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# Half- wave and Full-wave Rectifiers.pptx

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# Half- wave and Full-wave Rectifiers.pptx

Half- wave and Full-wave Rectifiers

Half- wave and Full-wave Rectifiers

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### Half- wave and Full-wave Rectifiers.pptx

1. 1. Why do we need Rectifiers? Electrical gadgets like tube, light, fan and refrigerators run on 220V-50Hz main line ac. However, electronic equipment like radio, mobile charger and computer run on various values of dc voltages. Thus we need to be able to convert the ac voltage to various values of dc voltages based on our requirements. The process in which a simple harmonic a.c. voltage is converted into unidirectional voltage, is known as rectification and the circuit used for this conversion is called a rectifier. The property of a junction diode is used for rectification. Transformer is another important element to construct a complete rectifier.
2. 2. Transformer In most practical cases, it is required to either increase or decrease the ac voltage value. Such type of enhancement or decrement of ac voltage or current are conveniently achieved with different types of transformers. It is a passive device consisting of two closely wound and electrically isolated coils: primary and secondary. It works on the principle of Electromagnetic Mutual Induction. When current flows in the Primary Winding, it behaves as electromagnet. Thus an EMFisinduced in the Secondary winding as it comes in thearea having magnetic field lines due to primary winding.
3. 3. Working Principle The secondary voltage depends on the ratio of the number of turns (NP) in primary to the number of turns (NS) in secondary. If NS > NP , the secondary voltage becomes larger than the primary and the secondary current decreases by the same amount with respect to primary current. This configuretion is called step-up transformer. Use: the ac main is substituted by battery power (inverter, emergency light). If NS < NP , the secondary voltage decreases than the primary and the secondary current increases by the same amount with respect to primary current. This configuretion is called step-down transformer. Use: the battery is eliminated by ac main (radio, tape recorder).
4. 4. Use of Transformers in Rectifiers t Sin V v m P   The ac voltage applied to the primary of the transformer is assumed to be sinusoidal, thus can be expressed as: The amount of the stepped-down ac voltage across the secondary depends upon the number of secondary coil turns. The stepped-down sinusoidal voltage amplitude (Vm) is kept much larger than the diode cut-in voltage. Thus the voltage drop across the diode is often neglected.
5. 5. Piecewise Linear Model of Diode Although a diode is a non-linear device, yet for practical applications it is often approximated to be a linear device. This approximation model in which a non-linear device behaves as a linear one for a particular range of voltages is called the piecewise linear model of a non-linear device. The diode is assumed to be combination of three elements: a switch, a voltage source a resistor. When other resistances are large, the diode series resistance may be neglected.
6. 6. Half-wave Rectifier The ac voltage to be rectified is connected to the primary of the transformer. The diode D is connected in series with the secondary of the transformer. The other end of the diode D is connected to a load resistance RL and the other end of the resistance is connected to the other end of the transformer. HW
7. 7. Working Principle of Half-wave Rectifier
8. 8. Voltage & Current Waveforms of Half-wave Rectifier
9. 9. Average DC Voltage figure (1) (2) (3) (1)
10. 10. Root Mean Square Voltage (4) (5) (6) (4)
11. 11. Ripple Factor (15) (16) (16) (15) (17) (18)
12. 12. Center-tapped Transformer The tapping point is in the exact center of the secondary winding providing a common connection for two equal but opposite secondary voltages. With the center-tap grounded, the output VA will be positive in nature with respect to the ground, while the voltage at the other secondary, VB will be negative and opposite in nature, that is they are 180°out-of-phase with each other.
13. 13. Full-wave Rectifier Two diodes D1 and D2 are connected to the transformer secondary as shown in above figure. One diode gets forward biased in each half cycle of the input.
14. 14. Working Principle of Full-wave Rectifier
15. 15. Working Principle of Full-wave Rectifier
16. 16. Average DC Voltage (1) (23) (24) the figure /
17. 17. Root Mean Square Voltage (25) (26) (4) (26)
18. 18. Form Factor and Ripple Factor (30) (31) (28) (27) (13)
19. 19. Comparison of Full-wave and Half-wave Rectifier 0.572
20. 20. Bridge Rectifier An alternative implementation of the full-wave rectifier is bridge rectifier. It does not require center-tapped transformer. Four diodes are utilized instead of two. /
21. 21. Working Principle of Bridge Rectifier
22. 22. Working Principle of Bridge Rectifier
23. 23. Full-wave Rectifier Vs. Bridge Rectifier 0.572
24. 24. Disadvantages of Bridge Rectifier