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TMS320F280025C: PSFB PCMC based on TIDM-02000

Masaru Maeda
Prodigy 20 points

Part Number: TMS320F280025C
Other Parts Discussed in Thread: TIDM-02000

I am trying to PCMC_PSFB used F280025 with reference to TIDM-02000.(Example Projects:TIDM-02000-Peak Current Controlled Mode PSFB DC-DC Power Converter)
It works fine normally, but I have a problem and I want to solve.

The waveform immediately after enabling PWM is not ideal.
As shown in the figure below, [Q1 and Q3] or [Q2 and Q4] are turned on at the same time.
At this time, current will flow to the primary side.

The waveform from the second cycle is ideal for me.
How can I output a waveform like the second cycle from the beginning?


I haven't changed much from the Example Project.
The settings are as follows.

PSFB_INCR_BUILD = 2 (Closed Voltage Loop Check)
PSFB_SR_mode = 1
Dead-Band = 1us(Temporary setting)
PWM frequency = 100kHz


The PWM enable method is as follows.
(Same as Example Project)

Is it possible that one of the causes of this problem is that PWM2 is always output?
If so, do you know a good way to stop the PWM2 output?

Regards,

Masaru,

  • 0
    TI__Genius 16035 points

    Hi Masaru,

    Could you please explain why this is not ideal? Is that because you will have a current going through the transformer in a short time and create some output voltage? 

    By looking at pic 2, it is not only related to PWM2B output (always on, we have a workaround for it which I can show you later). I need to look into this issue and try to get back to you this week.

    Regards,

    Chen

  • 0 in reply to Chen Jiang ti
    Prodigy 20 points

    Dear Chen,
    Thank you for your reply!

    You are right.
    I do not want to overlap diagonal switches("Q1 and Q3" or "Q2 and Q4") immediately after PWM enabled.
    However, i think i was able to fix the software today and improve it.
    I had not noticed any difference in the ePWM specs between 28002x and 28004x.
    So I was not able to set SYNCI for the slave PWMs.

    I configured as follows.

    // EPWM1 = Master(CTR = zero), EPWM2,EPWM4 = Slave
    EPWM2.PHSEN = Enable
    EPWM2.TBPHS = 2
    EPWM2.PHSDIR = Up
    EPWM4.PHSEN = Enable
    EPWM4.TBPHS = 2
    EPWM4.PHSDIR = Up

    And this is the waveform output.

    I have few questions.

    1. PWM1 outputs the waveform immediately, while PWM2 does not.
    Why is that?
    Because it's slave?
    Is there any way to output PWM1 and PWM2 at the same time?

    2. The manual for 28004x states that the slave module is delayed, but the manual for 28002x does not.
    However, I think that the 28002x will be delayed as well.
    Is my perception correct?

    3. About TIDM-02000 Sample Software.
    EPMW3 is available for RampGenerator.
    In my opinion, EPMW3 should also operate as a slave of EPWM1.
    However, there is no SYNCI setting in the Sample.
    Why is it not necessary to synchronize?

    I would also like to correct the issue of "PWM2 always output", so please respond to that as well.

    Sorry for asking so many additional questions.

    Regards,
    Masaru.

  • 0 in reply to Masaru Maeda
    TI__Guru* 83050 points

    Masaru,

    Apologies for the delay on our side.  Chen is out of the office, but should be back and reply tomorrow the 29th US time.

    Best,

    Matthew

  • 0 in reply to Masaru Maeda
    TI__Genius 16035 points

    Hi Masaru,

    I am sorry for the late reply. 

    Masaru Maeda said:
    2. The manual for 28004x states that the slave module is delayed, but the manual for 28002x does not.
    However, I think that the 28002x will be delayed as well.
    Is my perception correct?

    Since the sync mechanism is different for f28002x, I think it is possible delay is not there. I will check and get back to you tomorrow.

    Masaru Maeda said:
    About TIDM-02000 Sample Software.
    EPMW3 is available for RampGenerator.
    In my opinion, EPMW3 should also operate as a slave of EPWM1.
    However, there is no SYNCI setting in the Sample.
    Why is it not necessary to synchronize?

    It is synchronized since phase shift is enabled.

    Regards,

    Chen 

  • 0 in reply to Masaru Maeda
    TI__Genius 16035 points

    Hi Masaru,

    I just check internally for question 2. The delay is the same for f28002x. 

    Regards,

    Chen