Buck Converter Bootstrap problem

Discussion in 'Power Electronics' started by xxnatjadexx, Jul 10, 2016.

  1. xxnatjadexx

    Thread Starter New Member

    Jul 10, 2016

    i need help with my circuit as it is not working as should.

    using the application notes(AN486) from silicon labs i have calculated the required bootstrap capacitor which is anything above 151nF .

    the problem is that when simulating this circuit in multi sims 14 ...the high output of the IR2011PBF stops pulsing the mosfet after 400uS...then the output voltage of the buck decreases til it gets to 6v then starts pulsing again. i have check varies points on the circuit and made sure undervoltage lock out is not activated on any of the pins according to the data sheet. and i have no control loop on this circuit so dont know why it is doing that

    i am totally lost as what is wrong ....

    input voltage 40V
    Freqency is 200Khz
    Duty Cycle is 0.225
    output voltage should be 9V

    upload_2016-7-10_18-7-3.png IMG_1142.JPG

    Last edited: Jul 10, 2016