can LM 317T parallel combination be used to increase the current rating?

[GYU1751ASB]

hi,
I would like to know whether two LM 317 voltage regulator can be connected in parallel to increase the current rating or not. if anybody know the answer, plz reply me.
thanking you

 

[ashugtiwari]

well, theoretically may be its possible, i guess there are some circuits, but if there is difference in their regulated output voltage even by a slight, the problem can arise. For eg. one regulator gives 5.1V and another 5.2V, the regulator with 5.1V output will do most of work, overheat and shut the regulator off.
So, instead of directly connecting the two outputs, may be you can connect them through two different output resistor of high wattage and having different feedback circuitry for both of them.
But, ideally, i suggest using single regulator with current and voltage rating you need. U can build a small microcontroller based power supply, there are many application notes from microchip.

Hope that helps.

 

[chuckey]

Its much better for the LM to feed the base of a NPN transistor, its collector is fed from the input to the LM and the LM sense being fed from the emitter, which is the output connection. Some thing like :- https://www.elektroda.pl/rtvforum/topic2729254.html . How much current do you want? This is a bit complicated, use google images, I am sure some one has done this before.
Frank

 

[dimmich]

I launched three LM317T separate regulator for single radiator . With high accuracy (0.01 V) of the output voltages measured and made them identical using the fine tuning of the resistor. Then I shorted outputs regulators, and power on. Two of the three chips strongly warmed themselves!!! with load, and without load. After disconnecting the circuit outputs all three devices worked fine again.

Tried to add to all pins of regulators the ceramic capacitors. Tried to connect outputs through the power resistors 0.1 ohms. The situation has not changed.

I do not understand why it happened. I had to try to see on oscilloscope, may have occurred any parasitic generation, but now I do not have this scheme, I can not measure it.

For increase the power, some manufacturer recomend use the power transistor. But at high currents is much more advantageous to use pulse voltage regulators instead of linear regulators. Only in very sensitive circuits can not be used switching power supplies, but in most cases at high output currents switching power supply - the best solution in size, power dissipation of heat, the maximum current output.