What exactly is a shunt voltage regulator? Both types of
regulators can be considered as "variable resistors". The series
regulators increase their resistance to lower the voltage on the
load. The shunt regulators decrease their resistance to divert
away current from the load. As a result, unlike the series
regulators, there has to be some resistance between the load /
shunt regulator and the voltage source. Because of that, most
high current regulators are series regulators. Vs. a zener, a
regulator, series or shunt, has much sharper knees, so their
output voltage is far less dependent on external factors.