Question

a simple zener diode shunt voltage regulator is to supply 12V to a load which normally draws a load current which varies from 0 to 50mA. the input voltage varies between 15V and 18V
1.1 CALCULATE the maximum rated current value of a zener device to be used .

Answer 1

Answer:

As per the given question,

R_{s}=\dfrac{18-12}{10\times 10^{-3}}=\dfrac{6}{10^{-2}}=600\OmegaRs=10×10−318−12=10−26=600Ω

Wattage of zenar diode (P)=VI(P)=VI

=12\times 10\times 10^{-3}=0.12 watt=12×10×10−3=0.12watt

Answer 2

solution:

let, I be the current through the  diode

     V be the voltage across the diode

and P be the power of the diode

here, current ( I ) varies between 0 to 50mA

so, I min =0mA and I max = 50mA = 50*10^-3A

here, voltage varies between 15V to 18V

so, V min = 15V and V max = 18V

now, to find power

P min = V min * I min

P min = 15*0

P min = 0

and  P max = V max *I max

P max = 18*50*10^-3

P max = 900*10^-3

P max = 0.9 watt

now,   the maximum rated current value of a  device

= P max / shunt voltage

= 0,9/12

= 0.075A