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2.5-30V Variable Power Supply Circuit

The variable power supply circuit presented in this schematic allow to supply a consumer with a 60-70 W power consumption and a range of voltage between 2.5-30V with a current from 0.6A to 2.5 A .This variable power supply has a shortcircuit protection and a scale indication for output voltages and current.
The capacitor filter for input voltage must have a value between 3300-6800uF.
Error amplifier of the source it's made with a 741 operational amplifier which is supply with a 40 V tension from D7 , D8 diode.
The reference voltage it's given from an other 741 amplifier which give a very stable reference voltage.
Ic U1 commands a darlington connection made by T5 and T3 which command the power transistors 2n3055.
The limit current is given by T6 trough Pot2 which allow to chance the limit current.
When the current it's over the limit the lamp is lighting.

The 2N3055 transistors must be mounted on a heatsink with a 400cm 2 area.
The transformer must give 30 volts and 3 Ampers.
2.5-30V Variable Power Supply circuit diagram Components

Notations Value
R1,R6
R2
R3
R5
R7,R9,R11
R8
R10
R12,R13
R14
R15
R17
C1
C2
C3,C4,C5
D1,D2,D3,D5,D6
D4
D7,D8
D9
U1,U2
Pot1
Pot2
Q2,Q4
Q1,Q3
Q5,Q6
S1
bec
mA
0.33 ohm Rezistor/5W
1 ohm Rezistor /10W
330 ohm Rezistor /10W
300 ohm Rezistor /3W
Se aleg a.i la cap de scala sa arate val maxima
2.7k ohm Rezistor
12k ohm Rezistor
5.6k ohm Rezistor
22k ohm Rezistor
6.8k ohm Rezistor
4.7k ohm Rezistor
220µF/40V
3300µF/40V
10nF
1n4001(1n4004)
Bridge
Dioda zener 20V
Dioda zener 5.1V
Ad741
100k lin
500 ohm lin
2n3055
Bd135(Bd139)
Bc107
switch
lamp 24V 0.05A
miliampermetru

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