I. Types of Diode:

 

Backward Diode

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– This type of
diodae is also called the back diode, and it is not widely used. The backward
diode is a PN-junction diode that is similar to the tunnel diode in its
process. It finds a few special applications where its specific properties can
be used.

 

BARITT Diode

– The short
term of this diode Barrier Injection Transit Time diode is BARITT diode. It is
applicable in microwave applications and allows many comparisons to the more
widely used IMPATT diode. Please refer the below link for BARRITT Diode

 

Gunn Diode

– Gunn diode
is a PN junction diode, this sort of diode is a semiconductor device that has
two terminals. Generally, it is used for producing microwave signals.

 

Laser Diode

– The laser
diode is not the similar as the ordinary LED (light emitting diode) because it
generates coherent light. These diodes are extensively used in many
applications like DVDs, CD drives and laser light pointers for PPTs. Although
these diodes are inexpensive than other types of laser generator, they are much
more expensive than LEDs.

 

Light Emitting Diode

– The term LED
stands for light emitting diode, is one of the most standard types of the
diode. When the diode is connected in forwarding bias, then the current flows
through the junction and generates the light. There are also many new LED
developments are changing they are LEDs and OLEDs.

 

Photodiode

– The
photodiode is used to detect light. It is found that when light strikes a
PN-junction it can create electrons and holes. simply noticed. These diodes can
also be used to produce electricity.

 

 

 

 

. PIN Diode

– This type of
diode is characterized by its construction. It has the standard P-type &
N-type regions, but the area between the two regions namely intrinsic
semiconductor has no doping. The region of the intrinsic semiconductor has the
effect of increasing the area of the depletion region which can be beneficial
for switching applications.

 

.PN Junction Diode

– The standard
PN junction may be thought of as the normal or standard type of diode in use
today. These diodes can come as small signal types for use in RF (radio
frequency), or other low current applications which may be called as signal
diodes. Other types may be planned for high voltage and high current
applications and are normally named rectifier diodes.

 

Schottky Diode

– The Schottky
diode has a lower forward voltage drop than ordinary Si PN-junction diodes. At
low currents, the voltage drop may be between 0.15 & 0.4 volts as opposed
to 0.6 volts for a Si diode. To attain this performance they are designed in a
different way to compare with normal diodes having a metal to semiconductor
contact. These diodes are extensively used in rectifier application, clamping
diodes, and also in RF applications.

 

Step Recovery Diode

– A step
recovery diode is a type of microwave diode used to generate pulses at very HF
(high frequencies). These diodes depend on the diode which has a very fast
turn-off characteristic for their operation.

 

 Tunnel Diode

– The tunnel
diode is used for microwave applications where its performance surpassed that
of other devices of the day.

 

 

 

 

 

. Varactor Diode or Varicap Diode

–  Varactor diode is one sort of semiconductor
microwave solid-state device and it is used in where the variable capacitance
is chosen which can be accomplished by controlling voltage. These diodes are
also called as variceal diodes. Even though the o/p of the variable capacitance
can be exhibited by the normal PN-junction diodes.But, this diode is chosen for
giving the preferred capacitance changes as they are different types of diodes.
These diodes are precisely designed and enhanced such that they allow a high range
of changes in capacitance.

 

Zener Diode

– The Zener
diode is used to provide a stable reference voltage. As a result, it is used in
vast amounts. It works under reverse bias condition and found that when a
particular voltage is reached it breaks down. If the flow of current is limited
by a resistor, it activates a stable voltage to be generated. This type of
diode is widely used to offer a reference voltage in power supplies.

 

II. Rectifier Circuit:

 

Half Wave Rectifier circuit

– A rectifier
is a circuit which converts the Alternating Current (AC) input power into a
Direct Current (DC) output power. The input power supply may be either a
single-phase or a multi-phase supply with the simplest of all the rectifier
circuits being that of the Half Wave Rectifier.

 

 

Average voltage, Vaverage = Vm/?  
  |     Average Current, Iaverage = Im/?

 

Rms Voltage, Vrms = Vm/2      
             |      Rms
Current, Irms = Im/2

 

 

 Full Wave Rectifier circuits

– A full wave rectifier is a type of rectifier which converts both half
cycles of the AC signal into pulsating DC signal.

 

 

Average voltage, Vaverage =
2Vm/?     |     Average Current, Iaverage =
2Im/?

RMS Voltage, Vrms = Vm/?2
                   |  
  RMS Current, Irms = Im/?2

The full wave
rectifier is further classified into two types: center tapped full wave
rectifier and full wave bridge rectifier.

 

Center tapped full wave rectifier

–         
The Center Tapped Full Wave Rectifier employs a
transformer with the secondary winding AB tapped at the center point C. It
converts the AC input voltage into DC voltage the two diode D1, and D2 are
connected in the circuit as shown in the circuit diagram below.

