tmp89fm82 TOSHIBA Semiconductor CORPORATION, tmp89fm82 Datasheet - Page 298

• Manufacturer Part Number: tmp89fm82
• Description: 8 Bit Microcontroller Tlcs-870/c1 Series
• Manufacturer: TOSHIBA Semiconductor CORPORATION

19.1
Outline of Motor Control
RA000
19.1
brushless DC motor, which stator windings 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 de-
termined using a sensor such as a hall IC or by detecting polarity change (zero-cross) points of the induced voltage
that generated by the motor rotation (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 turn on case, there are six current application patterns as shown in Table 19-1, 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.
controlled by PWM. At this time, the current on windings need to be changed in synchronism with the phases of the
induced voltage. Control timing in cases where the current on windings are changed by means of sensorless control
is illustrated in Figure 19-4. 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 shift 30 degrees of electrical angle, with respect to the
position detection by an induced voltage.
elapsed time from the preceding zero-cross point. Because mode time corresponds to 60 degrees of electrical angle,
the following applies for the case illustrated in Figure 19-4.
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.
microcontroller’s PMD unit.
is accomplished by counting degrees of electrical angle and calculating the voltage data and sine wave data at the
counted degree of electrical angle.
The following explains the method for controlling a brushless DC motor with 120 degree control wave drive. In a
For brushless DC motors, the number of revolutions is controlled by an applied voltage, and the voltage level is
Mode time (60 degree rotation time) is obtained by detecting a zero-cross point at some timing and finding an
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 for motor control as in this example can be set freely as desired by using the internal timers of the
As for sine wave control, it requires controlling the PWM duty cycle for each pulse. Control of PWM duty cycles
Note:One of the upper or lower transistors is PWM controlled.
Outline of Motor Control
1. Current on windings change (commutation) timing : 30 degrees of electrical angle = mode time/2
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 19-1 Current Application Patterns
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 282
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
TMP89FM82