DRV10964 Datasheet, PDF (12/27 Pages) Texas Instruments – Three-Phase Sinusoidal Sensorless BLDC Motor Driver

DRV10964
SLDS227 – MARCH 2016
4 x Kt
Ktc
Kt
0.5 x Kt
www.ti.com
Lock detect
Figure 10. Abnormal Kt Lock Detect
7.3.5.3.1 Lock 3: Accelerate Abnormal
This lock condition is active when the DRV10964 device is operating in the closed loop mode. When the closed
loop commutation rate becomes lower than 1/2 of the previous commutation period then this is an indication that
the motor is not moving. Under this condition the accelerate abnormal condition will be triggered.
7.3.5.4 Lock4: Speed Abnormal
If the motor is in normal operation the motor BEMF will always be less than the voltage applied to the phase. The
DRV10964 sensorless control algorithm is continuously updating the value of the motor BEMF based on the
speed of the motor and the motor Kt as shown in Figure 11. If the calculated value for motor BEMF is higher than
the applied voltage (U) for a certain period of time (t_{ON_LOCK}) then there is an error in the system. The calculated
value for motor BEMF is wrong or the motor is out of phase with the commutation logic. When this condition is
detected a lock detect is triggered.
Rm
U
M BEMF = kt * speed
If speed > U / kt
Lock is triggered.
Figure 11. BEMF Monitoring
7.3.6 Short Circuit Current Protection
The short circuit current protection function shuts off drive to the motor by placing the motor phases into a high
impedance state if the current in any motor phase exceeds the short circuit protection limit I_SHT. The DRV10964
device will go through the initialization sequence and will attempt to restart the motor after the short circuit
condition is removed. This function is intended to protect the device and the motor from catastrophic failure when
subjected to a short circuit condition.
7.3.7 Anti-Voltage Surge (AVS)
Under normal operation the DRV10964 acts to transfer energy from the power supply to the motor to generate
torque, which results in angular rotation of the motor. Under certain conditions, however, energy which is stored
in the motor in the form of inductive energy or angular momentum (mechanical energy) can be returned to the
power supply. This can happen whenever the output voltage is quickly interrupted or whenever the voltage
applied to the motor becomes less than the BEMF voltage generated by the motor. The energy which is returned
to the supply can cause the supply voltage to increase. This condition is referred to as voltage surge.
12
Submit Documentation Feedback
Product Folder Links: DRV10964
Copyright © 2016, Texas Instruments Incorporated