EEVblog® Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: hsquared on May 01, 2026, 11:27:07 pm
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I am designing a LM5176 buck-boost. I ran into an issue where the pre-bias isn't working as smoothly as I had hoped. (If Vin turns on while Vout is still high for whatever reason, the controller tries to reduce Vout by driving negative current).
I wanted to overcome this by just creating a latching circuit that disables the controller until Vout falls low enough.
I created this BJT circuit that I believe works. I was wondering what this type of "design" is. Is there a name for this type of design or methodology? And is this a good method to solve this problem?
I created a table to remind myself what the circuit should do.
Vin, Vout, (EN/UVLO)', EN/UVLO
H, L, X, Vin - Vin turned on, Vout is low, EN/UVLO should track Vin
L, H, X, L - Vin low, Vout still high, EN/UVLO should latch low
L, L, X, Vin - Vin low, Vout fallen, EN/UVLO should track Vin
H, H, Vin/H, Vin - Vin and EN/UVLO were high, Vout turned on, EN/UVLO should track Vin
H, H, L, L - Vin high, Vout high but EN/UVLO was latched low, so EN/UVLO should continue being latched low