Basic of Zener Regulators

1. Basic of Regulators
Rajesh B. Lohani
Dept. of E & TC
Goa College of Engineering
1
References
Electronic Device Theory Robert Boylestead and Nashelsky
Electronic Devices and Circuits by Allan Mottershead
Integrated Electronics by Millman Halkias
Weber State University.
EMT212/4 – Analogue Electronic II
Courtesy : Google images
The presentation focus on the basics of
regulators.

2. Learning Objectives
2
i) Understand the basic operation of zener as voltage regulators.

3. A voltage regulator is a system designed
to automatically maintain a constant
voltage level.
A voltage regulator may use a simple feed-forward
design or may include negative feedback.

4. Zener Breakdown
Avalanche Breakdown
The Zener Breakdown and Avalanche Breakdown are two
different mechanisms by which a PN junction breaks. The
Zener and Avalanche breakdown both occur in diode under
reverse bias.
The avalanche breakdown
occurs because of the
ionisation of electrons and
hole pairs
The Zener diode occurs because of
heavy doping.
The temperature coefficient of the
avalanche breakdown is positive, and
the temperature coefficient of Zener breakdown is negative.

5. zener voltage regulator
 The zener voltage regulator consists of a current limiting
resistor RS connected in series with the input voltage VS
with the zener diode connected in parallel with the load RL
in this reverse biased condition.
 The stabilised output voltage is always selected to be the same as the
breakdown voltage VZ of the diode.

7. A voltage regulator is a system designed to
automatically maintain a constant voltage level.
A voltage regulator may use a simple feed-forward
design or may include negative feedback.
A voltage stabilizer is a device designed to
reduce the variations in voltage of the supply to some
other apparatus.
The voltage regulator will correct for both input as well as load change.
A voltage stabilizer corrects for input voltage changes but not for changes in load.
Voltage stabilizers have been classified into three main types:
A: Maintains constant voltage independent of changes in the supply but not
independent of load changes.
B: Maintains constant voltage independent of changes of load but not independent of
supply changes.
C: Maintains constant voltage independent of supply and load changes

8. Zener diode regulator
 For low current power supplies - a simple
voltage regulator can be made with a
resistor and a zener diode connected in
reverse.
 Zener diodes are rated by their breakdown
voltage Vz and maximum power Pz.

9. Voltage Regulation
 Two basic categories of voltage regulation are:
 line regulation
 load regulation
 The purpose of line regulation is to maintain a nearly
constant output voltage when the input voltage varies.
 The purpose of load regulation is to maintain a nearly
constant output voltage when the load varies

10. Line Regulation
Line regulation: A change in input (line) voltage does not significantly affect the
output voltage of a regulator (within certain limits)

11. Line Regulation
 Line regulation can be defined as the percentage
change in the output voltage for a given change in
the input voltage.
Δ means “a change in”
 Line regulation can be calculated using the following
formula:
%100








IN
OUT
V
V
regulationLine
 
IN
OUTOUT
V
VV
regulationLine



%100/

12. Load Regulation
Load regulation: A change in load current (due to a varying RL) has practically no
effect on the output voltage of a regulator (within certain limits)

13. Load Regulation
 Load regulation can be defined as
the percentage change in the output
voltage from no-load (NL) to full-load (FL).
 Where:
VNL = the no-load output voltage
VFL = the full-load output voltage
%100




 

FL
FLNL
V
VV
regulationLoad

14. Load Regulation
 Sometimes power supply manufacturers
specify the equivalent output resistance (Rout)
instead of its load regulation.
 RFL equal the smallest-rated load resistance, then VFL:








FLOUT
FL
NLFL
RR
R
VV

15. Load Regulation - summary
 Rearrange the equation:
%100
%1001
%100






















 






 

FL
OUT
FL
FLOUT
FL
FL
FL
FLOUT
FL
FL
FLOUT
FLNL
R
R
regulationLoad
R
RR
regulationLoad
V
V
R
RR
V
regulationLoad
R
RR
VV

16. 16
Learning Outcomes
The viewer will be able to classify the different types of
regulators.
 Differentiate between line and load regulation.
Constructive criticisms are welcome for further improvement.
You can reach me at: rblohani@gec.ac.in
This presentation has been peer-reviewed by Dr. Samarth Borkar.
Thanks to Mr. Pushpshil Satardekar for support.

17. Dedicated to my loving parents
Late. Janaki B. Lohani and Mr. Basant B. Lohani
(Retd. Principal)
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18. Thank You for your time.