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UCC28180: Function Discussion

Part Number: UCC28180
Other Parts Discussed in Thread: UCC3818, , UCC28019

Dear Team,

Here is Kevin from the Delta Taiwan team.

1. Why this PFC pre-controller doesn’t have Vin-sense and input current sense?

How does it achieve shaping input current without input voltage sensing?

From the previous design, there are input sense to multiple Imo to shape current, I have no idea how to shape current if without input voltage information.

 

2.What does the meaning of Reduced current sense threshold (minimizes power dissipation)?

Could you give me an example compared to UCC3818?

 This function seems what we need to achieve high efficiency.

 

3.If I want to measure the loop gain of the demo board how to measure?

 Please teach us how to measure open and close loop including current and voltage.

4. Could you teach us how to use Tina to simulate the UCC28180's bode plot?

Base on TI's website TINA circuit I can see the preliminary result.

a. I am not sure how to change the output resistance to achieve load transient test

b. How to check iTHD(even the simulation mention it have simulate iTHD)

c. How to test the bode plot

Customer would like to test below items:

(load transient , iTHD, Loop gain and phase)

 

BR

Kevin

  • Hello Kevin,

    Thank you for your very in-depth questions.  I will see what I can do to help.

    Please see my answers below.

    Dear Team,

    Here is Kevin from the Delta Taiwan team.

    1. Why this PFC pre-controller doesn’t have Vin-sense and input current sense?

    >The UCC28180 uses a technique for developing PF that does not require a multiplier.

    >This device is similar to the UCC28019 that has fixed switching frequency of 65 kHz and sense the line voltage for brownout shutdown.

    >The line sensing was removed on the UCC28180 so you could program the switching frequency.

     

    How does it achieve shaping input current without input voltage sensing?  I found this application note on line that explains why the multiplier was not needed.

    From the previous design, there are input sense to multiple Imo to shape current, I have no idea how to shape current if without input voltage information.

    I found this application note on line that explains why the multiplier was not needed at the following link.

    Multiplierless PFC Operation (1).pdf

     

     

    2.What does the meaning of Reduced current sense threshold (minimizes power dissipation)?

    P = (I^2*R) = (V^2)/R

    The VPCL is 0.4V typical which means the nominal current signal is less than 400 mV.  Older devices had this to be over a volt.

    Could you give me an example compared to UCC3818?

    This function seems what we need to achieve high efficiency.

    This old device generally used a current sense signal of 700 mV, which is 1.75 times greater than the UCC28180.

    P = (I^2*R) = (V^2)/R

    3.If I want to measure the loop gain of the demo board how to measure?

     Please teach us how to measure open and close loop including current and voltage.

    I found an application note on the web at the following link that you might find useful that describes how to compensate PFC current and voltage loop.

    https://www.ti.com/lit/an/spra902a/spra902a.pdf

    4. Could you teach us how to use Tina to simulate the UCC28180's bode plot?

    Base on TI's website TINA circuit I can see the preliminary result. This is similar to Spice and I found this article on the WEB that shows how to compensate the loop using PSPICE.

    https://www.youspice.com/straightforward-method-design-simulate-spice-loop-compensation-controller-switching-power-supplies/

    a. I am not sure how to change the output resistance to achieve load transient test

    > I believe Tina has voltage driven current source, you just need to apply a square wave to it.

    b. How to check iTHD(even the simulation mention it have simulate iTHD)

    > I searched TI Tina's help and it does not have a power analyzer function so measure iTHD is not possible with Tina.

    c. How to test the bode plot

    Customer would like to test below items:

    (load transient , iTHD, Loop gain and phase)

    The application notes on should help with loop gain, phase and load transients.  THD he will not be able to predict with Tina.  I do find that compensating the loop is best done on the bench with a network analyzer.  I know that it can be done with simulation modules but I really have not compensated a voltage this way.

    Regards,

    BR

    Kevin