We have discussed the application of zener diode as voltage regulator and now we will discuss the other two points. But when it is reverse biased above a certain voltage known as zener breakdown voltage or zener voltage or avalanche point or zener knee voltage the voltage remains constant for a. This breakdown voltage is known as the zener voltage. The complete vi characteristics of zener diode is as shown in figure. The output voltage can be greater or the polarity of output can be opposite that of the input by using this voltage regulator. Zener diode working, characteristics and application as. All electronic voltage regulators will have a stable voltage reference source which is provided by the reverse breakdown voltage operating diode called zener diode. The part requires a small quiescent current for regulation, and regulates the output voltage by shunting more or less current to ground, depending on input voltage and load. Zener diode as a voltage regulator working principles. Three different types are stepup voltage regulator, buck voltage regulator, and boostbuck voltage regulator. Working of the zener diode is similar to a pn junction diode in forward biased condition, but the uniqueness lies in the fact that it can also conduct when it is connected in reverse bias above its threshold breakdown voltage. Zener diodes are simple and useful devices for building voltage regulator circuits, but are times when you may have to improvise in the absence of the proper zener diode. When biased in the forward direction it behaves just like a normal signal diode, but when a reverse voltage.
This circuit enables a fixed stable voltage to be taken from an unstable voltage source such as the battery bank of a renewable energy system which will fluctuate depending on the state of charge of the bank. Zener diode is a pn junction diode specially designed to operate in the reverse biased mode. For a simple voltage regulation in the circuit or design zerner diode is the cost effective solution. Zener diode in may applications, operation in the reverse breakdown region is highly desirable. A voltage regulator is a circuit used to maintain a constant output voltage at a load independent of changes in the load current. Zener diode voltage regulator calculator below is a simple to use zener diode voltage regulator calculator. The figure below represents the circuit of zener diode as voltage regulator.
Lowpower voltage regulator diodes in small hermetically sealed glass sod80c surfacemounted device smd packages. Read on to understand how zener diodes and resistors are matched for any particular scenario. Zener regulator as mentioned earlier, the characteristics of the zener diode make it ideal for application as a voltage regulator. Zener diodes can be used to produce a stabilised voltage output with low ripple under varying load current conditions. The worst case situation occurs when vin is at the maximum value and the load current is at the minimum value as that results in the highest current through the zener diode. The series consists of 37 types with nominal working voltages from 2.
Zener diodes as voltage regulators a circuit diagram symbol for a zener diode. Zener diode and its functionality as voltage regulator. When the load current is the highest the zener conducts the least current while at lowest load current it conducts the most current. Zener diode has the property of behaving like a dc battery in on state i. Refer to the voltage reference circuit to set the resistance r 1. The breakdown voltage of zener diodes will be constant for a wide range of current. Zener diode as a voltage regulator working principles byjus. If we had oriented the diode in the normal way, so as to be forwardbiased, it would only drop 0. If source voltage vs can vary from 20 volt to 30 volt,find the maximum and minimum current in the diode. A transistor circuit such as the above may be incorporated into a type of integrated circuit p.
In a dc circuit, zener diode can be used as a voltage regulator or to provide voltage reference. Suppose we were building some kind of circuit which could not tolerate variations in power supply voltage. Oct 17, 2018 design for an opamp voltage regulator circuit to drive a load of 6v,1. Zener diode regulator with transistor current buffer. Zener diode voltage regulators 6 for step 3 we calculate the maximum power dissipation of the zener diode. The main use of zener diode lies in the fact that the voltage across a zener diode remains constant for a larger change in current. Zener diodes are used for voltage regulation, as reference elements, surge suppressors, and in switching applications and clipper circuits. If the resistors are good, then zener diode is bad.
