How to Convert 5V to 3.3V Circuit

Have you ever tried to use a toy that needs less power 3.3V with a charger that gives too much power 5V?

A 5V to 3.3V converter circuit is like a special adapter.

It takes the strong power 5V and weakens it 3.3V to the perfect level for your electronic device.

This is useful when you have a power source, like a USB port that gives more voltage than what your device needs.

There are different ways to build these converter circuits, each with its own pros and cons.

Circuit Working:

Parts List:

This article is a very basic 5V to 3.3V converter circuit, that uses diodes and a resistor in series.

Due to the voltage drop across each diode around 0.7V, the output voltage will be lower than 3.3V likely around 2.2V.

Additionally the efficiency of this circuit is very poor because the excess voltage is simply wasted as heat across the diodes.

This circuit can only supply a small amount of currents, typically around 10mA.

If you need to deliver more current, you will need a more sophisticated circuit design.

The output voltage will vary depending on the input voltage and the current draw.

Here are some better alternatives for converting 5V to 3.3V:

A voltage divider is a simple circuit, made with two resistors.

It is inexpensive and easy to use, but it is not very efficient for supplying current.

A linear voltage regulator is a more efficient option than a voltage divider.

It can supply more current and provide a more stable output voltage.

A switching regulator is the most efficient option, but it is also the most complex.

It can supply a wide range of current and provide a very stable output voltage.

Formulas and Calculations:

You may use the following procedures and calculations to convert 5V to 3.3V using a resistor voltage regulator and Zener diode:

Get Resistor Value R:

The voltage drop across the resistor VR and the intended current through the Zener diode Iz are used to get the resistor value.

The Zener diodes current Iz may be roughly calculated as follows:

I_z​ = V_in​−V_out​​ / R

here in our circuit,

• Vin stands for the input voltage 5V and Vout for the intended output value 3.3V.

One may compute the resistor value R as follows:

R = V_in​−V_out​​ / I_z

​Example Calculation:

Assuming a desired Zener diode current Iz of 30 mA (0.03 A), let us create a 5V to 3.3V voltage regulator utilizing a 3.3V Zener diode:

R = (5V−3.3V) / 0.03A ​ = 1.7V​ / 0.03A = 57Ω

Round to the nearest standard resistor value, such as 47Ω or 68Ω depending on availability.

Note:

Make that the resistor and Zener diode are rated for the amount of power dissipation.

Check that the output voltage remains stable with different loads.

The power rating of the resistor need to be sufficient to manage the computed power dissipation, which is expressed as follows: P_R ​= I^2​_z * R

For precise voltage control, take into account the resistor and Zener diode tolerance levels.

Using simple parts like a resistor and Zener diode, this design offers an efficient way to step down from 5V to 3.3V.

How to Build:

How to Convert 5V to 3.3V Circuit below mentioned are the simple steps for connections:

• In circuit A three 1N4148 diodes are connected in series to the positive terminal.
• In circuit B a 47 ohm resistor and a zener diode is connected in series with the output supply to negative supply.

Here are additional details, about the components listed in the diagram:

3x1N4148: 

• These are 1N4148 diodes.
• They are small signal diodes commonly used in general purpose applications.

3v2 70mA: 

• This likely indicates a 3.3V source that can deliver up to 70mA of current.
• However, this source is not directly part of the circuit.

3v3 30mA: 

• This likely indicates another 3.3V source that can deliver up to 30mA of current.
• However, this source is also not directly part of the circuit.

47 R: 

• This is a 47 ohm resistor which limits the output to 30mA.

Conclusion:

To conclude, 5V to 3.3V converter circuits allow you to power devices designed for lower voltages from a common 5V source like a USB port.

The choice of converter depend on your specific needs.

References:

How to convert 5v TTL to 3.3v and vice versa?