This is how Zener breakdown occurs; given enough energy by the electric potential difference across the Zener diode, the chances of an electron tunneling through the barrier increases dramatically. The Zener diode has a maximum power rating that designates the maximum amount of electric power that it can safely dissipate.
Since a Zener diode has a relatively fixed Zener voltage V Z , the power rating essentially dictates the maximum current that the diode can handle:. There are two components, and therefore, two primary choices that must be made when designing a Zener regulator. These are the Zener diode and the resistor. The first design choice to make is the Zener diode. Diodes come in a large selection of Zener voltages. The selection process starts by choosing a diode with a Zener voltage V Z that matches the output voltage that you want the regulator to provide.
The power rating and Zener voltage V Z can be used to determine the maximum current:. The two parameters that were found can be used to determine the value of resistor needed to complete the circuit. Now that we know the minimum and maximum values of resistor that we need in order to safely use the chosen Zener diode, we can use the load resistance to find the ideal resistor. In this case, the current through the resistor I R must be equal to the current through the Zener diode plus the current through the load:.
We calculate the maximum and minimum load currents using both the minimum and maximum values for resistor R 1 note that the voltage across the load is equal to V Z :. Zener regulators are commonly used in power supplies following the rectifier filter and bleed resistor.
A bleed resistor dissipates any stored charge from the filter capacitors if the circuit is disconnected from the power source. Finally, the Zener regulator outputs a constant voltage, absorbing fluctuations in voltage and current. Search Advanced search…. New posts.
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Register Log in. JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser. What's the difference between the voltage regulators and zener diodes?
Thread starter seadolphine Start date May 7, Status Not open for further replies. I have a small question that might be a silly one; What's the difference between the voltage regulators and zener diodes.??? I mean the difference in the function. I need to get it down to a maximum of 5. My space is limited on a board, and since the logic gates require very little current, I'm thinking a 5.
Someone did mention they are useless vs a voltage regulator if you need any amount of current draw. Quote from: Falcon69 on April 18, , am. Laura Contributor Posts: 18 Country:. How the hell did Dave know that Bob is my uncle?
Here is a real world example. This is from a project done several years ago. It is just one of many variations I tried before deciding that an LM was a much better choice. This circuit was to power a which in turn had to supply only about 15 mA. As you can see, over a fairly wide range of input voltages the 10 volt zener only regulates between about 10 to 11 volts. If your input voltage and output current is fairly constant a zener can work, otherwise a real voltage regulator will probably be better.
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