The rectifier is a device which used to convert the alternating current (AC) into the direct current (DC). A Power diode used as a power electronic switch. A diode allows the electrical current to flow in only one direction. This process is known as rectification. For controlled rectifier Power BJT used as a switching device.
The output of the rectifier is not a pure sine wave, this waveform is known as the pulsating DC. If you need a pure sine wave, you have to use smoothing circuits. These smoothing circuits are known as the filters. If this pulsating DC used directly, it will lead to the poor performance of the device.
- The rectifiers used inside of the power supplies of electronics equipment.
- It used for detection of amplitude modulated radio signals.
- Rectifiers supplies polarized voltage for welding.
- It used to achieve fine control of traction motors.
- HVDC transmission line
- It used in firing circuits and pulse generating circuits.
- It used in the voltage multiplier, modulation, and demodulation circuit.
Rectifiers used to convert AC power into DC power. Hence, the input of the rectifier is AC power. There are two types of AC power, single-phase and three-phase. So, according to the power supply, there are two types of rectifier;
- Single-phase rectifier
- Three-phase rectifier
Further, the rectifiers classified according to the output waveform.
- Half-wave rectifier
- Full-wave rectifier
- bridge rectifier
- center-tap rectifier
Let’s discuss all types of rectifiers in brief. All circuit diagrams and waveforms simulated from the MATLAB.
In this type of rectifiers, the input supply is single-phase AC power. According to the output waveform, single-phase rectifier divides into two parts;
A) Single-phase half-wave
It is a simple type of rectifier which consists of only one power diode. For small power applications, this type of rectifier used. The circuit diagram is as shown in the below circuit.
In the positive half cycle of the power supply, the diode operates in the forward bias. Hence, it allows current to flow through the diode. In the negative half cycle of the power supply, the diode operates in the reverse bias. Therefore, it will not allow the current to flow through the circuit.
By this operation, the diode allows current only in the positive half cycle. So, the current across the load is an only positive half cycle. The output waveform is as shown in the above figure.
B) Single-phase Full-wave
In half-wave rectifier, it converts only in a positive half cycle of AC supply. In full-wave rectifier, it converts in positive and negative both cycle of the AC supply. There are two types of a full-wave rectifier.
In this type of rectifier, four diodes connected as shown in the below circuit diagram. In this rectifiers, at a time two diodes in forward bias and two diodes in reverse bias.
As per the circuit diagram, for a positive half cycle of the AC supply, diodes D1 and D3 in forward bias and diodes D2 and D4 are in reverse bias. So, the direction of current from the load is as shown in figure-5. for a negative half cycle of the AC supply, diode D2 and D4 in forward bias and diodes D1 and D3 are in reverse bias. In this condition also the direction of current across the load is not changed for a positive and negative half cycle of the AC supply.
Single-phase full-wave center-tapped
In this type of rectifiers, two diodes and one transformer connected as shown in the below circuit diagram. This transformer is center-tapped at the secondary winding. During the positive half cycle of AC input, diode D1 works as forward bias and diode D2 in reverse bias. The direction of the current from the load is as shown in the figure-6. During the negative half cycle of AC input, diode D2 is forward bias and diode D1 is in reverse bias. We can see from the below figure, the direction of current from the load is not change for the positive and negative half cycle of AC input.
When the input of the AC supply is three-phase, the rectifier used that is known as the three-phase rectifier. Similar to the single-phase rectifier, three-phase rectifier also divides into two parts according to the output waveform.
- Three-phase half wave
- Three-phase full-wave
This type of rectifiers used in industries where large load is connected. In HVDC transmission line this type of rectifiers used. The input of the device is three-phase AC supply. Hence, for this type of device three-phase AC supply needed.
Three-phase half wave
In three-phase half-wave rectifiers, three diodes connected with each phase of the three-phase AC supply. The three-phase rectifier is same as three single-phase rectifiers. Each diode operates (forward bias) for one-third cycle of AC input and the remaining two diodes remain as an open circuit (reverse bias). Circuit diagram and waveforms are as shown in the below figure.
Three-phase full wave
In full bridge rectifiers, six number of diodes used. As we have seen in the half-bridge rectifiers, only half cycle of AC supply converted into pulsating DC supply. But in case of the full-bridge rectifiers, both half cycles converted into pulsating DC.
Six diodes connected in the form of the bridge as shown in the circuit diagram. There are three arms. As per shown in the circuit diagram, upper diodes (D1, D3, and D5) connected with the positive terminal and lower diodes (D2, D4, and D6) connected with the negative terminal of the AC supply.
Circuit diagram and waveforms are as shown in the below figure.