BLDC motor is traditionally defined as a permanent magnet synchronous motor with trapezoidal back-EMF waveform shape.
Because electrical excitation must be synchronized with the rotor position, BLDC motors usually require one or more rotor position sensors when running. For reasons of cost and reliability, the motor is suitable for operation without a position sensor, which is commonly referred to as sensorless operation. By detecting the BEMF voltage on the non-energized phase winding, the commutation time of the motor drive voltage can be determined.
Advantages of the sensorless algorithm:
1. Save device cost and installation cost.
2. To improve stability, the position sensor chip is easily damaged under high temperature and high humidity commutation. Therefore, Jianke Electronics launched the sensorless control technology, which solves the above problems well.
Zero crossing detection method. The BEMF voltage is compared with half of the DC bus voltage. This method is to use a comparator to compare the BEMF voltage with half of the DC bus voltage (VBUS/2) assuming that a zero-crossing event occurs when the BEMF voltage is equal to VDC/2. )Compare. The figure below shows the circuit used to implement this method.
Advantages: small amount of calculation, can achieve high speed
Disadvantages: not flexible enough.
Voltage comparison method. It can be simplified by using a variable threshold voltage point to detect zero crossing events. This variable voltage is the neutral point of the motor. The neutral point of most BLDC motors will not be led out with wires. But the neutral point can be constructed with a resistance network. Connect one end of the three resistors in parallel with the three-phase winding of the motor, and connect the other end together to create a virtual neutral point, as shown in the figure below.
Advantages: The algorithm is flexible and changeable, and can be quickly started.
Disadvantages: large amount of calculation and complicated algorithm.
1. Wider speed adjustment range.
In the traditional control algorithm, only one upper bridge and one lower bridge are connected at a time. Jianke Electronics has optimized the algorithm. On the basis of two or two connections, three or three connections are added to increase the conduction angle. Increase the speed.
2. Faster startup performance.
The fast start algorithm of Jianke Electronics has been applied to the fuel pump, which can ensure that it starts to the highest speed within 150ms.
Angle, thereby increasing the speed.
3. High robustness
Jianke Electronics uses the MCU comparator to detect the BEMF of the motor, while reducing costs, it can implement more complex software algorithms, thereby improving robustness.
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Email: sales@jkaec.com
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