• State Resolved
  • Locked Locked
  • Replies 11 replies
  • Subscribers 29 subscribers
  • Views 1015 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8301 cannot achieve 100% dutycycle

haotian cui
Prodigy 165 points
Other Parts Discussed in Thread: BOOSTXL-DRV8301, DRV8301

I just purchased a BOOSTXL-DRV8301 kit and tested it. I programed the launchpad to generate 3 complementary PWM signals to the DRV8301, but when the high side gate signal near 100% duty, the output gate driver signal cannot hold on and drop down. The datasheet shows this chip have the ability to achieve 100% dutycycle, what is the problem? Thank you.

There are some test signal below(yellow one is the highside gate drive signal,and the green one is the low side signal)

 

                                                          (1)

                                                              (2)

                                                          (3)

  • 0
    TI__Mastermind 26065 points

    Hi Haotian

    Let's have a check and get back to you later.

    What is the PWM and it's external deadtime you programmed? Also the PWM frequency?

    Thanks.

  • 0 in reply to Wilson Zuo
    TI__Mastermind 26065 points

    Hi Haotian

    After a simple checking, I see no issue of DRV8301 to output 100% duty on High side. Please refer to my test procedure.

    24V VM;

    DRV8301 default register setting;

    En_GATE = 1;

    INL_C = 0;

    INH_C = toggled H/L or constant H

    GH_C output can follow INH_C and maintained exactly as below. Blue: INH_C, Green: GH_C.

    (Note the duration of the HIGH level is hundreds ms)

     

    I think you many have some problem with your inputs signals into DRV8301.

    Thanks.

  • 0 in reply to Wilson Zuo
    Prodigy 165 points

    Hi,Wilson,

    I have a lot of tests with DRV8301 and no tests can achieve your result, the result on your oscilloscope is perfect!

    I just finished a new test and this problem is still the same, the condition is below:

    Bus voltage = 24V;

    DRV8301 default register setting;

    En_GATE = 1;

    INL_C  and INH_C are 18.8KHz complementary PWM signal, deadtime is about 2us.

    No problem with the input signals.

    And if I just put the INL_C  to zero, the INH_C=PWM the output will have no signal show.

    I want to know if you connected the driver signal between DRV8301 and the half bridge MOSFETs? If you have connected, I think the GH_C should be about 24v+12v=36v, because the high side MOSFET turned on and the SH_C=24V. 

    Thanks

     

  • 0 in reply to haotian cui
    Prodigy 165 points

    There is another test video clip here(the blue one is the input signal and the yellow is the output signal): 

    http://v.youku.com/v_show/id_XNzEyMzgwNTM2.html

    http://v.youku.com/v_show/id_XNzEyMzc3NDg4.html

  • 0 in reply to haotian cui
    Prodigy 165 points

    Last night, I did a test just like what you did, and it is really works! The high side has no problem to maintain high level.

    So, I guess it didn't work in early tests because I give the same signal to all three phase. If I just give 100% duty to one or two phases is fine, but when I give three 100% duty signals to all phase, the problem appears.

    I'll do some other tests to confirm my opinion.

  • 0 in reply to haotian cui
    TI__Mastermind 26065 points

    Hi Haotian

    I also don't see any issue to put six H/L or PWMs in to all the inputs.

    Note that DRV8301 will automatically insert the dead time if you put a overlaped HIGH into to both INH and INL of the same half bridge. 

    Also please note the there is a register can change the input mode between six PWM inputs or three PWM inputs.

    Thanks.

  • 0 in reply to Wilson Zuo
    TI__Mastermind 26065 points

    Hi Haotian

    BTW, althrough you didn't say anything about your videos uploaded to "Youku". I think there is still the possibilties to cause missunderstanding to other people or engineers. So I think it will be better to remove the videos or give a clear comments that it is fine with 100% duty and cool after your problem solved :)

    Thanks

  • 0 in reply to Wilson Zuo
    Prodigy 165 points

    Hi Wilson,

    I have been removed those videos. And I will do more tests to confirm that issue.

    Thanks for your help.

  • 0 in reply to Wilson Zuo
    Prodigy 165 points

    Hi, Wilson

    I think I know what causes the failure to hold high side to high. The deadtime is the reason, too large deadtime will cause this problem. Can you help me to have a test? The problem deadtime is about 2us. When I use 200ns high side is OK.

    Thanks

  • 0 in reply to haotian cui
    TI__Mastermind 26065 points

    Hi Haotian

    Thanks for your feedback. The question is DRV8301 only can support MAX 500nS deadtime with 150k Rdtc. So I'm not sure about your 2us dead time. Did you use a resister > 150k or you mean just the external deadtime by MCU. If it is the external deadtime, what is your internal deadtime setting?

    Thanks.

  • 0 in reply to Wilson Zuo
    Prodigy 165 points

     Hi, Wilson

    I use a 1R resister at DTC and a 2us external deadtime by MCU. 

    Thanks