EVLVIPGAN50PD Modification for Standalone 12V Power Supply

[TIENHUA]

Hi Sir,

I would like to explore a specific use case that deviates from the standard design. My goal is to modify the EVLVIPGAN50PD to achieve a fixed 12V output, bypassing the USB PD negotiation functionality entirely. My intention is to utilize only the motherboard circuit, which contains the VIPERGAN50 and SRK1001, and not use the daughterboard with the STUSB4761 controller.

Could you please provide some technical guidance on what modifications would be necessary to the motherboard circuit to achieve stable 12V regulation? Since the voltage feedback loop is currently managed by the STUSB4761 on the daughterboard, I assume changes would be required to establish a fixed reference for the VIPERGAN50 on the motherboard.

For example, on the daughterboard schematic, a resistor divider (R36 and R37) is used for voltage sensing. I am wondering how a similar feedback mechanism could be implemented directly on the motherboard circuit to set the output to a constant 12V.

Thank you.

[Peter BENSCH]

Please take care: R36/R37 is not used for voltage sensing! The optocoupler U3.2 is connected to J4.1, from where the VIPERGAN50 is controlled. You can regulate the desired fixed voltage via this pin using the classic approach with a TS431 or similar. Circuit examples can be found in the data sheet of the VIPERGAN50 in fig. 33 and 34.

Hope that helps?

Regards
/Peter