In this article IC LM723 chip controls the voltage.
It give stable DC output, voltage and current adjustable.
Output voltage range is 2V to 37V and up to 150mA and input is max 40V.
High Current Adjustable Regulator Circuit with 30V 3A Output is good for lab supply and projects.
With extra pass transistor it can handle more current.
Circuit Working:
Parts List:
| Component | Value | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 watt unless specified) | ||
| 680Ω | 1 | |
| 82k | 1 | |
| 1k | 1 | |
| 0.18Ω 5W | 1 | |
| 8.2k | 1 | |
| 2.2k | 1 | |
| Potentiometer 10k | 1 | |
| Capacitors | ||
| Electrolytic 10000µF 50V | 1 | |
| Electrolytic 100µF 25V | 1 | |
| Ceramic 100nF | 2 | |
| Ceramic 470pF | 1 | |
| Semiconductors | ||
| IC LM723 | 1 | |
| Transistor MJ3001 | 1 | |
| Diode 6A6 | 2 | |
| Bridge Rectifier Diodes 6A6 6 amp | 4 | |
| Transformer 230V Primary and 25V Secondary 5A | 1 |
Circuit take 230V AC, step down, change to DC and filter for smooth output.
IC LM723 keep voltage steady and MJ3001 handle big current.
R4 is power resistor 0.18Ω watch current and give overload protection.
R5 and R6 set output voltage.
How circuit parts works :
Transformer lowers AC voltage.
D1 bridge rectifier make pulsating DC.
C1 10000µF smooth DC.
IC LM723 get voltage at pin 12.
VR1 + R1 at pin 5 adjust output and VR1 change voltage.
IC LM723 compare reference and feedback and adjust output.
Q1 MJ3001 boost current capacity.
R4 check current and stop overload.
D2 and D3 6A6 protect from spikes and reverse polarity.
C4 and C5 keep output steady.
Formulas with Calculations:
Vout formula: Vout = Vref × (1 + VR1 / R1)
Vref = 7.15V. VR1 = 10kΩ, R1 = 680Ω.
10000 / 680 = 14.7059
1 + 14.7059 = 15.7059
7.15 × 15.7059 = 112.30V.
So with VR1 is 10k you can get 112.3V and not 30V.
If we want 30V output then VR1 must be about:
VR1 = 680 × (30/7.15 − 1) = 2.17 kΩ.
Current limit formula: Ilimit = 0.6V / R4
R4 = 0.18Ω.
0.6 / 0.18 = 3.33 A.
Thus the circuit limits maximum current to 3.33 A.
How to Build:
To build a High Current Adjustable Regulator Circuit with 30V 3A Output follow the below mentioned steps:
- Collect all parts as per circuit diagram.
- Pin 2 of LM723 connected to emitter of Q1 through R3.
- Output 2 to 37V from LM723 connected to Vout.
- Pin 4 connected to pin 13 through C3.
- Pin 5 connected to center leg of VR1 and lower leg of VR1 is connected to R1 and upper leg of VR1 is connected to pin 6.
- Pin 10 is connected to base of Q1 and collector of Q1 is connected to positive output terminal.
- Pins 11 and 12 are connected to positive supply.
- R4, R5, R6 connected in series from emitter of Q1 to ground.
- Cathode of D2 connected to positive terminal; anode connected to junction of emitter of Q1 and R4.
- R2 connected from positive supply to pin 2.
- C4, C5 and D3 connected from pin 2 to ground.
- C1 and C2 connected in parallel from one end of bridge rectifier D1 to ground.
- Secondary winding of transformer connected to two AC inputs of bridge rectifier D1.
- One DC output of bridge rectifier D1 connected to ground.
- Primary winding of transformer connected to 230 V AC input.
Conclusion:
The High Current Adjustable Regulator Circuit with 30V 3A Output gives stable, adjustable voltage with overload protection and with low ripple.
The pass transistor increases current handling capacity, making it ideal for DIY electronics, lab power supplies and testing applications.