UC3843: CC mode in UC3843 boost converter

Hi,

I modified the circuit and it worked ok. It looks your circuit has several things not correct. Most critical are VFB not correctly connected, R1 = 10k too big.

The below is the result based on my simulation 30Vin and 60Vout. 

There are other issues in your circuit But I could not have time to study. So I changed some of the circuit with what I know to work for sure - so the IC model is correct. The remaining work of your circuit needs to be adjusted by yourself.  The circuit I modified and worked is attached.Boost_ucc28c42_30Vin_60Vout.TSC

Hi,

It looks to me the reason is like the below:

The sensing on R8 needs to reach 2V, to match U3 ref 2V. 2V on R8 produces 2A which also flows through R12. So the resulted Vout = 4V < 30Vin.

The converter is in the boost topology not able to regulate Vout =4V, so not able to achieve the CC with the circuit you show.

Hi,

Fundamentally, the capacitor you added will be charged up since the capacitor flowing a dc current, you won’t get a CC. It looks this capacitor cannot solve the issue.

For CVCC, can you look at UCC28704, UCC28740, or UCC28730, these devices are dedicated for battery charge.

No matter what you want to move, I suggest not to spend time on that added capacitor since it won’t help to get CC operation for battery charge.