Halfwave and full wave rectificaton

this presentation describes the half wave rectification and full wave rectification of an AC signal and convert it into pulsating DC output voltage.

1. Half-Wave Rectification Course code: 402 Course title: Modern Physics & Electronics Course Incharge: Sehrish Inam, Lecturer Physics

2. What is Half-Wave Rectifier? A diode is connected to an ac source that provides the input voltage, V , and to a inload resistor, RL, forming a half-wave rectifier O n the positive half-cycle, the diode is forward biased and vice versa.

3. What is Half-Wave Rectifier? A  rectifier circuit   in which the half part of the cycle either positive or negative of AC is converted to DC is defined as the half-wave rectifier. If the positive half cycle is considered then the negative half cycle of the source gets blocked or if the negative cycle of the source is considered in that case positive cycle gets blocked.

4. Working of a Half-Wave Rectifier The circuit consists of a single diode in series with the AC supply and the load  resistor . As the sufficient supply is provided the diode converts AC to DC the resultant will be unidirectional by utilizing the half cycle of the supply .

5. Half Wave Rectification for Positive Cycle Consideration In positive half cycle sufficient amount of voltage reaches the diode resulting it to function in forwarding bias condition . The process of rectification occurs at the load resistance where the generated voltage in the circuit is consumed by the load. L oad resistor is to block the excess current produced in the circuit due to the diode. Here the positive side of the supply is considered so it is termed as a positive half-wave rectifier.

6. Half-wave Rectification for Negative Cycle Consideration Here the diode direction is changed so it begins to conduct during the applied negative supply of the voltage and the positive cycle gets blocked. The current produced in the circuit gets measured at the load resistor. The output generated consists of pulsating Dc but the intention of rectification is to produce constant DC .

7. Characteristics of Half Wave Rectifier

8. Characteristics of Half Wave Rectifier RMS Value of a Half-Wave Rectifier RMS is defined as the root mean square value. For load current, the RMS value can be given as I RMS  = I m /2 The RMS value of the output voltage  is given as V RMS  = I RMS  R L V RMS = Im /2 * RL

9. Characteristics of Half Wave Rectifier The efficiency of the rectifier is the ratio between the generated output power to the applied input power. E = P dc  / P ac The maximum efficiency produced is 40.6 %. Question: if input signal is being rectified half, then why the efficiency is not 50%?

10. Ripple Factor of a Half-Wave Rectifier The output produced consists of pulsating DC. P ulses in the output referred to as ripples. The number of ripples present at the output can be measured in terms of ripple factor . Ripple Factor, γ = (Ripple voltage at the output ) ( dc output voltage ) This ripple factor effects the practical implementation of half wave rectifier.

11. Advantages Requirements list of the components is less. The cost for the construction is low. Less number of components presence results in the construction of rectifier in the easiest manner. It is simple to analyze because the designed circuit is straight forward .

12. Disadvantages The output generated in this rectifier is in the form of pulses. The ripple factor is high. Results in the power loss of the circuit . The transformer utilization factor (TUF) of the half-wave rectifier is low. Here the output generated requires the filter to be connected across the load because of the ripples generated at the output voltage.

13. Applications The requirement of generating dc output voltage paves the way for the application of the half-wave rectifier circuit with the filter attached across the load. In the power supplies circuitry where the constant DC at the output is not considered as the major requirement at that case, the half-wave rectifier can be used.

14. Full Wave Rectifier Working and Its Applications Course code: 402 Course title: M odern Physics & Electronics Course Incharge: Sehrish Inam, Lecturer Physics

15. What is a Full Wave Rectifier ? A rectifier that utilizes both the positive and the negative half of the input cycle and undergoes rectification is defined as a full-wave rectifier.

