Zener Diode: Workability in Reverse and Forward Bias

This article explains the workability of Zener diode in reverse and forward bias. It covers the Volt-Ampere properties, breakdown voltage, and resistance of Zener diode. It also discusses how Zener diode is used as a line and load regulator in power conversion. The article includes the experiment procedure and results.

POWER ELECTRONIC AND GENERATION
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INTRODUCTION
Diodes are basically known devices that allow the current to flow in one specific direction in the
case of the forward biased. It offers much resistance to the current that flows when applied as the
reverse biased. The type of diode called Zener diode not only allows for the flow of the current is
the forward direction but also in the reverse direction when used as forward bias and reverse bias
respectively. In this kind of the applications, the applied voltage is right above the breakdown
voltage. This threshold voltage is called Zener breakdown voltage. This kind of voltage may be
defined as the voltage at which the diode starts conducting in the direction that is considered
reverse(Tam, Kok, Siu and Wong 2014). The uniqueness is defined by the ability to permit the
reverse flow of the current when the value of the voltage meets a specific value that is required.
The Zener voltage is the much talked about breakdown voltage. The value of the Zener voltage
normally has higher value in the case of the standard values. The design of the Zener voltage is
normally kept as low as possible. The breakdown is controlled in such a way that the diode is not
damaged when there is reversal of the current whose value is slightly above the voltage of the
Zener.
Experiment
Main Aim
To properly study and also analyze the workability of the Zener diode in the reverse bias and
also forward bias.
Specific objectives

o Plotting of the Volt-Ampere properties of the Zener diode
o To evaluate the Zener breakdown voltage in the reverse biased situations
o Calculations of the dynamic and static resistance of the Zener diode in both the reverse
and forward conditions that is evident before and after the breakdown.
Required Components
Zener Diode (1N5232B)
RL= 1k , Rs = 100
Black Board and Jumper Wire
DZ = Zener diode,
VZ = VL, Vo = 5.6 V
Vin = 10 – 15 V, IL = 10 mA, RL=?
Equipment:
Number of S Name Amount
1 DC regulated power supply
dual type of capacity 0-30V
One
2 A digital Ammeter type of
capacity 0-200mA
Two
3 Voltmeter(digital) 0-20V One
4 Decade Resistance Box One
5 Wires for connection One
Specifications of the Zener Diode (1N5232B)
Voltage for the breakdown=5.2V

Dissipation of power=0.75W
Highest forward current=1A.
Operation
The zener diodes are those kinds of the diodes that allow the current to flow in the forward
direction. The uniqueness is defined by the ability to permit the reverse flow of the current when
the value of the voltage meets a specific value that is required. The Zener voltage is the much
talked about breakdown voltage. The value of the Zener voltage normally has higher value in the
case of the standard values. The design of the Zener voltage is normally kept as low as possible.
The breakdown is controlled in such a way that the diode is not damaged when there is reversal
of the current whose value is slightly above the voltage of the Zener. The most widely
recognized qualities for ostensible working voltage are 5.1 V, 5.6 V, 6.2 V, 12 V and 15 V. We
additionally convey Zener diodes with ostensible working voltage up to 1 kV. Forward (drive)
current can have a range from 200 uA to 200 A, with the most widely recognized forward (drive)
current being 10 mA or 200 mA. In the forward predisposition heading, the zener diode carries
on like a customary silicon diode.

Figure 1: Circuit diagram for Zener (Yu, Iu, Fitch and Liang 2014)
In the switch inclination bearing, there is for all intents and purposes no invert current stream
until the point when the breakdown voltage is come to. At the point when this happens there is a
sharp increment in turn around current. Fluctuating measure of switch current can go through the
diode without harming it. The breakdown voltage or zener voltage (VZ) over the diode remains
moderately consistent. The most extreme switch current is constrained, be that as it may, by the
wattage rating of the diode.
Avalanche Breakdown
At the point when the diode is in the turnaround predisposition condition, the width of the
exhaustion area is more. In the event that both p-side and n-side of the diode are delicately
doped, consumption area at the intersection extends. In invert predisposition, the minority charge
bearer current moves through intersection. As the connected turn around voltage builds the
minority transporters secure adequate vitality to slam into the bearers in the covalent bonds
inside the consumption area. Therefore, the security breaks and electron gap sets are created. The
procedure ends up aggregate and prompts the age of an expansive number of charge bearers
bringing about Avalanche Breakdown.
Regulation of voltage using zener:
The amount of the current in the circuit can easily be controlled using different gadgets that are
connected either in parallel or series with other components within the circuit. However it is
important to note that every application of the appliances will require specific amount of the
current for effective running. In order to achieve this, the specific value of the current must be
matched with the regulated voltage. . The voltage for the input is taken as a variable with no

