TT, You know diodes don't turn on and off, they pass current one direction only.
Diodes only conduct when they are forward biased. Feed them an AC input, with both positive and negative voltage swings, and they turn on and off at the cycle rate, enabling or blocking conduction, depending on the polarity of the voltage applied to them. And, they don't do it at the Zero crossings, but at the forward bias voltage points. The switching points are either plus or minus .7V away from the zero crossing point for standard silicon devices. To recover/convert the full sine wave on a single phase, you need two diodes for each phase, one is forward biased on the positive wave and the other is forward biased on the negative portion of the sine wave, so that most of the sine wave time period results in conduction at the output.
So, I have to disagree with you on this point. If you provide a silicon diode with a 0.5V Pk to Pk AC sine wave, it won't turn on and pass any current, apart from the very small leakage that may occur, as nothing is perfect.
Cheers,