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Hello,
I am looking into making a BLDC controller using a C2000 microcontroller. It seems trapezoidal control it easier to use than FOC. I am reading the Application Report "Sensorless Trapezoidal Control of BLDC Motors" found here:
When it comes to the current control loop, there are two options: "The Pulse Width Modulation (PWM) Mode" and "The Hysteresis Mode". Hysteresis mode seems easier to implement. But the text does not elaborate very much. Does Hysteresis Mode work similarly to how Peak Current Control works in DC/DC converters? I.e allowing the current in the inductor reach a certain current reference level before turning the switches off?
So, when a pair of poles of the motor are ON, the current rises linearly due to the inductance in the motor. Eventually the current reaches the desired level set by the speed controller. Then the switches turn OFF for the remainder of the PWM period. I can use the DAC and Internal Comparator of the C2000 to switch off the switches quickly. Is this a correct understanding of the Hysteresis Mode?
I am incorrect I think, and I don't understand how the hysteresis is working. I found a picture of the current hysteresis, shown below. When the switches are turned off as then upper current reference is reached, where is the motor current then going? The current gets a negative slope until the lower reference is reached. But where is the current going when we have the negative slope?
Thank you for the reply. I will read through the material.
One thing I don't understand is where the current flows when the transistor is off. The transistors are off, but there is still current flowing. 
The current is decreasing. But how is the current reaching the shunt resistor? 
