Zener Diodes can be used to produce a stabilised voltage output with low ripple under varying load current conditions. By passing a small current through the diode from a voltage source, via a suitable current limiting resistor (RS), the zener diode will conduct sufficient current to maintain a voltage drop of Vout.
How is Zener diode used as voltage regulator?
When the Zener diode is given reverse bias feedback, there is a small leakage current until it attains the breakdown voltage or a constant voltage. At this point, the current begins flowing seamlessly without any change in voltage. Therefore, the constant voltage helps Zener Diode as Voltage Regulator.