UCC3818A：DUAL AC INPUT PFC PARALLEL

Hello Andy,

Thank you for your interest in TI products. I do not think that your design will work well. You cannot simply tie multiple boost PFC outputs together. If you do, then your THD and PF will be poor. You need to track the current and phase of the AC input. Real world AC inputs will have common GND references so tracking multiple AC inputs will not work. 

One possible solution is to have each AC input go into a separate PFC stage. Each PFC stage will then go into their own isolated DC/DC converter (Ex. an LLC or PSFB stage). The outputs of each isolated DC/DC converter can then be connected to each other. If you are using an analog controller, the UCC28070A is ideal since it has SYNC capability, which will be useful.

For 3-phase AC, you can use a UCD3138 or C2000 MCU in a 3-phase PFC, such as a Vienna Rectifier. Here is one such reference design: https://www.ti.com/tool/TIDM-1000 

Please see the following E2E threads for more information

• UCC28070: Recommended Boost-PFC Controller devices for 3-phase AC Input: https://e2e.ti.com/support/power-management-group/power-management---internal/f/power-management---internal-forum/1304693/ucc28070-recommended-boost-pfc-controller-devices-for-3-phase-ac-input/4956466?tisearch=e2e-sitesearch&keymatch=3%20phase%20analog%20pfc#4956466 
• 300W PFC with input 3 Phase (Delta, 3 wire) 220VAC, L-L, 50Hz: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1279328/300w-pfc-with-input-3-phase-delta-3-wire-220vac-l-l-50hz/4852458?tisearch=e2e-sitesearch&keymatch=3%2520phase%2520analog%2520pfc#4852458 
• Need controller for 3 Ph PFC to be implemented on a per phase basis: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/478335/need-controller-for-3-ph-pfc-to-be-implemented-on-a-per-phase-basis 

Regards,

Jonathan Wong