AN1915D Freescale Semiconductor / Motorola, AN1915D Datasheet - Page 6

• Manufacturer Part Number: AN1915D
• Description: 3-Phase BLDC Motor Control with Quadrature Encoder using DSP56F80x
• Manufacturer: Freescale Semiconductor / Motorola

6
Target Motor Theory
3.1.2 Complementary Switching of Power Transistors
Note:
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, and falls to zero. With complementary switching, the opposite occurs -
transistors are switched on during freewheeling. Thus, the current is able to flow in the opposite
direction.
Both described switching modes are able to work in bipolar or unipolar mode. For detailed
information about bipolar and unipolar modes see the Application Note DSP56F80x MC
PWM Module in Motor Control Applications [2].
bipolar switching mode. The presented application utilizes the complementary unipolar PWM
mode.
Figure 3-5
Figure 3-5. Complementary Switching of Power Transistors
PWM
switching
PWM Q1
PWM Q2
PWM Q3
PWM Q4
PWM Q5
PWM Q6
PWM
switching
PWM Q1
PWM Q2
PWM Q3
PWM Q4
PWM Q5
PWM Q6
Figure 3-4. Independent Switching of Power Transistors
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
ON
OFF
ON
ON
ON
ON
ON
ON
3-Phase BLDC Motor Control with Quadrature Encoder
depicts complementary switching.
Freescale Semiconductor, Inc.
For More Information On This Product,
10º
10º
20º
20º
Go to: www.freescale.com
30º
30º
40º
40º
50º
50º
60º
60º
Figure 3-4
70º
70º
80º
80º
and
90º
90º
Figure 3-5
Electrical
angle
Electrical
angle
illustrate the
MOTOROLA