6A / 0-28V Variable Power Supply

The following diagram is the schematic diagram of variable power supply which will deliver 0 to 28V output voltage at 6A or 8A electric current. 6A regulated variable power supply circuit

Components List 6A / 0-28V Variable Power Supply Circuit:

R1 = 2K2 Ohm 2,5 Watt
R2 = 240 Ohm
R3,R4 = 0.1 Ohm 10 Watt
R7 = 6K8 Ohm
R8 = 10K Ohm
R9 = 47 Ohm 0.5 Watt
R10 = 8K2 Ohm
C1, C7, C9 = 47nF
C2 = 4700uF/50v – 6800uF/50v
C3, C5 = 10uF/50v
C4, C6 = 100nF
C8 = 330uF/50v
C10 = 1uF/16v
C11 = 22nF D1…D4 = four MR750 (MR7510) diodes (MR750 = 6 Ampere diode) or 2 x 4 1N5401 (1N5408) diodes.
D5 = 1N4148, 1N4448, 1N4151
D6 = 1N4001
D10 = 1N5401
D11 = LED
D7, D8, D9 = 1N4001
TR = 2 x 15 volt (30volt total) 6+- Ampere
IC1 = LM317
T1, T2 = 2N3055
P1 = 5k
P2 = 47 Ohm or 220 Ohm 1 Watt
P3 = 10k trimmer
F1 = 1 Amp
F2 = 10 amp

Circuit Description:

This is an easy to make power supply that has reliable, clear and regulator 0 to 28 Volt 6/8 Amp output voltage. By making use of two 2N3055 transistor, you’ll get two times the amount of electric current.
Although the 7815 power regulator may kick in on short circuit, overload and thermal overheating, the fuses in the main section of the transformer and the fuse F2 at the output will safe your power supply. The rectified voltage of: 30 volt x SQR2 = 30 x 1.41 = 42.30 volt measured on C1. So all capacitors should be rated at 50 volts. Caution: 42 volt will be the voltage that could be on the output if 1 of the transistors ought to blow.
P1 lets you ‘regulate’ the output voltage to something in between 0 and 28 volts. The LM317 lowest voltage is 1.2 volt. To have a zero voltage on the output I’ve place 3 diodes D7,D8 and D9 around the output with the LM317 towards the base with the 2N3055 transistors. The LM317 optimum output voltage is 30 volts, but using the diodes D7,D8 & D9 the output voltage is approx 30v – (3x 0.6v) = 28.2volt.
Adjust your build-in voltmeter using P3 and, of course, a fine digital voltmeter is better solution.
P2 will let you to control the limit with the optimum available electric current in the output +Vcc. When utilizing a 100 Ohm / 1 watt varistor the current is limited to approx. 3 Amps @ 47 Ohm and +- 1 Amp @ 100 Ohms.
6A / 0-28V Variable Power Supply source:
http://users.belgacom.net/hamradio/homebrew.htm