Application Note AN-1187
Alex Lollio
The IR3230 is a three-phase brushless DC motor controller/driver with many integrated features. They provide large flexibility in adapting the IR3230 to a specific system requirement and simplify the system design.
Purpose of this document is to provide all the information for realizing a sensorless 3-phase DC motor driver using IR3230 and Microchip PIC16F1937.
To rotate the BLDC motor, the stator windings should be energized in a sequence. It is important to know the rotor position in order to understand which winding will be energized following the energizing sequence. Rotor position is sensed using Hall effect sensors embedded into the stator.
Most BLDC motors have three Hall sensors embedded into the stator on the non-driving end of the motor. Whenever the rotor magnetic poles pass near the Hall sensors, they give a high or low signal, indicating the N or S pole is passing near the sensors. Based on the combination of these three Hall sensor signals, the exact sequence of commutation can be determined. Figure shows the typical connection of the IR3230 to a 2-pole BLDC motor with Hall sensors. Based on the physical position of the Hall sensors, there are two versions of output. The Hall sensors may be at 60° or 120° phase shift to each other. This job is referred to a 60° phase shift configuration.
In more and more applications we need to drive a BLDC motor with no Hall sensor embedded into the stator. In this condition we have to find a way to generate the equivalent digital word that the Hall sensors would generate if present. When a BLDC motor rotates, each winding generates a voltage known as back Electromotive Force or back EMF, which opposes the main voltage supplied to the windings according to Lenz's Law. The polarity of this back EMF is in opposite direction of the energized voltage.
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IR3230 typical connection to a BLDC motor with Hall effect sensors embedded in the stator
