Power Supply Unit


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Power Supply Unit

  1. 1. KUSHAL, 091064 A2 BATCH, ECEJAYPEE UNIVERSITY OF ENGINEERING AND TECHNOLOGYPROJECT REPORT ON POWER SUPPLY UNIT AND ECM AMPLIFIER Under the guidance of Mr. GAURAV SAXENA Senior Lecturer Electronics and Communication Department JUET, Guna, M.P. Submitted by: KUSHAL 091064 A2, ECE
  2. 2. KUSHAL, 091064 A2 BATCH, ECE REGULATED POWER SUPPLYAIM:To implement and check Regulated Power Supply.REQUIRED APPARATUS AND COMPONENTS: To prepare the Copper track on the PCB • PCB Board of appropriate size to mount the circuit. • PCB cutter • PCB driller • FeCl3 Solution • Sand Paper To mount (Solder) the components on the PCB • Soldering paste • Soldering Wire • Soldering Machine Extra Apparatus • DMM • Ribbon Wire • Sharp cutter • Power Supply 6-30 Volts Components Required • One center tapped Transformer • One 1kΩ resistor • Three IN4007 diodes • Two Voltage Regulator ICs • IC 7805 - For +5V output • IC 7905 - For -5V output • Two 1000µF electrolytic capacitors and Two 0.1µF paper capacitors
  3. 3. KUSHAL, 091064 A2 BATCH, ECECircuit diagram:Component description and working:TRANSFORMER:Transformer is a major class of coils having two or more windings usually wrapped around acommon core made from laminated iron sheets. It has two cols named primary andsecondary. If the current flowing through primary is fluctuating, then a current will beinducted into the secondary winding. A steady current will not be transferred from one coilto other coil.
  4. 4. KUSHAL, 091064 A2 BATCH, ECETransformers are of two types: 1. Step up transformer 2. Step down transformerIn the power supply we use step down transformer. We apply 220V AC on the primary ofstep down transformer. This transformer steps down this voltage to 6V AC. We give 6V ACto rectifier circuit, which converts it to 5V DC.DIODE:The diode is a p-n junction device. Diode is the component used to control the flow of thecurrent in any one direction. The diode widely works in forward bias. When the currentflows from P to N direction, then it is in forward bias. The Zener diode is used in reverse biasfunction i.e. N to P direction. Visually the identification of the diode`s terminal can be doneby identifying he silver/black line. The silver/black line is the negative terminal (cathode)and the other terminal is the positive terminal (cathode).BRIDGE RECTIFIER:During the positive half cycle of the input supply, the upper end A of the transformersecondary becomes positive with respect to its lower point B. This makes Point1 of bridgePositive with respect to point 2. The diode D1 & D2 become forward biased & D3 & D4become reverse biased. As a result a current starts flowing from point1, through D1 the load& D2 to the negative end. During negative half cycle, the point2 becomes positive withrespect to point1. Diodes D1 & D2 now become reverse biased. Thus a current flows frompoint 2 to point1.
  5. 5. KUSHAL, 091064 A2 BATCH, ECECAPACITOR:Like a battery, a capacitor has two terminals. Inside the capacitor, the terminals connect totwo metal plates separated by a dielectric. The dielectric can be air, paper, plastic oranything else that does not conduct electricity and keeps the plates from touching eachother.VOLTAGE REGULATORS:Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or variable outputvoltages. The maximum current they can pass also rates them. Negative voltage regulatorsare available, mainly for use in dual supplies. Most regulators include some automaticprotection from excessive current (over load protection) and overheating (thermalprotection). Many of fixed voltage regulator ICs has 3 leads. They include a hole forattaching a heat sink if necessary.These voltage regulators are monolithic circuit integrated circuit designed as fixed voltageregulators for a wide variety of applications. These regulators employ internal currentlimiting, thermal shutdown, and safe-area compensation. With adequate heat sinking theycan deliver output current in excess of 1.0 A.EXPLANATION of how the POWER SUPPLY works:The main function of power supply is to convert AC to DC; as shown in fig 1, the first stage isto make full wave rectifier to the AC signals by using bridge rectifier, filter the rectified waveby using filtering capacitor and finally select the appropriate voltage signal to generate pureDC signal.Current rating for bridge rectifier should be suitable with load current, also; the designershould consider the voltage drop across each diode, which is normally equal to 0.7v. Notethat only two diodes are required when using Centre Tapped Transformer.The following formula is used to calculate the capacitance value for the filtering capacitor:C: Capacitor value.Vp: Peak voltage. ("Bridge output max voltage")f: Frequency of the AC supply.i: Load current.The figure is shown Below:
  6. 6. KUSHAL, 091064 A2 BATCH, ECE
  7. 7. KUSHAL, 091064 A2 BATCH, ECEPrecautions:1: Do the drilling properly.2: Iron should be kept in contact with the joint for 2-3 seconds.3: Put the components at correct place.4: Clean component lead and copper pad before soldering.