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Original question:

UCD3138: UCD3138 Phase Shift Mode

UCD3138: PFM and PSM Mode

Jie Wang
Prodigy 55 points
Part Number: UCD3138
Other Parts Discussed in Thread: TIDA-00381

Dear TI term

    Hi, I am using UCD3138 for LLC converter. And I want the converter working in PFM and PSM mode.

With the help of TI, I can achieve the PFM and PSM mode. However, there are some issues when switching modes.

1. For the PSM mode, we using the Multi-mode Open Loop. The Phase Trigger is determined by Filter Duty.

        When the output voltage is LOW, the Filter Duty is HIGH, but the Phase Trigger also is HIGH，causing LOWER output voltage.

         

         For this issue, we will pair DPWM0A and DPWM1B instead of DPWM0A and DPWM1A.

         I'm not sure if there are any other ways to solve it?

2. Can the multiplication factor of the Filter YN change when the DPWM mode is switched?

I could not find this part in the AUTOMID and AUTOMAX registers.

For example, for resonant mode, OUTPUT_MULT_SEL should be set to 3 and Resonant Duty to half the period value corresponding to the lowest frequency. 

However, when switching to phase-shifting mode, the switching frequency quickly changes from the higher frequency to the lowest frequency, and then the phase-shifting operation is performed. This is wrong.

So, I would like to ask you how can smoothly switch from PFM mode to PSM mode?

  • 0
    TI__Expert 3440 points

    Hi, Jie

    Q1, I was confused your question. Can you clearly clarify how you want to configure UCD DPWM? Q2, for smooth switching of DPWM mode, the maximum frequency should be equal to mode switching threshold. It seems that your application is not based on reference design or EVM and you are developing customized application. To easing your development, it is recommended to following up the existing ready-made solution. This makes it easy for us to know what issues you are having.  If you want to create new solution, what we can help you is only answer the questions around UCD instead of system, because it is hard to re-build what system issue you are encountering.  surely, if you request customized support, you can reach out to FAE who are supporting you.  

    Thanks  

  • 0 in reply to Bliss Zhou
    Prodigy 55 points

    Hi, Bliss

    Thanks for your reply!

    Q1, I want the phase difference between DPWM0A and DPWM1A to decrease as the Filter duty increases.

    Q2, it is the TI demo code(TIDA-00381).

    Can you send me a copy of the TIDA-00381 code?

    Best regards,

    Jie

  • 0 in reply to Jie Wang
    TI__Expert 3440 points

    Jie,

    For reasons of confidentiality, I am sorry that the source code cannot be shared on E2E. please reach out to FAE to request source code.