Full Wave Rectifier:

A full wave rectifier is a type of rectifier which converts both half cycles of the AC signal into

pulsating DC signal. . It uses two diodes of which one conducts during one half cycle while the

other conducts during the other half cycle of the applied ac voltage.

Load voltage: VL(pk)= vs(pk)/2-0.7

The average (DC) output voltage is higher than for half wave rectifier.

Vavg= 2VL(pk)/pi or 0.637*VL(pk)

Some formula:

If the given value is in rms then convert it into Vp(pk) Vp(pk)=rms/0.707

Vs(pk)=Ns/Np*Vp(pk)

VL=Vs(pk)-Vf

But if the given value is rated then directly Vs is found by dividing the the value by 0.707.

Working:

During the positive half cycle of the input voltage, diode D1 becomes forward biased and D2

becomes reverse biased. Hence D1 conducts and D2 remains OFF. The load current flows through D1 and the voltage drop across RL will be equal to the During the negative half cycle of

the input voltage, diode D1 becomes reverse biased and D2 becomes forward biased. Hence D1 remains OFF and D2 conducts. The load current flows through D2 and the voltage drop across

RL will be equal to the input voltage.

Ripple Factor: Ratio of rms value of ac component to the dc component in the rectifier

output.

R.F=Iac/Idc

Ripple factor is very important in deciding the effectiveness of the rectifier. The smaller

the ripple factor, the lesser the effective a.c component and hence more effective is the

rectifier.

The output of the full wave rectifier has much less ripple than that of the half wave

rectifier producing a smoother output waveform.

R.F=0.482

Derivation:

The ripple factor for a Full Wave Rectifier is given by

The average voltage or the dc voltage available across the load resistance is

RMS value of the voltage at the load resistance is

Efficiency:

The ratio of dc power output to the applied input ac power is known as the

rectifier’s efficiency.

Dc power output/input ac power.

η max =0.812 = 81.2%

it is more efficient than half wave rectifier.

The maximum efficiency of a Full Wave Rectifier is 81.2%.

PIV:

peak inverse voltage (PIV) or peak reverse voltage (PRV) is the maximum value of reverse

voltage which occurs at the peak of the input cycle when the diode is reverse-biased.

Voltage Multipliers:

The voltage multiplier is an electronic circuit that delivers the output voltage whose amplitude

(peak value) is two, three, or more times greater than the amplitude (peak value) of the input

voltage.

OR

The voltage multiplier is an AC-to-DC converter, made up of diodes and capacitors that produce

a high voltage DC output from a low voltage AC input.

Voltage Multipliers are made up of many stages. Each stage is comprised of one capacitor and

one diode.

Depending on the output voltage, they can be of different types:

Voltage Doublers

Half wave voltage doublers.

Full wave voltage doublers.

Voltage Tipplers

Voltage Quadrupler.

1. Voltage Doublers It produces a dc voltage almost twice the rms value of the input ac voltage. They can

be of two types.

o Half wave voltage doublers.

o Full wave voltage doublers.

Half wave voltage doublers:

The half-wave voltage doubler circuit consists of two diodes, two capacitors, and AC input

voltage source.

Working:

The circuit diagram of the half-wave voltage doubler is shown in the below figure. During the

positive half cycle, diode D1 is F.B and allows current through it. This current will flows to the

capacitor C1 and charges it to the peak value of input voltage I.e. Vm.

However, current does not flow to the capacitor C2 because the diode D2 is R.B . So the diode D2

blocks the electric current flowing towards the capacitor C2. Therefore, during the positive half

cycle, capacitor C1 is charged whereas capacitor C2 is uncharged.

During negative half cycle:

During the negative half cycle, diode D1 is reverse biased. So the diode D1 will not allow electric

current through it. Therefore, during the negative half cycle, the capacitor C 1 will not be

charged. However, the charge (Vm) stored in the capacitor C1 is discharged (released).