ripples. The switches of the electronics open and close at a rate that is fixed for example at a
value of 100kHzThe duty cycle however is varied to give the output with designation of the
Vout. The commonly used controller normally contributes reliable values of the voltage. It is this
kind of behaviour that earns this gadget a lot of applications in the industrial set up .The diode
works in a way that assist in the proper coordination of the current and voltage. If this kind of the
information was to be represented using the methods of the graph, the extrapolation of the excess
values of the current would have been achieved prior. The conduction of the current by the diode
is very evident at the point when excess voltage is registered. When the value of the current is
significantly low, the effect is negligible. When the resistance is also too low, the diode may be
used to check for the pattern of the current flow.
There are essentially two sorts of the known directions.
Line regulation
In this kind of the regulation, the load resistance and the series resistance are fixed values. The
only value that is changing is the input voltage. The value of the output voltage will remain
constant as long as the value of the input voltage is kept above the specific minimum
value(Yajun, Collins, Steigerwald, Koninklijke and Lumileds 2013).
Load Regulation
In this kind of the regulation, the voltage of the input is fixed and there is variation in the value
of the load resistance. The output volt remains the same. This is possible as long as the resistance
of the load is kept constant and also kept above the specific value of the required threshold.
Circuit Diagram

Condition of Forward bias
Figure 2: Condition of Forward bias
Illustrative circuit
Figure 3: Condition of illustrative circuit
A diode used in the regulation of the line within the circuit.

Figure 4: Representation of the two in the diagram of the circuit.(Frisch and Desbruslais 2013)
Figure 5: Zener
diode as the line
regulator in the
circuit diagram(Frisch and Desbruslais 2013).
Procedure
In order to achieve the forward condition, the following steps were followed.
1. The circuit was connected as shown in the above diagram.
2. The Vs value was initially varied. The process of the variation was continued as the value
of the voltage changed from the 1 to 12 voltage.
3. The values of the current in the reverse points were recorded against the reverse voltages.
Zener diode as Line regulator

This was used in the case of the variations in the supply of the voltage.
1. The circuit was connected as shown in the figure above.
2. The voltage was varied in steps of 1volts from volts to 15 volts.
3. The generated graph was provided.
4. The graph was plotted for the confirmation.
Zener diode as load regulator
This was used in the variation of the connected load.
1. The circuit for the load regulation was as had been indicated above.
2. The power supply was then fixed at 10Volts.
Results
VZ = 5.6 V.
VL = 5.6 V;Po = 500 mW
I Z= P0
V z
=500 mW
5.6V ; I Z=89.29 mA
Is = IL + Iz = 10 + 89.29 = 99.29 mA
Vs = Vin – Vz
If Vin = 10 V;Vs = 10 – 5.6 = 4.4 V
RS= V s
Is
= 4.4
99.29 =44.31 Ω .

I S=106 mA−89.29 mA =16.71mA
If Vin = 15 V,;Vs = 15 – 5.6 = 9.4 V
RS= V s
Is
= 9.4
99.29 =94.67 Ω
I S=338.5mA −89.29 mA =249.21mA
Use 15V,; RS=94.67 Ω≈ 95 Ω; RL= V L
I L
= 5.6 V
10 mA =560 Ω
For Vin = 10
Vin(V) Vo(V)
10 6.04
11 6.07
12 6.11
13 6.19
14 6.23
15 6.24
IL(mA) Vo(V)
0 6.07

15 6.05
20 6.01
30 5.99
40 5.96
50 5.92
60 5.80
70 5.35
80 4.56
90 3.98
100 3.45
105 2.12
For Vin = 15
Vin(V) Vo(V)
10 6.04
11 6.07
12 6.11
13 6.19
14 6.23
15 6.24
IL(mA) Vo(V)
0 6.27
15 6.24
20 6.21
30 6.18
40 6.15
50 6.10
60 6.04
70 6.01
80 5.98
90 5.34
100 2.56
105 0.65

Graphical presentation.
SWITCHING CONVERSION
The devices that are analog in nature have very big range of regulators for switching and whose
operation are based on the principle of step up and step down in the modes of the inversion, The
devices have the ability to produce output voltage that is adjustable or one that is fixed already.
The maximum output of the current is normally at the 2A.The commonly available features at
the regulation point include the following:
 Low battery
 Adjustable limit of the current
 Variety of the frequencies for switching
 Lowered quantity of the external components
This kind of the family products are expected to reduce the number of the external components
in the case of the space challenged uses.

