How does lm317 work

It can supply the output voltage in a range of 1. It has advanced line regulation and load regulation standards as compared to the general regulators. It has a lot of applications in rela life e. LM works on a very simple principle. It is a variable voltage regulator i. A variable resistor is connected at its Adjustment Adj terminal in order to control the level of the output voltage according to the requirements of the circuit.

We need to do one more thing: calculate the power dissipated in the LM This will be the voltage across the LM times the current:. Skip to content. LM constant-current power supply. Voltage drop and headroom For the LM to regulate properly it must have adequate supply voltage to allow for the sum of the voltage drops in the circuit.

How does this power supply circuit work? Asked 10 years, 3 months ago. Active 5 years, 3 months ago. Viewed 8k times. Any insight would be appreciated. PetPaulsen 2, 3 3 gold badges 21 21 silver badges 33 33 bronze badges. Saad Saad 5, 8 8 gold badges 57 57 silver badges 88 88 bronze badges. Add a comment. Active Oldest Votes. All the rest is "engineering" or not :- The opamp is effectively forming a dynamic value of the "datasheet's R2" in series with R4 on the circuit.

Could be useful for controlling a fan. Depending on their values in relation to R1, they might also determine a default voltage about which the micro has only limited influence.

Show 3 more comments. In operation, the IC lm develops and maintains a nominal 1. This reference voltage is converted to a programming current I PROG by resistor R 1 , and this constant current flows through potentiometer R 2 to the ground. By changing R 2 , a wide range of output voltage can be obtained, and a suitable heatsink should be placed to dissipate excess heat from the IC. The output voltage V out is dependent on values R 1 and R 2 , according to the following formula:.