Is possible to drive B-G431B-ESC1 using 6-step control.

Kenji1 · ‎2022-09-28

Hi Team

I want to drive BLDC motor based 6-step control (Trapezoidal control), using B-G431B-ESC1.

But it seems that the board is design for FOC control.

Is it possible to drive with 6-step?

Gigi · ‎2022-10-03

Ciao
It is possible to sample the BEMF in two points, one is in the middle of the PWM off time and in this case the zero-crossing threshold is zero (the GND of the inverter). In this way there is no need of having a voltage divider on the BEMF network.
The second point is the middle of the PWM on time. In this case is necessary to enable the voltage divider to bring the neutral point in a range compatible with the ADC input.
The BEMF_GPIO pin can be used for this purpose, to enable or disable the BEMF voltage divider in run time (according to the sampling point of the BEMF).
If the BEMF_GPIO pin is set in output, push pull, with low value, it enables the divider, if it is set as high impedance (for instance in input) it disables the voltage divider.
I’m not aware about any recent documentation on this technique.
Ciao
Gigi
ST Restricted

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Cristiana SCARAMEL · ‎2022-09-29

Hello @Kenji

as reported in the board user manual UM2516: The Discovery kit is also compatible with the 6-step control with embedded BEMF hardware circuit for rotor position estimation.

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Kenji1 · ‎2022-09-29

Hi @Cristiana SCARAMEL

I want to do, sensorless trapezoidal (6step) control of BLDC motor.

Just looking at the schematic, I think it's possible by using Hall sensor.

However, I want to control with sensorless.

Is possible to drive with sensorless?

If possible, how does this circuit perform BEMF zero-crossing detection?

Gigi · ‎2022-09-30

The board shall be ready for a SixStep sensorles control using the this BEMF zero crossing detection network. Detection is done using the ADC of the micro.

Ciao

Gigi

Kenji1 · ‎2022-10-03

Hi @Community member

Actually, how does this circuit works for BEMF zero crossing detection?

It will do ADC and calculate virtual neutral point for detect zero cross detection?

How is the BEMF_GPIO pin used, is there any documents that describe it?

Gigi · ‎2022-10-03

Ciao
It is possible to sample the BEMF in two points, one is in the middle of the PWM off time and in this case the zero-crossing threshold is zero (the GND of the inverter). In this way there is no need of having a voltage divider on the BEMF network.
The second point is the middle of the PWM on time. In this case is necessary to enable the voltage divider to bring the neutral point in a range compatible with the ADC input.
The BEMF_GPIO pin can be used for this purpose, to enable or disable the BEMF voltage divider in run time (according to the sampling point of the BEMF).
If the BEMF_GPIO pin is set in output, push pull, with low value, it enables the divider, if it is set as high impedance (for instance in input) it disables the voltage divider.
I’m not aware about any recent documentation on this technique.
Ciao
Gigi
ST Restricted

Kenji1 · ‎2022-10-03

Hi @Community member

Thank you.