User Guide

The MOSFETs have a Yfs of ~2.3S. To increase current from 1.3A to 5A, it needs a Vgs of ~6.7V.
Add to this the voltage drop across the source resistor; that gives 9.1V. The normal DC voltage
across C3 is 11.4V. So in theory at least, this is sufficient.
Even after a few hundred cycles, simulations show that C3 does not lose voltage. And no current
flows through any of the 1N4148 diodes. Some input current is required though to drive against
R6//R7, but not unexpected.
So let’s be greedy and reduce load impedance further. This still seems to work down to 1.5R load,
when maximum current becomes 10A (and output drops to 15V). The Vg of the Q2 still does not
exceed the output voltage peak. So D3 does not conduct. Same applies to Q1 and D1. One can also
clearly see how the LM385 is conducting, keeping the current in the LED in check.
Fig. 1 20V in 10Hz into 4R