modified 9 years ago

Simple zener voltage regulator

01:01:19

Art of ELectronics 3rd ed. Exercise 2.6

Design a +10V regulated supply for load currents from 0 to 100mA; the input voltage is +20-+25V. Allow at least 10mA zener current under all (worst-case) conditions.
What power rating must the zener have?

1. Calculate R

Iout(max) < (Vin(min) - Vout)/R

0.1 < (20-10)/R

R < 100Ohm

2. What power rating must the zener have?

Pzener = ((Vin-Vout)/R - Iout)*Vzener

For worst case:
Vin = 25V
Vout= 10V
Iout = 0A (no load)
Vzener = 10V

Pzener =( (25-10)/R - 0)*10
Pz=150/100=1.5W

published 9 years ago

BillyT

9 years ago

The zener resistor needs to be 91 ohms, and who messed with the zener characteristics?

nemethakos

9 years ago

Show your calculations!

BillyT

9 years ago

I was not allowing for those zener characteristics when I said 91ohms.

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