zener diode voltage regulator?

Question

I have this problem involving a zenor diode voltage regulator circuit. The zener is a 1N4753. R=56 ohm. Vin = 12 v. The load varies from 0 to 150mA. How would i calculate the load setting( RL) when the zener comes out of breakdown?

here is the drawing of the circuit:
http://img.photobucket.com/albums/v233/jster28/1-1.jpg

p.s.
I'm not looking for the answer, but some guidence on how to solve this problem. This is my first electronics class, so i'm kinda confused on how to solve this problem.

Answer 1

take a look at the datasheet for the 1N4735 at one of these suppliers
http://www.datasheetcatalog.com/datasheets_pdf/1/N/4/7/1N4753.shtml

from there you can get the zener voltage - this model appears to be a 6.2V device (i assume you mean the ..35 not ..53)
The 2 resistors act as a voltage divider - so the applied voltage across the zener is related to the ratio of the 2 resistances.

so you need to calculate the resistance Rl that would create 6.2V across the zener. this is the point where it conducts. If Rl is lower than this value, it will pull more current and the voltage drop across R will be more than 12-6.2V - so the zener cannot regulate. if Rl is higher than this value, more than 6.2V is applied to the zener and it conducts, regulating the voltage to 6.2V.

lookup the links below to understand how to calculate the voltage divider and good stuff on Thevenin and Norton equivalent circuits which will help with more complex examples

Answer 2

Think this way. As you increase the load current, the voltage drop across R increases. This leaves less voltage across the load and the zener. The zener will leave breakdown when there is only Vz or 6.2 V left. So you have to figure three things: How much of a voltage drop across R will leave you 6.2V across the load. The current through R to give you that drop. And, if all that current goes through RL (remember the zener shut down so it's not conducting) the resistance of RL needed to drop 6.2 V.
I hope that makes it clear. Email me, I'd be happy to answer any other questions. Charley

Answer 3

[1] Resistor value calculate at the peak solar cell voltage 39V. [2] 24V zener diode cut off at voltage below 24V. Therefore, output is 20V while solar cell produces 20V. [3] No more high power more than 3W zener diode was manufactured now. You need to use power transistor and let zener voltage control its base. Choose power FET to obtain more than 4.8A current flow capacity.

Answer 4

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