yo peoples ive got to have at least 1.5 A available to a certain chip and to reach the required Voltage over the chip Im going to have to use a voltage doubler from a transformer supplying me with 12Vac and between 50VA and 300VA. So I just wanna know if it is OK to use a doubler with high current rated (above 1.5A) diodes and then a high current rated regulator (also above 1.5A) to supply a nice 15 or 20 V with the required current capacity.
From what I have read before, a voltage multiplier will simply not do for supplying a high amount of current because, in a sense, the current that you are drawing is from the capacitors you are utilizing to double the voltage. If you draw too much current, the capacitors will discharge much more rapidly, and whatever voltage you are obtaining will decline because of the increased load and the time value for the capacitor to charge/discharge in relation to the frequency of AC. Voltage multipliers are typically utilized just for light current and stabilized loads.
In theory it should work, but ... (1) The current on the capacitors will have a lot of ripple. They will get hot and dry out faster. (2) The voltage on the capacitors can be up to 12*sqrt(2)*2=34V, add 10% grid tolerance and you get 37V peak. As input voltage that is cutting it very close for many regulators, specially for the low dropout regulators. (3) The regulator will have to dissipate a lot of power. A 300VA transformer may well be able to charge the caps to 34V each cycle, so dissipated power with a 1.5A/15V load will be 28W peak, and could be 20W average. I wouldn't do this for anything that requires any kind of reliability.