Figure 6: Circuit diagram for power conversion (Frisch and Desbruslais 2013).
There are several advantages of the high efficiency DC-DC switching ICs.Some of these
advantages include;
 Generation of less heat
 Consumption of less current
 Needs less space in the board and this allow for the robust operation and longer life for
the battery.
The regulator for the switch may be used as an inductor, a power switch or as a diode to assist in
the energy transfer from one input to the output. The basic components of the circuit for
switching can actually be arranged so as to form a step down that is also called the buck
converter, an inverter or the boost system also known as the step up convertyer.The addition of
the control circuitry and feedback may assist in the regulation of the energy transfer and assist in

the maintenance of the constant output(Kleemann, Gutierrez, Avdoshenko, Cuniberti, Leo and
Lüssem 2013). There is provision of the high switching frequencies that are known to be very
efficient in the internal switching of the other elements, the built in circuit protection that support
a wide range of the applications and finally the board input ranges.
Experiment
Objectives
To observe the operating characteristics of the boost, the buck and the buck-boost.
Equipment
Converter box of DC-DC
A 3-ph resistor load box
Fluke 43B power quality analyzer
Fluke 4mm Test pins
Banana Test Leads
Small screw driver.

Figure 7:Laboratory diagrams of the connections(Frisch and Desbruslais 2013).
Procedure
The following procedure was used in the laboratory for the process.
1. The fluke 43B was set up
2. The Buck converter was connected to the circuit that is indicated below by the use of the
DC-DC converter box and banana test leads while taking the input voltage at
approximately +13V.
Figure 8:Circuit diagram (Frisch and Desbruslais 2013)
Buck-converter circuit
1. The power was then supplied
2. The measurements were then recorded
Buck-Boost Converter Circuit
1. The wiring was changed so as to allow for the creation of the buck-boost converter.

2. The input voltage was maintained at the positive value while the output voltage was
considered the voltage across the capacitor and the load box.
The below circuit was considered.
Figure 9: Circuit diagram(Roy et al 2015)
Results
Diagram of Switching Power Conversion

Figure 10: Conventional layout (Roy et al 2015)
Input Voltage = 10V (Don’t EXCEED 15V on this input)
Output Voltage = 5V
Load Current = 10mA
VL = 5.6V, IL = 10mA
RL= V L
I L
= 5.6 V
10 mA =500 Ω
I S= (10−5.6)
270 =16.3 mA
Load Current
IL (mA)
Output Voltage
(Volt)
0 2.999
100 2.991
110 2.953
190 2.950
230 2.945
280 2.944
310 2.938

400 2.936
510 2.901
610 2.887
700 2.398
800 2.216
Input Voltage
(Volt)
Output Voltage
(Volt)
4 2.952
8 2.977
12 2.985
16 2.991
18 2.992
VL = 5.6V, IL = 10mA
RL= V L
I L
= 5.6 V
10 mA =500 Ω
I S= (10−5.6)
270 =16.3 mA
Eff =Output power
Input power ×100 %
Loss Power=16.3 ×4.4=71.72 mW
Input Power = Output Power + Loss Power = 299.1mW + 71.72mW = 370.82mW
Output Current = 100mA
Output Voltage = 2.991V

Output Power = 299.1mW
Eff = 299.1
370.82 × 100 %
Eff =80.66 %
Graphical representation.
Series (Transistor Regulator)
AB32 is normally considered the ready to use experiment board of the Transistor Series Voltage
Regulator. This kind of the board is normally useful for those students that study the activities of
the transistor as a regulator of the voltage in the series connection. Normally it may be used as
the standalone unit that has external DC power supply.
Theory
Regulators are basically those circuits that are known to maintain the power supply of the
voltages or the output of the current but within the limits that are specified. The design normally

