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Power Supplies part 2, Thesis of Electronics

Tshwane University of TechnologyElectronics

Half wave and full wave rectifiers theory and description.

Typology: Thesis

2017/2018

Uploaded on 04/19/2018

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Module 2: Power Supplies
Engineering and the Built Environment / Electrical Engineering
Overview:
•Complete block diagram - Components
•Transformer –V/I/N, Rating [Part 1]
•Diode
Semiconductor Theory
Applications
Special Purpose diodes (Self-Study) [Part 2]
Rectification
•Half-Wave [Part 3]
•Full-Wave [Part 4]
•Filtering [Part 5]
•Regulation [Part 6]
•Power Supply Design [Part 6]
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Download Power Supplies part 2 and more Thesis Electronics in PDF only on Docsity!

Module 2: Power Supplies

Overview:

• Complete block diagram - Components

• Transformer – V/I/N, Rating [Part 1]

• Diode

 Semiconductor Theory

 Applications

 Special Purpose diodes (Self-Study) [Part 2]

 Rectification

• Half-Wave [Part 3]

• Full-Wave [Part 4]

• Filtering [Part 5]

• Regulation [Part 6]

• Power Supply Design [Part 6]

Module 2: Semi-conductor Theory

Outcomes

On completion, one should be able to:

• Discuss the basic operation of a diode.

• Basic structure of atoms.

• Insulators, conductors and semiconductors.

• Covalent bonding.

• Properties of N-type and P-type materials.

• Forward and reverse bias of a diode.

• Diode Models / Approximations

Part 2

Bohr Model

As seen in this

model, electrons

circle the nucleus.

Atomic structure

of a material

determines its

ability to conduct

or insulate.

Atomic Structure

The Valance shell determines the material’s ability to conduct

Conductors and Insulators

Certain atoms will combine in this way to form a

crystal structure. Silicon and Germanium combine this

way in their intrinsic or pure state

Covalent Bonding

The process of creating N-Type & P-Type materials is

called Doping.

Other atoms with 5 electrons such as Antimony are added to Silicon to increase the free electrons.

N-Type

Other atoms with 3 electrons such as Boron are added to Silicon to create a deficiency of electrons or hole charges. P-Type

N-Type & P-Type

Forward & Reverse bias

In this characteristic

curve we do not

consider the voltage

drop or the resistive

properties. Current

flow proportionally

increases with voltage.

Ideal Diode Characteristics

The voltage drop is not

the only loss of a

diode. In some cases

we must take into

account other factors

such as the resistive

effects as well as

reverse breakdown.

Complex Diode Characteristic Curve

  1. A series circuit consists of 15 v source, an ideal Silicon diode and a 390 Ω resistor. Calculate I (^) F, VR and VD when the diode is (a) Forward biased and (b) Reversed biased. Draw the circuit.
  2. A series circuit consists of a 10 V source, a silicon diode and a 2 kΩ resistor (R 1 ). Calculate the replacement value of R 1 to ensure that a diode current (I (^) D) of 1 mA will flow for each of the following cases: 2.1 Ideal diode 2.2 Practical diode 3.3 Complex diode (assume average resistance of 7 Ω.)
  3. Explain why a pn junction acts as a conductor when forward- biased

Exercise 1

Multiple-choice

  1. The depletion region of a forward-biased pn region is b (a) non existent (b) very narrow (c) wide (d) none of the above

  2. The two leads of a diode are known as the c (a) positive and negative (b) p and n (c) anode and cathode (d) forward and reverse

  3. The positive potential of an external source is connected to the d terminal of the forward-biased diode, with the negative polarity connected to the other terminal. (a) positive (b) negative (c)cathode (d) anode

  4. When a voltmeter is placed across a reverse-biased silicon diode, it will read a voltage approximately equal to b (a) 0, 7 V (b) the supply voltage (c) 0 V (d) the diode barrier potential

Exercise 2

 Describe the characteristics of a zener diode and analyze its operation

 Explain how a zener is used in voltage regulation and limiting

 Describe the varactor diode and its variable capacitance characteristics

 Discuss the operation and characteristics of LEDs and photodiodes

 Discuss the basic characteristics of the current regulator diode, the pin diode, the step-recovery diode, the tunnel diode, and the laser diode.

Module 2: Special Purpose Diodes

Outcomes

Zener Diode

A zener diode is much like a normal diode, the exception being is that it is placed in the circuit in reverse bias and operates in reverse breakdown. This typical characteristic curve illustrates the operating range for a zener. Note that its forward characteristics are just like a normal diode.

Varactor Diode

A varactor diode is best explained as a variable capacitor. Think of the depletion region a variable dielectric. The diode is placed in reverse bias. The dielectric is “adjusted” by bias changes.

Observe the voltmeter reading as the dielectric varies.