Tag Archives: LM317

1.2V-32V @3A Variable Switching Regulator using LM317

The circuit presented here is based on LM317. Generally, LM317 is known as a linear regulator IC, but here the circuit operates as a switching regulator. This circuit operates by transferring energy
from the input to the output by using a solid state switch. Power Efficiency of a switching regulator is much higher than the linear regulators. The input voltage for this circuit is 8V-35V and it can produce the output of 1.8V to 32V, that can be varied by using potentiometer R3.


  • Input(V): 8VDC to 35VDC
  • Output(V): 1.8VDC to 32VDC
  • Output load: 3A
  • PCB:68mm X 50mm

1.2V-32V @3A Variable Switching Regulator using LM317 – [Link]

Dual Adjustable Regulated power supply 1.2V TO 37V DC


This project is a solution to power up most of devices or projects requiring dual (+/-) adjustable power supply. The circuit is based on LM317 positive and LM337 negative voltage regulators. LM3X7 series of adjustable 3 terminal regulators is capable of supplying in excess of 1.5A over a 1.2V to 37V DC output range. On board TO220 Package with heat sink can handle maximum load current. Board provided with two on board preset to adjust the voltage.

Dual Adjustable Regulated power supply 1.2V TO 37V DC – [Link]

LM317 smooths but doesn’t regulate


Michael Dunn discuss about a circuit that smooths ripple and noise but doesn’t regulates the output.

A well known power supply circuit is the capacitance multiplier. It doesn’t regulate, but instead reduces ripple & noise while the output tracks at some fraction of the input vol

LM317 smooths but doesn’t regulate – [Link]

1.2V to 37V Regulated Power Supply – 1.2A


This project provides a variable output power supply ranging from 1.2 to 37 V @ 1.5 A. Uses industry populer LM317 in TO3 package for delivering variable output voltage.


  • Input 40 VDC or 28V AC 2Amps
  • Output : 1.2 to 37 V @ 1.5 A regulated low ripple DC voltage
  • Heatsink for regulator IC
  • Onboard bridge rectifier to convert AC to DC
  • LED indication at input of IC
  • Thermal overload/short circuit protection (provided by IC feature)

1.2V to 37V Regulated Power Supply – 1.2A – [Link]

Circuit adds foldback-current protection

Use-an-LM317-as-0-to-3V-adjustable-regulator-fig-1 by Rafael Garcia-Gil @ edn.com:

For many applications that require power-supply currents of a few amperes or less, three-terminal adjustable-output linear voltage regulators, such as National Semiconductor’s LM317, offer ease of use, low cost, and full on-chip overload protection. The addition of a few components can provide a three-terminal regulator with high-speed short-circuit current limiting for improved reliability. The current limiter protects the regulator from damage by holding the maximum output current at a constant level, IMAX, that doesn’t damage the regulator (Reference 1).

Circuit adds foldback-current protection – [Link]

Use an LM317 as 0 to 3V adjustable regulator


by Vladimir Rentyuk @ edn.com:

Most engineers know that they can use an inexpensive, three-terminal adjustable regulator, such as Fairchild Semiconductor’s LM317, as an adjustable regulator to only some necessary value of voltage, such as 36 or 3V. This value cannot be less than 1.25V without employing other approaches, however. The devices’ inner reference voltage is 1.25V, and their output voltage accordingly cannot be less than this value without potential bias (Reference 1). One way to solve this problem is to use a reference-voltage source based on two diodes (Reference 2).

Use an LM317 as 0 to 3V adjustable regulator – [Link]