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UCC28056: PFC bandwidth crossover frequency

dushimutong
Intellectual 620 points
Part Number: UCC28056
Other Parts Discussed in Thread: UCC28050, UCC28051

Hello:
         according to your recommended PFC management chip, after reading the information carefully, I found that the data recommends that the crossover frequency of the compensation circuit (loop) be set below 20Hz. After reading the relevant information, I know that the input is a power frequency AC at about 50Hz ~ 60Hz (to achieve a high power factor ratio).
        Then if my power input is AC from 360Hz ~ 800Hz, can I set the crossover frequency to 32Hz ~ 100Hz or higher in proportion? UCC28056's internal circuit is not limited to the frequency bandwidth, or the algorithm is not suitable for higher input frequencies.
        Question 1: Are all the PFC management chips of TI the bandwidth is less than 20Hz.
        Question 2: Is this bandwidth an inherent design of the chip's internal circuit and cannot be changed externally?
        Question 3: If you are convenient, I hope to explain to me the relationship and principle of this bandwidth or crossover frequency setting and the input AC frequency. Related materials are also available.
        Question 4: Please help me recommend a wide bandwidth PFC management chip, or it can adapt to 360Hz ~ 800Hz input.

  • 0
    TI__Guru* 85926 points

    Hello,

    This UCC28056 use a transconductance amplifier.  I reviewed the data sheet and their is no information in regards to gain bandwidth product.  Generally these amplifiers are not designed for high frequency applications.  The older TI PFC controllers use to specify gain bandwidth product of about 1 to 2.5 MHz with an open loop gain of around 80 dB.  The open loop bandwidth of these amplifier would be about 250 Hz.  So this amplifier should have similar performance and crossing over at 32 to 100 Hz should be o.k.

    The reason why the data sheet suggests crossing over the loop at 10 Hz is because you don't want the voltage loop to correct for the 2Xfline = 100 to 120 Hz ripple on the boost capacitor.  This is done so you don't create third harmonic distortion that will hurt your current THD.

    I do have another suggestion as well.  It may also be worth while for you to order the UCC28056 EVM and adjust it for your high frequency design.

     

    The UCC28056 does use constant on time critical conduction PFC and I am not sure how well that will work for high frequency designs.  I do know that other customers have done designs with the UCC28050/1 that is a critical conduction PFC for high frequency designs (400 to 800 Hz).  These are also critical conduction PFC controllers that use quasi resonant control.  They control the FETs peak current and for it to track the line and also only allow the FET to turn on into zero current.

    I have discussed frequency PFC design with other customers.  They do have issues caused the phase shift in current and voltage of the input filter.  One trick to eliminate this on top of using a bridge rectifier, the design use a full wave rectifier to drive the multiplier resistor divider.  Common anode to the resistor divider and connect each anode to the separate AC input.

    The other is to use a technique call current feedforward control. I had reviewed a paper at APEC that discusses this technique and believe it requires the addition of one amplifier.   ieeexplore.ieee.org/.../1295973

    Regards,

     

  • 0 in reply to Mike O'
    Intellectual 620 points

    Hell Mike:

    Thank your reply.

               1:Is there a suitable PFC control chip that can not only generate the third harmonic distortion, but also can adapt to 360Hz ~ 800Hz AC input, that is, a higher crossover frequency (32Hz ~ 200Hz).

               2:Our ac input is a bridge rectifier.

               3:I went looking for a control chip with a full - wave rectifier ripple into the multiplier.If you can recommend a control chip with this function, so much the better.

               4:I went looking for a control chip with current feed forward control technology.If you can recommend a control chip with this function, so much the better.

               5:I don't have permission to view the papers on APEC at present. I'll look for information on current feed forward control techniques.

    Regards,

    dushimutong

  • 0 in reply to Mike O'
    Intellectual 620 points

    Hell Mike:

           Supplementary questions:

                  6：You say that other clients have done PFC designs (400 to 800 Hz) using UCC28050 or UCC28051, right?

                      Would it be convenient for you to ask the customer what is the power factor of the PFC power supply they made at the input state of 800Hz ac? Is it greater than 0.97?

  • 0 in reply to dushimutong
    TI__Guru* 85926 points

    Hello,

    I believe the PF using the full wave rectifier for their 400Hz design was greater than the requirement of 0.95. 

    Regards,

  • 0 in reply to Mike O'
    Intellectual 620 points

    Hello：Mike O'

           Thank you.

    800Hz AC input, power 10 watts, can the power factor be greater than 0.97? Because my input range is 360Hz ~ 800Hz.

    Regards,

  • 0 in reply to dushimutong
    TI__Guru* 85926 points

    Hello,

    I know that better than 0.95 has been achieved.  I am not sure about 0.97.  You might have to use average current mode control and current feedforwarded to achieve that.

    Regards,

  • 0 in reply to Mike O'
    Intellectual 620 points

    Hello Mike O'

             Thank you very much.

    Regards,