In electronics, engineers use electronic circuits, systems, and components to perform various functions by modifying electrical signals. The basic concept of electronics revolves around controlling the flow of electrons using different materials which control the electric current and perform various functions such as transmission, amplification of signals, information processing, and energy conversations. With advancement of technology, this process has become necessary as this principle is used in different electronic devices. Therefore, an engineer must know the basic electronic components.
The rapidly evolving electronics work on the principle of rectification. Rectification plays a pivotal role in developing electronic circuits. It is defined as:
“Conversion of two-dimensional alternating current into a single-dimension direct current is called rectification”
Many devices need to rectify AC current into simple DC output to work effectively. For the smooth working of applications, it is necessary to eliminate the negative half cycle of electric current.
Types of Rectification:
Electronic devices rectify input signals (AC) into output signals (DC). The signals can be rectified into two basic types, which are:
- Half Wave Rectification
- Full Wave Rectification
- Both these types of rectification work by altering the negative half cycle of alternating current.
- In a full wave rectifier, the negative half cycle of the input signal is fully rectified into the positive half cycle.
However, in a half-wave rectifier, the negative half-cycle is lost. Let us discuss the half-wave rectifier in detail
Half Wave Rectifier
A half-wave rectifier is the simplest form of a circuit. It performs its rectification function by allowing only half (positive) cycle of current to pass while blocking the other half (negative) cycle of current. The basic component of a half-wave rectifier is a “semiconductor diode”
Semiconductor diodes play an important role in electronic circuits. These provide voltage regulation, controlled regulation, signal demodulation, and other necessary functions of rectification. These have built-in ability to control the flow of electrons in specific directions. The most common composition of a semiconductor diode may be silicon or germanium.
If we are talking about a semiconductor diode, P-N Junction comes to mind. It is the most important example of a semiconductor diode.
P-N Junction
A P-N junction is a boundary formed when the crystal of silicon or germanium is grown in such a way that one side of the crystal becomes pentavalent (having a valency of five electrons) while the other side of the crystal becomes trivalent (having a valency of three electrons).
It has the following main sides:
- P-Side: the positive side which is doped with a type of impurity that creates excessive positive charge carriers (also called holes). The impurity is usually boron
- N-Side: the other side of the semiconductor diode is doped with an impurity which creates excess of electrons (i.e. negative charges). This is the N-side of a semiconductor diode. The impurity which is usually for creating an N-type semiconductor is phosphorus.
- Depletion Region: when the P and N sides of a semiconductor are formed, a boundary is created between them. This boundary is free from mobile charges (i.e. electrons and holes). This is due to neutralisation when electrons from the N side and holes from the P side diffuse into a region. This region establishes a potential across the junction which prevents further diffusion of charges.
Biassing of P-N Junction
A P-N Junction may be forward biassed or reverse biassed.
- Forward Biassing: when a battery is connected in such a way that the positive side of the battery is connected to the P side (positive side of a semiconductor diode), the flow of charges takes place and it works as a closed circuit. During this, depletion regions shorten allowing the passage of charges.
- Reverse Biassing: when a battery is connected so that the negative side of the battery connects to the N side (negative side of a semiconductor diode), there is a resistance on the flow of charges and it acts as an open circuit. During this, the depletion region widens and offers high resistance to the charges.
Working of a Half Wave Rectifier
In usual practices, the input of a half wave rectifier is an AC voltage, also called a sine wave.
Placement of Diode
A diode is connected with the input voltage in series. A load (which may be a device or a resistor working on DC) is applied. The diode placed will allow only the positive half cycle and block the negative half cycle.
Output Waveform
Whenever a signal is rectified by a half-wave rectifier, the output signal is in the form of pulsating DC voltage. It has only a positive component of input AC voltage. However, this output signal is not suitable for usage (since is it pulsating)
Ripple Voltage
The output pulsating DC voltage has a fluctuation in DC voltage, which is due to the periodic nature of AC voltage. This is termed as ripple.
DC Filtering
The output DC voltage is filtered by using special capacitors or inductors. These filter pulsating DC output into constant DC waveforms which can be smoothly run in electronics. The filter is used to keep the ripple factor as low as possible.
Benefits of Half Wave Rectifier
Half-wave rectifiers are widely used in electronics due to their simplicity. To achieve rectification, all we need is a simple diode which makes it a cost effective option to implement. For low-level students or beginners, half-wave rectifiers are great options since they allow understanding of straightforward and basic rectification concepts.
A half-wave rectifier is also used in different low-power applications where minimal power is required. It reduces voltage since the negative half cycle of AC input is lost. However, it also has drawbacks since half-wave rectifiers have a high value of ripple factor. As mentioned earlier, we have to use filters for the smooth running of DC devices.
The Bottom Line
Electronics play a vital role in communication, entertainment, healthcare, transportation, technology, etc. Therefore, it is advancing day by day. For the smooth evolution of electronics, it is necessary to understand the importance of rectifiers, an example of which is the half-wave rectifier. Thus for a unidirectional flow of current, half-wave rectifiers are a good option. Whenever we need a small amount of DC power, a wave rectifier comes to rescue.
