H2 - AC to DC
Yrd. Doç. Dr. Aytaç Gören
ELK 2018 - Contents
W01 Basic Concepts in Electronics
W02 AC to DC Conversion
W03 Analysis of DC Circuits
W04 Transistors and Applications (H-Bridge)
W05 Op Amps and Applications
W06 Sensors and Measurement (1/2)
W07 Sensors and Measurement (2/2)
W08 Midterm
W09 Basic Concepts in Digital Electronics (Boolean Algebra, Decimal to binary, gates)
W10 Digital Logic Circuits (Gates and Flip Flops)
W11 PLC’s
W12 Microprocessors
W13 Data Acquisition, D/A and A/D Converters.
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ELK 2018 – W01 Contents
1.
2.
3.
4.
5.
6.
AC – Form and values of grid
Potentiometer
Transformers
Semi Conductors
Diodes
Conversion to DC
1.
2.
3.
4.
7.
8.
Half Wave Rectifier
Half Wave Rectifier with Smoothing Capacitor
Using full wave rectifier
Using diode bridge rectifier
7805 Voltage Regulator IC
Switch Mode Power Supply Selection
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Why conversion?
Electricity is transferred from power plants to houses or business
as alternate current because of decreasing losses during transfer.
On the other hand, semi conductors use direct current. Thus, it is
needed to be changed to direct current.
A rectifier is a circuit which converts the Alternating Current (AC)
input power into a Direct Current (DC) output power.
Yrd. Doç. Dr. Aytaç Gören
Potentiometer
http://mechatronics.poly.edu/
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Potentiometer
Yrd. Doç. Dr. Aytaç Gören
Transformers
Ref: http://www.physics.sjsu.edu/becker/physics51/ac_circuits.htm
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Transformers
Ktrafo
NS VS IP

 
NP VP IS
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Ref: http://www.physics.sjsu.edu/becker/physics51/ac_circuits.htm Yrd. Doç. Dr. Aytaç Gören
Semi Conductors
Semiconductors materials such as silicon (Si),
germanium (Ge) and gallium arsenide (GaAs), have
electrical properties somewhere in the middle, between
those of a "conductor" and an "insulator".
They are not good conductors nor good insulators
(hence their name "semi"-conductors).
They have very few "fee electrons" because their atoms
are closely grouped. That is due to the strength of the
molecular bounds
However, their ability to conduct electricity can be
greatly improved by adding certain "impurities" to this
crystalline structure thereby, producing more free
electrons than holes
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Semi Conductors Semiconductors- Silicon
The most commonly used semiconductor basics material by far is silicon. Its
atomic number is 14
Silicon has four valence electrons in its outermost shell
The structure of the bond between the two silicon atoms is such that each
atom shares one electron with its neighbour
This bound is very stable and called as co valent bound crystals of pure
silicon (or germanium) are therefore good insulators.
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Yrd. Doç. Dr. Aytaç10Gören
Semi Conductors
Semiconductor N-type
In order for our silicon crystal to conduct electricity, we need to introduce
an impurity atom such as Arsenic, Antimony or Phosphorus
These atoms have five outer electrons in their outermost orbital to share
with neighbouring atoms. This allows four out of the five orbital
electrons to bond with its neighbouring silicon atoms leaving one "free
electron" to become mobile when an electrical voltage is applied.
The resulting
semiconductor material
has extra electrons, each
with a negative charge,
and is therefore referred
to as an "N-type" material
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Yrd. Doç. Dr. Aytaç11Gören
Semi Conductors Semiconductor P-Type
Another way to make silicon crystal conduct electricity is to add impurity
atoms such as Aluminium, Boron or Indium, which have only three
valence electrons
Therefore, a complete connection is not possible, giving the semiconductor
material an abundance of positively charged carriers known as "holes" in
the structure of the crystal where electrons are effectively missing.
