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SEMICONDUCTOR APPLICATION NOTE

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SEMICONDUCTOR APPLICATION NOTE
MOTOROLA
Freescale Semiconductor, Inc.
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AN1590
HIGH VOLTAGE MEDIUM POWER BOARD FOR THREE PHASE MOTORS
By Ivan Skalka, Leos Chalupa, Radim Visinka Industrial System Application Laboratory Motorola, Roznov pod Radhostem, Czech Republic
Freescale Semiconductor, Inc..
INTRODUCTION
This application note discusses one member of the Motor Control Kit, developed by Motorola. Motorola offers a wide variety of microcontrollers, analog ICs and power devices which leads to many possible types of control and power boards suitable for different applications. The Motor Control Kit takes advantage of this portfolio by allowing the optimum combination of boards to be selected, based on customer requirements.
This application note describes and explains how to use the High Voltage (HV) Power Board with Isolated Gate Transistors such as MOS or IGBT (Isolated Gate Bipolar Transistor) of up to a maximum of 400 V DC-Bus voltage and a maximum of 5A DC-Bus current. The power board is very suitable for driving three phase AC induction motors, three phase synchronous motors, three phase Brushless DC (BLDC) motors or Switch Reluctance (SR) motors with power ratings up to 600 W
Stepper Motor Power Board 1 Phase Power Board Microcontroller Board - HC16Y1 Microcontroller Board - HC08MP16 Microcontroller board - HC05MC4
HV Power Board with discrete IGBTs
LV Power Board HV Power Board with HPM
UNI-2
Figure 1-1.
Members of the Motor Control Kit
This document contains information on products under development. Motorola reserves the right to change or discontinue these products without notice.
MOTOROLA LTD., 1997. All trademarks are recognized.
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2 FEATURES
The High Voltage Power Board with discrete IGBTs has been developed as a member of the Motor Control Kit. This means that the power board must meet some common requirements and the most important is the interface between control and power boards. The block diagram of the power board is shown in Figure 2-1.
High Voltage Power Board
Power devices TO220+Diode Interface To micro board Opto isolation Drivers
COPACK Customer circuit area
To motor
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Extra PCB Board
Opto Opto
SENSING: DC Bus Voltage + DC Bus Current SENSING: Phase A, B, C Voltage
Figure 2-1. Features included are: · · · · · · · · · ·
Block diagram of the High Voltage Power Board
interface which meets the UNI-2 specification opto isolation
input gates (buffers or inverters) for PWM signals support for multiple package options of power switches DC-Bus current sensing DC-Bus voltage sensing
phase A, B, and C voltage sensing
resistor dividers for high voltage lines sensing measurement points for all important signals variable configuration
The connection to the all boards necessary for the whole system (microcontroller board, extra PCB boards) is provided through one common interface - UNI-2 (connector J1). The definition of the interface covers several possibilities in order to keep compatibility with the present power boards actually available. The base is an area with 40 holes which allows placement of several different connectors. Refer to Figure 2-2. for a description of each pin and its functionality. MOTOROLA For More Information On This Product, Go to: www.freescale.com AN1590
UNI-2 Interface Connector
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For more details refer to the UNI-2 specification.
Present interface UNI-1
2 connectors
New interface UNI-2
2 connectors
New interface UNI-2
1 connector
+5 V +5 V GND GND GND GND GND Reserved Reserved Reserved -5 V -15 V1 GND GND GND GND GND GND Vbus Isense
Atop Abot Btop Bbot Ctop Cbot GND Reserved Reserved Reserved Fault +15 V Phase A Phase B Phase C Reserved Reserved Vtemp GND Analog GND Analog
Ctrl1 Ctrl2 Ctrl3 Ctrl4 Ctrl5 Ctrl6 GND Reserved Reserved Reserved Fault +15 V Sense1 Sense2 Sense3 Reserved Reserved Vtemp GND Analog GND Analog
GND GND GND GND Reserved Reserved Reserved1 -5 V -15 V GND GND GND GND GND GND Vbus Isense
GND GND GND GND Reserved Reserved Reserved -5 V -15 V GND GND GND
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GND GND GND Vbus Isense
14+16 pins Some analog signals 0 - 2.5 V
14+20 pins All analog signals 0-5V
Figure 2-2.
Interface connector
40 pins All analog signals 0-5V
Signals Ctrl1 - Ctrl6 and Sense1 - Sense3 are defined for the three phase power board as follows: Ctrl1- PWM signal for the top transistor in phase A (Atop) Ctrl2 - PWM signal for the bottom transistor in phase A (Abot)
Ctrl3 - PWM signal for the top transistor in phase B (Btop)
Ctrl4 - PWM signal for the bottom transistor in phase B (Bbot) Ctrl5 - PWM signal for the top transistor in phase C (Ctop) Ctrl6 - PWM signal for the bottom transistor in phase C (Cbot)
Sense1 - It can be either an analog signal which represents voltage or current of phase A, or a digital signal. In analog form +5 V represents a maximal value of the sensed quantity. Sense2 - It can be either an analog signal which represents voltage or current of phase B, or a digital signal. In analog form +5 V represents a maximal value of the sensed quantity. Sense3 - It can be either an analog signal which represents voltage or current of phase C, or a digital signal. In analog form +5 V represents a maximal value of the sensed quantity.
