+ Post New Thread
Results 1 to 6 of 6
  1. #1
    Newbie level 3
    Points: 32, Level: 1

    Join Date
    Mar 2020
    Posts
    3
    Helped
    0 / 0
    Points
    32
    Level
    1

    Bootstrapping with Opto Driver

    Hi team!

    There is a bootstrap gate drive circuit for a inverter that I take the project of a graduate student as a reference and it works. But there are a few things that I don't understand in this circuit.

    Like ;

    -Why does the PWM signal come from the cathode to the anode?
    -Why is a capacitor placed between the cathode and the anode?
    -Why 12V is given externally to the anode? or
    ( Doesn't the opto coupler work without biasing the Anode? )

    Click image for larger version. 

Name:	Bootstrapping Circuit Ex..JPG 
Views:	8 
Size:	42.0 KB 
ID:	158514

    •   AltAdvertisement

        
       

  2. #2
    Super Moderator
    Points: 83,859, Level: 70
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    17,050
    Helped
    3853 / 3853
    Points
    83,859
    Level
    70

    Re: Bootstrapping with Opto Driver

    Hi,

    this is an inclomplete circuit. I donīt think it is correct. It does not make sens to discuss abut an incomplete circuit.

    Where is it from? --> give a link ..
    and give full description.

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.


    1 members found this post helpful.

    •   AltAdvertisement

        
       

  3. #3
    Newbie level 3
    Points: 32, Level: 1

    Join Date
    Mar 2020
    Posts
    3
    Helped
    0 / 0
    Points
    32
    Level
    1

    Re: Bootstrapping with Opto Driver

    Hi sır ,

    The Opto Driver IC is the HCPL-3120 above ,

    Also i will send another picture below wich includes 2 pre-bias supplies like the picture above.
    He got the same things , only the difference is that they give 5V instead of 12V.
    the driver section is taken by EG8010+TLP250.
    Click image for larger version. 

Name:	TLP250.JPG 
Views:	13 
Size:	61.0 KB 
ID:	158515

    The link the link :)
    https://www.lz2gl.com/data/power-inv...tasheet_en.pdf



    •   AltAdvertisement

        
       

  4. #4
    Super Moderator
    Points: 83,859, Level: 70
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    17,050
    Helped
    3853 / 3853
    Points
    83,859
    Level
    70

    Re: Bootstrapping with Opto Driver

    Hi,

    This circuit makes more sense:

    It differs to the first one:
    * Now there is no capacitor beween A nd C of the LED. It is between pin2 and GND. Mind the junction dot.
    * It seems to be a low side driver and a high side driver
    * low side driver pin5 is connected to GND
    * high side driver pin5 is connected to the half bridge
    * LED power supply now is 5V.
    * maybe others...

    Now to your questions.
    -Why does the PWM signal come from the cathode to the anode?
    what does this mean?

    -Why is a capacitor placed between the cathode and the anode?
    No. The capacitor is NOT connected between C and A.

    -Why 12V is given externally to the anode?
    What is the alternatice you see? Why do you ask?

    or( Doesn't the opto coupler work without biasing the Anode? )
    the input of the optocoupler is a LED. It needs current to flow, it needs some power.
    It is very basic knowledge that any LED will need both pins connected to be able to work.

    ... or did I misunderstand the question?

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



  5. #5
    Newbie level 3
    Points: 32, Level: 1

    Join Date
    Mar 2020
    Posts
    3
    Helped
    0 / 0
    Points
    32
    Level
    1

    Re: Bootstrapping with Opto Driver

    First of all, thank you very much for answering very quickly sir!

    What is the alternatice you see? Why do you ask?
    I want to explain the reason by giving an example ,
    when the PWM signals are applied, a voltage of 12V comes already to the anode of the IC.
    In addition, I could not understand why it was directly powered by 12V with a pre-biased supply.

    I mean , can't i just feed the opto - driver with the amplitude of the pwm signal?

    Thanks in advance.



    •   AltAdvertisement

        
       

  6. #6
    Super Moderator
    Points: 83,859, Level: 70
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    17,050
    Helped
    3853 / 3853
    Points
    83,859
    Level
    70

    Re: Bootstrapping with Opto Driver

    Hi,

    I want to explain the reason by giving an example ,
    when the PWM signals are applied, a voltage of 12V comes already to the anode of the IC.
    In addition, I could not understand why it was directly powered by 12V with a pre-biased supply.

    I mean , can't i just feed the opto - driver with the amplitude of the pwm signal?
    This all makes no sense to me.

    --> Show a sketch/circuit about your idea.

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



--[[ ]]--