DSC MC56F84xxx in the motor control application

Freescale Semiconductor
Application Note
Document Number:AN4625
Rev. 0, 10/2012
DSC MC56F84xxx in the motor
control application
by:
Arendarik Stanislav
Contents
1 Introduction
1
Introduction................................................................1
3-phase high voltage or low voltage motors are used in large
number of applications. The various types of motors require a
various control algorithms, which are often very complex.
Freescale offers a family of Digital Signal Controllers (DSC)
MC56F84xxx dedicated for control of complex motor control
algorithms. One of the latest DSC is 100MHz 32-bit
MC56F84789. For the successful control of the application the
DSC peripherals must be utilized and properly connected to
the power hardware control and feedback signals.
2
Key peripherals dedicated for motor control
applications...............................................................1
3
Power Stage Structures.............................................2
4
2 Key peripherals dedicated
for motor control
applications
The two eFlexPWM modules PWMA and PWMB for the
control signal generation
• up to 12 output PWM channels
• 16-bit resolution for edge, center aligned or
asymmetrical PWM
• Independent control of both edges of each PWM output
• Independently programmable PWM output polarity
• Independent top and bottom deadtime insertion
© 2012 Freescale Semiconductor, Inc.
5
3.1
Motor Inverter...............................................2
3.2
Interleaved PFC Stage....................................3
3.3
Current and Voltage
Measurement..................................................4
Hardware Connections..............................................4
4.1
Power Supply and DSC's JTAG
Interface connection.......................................5
4.2
One 3-Phase Motor without PFC
Stage...............................................................5
4.3
One 3-Phase Motor with PFC
Stage...............................................................7
4.4
Two 3-Phase Motors with PFC
Stage...............................................................8
Conclusion.................................................................9
Power Stage Structures
• Each complementary pair can operate with its own frequency and deadtime values
• The PWMA supports NanoEdge placement with 312 ps high resolution
Two independent 12-bit high speed cyclic ADC for the analog signal measurements:
• 8-channel external input each
• 300 ns conversion speed
• Each ADC has ability to scan and store up to 8 conversion results
•
•
•
•
•
•
•
•
1 x 24-channel 16-bit SAR ADC
1 x 24-channel 16-bit SAR ADC
One quadrature decoder
Two periodic interval timers
Two programmable delay blocks
One 12-bit DAC
Four high speed comparators with 6-bit DACs for comparator reference
Dual inter-module crossbar switch enabling user configuration of data path between internal modules and between
internal modules and GPIO pins.
This DSC with large FLASH (up to 256 KB) and RAM (up to 32 KB) memories is running at 100 MHz. It is powered
from +3.3 V power supply and it has the 5 V tolerant I/O pins.
DSC is able to control two 3-phase motors together with one common power factor control (PFC) stage simultaneously.
The suggested connections for the one or two 3-phase motors optionally with PFC stage are proposed below.
3 Power Stage Structures
Let's start with the design of the key parts of typical power stage.
• Motor inverter
• Interleaved PFC
• Current and voltage feedback measurement.
3.1 Motor Inverter
The basic hardware connection for one motor is shown in Figure 1.
DSC MC56F84xxx in the motor control application, Rev. 0, 10/2012
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Freescale Semiconductor, Inc.
Power Stage Structures
DC-Bus
+15V
PWM1_AT
PWM1_BT
PWM1_CT
PWM1_AB
PWM1_BB
PWM1_CB
Q1
GAT
GBT
GCT
Gate
drivers
GAT
Q5
GCT
VoutA
VoutB
VoutC
GAB
GBB
GCB
Q2
GAB
R4
GND
Q3
GBT
Q4
GBB
3~
Q6
GCB
IsA+
IsB+
IsC+
R1
IsA–
R2
IsB–
R3
IsC–
Is_DCB–
Is_DCB+
Figure 1. 3-Phase Motor Connection
The Figure 1 shows the basic internal connection of the 3-phase power module typical for motor control application. The
input gate driver block receives the control signals from the control DSC and generates the control signals for the IGBTs or
MOSFETs. This stage is usually able to accept the control signals of the 3.3 V to 5 V level. The block of the gate drivers is
powered from the +12 V to +15 V power supply (Vdd). The 3-phase bridge of the power MOSFETs or IGBTs is powered
from the high voltage DC-Bus line (100V DC to 400V DC).
3.2 Interleaved PFC Stage
The PFC stage is commonly used to improve the efficiency of the power consuming from the power line. The power factor is
decreased by the current spikes when the DC-Bus capacitors are charged from the standard diode bridge rectifier. The PFC
stage maintains the mains current nearly sine shape, thus the power factor is close to 1.
