Help me understand the relations in this zener diode

[woefulspawn]

Zener Diode Help

In the attached circuit the actual values doesn't really matter.

If the load resistor voltage increases then zener current does what?

If load resistor increases what could be wrong?

If load resistor voltage decreses then current through the first resistor does what? (meaning the series resistor)

If Voltage in increses current through the series resistor does what?

 

[E-design]

Re: Zener Diode Help

If the load resistor increases more current will be shunted through the zener to have a higher voltage drop over the series resistor. If the load resistor decreases, less current through zener and less voltage drop over series resistor. Increase/decrease in the input voltage will have the same effect. As long as the input voltage is higher than the zener voltage by a small margin (1v or so) you will have regulation.

That is why it is important to design so that the zener rating (watts) will be able to shunt all the extra current with high or no load resistor. Wz=Vz X Iz, so Imax=Wz/Vz. Try and design so that you never exceed about 70% of zener power rating with no load and max input voltage.

If you have actual data curves of the zener that you want to use, you should try and design your values to operate where the change in resistance against the change in current slope is the steepest

 

[sabari]

Zener Diode Help

R of the load increases more current will be by passed through the zener to have a higher voltage drop over the series resistor. If RL decreases, less current through zener and less voltage drop over series resistor. Increase/decrease in the input voltage will have the same effect.