How do I regulate the output coming from a 50V transformer? At the filter's output, the transformer has 50*1.4142=70.7 volts. But this voltage of course drops as a load is applied, since the filter capacitor doesn't get a chance to charge fully.
70 volts is still manageable, as there are devices able to work at that voltage. But what if I want to do 60V DC. 80 V DC? Things start getting complicated there.
I think a 3-pin regulator is no longer suited for this. Probably a discrete zener diode + power transistor would work, but the regulation is not as good as a 3-pin device. Though, I don't mind this, as this is the supply for a closed-loop audio amplifier, which has good PSRR.
What if I wanted to do this with a buck converter? I'm familiar with the TPS40061. This device works with inputs 10 to 55V. Can a device like this be used with an auxiliary power supply, and regulate higher voltages?