Diode as a rectifier

What is Rectifier

From the V-I characteristic of a junction diode, we have a tendency to see that it permits the current to pass only its forward bias. Current flows only during the forward-biased portion of the cycle when an alternating voltage is applied across a diode.

A rectifier is a device that converts alternate current to direction current using one or more contact diodes. It’s done by employing a diode or a bunch of diodes. Half-wave rectifiers use one diode, whereas a full-wave rectifier uses multiple diodes. A half-wave rectifier works by taking advantage of the fact that diodes only allow current to flow in one direction.

What is a rectifier?

From the V-I characteristic of a junction diode, we see that it permits the current to pass only its forward bias. Current flows only during the forward-biassed portion of the cycle when an alternating voltage is applied across a diode. 

Rectifier types

There are total 3 rectifier types

• Half wave rectifier

• Full way rectifier

•  diode bridge rectifier

Half wave rectifier

a whole half-wave diode rectifier circuit consists of three main parts:

1. An electrical device

2. A resistive load

3. A diode

The secondary of an electrical device provides the specified AC voltage across terminals A and B. Once the voltage at A is positive, the diode is forward biassed and it conducts. Once A is negative, the diode is reverse-biassed and it doesn’t conduct. The reverse saturation current of a diode is negligible and might be thought of as adequate to zero for practical purposes. (The reverse breakdown voltage of the diode should be sufficiently more than the height ac voltage at the secondary of the electrical device to guard the diode against reverse breakdown.)     

Therefore, within the positive half-cycle of AC, there’s a current through the load electrical device RL and we get an output voltage, whereas there is no current in the negative half-cycle. Within the following positive half-cycle, once more, we get the output voltage. As a result, while the output voltage varies, it is limited to only one direction and is stated to be corrected. Since the diode rectifier circuit is barely for half the input ac wave, it’s known as a half-wave rectifier.

Full-wave rectifier

The diode rectifier circuit victimisation of two diodes offers output-corrected voltage comparable to each positive in addition to negative half the AC cycle. Hence, it is called a full-wave rectifier. Here the p-side of the two diodes are connected to the ends of the transformer’s secondary. The diodes are connected along and therefore the output is taken between this common purpose of diodes and the centre of the transformer’s secondary. Thus, for a full-wave rectifier, the secondary of the electrical device is given a centre sound, so it’s known as a centre-tap transformer.

As frequently visible, the voltage corrected using each diode is slightly 1/2 of the complete secondary voltage. Each diode rectifies only 1/2 of the cycle, but the two accomplish that for trade cycles. Thus, the output between their not unusual place terminals and consequently the middle facet of the transformer will become a rectifier output. (Note that there is some other circuit of complete wave rectifiers that does not love a middle faucet transformer; however, it dreams of 4 diodes.) Suppose the enter voltage to A with appreciation to the middle faucet at any immediate is tremendous. It is clear that, at that instant, the voltage at B being out of the element is terrible. So, diode D1 receives ahead bias and conducts (at the same time as D2 being oppositely biassed isn’t always conducting). Hence, for the duration of this tremendous 1/2 of the cycle, we will be predisposed to get an output voltage (and an output voltage throughout the electric weight tool RL) in the path of the AC cycle, as soon as the voltage at A becomes terrible with the relevance middle faucet, the voltage at B could be tremendous. Thus, we will be predisposed to get output voltage at some point of every tremendous similarity due to the fact the terrible 1/2 of the cycle. Obviously, this may be a more excellent low-cost circuit for acquiring corrected voltage than the halfwave rectifier. 

The rectified voltage is within the style of pulses in the form of half sinusoids. Although it’s unidirectional, it doesn’t have a gradual value. To induce steady DC output from the pulsing voltage, ordinarily, a condenser is connected across the output terminals (parallel to the load RL). One can even use an inductance serial with RL for an equivalent purpose.

Ripple issue of half Wave Rectifier

‘Ripple’ is that the unwanted AC element remains once changing the AC voltage waveform into a DC waveform. Even supposing we have a tendency to attempt our best to get rid of all AC components, there’s still some touch left on the output aspect that pulsates the DC waveform. This undesirable AC component is termed ‘ripple’. We utilise the ripple factor (expressed by or r) to determine how successfully the half-wave rectifier will convert AC voltage to DC voltage. The ripple factor is a numerical relationship between the RMS value of the AC voltage (on the input side) and the rectifier’s DC voltage (on the output side).

Advantages of half-wave rectifier:

• Half wave rectifier could be a straightforward circuit.
• It’s an occasional cost.
• We are able to use it.
• we are able to simply construct.

Disadvantages of half-wave rectifier:

The electrical device utilisation issue is low.

They manufacture an occasional output voltage.

DC saturation of transformer core leading to magnetising current and additionally some physical phenomenon losses and generation of harmonics. 

The facility output and thus rectification potency are quite low. This can be because of the actual fact that power is delivered solely throughout the simple fraction cycle of the input alternating voltage.

Ripple factor is high and elaborate filtering is, therefore needed to relinquish steady dc output.

They only allow a half cycle through per sine wave and also the partner cycle is wasted. This results in power loss.

Conclusion 

A rectifier could be nothing but a straightforward diode that converts the electrical energy into direct current. A half-wave rectifier is one style of rectifier which converts the positive half cycle of the input into a right away current referred to as the output signal. But in this, we get a high ripple factor which means output is not completely DC.  This is the disadvantage of a half-wave rectifier. To convert full-cycle AC current into DC we need a full-wave rectifier.