exploits the operation of the dc voltages depending on the areas of application(Ito, Miyata, and
Yokota 2013). The voltage regulator circuits are addition to the basic power supply circuits
whose components include the sections of the filter and the rectifier. The voltage regulator serves
to provide the output that has got very little variation. The circuit of the regulator will sense
changes and then provide compensation for the sensed changes. There are basically two types of
the voltage regulators are normally categorized as the shunt or series depending on the location
of the regulating elements(Roy et al 2015).
Figure 11:Series Transistor connections (Roy et al 2015).
In the diagram that has been labeled B,the suggested name series regulator is as a result of the
connection of the regulating device in a series manner. As can be seen from the given diagram, it
is clear that the regulator that is in series with the load resistance ,RL.Also the fixed resistor that
is marked as Rs is in series as well with the load resistance. Considering that the total current
sometimes passes through this kind of the transistor, it is normally called the pass transistor. The

other components that are known to be part of the circuit include the Zener diode of 5.6V and a
current limiting resistor of 200ohms.It is important to remember that the Zener diode is one that
will block the current until the specific value of the voltage is applied. The applied voltage is
normally called the breakdown or just the Zener voltage. When the Zener voltage value is finally
achieved, the conduction of the diode will be from the anode terminal to the cathode of the very
diode(Frisch and Desbruslais 2013).
Figure 12: Transistor circuit connection(Frisch and Desbruslais 2013)
In this kind of the voltage regulator, the transistor has a fixed value of the applied voltage that is
commonly referred to s the reference voltage. The changes in the output of the voltage are
detected and then corrected at the point of the emitter. The Zener diode will always assist in the
establishment of the base voltage.
Experiment 1
Objectives
To study the Transistor series voltage regulator with the variable load resistance,RL and fixed
input voltage.

Equipment
Analog board of AB32
Two digital multimeters
Two patch cords of 2mm each
A DC power supply.
The circuit diagram was as indicated below.
Figure 13:Circuit diagram (Frisch and Desbruslais 2013)
Procedure:
The following steps were followed in the experimental set up.
The power supply of +12V was connected at their respective positions from the external source.
One of the voltmeters was connected between the test point 1 and the ground so as to allow for
the measurement of the voltage, in.

The ohmmeter was connected between the test point 4 and the ground and the set value of the
load resistance Rl was placed at some fixed value of 1K.
The 2mm patch cord was connected between the test point 2 and 3 of the components.
The voltmeter test point was connected at position 4 so as to allow for the generation of the
output, Vout.
The power supply was then switched on.
The exercise of varying the potentiometer from the input voltage of 0V to 9V was carried out
while measuring the correspondence values of the output voltage,Vout,the Zener voltage, Vz and
also the forward biased voltage,VBE.
The patch cord was then disconnected from the points 2 and 3.
The procedure was repeated for confirmation of the accuracy.
Results and Calculations
The percentage of the regulation was obtained by the formula shown below.
% Regulation = [(VNL − VFL) / VFL] * 100
In which ;
R = resistance in series VNL = no-load or open-circuit terminal voltage. VFL = full-load
terminal voltage.
Results

The experimental results that were obtained indicated that the value of the fixed voltage ranged
from 0V to 5.54V.The percentage of the regulation was found to be 88.75%.
Experiment 2
Objectives:
To study Transistor Series Voltage regulator when the input voltage is considered variable and
the resistance of the load is taken as the fixed value.
Equipment
Analog board of AB32
Digital multimeters
Patch card of 2mm
A +12 voltage power supply from the external source.
The applied circuit diagram

Figure 13:Applied circuit diagram(Frisch and Desbruslais 2013)
Procedure
The 12 V power supply was connected to the indicated positions
The voltmeter was connected between the test point 1 and the ground so as to assist in the
measurements of the input voltage(Ribeiro, Marques and Borges 2012).
The ohmmeter was connected between the test point 4 and also the ground while putting the
value of the load resistance at RL maximum amount.
The two mm patch cords were connected between the test points 2 and 3.
The voltmeter was then connected between the test point 4 and the ground and this really assisted
in the measurements of the voltage output.
The potentiometer was varied after switching on of the power from as little value as 7V to as
maximum as 9V
The corresponding values of the Vout and the Vzener were measured.

