A full-wave rectifier converts the whole of the input waveform to one of constant polarity (positive or negative) at its output. Full-wave rectification converts both polarities of the input waveform to DC (direct current), and is more efficient. However, in a circuit with a non-center tapped transformer, four diodes are required instead of the one needed for half-wave rectification. Four rectifiers arranged this way are called a diode bridge or bridge rectifier:
Gratz bridge rectifier: a full-wave rectifier using 4 diodes.
For single-phase AC, if the transformer is center-tapped, then two diodes back-to-back (i.e. anodes-to-anode or cathode-to-cathode) can form a full-wave rectifier. Twice as many windings are required on the transformer secondary to obtain the same output voltage compared to the bridge rectifier above.
Full-wave rectifier using a transformer and 2 diodes.
Full-wave rectifier, with vacuum tube having two anodes.
A very common vacuum tube rectifier configuration contained one cathode and twin anodes inside a single envelope; in this way, the two diodes required only one vacuum tube. The 5U4 and 5Y3 were popular examples of this configuration.
Three-Phase Bridge Rectifier.
3-phase AC input, half & full wave rectified DC output waveforms
For three-phase AC, six diodes are used. Typically there are three pairs of diodes, each pair, though, is not the same kind of double diode that would be used for a full wave single-phase rectifier. Instead the pairs are in series (anode to cathode). Typically, commercially available double diodes have four terminals so the user can configure them as single-phase split supply use, for half a bridge, or for three-phase use.
Disassembled automobile alternator, showing the six diodes that comprise a full-wave three-phase bridge rectifier.
Most devices that generate alternating current (such devices are called alternators) generate three-phase AC. For example, an automobile alternator has six diodes inside it to function as a full-wave rectifier for battery charging applications.
The average and root-mean-square output voltages of an ideal full wave rectifier can be calculated as:
- Vdc,Vav - the average or DC output volage,
- Vp - the peak value of half wave,
- Vrms - the root-mean-square value of output voltage.
- π = 3.141592653589793238462643383279...
- e = 2.7182818284590452353602874713527...
RECTIFIER wheather a full wave or a half wave converts ac into dc
but in full wave rectifier power wastage is less.