Sunday, November 23, 2014

P N Junction Diode as Full Wave Rectifier

Full wave  rectifier is a device which converts complete alternate current into direct current. The input of this circuit is very similar to the half wave  rectifier.It is nothing but a step down transformer. In this kind of the device the output consists of not one diode but two diodes. In between the two diodes there is a special arrangement called central tap. The purpose of the central tap is to reverse the phase of the current that is passing through it. When the input is connected to both diode D1 and D2 it first passes to first diode and then to the second diode via central tap.

When the positive cycle of the alternate current is given like input ,diode D1 will be in forward bias. Before the same positive peak is passed to the diode D2, it is first of all passed to the central tap therefore it will reverse that positive peek into negative peak. Hence  the diode D2 will be simultaneously will be in reverse Bias.

When the Negative peak of the alternate current has reached the system, the diode D1 will be in reverse Bias. The same negative peak before reaching the diode D2 is passed to the central tap therefore it will be converted as positive peek. This is the job of the central tap which is managed with the help of the phase reversal. 

Thus the diode D2 will be in forward bias for the Negative peak of the alternate current that is reaching the circuit. All positive peaks are passed through the diode D1 and all negative peaks are passed  through the diode D2.Thus  all alternate current is converted into direct current.

Theoretically the full wave rectifier is supposed have an efficiency of hundred percent. Anyway as the output still contain some part of the alternate current components, it is not equal 100% and in the ideal case it is close to 81.2% as shown.

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