This circuit was found in a 1969 Ferranti documentation. It can be implemented with modern equivalent transistors and diodes.
Mouser Electronics has in stock Texas Instruments Buck controllers LM5145 to operate with voltage...
This 80's circuit can be made with current comparators. Rectification accuracy is 1% DC up to 100...
Mouser Electronics counts in stock with the new TLV703 Low Dropout Voltage (LDO) Linear Regulators from Texas...