Vin
L1
D1
L2
D2
DC-Bus
+15V
Q1
PWM1_PFC1
PWM1_PFC2
Q2
Dual
gate
driver
Is1_PFC+
R1
Is1_PFC–
+
C1
Is2_PFC+
R2
Is2_PFC–
GND
Figure 2. Interleaved PFC Stage
The basic structure of the interleaved PFC stage is shown in Figure 2. The input to the PFC stage is the Vin voltage. It is the
power line AC voltage rectified by the diode bridge. Vin is the pulsating DC voltage. This voltage is measured by the control
DSC. The DSC generates the PWM control signals for the power MOSFETs in order to consume sine shape current from the
power line. The high frequency switching currents are sensed by the current sense resistors R1 and R2, then amplified and
measured by the ADC module of the DSC. The output DC-Bus voltage is usually stabilized at level about 380V DC. The
DC-Bus voltage provides power for the motor inverter.
DSC MC56F84xxx in the motor control application, Rev. 0, 10/2012
Freescale Semiconductor, Inc.
3
Hardware Connections
3.3 Current and Voltage Measurement
The current and voltage measurement is the key factor for the proper control of the motor. The currents of the each phase are
sensed by the power current sense resistors. The voltage on the each sensing resistor is amplified by the measurement
amplifier. The structure of this current sense amplifier is shown in Figure 3. The amplification factor is suggested to be lower
than 10.
Voltage levels are typically measured by the simple voltage divider, which scales the high voltage to proper level acceptable
by the processor. The voltage dividers for phase B and C are like for the phase A in Figure 3.
+3.3VA
DC-Bus
Vin-RECT
R14
R5
VoutA
R11
IsA– R1
R8
R3
U3
–
R15
R12
V-DCB
C5
R16
C4
GNDA
C1
R9
Vin
R13
V-A
C3
GNDA
IsA+ R2
R10
+1,65Vref
GNDA
+
R4
V+
V–
R7
I-A
C2
R6
GNDA
Figure 3. Voltage dividers and current sense amplifier for phase A
The input components R1, R2 and C1 form the noise filter. The voltage reference +1.65 V enables the measurement of
currents of the both polarities. For the DC-Bus current measurement this reference voltage is equal to zero. Then the only
positive current polarity is measured. At the output of this amplifier is the simply low pass filter which improves the
measurement accuracy. The output of this filter is connected to the ADC input of the DSC.
4 Hardware Connections
This section describes the DSC MC56F84xxx connections for the various configurations of the motor control application.
The field oriented control (FOC) is mostly used for control of the 3-phase generic motors. The control algorithm requires the
simultaneous (at the same time) measurement of the currents of the two phases of the 3-phase system. This task can be
accomplished by the two ADC modules in the DSC. The measured values are processed by the DSC software algorithm. The
control algorithm then generates the 3-phase PWM signals for the power stage control. The basic control algorithm is shown
in Figure 4.
DSC MC56F84xxx in the motor control application, Rev. 0, 10/2012
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Freescale Semiconductor, Inc.
Hardware Connections
wreq
Ramp
Speed
control
+
Q-Current control
torque
PI
controller
–
Field
control
+
PI
controller
–
DC-Bus/measured
Uq
a,b
Ud
+
d,q
PI
controller
–
Ua
Ub
a,b,c PWM-C
PWM-B
PWM-A
a,b
DC-Bus
ripple
elimination
D-Current control
flux
a,b
I,a
I,b
d,q
q
est
west
DC-Bus
a,b,c
3-phase
power
stage
la
lb
a,b
Back-EMF
observer
Tracking
observer
3~
Figure 4. Basic Control Block for PMSM
The control DSC MC56F84xxx is able to manage all these tasks for simultaneous control of the two motors with PFC stage
together. The following sections describe the suggested hardware connection for one and two motor control with PFC stage.
4.1 Power Supply and DSC's JTAG Interface connection
The DSC's power supply pins and JTAG connection for DSC is shown in Figure 5. Please meet the basic power supply rules
for the layout design – place the blocking capacitors as close to DSC's power supply pins as possible.
+3.3V
+3.3V
7
43
67
96
31
+3.3VA
C8
0.1u
32
16
35
93
GNDA
C9
C10
C11
C12
C13
C14
C15
0.1u
0.1u
0.1u
0.1u
2.2u
2.2u
2.2u
8
44
66
97
15
VDD1
VDD2
VDD3
VDD4
VDDA
VSSA
VCAP1
VCAP2
VCAP3
R1
47k
TDI
TDO
TCK
TMS
RESET
100
98
1
99
2
VSS1
VSS2
VSS3
VSS4
VSS5
R2
47k
1
3
5
7
9
11
13
J1
R3
47k
2
4
6
8
10
12
14
JTAG
MC56F84789_LQFP-100
GND
Figure 5. DSC's power supply pins and JTAG connection.
