ADP1047 predetermined loop BW

I read some answers such as "since ADP1047 is designed for PFC, its loop bandwidth is slow".

This is how the traditional boost circuits work.

But why would you predestine a whole new part for such a narrow application?

This slow BW comes from the fact that the output of ALL 60  Hz single phase has awful line harmonics.  Even gazzillion mF wont kill that . BUT there are new topologies that do not have this limitation.

So then how can I modify this predestined limitation?

What is the way to design loop BW according to the power stage? Through the GUI?

BTW:  can multiple ADP1047 chips be synchronized? How?

thnx

robin

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  • Hello Robin,

    The ADP1047/8 was released in 2012 and is for single phase, interleaved and bridgless boost PFCs.

    Can you please give me an example where you want a very fast voltage loop? You can increase the bandwidth of the voltage loop as much as you like but  there is a limitation in the current filter design that does not allow you to place the zero beyond 50Hz.

    To answer your other questions:

    1. Yes, the filter settings are programmed through the GUI

    2. For SYNC, it is possible to SYNCronize 2 ADP1047/8 together using the SYNC pin.

    Lt. Comm. Data.

  • LT: I will have 18 ADP1047/48 running in this system. How would I  to synchronize these in the following  manner

    - 6 of these in same phase

    - 6 of the next set out of phase by 120 deg

    -rest out of phase by 240

    There used to be a chip that gave  out of phase signals ....but just cannot retrieve it by searching. Is that chip  taken out  of  parts made by ADI/LT?

    Of course, question remains how  to do it in circuit.

  • Please see the GUI PWM settings to SYNC several ADP1048s with appropriate phase delay. Also see attached. Essentially, you send the same SYNC pulse to all the ADP1048s and in the GUI you can set the phase delay.

    From what you are describing what you need is just a simple boost converter and the ADP1048 is a power factor controller and hence the poles and zeros are so low as you have found them in the controller. Seems like you are more interested in output ripple cancellation than reducing THD. Do you need power factor correction? What is the total output wattage? Also, what is the reason for putting 18 in parallel?

  • ltcommdata

    thnx much. 

     

    power stage we have offers far superior Pfc & far lower THD than boost with no variation in pwm to extremes. It is operated at some duty say 40% & the controller essentially does ‘delta variation’ to have output controlled

    current shaping happens because of the resonant power stage. and far outperforms boost or SVM.

     

    why 18?

    each single phase ( to neutral ) gives 1kW with transformer isolation.

    3 such  paralleled will naturally givve 0 ripple ( a bonus) PLUS 3kw with  minimal output cap & NO DC inductor.

    we need 18 kW PFC stage. Hence 18 such single PFC in parallel each with a controller.

    In truth, they need not BE  in sync.

    But there are significant advantages if they do.

    This power stage due to isolation allows paralleling easy. 

     

    these are significant benefits of  our approach  all said& done.

    1) no inrush, no need to slow start.

    2) no stored energy by dc inductor - fast loop

    3) no line frequency at the output. This is a million fold bonus in aerospace.

    4) fixed freq operation with almost constant PWM- only varied by feedback to control.

     5) no stress or reflected ripple to the generator side. 

    6) truely bridgeless, resonant operation.

    7) isolated outputs of any value by turns ratio selection.

    Limitations: of course...but that is not visible to this design.

    hope this answers your curiosity about our power stage. 

     

    Then you see why very nominal change in the boost code through the GUI to essentially remove boost imposed limitations will give rise to a really novel PFC system and product. Based upon ADI1047( or 48) and easily programmable thru GUI

    ONE REMAINING challenge is that current waveform is quite different. If this post is private, I can send you all these info since we gave an NDA.

    But this calls for real explanation of exactly how the digital controller processes the current waveform. IN analog controller  data sheets such as LT1509,  they never explain what is critical in producing PWM.  One thing I know, the return current better pass through RS to be negative & of low value. In digital I know you add a level shift to make it positive. 

    But this leaves a lot of questions unanswered. I could never make LT1509 work with my power stage. Analog controller just does not have the flexibility to adjust to different current waveform.

    But I can  tell you, ADP1047 ought to work if we know what to modify. 

    When it does, you will have a unique  application & an excellent system.

    Let me know.

  • LTComm: any hope  they can tell me how to set up the ADP1047 for our power stage? I am at a point where a major decision has to be made to keep hoping or hop out. If the answer is a clear  NO- no one will help to adapt . That will kill it as well. It will remain a sad episode. Because there is so much potential for its reuse.

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