On the other hand, the diode D2 is forward biased during the negative half cycle. So the diode

D2 allows electric current through it. This current will flows to the capacitor C 2 and charges it.

The capacitor C2 charges to a value 2Vm because the input voltage Vm and capacitor C1 voltage

Vm is added to the capacitor C2. Hence, during the negative half cycle, the capacitor C2 is

charged by both input supply voltage Vm and capacitor C1 voltage Vm. Therefore, the capacitor

C2 is charged to 2Vm.

Full wave doublers:

The full-wave voltage doubler consists of two diodes, two capacitors, and input AC voltage

source.

During positive half cycle:

During the positive half cycle of the input AC signal, diode D1 is forward biased. So the diode D1 allows electric current through it. This current will flows to the capacitor C1 and charges it to the

peak value of input voltage I.e. Vm.

On the other hand, diode D2 is reverse biased during the positive half cycle. So the diode D2 does not allow electric current through it. Therefore, the capacitor C2 is uncharged.

During negative half cycle:

During the negative half cycle of the input AC signal, the diode D2 is forward biased. So the diode D2 allows electric current through it. This current will flows to the capacitor C2 and

charges it to the peak value of the input voltage I.e. Vm.

On the other hand, diode D1 is reverse biased during the negative half cycle. So the diode D1 does not allow electric current through it.

Thus, the capacitor C1 and capacitor C2 are charged during alternate half cycles.

The output voltage is taken across the two series connected capacitors C1 and C2.

If no load is connected, the output voltage is equal to the sum of capacitor C1 voltage and capacitor C2 voltage I.e. C1 + C2 = Vm + Vm = 2Vm. When a load is connected to the output

terminals, the output voltage Vo will be somewhat less than 2Vm.

The circuit is called full-wave voltage doubler because one of the output capacitors is being charged during each half cycle of the input voltage.

Voltage tripler

The voltage tripler can be obtained by adding one more diode-capacitor stage to the half-wave voltage doubler circuit.

During first positive half cycle:

During the first positive half cycle of the input AC signal, the diode D1 is forward biased

whereas diodes D2 and D3 are reverse biased. Hence, the diode D1 allows electric current through it. This current will flows to the capacitor C1 and charges it to the peak value of the input voltage I.e. Vm.

During negative half cycle:

During the negative half cycle, diode D2 is forward biased whereas diodes D1 and D3 are reverse

biased. Hence, the diode D2 allows electric current through it. This current will flows to the

capacitor C2 and charges it. The capacitor C2 is charged to twice the peak voltage of the input signal (2Vm). This is because the charge (Vm) stored in the capacitor C1 is discharged during the

negative half cycle.

Therefore, the capacitor C1 voltage (Vm) and the input voltage (Vm) is added to the capacitor C2 I.e Capacitor voltage + input voltage = Vm + Vm = 2Vm. As a result, the capacitor C2 charges to

2Vm.

During second positive half cycle:

During the second positive half cycle, the diode D3 is forward biased whereas diodes D1 and D2 are reverse biased. Diode D1 is reverse biased because the voltage at X is negative due to charged

voltage Vm, across C1 and diode D2 is reverse biased because of its orientation. As a result, the voltage (2Vm) across capacitor C2 is discharged. This charge will flow to the capacitor C3 and charges it to the same voltage 2Vm.

The capacitors C1 and C3 are in series and the output voltage is taken across the two series

connected capacitors C1 and C3. The voltage across capacitor C1 is Vm and capacitor C3 is 2Vm. So the total output voltage is equal to the sum of capacitor C1 voltage and capacitor C3 voltage

I.e. C1 + C3 = Vm + 2Vm = 3Vm.

Therefore, the total output voltage obtained in voltage tripler is 3Vm which is three times more than the applied input voltage.

One alternative approach is to use a diode voltage multiplier circuit which increases or

“steps-up” the voltage without the use of a transformer. Voltage multipliers are similar

in many ways to rectifiers in that they convert AC-to-DC voltages for use in many

electrical and electronic circuit applications