Complementary Switching Of Power Transistors - Motorola M68HC08 Manual

BLDC Motor Theory

3.3 Complementary Switching of Power Transistors

Designer Reference Manual
20
Freescale Semiconductor, Inc.
PWM
switching
ON
PWM Q1
OFF
ON
PWM Q2
OFF
ON
PWM Q3
OFF
ON
PWM Q4
OFF
ON
PWM Q5
OFF
ON
PWM Q6
OFF
10º
Figure 3-4. Independent Switching of Power Transistors
With complementary switching, two transistors are switched on when the
phase of the BLDC motor is connected to the power supply. But there is
a difference during freewheeling. With independent switching, all the
transistors are switched off. The current continues to flow in the same
direction through freewheeling diodes until it falls to zero. Contrary to
this, with complementary switching, the complementary transistors are
switched on during freewheeling. Thus the current may be able to flow
in the opposite direction. Figure 3-5. Complementary Switching of
Power Transistors depicts the complementary switching.
BLDC Motor Theory
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Electrical
angle
DRM046 — Rev 0
MOTOROLA