Motorola M68HC08 manual Balanced Capacity Coupling Back-EMF Sensing Circuit

Freescale Semiconductor, Inc.

BLDC Motor Control

Freescale Semiconductor, Inc.

Figure 3-11. Balanced Capacity Coupling

NOTE: The configuration of the phase windings end-turns has significant impact; therefore, it needs to be properly managed to preserve the balance in the mutual capacity. This is important, especially for prototype motors that are usually hand-wound.

CAUTION: Failing to maintain balance in the mutual capacitance can easily disqualify such a motor from using sensorless techniques based on the back-EMF sensing. Usually, the BLDC motors with windings wound on separate poles show minor presence of the mutual capacitance. Thus, the disturbance is also insignificant.

3.2.5 Back-EMF Sensing Circuit

An example of the possible implementation of the back-EMF sensing circuit is shown in Figure 3-12.

Designer Reference Manual		DRM028 — Rev 0
36	BLDC Motor Control	MOTOROLA
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