Adjustable LM317 IC Voltage Regulator Circuit With Working

The power supply received at the load end or consumer end has fluctuations in the voltage levels due to irregular loads or based condition of the local power grid. These voltage fluctuations may lead to the reduction of lifespan of the electrical and electronic appliances of the consumer or damage to the loads.  So, it is required to protect loads from over and under voltages or need to provide a constant voltage to the loads and to maintain stability in system voltage using regulation technique. Voltage regulation can be defined as maintaining constant voltage or maintaining the voltage level of a system within acceptable limits over a wide range of load conditions and thus, voltage regulators are used for voltage regulation. For linear voltage regulation, occasionally adjustable IC LM317 voltage regulators are used wherein non-standard voltage is intended.
The voltage regulation in a power supply  can be achieved using an electrical or electronic device. There are different types of voltage regulators such as Fixed voltage regulators like 7805,7806 ect and Variable voltage regulators such as LM317. These are again subdivided into many types as Electronic voltage regulators, Electro-mechanical regulators, Automatic voltage regulators, Linear voltage regulators, Switching regulators, LM317 voltage regulators.

LM317 Voltage Regulator

It is a type of positive-linear-voltage regulators used for voltage regulation,  which is invented by Robert C. Dobki.n and Robert J. Widlar while they worked at National Semiconductor in 1970. It is a three-terminal-adjustable-voltage regulator and is easy to use because to set the output voltage it requires only two external resistors in LM317 voltage regulator circuit. It is majorly used for local and on card regulation. If we connect a fixed resistor between the output and adjustment of LM 317 regulator, then the LM317 circuit can Decoupling capacitors are used for decoupling or to prevent undesired coupling of one part of an electrical circuit from another part.
To avoid the effect of noise caused by some circuit elements over the remaining elements of the circuit, the decoupling capacitors in the circuit are used for addressing the input noise and output transients. A heat sink is used with the circuit to avoid the components getting overheated due to more power used as a precise current regulator.

Features of LM317 Voltage Regulator

There are some special features of LM317 regulator and a few are as follows:

  • It is capable of providing excess current of 1.5A, hence it is conceptually considered as operational amplifier with an output voltage ranging from 1.2V to 37V.
  • The LM317 voltage regulator circuit internally consists of thermal overload protection and short circuit current limiting constant with temperature.
  • It is available in two packages as 3-Lead Transistor Package and surface mount D2PAK-3.
  • Stocking of many fixed voltages can be eliminated.

Working of Voltage Regulator LM317 Circuit

The LM317 regulator can provide excess output current and hence with this capacity, it is conceptually considered as an operational amplifier. The adjustment pin is the inverting input of the amplifier and to produce a stable reference voltage of 1.25V, an internal bandgap reference voltage is used to set the non-inverting input.
The output pin voltage can be continuously adjusted to a fixed amount using a resistive-voltage divider between the output and ground, which will configure the operational amplifier as a non-inverting amplifier.
A bandgap reference voltage is used to produce constant output voltage irrespective of the changes in supply power. It is also called as temperature independent reference voltage frequently used in integrated circuits.
The output voltage (ideally) of the LM317 voltage regulator circuit

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