tmp88fw45afg TOSHIBA Semiconductor CORPORATION, tmp88fw45afg Datasheet - Page 150

• Manufacturer Part Number: tmp88fw45afg
• Description: 8 Bit Microcontroller Tlcs-870/x Series
• Manufacturer: TOSHIBA Semiconductor CORPORATION

14.1
Outline of Motor Control
14.1
motor, the rotor windings to which to apply electric current are determined from the rotor’s magnetic pole position,
and the current-applied windings are changed as the rotor turns. The rotor’s magnetic pole position is determined using
a sensor such as a hall IC or by detecting polarity change (zero-cross) points of the induced voltage that develops in
the motor windings (sensorless control). For the sensorless case, the induced voltage is detected by applying electric
current to two phases and not applying electric current to the remaining other phase. In this two-phase current on case,
there are six current application patterns as shown in Table 14-1, which are changed synchronously with the phases
of the rotor. In this two-phase current on case, the current on time in each phase is 120 degrees relative to 180 degrees
of the induced voltage.
is controlled by PWM. At this time, the current on windings need to be changed in synchronism with the phases of
the voltage induced by revolutions. Control timing in cases where the current on windings are changed by means of
sensorless control is illustrated in Figure 14-4. For three-phase motors, zero-crossing occurs six times during one cycle
of the induced voltage (electrical angle 360 degrees), so that the electrical angle from one zero-cross point to the next
is 60 degrees. Assuming that this period comprises one mode, the rotor position can be divided into six modes by zero-
cross points. The six current application patterns shown above correspond one for one to these six modes. The timing
at which the current application patterns are changed (commutation) is out of phase by 30 degrees of electrical angle,
with respect to the position detection by an induced voltage.
zero-cross point. Because mode time corresponds to 60 degrees of electrical angle, the following applies for the case
illustrated in Figure 14-4.
of the induced voltage for reasons that even after current application is turned off, the current continues flowing due
to the motor reactance.
times during 360 degrees of electrical angle and activating commutation, position detection start, and other operations
according to that timing.
the microcontroller’s PMD unit.
The following explains the method for controlling a brushless DC motor with sine wave drive. In a brushless DC
For brushless DC motors, the number of revolutions is controlled by an applied voltage, and the voltage application
Mode time is obtained by detecting a zero-cross point at some timing and finding an elapsed time from the preceding
Timings are calculated in this way. The position detection start timing in 2 is needed to prevent erroneous detection
Control is exercised by calculating the above timings successively for each of the zero-cross points detected six
In this way, operations can be synchronized to the phases of the induced voltage of the motor.
The timing needed for motor control as in this example can be set freely as desired by using the internal timers of
Note:One of the upper or lower transistors is PWM controlled.
Outline of Motor Control
1. Current on windings changeover (commutation) timing
2. Position detection start timing 45 degrees of electrical angle = mode time × 3/4
3. Failure determination timing 120 degrees of electrical angle = mode time × 2
Table 14-1 Current Application Patterns
30 degrees of electrical angle = mode time/2
Application Pattern
Current
Mode 0
Mode 1
Mode 2
Mode 3
Mode 4
Mode 5
OFF
OFF
OFF
OFF
ON
ON
u
Upper Transistor
OFF
OFF
OFF
OFF
ON
ON
v
OFF
OFF
OFF
OFF
ON
ON
Page 136
w
OFF
OFF
OFF
OFF
ON
ON
x
Lower Transistor
OFF
OFF
OFF
OFF
ON
ON
y
OFF
OFF
OFF
OFF
ON
ON
z
Current on Winding
U→W
V→W
W→U
W→V
U→V
V→U
TMP88FW45AFG