Full Wave Bridge Rectifier: Bridge rectifier circuit

–         
A Full wave rectifier is a circuit arrangement which
makes use of both half cycles of input alternating current (AC) and converts
them to direct current (DC). In our tutorial on Half wave rectifiers, we have
seen that a half wave rectifier makes use of only one-half cycle of the input
alternating current. Thus a full wave rectifier is much more efficient
(double+) than a half wave rectifier. This process of converting both half
cycles of the input supply (alternating current) to direct current (DC) is termed
full wave rectification.

III. Block Diagram of Power Supply.

 

 

A transformer is a static electrical
device that transfers energy by inductive coupling between its winding
circuits. A varying current in the primary winding creates a varying magnetic
flux in the transformer’s core and thus a varying magnetic flux through the
secondary winding. This varying magnetic flux induces a varying electromotive
force (EMF) or voltage in the secondary winding. Transformers range in size
from thumbnail-sized used in microphones to units weighing hundreds of tons
interconnecting the power grid. A wide range of transformer designs are used in
electronic and electric power applications. Transformers are essential for the
transmission, distribution, and utilization of electrical energy.

 

A rectifier is an electrical device that
converts alternating current (AC), which periodically reverses direction, to
direct current (DC), which flows in only one direction. The process is known as
rectification. Physically, rectifiers take a number of forms, including vacuum
tube diodes, mercury-arc valves, copper and selenium oxide rectifiers,
solid-state diodes, silicon-controlled rectifiers and other silicon-based
semiconductor switches. Historically, even synchronous electromechanical
switches and motors have been used. Early radio receivers, called crystal radios,
used a “cat’s whisker” of fine wire pressing on a crystal of galena
(lead sulfide) to serve as a point-contact rectifier or “crystal
detector”. The simple process of rectification produces a type of DC
characterized by pulsating voltages and currents (although still
unidirectional). Depending upon the type of end-use, this type of DC current
may then be further modified into the type of relatively constant voltage DC
characteristically produced by such sources as batteries and solar cells.

 

Filter capacitors
are capacitors used for filtering of undesirable frequencies. They are common
in electrical and electronic equipment, and cover a number of applications. The
simple capacitor filter is the most basic type of power supply filter. The
application of the simple capacitor filter is very limited. It is sometimes
used on extremely high-voltage, low-current power supplies for cathode-ray and
similar electron tubes, which require very little load current from the supply.
The capacitor filter is also used where the power-supply ripple frequency is
not critical; this frequency can be relatively high.

 

A voltage regulator is designed to
automatically maintain a constant voltage level. A voltage regulator may be a
simple “feed-forward” design or may include negative feedback control
loops. It may use an electromechanical mechanism, or electronic components.
Depending on the design, it may be used to regulate one or more AC or DC
voltages.

 

 

IV. Application of Diode

1. Reverse Current Protection

            Ever stick a battery in the wrong
way? Or switch up the red and black power wires? If so, a diode might be to
thank for your circuit still being alive. A diode placed in series with the
positive side of the power supply is called a reverse protection diode. It
ensures that current can only flow in the positive direction, and the power
supply only applies a positive voltage to your circuit.

This diode
application is useful when a power supply connector isn’t polarized, making it
easy to mess up and accidentally connect the negative supply to the positive of
the input circuit.

 

The drawback
of a reverse protection diode is that it’ll induce some voltage loss because of
the forward voltage drop. This makes Schottky diodes an excellent choice for
reverse protection diodes.

 

2. Demodulation of Signals

The most common use for diodes is to remove the negative component of an
AC signal so it can be worked with easier with electronics. Since the negative
portion of an AC waveform is usually identical to the positive half, very little
information is effectively lost in this process. Signal demodulation is
commonly used in radios as part of the filtering system to help extract the
radio signal from the carrier wave.

 

 

 

 

 

 

 

 

 

 

 

 

 

3. Over-Voltage
Protections

Diodes also function well as protection devices for sensitive electronic
components. When used as voltage protection devices, the diodes are
non-conducting under normal operating conditions but immediately short any high
voltage spike to ground where it cannot harm an integrated circuit. Specialized
diodes called transient voltage suppressors are designed specifically for
over-voltage protection and can handle very large power spikes for short time
periods, typical characteristics of a voltage spike or electric shock, which would
normally damage components and shorten the life of an electronic product.

 

4. Current Steering

The basic application of diodes is to steer current and make sure it
only flows in the proper direction. One area where the current steering
capability of diodes is used to good effect is in switching from power from a
power supply to running from a battery. When a device is plugged in and
charging, for example, a cell phone or uninterruptible power supply, the device
should be drawing power only from the external power supply and not the battery
and while the device is plugged in the battery should be drawing power and
recharging. As soon as the power source is removed, the battery should power
the device so no interruption in noticed by the user.