While it is great to know how to increase voltage output from a 7812 or 7805 chip, it is actually not recommended.
These chips are designed to give a specific voltage 12V for 7812 and 5V for 7805.
There are better solutions:
If you need a different voltage, you can get a different voltage regulator chip designed for the output you need.
There are many options available.
If you are set on using these chips, you can build a more complex circuit with extra parts to boost the voltage.
But this can be tricky and is not ideal for beginners.
Circuit Working:
Parts List:
| Category | Component | Quantity |
|---|---|---|
| Resistors | 4.7k | 1 |
| 5.6k | 1 | |
| 560Ω | 1 | |
| Capacitors | Ceramic 220nF | 1 |
| Semiconductors | IC 7812 or 7805 | 1 |
| Transistor BC547 | 1 |
It is often necessary to configure a voltage regulator IC to provide a higher output voltage than its set value.
One approach is to connect the “common” terminal to the midpoint of a potential divider.
However, this method is problematic because IC regulators have a small quiescent current approx10mA flowing from the common terminal to ground.
The quiescent currents magnitude is not tightly controlled leading to some unpredictability in the total output voltage.
Lower resistor values in the divider can help but they can also cause complications related to heat dissipation and inefficiency.
The circuit presented here circumvents this issue by using transistor T1 to create a low impedance at the regulators common terminal through emitter follower action.
This setup transfers the voltage divider function to a network with relatively high resistance.
The value of R3 is not critical but must be low enough to accommodate the highest quiescent current without causing T1 to turn off.
Formula:
The formula proposes a simple transistor arrangement in which the voltage at the transistors emitter, a voltage drop of around two volts, and the input voltage Vin all affect the output voltage Vout.
How to calculate the output voltage:
Vout = Vin – 2 + (Transistor Emitter Voltage)
where,
- Vin is the voltage input that the circuit receives.
- 2 indicates the internal voltage drop of the IC.
- Transistor Emitter Voltage is the voltage present at the transistors emitter terminal.
How to Build:
Below are the steps, how to build a Increase Voltage Output of 7812,7805 ICs:
Circuit Diagram:
- Connect the input voltage to the input pin of the voltage regulator IC.
- Connect the output pin of the voltage regulator to the load e.g. a device you want to power.
- Connect the ground of the voltage regulator IC to the ground of the input voltage and the load.
Adding the Transistor T1:
- Connect the emitter of the transistor to the ground.
- Connect the collector of the transistor to the output pin of the voltage regulator IC.
- Connect the base of the transistor to the midpoint of a potential divider R1 and R2.
Adjusting the Divider Network:
- Use resistors R1 and R2 to create a voltage divider network.
- Connect the common terminal of the voltage regulator IC to the midpoint of this divider.
Adding Capacitors:
- Connect capacitor C1 between the input and ground of the voltage regulator IC for input voltage filtering.
Testing and Fine-Tuning:
- Power up the circuit and measure the output voltage.
- Use a potentiometer in place of R2 for fine tuning the output voltage if necessary.
Adjusting Component Values:
- If the output voltage is unstable or not as expected adjust the values of the resistors and capacitors accordingly.
Finalizing the Circuit:
- Once you achieve the desired output voltage finalize the circuit by soldering the components onto a PCB or a protoboard for a more permanent setup.
Note:
- Remember to take necessary precautions while working with electricity such as ensuring the correct polarity of components and using appropriate safety measures.
Conclusion:
To conclude, increasing the voltage output of a 7812 or 7805 IC can be achieved by using a voltage boosting circuit such as a voltage multiplier.
This allows for the generation of higher output voltages beyond the fixed values provided by these regulators.
However, it is important to ensure the components used in the circuit are suitable for the desired output voltage and to test the circuit carefully to ensure proper functionality.