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  1. Electric1

    Opamp circuit clarification

    I am trying to solve not really homework problem. I do not know how to add bias current and analyze the circuit, I have re written the equations last time i have done mistakes, these are the new equations and get entirely new equation and it is not correct as well since when V1 = 0V; V+ =...
  2. Electric1

    Opamp circuit clarification

    I applied the Kirchoff's rules to the below circuit and derived the below equation of the voltage at the noninverting input V+ = (1.65V - V/1323).
  3. Electric1

    Opamp circuit clarification

    My actual circuit is as below i am sorry that i am going in steps to understand what the circuit does in one go it is quite challenging to analyze The voltage at noninverting input is 3.3V/2 = 1.65V and it is amplified by the factor of 1.65V*(1 + 2.5kOhm/660kOhm) = 1.65V I get around 1.66V...
  4. Electric1

    Opamp circuit clarification

    Ok now i understand if i take a higher input voltage of 10V the output value is now 10.04V
  5. Electric1

    Opamp circuit clarification

    I am trying to analyze the below Opamp circuit I have picked a random opamp in Ltspice. I can understand that it is non inverting amplifier and gain is Vout = V1(1 + (R1 || R3) / R2) Vout = 2mV * (1 + 2.5KOhm/660KOhm) = 2mV but i get result of 9mV, why? If i simulate without R4 i get the...
  6. Electric1

    Calculation of Gate Resistance

    I have done several changes and tested it 1. Changed the gate resistance from 22 Ohm to 10 Ohm, the observation is the ringing was observed on the Mosfet and on the Gate driver output. Initially with 22 Ohm the ringing was not present on the Mosfet. 2. Changed the boot strap capacitor with...
  7. Electric1

    Calculation of Gate Resistance

    Initially the boot strap capacitance value was 1uF, then i changed it to 4.7uF and observed an improvement in speed of 200 RPM, i tried increasing to 10uF but motor was not rotating. Now i want to check for around 6.8uF but it is not available, it is 0603 package and there no pcb slot to solder...
  8. Electric1

    Calculation of Gate Resistance

    It is there the V signal from the VS is going to the V signal in the MOSFET diagram( I have shown U phase MOSFET) 3 MOSFET drivers U,V, W signals from VS pin going to U,V,W points of the MOSFET.
  9. Electric1

    Calculation of Gate Resistance

    Phase current waveforms i have captured from standard controller and mine. The DC bus current and phase currents are high for the standard controller and hence speed i suppose. 100mv - 10A I get around 50mV - 5A DC bus current is 2.7A Standard controller - It goes upto 15A, DC Bus current is...
  10. Electric1

    Calculation of Gate Resistance

    It is 3 phase current sensing and hall sensor based.(It is off road farming vehicle and runs at slow speed not very safety critical application).
  11. Electric1

    Calculation of Gate Resistance

    Thank you for the guidance, I have not tried both of them. I am driving the Gate driver with 12V which is converted from the battery 48V. It is not laboratory experiment it is used for driving the hydraulic fluid for steering control and the requirement is motor should run at 3000 RPM, i have...
  12. Electric1

    Calculation of Gate Resistance

    As a first step i reduced the gate resistance to 10 Ohm in place of 22 Ohm but no difference in speed is observed. I do not think further decrease in resistance will have impact on speed. I am not sure what else i can do to increase the speed, i am assuming FOC SVPWM gives the maximum speed, is...
  13. Electric1

    Calculation of Gate Resistance

    Yes i have taken the waveforms positive on the Mosfet Gate and negative on the source. One waveform i have taken with negative on battery ground. The number in the front indicates the modulation index. The waveforms are ok now. But 2 issues i have right now a. when i set the modulation index to...
  14. Electric1

    Calculation of Gate Resistance

    Ok I will do it and share the waveforms.
  15. Electric1

    Calculation of Gate Resistance

    Sorry i did not explain the testing The probe is differential probe positive on the gate output, pin no 4 and negative on the battery ground instead of the source. The probe is in *20 mode hence 0.6V will be 0.6*20 = 12V. Pin 5 i gave 12V supply. Diffprobe I will share the schematics shortly.
  16. Electric1

    Calculation of Gate Resistance

    Yes exactly i am facing the ringing issue at Gate to Source Low side after the Mosfet driver, i have not verified at high side. At some levels of modulation index of 85% the ringing is very high and over voltage fault is created. That is the reason i went for the exact calculation of external...
  17. Electric1

    Calculation of Gate Resistance

    I am sorry i could not understand completely what you are trying to say, whatever little i can understand is that we cannot completely rely on the calculations, based on testing we have to decide the value, am i correct?
  18. Electric1

    Calculation of Gate Resistance

    Please help to review and confirm the calculations for the total gate resistance the Mosfet data sheet i have attached, the gate resistance calculations are performed as per the article GateResistance tsw = 100ns, the way i arrived at 100ns is the switching frequency is 15KHz , time for one...
  19. Electric1

    Calculation of Gate Resistance

    Ok, now i get it thank you, Internal source resistance Calculation Rs1 Ohm = VCC/IOpk+ = 15 Volts / 2.5 A = 6 Ohm Rs2 Ohm = Voh / Itest = 0.05 Volts / 0.02 A = 2.5 Ohm Average = (Rs1 + Rs2) / 2 = (6 Ohm + 2.5 Ohm)/2 = 4.25 Ohm So, the internal source resistance is 4.25Ohm Internal Sink...
  20. Electric1

    Calculation of Gate Resistance

    Thank you for reply, but one challenge i am facing is for the Mosfet driver attached i am unable to find the table similar to below which is used in the calculation Can you please guide how do i calculate for the driver i have attached. There is an article from Infineon but could not follow...
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