This is 0-30V 5A variable benchtop power supply circuit, with voltage and current adjustable system. The output voltage 0-30V and a maximum current of 5A. Use LM723 as a voltage regulator designed primarily for series regulator applications. By itself, it will supply output currents up to 150 mA. So need to use two transistors 2N3055 for boost up current to 5A. CA3140 for Control Current and Voltage output in easily. And full overload protection.
- P1-50K for control current
- R20-50K for Adjustable output voltage
- R19-5K for fine Adjustable voltage output
- Transformer—use 5-8A at 32V and 18V voltage. Read more below!
Note: This circuit is not suitable for the beginner. It is best for professional only.
How it works
In the 0-30V 5A regulator circuit below. It uses a precision voltage regulator system.
LM723 is the main part to control the output voltage precisely by itself.
Note: I am sorry that tell you. I never build this circuit. So, I cannot confirm it works. If you are looking for 0-30 variable power supply.
I recommend this circuit better. It tested.
Also, You can increase current up to 5A with adding a transistor like this.
This circuit has 2 unregulated power supply, 43V, and 24V.
It gets the AC voltage of 32V from transformer secondary. To rectify with a bridge rectifier, four 5A diodes.
They power a positive voltage to a collector of two the power transistors, 2N3055. Both transistors are connected in parallel to increase the high current to the output load.
But in beginning, 2N3055 does not conduct. Because they need to biased current from Q3-BC337 first.
So, we need to have another rectifier one.
This is a power supply for a control voltage regulator system. To begin with, we rectify the 18VAC from the transformer into 24V DC using D3-diode and C5-filter capacitor.
Then, the 24VDC comes to resistor-1K to power to pin 12(V+) and pin 7 (V-) of LM723.
While the 24VAC also powers CA3140 op-amp IC at pin 7(V+) and pin4 (V-). This is a limiting current system of this circuit.
When the 24VDC flows through 1K resistor pin 11 (VCC) of IC1. It makes the transistor inside can supply voltage output of pin 9.
So, there is a voltage to bias the base of Q3 transistor. It is working to conduct current from 24VDC through resistor 200Ω 1W to C-E of that transistor.
It results in both transistor 2N3055 get a biased current. So, they can power the current to the output.
Block diagram inside LM723
Look at in the block diagram inside uA723. This voltage can be controlled by comparing the voltage pin 4 and pin 5.
Which both inputs of op-amp have 2 pins. Pin 5 is non-inverting and Pin 4 is inverting.
For pin 6 act as set the reference voltage.
If you want to change the output voltage. You change the voltage at pin 4 and pin 5.
In this circuit, we should choose to adjust the voltage at pin 5. Because it controls the voltage in a linear positive.
If the pin 5 voltage rises up. It makes the output pin 9 is positive up. Of course, there is a lot of biased currents.
Which we can rotate the potentiometer 50K to adjust the output voltage 0-30V in normal and 5K in fine adjusting.
CA3140 is Bi MOSFET Operational Amplifier, it acts as limit the current in this circuit. If the current is more than 5A. This will cut off the regulator immediately—with stopping 2N3055 transistor working.
How it works?—We use a comparing voltage between pin 2 and pin 3. When the transistor Q1 works over current than normal. Then, pin 3 will compare the voltage with pin 2.
It makes the positive voltage out of pin 6 to bias the base of BC549. Then, BC549 pull the voltage at pin 13 of LM723 down and no output voltage. This circuit safe.
Parts you will needs
Q1,Q2: 2N3055- 15V 60V transistor
Q3: BC337-0.8A 40V NPN transistor
Q4: BC549-0.4A 40V NPN transistor
0.5W 5% resistors Except special
R1, R3: 1.2Ω 5W
R4: 100Ω 5W
R6: 2.2K 5W
R8: 100Ω 1W
R9, R10.: 1K
R11: 150Ω 0.5W
C1: 2,200μF 50V
C3,C4,C5: 220μF 50V
C7: 47μF 50V
How it builds
First of all, we should get all the components on the lists below. Then, get the PCB. You can also use a perforated board. Look at the PCB layout and the components layout.
Warning! This circuit is not suitable for newbies. You can look at 0-50V 3A Variable power supply
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