ZENER DIODE VOLTAGE REGULATOR
To design and set up a voltage regulator using Zener diode
COMPONENTS AND EQUIPMENTS
1. Bridge rectifier circuit
2. Zener diode (6.2 volt)
To get a 5.6 V as output, select SZ 5.6 as Zener diode .Take load current as 5 mA.
Load current =output voltage\output current
= 5.6/5 mA
= 1.1 K (use 1.2 K)
R1 is used to limit the current .Take 1 K resistor as R1.
Zener diode is a P-N junction diode specially designed to operate in the reverse biased mode. It is acting as normal diode while forward biasing. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. In the case of normal diodes the diode damages at the break down voltage. But Zener diode is specially designed to operate in the reverse breakdown region.
The basic principle of Zener diode is the Zener breakdown. When a diode is heavily doped, it’s depletion region will be narrow. When a high reverse voltage is applied across the junction, there will be very strong electric field at the junction. And the electron hole pair generation takes place. Thus heavy current flows. This is known as Zener break down.
So a Zener diode, in a forward biased condition acts as a normal diode. In reverse biased mode, after the break down of junction current through diode increases sharply. But the voltage across it remains constant. This principle is used in voltage regulator using Zener diodes.
1. Check the components using multimeter
2. Wire up and test a bridge rectifier circuit.
3. Wire up the regulator circuit
4. Apply the output of rectifier to the regulator
5. Now keep the input voltage constant and vary the rheostat at output. Note down the voltmeter and ammeter readings
6. Now take the voltmeter and ammeter readings by varying the input voltage
6. Plot the graphs for line and load regulation and find the values by taking the slopes of the graphs.
LINE REGULATION LOAD REGULATION
1. LINE REGULATION
2. LOAD REGULATION
Load regulation=Voltage at no load-Voltage at full load\Voltage at no load
Line regulation=Change in output\Change in input
A Zener voltage regulator was designed .Graphs were plotted. Line regulation and load regulation was calculated.
SAMPLE VIVA QUESTIONS
1. What is the basic principle of Zener diode?
2. What is Zener break down?
When a diode is heavily doped, it’s depletion region will be narrow. When a high reverse voltage is applied across the junction, there will be very strong electric field at the junction. And the electron hole pair generation takes place. Thus heavy current flows. This is known as Zener break down.
3. What is the break down voltage of Zener diode?
It is the reverse voltage at which break down of PN junction occurs