# Full wave Bridge Rectifier

#### Definition of Full Wave Bridge Rectifier:

The full wave Bridge Rectifier uses four diodes.  Where the input cycles is positive as in Part (a) Diagram, D1 and D2 are forward biased and conduct current.  A voltage is developed across RL that looks like the positive half of the input cycle .  During this time, diodes D3 and D4 are reverse biased.

Figure1: Action of Bridge Rectifier During Positive Half Cycle

##### Details Figure 1:

During the Positive half cycle of the input , the tow diodes of  Full wave bridge rectifier D1 and D2 are Forward Biased and conducts, we get output across RL . This was all about only Positive cycle of AC input wave.

Figure 2: Action of Bridge Rectifier During Negative Half Cycle

##### Details Figure 2:

During the negative half cycle, the diodes D3 and D4 of Bridge Rectifier are in Forward Biased, and other two diodes are reverse biased. So, only D3 and D4 conducts and we get output across the RL.

#### Bridge Output Voltages:

A bridge rectifier with a transformer coupled input is shown in figure 1, during the positive half cycle of the total secondary voltage, diodes D1 and D2 are forward biased.  Neglecting the diode drops, the secondary voltage appears across the load resistor.  The same is true when D3 and D4 are forward biased during the negative half cycle.

Vp (out) = Vp (sec)

As we can see in figure 2, two diodes are alsway in series tih the load resistor during both the positive and negative half cyles.  If these diodes drops are taken into account the output voltage is

Vp(out) = Vp(sec) – 1.4 V

#### Peak Inverse Voltage of Bridge Rectifier:

Let’s assume that diode D1 and diode D2 are forward biased and examine the reverse voltage across D3 and D4.  Visualizing D1 and D2 as shorts (ideal model) , we can see that D3 and D4 have a peak inverse voltage equal to the peak secondry voltage.  Since the output voltage is ideally equal to the secondry voltage.

PIV = Vp(out)

If the diode drops of the forward biased diodes are included as the peak inverse voltage across each reverse biased diode in terms of Vp(out) is

PIV = Vp(out) + 0.7V