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Electrical Engineering

Comparision between half wave and full wave rectifier?

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January 20, 2012 7:56PM

A half wave rectifier conducts on every other cycle. The output is a train of half sine cycles, at a period equal to the input period. At 60 Hz, the period is 16.7 ms. Each half cycle (8.3 ms) will be interleaved with periods (8.3 ms) of no voltage. If you filter the output with a capacitor, you get DC - at no load, the DC will be the peak value less the forward bias voltage of the diode - at some load, the DC will fluctuate between that peak value and some value dependent on the size of the capacitor and the current draw. Again, the period (of this nearly sawtooth waveform) will be the input period.

A full wave rectifier conducts on every cycle. The output is a train of half sine cycles, at a period equal to half the input period. At 60 Hz, the period is 8.3 ms. Each cycle (8.3 ms) will be connected to the preceding cycle with no intervening delay. Each cycle will pulse in the same direction, instead of in alternating directions. If you filter the output with a capacitor, you get DC - at no load, the DC will be the peak value less the forward bias voltage of the diode - at some load, the DC will fluctuate between that peak value and some value dependent on the size of the capacitor and the current draw. Again, the period (of the nearly sawtooth waveform) will be half the input period.

Since the full wave output waveform is twice the frequency (half the period) of the half wave output, the capacitor can be about half its required value for the half wave circuit in order to achieve the same level of filtering.