EMT 212 Analog Electronic II Chapter 6 Voltage

EMT 212 Analog Electronic II Chapter 6 Voltage Regulators

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

Introduction n 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 1. series and shunt regulator 2. switching regulator 1. 3 general configuration(step-down, step-up and inverting) n n 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. n 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. n Filter –using low-pass filter either capacitor filter or RC filter. The function is straighten the pulse dc voltage by eliminate the n ripple. n Voltage regulator -is the ability to establish a constant voltage reference.

Power Supplies n For example a 5 V regulated supply

Power Supplies Transformer u. Transformers convert AC electricity from one voltage to another with little loss of power. u. Transformers work only with AC and this is one of the reasons why mains electricity is AC. u. Step-up transformers increase voltage. u. Step-down transformers reduce voltage.

Power Supplies n 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 n Smoothing

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

Power Supplies n 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 400 m. W or 1. 3 W).

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. Line Regulation = Line Regulation= % 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 = The load regulation also can be expressed as a percentage change in output voltage for each m. A change in load current (%/m. A).