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Created December 09, 2019
Last modified December 09, 2019
Tags buck   buck-regulator   converter   lm358  


Buck regulator using LM358 and MOSFETTs for switching. Includes voltage and current limit control


Provides 0v-20v DC with current limiting function from 24v and 5v DC input

M1, D1, L1 and R7 will determine the max current.

R7 is the sense resistor so should be able to handle getting hot since it can be dissipating over 10w of heat at 10a loads

D3 should give somewhat of an indication when current limiting is applied

The circuit employs M2 as a signal inverter as well to be able to drive a high power MOSFETT from a 5v signal but this also means that the switch will be normally closed if the op amp circuit fails and might cause an issue if you care about that.

The main logic of this circuit is the op-amp will turn off to raise the output voltage and turn on to lower the output voltage. This allows to combine voltage and current limiting without more logic I think. Since this circuit acts as an oscillator the frequency is limited by C3

Due to the high capacity of C2 it's possible when changing load or adjusting voltage/current that it delivers more voltage/current than desired for a short time, could probably improve on the output filtering but I opted for large capacity in cases when I wanted more current

Strongly suggest using active cooling for M1 and D1. M2 should have passive heatsink


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