Oct 15, 2017 it is recommended to read about how zener diode will provide the voltage regulation in the circuit before proceeding further zener diode based voltage regulator. When forward biased, it behaves like a normal signal diode, but when the reverse voltage is applied to it, the voltage remains constant for a wide range of currents. Jan 11, 2019 in this video, the examples based on the zener diode circuit have been solved. The zener voltage is the voltage at which the zener diode conducts current when reverse biased. Jan 02, 2019 the exciting part of this diode is that we can choose the zener diode with a suitable breakdown voltage to work as a voltage regulator in our circuit. The circuit consists of an npn transistor and a zener diode along with a series resistor rseries that is connected in series with the input supply. Overvoltage protection is done by using zener diodes because there is current flowing through the.
Zener diode as voltage regulator tutorial basic electronics tutorials. In normal diodes, the breakdown voltage is very high and the diode gets damaged totally if a voltage above the breakdown diode is applied, but in zener diodes, the breakdown voltage is not as high and does not lead to permanent damage of the zener diode if the voltage is applied as the reverse voltage applied to the zener diode increases towards the. When connected in parallel with a variable voltage source so that it is reverse biased, a zener diode conducts when the voltage reaches the diode s reverse breakdown voltage. We have already explained about ic voltage regulators. Zener diode as a voltage regulator zener diode is a silicon semiconductor with a pn junction that is specifically designed to work in the reverse biased condition. It is because multimeters usually do not have enough input voltage to put the zener into breakdown region. Voltage regulator circuits linear voltage regulator.
There are several drawbacks, however, that will be discussed shortly. Over voltage protection is done by using zener diodes because there is current flowing through the diode after the reverse bias voltage exceeds a certain voltage. Dec 14, 2012 zener diode is a general purpose diode, which behaves like a normal diode when forward biased. Voltage regulator circuits linear voltage regulator, zener. Voltage regulation is a useful diode property to exploit. Career point cares zener diodes are a special kind of diode which permits current to flow in the forward direction. The very simple zener diode circuit providing the shunt regulator function as shown above is not particularly efficient and is not practicable for many higher current applications. The examples are related to the zener diode voltage regulator circuits.
Zener diode is a silicon semiconductor with a pn junction that is specifically designed to work in the reverse biased condition. It is different from others diodes zener diodes will also allow current to flow in the reverse direction when the voltage is above a certain value. The negative feedback taken from the output is connected to the inverting pin of the opamp through a voltage divider. The main application of this type of diodes are as voltage regulator. But when it is reverse biased above a certain voltage known as zener breakdown voltage or zener voltage or avalanche point or zener knee voltage the voltage remains constant for a wide range of current. A zener diode is an electronic component which can be used to make a very simple voltage regulator circuit.
The reverse breakdown voltage is relatively insensitive to the current flowing thought the diode the reverse current. Zener diode shunt regulator shunt regulators are normally only used for applications where the load power is not much often only milliwatts and rarely more than a few hundred milliwatts because under the worst case situation of no load the zener has to dissipate the full load power. As shown in the figure above, the resistor is selected so that when the input voltage v in is minimum and the load current i l is maximum than the current through the zener diode is, at least, minimum i z. The stabilised output voltage is always selected to be the same as the breakdown voltage v z of the diode. This simple zener diode circuit is widely used as an easy method of providing a voltage reference. R s absorbs the voltage fluctuations so as to give a constant voltage at the output. In this region the voltage across zener diode remains constant but current changes depending on the supply voltage. When the load current is the highest the zener conducts the least current while at lowest load.
Voltage regulators,circuits,types,working principle. A zener diode is a diode that breaks down at a specific voltage when it is reverse biased. The zener diode working principles and its various applications. Figure 2 shows the current versus voltage curve for a zener diode. For example, we want that the voltage across a load in our circuit does not exceed, lets say, 12 volts.
Electronic voltage regulator all electronic voltage regulators will have a stable voltage reference source which is provided by the reverse breakdown voltage operating diode called zener diode. In a zener diode voltage regulator circuit,the source series resistance rs 20 ohm. Since the exploited property of zener diodes is the reverse breakdown voltage, connect the anode of the diode to ground, not the cathode. The voltage across load resistor r l is equal to the zener breakdown voltage v zkregardless of the value of load resistor r l or source voltage v s provided, of course, that the zener diode is in breakdown. Basic series regulator using a zener diode and emitter follower. The load voltage equals breakdown voltage vz of the diode. But when it is reverse biased above a certain voltage known as zener breakdown voltage or zener voltage or avalanche point or zener knee voltage the voltage remains constant for a wide range of current clarence zener is the scientist who discovered this electrical property and the device is named.
