2. JIWAJI UNIVERSITY,GWALIOR INSTITUTE OF ENGINEERING A SEMINAR PROJECT ON Submitted To:- Res Neetu Mam Submittedted By: Gaurav Priyadarshi (EL-09119) Durgendra Singh Kol (EL-09118) Chandarsen Bharti (EL-09114)

3. # Introduction. # Components required. # Components description. # Circuitry. # Working. # Application.

4. INTRODUCTION: The multi-output power supply evaluation board is a fully assembled and tested printed circuit board (PCB) that provides three step - down DC regulated output voltages 5V, 12V & one variable voltage 1.25V – 20V. It converts the AC (input ) in to 3 diffrent DC voltages. This low-cost, multipurpose power supply fulfils the requirements of almost all laboratory experiments. Nonetheless, it can be easily fabricated by hobbyist.

5. COMPONENTS REQUIRED  Resistor.  Transistor.  Capacitor.  Transformer.  LEDs.  Bridge rectifier.  IC LM317, IC 7812, IC 7805, IC 7912, IC7905, ( Voltage Regulators)

6. 1. Resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. The current through a resistor is in direct proportion to the voltage across the resistor's terminals. This relation is represented by Ohm's law. V=I.R

7. #A BI-POLAR transistor is a 3 terminal, 2 junction semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with 3 terminals for connection to an external circuit. It having three parts and these are: 1. Emitter. 2. Base. 3. Collector There are two types of BJT: NPN & PNP. In which, one p-type or n-type semiconductor is sandwitched between two n-type or p- type semicondutor respectively. So simply we can say that bipolar transistor is made of two p-n junction diode.

8. A capacitor is a passive two-terminal electrical component used to store energy in an electric field. construction consists of metal foils separated by a thin layer of insulating film (called dilectric). Capacitors are widely used as parts of electrical circuits in many common electrical devices. Capacitors may retain a charge long after power is removed from a circuit; this charge can cause dangerous or even potentially fatal shocks or damage connected equipment. In this device, capacitor is used as filter & this type of filter is called shunt capacitor filter.

9. A transformer is a static device which transfer ac electric power from one circuit to the other at same frquency but the voltage level is changed usually. A varying current in the first or primary winding creates a varyingmagnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF), or voltage, in the secondary winding. This effect is called inductive coupling. There are two types of transformer depending upon output voltage 1.Step up (voltage level is raised on output side) 2. Step down (voltage level is lowered on output size) STEP DOWN TRANSFORMER IS USED IN THIS DEVICE.

10. 5. LEDs LED: A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting.LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

11. A bridge rectifier is an arrangement of four diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input.When used in its most common application, for conversion of an alternating current (AC) input into direct current a (DC) output. A bridge rectifier gives pulsating dc output. A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from a transformer with a center- tapped secondary winding.

12. WHY BRIDGE RECTIFIER ?  A transformer without a center tap is used in bridge rectifier.  The current drawn in both the primary and Secondary of the supply transformer flows for the entire ac cycle and therefore a smaller transformer may be used in comparison with the full wave circuit of the Same output.  The bridge rectifier is suitable for high voltage application.  It has less PIV rating per diode.  It having lower cost & weight than full wave rectifier.

13. Voltage Regulator: A regulator is normally connected between filter and load. The aim of the regulator circuit is to maintain a nearly constant output voltage. IC LM317: Regulator LM317 generates variable power supply of 1.25 to 20 volt, 1 A. IC 7812 & IC 7912: Generates dual +12v & -12 volt, 1A power supply IC 7805 & IC 7905: Generates dual +5v & -5v, 1A power supply

14. CIRCUITRY…

15. WORKING OF POWER SUPPLY Transformer X1 steps down the mains power to deliver the secondary output of18V-0-18V.The transformer output is rectified by full-wave bridge rectifier BR1, filtered by capacitors C1, C2, C3, C7 and C8, and regulated by IC1 through IC5. Regulator IC1 (LM317) provides variable voltages (1.25 to 20V), while IC2 and IC4 provide regulated +12V and –12V, respectively. The output of IC2 is fed to regulator IC3 (7805), which provides fixed +5V. Similarly, the output of IC4 is fed to regulator IC5 (7905), which provides fixed –5V. Capacitors C4 through C6, and C9 through C11, are used for further filtering of ripples in positive and negative regulated power supplies.

16. LED1 glows to indicate that +5V is available, while LED2 indicates that –5V is available. Switch S1 is used for mains ‘on’/ ‘off’. Using switches S2 through S4, any of the three supplies can be independently turned off when not required in a particular experiment. This reduces unnecessary power dissipation and increases the life and reliability of the power supply. Since the circuit uses three terminal regulators, only capacitors are required at the input and output.

17.  The ripple factor y gives an idea about the waviness of the rectified voltage and is defined as the ratio of the effective value of AC component of voltage or current to the direct or average value.  Y= ripple voltage = rms value of ac component Dc voltage Dc value of wave ripple factor half wave = 1.21 ripple factor full wave rectifier = 0.48 ripple factor of bridge rectifier= 0.48 Ripple factor ‘y’

18.  The output voltage of an unregulated power supply varies due to: 1. Change in input supply voltage 2. Change in load resistance 3. Change in temperature.  The change in output voltage from no load to full load condition is called as voltage regulation  VR = V no load - V full Load *100 V full Load Smaller value of VR is usually beneficial Voltage Regulation

19. Application  Power Over Ethernet Powered Device / Receiver End Supply.  Multi-output Power Supply.  Used in Laboratory Experiment.  Used in home applances.  It can also be used as extension board and there is need of different voltage levels.