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UCC2818-EP: PFC APPLICATION TO DC CONVERSION OF 3 Phase 400 Hz 115V AC Input with 6 Diodes

Cihangir Öksüz
Prodigy 75 points
Part Number: UCC2818-EP
Other Parts Discussed in Thread: UCC28070A

Hello,

I will rectify the 3 Phase 400 Hz 115 VAC input supply to DC (270 VDC) with the bridge rectifiers shown in the figure, and then apply boost PFC to 450 VDC with the UCC2818-EP integrated circuit. In this case, the ripple frequency will be 2.4 kHz. There is no restriction regarding line frequency in any PFC control IC. Another reason why I do not prefer UCC2818-EP is that its temperature features are suitable for application. Is UCC2818-EP suitable for this application?

Kind regards.

  • +1
    TI__Mastermind 32050 points

    Hello Cihangir, 

    Thank you for your question on using the UCC2818-EP at 400Hz. 

    Yes, the UCC2818-EP controller is suitable for your application. 
    Please be aware that PF and THDi will not be as good as a 1-Phase AC input using the same controller. 

    The input current of each phase of the rectified 3-Phase line will look similar to this: 

    They will not be sinusoidal currents because of the way the bridge rectifier sequences the currents in the 3 phases:
    The PFC controller will shape line current to follow the rectified line voltage that appears at the (+) and (-) outputs of the bridge.
    Because there are 3-phases being rectified, the full sine shape of each voltage does not appear at the bridge output. 

    Only the difference in phase voltages appears there, and that ripple is what the PFC controller has to work with to shape the current.   

    Phase-currents I2 and I3 will be the same as I1, but shifted 120-degrees.

      Regards,

    Ulrich

  • 0 in reply to Ulrich Goerke
    Prodigy 75 points

    Hello Ulrich,

    First of all, thank you for your quick return. There is another issue that comes to my mind. If the input voltage source of the PFC circuit is a clean DC voltage supplied from the battery rather than a fluctuating DC rectified from AC, will the UCC control integrated continue to work as a boost converter? In other words, will giving the PFC input voltage directly from a DC source cause the control IC to not work properly?

    Kind regards.

  • +1 in reply to Cihangir Öksüz
    TI__Expert 6010 points

    Hello Cihangir,

    Uli is out of office so I will cover for him. 

    Are you asking if it is ok to use a DC input to the PFC circuit and if the UCC2818-EP will continue to work properly? If so, then the answer is yes. The UCC2818-EP will operate as a normal boost converter if the input is just DC. This is helpful for debug purposes since you can test if your controller is working as a boost converter before trying to rectify the AC voltage.

    While a PFC controller will work just fine as a regular boost controller with a DC input, it will be cheaper and simpler to use a dedicated boost controller if that is your goal. 

    Regards,

    Jonathan Wong

  • 0 in reply to Jonathan Wong
    Prodigy 75 points

    Hello Jonathan,

    First of all, thank you for your quick return. Can you recommend a buck or boost controller for a system with a target input range of 150-450 DC? (Operating temperature range -55 +125)

    Kind regards.

  • 0 in reply to Cihangir Öksüz
    TI__Expert 6010 points

    Hello Cihangir,

    I will redirect this E2E post to the boost controller experts.

    Also, as a correction, not all PFCs will work as a simple boost controller with DC input. Some PFC controllers require a zero crossing in order to work. For example, the interleaved CCM PFC controller UCC28070A may require a zero-crossing detection with the VINAC pin. See below footnote in page 10 of the UCC28070A datasheet:

    Regards,

    Jonathan Wong

  • 0 in reply to Jonathan Wong
    TI__Guru 61245 points

    Hello Cihangir,

    What output power are we talking about?

    We only can recommend non-synchronous boost controllers for this high voltage and then the power is really limited. In addition, the output voltage of the boost controller needs to be higher than the input. Only if you create a flyback converter with the boost controller, the output can be lower than the input voltage.

    Best regards,
    Brigitte