Variable Power Supply Circuit Pdf Writer

Variable power supply circuit pdf writer

A power supply is a hardware component that supplies power to an electrical device.

Variable power supply circuit pdf writer

A power supply can be given from the battery or from a hardware circuitry which converts the AC supply into the DC supply or step-down AC to step-up AC and vice-versa. A variable power supply is one which facilitates the user to vary and adjust the desired output voltage and output current.

Usually, a potentiometer is used for voltage adjustments.

Working of Variable Power Supply with Digital Control

The variable power supply circuit is equipped with an adjustable voltage regulator to adjust the output according to the output. An adjustable voltage regulator has line regulation and load regulation. This block diagram shows how the AC voltage is regulated in the circuit. This circuit diagram is given below. The main supply of V is fed directly to the centre tapped transformer. This transformer step downs the V supply to 24V which is then rectified through a bridge rectifier.

The bridge rectifier gives a continuous pulsating DC signal. Then capacitors are used to filter the pulsating signal into a smooth non-pulsating DC.

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Finally, the voltage is regulated using a regulator IC. The voltage from the step-down transformer is then fed to the bridge rectifier which generates a continuous pulsating DC signal.

The polarity of the output cannot be inverted and has large ripples in it. This pulsating DC also has some unwanted current ripples which makes it impossible for using in powering applications.


A smoothing capacitor which acts as a filter is used to remove unwanted current Ripples. Now the output with capacitance will be as shown below figure and further filtered to get pure DC.

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The smooth, non-pulsating DC signal is fed to the voltage regulator. LM is used as a voltage regulator.

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The capacitors C2 and C4 are used to eliminate the ripples if the filtering process is done away from the regulator. Capacitor C4 also prevents the LM voltage regulator to act as an oscillator. Diodes are used to protect the regulator from excess flowing through if any voltage source is connected across the output terminals of the regulator.

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A variable resistance is connected across the ADJ pin of the regulator. The voltage regulator is an integrated circuit which supplies a constant, controlled output voltage irrespective of the change in input voltage.

Variable power supply circuit pdf writer

LM is a variable voltage regulator with 3 pins monolithic integrated circuit shown below. It is capable of providing 1.

Variable Power Supply Circuits

The ratio of two resistances connected to the LM voltage regulator can be used to set the desired voltage level. The LM voltage regulator has many electrical applications. Here are the few of the applications. The output of the transformer is rectified using a full wave rectifier to bypass the unwanted spikes and provide smooth, fluctuation free power.

Variable power supply circuit pdf writer

Capacitors are used to filter ripples. Both positive and negative half cycles are used to obtain positive and negative DC output.

Variable power supply circuit pdf writer

IC CD is a decade ring counter. Each of its outputs goes high one after the other when a clock pulse is received. Adjustable voltage regulator IC LM develops 1. Presets VR1 to VR9 is adjusted to get desired output voltage. As the presets VR1 to VR9 are connected at the collectors of transistors T2 to T10, different output resistances appear between the adjustable terminal and the ground terminal of IC4 which causes different output voltages. Thus the power supply unit can be used for circuits requiring both negative and positive voltages.

0-30 Vdc Stabilized Power Supply with Current Control 0.002-3 A

When CD is reset by pressing switch S3 the output voltage changes tom 1. LM is commonly used 3 terminal negative voltage regulator in electronic circuits. This IC provides constant negative output voltage despite changes in the input voltage. The number 79 indicates that the IC is a negative voltage regulator and 12 indicates the output voltage.

The universal power supply is most commonly used the circuit in electronic laboratories. It provides a varied and fluctuation free output.

How to Use LM317 for Making a Variable Power Supply Circuit

The above universal power supply circuit provides a variable voltage between 3 to 30V, the maximum current of 1. The adjustable voltage regulator LM U1 offers short circuit. The rectified input voltage from diode bridge filter capacitor charges up to V. This circuit is paired with a high power audio amplifier of W. The circuit is designed for laptop charger with 20V output and it uses TOP Y by power integration. A digital multimeter is a device used to measure the electrical values like voltage, current and resistance.

Digital multimeter has replaced analog meters due its high accuracy, reliability and increased impedance. This is all about Variable Power Supply circuit. We hope that you have gone a better understanding of the concept of this topic. Furthermore, any queries regarding this topic or electronics projects, please give your feedback by commenting in the comment section below.

Variable Power Supply Circuit

Here is a question for you, what are the applications of LM? For customization of projects please email us on team elprocus. Variable Power Supply Circuit The variable power supply circuit is equipped with an adjustable voltage regulator to adjust the output according to the output.

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Variable power supply circuit pdf writer

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