Problems on Zener Diode as Voltage Regulator

We all use mobile phones

The adapter of the mobile phone gives only 5 volts constantly.

To maintain the voltage constantly, a voltage regulator is used.

A Zener diode is the basic component of a voltage regulator.

Let’s learn about the Zener diode.

Zener diode is a special purpose semiconductor diode.

Symbol of the Zener diode is as above.

Zener diode has 2 terminals namely, 1- Cathode 2- Anode

Zener diode is specially designed to work as a voltage regulator.

Let’s see how a Zener diode works as a voltage regulator.

To get a constant DC voltage from the unregulated output of the rectifier, We use a Zener.

And when the voltage crosses breakdown voltage Vz, voltage starts to saturate even if current changes.

So, for any change in current, the voltage across Zener remains the same.

Hence, Zener diode acts as a voltage regulator.

Now, let’s see a problem with Zener as voltage regulator.

Problem: A $5 V$ DC stabilized power supply is required to be produced from a $12 V$ DC power supply.

The maximum current of the Zener $I_{z}$ is $400 m A$ . Then we have to find the minimum value of the series resistor $R_{s}$ .

Solution: We have a formula for $R_{s}$ as, $R_{s} = \frac{V _{s} - V _{z}}{I _{z}}$

And $V_{s} = 12 V$ $V_{z} = 5 V$ $I_{z} = 400 m A$

Therefore, $R_{s} = \frac{V _{s} - V _{z}}{I _{z}}$ $= \frac{1 2 - 5}{4 0 0 m A}$

Solving further we get, $= \frac{1 2 - 5}{4 0 0 m A}$ $= 175 Ω$

Therefore, finally, we get the value of $R_{s}$ , $R_{s} = 17.5 Ω$

Revision

Zener diode is a special purpose semiconductor diode.

Zener diode is fabricated by combining heavily doped p and n-type semiconductors.

Zener diode in reverse bias works as a voltage regulator.

The End