This ckt was suppose to use a LM555 as the source but settled w/ the pulse gen. set at 200khz (Volts at SLA BATT) Using the diodes and caps to charge and discharge at a certain rate along side w/ resistors to buffer the voltage to finally regulate at 20v.
Without the 5.6k at Zener (20v) would see some noise and have gone thru reverse brkdwn.