The doping of such
atoms causes
conduction to consist
mainly of positive charge
carriers resulting in a "Ptype" material with the
positive holes
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Yrd. Doç. Dr. Aytaç12Gören
Semi Conductors
Semiconductor –
PN Junction
These semiconductor N and P-type materials do very little on
their own as they are electrically neutral,
but when we join (or fuse) them together these two materials
behave in a very different way producing what is generally
known as a PN Junction.
When the N and P-type semiconductor materials are first
joined together a diffuusion phenomena occurs.
The free electrons from the N-type impurity atoms begin to
migrate across this newly formed junction to fill up the
holes in the P-type material
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Yrd. Doç. Dr. Aytaç13Gören
Semi Conductors
Semiconductor –
PN Junction
This process continues back and forth until the number of electrons which
have crossed the junction have a large enough electrical charge to repel
or prevent any more carriers from crossing the junction. Eventually a
state of equilibrium (electrically neutral situation) will occur producing
a "potential barrier" zone around the area of the junction This area
around the junction is now called the Depletion Layer.(gerilim seti)
This layer produces a
potential difference vallue
of for silicon about 0.6 - 0.7
volts and for germanium
about 0.3 - 0.35 volts.
This potential barrier will
always exist even if the
device is not connected to
any external power source.
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Yrd. Doç. Dr. Aytaç14Gören
Semi Conductors
PN Junction Diode
However, if we were to make electrical connections at the ends of both the
N-type and the P-type materials and then connect them to a battery
source.This additional energy source overcomes the barrier resulting in
free charges being able to cross the depletion region from one side to
the other.
The behavior of the PN junction with regards to the potential barrier width
produces an asymmetrical conducting two terminal device, better
known as the Junction Diode.
A diode is one of the simplest
semiconductor devices, which has the
characteristic of passing current in
one direction only
However, unlike a resistor, a diode
does not behave linearly with respect
to the applied voltage as the diode
has an exponential I-V relationship
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Yrd. Doç. Dr. Aytaç15Gören
Semi Conductors
Operation of a Diode
There are two operating regions for a diode: Forward biased and Reverse
biased.
When a diode is connected in
a Reverse Bias condition, a positive
voltage is applied to the N-type
material and a negative voltage is
applied to the P-type material.
When a diode is connected in
a Forward Bias condition, a
negative voltage is applied to the
N-type material and a positive
voltage is applied to the P-type
material.
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Diodes
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Diodes
(open door/closed door)
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Diodes
(more…)
Leds are
also diodes
which emit
light.
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Diodes
The power semiconductor diode, known simply as the Power Diode,
has a much larger PN junction area compared to its smaller signal
diode cousin, resulting in a high forward current capability of up to
several hundred amps (KA) and a reverse blocking voltage of up to
several thousand volts (KV). Since the power diode has a large PN
junction, it is not suitable for high frequency applications above
1MHz, but special and expensive high frequency, high current diodes
are available. For high frequency rectifier applications Schottky
Diodes are generally used because of their short reverse recovery
time and low voltage drop in their forward bias condition.
Ref: http://www.physics.sjsu.edu/becker/physics51/ac_circuits.htm
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Yrd. Doç. Dr. Aytaç Gören
Diodes
If an alternating voltage is applied across a power diode,
during the positive half cycle the diode will conduct
passing current and during the negative half cycle the
diode will not conduct blocking the flow of current. Then
conduction through the power diode only occurs during
the positive half cycle and is therefore unidirectional i.e.
DC as shown.
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Yrd. Doç. Dr. Aytaç21Gören
Half Wave Rectifier
Power diodes can be used individually as above or connected
together to produce a variety of rectifier circuits such as "HalfWave", "Full-Wave" or as "Bridge Rectifiers".
