High Current LM317 Variable Power Supply Circuit

You you are looking for a high current LM317 variable power supply circuit version then you have probably landed on the right post. Here you will find how an ordinary LM317 circuit could be converted into a high current 20 amp variable power supply circuit using just a few 2n3055 power transistors in conjunction with a standard LM317 voltage regulator circuit stage.

high current LM317 variable power supply circuit


Looking at the proposed high current LM317 regulator circuit design we can see how the basic LM317 variable power supply design which is normally rated to deliver just  1 amp current is cleverly upgraded to a high current version using a few 2N 3055 transistors.

All the 2N3055 transistor are configured in their individual emitter follower mode, which implies that all these will follow and produce voltage output at their emitters that may be exactly equal to the LM317 output, meaning when the LM317 pot is adjusted for a particular output voltage, the emitters of the power transistors would exactly replicate and produce the same amount of voltage at their emitters, but since he collectors of these devices are connected with the high current supply rail would transform the LM317 voltage into a high current capacity that may be equal to the maximum current carrying capability of the transistors as well as the power supply specification.

Thus this simple tweak using a few 2N3055 transistor transforms a ordinary LM317 variable regulated power supply into an awesome high current LM317 regulated variable power supply unit.

However make sure that all the 2N3055 are mounted over a large common heatsink, using a generous amount of heatsink compound paste but without mica isolators.

The 0.47 ohm resistors limit the current to the devices maximum current specs, if some other transistor such TIP35C are used this may be changed to obtain current as high as 100 amps