AN1524 Freescale Semiconductor / Motorola, AN1524 Datasheet - Page 6

• Manufacturer Part Number: AN1524
• Description: AC Motor Drive Using Integrated Power Stage
• Manufacturer: Freescale Semiconductor / Motorola

consists of an inverting amplifier with a 0.69 volt offset. The
output provides a temperature signal of approximately
26.5 mV/ C. The compensation capacitor is essential to avoid
oscillations with such a large feedback resistor. Resistor R20
biases the temperature sense diode at 1 mA. The bias current
can be increased if necessary to minimize noise problems.
However, the gain will have to be readjusted.
shown in Figure 8. The voltage divider provides a 0 to 5 volt
signal, 1 volt per 100 volts on the DC buss. Four resistors in
series are used to ensure the voltage rating of the resistors is
not exceeded for the high voltage system. The over–current
comparator trips at 4.25 volts. Some hysteresis is also
provided to prevent the brake from oscillating between the on
and off states. The resistive divider also serves as a bleeder
resistor to slowly discharge the buss capacitors. The high
voltage drive uses resistors twice the value shown for R11–14.
Logic Circuit
logic device for flexibility, see Figure 9. The 22V10 PLD has
12 input pins and 10 I/O pins. Seven of the outputs are
dedicated to the seven IGBT gate drives. Seven of the inputs
are configured for use with the seven transistor inputs. Seven
resistors are connected to the inputs and may be configured
as pull–up or pull–down resistors. The polarity of the input
signals may be changed by modifying the device equations
and setting the polarity jumper. One of the inputs is dedicated
as a hardware enable. The three remaining I/O pins are
available as programmable I/O signals to the ribbon
connector.
Complete Schematic & Bill of Materials
AN1524
(U1 PIN 3)
The temperature amplifier is shown in Figure 7. The circuit
The voltage divider and over–voltage comparator are
The input logic of the demo board uses a programmable
6
PlusT
(0.69 V)
+ 2.5 V
Figure 7. Temperature Amplifier
R23
3.40 k
R24
1.30 k
+ 5 V
R20
4.42 k
10.0 k
R22
C8
0.1 F
MC33272D
–
+
Freescale Semiconductor, Inc.
1000 pF
137 k
R21
U4a
C7
For More Information On This Product,
Go to: www.freescale.com
(ANALOG
OUTPUT)
TO
demo board. All of the component values listed in the
schematic are for the 1 hp 240 VAC configuration. Appendix
II is a bill of materials for the demo board. Again the values
listed are for the 1 hp 240 VAC configuration. The 2 hp 240
VAC configuration requires changing several resistor
component values. The 1 & 2 hp 480 VAC configurations
require changing J1 and using 1000 volt bootstrap diodes, in
addition to changing several resistor values. Alternate bill of
materials are available on special request.
PWM Signals
signals can be generated by a microcontroller. Two
microcontrollers suitable for this purpose are the MC68332
and the MC68HC16Y1. Basic code for PWM AC motor control
has been written for the MC68332 1 and the MC68HC16Y1 2 .
Both of these microcontrollers include a Time Processor unit.
The Time Processor unit is an autonomous timer which may
be micro–programmed for various time functions. A special
microcode primitive has been written called Multi–Channel
PWM 3 that can generate center aligned PWM signals with
dead time. A motor control development system has been
developed for the ’HC16Y1. The integrated power stage demo
board was designed specifically to interface directly to the
’HC16Y1 motor control development system. However, the
PLD provides added flexibility for use with different
microcontrollers.
USING THE IPS AC MOTOR DRIVE DEMO BOARD
+V M
Appendix I contains a complete board level schematic of the
The demo board requires a PWM signal source. The PWM
R11
82.5 k
R12
82.5 k
R13
82.5 k
R14
82.5 k
R15
3.32 k
Figure 8. Voltage Divider and Over–voltage
(4.25 V)
+ 5 V
R16
9.09 k
R18
51.1 k
Comparator
LM293AD
+
–
150 k
U3a
R19
+ 5 V
MOTOROLA
R17
2.2 k
(ANALOG
OUTPUT)
(TO PLD)
VO
OV