The input power supply may be either a single-phase or a multiphase supply with the simplest of all the rectifier circuits being
that of the Half Wave Rectifier. The power diode in a half wave
rectifier circuit passes just one half of each complete sine wave
of the AC supply in order to convert it into a DC supply. Then
this type of circuit is called a "half-wave" rectifier because it
passes only half of the incoming AC power supply.
Ref: http://www.electronics-tutorials.ws
Yrd. Doç. Dr. Aytaç Gören
Half Wave Rectifier
During each "positive" half cycle of the AC sine wave, the diode is forward
biased as the anode is positive with respect to the cathode resulting in
current flowing through the diode. Since the DC load is resistive (resistor,
R), the current flowing in the load resistor is therefore proportional to the
voltage (Ohm´s Law), and the voltage across the load resistor will
therefore be the same as the supply voltage,Vs (minus Vf), that is the "DC"
voltage across the load is sinusoidal for the first half cycle only
soVout = Vs.
Ref: http://www.electronics-tutorials.ws
Yrd. Doç. Dr. Aytaç Gören
Half Wave Rectifier
During each "negative" half cycle of the AC sine wave, the diode
is reverse biased as the anode is negative with respect to the cathode
therefore, No current flows through the diode or circuit. Then in the
negative half cycle of the supply, no current flows in the load resistor as
no voltage appears across it soVout = 0.
Ref: http://www.electronics-tutorials.ws
Yrd. Doç. Dr. Aytaç Gören
Half Wave Rectifier
The current on the DC side of the circuit flows in one direction only
making the circuit Unidirectional and the value of the DC
voltage VDC across the load resistor is calculated as follows.
Where Vmax is the maximum voltage value of the AC supply, and VS is
the r.m.s. value of the supply.
Ref: http://www.electronics-tutorials.ws
Yrd. Doç. Dr. Aytaç Gören
Half Wave Rectifier with Smoothing Capacitor
When rectification is used to provide a direct voltage power supply from
an alternating source, the amount of ripple can be further reduced by
using larger value capacitors but there are limits both on cost and size. For
a given capacitor value, a greater load current (smaller load resistor) will
discharge the capacitor more quickly (RC Time Constant) and so increases
the ripple obtained. Then for single phase, half-wave rectifier circuits it is
not very practical to try and reduce the ripple voltage by capacitor
smoothing alone, it is more practical to use "Full-wave Rectification"
instead.
Ref: http://www.electronics-tutorials.ws
Yrd. Doç. Dr. Aytaç Gören
Full Wave Rectifier
In a Full Wave Rectifier circuit, two diodes
are used, one for each half of the cycle. A
transformer is used whose secondary
winding is split equally into two halves
with a common centre tapped connection,
(C). This configuration results in each
diode conducting in turn when its anode
terminal is positive with respect to the
transformer centre point C producing an
output during both half-cycles, twice that
for the half wave rectifier so it is 100%
efficient.
Ref: http://www.electronics-tutorials.ws
Yrd. Doç. Dr. Aytaç Gören
Full Wave Rectifier
The full wave rectifier circuit consists of two
power diodes connected to a single load
resistance (RL) with each diode taking it in
turn to supply current to the load. When
point A of the transformer is positive with
respect to point C, diode D1 conducts in the
forward direction as indicated by the
arrows. When point B is positive (in the
negative half of the cycle) with respect to
point C, diode D2 conducts in the forward
direction and the current flowing through
resistor R is in the same direction for both
half-cycles. As the output voltage across the
resistor R is the phasor sum of the two
waveforms combined, this type of full wave
rectifier circuit is also known as a "bi-phase"
circuit.
Ref: http://www.electronics-tutorials.ws
Yrd. Doç. Dr. Aytaç Gören
Full Wave Rectifier
As the spaces between each halfwave developed by each diode is
now being filled in by the other
diode the average DC output
voltage across the load resistor is
now double that of the single halfwave rectifier circuit and is
about 0.637Vmax of the peak
voltage, assuming no losses.
