[Moved] 5v to 4v buck converter

[Afzal Hossain Khan]

Hello,
Recently I'm designing a circuit where I need 4v and 2A to operate my circuit.My input range is 5V - 12V. I need a smps which can convert 5v to 4v and remain 2A current for the circuit.I used lm2576 , but when the input voltage is bellow 6v , It cant provide 2A current .Please suggest me a smps or any things else to resolve this problem.

 

[amayilsamy]

What is the max power of input supply?
And chek your coil value.

 

[zerealbigboss]

Hello,
Recently I'm designing a circuit where I need 4v and 2A to operate my circuit.My input range is 5V - 12V. I need a smps which can convert 5v to 4v and remain 2A current for the circuit.I used lm2576 , but when the input voltage is bellow 6v , It cant provide 2A current .Please suggest me a smps or any things else to resolve this problem.

Any smps has an internal voltage loss, which in general is around 1.3V. That is also why you never will get a lower output than 1.27V with the 2576, as per specs. As the regulation needs an additional voltage to regulate properly you will need an input voltage that is at least 2V higher than the output. If you insist on using less than 6V for an output of 4V, you will have to go for a linear discrete voltage regulator with a MOSFET in the power line, but then you will have to take care for proper cooling ((12-4)*2=16 Watt heat loss in worst case). A simple design with one zener, one transistor and one MOSFET will do. You can find many of them with a power transistor on the net; This one has a drop-out of just 1V, so that might serve: https://www.learningelectronics.net/circuits/discrete-voltage-regulator.html. You will not have a short-circuit protection, though, because that also increases the drop-out.

 

[FlapJack]

Webench will design the circuit for you.

https://www.ti.com/lsds/ti/analog/webench/overview.page?DCMP=sva_webench&HQS=webench

I will try posting the schematic and BOM that i got.

 

[zerealbigboss]

https://www.learningelectronics.net/circuits/discrete-voltage-regulator.html.

I forgot to say that you should take a zener diode of 4.7V and leave the potentiometer out; the output will then be (4.7-Vbe)=4.1V. If you take a zener of 3.3V and leave P1 in, you can adjust the output to what you want.