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UCD3138: UCD3138 unable to enter the Single Frame state, and stay in the IDLE state

Part Number: UCD3138

Hello.
I have recently debuging your UCD3138 full bridge hard switch circuit development board.
I have encountered a question .
The development board has a secondary short circuit during circuit debuging. Resulting in the primary MOS tube and secondary synchronous rectifier and the primary MOS transistor driver UCD27211 burned out.I replaced the MOS tubes and drive UCD27211, auxiliary power can work properly. But UCD3138stay in the IDLE state, did not enter the Single Frame state, the system can not start, UCD3138 did not issue PWM, power input current is only 19mA.

I guess should be my hardware part of the problem, leading to UCD3138 stay in IDLE state. But I checked the auxiliary current, the driver, the isolator, the MOS tube, the input voltage sampling circuit, these are all good. I am now very puzzled.
Excuse me, can i get the inspiration from the program? Can be seen from the program may be what causes UCD3138 unable to enter the Single Frame state, and stay in the IDLE state?
Thank you!

  • Hi,

    Sorry for the delay in replying to your post. I have asked the UCD team to respond to your post. You should see a response soon.

    Regards

    Peter
  • There may be more voltage drop after the circuit is repaired. Trying few things:

    1). Scope the DPWM0A and DPWM1A, and see if you can see any short pulse;

    2). Increase input voltage  to 50V;

    3). Apply 1A load.

    Please let me know if it helps,

    Sean

  • 您好。
    我按照您指点的方法,给输入电源设到50V,并带了1A负载。
    检测DPWM0A,可以看到single frame 模式下发出的800ns短脉冲。
    然而模块一起没有启动,输入电流只有19mA,短脉冲持续的发出,UCD3138停留在IDLE状态。
    是输入电压采样出错了吗?使3138一直处于欠压保护状态?
  • DPWM0不断发出短脉冲,但VIN_CT脚的电压只有0.15V,估计UCD3138一直处于欠压状态,所以起不来。
    但为什么采样电路只有0.15V呢?如果正常的话,在50V输入情况下,应该能达到0.7V。
  • 我发现了一个现象,只有DPWM0A和DPWM0B有短脉冲,DPWM1A和DPWM1B没有发出脉冲,这不正常,不过我知道哪里出现了问题导致这一现象。
  • 不好意思,我弄错了,DPWM1A和DPWM1B也都发出脉冲了。不过VIN_CT只有0.15V。
  • Hello. Have you used the memory debugger to look at the state variable to see what state the HSFB code is in?

    I've been looking in the code.  If you have the ENABLE switch (S1) on, it looks like the idle state will run the single frame 2 times per second.  So if you see 2 pulses per second on the DPWM pins, that means that it is probably staying in the idle state. 

    If you're seeing pulses at the switching frequency, it's obviously in some sort of power up state. 

    It may also be going back and forth between idle and ramp up.

    For it to start ramp up, there are two requirements.

    1. Enable pin high

    2. EAP2 pin goes to or above .345 volts when sampled during single frame. 

    I hope this will help you with your debugging 

  • thank you very much!
    I checked the memory debugger, HSFB code in the IDLE state.
    I observed the DPWM, issued two pulses per second, should be in the IDLE state.
    The enable pin is set high, but the voltage on the EAP2 pin is only 0.15V and does not reach 0.345V.
    I think it might be a problem with the input voltage sampling circuit.
    But I checked the circuit, the components are not damaged.
  • Hello. I recently debug 3138 of the full bridge development board encountered a problem.

    The development board before burning once, I replaced the bad mos,
    the board is not up after the power, has been in the simgle frame state,
    the input voltage detection value regardless of the input voltage,
    from 40V to 60V, are 0.2V, Has been lower than the undervoltage protection threshold.
    Under normal circumstances, the input value of 40V, the detection value of 0.7V, the board will start.
    I checked the input voltage sampling circuit, the primary digital isolator, the driver and the primary MOS tube are all good.
    I am wondering why the input voltage from the secondary tap of the transformer is low and does not change.
    I used the procedure to TI to the code, the problem should still be on the hardware, but I now do not know where mistakes.
  • Hello there.
    "Using the UCD3138HSFBEVM-029 User's Guide" on page 30
    Say "the sensing approach described in Section 12.3.3 is good to use in steady-state but not capable of fast transient sensing."
    And "More details on how the maintransformer is used to make input voltage sense can be found in Section 12.5. "
    Which manuals are "Section 12.3.3" and "Section 12.5"? I did not find the "Using the UCD3138HSFBEVM-029 User's Guide".
  • Hello there.
    "Using the UCD3138HSFBEVM-029 User's Guide" on page 30
    Say "the sensing approach described in Section 12.3.3 is good to use in steady-state but not capable of fast transient sensing."
    And "More details on how the maintransformer is used to make input voltage sense can be found in Section 12.5. "

    Which manuals are "Section 12.3.3" and "Section 12.5" in?
    I did not find it in the "Using the UCD3138HSFBEVM-029 User's Guide".
  • Hello.
    The problem is solved.
    The input port's fuse is broken. Resulting in low input voltage.
    thank you for your help!