Javalab [Javalab] Lars Drud Nielsen
ldn@oersted.dtu.dk

Voltage regulator

The Zener diode is modelled as an ideal switch with a simple forward voltage drop, VD = 0.6 V, and no series resistance. The Zener (reverse) breakdown voltage, VZ, is adjustable, and also the breakdown current versus voltage has an infinite slope.

Observe that, for given settings of the three vertical components in the diagram, the optimal power transfer ratio from the source (> VZ) to the load is obtained by adjusting the resistance of the horizontal series resistor exactly to hit the breakdown point of the Zener diode. Larger series resistance values will result in a resistive voltage divider (IZ = 0) with a decreasing voltage fraction across the load. Smaller series resistance values will leave the load current unchanged but will increase the total current (IZ > 0).

Exercise: A voltage source is available with an output voltage that may fluctuate between 6 V and 8 V. Design a voltage regulator to supply a constant voltage of 5 V (= VZ) to a load that may vary from 8 kW to 12 kW. (Determine a fixed series resistance value with minimal over-all power losses in mind!)

• How to use Javalab
[Opdatering af log]