This is just to understand the base concept of negative supply generation using the property of capacitor to block the DC level present in a signal. However this has a very bad efficiency since nearly half of the power is wasted. One cycle of the power is wasted. If better efficiency is required we should go for inductor based design. You can introduce a PI filter between load and output diode to reduce ripples even further. This is base principle for small current negative bias generators.
