uc3843 buck-boost

Thread Starter

mrh586

Joined Dec 5, 2021
90
I also currently building sepic converter for input voltage 8.5v(minimum uc3843 supply) to 24v and output to 2.5v to 24v. Mosfet FDP036N10A (100 V, 214 A, 3.6 mΩ). I'm expecting to get 150 watt output and 10A max current. At 12v input, I'm testing 12v 6A load by halogen lamp, Input current show 8.5A (efficiency about 70%). But inductor and R sense get hot. I have trying to rewinding different inductor with different core color (yellow-white, green-blue and blue), size and turns. But all have same issue. So i think that sepic converter is not suitable for such high power application.
I have noticed about 4 switch buck boost non inverting converter for higher power, with single inductor. But circuit is seem so complex and i hate that.
I also meet same issue like yours, when output get drop. Try to increasing R sense > 0.05ohm, increase input bulk capacitor above 2200uf or adding one npn transistor at pin 4 to pin 3 as loop compensation.

For reference, see https://danyk.cz/univ_m_en.html
Maybe it will help.
I have done almost all of these things
But my problem is that the MOSFET is too hot
And currently at 40 volts, when I connect a 13 amp load to the circuit, I have a 20 volt drop
The cores in miner power supplies (black) are very resistant and do not get hot at all
Try to use them
I am working on the circuit every day and I will definitely let you know if I get the result
 

Thread Starter

mrh586

Joined Dec 5, 2021
90
Back in post #110 I asked for a scope trace of the voltage across the current sense resistor.
I read the post you mentioned very carefully
After making the 10x probe, I posted the photos in post 114
Now tell me exactly what you need for me to prepare
 
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