Simple 5V Switch Mode Power Supply Circuit using IC LM2674

This Simple 5V Switch Mode Power Supply Circuit using IC LM2674 work like charger for electronics but better.

It take strong electricity which is more than 5 volt and make it just 5 volt.

5 volt is perfect power for small electronics like those tiny computer boards for projects.

Inside it got a special chip called LM2674 and this chip is easy to use and keep the 5 volt nice and steady.

So we can use this circuit and there is no need to worry about our electronics safety as they wont damage from too much power.

Circuit Working:

Parts List:

This circuit use 5V power supply called Switch Mode Power Supply which uses one chip IC from National Semiconductor.

This company is good at making these kind of power chips.

These chips are easy to use because they have good guide paper.

Many people use LM2671 or LM2674 for this.

We can get parts for 3.3V, 5V or 12V output and also some can change voltage if needed.

This power supply can give up to 500mA current and it works fast to 260 kHz switch speed.

Good thing is it not need big coil or big capacitor so it is small and save power.

Most time it work with 90% efficiency and sometimes even 96% which is very good!

These ICs also protect from too much heat or too much current with no damage.

LM2671 IC has more options it can start slowly with soft start and can match timing with other power supplies.

This help reduce signal noise like EMC problem.

This circuit makes 5V output and can give up to 500mA current.

It has diode D1 which is a special type called Schottky diode and it should be at least 45V and 3A rated.

Formulas:

The LM2674 IC is used in this 5V switch mode power circuit it is made to make voltage go down easily.

Even this chip does many things by itself it is still good to know some basic formula to help with checking how it works and choosing parts.

Inductor Value (L):

L = (Vout * (Vin – Vout)) / (ΔI * fsw)

where,

• L is coil value in henrys.
• Vout is 5V for output voltage.
• Vin is input voltage which is between 8V to 40V.
• ΔI is ripple current which is usually 20–40% of output current.
• fsw is switch speed for 260 kHz for IC LM2674.

Be sure coil can take more than 500mA current.

Choosing Output Capacitor (C3):

C3 = Iout / (ΔVout * fsw)

where,

• C3 is capacitor value in farads
• Iout is output current which is 500mA.
• ΔVout is small change for ripple in output voltage.
• fsw is switch frequency at 260 kHz.

Bigger capacitor means less ripple.

Efficiency Formula:

η = (Pout / Pin) * 100%

where:

• η is efficiency in percent.
• Pout is the Vout × Iout
• Pin is the Vin × Iin

Note:

This is short and basic information for exact numbers and better design we need to check the LM2674 datasheet.

Also try using simulation tools to help test the design.

How to Build:

To build a 5V Switch Mode Power Supply Circuit using IC LM2674 follow the below mentioned connections steps:

Choose Parts:

• Pick inductor, capacitor and resistor values by checking LM2674 datasheet.
• Choose should be based on what we need like output voltage, current etc.

Make Circuit Layout:

• Build the circuit on breadboard or PCB and follow layout advice from LM2674 datasheet for best working.

Connect Parts:

• Put all parts together same as circuit diagram in datasheet or application notes.

Power In and Out:

• Give power to pin 7 of LM2674 DC input and connect the load output to pin 8.

Test the Circuit:

• Turn the power ON and check output voltage and current and be sure they match what we need.
• Also check if LM2674 get too hot it should stay cool or warm but not too hot.

Finish Up:

• If everything works good then fix layout and wires properly.
• If LM2674 gets hot if possible maybe add heat sink to keep it cool.

Note:

• Always check the LM2674 datasheet for correct information and follow all tips for best results.d application notes for detailed instructions and specifications specific to your application.

Conclusion:

Simple 5V Switch Mode Power Supply Circuit using IC LM2674 is simple and works well for making 5V switch power supply.

It is easy to use and gives steady output, so many people like to use it for different projects where 5V is needed.

References:

LM2674 SIMPLE SWITCHER