1. EMT212 Analog Electronic II
Chapter 6 Voltage Regulators

2. SYLLABUS Introduction Power supplies Voltage regulation
Types of regulators
Series Regulators
Shunt Regulators
Switching Regulators
Integrated Circuit (IC) Voltage Regulators
Regulator Application

3. 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:
linear regulator
series and shunt regulator
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.

4. 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.

5. Power Supplies
For example a 5V regulated supply

6. 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.

7. 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.

8. Power Supplies
Smoothing

9. Power Supplies Regulator
Voltage regulator ICs are available with fixed
(typically 5, 12 and 15V) or variable output voltages.

10. 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).

11. Voltage Regulation % Line Regulation = ΔVout/Vout Line 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. %
Line Regulation =
Can be expressed in units of %
Fig 18-1 lower regulator w/meters
ΔVout/Vout
ΔVin
Line Regulation=
100% %/V
Also can be expressed in units of %/V

12. 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 =
Fig 18-2 lower regulator
The load regulation also can be expressed as a percentage change in output voltage for each mA change in load current (%/mA).