FULL WAVE RECTIFIER
welcome to this article, as we Learned about Half-wave rectifiers previously. Today we are going to study about Full Wave rectifiers and their types. so before going to start let me tell you if you have not learned my article on Half Wave rectifier so you must check out that you will understand the basics of rectifiers circuits. so let’s get started.
What is Rectifier Circuit?
A rectifier circuit is that circuit which performs conversion of AC voltages to DC Pulsating Voltages. So how this Rectifier Circuit Works? I mean how the Full Wave Rectifier circuits work? and why we use Full Wave Rectifier circuits? let’s start our discussion.
A Half Wave rectifier has some applications, the full-wave rectifier is the most commonly used type of dc power supplies. In this section, you will use what you learned about half-wave rectification and expand it to full-wave rectifiers. You will learn about two types of full wave rectifiers.
- Center-Tapped Full Wave Rectifier.
- Bridge Full Wave Rectifier.
Full Wave Rectifier Operation:
A Full Wave rectifier allows current in unidirectional (one-way) through the load during the entire of the input cycle, whereas a half-wave rectifier allows current through the load only during one-half of the cycle. The result of full-wave rectification is an output voltage with a frequency twice the input frequency and that pulsates every half-cycle of the input, as shown in given picture below.
The number of +ve alternations that make up the full wave rectified voltage is twice that of the half-wave voltage for the same time interval. The average value, which is the value measured on a dc voltmeter, for a full-wave rectified sinusoidal voltage is twice that of the half-wave, as shown in the following formula:
Center-Tapped Full-Wave Rectifier Operation
A Center-Tapped rectifier is a type of full wave rectifier that uses two diodes connected to the secondary of a center tapped transformer, as shown in Figure given below. A Centre Tapped Transformer is one whose secondary number of turns are grounded to provide two isolate circuits in secondary of Transformer. Mostly the Word Centre Tapped is used whenever the circuit is grounded in its center.The input voltage of Centre Tapped Full Wave Rectifier is coupled through the transformer to the center-tapped secondary. Half of the total secondary voltage appears between the center tap and each end of the secondary number of turns as shown in given figure.
For a positive half-cycle of the input voltage:
The polarities of the secondary voltages are as shown in Figure (a). This makes forward-biases diode D1 and reverse-biases diode D2. The path for current is through Diode 1 and the load resistor, as indicated.
For a negative half-cycle of the input voltage:
The voltage polarities on the secondary are as shown in Figure (b). This makes reverse-biases D1 and forward-biases D2. The current path is through D2 and RL, as indicated. Because the output current during both the positive and negative portions of the input cycle is in the same direction through the load, the output voltage developed across the load resistor is a full-wave rectified dc voltage, as shown below.
Effect of the Turns Ratio on the Output Voltage
The output voltage of a center-tapped full-wave rectifier is always one-half of the total secondary voltage less the diode drop, no matter what the turns ratio.
Peak Inverse Voltage
Each diode in the full-wave rectifier is continuously changing from forward-biased and then reverse-biased. The maximum reverse voltage that a diode can handle is the peak secondary voltage Vp(sec). The peak inverse voltage across either diode in a full-wave center tapped rectifier is:
Bridge Full Wave Rectifier Operation
The bridge rectifier is a best full wave rectifier which uses four diodes that connected as shown in Figure below. When the input cycle is in going for positive alternation as shown in part (a), the diodes D1 and D2 are in forward-biased and they conduct current in the direction as shown. A voltage is generated across Load Resistor that looks like the +ve half of the I/P cycle. During this period of duration, diodes D3 and D4 are reverse-biased.
When the input cycle of bridge full wave rectifier is going in the negative cycle as in (b), the diodes D3 and D4 are also going in forward bias and they conduct current in the same direction through Load Resistor as during the +ve half-cycle. when the negative half-cycle is coming for the diode, D1 and D2 are going in reverse-biased. A full-wave rectified output voltage appears across RL as a result of this action.
Bridge Output Voltage
A bridge rectifier with a transformer-coupled input is shown in (a). During the +ve half-cycle of the secondary voltage, diodes D1 and D2 are forward biased. we are neglecting diode drop here. The same is true when D3 and D4 are forward-biased during the negative half-cycle.
As you can see in Figure (b), two diodes are always in series with the RL during +ve and -ve half-cycles. If these diode drops are taken into account, the output voltage is.
Peak Inverse Voltage for Bridge Full Wave Rectifier
Since the output voltage is ideally equal to the secondary voltage, If the diode drops of the forward-biased diodes are included as shown in Figure 2–40(b), the peak inverse voltage across each reverse-biased diode in terms of Vp(out) is
The Peak Inverse Voltage rating for Bridge Full wave rectifier’s diodes is less than that required for the center-tapped configuration. If we neglect the diode drop, the bridge rectifier requires diodes with half the PIV rating of those in a center-tapped rectifier for the same output voltage.
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