Powerful DC variable supply with LM317 and 2n3055

Commonly we use fix voltage regulator when we have to fix voltage for any circuit. Many times we need variable voltage power supply to control the voltages according to our choice and here we needed a variable voltage power supply. LM 317 is is best choice for this purpose, Draw back of lm 317 is that it can control and can be uses in very low amperes, In this article i will clear how can some one make a power full DC variable power supply with the use of LM317 with the addition one more transistor.

LM 317 Regulator

It is a type of positive-linear-voltage regulators used for voltage regulation ,designed by Robert C in 1976 while he worked at National Semiconductor.

It is a three-terminal-adjustable-voltage regulator and is easy to use Because it has only three terminal to use. It is majorly used for local and on card regulation. If we use fix resistors with this regulator then it can also be used as fix output like 7805,7806,78XX and so on,

Variable Voltage Power Supply LM317

The LM317 is a fully adjustable positive voltage regulator that can control 1.5 amps with an output voltage from 1.25 volts to 30 volts. By using the ratio of two resistances one of a fixed value and the other variable or both fixed,.we can set the output voltage to our desired level. Total input can be given to this regulator from 3 to 30 volts DC.

Powerful DC variable power supply using 2n3055 transistor

The above given circuit can control on 1.5 amps DC current but some times we have to control more amps to control our DC appliances. To control powerful appliances we must have to use powerful power supply so now we convert our supply in powerful supply with the help of another transistor 2n3055, It can control 15 amps DC current ranging 60 volts.

An alternative circuit is shown above for an adjustable power supply with LM317 and parallel connected NPN power transistors. It can control 15 Amps according to my knowledge and if some one needed more amps then another circuit design also given below.

This circuit share double amp and that is way you can control more amp with this circuit any how if u find any mistake in this circuit then please share your knowledge with me i will be great full to you.

I made the first one circuit with one transistor (2n3055) that works very perfectly but when i used it with two transistors it did not work. what is problem i did not understand if any expert read my post plz must guide me and my viewers with explanation ,


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  1. hola amigos quiero hacer un controlador de velocidad para una bicicleta o monopatín que trabaje con 12v o batería de auto si tienes alguna idea o diagrama se los agradeceria

    1. si tengo una idea clara
      Puedes hacerlo con el diagrama dado.

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