Key points that BLDC is prone to making mistakes and neglecting

    Motor forward and reverse rotation

    For three Hall elements placed 120 ° apart: (here should be only one pole pair)     Corresponding forward and reverse rotation:

    What is the order of 546231?

    This is not a sector!!!!

    Actually, in the end, we all need to control the motor through software.

    Three Halls make up a 3-bit wide binary number: 101, 001, 011

    So we made the following assumptions: the U-value of the Hall sensor is the high bit 2, the V-value is bit 1, and the W-value is bit 0

    We can calculate a Hall value accordingly:

    And 546231 is the corresponding Hall value during normal transmission.

    What should be noted when implementing Hall value software?

    Hall is just three high and low level signals, the key is when to read this value.

    Suggest placing it in the interrupt, don‘t ask why, it‘s about real-time performance, especially when the speed is too high. You don‘t have time to process the data, which leads to untimely commutation and inability to increase the speed!!!

    HallDate=0;

    HallDate=U<<2 | V<<1 | W<<0;

    And operations that can be completed using shifts, do not use addition, subtraction, multiplication, and division. Bitwise operations are the fastest in C.

    At this point, the HallDate you read is a number from 0 to 7, why are there still 0 and 7?

    0 means the Hall value was not read, and 7 means the Hall value has been interfered with. Anyway, there is a problem, check it quickly!

    What is the half bridge of a three-phase inverter circuit

    Attention: Half bridge does not refer to the three power transistors above, but to the three half bridges of UVW, U+U - which can be considered as one half bridge.     Common PWM regulation methods

    When we look at other people‘s code, we often see things like H-ON-L_PWM, H-PWM-L-ON

    What is this?

    In fact, it is the PWM adjustment method. It is not mentioned above that better control of the motor is necessary, and PWM is introduced, but there are also many ways of PWM adjustment.

    In theory, there should be 5 types, but let‘s only talk about the most common three

    HYON-L-PWM: The upper half bridge of one phase always maintains a high level (i.e. the upper half bridge is normally open and conducting), while the lower half bridge of the other phase is always controlled in PWM mode

    H-PWM-L-ON: The upper half bridge of one phase is always controlled in PWM mode, while the lower half bridge of the other phase remains at a high level (i.e., the lower half bridge is normally open and conducting)     H-PWM-L-PWM: Both the upper and lower half bridges are controlled in PWM mode, and this control must have a dead zone, otherwise it may cause a short circuit at the moment of commutation.

    Pay attention to keeping the frequency of PWM around 20K as much as possible, firstly due to power transistor limitations, and secondly to avoid interference from high-order harmonics.