Proper heat sink must be provided for the power transistors.Correspondingly the emitter voltage of power transistor 2N3055 is varied. By varying the resistance of potentiometer output voltage of LM317 IC can be varied.Collector of 2N3055 connected to Vcc and Emitter of each transistor are looped together to get output terminal.In this circuit the output from LM317 directed to parallel combination of 2N3055 power transistors which will increase the output current hence the power also.2N3055 power transistor can handle a maximum of 115 watts and the maximum collector current is 15A.Here the first section of circuit is same as before but in order to boost current we are using 2N3055 transistor.We have already discussed LM 317 Variable DC Power supply, but it was low current. Output of LM317 variable voltage regulator in connected to the base of 2N3055 power transistor.
![2n3055 transistor resistance check 2n3055 transistor resistance check](https://www.eleccircuit.com/wp-content/uploads/2019/11/Power-transistor-works-as-resistor.png)
Output voltage of this IC can be varied between 1.25V and 37V.! Yes, this is the best choice of variable power supply circuits. As you know LM317 is a variable voltage regulator IC.High Current Variable Power Supply Circuit Diagram Battery charger circuit with auto cutoff.The maximum input to this DC variable power supply is 37 volts. This can be used as a regulated 48V DC power supply or 24 V DC power supply. 2N3055 can handle 15A, so by connecting parallel make add the individual current. So I connected a power transistor which helps to increase the current without varying the voltage. My 30Ah lead acid inverter battery takes more time for constant voltage charging when I use a LM317 variable voltage regulator. I happened to design variable power supply schematic diagram for my inverter battery for safe and quick charging. So to get through such problems I introduce a high current variable voltage power supply circuit which can drive 10A of load, the current handling capacity can be increased simply by connecting 2N3055 power transistors in parallel.
![2n3055 transistor resistance check 2n3055 transistor resistance check](https://ww2.justanswer.com/uploads/molurch/2010-11-07_142033_altim.png)
Variable power supplies are available in different ranges but they provide very low current of one or two amperes, they can’t drive high power devices like motor or high power lamps.