Voltage regulator tutorial pdf

There are two kinds of zener controlled transistor voltage regulators. Such a circuit is also named an emitter follower voltage regulator. It is called so because the transistor used is connected in an emitter follower configuration. The circuit consists of an N-P-N transistor and a zener diode. As shown in the figure below, the collector and emitter terminals of the transistor are in series with the load.

Thus this regulator has the name series in it. The transistor used is a series pass transistor. The output of the rectifier that is filtered is then given to the input terminals and regulated output voltage Vload is obtained across the load resistor Rload. The reference voltage is provided by the zener diode and the transistor acts as a variable resistor, whose resistance varies with the operating conditions of base current, Ibase. The main principle behind the working of such a regulator is that a large proportion of the change in supply or input voltage appears across the transistor and thus the utput voltage tends to remain constant.

The transistor base voltage Vbase and the zener diode voltage Vzener are equal and thus the value of Vbase remains almost constant. When the input supply voltage Vin increases the output voltage Vload also increases. This increase in Vload will cause a reduced voltage of the transistor base emitter voltage Vbe as the zener voltage Vzener is constant.

This reduction in Vbe causes a decrease in the level of conduction which will further increase the collector-emitter resistance of the transistor and thus causing an increase in the transistor collector-emitter voltage and all of this causes the output voltage Vout to reduce.

Thus, the output voltage remains constant. The operation is similar when the input supply voltage decreases. The next condition would be the effect of the output load change in regard to the output voltage. Let us consider a case where the current is increased by the decrease in load resistance Rload. This causes a decrease in the value of output voltage and thus causes the transistor base emitter voltage to increase. This causes the collector emitter resistance value to decrease due to an increase in the conduction level of the transistor.

This causes the input current to increase slightly and thus compensates for the decrease in the load resistance Rload. The load current Iload of the circuit will be the maximum emitter current that the transistor can pass. For a normal transistor like the 2N, the load current can go upto 15A. Such an emitter follower voltage regulator is more efficient than a normal zener regulator. A normal zener regulator that has only a resistor and a zener diode has to supply the base current of the transistor.

The limitations listed below has proved the use of this series voltage regulator only suitable for low output voltages. The image below shows the circuit diagram of a shunt voltage regulator. 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.

The zener diode is connected across the base and the collector of the transistor which is connected across the output. As there is a voltage drop in the series resistance Rseries the unregulated voltage is also decreased along with it. The amount of voltage drop depends on the current supplied t the load Rload. The value of the voltage across the load depends on the zener diode and the transistor base emitter voltage Vbe. The output remains nearly a constant as the values of Vzener and Vbe are nearly constant.

This condition is explained below. Thus, the supply voltage increases causing an increase in supply current, which inturn causes a voltage drop i the series resistance Rseries and thereby decreasing the output voltage. This decrease will be more than enough to compensate for the initial increase in output voltage.

Thus, the output remains nearly a constant. Mastering the Raspberry Pi. Output VA characteristics of a L However, components by other manufacturers behave differently. The pin 2 acts as the input terminal 5V to 24V. Questions must be on-topic, written with proper grammar usage, and understandable to a wide audience.

After their advice we have tested whether this problem can be caused by oscillating of the stabilizer. Heat sink boosts heat dissipation therefore the life of the device can be extended. Each type employs internal current limiting, thermal shut down and safe operating area protection, making it essentially indestructible.

The LM78S40 from Fairchild is not part of the 78xx regulato and does not use the same design. No data is shared with Paypal unless you engage with this feature. Voltage regulator IC can be defined as an integrated circuit that is capable of supplying a constant controlled output voltage which is not at all affected by the variations regulstor input voltage provided regjlator the variations are within the prescribed limits under specified atmospheric conditions. Diode D1 was added to compensate for the voltage drop across the base-emitter junction of Q1.

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This is probably the cause of the problem. This is used to identify particular browsers or devices when the access the regulatod, and is used for security reasons. Series Regulators use a power transistor connected in series between the unregulated DC input and the load. The output voltage is controlled by the continuous voltage drop taking place across the series pass transistor. Since the transistor conducts in the active or linear region, these regulators are also called linear regulators.

Linear Regulators may have fixed or variable output voltage and could be positive or negative. This gives improved efficiency over series regulator. The zener diode, a constant current and reference amplifier produce a fixed voltage of about 7 Volts at Terminal Vref. The constant current source forces the zener to operate at a fixed point so that, the zener outputs a fixed voltage. The circuit also consists of an error amplifier, a series pass transistor Q1 and a current limit transistor Q2.

The error amplifier compares a sample of the output voltage applied at the Inv input terminal to the reference voltage Vref, applied at the NI input terminal. The error signal controls the conduction of Q1. The output of the error amplifier drives the pass transistor Q1, so as to minimize the difference between the NI and INV inputs of error amplifier.

Since Q1 is operating as an emitter follower,. If the output voltage becomes low, the voltage at the INV terminal of error amplifier also goes down. This makes its output to become more positive, there by driving Q1 more into conduction.

This reduces the voltage across Q1 and drives more current into the load causing voltage across load to increase. So the initial drop in the load voltage has been compensated.

Similarly any increase in load voltage or changes in the input voltage get regulated. To protect the circuit we provide a current limit facility. Current limiting refers to the ability of a regulator to prevent the load current from increasing above a present value. The current limit is set by connecting an external resistor R4 between the emitters of Q1 and Q2.