Question

A Zener diode regulator circuit

must

provide a constant voltage of 12V, across

a 250Ω load resistor. The circuit uses a 24V input DC source, a 12V Zener

diode and a 50Ω series resistance. Calculate the minimum acceptable power

rating of the Zener diode.

Answer 1

Total current in the circuit

$I=\frac{24-12}{50}=\frac{12}{50}=0.24A\\ V_z=12V\\$

Current in 250ohms resistor

$I_R=\frac{12}{250}=0.048A$

Current through zener diode is

$I=I_z+I_R\\ I_z=0.24-0.048=0.192A\\$

Minimum acceptable power is

$P_z=I_z\cdot V_z\\ P_z=0.192\cdot 12=2.304W$