A Zener diode is a semiconductor device made of silicon that allows current to flow in both directions. When a particular voltage is reached, the diode is specially designed to conduct in the other direction through an extensively doped p-n junction.

The reverse breakdown voltage of a Zener diode is well-structured, at which point it begins to conduct current and can operate in the forward or backward direction indefinitely without being destroyed. Furthermore, the power flow throughout the diode remains constant over a large voltage range, making Zener diodes an ideal voltage regulator.

Zener diodes are used in a wide range of applications.

• Zener diodes are used as voltage regulators.
• In wave shaping circuits, they are used as peak clippers.
• In transistor skewing circuits, as a rigid support voltage.
• Zener diodes protect a device from harm caused by excess voltage.

What is a voltage regulator?

A voltage regulator is a component of an electronic device that supplies power and adjusts incoming current into the expected output type in terms of power type and voltage level. It is a part that maintains a consistent voltage under varied conditions while in operation. The regulator’s main function is to maintain a stable supply during the variation in power and voltage levels.

Zener diode explanation:

Working voltage — maximum and minimum current

The reverse breakdown voltage is called Zener voltage. Depending on the diode, this can range from 2.4V to 200V.

The maximum current can be anywhere between 200uA and 200A.

The minimal current required for the diode is between 5 and 10 milliamps.

Tolerance in voltage – usually 5%

Power dissipation — The power rating of a diode is its maximum power dissipation value, which comprises both the current that flows through it and the voltage across these. The popular power levels are 400mW, 500mW, 1W, and 5W. Surface-mounted diodes are commonly rated at 200mW, 350mW, 500mW, and 1W.

Packaging — Surface mount devices and leaded devices are used as separate devices or within integrated circuits.

Zener diodes as voltage regulators

A regulator is used to maintain a stable flow of voltage output to the connections on the particular load, despite the changes in the supply of current or changes in the voltage of the supply.

• A Zener diode regulates the supply and keeps it within the required parameters, below the Iz (minimum) points in the reverse breakdown region.

• It controls the current supply within the normal parameters when moving in forward direction.
• It lets the current move in the reverse direction as well when the supply level reaches beyond a particular level. This level is known as the Zener voltage level.
• The features of a Zener diode are the same as they are in any other form of diode regulators. 
• It features a constant flow of current across different variations of flow of supply.
• The job of a voltage regulator is to maintain a constant voltage level across a load despite fluctuations in the input power or current. 
• When the input supply is at minimum (Vin) and the load voltage is at maximum (IL), the resistor is so arranged that the supply through the Zener diode remains at Iz (min).
• For all other input voltage and load current combinations, a Zener diode conducts the excess current, maintaining a constant voltage across the load. 
• A Zener diode conducts the least current when the load current is the highest and the most current when the load current is the lowest.

Types of regulators

• Line regulation: Only the input voltage changes in this type of regulator since the series and load resistors are fixed. As long as the input power is over a certain threshold, the output voltage remains constant.
• Load regulation: The input voltage is fixed while the load resistance varies with this sort of regulator. As long as the resistor is kept above a certain level, the output voltage remains constant.

A Zener diode’s reverse breakdown occurs in an area known as the Zener region. The voltage across the Zener diode remains constant in this region, while the current varies depending on the power supply. When a Zener diode is employed as a voltage regulator, it operates in this range.

Drawbacks of a Zener diode as a voltage regulator

• It is not a very efficient voltage regulator for large loads, owing to heavy loss of power in series resistors when there is heavy current.

• Minor change in output voltage with change load.

Conclusion

There is a tiny leakage current when a Zener diode is given reverse bias feedback until it reaches the breakdown voltage or a constant voltage. The current begins to flow without interruption at this point, with no change in voltage. So to conclude, if there is a constant voltage, then a  Zener diode’s function as a voltage regulator is quite efficient.