Download voltage regulators 1

EMT212
Analog Electronic II
Chapter 6
Voltage Regulators
SYLLABUS

Introduction
 Power supplies
 Voltage regulation
 Types of regulators
• Series Regulators
• Shunt Regulators
• Switching Regulators

Integrated Circuit (IC) Voltage Regulators
 Regulator Application
Introduction



Voltage regulator function is to provide a constant dc output
voltage.
Input voltage may come from rectifier ac voltage or from a
battery.
Voltage regulator part of dc power supply and can divide into
two categories:
1. linear regulator
– series and shunt regulator
2. switching regulator
– 3 general configuration(step-down,step-up and
inverting)


The popular voltage regulator IC is three terminal +ve and –
ve which can be fixed output or variable output.
Switching regulators are also widely used and more efficient
than linear regulators.
Power Supply



Transformer –to step up or step down ac voltage amplitude. Also
isolate secondary from primary power earth line and noise.
Rectifier –three types half-wave, full-wave and bridge. The
function is to convert from ac voltage to dc voltage. The output is
pulse dc voltage with ripple voltage.
Filter –using low-pass filter either capacitor filter or RC filter. The
function is straighten the pulse dc voltage by eliminate the
ripple.

Voltage regulator -is the ability to establish a constant voltage
reference.
Power Supplies

For example a 5V regulated supply
Power Supplies
Transformer
Transformers
convert AC electricity from one
voltage to another with little loss of power.
Transformers work only with AC and this is
one of the reasons why mains electricity is AC.
Step-up transformers increase voltage.
Step-down transformers reduce voltage.
Power Supplies

Rectifier
Produces full-wave varying DC.
A bridge rectifier can be made using four individual
diodes,
but it is also available in special packages containing the
four diodes required.
Power Supplies

Smoothing
Power Supplies

Regulator
Voltage regulator ICs are available with fixed
(typically 5, 12 and 15V) or variable output voltages.
Power Supplies

Regulator
- 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 as shown in the diagram.
Zener diodes are rated by their breakdown voltage Vz and
maximum power Pz (typically 400mW or 1.3W).
Voltage Regulation
Line regulation is a measure of the effectiveness of a
voltage regulator to maintain constant dc voltage output
despite changes in the supply voltage.
It is define as a percentage(%) change in output
voltage for a change in input voltage.
 Vout
Line Regulation = 
 V
in

Line Regulation=


100% %

ΔVout/Vout 100% %/V
ΔVin
Can be
expressed in
units of %
Also can be
expressed in
units of %/V
Voltage Regulation
Load regulation is a measure of the ability of
regulator to maintain constant dc Vout despite
changes in load current due to a varying load
resistance.
Ideally the load regulation is 0 %, and the formula is:
Load Regulation =
 VNL  VFL


VFL



100%

The load regulation also can be expressed as a
percentage change in output voltage for each mA
change in load current (%/mA).