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Simple Variable power supply circuit 0-30v 2A

If you are beginners who want to use the simple variable power supply 0-30V 2A. This circuit is best for you. Because it has a few parts, small, and cheapest than others circuit that same power. The features of this handset are the DC voltage continuously from 0-30 volts and apply current up to 2 amperes and can put easily in a large pro box.

How it works
Figure 1 is a circuit diagram. We apply AC line to the circuit to SW1 on/off to the transformer T1 and fuse F1 to protection circuit when too much power source.


Beginning Variable power supply circuit 0-30v 2A
Figure 1 Beginning Variable power supply circuit 0-30v 2A

T1 reduce AC voltage 220V into 24V 0 24V. Then, the current through to both diode D1, D2 to rectifiers to DC voltage. Next, C1 filter current to DC voltage about 36V.

There are LED1 to show power on and R1 limit current to a safe value.

R2-100ohms and ZD1-30V are connected together as the 30V steady DC regulators.
The variable resistors VR1 is used to adjust the output voltage between 0V to 30V, that have transistors Q1, Q2 increase the output current up to 2A. Also, there is the short-Circuit protection include Q3, R3.

How to builds
The circuit assembly is very simple Because the devices are less Can assemble down on the perforated board. While the power transistor Q3 – 2N3055 is working, will hot so we always use a heat sink on it.

Should use low wattage soldering iron does not exceed 30 watts. The soldering the legs of transistors and diodes we should use the pliers with leg devices Because these devices cannot be very hot.

Adjustment and usage
The prototype works well, have ripple voltage at output lower than 1 mV and the output voltage will drop lower than 0.1 volts

In real usage that although it off, LED power ON will still light up for a moment. Because the LED get current from C1 that does not discharge fully.

‘Keep reading: 0-30V, 3A Adjustable DC Supply’ »

If you want to stop LED immediately, may move R1 and LED1 to across the secondary of T1. Then, add the diode-1N4001 series with LED to protects voltage backward which LED may be damaged as Figure 2

The LED will outage immediately when switched off
Figure 2: The LED will outage immediately when switched off


If need to use the dual power supply (Positive Ground and Negative terminal) For testing amplifier OCL.

We change the rectifier section to new, from a Full wave into the bridge and use the two secondary coil; 24V 2A. Then, apply the negative and positive of each channel to the ground as Figure 3

Making supply is 2 sets with bridge diode and capacitor
Figure 3: Making supply is 2 sets with bridge diode and capacitor


The parts you need
Q2,Q3____2N3055 Power NPN transistor
Q1_______BC548,BC549___45V 100mA NPN Transistor
D1,D2_____1N5402 3A 100V Diode
D3_______1N4002 1A 100V Diode
ZD1______30V 1W Zener
VR1_______10K Potentiometer
R1________3.3K_____0.25W resistor
R2________100 ohms____0.5W resistor
R3________0.3 ohms 10W resistor.

Be careful Components pinouts

Some parts on this have different pins. You need to put it in the correct way only!

Be careful component pinouts on power supply circuit
Be careful component pinouts on power supply circuit

Best Variable DC power supply projects

0-50V 3A variable power supply

This Post Has 18 Comments

  1. Thanks.

  2. Hi, Salim Khan
    Thanks for your feedback.
    You are welcome.

  3. Very interesting !

  4. simply—–the best!

  5. Hi, Augusto Principato
    Thanks for your feedback.

  6. where is the placement of VR1 10k pot. I can not see it in figure

  7. Hi, subodh
    Thanks for your feedback.
    Please look at the figure 1.
    VR1-10K ,

  8. hi is this still uselful with 12 0 12 volts transformer?? can u make using 12 0 12 volt transformer.?

  9. hi, how can i change the output to 3 Amp in this schematic diagram?

  10. This circuit is great. It works. Thanks!

  11. Hey! Plz explain me! How the current is amplified … Coz , its confusing me! Make it fast, or reply to my mail id. [email protected]

  12. Hiii
    I would like to send me some mini circuits

    1. Hello, Mamdouh
      If you still want mini circuits. I will send you the email. Thanks

  13. a current limit function would be very nice..anyone can tell me how to add a current limiter function to this circuit?

  14. Hello, Jed Frances Ararao
    Thanks to your question. This is a simple circuit. It has basically a current limiting function. When the current is too much. There is a voltage across R3. Then, Q3 get a biased current. It works, the collector and emitter is low voltage. Thus, Q1 and Q2 stop. No current to load.

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