The fact that the voltage across the diode in the breakdown region is almost constant turns out to be an important application of the zener diode as a voltage regulator. Zener diodes when we first talked about practical diodes, it was mentioned that a parameter associated with the diode in the reverse bias region was the breakdown voltage, v br, also known as the peakinverse voltage piv. Exploiting this characteristic of zener diodes allows for simple, inexpensive voltage regulators. Lm431 adjustable precision zener shunt regulator datasheet. Zener controlled transistor shunt voltage regulator the image below shows the circuit diagram of a shunt voltage regulator. A zener diode is a pn junction that has been specially made to have a reverse voltage breakdown at a specific voltage. Zener diode is a special purpose pn junction diode, which operates under reverse biased condition. This is an example of a primary application of zener diodes voltage regulation. Basic electronics notes on vi characteristics of zener. The opamp voltage regulator circuit consists of a noninverting amplifier with a fixed reference voltage at the noninverting input. Zener diodes are normal pn junction diodes operating in a reverse biased condition. Zener diode is used as shunt voltage regulator for regulating voltage across small loads. The exciting part of this diode is that we can choose the zener diode with a suitable breakdown voltage to work as a voltage regulator in our circuit.
Please take note of the zener diodes orientation in the above circuit. The purpose of the zener diode is to stabilize the value of the output voltage. Observe the nearly constant voltage in the breakdown region. As we had already discussed in detail about the voltage regulation using zener diode, we will. For any given output voltage and current requirement it will calculate the value of power rating of the current limiting resistor and zener diode. Simple zener diode voltage regulator circuit designed to give 5 volt output from 9 volt input, you can replace the zener diode to get desired output voltage. Zener diodes are widely used as voltage references and as shunt regulators to regulate the voltage across small circuits. The zener diode is a type of diode which operates under the reverse bias that breakdowns when the applied voltage reaches a particular reverse bias voltage or knee voltage. Diodes and diode circuits tlt8016 basic analog circuits 20052006 11 3. When connected in parallel with a variable voltage source so that it is reverse biased, a zener diode conducts when the voltage reaches the diodes reverse breakdown voltage. Explain how normal diodes might be used as crude substitutes for a zener diode in the following circuit. Zener diodes cannot be tested individually with a multimeter. Mar 15, 2020 this quantity is set as the duty cycle of the switch.
Here, r s is the current limiting resistor, v s is the voltage source and r l represents the load resistance. It is acting as normal diode while forward biasing. Zener diodes are rated by their breakdown voltage v z and maximum power p z typically 400mw or 1. Until load voltage is less than the breakdown voltage, the zener diode. It allows the current to flow as like a normal pn junction diode when it is forward biased and block the reverse flow of current during the reverse bias up to the breakdown voltage. Pdf performance of shunt voltage regulators based on zener. Power is calculated by multiplying current by voltage pie, so we can calculate power dissipations for both the resistor and the zener diode quite easily. This was a bad thing before the whole avalanche breakdown, large current. Zener diode regulator procedure step 1 monitor and report the load voltage v l by using the scopy voltmeter instrument to measure v l for r l equal to. Applications of zener diodes zener diodes finds a wide applications commercially and industrially.
Jan 09, 2020 the only way to tell which device has failed is to remove the resistors and check them with an ohmmeter. In normal diodes, the breakdown voltage is very high and the diode gets damaged totally if a voltage above the breakdown diode is applied, but in zener diodes, the breakdown voltage is not as high and does not lead to permanent damage of the zener diode if the voltage is applied. A series of experiments were carried out to investigate the operation and performance of zener diode voltage regulators. The zener diode working principles and its various. The zener voltage regulator consists of a current limiting resistor r s connected in series with the input voltage v s with the zener diode connected in parallel with the load r l in this reverse biased condition. Zener diode working with circuit diagram and applications. Zener diode, resistors, power supply, multi meter circuit diagram. Zener diodes are used in circuits to maintain a fixed voltage across a load. The main reason to use a voltage regulator is to maintain a constant dc output voltage.
