SLVSHD4 October 2024 DRV8376
ADVANCE INFORMATION
Figure 7-24 shows the operation of active demagnetization during the BLDC motor commutation. As shown in Figure 7-24 (a), the current is flowing from HA to LC in one commutation state. During the commutation changeover as shown in Figure 7-24 (b), the HB switch is turned on, whereas the commutation current (due to motor inductance) in OUTA flows through the body diode of LA. This incorporates a higher diode loss depending on the commutation current. This commutation loss is reduced by turning on the LA for the commutation time as shown in Figure 7-24 (c).
Similarly the operation of high-side FET is realized in Figure 7-24 (d), (e) and (f).
Figure 7-25 (a) shows the BLDC motor phase current waveforms for automatic synchronous rectification mode in BLDC motor operating with trapezoidal commutation. This figure shows the operation of various switches in a single commutation cycle.
Figure 7-25 (b) shows the zoomed waveform of commutation cycle with details on the ASR mode start with margin time (tmargin) and ASR mode early stop due to active demag. comparator threshold and delays.