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How can I design a simple DC-DC buck step down converter with feedback

Fluffyboii

Member
This is the PCB. I tried my best but this is my first self made PCB so it may have some issues. I tried adding some extra power lines to make it withstand 10A. The diode seems like two diodes in one packade so I parallel connected them. I am not sure if it is flawless.
 

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crutschow

Well-Known Member
Most Helpful Member
The right part of your schematic is rather a mess.
You don't normally use diagonal lines or run wires through a component on a schematic, and the grounds should be at the bottom, not run clear across the schematic to the ground on the left..
The schematic should be drawn neatly, not to follow the PCB layout.

D1 should be close to Q1 on your PCB as it carries high current.
 

Fluffyboii

Member
The right part of your schematic is rather a mess.
You don't normally use diagonal lines or run wires through a component on a schematic, and the grounds should be at the bottom, not run clear across the schematic to the ground on the left..
The schematic should be drawn neatly, not to follow the PCB layout.

D1 should be close to Q1 on your PCB as it carries high current.
I fixed some of the issues with that schematic but you are right diode should be closer to mosfet. I also prepared the coil.
 

Fluffyboii

Member
Big one is 200uH at 0.3 ohm the small one 300uH not gonna use the small one anyway.
 

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Fluffyboii

Member
crutschow Should I fully remake it or is it ok as it is. I think this will be the last version, I put a lot of effort into making it better.
 

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Last edited:

Fluffyboii

Member
Am I putting the mosfet pins in wrong direction. I keep loking the diagram and I can't be sure about it. LTspice mosfet diagram arrow location seems to be reverse of the real thing. So I think I made a mistake because of it in the EasyEda diagram. Can someone check it for the ease of my mind. Maybe I am getting confused because this is a P channel mosfet.
 

crutschow

Well-Known Member
Most Helpful Member
Am I putting the mosfet pins in wrong direction.
In the LTspice schematic, the P-MOSFET source is on the left, the gate is in the middle and the drain is on the right.
Look at the MOSFET pin layout in the data sheet for the MOSFET you are using to determine if your layout is correct.
Be careful you don't confuse the top of the package from the bottom in the data sheet diagram.
 

Fluffyboii

Member
The PCB mashine at collage was broken so I made it the usual way. It works. I wasn't able to test it with 10A but seems to work well at 2A. I want to make the voltage variable if I can. I tried to use my oscilloscope to look at the comparator output and mosfet gate but I wasn't able to get anything meaningful. Does anyone know why.
 

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Fluffyboii

Member
Ok I set my oscilloscope to AC from DC and I was able to see the comparator output and mosfet gate. It actually falls in the hearable frequency range when 1-2Amps is pulled from the circuit. More current = higher frequency and at some point you can't hear it, neat.
 

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