Prepared by(Group no. 3): C. K. Pithawalla College Of Engineering And Technology. Subject: Electronic Devices And Circuits Topic: Rectifiers Prepared by(Group no. 3): Bharuchwala Zainab-140090111006 Sadriwala sherebanu-140090111050 Parekh Janki-140090111033 Rathod Axay-1511909 Kakadiya Kartik-1511915

Rectification: Rectification is the process of converting the alternating voltage or current into the corresponding direct(dc)quantity. The input to a rectifier is ac whereas its output is undirectional or dc. The electronic circuit which carries out rectification is called as rectifier.

Rectifiers: Rectifier is an electronic device which is used or converting an alternating(ac) voltage or current into unidirectional(dc) voltage or current.

Operation: A step down transformer 2. A rectifier The basic building blocks of regulated power supply are: A step down transformer 2. A rectifier 3. Filter 4. A voltage regulator A step down transformer is used to reduce the ac mains voltage to an adequately small voltage. This voltage is converted into a pulsating dc voltage by the rectifier. The pulsating dc voltage at the rectifier output is converted into a ripple free steady dc voltage by the filter circuit. The filtered dc voltage is then applied to a voltage regulator which tries to keep the dc output voltage constant even if the supply voltage fluctuations take place.

Classification of rectifiers: Rectifier circuits Full wave rectifier(FWR) FWR with center trapped transformer Full wave bridge rectifier Half wave rectifier(HWR)

Half wave rectifier(HWR): In half wave rectifier, the rectifier is the only during one half cycle of the ac supply. So output is produced only in that half cycle. The output is suppressed in the other half cycle. The conduction takes place only in one half cycle of supply, hence the name of this circuit is half wave rectifier.

Rectifier circuit:

Wave form for half wave positive half cycle: Where: Vdc, Vav - the DC or average output voltage, Vpeak, the peak value of the phase input voltages, Vrms, the root-mean-square value of output voltage.

Voltage regulation for HWR: Where, Vnl = average load voltage at no load Vfl = average load voltage at full load Ideally the load regulation should be 0% and practically it should be as low as possible .

Rectification Efficiency: But actually the RMS current flowing through the winding is only  . Rectification Efficiency: Ideally the conversion efficiency should be 100% and practically it should be as high as possible. Transformer Utilization Factor:

Disadvantages: Avantages : Applications: Due to the unidirectional current flow through the transformer, there is a possibility of core saturation. To avoid it, transformer size must be increased. Ripple factor is high(1.21) Larger filter components are required. Avantages : Simple construction. Less number of components are required to be used. Small size. Applications: In the eliminators for pocket radios or eliminators for walkman or in the low cost power supply.

Full wave rectifier: A full-wave rectifier converts the whole of the input waveform to one of constant polarity (positive or negative) at its output. Full-wave rectification converts both polarities of the input waveform to pulsating DC (direct current), and yields a higher average output voltage. Two diodes and a center tapped transformer, or four diodes in a bridge configuration and any AC source (including a transformer without center tap), are needed.

Waveforms for full wave rectifier:

The average and root-mean-square no-load output voltages of an ideal single-phase full-wave rectifier are: Voltage Regulation:

Rectification efficiency:   The maximum efficiency of a Full Wave Rectifier is 81.2%.  Transformer Utilization Factor   Transformer Utilization Factor, TUF can be used to determine the rating of a transformer secondary. It is determined by considering the primary and the secondary winding separately and it gives a value of 0.693.

Disadvantages: Advantages: Applications: Since PIV of the diodes is 2 Vm size of the diodes is larger and they are more costly. Cost of the center taped transformer is high. Advantages: Low ripple factor as compared to HWR. Better rectification efficiency. No possibility of transformer core saturation. Applications: Laboratory power supplies. High current power supplies. Battery charges. power supplies for various electronic circuits.

Full wave rectifier with centre taped transformer: In the case of centre-tap full wave rectifier, only two diodes are used, and are connected to the opposite ends of a centre-tapped secondary transformer as shown in the figure below. The centre-tap is usually considered as the ground point or the zero voltage reference point.

Bridge Rectifier: The disadvantages of the full wave rectifier such as high PIV and compulsory use of center tapped transformer are overcome in the bridge rectifier. A bridge rectifier uses 4 diodes that are connected in the form of a Wheatstone’s bridge. In a single half cycle only two diodes conduct. Consider the circuit diagram given below.

Waveform for Bridge rectifier:

Disadvantages: The number of diodes used is four instead of two for FWR. As two diodes conduct simuntaneously , the voltage drop increases and the output voltage reduces. Advantages: It requires a small size transformer. Centre tap transformer is not required. This makes the bridge rectifier cost effective. High average output voltage. Applications: Laboratory dc power supplies. High current power supplies. Battery charger. DC power supplies for various electronics circuits

THANK YOU