I am using STM32F405 for BLDC six step motor control for drone application with open source BLDC VESC code. In the PWM pulses for the low side IGBT’s, there is a weird pulse (which is unwanted) and causing problem especially during high duty cycle

[JJaco.3]

The captured PWM signals with back-emf’s and currents are shown in the figure below (waveforms are recorded using Logic Analyzer). The pulse causing the problem is highlighted in yellow.

I did many work-around to solve the problem but could not find a solution. I would really appreciate if anyone can give some idea to tackle this issue.

Figure explanation:

The first three waveforms are the phase currents, followed by three back-emf’s and PWM pulses

In the figure,

'High U' is the PWM pulse on high side of U phase

'Low U' is the PWM pulse on low side of U phase

'High V' is the PWM pulse on high side of V phase

'Low V' is the PWM pulse on low side of V phase

In the test the motor is running at no-load, duty cycle is 90% and switching frequency is around 20kHz

The IGBT module used: FAM65V05DF1

The BLDC motor used: T-Motor U15

Thanks in advance

[Laurent Ca...]

Dear @JJaco.3​ 

Welcome to the STM32 Community

Could you give more details to the STM32 Community about your setup -the material you use- ?

(HW and SW, CPU(s), tools and versions, board(s), motor(s) and so on)

And more especially did you use STM32 MC tools (such as MC_suite, STM32 MC Motor Profile, STM32 MC SDK, STM32 MC Workbench, and so on)?

Best regards

Laurent Ca...