For the same transformer secondary voltage, which rectifier has the highest average output voltage?

A bridge rectifier uses the entire secondary winding of the transformer to produce its full-wave output. In contrast, a full-wave centre-tap rectifier only uses half of the secondary winding at any given time, resulting in an output voltage that is roughly half that of the bridge design for the exact same transformer. A half-wave rectifier also produces a significantly lower average output voltage because it only conducts during one half of the AC cycle, blocking the other half completely. Therefore, the bridge configuration maximizes the use of the transformer's full secondary voltage, producing the highest average DC output.