Ref: http://www.electronics-tutorials.ws
Yrd. Doç. Dr. Aytaç Gören
Using Diode Bridge Rectifier
Another type of circuit that produces the
same output waveform as the full wave
rectifier circuit is that of the Full Wave
Bridge Rectifier. This type of single phase
rectifier uses four individual rectifying
diodes connected in a closed loop
"bridge" configuration to produce the
desired output. The main advantage of
this bridge circuit is that it does not
require a special centre tapped
transformer, thereby reducing its size and
cost. The single secondary winding is
connected to one side of the diode bridge
network and the load to the other side.
Yrd. Doç. Dr. Aytaç Gören
Using Diode Bridge Rectifier
The four diodes labelled D1 to D4 are arranged in "series pairs"
with only two diodes conducting current during each half cycle.
During the positive half cycle of the supply, diodes D1 and D2
conduct in series while diodes D3 and D4 are reverse biased and
the current flows through the load as shown above.
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Yrd. Doç. Dr. Aytaç31Gören
Using Diode Bridge Rectifier
As the current flowing through the load is unidirectional, so the
voltage developed across the load is also unidirectional the same as
for the previous two diode full-wave rectifier, therefore the average
DC voltage across the load is 0.637Vmax. However in reality, during
each half cycle the current flows through two diodes instead of just
one so the amplitude of the output voltage is two voltage drops ( 2 x
0.7 = 1.4V ) less than the input VMAX amplitude. The ripple frequency
is now twice the supply frequency (e.g. 100Hz for a 50Hz supply)
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Yrd. Doç. Dr. Aytaç Gören
Typical Diode Bridge Rectifier
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Using Diode Bridge Rectifier
with Smoothing Capacitor
The smoothing capacitor converts the full-wave
rippled output of the rectifier into a smooth DC
output voltage. Generally for DC power supply
circuits the smoothing capacitor is an Aluminium
Electrolytic type that has a capacitance value of
100uF or more with repeated DC voltage pulses
from the rectifier charging up the capacitor to
peak voltage. However, there are two important
parameters to consider when choosing a suitable
smoothing capacitor and these are its Working
Voltage, which must be higher than the no-load
output value of the rectifier and its Capacitance
Value, which determines the amount of ripple
that will appear superimposed on top of the DC
voltage.
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Yrd. Doç. Dr. Aytaç Gören
Using Diode Bridge Rectifier
with Smoothing Capacitor
As a general rule, we are looking to have a ripple
voltage of less than 100mV peak to peak.
Where: I is the DC load current in amps, ƒ is the
frequency of the ripple or twice the input
frequency in Hertz, and C is the capacitance in
Farads.
The main advantages of a full-wave bridge rectifier is that it has a smaller
AC ripple value for a given load and a smaller reservoir or smoothing
capacitor than an equivalent half-wave rectifier. Therefore, the
fundamental frequency of the ripple voltage is twice that of the AC supply
frequency (100Hz) where for the half-wave rectifier it is exactly equal to
the supply frequency (50Hz).
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Yrd. Doç. Dr. Aytaç Gören
Using Diode Bridge Rectifier
with Smoothing Capacitor
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Yrd. Doç. Dr. Aytaç Gören
Using Diode Bridge Rectifier with Smoothing Capacitor
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Yrd. Doç. Dr. Aytaç37Gören
7805 Voltage Regulator IC
Ref: http://www.ti.com/lit/ds/symlink/lm340-n.pdf
http://powersupplycircuit.net/lm7805.html
7805 Voltage Regulator IC
Ref: http://www.ti.com/lit/ds/symlink/lm340-n.pdf
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Yrd. Doç. Dr. Aytaç39Gören
7805 Voltage Regulator IC
SMPS Selection
What is the voltage and power of the system that you
will use it?
Voltage:
What is the DC voltage
needed to run your
machine/circuit?
Power:
DC P [Watt] = V [Volt] x I
[Ampere]
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