where the junction breakdown occurs. The purpose of the resistor in a zener diode regulator is to limit the current through the zener diode so that breakdown will NOT occur.

You are correct that V sub S will always be greater than V sub Z. This is true of all linear regulators. It is only untrue for some types of switching regulators.

Does that clear things up a bit?

 

V sub R is not the voltage across the resistor it is the Reverse Bias voltage ACROSS THE ZENER DIODE. V sub z has a fixed value for each diode. It will vary a little bit from diode to diode in a lot of "identical" diodes. V sub R in a given circuit will vary from zero to some negative value where the junction breakdown occurs. The purpose of the resistor in a zener diode regulator is to limit the current through the zener diode so that breakdown will NOT occur.

Does that clear things up a bit?

Yes it's clear now. Does temperature affect the working of Zener diode ? As lot of diodes are temperature dependance.

 

Zeners make pretty crappy regulators in general, not used much except where poor regulation and power waste can be traded for circuit simplicity.