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Original question:

UCD3138: How does the phase shift information get from the filter output to the controlling the shift of the DPWMs

UCD3138: UCD3138 Phase Shift Mode

Jie Wang
Prodigy 55 points
Part Number: UCD3138

Hi

I am using UCD3138CC64EVM-030A.

I want the PWM to operate in phase shift mode. First of all, I would like to implement it by a simple experiment, but I found some problems.

1. the MASTER_SYNC_CNTL_SEL bit is set to 0, master sync controlled by Phase Trigger Register.

2. the PHASE_TRIGGER bit of DPWM1 is set to 400, DPWM0 is 0.

3. the DPWM_MODE bit is set to 2, Multi-Output Mode.

However, on the oscilloscope, DPWM0A coincides exactly with DPWM1A, with no phase difference.

So, I would like to ask if there is something wrong with my configuration?

Best Regards,

Jie

  • +1
    TI__Expert 3440 points

    Jie,

    Which channel do you want to be the master? Let me start by assuming DPWM0 is the Master here. See the following configurations.

    Dpwm1Regs.DPWMCTRL0.bit.MSYNC_SLAVE_EN = 1; //configured to slave

    Dpwm0Regs.DPWMPHASETRIG.all = ??;//  fill the data you want.

    LoopMuxRegs.DPWMMUX.bit.DPWM1_SYNC_SEL = 0; // Slave to dpwm-0

    thanks 

  • +1 in reply to Bliss Zhou
    Prodigy 55 points

    Hi Biss

    Thank you very much for your answer.

    As you described, I was able to successfully configure the phase-shifted PWM after adding these codes.

    By the way, do you know how to associate Filter Duty with Phase?

    Regards,

    Jie

  • +1 in reply to Jie Wang
    TI__Expert 3440 points

    Hi Jie,

    Dpwm0Regs.DPWMCTRL0.bit.MASTER_SYNC_CNTL_SEL = 1;//1 = Master Sync controlled by CLA value

    thanks 

  • 0 in reply to Bliss Zhou
    Prodigy 55 points

    Hi Biss,

    Thank you very much for your reply.

    Can you help me solve one more small question? 

    Dpwm0Regs.DPWMCTRL0.bit.MASTER_SYNC_CNTL_SEL = 1;//1 = Master Sync controlled by CLA value

    However, for multi output mode, Filter Duty also determines the falling edge of DPWMAB.

    So how can I ensure that the duty of DPWMAB is 0.5 during phase shifting

    Best Regards,

    Jie

  • 0 in reply to Jie Wang
    TI__Prodigy 480 points

    Hi Jie,

    A little confused about "So how can I ensure that the duty of DPWMAB is 0.5 during phase shifting", could you provide more details?

    Regards,

    Peter

  • 0 in reply to Jie Wang
    TI__Prodigy 480 points

    Hi Jie,

    Do you want DPWM1A to be slaved to DPWM0A and the phase shift controlled by the CLA value of DPWM0?

    Or do you want DPWM0B to be slaved to DPWM0A and the phase shift controlled by the CLA value of DPWM0?

    This is a different implementation. Could you draw the timing you need for better understanding?

    Regards,

    Peter

  • 0 in reply to Peter Ban
    Prodigy 55 points

    Hi Peter

    Thank you very much for your reply!

    When I set the phase shift to be determined by the Filter duty, I find that not only does the PWM phase change, but their duty changes as well.

    I want DPWM1A to be slaved to DPWM0A and the phase shift controlled by the CLA value of DPWM0.

    And the duty cycle should always be 0.5 for PSFB.

    like this:

    Best Regards,

    Jie

  • +1 in reply to Jie Wang
    TI__Prodigy 480 points

    Hi Jie,

    You can reference the configuration of "Muti-Mode Open Loop" in manual. In this mode the edge of DPWM is determined by the event register.

    Below configuration for your reference.

    //Disable the CLA

    Dpwm0Regs.DPWMCTRL0.bit.CLA_EN = 0;

    Dpwm1Regs.DPWMCTRL0.bit.CLA_EN = 0;

    //Mater slave 

    Dpwm0Regs.DPWMCTRL0.bit.MSYNC_SLAVE_EN = 0;// Master

    Dpwm1Regs.DPWMCTRL0.bit.MASTER_SYNC_CNTL_SEL = 1; //Slave

    LoopMuxRegs.DPWMMUX.bit.DPWM1_SYNC_SEL = 0; //0 = DPWM 0 Sync (Default)

    //Phase shift is triggered by CLA

    Dpwm0Regs.DPWMCTRL0.bit.MASTER_SYNC_CNTL_SEL = 1;//1 = Master Sync controlled by CLA value

    //DPWM0 timing

    Dpwm0Regs.DPWMEV1.bit.EVENT1 = 0;

    Dpwm0Regs.DPWMEV2.bit.EVENT2 =  period * 0.5;

    Dpwm0Regs.DPWMPRD.bit.PRD = period;

    //DPWM1 timing

    Dpwm1Regs.DPWMEV1.bit.EVENT1 = 0;

    Dpwm1Regs.DPWMEV2.bit.EVENT2 =  period * 0.5;

    Dpwm1Regs.DPWMPRD.bit.PRD = period;

  • 0 in reply to Peter Ban
    Prodigy 55 points

    Hi Peter,

    Thank you very much for your reply and the detailed configuration instructions.

    I successfully got the phase shift PWM implemented.

    Best Regards,

    Jie

  • +1 in reply to Jie Wang
    TI__Prodigy 480 points

    Hi Jie,

    You are welcome.

    Regards,

    Peter