Zener Diode As Voltage Regulator

A Zener Diode is an electronic component which can be used to make a very simple voltage regulator circuit.
This circuit enables a fixed stable voltage to be taken from an unstable voltage source such as the battery bank of a renewable energy system which will fluctuate depending on the state of charge of the bank.

As the input voltage increases the current through the Zener diode increases but the voltage drop remains constant - a feature of zener diodes.
Therefore since the current in the circuit has increased the voltage drop across the resistor increases by an amount equal to the difference between the input voltage and the zener voltage of the diode.

The constant reverse voltage of the zener diode makes it a valuable component for the regulation of the output voltage against both variations in the input voltage from an unregulated power supply or variations in the load resistance.
The current through the zener will change to keep the voltage at within the limits of the threshold of zener action and the maximum power it can dissipate