Sunday, November 23, 2014

P N Junction Diode as Half Wave Rectifier

Rectifier is a device which converts alternate current into direct current.The PN junction diode can act like a rectifier. There are two types of rectifiers. One is a full wave rectifier and another one is a half wave rectifier.

Half wave rectifier :

The device which converts half of the input alternate current into direct current  is called a half wave rectifier. Then input is given generally from a step down transformer which has a primary and secondary coils and in between them there is a soft core. The output of the step down transformer is connected to a diode as shown in the figure. When the diode is in the forward biased the alternate current will be converted into direct current and when it is in the reverse biased it is not going to allow the current passing through it.

Anyway the converted direct current is not a complete direct current but still it will be having some sort of alternate current components. This is the reason why the output is still shown with the small kind of waves.To eliminate the remaining the alternate current we need to use filter circuit which is a combination of capacitors and resisters.

Efficiency means the ratio of portion of the output that is converted into direct current when compared with the input alternate current given. The half wave rectifier is theoretically supposed have efficiency of 50%. Anyway because of the remaining alternate current components and output it is having an efficiency close to 40.6% . This is also possible only  when  the diode in the forward bias. In that case, ideal diode offers zero resistance.

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