Help With BLDC Sensorless Speed Control

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Help With BLDC Sensorless Speed Control

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MoHo98
Contributor I

Hey there!

we tend to drive a specific bldc sensorless motor using two different algorithms.

both of them are based on zero crossing detection, a vey simple approach.

the algorithm one detects ZCs by analog comparators and of course their corresponsive interrupts to apply the next step of commutation.

the algorithm two detects ZCs using ADC and then comparing the BEMF to VBus/2.

here is my broblem. the max speed achieved by algo.1 differes from algo.2 while the applied duty cycle is the same(for both almost 100%)

how could it be possible? I know that the speed is related to duty cycle so I tought the max speed would be the same no matter which algo I used.

I would be grateful if you could help.

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nxp93507
NXP Employee
NXP Employee
Can you check if you have excluded hardware limitations like PWM frequency and responsiveness of the power stage? Is the power stage (FETs or IGBTs) able to react to changes in duty cycle?
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