Results
The results that were obtained from the experiment 2 indicated that for the network that had
fixed value of the load resistance, the output of the voltage will always remain unchanged and
very close to a value of 4.9V when the input voltage was from 7V to 9V.
Series (Buck Convertor)
Overview
The DC-DC converters are normally known to provide enough conversion of the DC voltage
from one level to another level. The word Buck converter basically means that the converter
takes an input current from a higher level of voltage like 36-42voltage from the solar panels to
another level of say12Vdc for use in the equipment(Qian, Liu, Sheng, Zhang, Li and Lai 2016)
Theory of operation
The basic components of the buck converter are as indicated below. The voltage for the input is
taken as a variable with no ripples. The switches of the electronics opens and closes at a rate that
is fixed for example at a value of 100kHzThe duty cycle however is varied to give the output
with designation of the Vout.The capacitor is assumed to be very large to provide an output with
less than 5% ripples. This basically means ripple free. In the normal cases of the operation, it is
assumed that the circuit is in continuous conduction(Yu, Iu, Fitch and Liang 2014).
Figure 14: ;layout of the circuit(Frisch and Desbruslais 2013)

It is important to note that 0.01 Ω will be required at the negative terminal as given so as to assist
in the measurement of the current at the point of the ouput.In oreder tpo have the overshoot
reduced across the Vin termainal,a capacitor of the value of the 10 μF will be needed.The
overshoot ios normally caused by the inductance.It is assumed that the circuit is basically
lossless so as to ensure that the value of the output is equal to the vakue of the input(Connelly,
Weiner, Miller and Helfer 2012).
Pin=Pout
When continous conduction is assumed,the circuit takes two states.The open switch is open and
closed as illustaretd in the diagram below.
For Switch closed
For switch open.
In the closed switches, the biasing of the diode is reversed. The iL increases at the rate given
below. The inductor however is charging properly.

When the switch is open, the iL will just continue to circulate through the diode and the diode is
biased forward. The iL value decreases at the illustrated rate.
In the continuous conduction, the wave form below is obtained.
Discontinuous Conduction
At the periods of the low loads the converter usually performs discontinuous in the mode of the
conduction. The third state therefore is achieved during which the all the power is provided by
the system of the capacitor. The voltage that is across the conductor thus becomes zero.

Discontinuous state of conduction.
Experiment
Procedure
A plan was developed for the circuit layout as indicated below on the piece of wood. The red
wire represented the +ve terminal and black wires represented –ve terminal(Morris, Han and
Sarlioglu 2017).
Figure 15: Buck circuit(Frisch and Desbruslais 2013).
The diode feature was used in the identification of the leads of the positive values and the
negative values.
The process of the wiring was completed as required.

The 10uF ripple current capacitor was connected across the terminal of the Vin.The polarity was
not important considering that the capacitor was bipolar.
The MOSFETsnubber capacitor was removed and discarded.
A 12 Vdc was connected to the wall wart of the dc jack so as to assist in the firing of the circuit.
The MOSFET firing circuit was connected to the buck converter. The wires were kept as short as
possible. A 10 Ω power resistor was connected to the output that is provided by the buck
conveter.The transformer was then connected to the DBR(Lu, Zhao, Ji,Yu and Yuan 2012).
Figure 16: Laboratory set up (Frisch and Desbruslais 2013)
A 10 Ω load, and frequency f = 50 kHz were used in the generation of the output.

Figure 17:Frequency curves(Frisch and Desbruslais 2013)
CONCLUSION
The general trial gave knowledge of the methods for changing over the AC capacity to the Dc
control. This was viewed as extremely helpful in knowing since the majority of the electrical
machines have such circuits introduced in them. Additionally thinking about that the greater part
of the machines typically expect control voltage estimation of 120VAc,the learning of the change
connects to the data sources. This ought to be consolidated at the plan arrange. The inspiration
concept that assist in the driving of the controller of the voltage will always ensure that the value
is kept bat the recommended level.

This effect normally assists in the balancing of the established relationship between the voltage
and the current.(Boylestad and Nashelsky 2012). It is important to note that 0.01 Ω will be
required at the negative terminal as given so as to assist in the measurement of the current at the
point of the ouput.In oreder tpo have the overshoot reduced across the Vin termainal,a capacitor
of the value of the 10 μF will be needed.The overshoot ios normally caused by the inductance
(Yang, Yao and Monolithic 2013). The Zener conducts the smallest current when the load
current is the most raised and it drives the most present when the pile current is the minimum.
The data that has been learned on the voltage controllers can be to a great degree helpful when
utilizing the parts that are ordinarily seen to be touchy to the changes of the information voltage.
The examination represented alternate methods for making the cradle inside the circuit a section
from the known strategies.
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