4.2 One 3-Phase Motor without PFC Stage
This is the simplest motor control application usually used for the low power (< 100W) application. The power limitation is
due to valid regulation – the only low power motor control applications can be used without PFC stage.
DSC MC56F84xxx in the motor control application, Rev. 0, 10/2012
Freescale Semiconductor, Inc.
5
Hardware Connections
DC-Bus
AC line
Diode
bridge
3-Ph. inverter
motor 1
Control
PMSM
Feedback
Sensorless
FOC control
motor 1
Application
control
Application SW
DSC MC56F84xxx
Figure 6. One Motor Control without PFC Stage
The block schematic of the power circuit for the one motor control without PFC stage is shown in Figure 6. The power
supply schematic is shown in Figure 7.
DC-Bus
AC1
L
RV1
N
Input
filter
–DC
–
+15V
+3.3V
+3.3VA
C2
2n2
+DC
+
AC2
+
C3 C1
2n2 470u
L1
Auxiliary
DC/DC
C4
10u
C5 Bead
0.1u
L2
C6
0.1u
C7
2.2u
GND
Bead
PE
GND
GNDA
Figure 7. Power supply without PFC
The measured currents and voltages are scaled by the voltage dividers and measurement amplifiers and connected to the
control DSC as in Figure 8.
DSC MC56F84xxx in the motor control application, Rev. 0, 10/2012
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Freescale Semiconductor, Inc.
Hardware Connections
I-A
I-B
V-A
V-B
I-DCB
22
23
24
25
21
20
19
17
I-A
I-C
V-C
ANA0
ANA1
ANA2
ANA3
ANA4
ANA5
ANA6
ANA7
33
34
36
42
30
29
28
26
V-DCB
ANB0
ANB1
ANB2
ANB3
ANB4
ANB5
ANB6
ANB7
18
14
13
37
PWM1_AT
PWM1_AB
PWM1_BT
PWM1_BB
PWM1_CT
PWM1_CB
69
68
75
74
83
82
DC-Bus
PWM1_AT
PWM1_AB
PWM1_BT
PWM1_BB
PWM1_CT
PWM1_CB
VoutA
MOSFETs VoutB
+ drivers VoutC
Figure 1.
85
PWM1_D1
84
PWM1_D2
PWM2_AT
PWM2_AB
PWM2_BT
PWM2_BB
PWM2_CT
PWM2_CB
3~
GND
71
70
79
78
73
72
Voltage
dividers
Current
sense
amplifiers
Figure 3.
ANC16
ANC17
ANC18
ANC19
MC56F84789_LQFP-100
Figure 8. Measurement and control signals for one 3-phase motor without PFC
4.3 One 3-Phase Motor with PFC Stage
This configuration is often used for the high power motor control application. For higher power the interleaved PFC stage is
used.
DC-Bus
AC line
Interleave
PFC
Control
3-Ph. inverter
motor 1
Feedback
Control
Feedback
Sensorless
FOC control
motor 1
Interleave
PFC control
Application
control
PMSM
Application SW
DSC MC56F84xxx
Figure 9. One Motor Control with PFC Stage
The main 3-phase motor with the PFC stage connection is in Figure 9. The main power circuit for the one motor control with
PFC stage connection is shown in Figure 10.
DSC MC56F84xxx in the motor control application, Rev. 0, 10/2012
Freescale Semiconductor, Inc.
7
Hardware Connections
Vin-RECT Interleave
PFC
Figure 2.
AC1
L
RV2
Input
filter
–DC
–
N
+15V
DC-Bus
+3.3V
+3.3VA
C21
2n2
L4
+DC
+
Auxiliary
DC/DC
AC2
PWM1_PFC1
PWM1_PFC2
IPFC1
IPFC2
Bead
C23
0.1u
C22
2n2
C20
+ 470u
GND
C18
10u
C24
0.1u
C19
2.2u
L3
Bead
PE
GND
GNDA
Figure 10. Power supply with interleaved PFC stage
The DSC power supply circuits and JTAG connection are the same as in previous configuration. It is shown in Figure 5. The
measured currents and voltages are processed by the measurement amplifiers and connected to the control DSC as in Figure
11.
Vin-RECT
DC-Bus
Interleaved
PFC stage
PWM1_PFC1 Figure 2. Vin
Voltage
PWM1_PFC2 dividers V-DCB
Figure 3. I-PFC1
I-PFC2
I-A
I-B
V-A
V-B
I-DCB
I-PFC1
I-A
I-C
V-C
Vin
V-DCB
I-PFC2
GND
Current
sense
amplifiers
Figure 3.
