Car alternator and voltage regulator

[HighTechPower]

Hi. I'm new to car electronics. What I perceive after reading few websites that car alternator converts AC to pulsating DC using diodes. After that a mechanical relay type vibrating switch is used to stabilize DC output within battery voltage range. I can break my question as below,

What is the ac voltage of alternator before rectification.

Why don't we use DC-DC converter after diode rectification as voltage regulator OR why don't we use AC-DC converter, eliminating diode rectification, as voltage regulator.

 

[FvM]

Modern car alternators are synchronous generators, voltage is controlled by varying the excitation winding current, a very efficient method. Bridge rectifier is an appropriate method for AC/DC conversion. Consider that it can be simply integrated into the alternator. An active transistor rectifier could achieve slightly higher efficiency, but reduced reliability.

 

[treez]

The alternator acts as a current source...and the car battery clamps the voltage to 12V or so....if someone runs the car without the battery connected, then you get "automotive load dump" whereby 80V+ can potentially come from the alternator and damage electrical things in the car....because the battery is not there to clamp the voltage.