16. Full Wave Rectifier Theory The full-wave bridge rectifier uses four diodes , as shown on the next slide For + ve input cycle (a), diodes D 1 and D 4 are forward-biased and conduct current, while diodes D 2 and D 3 are reverse-biased For – ve input cycle (b), diodes D 2 and D 3 are forward-biased and conduct current, while diodes D 1 and D 4 are reverse-biased

17. Full wave Rectifier

18. Types of Full Wave Rectifier The full-wave rectifier can be designed by using with a minimum of two basic diodes or it can use four diodes based on the topology suggested . F ull-wave rectifier can be classified into two types. They are (1) Center – Tapped A center-tapped full-wave rectifier circuit consists of two diodes, a transformer, and a resistive load .

19. Full Wave Rectifier Circuit for Center – Tapped A center-tapped transformer is a normal transformer that has a slight modification in it. Its secondary winding has a wire connected at the center. Hence the input supply AC voltage while passing through the secondary winding its voltage is divided into two halves. The one half is referred to positive half of the voltage. Whereas the remaining half of the voltage is for the negative part of the cycle.

20. Full Wave Rectifier Circuit for Center – Tapped The circuit consists of two diodes that are connected in parallel to each other along with the resistive load. The load is connected at the center-tapped wire of the secondary winding.

21. Full Wave Rectifier (Center- Tapped) working The input is provided to the center-tapped transformer as it reaches the secondary winding the voltage is divided into two halves. During the positive half of the input cycles, the diode D1 is in forwarding bias condition indicating the conducting mode and the diode D2 is in the non-conducting mode because it is in reverse bias condition. The flow of current is observed at the terminal of diode D1 .

22. Full Wave Rectifier Circuit for Center – Tapped During the negative half of the cycle, the diode D2 conducts because of the center-tapped transformer property and the diode D1 is in reverse bias condition that is in non-conduction mode. During this consequence the terminal at D2 one can find the flow of current through it and at D1 there is no evident flow of current or the current is blocked at D1 terminal.

23. Full Wave Rectifier Circuit for Center – Tapped Hence both the cycles are utilized here for rectification without any loss of input power. T he average output voltage of the half-wave rectifier is doubled compared to that of the half-wave rectifier.

24. (2) Full Wave Rectifier (Bridge ) A full-wave bridge rectifying circuit consists of four diodes connected in a diagonal manner that is nothing but in bridge topology . No center-tapped transformer is used .

25. Full-Wave Bridge Rectifier 1 4 2 3

26. Full Wave Bridge Rectifier Circuit The four diodes connected in a bridge form. D iagonally opposite diodes conduct during one half of the cycle. Second half the remaining two diode conducts.

27. Working of Full Wave Bridge Rectifier The diode D 1 and D 4 are diagonally opposite to each other whereas D 2 and D 3 are also connected in a diagonally opposite manner. During this the diodes D 1 and D 4 are in forwarding bias condition that is in conduction mode acts like closed switch then the path is established for the flow of current. Whereas diodes D 2 and D 3 are in reverse bias mode.

28. Full Wave Rectifier Circuit for Center – Tapped As the negative cycle of the supply reaches the bridge rectifying circuit diodes D 1 and D 4 becomes reverse bias and the diodes D 2 and D 3 act in forwarding bias mode. Hence the path is established for the flow of current between and D 3 . Where D 1 and D 4 diodes act like an open circuit and block the flow of current

29. Advantages The full-wave rectifier has more efficiency compared to that of a half-wave rectifier. There is the utilization of both the cycles. Hence there is no loss in the output power. As both the cycles used in rectification. There will be no loss in the input voltage signal. Ripple factor is less compared to that of the half-wave rectifier. Greater mean in DC value is achieved. Compare to the center-tapped full-wave rectifier bridge rectifier is cost-effective because the center-tapped is more costly.

30. Disadvantages The only disadvantage of this circuit is that the center-tapped transformer utilized here is costly. To overcome this disadvantage bridge rectifier circuit is constructed where the four diodes are connected in a bridge topology. 

31. Applications The amplitude for the modulating radio signal is detected using the full-wave bridge rectifier circuit. In electric wielding to supply steady DC voltage in a polarized way, this circuit is preferred. As the efficiency of rectification is high in this rectifier circuit, it is used in various appliances as a part of the power supply unit. It has the capability of converting high AC voltage to low DC value. In case of powering up of the devices like motors and LED devices these are used .