22
23
24
25
21
20
19
17
33
34
36
42
30
29
28
26
18
14
13
37
ANA0
ANA1
ANA2
ANA3
ANA4
ANA5
ANA6
ANA7
ANB0
ANB1
ANB2
ANB3
ANB4
ANB5
ANB6
ANB7
PWM1_AT
PWM1_AB
PWM1_BT
PWM1_BB
PWM1_CT
PWM1_CB
69
68
75
74
83
82
PWM1_AT
PWM1_AB
PWM1_BT
PWM1_BB
PWM1_CT
PWM1_CB
VoutA
MOSFETs VoutB
+ drivers
Figure 1. VoutC
3~
85 PWM1_PFC1
PWM1_D1
84 PWM1_PFC2
PWM1_D2
PWM2_AT
PWM2_AB
PWM2_BT
PWM2_BB
PWM2_CT
PWM2_CB
71
70
79
78
73
72
ANC16
ANC17
ANC18
ANC19
GND
Voltage
dividers
Current
sense
amplifiers
Figure 3.
MC56F84789_LQFP-100
Figure 11. Measurement and control signals for one 3-phase motor with PFC
The difference to previous is only the PFC stage control PWMs and PFC currents measurement.
4.4 Two 3-Phase Motors with PFC Stage
This configuration is mostly used in the heating, ventilating and air conditioning (HVAC) appliances. This configuration
comprises the two PMSM with PFC stage as shown in Figure 12.
DSC MC56F84xxx in the motor control application, Rev. 0, 10/2012
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Conclusion
3-Ph. inverter
motor 2
DC-Bus
Control
Interleave
PFC
AC line
Control
Feedback
3-Ph. inverter
motor 1
Feedback
Control
Application
control
PMSM
#1
Feedback
Sensorless
FOC control
motor 1
Interleave
PFC control
PMSM
#2
Sensorless
FOC control
motor 2
Application SW
DSC MC56F84xxx
Figure 12. Dual Motor Control with PFC Stage
The hardware connection of the ADC and PWM pins of the control DSC is in Figure 13.
GND
Vin-RECT
DC-Bus
Interleaved
PFC stage
PWM1_PFC1 Figure 2. Vin
Voltage
PWM1_PFC2 dividers V-DCB
Figure 3. I-PFC1
I-PFC2
GND
Current
sense
amplifiers
Figure 3.
I1-A
I1-B
I2-A
I2-B
I-PFC1
V1-A
V1-B
I-DCB1
22
23
24
25
21
20
19
17
I1-A
I1-C
I2-A
I2-C
I-PFC2
V1-C
Vin
I-DCB2
33
34
36
42
30
29
28
26
V2-A
V2-B
V2-C
18
14
13
37
ANA0
ANA1
ANA2
ANA3
ANA4
ANA5
ANA6
ANA7
ANB0
ANB1
ANB2
ANB3
ANB4
ANB5
ANB6
ANB7
PWM1_AT
PWM1_AB
PWM1_BT
PWM1_BB
PWM1_CT
PWM1_CB
69
68
75
74
83
82
PWM1_AT
PWM1_AB
PWM1_BT
PWM1_BB
PWM1_CT
PWM1_CB
85 PWM1_PFC1
PWM1_D1
84 PWM1_PFC2
PWM1_D2
PWM2_AT
PWM2_AB
PWM2_BT
PWM2_BB
PWM2_CT
PWM2_CB
71
70
79
78
73
72
ANC16
ANC17
ANC18
ANC19
MC56F84789_LQFP-100
PWM2_AT
PWM2_AB
PWM2_BT
PWM2_BB
PWM2_CT
PWM2_CB
MOSFETs
+ drivers
Figure 1.
VoutA
VoutB
VoutC
3~
Voltage
dividers
Current
sense
amplifiers
Figure 3.
GND
MOSFETs
+ drivers
Figure 1.
VoutA
VoutB
VoutC
3~
Voltage
dividers
Current
sense
amplifiers
Figure 3.
Figure 13. Measurement and control signals for two 3-phase motors with PFC
5 Conclusion
The application note suggests the proper connection of the DSC MC56F84xxx for motor control applications. Particularly it
deals with ADC, PWM, current sensing and other necessary connections of pins of DSCs.
DSC MC56F84xxx in the motor control application, Rev. 0, 10/2012
Freescale Semiconductor, Inc.
9
Conclusion
The main peripherals for this application are the ADC and PWM modules. The ADC module is used for all voltage/currents
measurements. The ADC measurement moment must be properly set due to switching noise elimination. The ADC module
provides many options for the right sampling time synchronization with the generated PWM signals. The PWM module
generates the control signals for the power driver.
The right consideration must be done for each application regarding the package pinout. The lowest pin count package (48
LQFP) meets the minimum requirements for one PMSM control. The largest package (100 LQFP) can be used for the dual
motor control with PFC stage. The internal cross-bar supports flexibility for the final pinout configuration for the each
package.
DSC MC56F84xxx in the motor control application, Rev. 0, 10/2012
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Document Number: AN4625
Rev. 0, 10/2012
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