A zener diode is designed to operate in reverse bias, clamping the voltage across its terminals to the zener voltage. The zener diode is like a generalpurpose signal diode. As shown in the figure below, the collector and emitter terminals of the transistor are in series with the. Some of the important applications of a zener diodes are as a voltage regulator or stabilizer, as a meter protector and as a wave shaper. Building a voltage regulator with an ideal zener diode, construction of a voltage regulator is easy, simply connect the diode between the unregulated voltage and ground. The low value is required so as to allow the maximum flow of current through the diode, connected in parallel. Zener diode is connected parallel to the load to make it reverse bias and once the zener diode exceeds knee voltage, the voltage across the load will become constant. Applications of zener diodes voltage regulator, meter.
A simple circuit involving zener diode as a regulator requires a resistor of low value connected in series with the input voltage source. Here, we have designed a zener voltage regulator using 5. April 7, 20 introduction a zener diode is a pn junction that has been specially made to have a reverse voltage breakdown at a specific voltage. Building a voltage regulator with an ideal zener diode, construction of a voltage regulator is easy, simply connect the diode between. A simple zener diode voltage regulator in the voltage regulator the zener diode operates in the breakdown region, which ensures approximately constant voltage across it. For most of the low voltage diodes up to 15 v, the slope resistance is 20. This page describes the voltage regulator with the use of zener diode with its constructional details and working principle.
We will discussed what is the application of zener diode as voltage regulator, now we will discuss the other two points briefly. The only external component requirement is a resistor between the cathode and the input voltage to set the input current. Zener diodes are designed to operate in the reverse breakdown region. The zener diode is connected across the base and the. Its characteristics are otherwise very similar to common diodes. The series resistor limits the current through the diode and drops the excess voltage when the diode. When the supply voltage exceeds its breakdown voltage, its start conducting in reverse direction and maintains the same voltage across it and flow back the extra current, thus provide the stable output voltage. Zener diode circuit for psu with series transistor.
We can make a simple voltage regulator using zener diode as shown in the below figure. The circuit uses a single pass transistor in the form of an emitter follower configuration, and a single zener diode or other voltage regulator diode driven by a resistor from the unregulated supply. We call this particular regulator circuit the shunt. They are designed to provide voltage regulation protection and are especially attractive in situations where space is at a premium. The purpose of a voltage regulator is to maintain a constant voltage across a load regardless of variations in the applied input voltage and variations in the load current. Regulator zener diode regulator for low current power supplies a simple voltage regulator can be made with a resistor and a zener diode connected in reverse. Placing the zener diode in parallel with the load as shown in figure 3. In breakdown the voltage across the zener diode is close to constant over a wide range of currents thus making it useful as a shunt voltage regulator. In on state, the voltage across zener diode remains constant until the voltage across it deops less than vz. Zener diodes are supplied in a range of breakdown voltages, typically 2v7 to 62 v, and in a large variety of power ratings.
Diode circuits operating in the reverse breakdown region. The diodes are available in the normalized e24 2 % bzv55b and approximately 5 % bzv55c tolerance range. Zener diode is a general purpose diode, which behaves like a normal diode when forward biased. Such devices may also have current limiting features. A resistor that limits the current is connected across the load along with the zener diode. This electronics video tutorial provides a basic introduction into zener diodes which is used as voltage regulators in dc circuits. This can be done with a simple circuit using a resistor, zener diode, and transistor.
448 789 187 452 322 678 1466 695 911 1057 943 990 202 1429 1035 136 860 337 108 890 482 1108 1139 1521 1018 1411 973 737 739 1197 154 1669 1150 549 998 480 586 846 1033 542 1447 519 898 937