Zener diode as a voltage regulator

To work properly when reverse biassed, the silicon semiconductor used in the Zener diode has a p-n junction. There is a large variety of currents that can be applied to the reverse voltage and yet maintain a constant voltage across a wide range of currents. As a result of this property, it is employed in d.c. circuits as a Zener diode as a voltage regulator. The Zener diode’s principal job as a voltage regulator is to keep the supply voltage constant. In this case, we’ll state that the voltage stays constant at 5 V because of the Zener voltage. Computers, generators and alternators all need voltage regulators to regulate their output.

Zener diode as a voltage regulator?

There are several different types of voltage regulators. It effectively reduces the input voltage to the desired level and maintains that level throughout the supply. This ensures that the voltage does not drop even when a load is applied. There are two primary purposes for which the Zener diode as a voltage regulator is employed:

• To alter or control the voltage output
• To maintain a steady output voltage regardless of input voltage fluctuations.

Zener Diode explanation

The diode is protected from overheating by a series resistor in the circuit. DC positive terminal is connected to it. As a result, the reverse-biased can work even in the event of an outage. Diodes with lower power ratings aren’t used since they can be destroyed when reverse bias is applied over their breakdown voltage. The Zener diode current should always be the lowest when the minimum input voltage and the highest load current are applied.

Choosing a Zener diode with a voltage roughly equal to the load voltage (VZ = VL) is easy since the input and output voltages are known.

Avalanche and Zener effects

Anode to cathode current flow is possible when the Zener diode is forward biassed, which makes it act like any other silicon diode with a PN junction. In contrast to a typical diode, which inhibits current flow when reverse-biassed, the Zener diode begins to conduct with a current flowing in the opposite direction upon reaching a specified reverse voltage threshold.

Reverse voltage given to Zener diodes causes avalanche breakdown in the semiconductor depletion area, after which the diode generates current in order to limit the increase in voltage to a predetermined level. Free electrons collide with nearby atoms, creating electric charges, which leads to the generation of heat and the potential for permanent damage to the device. When a diode has a depletion area that is very thin and heavily doped, a reverse current can be generated as a result of the development of a high-intensity electric field at the junction of the diode. Zener breakdown is reversible and does not harm the diode throughout this process. 

When the voltage on the Zener diode stabilises at a certain point on the horizontal axis, this point is known as the Zener voltage (VZ) and its value can range from a few volts to a few hundred volts. It is possible to precisely adjust the slope of the conduction curve and the minimal reverse current value from which the process is initiated during doping and diode manufacture. 

Standard Zener Voltages

Zener diodes are available in voltages ranging from little over 1 volt to a few hundred volts on the market today. From slightly under 1 W to over 5 W are typically available for each voltage setting that is offered. The BZX55 small signal series of Zener diodes has VZ voltages ranging from 2.4 V to 75 V and a maximum power of 500 mW, making it one of the most prevalent Zener diode families. Another popular Zener power diode is the BZX85, with voltages between 2.7V and 100V (VZ) and 1,300mW (maximum current).

Zener Breakdown

Because of Zener Breakdown, Zener diodes work. When a P-N junction is narrowed, electrons can tunnel through the depletion zone to the other side of the junction if a sufficient voltage is applied. Due to the electron’s dual nature, tunnelling is a quantum mechanical event. Electrons are described as wave functions rather than as basic ‘particles’ in quantum mechanics. They’re dispersed around the cosmos, with a chance of encountering one of them at some point. Electron tunnelling over a barrier like the depletion area is possible because of the chance that an electron can break through the barrier. When the electric potential difference across the Zener diode is large enough, an electron has a much better probability of tunnelling across the barrier, which is how Zener breakdown happens.

Advantages of zener diode

• Dissipation power is really high.
• High precision
• Small in size 
• Low cost

Applications

• As a voltage reference, it is frequently employed.
• Shunt regulators and voltage stabilizers employ Zener diodes.
• In switching processes, Zener diodes are employed.
• Clipping and clamping circuits use Zener diodes, which are sometimes referred to as zeners.
• Protection circuits rely on Zener diodes.

Characteristics of Zener Diode

Typical diodes have a forward bias and operate in the same manner as their name suggests. An enormous forward current flows through them, although there is virtually little voltage drop. Reverse biassed operation of a common diode results in negligible current flow until the voltage across the diodes is greater than the reverse breakdown voltage. The diode may be destroyed if a significant current travels through the junction. In this case, the Zener diode is the best solution. Reverse biassing a Zener diode ensures that it will not be harmed even if the voltage applied across it exceeds the value required for reverse breakdown.

Conclusion 

Zener diodes are available in a wide range of voltages, some of which are adjustable. This is known as the Zener effect, after Clarence Zener, because electron quantum tunnelling happens in the narrow gap between the p and n regions of a Zener diode, resulting in reverse conduction. Electronic devices of various kinds rely on Zener diodes, which are the building blocks of electronic circuits.They are, for example, used to generate low-power stabilised supply rails from a higher voltage and to provide reference voltages for circuits, notably stabilised power supplies. Overcurrent and electrostatic discharge can also be prevented by using these devices (ESD). Zener diode as a voltage regulator because this diode is designed in such a way that despite the increase in voltage, the circuit can break down and continue the flow of current in the opposite direction.