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UCC28070

James Tantillo
Prodigy 40 points
Other Parts Discussed in Thread: UCC28070

I am running a ucc28070 for a product which we are trying to make multivoltage as well as multiphase. right now it is designed for a 187-506 VAC input on either 1 or 3 phase input. I am having no issues with any of the single phase inputs nor is there a problem on the higher (400-506) voltage three phase variants. Where I am currently having an issue is when the input is at the lower input voltages on three phase. I have tried 208- 230 VAC and there have been two different scenarios. one where the bus voltage drops all the way to the level of the Rectified DC of the input, somewhat recovers, then drops again until our protection scheme disables output. The second scenario (after I re-tuned the voltage and current loops) is that the voltage dips, rises to the OVP level then drops again to the rectified line level until the software shuts down our main inverter load. I am at my wits end trying to figure out a solution to what I am seeing.
I need to know what to try next.

Thank you,

Jim

  • 0
    TI__Mastermind 34465 points
    Running the UCC28070 from a 3 phase supply will result in almost a peak rectified voltage signal on the VINAC pin. The problem is that the UCC28070 expects to see a voltage that transition to 0 V on this pin.
    You need to add circuitry to the VINAC sensed voltage which will decrease the sensed voltage to 0 V around the line transitions. The transitions to 0 V need to have a relatively slow slew rate.