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Build Your Own 3-30V Adjustable DC Power Supply
Description
This power supply unit is intended as a supplementary or a permanent power source for a variety of circuits, providing a stable direct current voltage ranging from 3 to 30V, provided the current draw does not exceed 3A. Naturally, this power supply unit can also be utilized for alternative applications. By replacing the trimmer capacitor with a potentiometer, it can even function as a variable power supply. A high-quality heatsink is essential for proper operation.
Picture of project:
Circuit diagram:
Parts list:
- R1 = 8.2K
- R2 = 2.2K
- R3 = 680R
- R4 = 1K
- R5 = 82K
- R6 = 0.18R/5W
- C1 = 470p
- C2 = 100nF-63V
- C3 = 100nF-63V
- C4 = 100uF-63V
- C5 = 10KuF-60V
- D1-D6 = 6.6A
- Q1 = MJ3001 (Darligton)
- IC1 = UA723D
Specifications:
- Overload secure
- Short-circuit resilient
- Output current: maximum 3A
- Output ripple voltage: 0.5mV
- Output voltage: adjustable from 3 to 30V, stabilized
- Input voltage: 9 to 30V AC (depending on the desired output voltage)
Assembling into a housing:
- Depending on the transformer employed, one may select one of two enclosures
- If a metal enclosure is utilized, it must be earthed for safety reasons.
- Ensure the cooling body does not contact the enclosure. This could lead to a short circuit.
- When mounting a toroidal transformer, verification is needed that the fixing bolt does not touch the cover. This may cause the transformer to burn.
- If the circuit is to be integrated into another enclosure, it must be furnished with ventilation holes (one can fabricate these holes oneself), necessary for the release of the heat produced.
Notes :
- Connect a voltmeter to the points ‘GND’ and ‘+OUT’ and adjust ‘RV1’ until the desired output voltage is attained.
- Apply some thermally conductive paste to the underside of the transistor and mount it onto the heatsink.
- If you require a voltage between 3 and 8 volts, then R2 will be 5.6K
- If you require more than 8 volts, then R2 will be 2.2K
- Suitable transformer 30vAC at 120VA