D. Explain ripple voltage and how a passive capacitor circuit is used to reduce the effect. Given a full-wave bridge rectifier schematic, calculate the ripple voltage. Simulate the circuit and record the unfiltered and filtered response of the bridge. Compare the results to the calculated values. a. Explain the cause of ripple voltage and how a capacitor can reduce its effect. Ripple voltage is due to insufficient suppression of the AC input within the power supply. A large ripple means less effective filtering and a small ripple means effective filtering. When a capacitive filter is used, it provides a source voltage for the load during the discharge (or non- conduction) period .
b. Given the following circuit, assuming that V dc approximately equals V pk , calculate the expected ripple voltage. V ac ( rated ) = V S N S N P = 120 V ( 1 10 ) = 12 V V S ( PK ) = V ac ( rated ) 0.707 = 12 V 0.707 = 17 V V L ( PK ) = V S ( PK ) − 1.4 V = 17 V − 1.4 V = 15.6 V I L = V DC R L = 15.6 V 120 Ω = 130 mA V r = I L t C = ( 130 mA )( 8.33 mS ) 470 uF = 2.3 mVpp 2.3 V c. From Doc Sharing, week 1 download the Multisim PS2.ms Multisim file or create the circuit. Simulate the circuit without the capacitor connected and record the ripple voltage. Connect the capacitor and repeat the simulation. r V : _7.8V_________ (without capacitor)
r V : _2.3mVpp____ (with capacitor) check d. Describe the effect of the capacitor on the ripple voltage. The ripple voltage decreases when the capacitor is connected. The capacitor stores energy during the conduction period and delivers this energy to the load during the non-conduction period. This increases the time the current flows through the load and the ripple is considerably reduced. The higher the capacitance value, the lower the ripple. However if a capacitor is installed with too high capacitance then it will cause a surge current problem within the power supply. E. Discuss the operation of a voltage regulator IC. Identify the operating parameters from the data sheet. a. Locate the data sheet for a LM7805 voltage regulator and determine its pin configuration, current and voltage rating. Package Drawing and pin configuration: Maximum Ratings and Electrical Characteristics: Input Voltage ( I V ): __35V________ Output Voltage ( O V ): _5V(max=5.2V)_________ Quiescent Current ( Q I ): _5mA(max=8mA)_________
F. Simulate a full-wave bridge regulated power supply. Measure, and record the output voltages of the transformer, bridge rectifiers and regulator . a. From Doc Sharing, week 1 download the Multisim PS3.ms file or create the circuit. b. Simulate the circuit and record the following values. ( ) P pk V : _197V________ ( ) S pk V : _9.9V________ ( ) L pk V : _8.5V________ ave V : __5V_______ REG V : Not sure how to measure this. This should be a near pure DC voltage. You would have to be careful setting up the oscilloscope to measure this. You can used your DMM set to volts DC.
G. Explain the operation of a full-wave bridge rectifier.
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- Spring '11
- Direct Current, power supply, Rectifier, ripple voltage