Site icon Circuit Ideas for You

LM2678 Based 5V DC-DC Buck Converter Circuit

This is LM2678 Based 5V DC-DC Buck Converter Circuit

It makes 5V DC-DC buck converter.

Buck converter changes high voltage to low voltage by switching.

LM2678 IC chip is very efficient step-down regulator and it can give 5A output current.

Circuit efficiency is more than 90% and it works good with load and voltage changes.

LM2678 IC have three fixed output like 3.3V, 5V, 12V and also have adjustable output.

It has features like thermal shutdown, current limit and ON/OFF control.

Power input is from 8V to 40V DC.

This article show how circuit work, design calculation and to build 5V buck circuit with LM2678.

Circuit Working:

Parts List:

ComponentSpecificationQuantity
Capacitors
Electrolytic 15µF 50V3
Electrolytic 180µF 25V2
Ceramic 0.01µF1
Ceramic 0.47µF1
Semiconductors
IC LM26781
Inductor Coil 22µH1
Schottky Diode 6TQ045S1

Circuit uses IC LM2678 step-down regulator chip.

Input voltage is from 8V to 40V change to steady 5V output.

This regulator works as switch mode with more efficient than normal linear.

Input DC voltage is from 8V to 40V.

Three capacitors C1, C2, C3 clean input voltage and reduce noise and spikes.

LM2678 IC control voltage and switch current through inductor L1 fast.

Capacitor C4 connect pin 2 for frequency stable.

Inductor L1 save energy when switch ON and give energy when switch OFF to keep current flow.

Pin 7 is ON/OFF switch and if connected to ground the regulator turn OFF.

Diode D1 give path for current when switch is OFF and saves energy.

Capacitors C6 and C7 smooth output and makes stable 5V DC.

Formulas with Calculations:

Formulas for LM2678 5V buck converter:

Inductor l calculate by:

l = (Vout * (Vin – Vout)) / (f * Iout * Vin * k)

where,

Put values:

l = (5 * (12 – 5)) / (260000 * 5 * 12 * 0.3) = 22µH

Output capacitor Cout calculate by:

Cout = (Iout * k) / (f * Vripple)

where,

Put values:

Cout = (5 * 0.3) / (260000 * 0.05) = 115µF

Use two 180µF capacitors for better performance.

How to build:

To build a LM2678 Based 5V DC-DC Buck Converter Circuit follow the below steps:

Conclusion:

LM2678 Based 5V DC-DC Buck Converter Circuit is strong step-down regulator.

It gives 5A output with high efficiency.

Switching design is less with heat loss.

Circuit is good for microcontrollers, battery devices, and industrial electronics.

Use right parts like inductor, capacitors, diode for better performance and for stable work.

References:

LM2678 SIMPLE SWITCHER® High Efficiency 5-A Step-Down Voltage Regulator

Exit mobile version