2n3055 adjustable power supply circuit diagram

2n3055 adjustable power supply circuit diagram (I)

This simple variable power supply circuit is low cost to produce and has an output voltage between 1.5V and 15V with a maximum current of 500mA. Its stability is better than 350mA if the current consumption does not exceed 2mA. The variation of the supply voltage can be made by a potentiometer and a buzzer will sound an alarm when an overload occurs.

T4 matches the P1 slider voltage to the output voltage. Then the P1 slider voltage is 0,65V higher than the adjusted voltage, T2 opens, stopping the T3-T5 Darlington base current. The 18V, 1A transformer voltage must be filtered with B1 and C1. When the output current exceeds 500mA, Bz1 activates the alarm (overload). Bz1 must be a 24V type, automatic oscillation.

2n3055 adjustable power supply circuit diagram (II)

After rectification and filtering, the DC voltage is supplied to the base of the adjustment tube by R1, which turns on the adjustment tube. When V1 turns on, the voltage passes through RP and R2 to turn on V2, and then V3 turns on. At this time, the emitter and collector voltages of V1, V2, and V3 no longer change (their function is the same as that of the voltage regulator tube). By adjusting RP, a stable output voltage can be obtained. The ratio of R1, RP, R2 and R3 determines the output voltage value of this circuit.

Transformer T is 80W~100W, input AC 220V, output double winding AC28V. FU1 is 1A, FU2 is 3A~5A. VD1 and VD2 are 6A02.

RP uses a 1W common potentiometer with a resistance of 250K~330K, C1 uses a 3300µF/35V electrolytic capacitor , C2 and C3 use 0.1µF monolithic capacitors , and C4 uses a 470µF/35V electrolytic capacitor.

R1 is 180~220Ω/0.1W~1W, R2, R4, R5 are 10KΩ, 1/8W. V1 is 2N3055, V2 is 3DG180 or 2SC3953, V3 is 3CG12 or 3CG80.