![]() ![]() ![]() Compared to a typical SMPS or a similar driver that employed PWM via the individual driver channels this is a very long 'on time' and will require considerably more capacitance than switching 30khz or more.at least I THINK it will.hence my reasoning for having 100uF.Regardless of my reasoning, I haven't found anything to suggest that the extra capacitance will be problematic The reason for adding it was to address. All of these formulas are based on knowing the switching characteristics in advance.which is intuitive if you are designing an SMPS or a driver for a particular motor.In my case I want to experiment with different BLDC motors in a fairly wide frequency range.so if I am driving a 3-phase motor 30hz, and not employing PWM via the driver, then each switch will have have an 'on-time' of 5.5ms, the 'on time' would be 550uS. Arouse/Kris.Thank you for the Fairchild's Application Note AN-6076 ( ) and several other application notes I have read there are formulas to use to correctly select the value of the bootstrap capacitor 'Cboot', but in all cases the values I see applied in real-world circuits are typically at least an order of magnitude larger than the formulas in the application notes would suggest. You probably already knew that I just feel obliged to point it out for thoroughness. If you try to do that, the high-side charge capacitors (C1 and C2) will eventually discharge and the top MOSFET will turn OFF. ![]()
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December 2022
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