# Full wave bridge rectifier & center tap rectifier

Full wave rectifier can be divide into two types. First is the full wave bridge rectifier and second is the centre tap full wave rectifier. In full wave rectifier we get same output voltage across the load resistor in same direction for both half cycle of ac input voltage.

In half wave rectifier we get the output of half cycle. Whereas in the full wave rectifier we have the output for both half cycle. That’s why we call it full wave rectifier.

The dc level of output voltage obtain from ac input can be improve 100% by using full-wave rectification.

#### Full Wave Bridge Rectifier

###### Construction:

In full wave bridge rectifier, there is four diode which form the bridge. The output is taken across the diagonally opposite sides. And ac input voltage is apply across the remaining diagonally opposite side as given in diagram.

###### How does a full wave bridge rectifier work?

From the circuit, we apply ac input voltage across point A and B. And then observing voltage across point C and D.

During the positive half cycle of ac input voltage,

• there is positive voltage at point A. And negative voltage at point B.
• Due to this Diode D2 and diode D3 are forward bias. And diode D1 and diode D4 are reverse bias.
• So current flow through positive terminal of supply via diode D2, load resistance R, diode D3 and then to negative terminal of ac input voltage.

During the negative half cycle of ac input voltage,

• there is negative voltage at point A. And positive voltage at point B.
• Due to this Diode D1 and diode D4 are forward bias. And diode D2 and diode D3 are reverse bias.
• So current flow through positive terminal of supply via diode D4, load resistance R, diode D1 and then to negative terminal of ac input voltage.

During both half cycle of ac input voltage, the polarity of output voltage across resistor R is same. And we get the output voltage for both input wave cycle in full wave bridge rectifier.

###### Peak inverse voltage of Full Wave Bridge Rectifier

Peak inverse voltage or peak reverse voltage is define as the voltage across the diode in reverse bias mode which does not exceed otherwise the diode will go in breakdown region and may get damage.

PIV => Vp means PIV must be greater than or equal to Vp.

• efficiency is double as compare to half wave rectifier
• average voltage or dc component of output voltage is double comparing to half wave rectifier
• No need of center tape transformer.
• Peak inverse voltage is half compare to center tape rectifier.

• It requires 4 diode which is more as comparing to center tap or half wave,
• in case of practical diode the internal voltage drop is more comparing to center tap rectifier.

#### Center tap full wave rectifier

Center tap rectifier consist of two diode D1 and D2 along with a center transformer to establish the ac input voltage.

###### working of Center Tap Full Wave Rectifier

From the figure,

During positive half cycle of the ac input voltage waveform

• there is positive voltage at point A and negative voltage at point C.
• so diode D1 is forward bias and diode D2 is reverse bias.
• which means current flow through diode D1, then resistor and then through the point B.
• and output voltage is appear across R resistor.

During negative half cycle of the ac input voltage waveform,

• there is negative voltage at point A and positive voltage at point C.
• so diode D2 is forward bias and diode D1 is reverse bias.
• which means current flow through diode D2, then resistor and then through the point B.
• and output voltage is appear across R resistor with same polarity as in case of positive half of input voltage.

So we get the output voltage during both the half cycle of input ac voltage with same polarity.

###### Peak Inverse Voltage Of center tap Full Wave Rectifier

Peak inverse voltage or peak reverse voltage is define as the voltage across the diode in reverse bias mode which does not exceed otherwise the diode will go in breakdown region and may get damage.

PIV => 2Vp means PIV must be greater than or equal to 2 times of Vp.

• efficiency is double as compare to half wave rectifier
• average voltage or dc component of output voltage is double comparing to half wave rectifier

• It require center tap transformer,
• Peak inverse voltage is double compare to full wave bridge rectifier.

#### Average voltage(Dc voltage) and AC voltage of output of full wave Bridge rectifier

The average voltage or the dc voltage of Full Wave Bridge Rectifier & Center Tap Rectifier is

AC value of output voltage is:

#### efficiency of full wave bridge rectifier and center tape rectifier

The efficiency of full wave rectifier is define as the ratio of dc power component to ac power component of output voltage.

Or efficiency equals to 81.2%.

#### Ripple Factor & Form Factor Of full wave Rectifier

The ripple factor of full wave bridge rectifier and center tap rectifier is the ratio of ripple voltage Vr to the average (dc) voltage.

we know Vdc = 0.636 Vp

and Vr = 0.308 Vp

hence r = 0.308 Vp / 0.636 Vp = 0.4843 or 48.43%

Form Factor of full wave rectifier ff = square root of ( r*r +1)

= 1.11

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