It would be ideal to define ground signals to exclusively occupy one side of the connector and to allow an easier PCB layout, but compatibility with UNI-1 excludes this possibility. There are ground lines between all signals in the interface cable to avoid distortion of signals. The definition of the interface includes some spare pins which are available for the user. There are 2 spare pins in the two connector (14 + 20 pins) solution and 8 spare pins in the one connector (40 pins) solution. AN1590 For More Information On This Product, Go to: www.freescale.com MOTOROLA
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Opto-isolation
Driver for Isolated Gate Transistor
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+15V isol
R52 MGP20N60 DZ1 22V Q1 D1 MSR860
N.C. VDD HIN SD LIN VSS N.C.
R1 C1 1R0 220nF
1N4148 22R R2 22R D7 MUR160 R4 22R D15
MPIC2112
MUR160 C2 220nF D10
22R MGP20N60 DZ2 22V Q2
R53 22R
D2 MSR860
1N4148
Figure 2-3.
Example of Power Stage Solution
Figure 2-3. shows a solution for driving Isolated Gate Transistors.
Resistors R2, R4 (R6, R8, R10, R12) limit the switching speed and of course also the turn-off time. Increasing the value of the series gate resistors causes the amplitude of the negative spike decreases, while the turn-off time is a linear function of the series gate resistance. Experimental results show that R3 (R7, R11) suppresses the negative spikes on pin VS of the top transistor more effectively than R2. R3 (R7, R11) also has less effect on the turn-off time.
Resistors R52, R53 (R54, R55, R56, R57) and diodes D14, D15 (D16, D17, D18, D19) set different turn-off and turn-on times when such a function is required. The diode D10 (D11, D12) is another method of suppressing the negative spike on pin VS. The most important parameter of the diode is the turn-on time. In this case resistor R3 (R7, R11) limits the current through the diode.
Motorola allows and guarantees operation of the MPIC drivers up to a maximum of -5 V on pin VS (pin 5). For More Information On This Product, Go to: www.freescale.com
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The HV Power Board supports multiple package options for the power switches (TO220, TO247 and TO264). This also makes possible to mount discrete TMOS transistors or IGBTs with discrete fly-back diodes or a copack (IGBT with build-in diode) devices only. The following table summarises all combinations.
Device vs. package type Discrete power switch Discrete diode Copack IGBT TO220 TO220 No No No TO220 No No TO247 No No TO264 TO247 No No TO264 No No
Power Devices
only for T-MOS where its internal diode can be used instead of the discrete one
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Table 2-1. Figure 2-3. shows one possible configuration of the power stage. MGP20N60 MSR860 Collector-Emitter voltage Reverse voltage
Motorola MGP20N60 IGBTS and MSR860 diodes are used with the following characteristics: Collector current - continuous Rectified forward current 600 Vdc 20 A 8A 600 V
An emitter of the high side transistor and a collector of the low side transistor are disconnected to make possible the measurement of the leg current through every Isolated Gate Transistor. Before using this board each point pair: PH1-PH2, PH3-PH4, PH5-PH6 must be connected. The PCB layout is also designed for an easy mounting of the heatsink because the power switches are all in-line.
Sensing DC-Bus Voltage Sensing
The DC-Bus voltage is one of the feedback signals. An on-board resistor divider (R15-R18) and over voltage suppressor is provided (D13). The customer circuit area can be used for needed buffering, filtering and amplifying. Figure 2-4. shows an example:
R15 1M DC voltage max. 400 V R16 1M R17 1M R18 2k VCC D13 1N4004
Isolation amplifier
Amplifier
150pF
VCC 5V6 10nF
100nF 2k2 2k2 150pF
10k +15V 3 2 10k 8
max. 200 mV
HCPL7800 Customer circuit area
4 -15V
MC34082
Vout cca 5 V
Figure 2-4.
DC-Bus Voltage Sensing
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The resistor dividers of the phase output lines (R40-R51) give the possibility to sense the phase voltages. These can provide the feedback for the sensorless drive, the dead time compensation or other feedback techniques. The buffering, filtering and amplifying circuit can be similar as that for DC-Bus voltage sensing.
Phase A, B, C Voltage Sensing
Low pass filter 2n2 8 A Isolation amplifier VCC VCC 1N4004 5V6 10nF 1 1k0 2
DC-Bus Current Sensing
Amplifier 150pF +5 V 100nF 2k2 2k2 150pF 10k +15 V 5 6 8
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IGBTs Rsense R13
+15 VG 56k 56k 2n2 3 2
4 max. 200 mV -15 VG MC34082
HCPL7800
7 MC34082
Vout cca 5 V
Customer circuit area
Figure 2-5.
DC-Bus Current Sensing
The customer circuit area enables one to customise the HV Power Board functions (such as buffering, filtering, amplifying, limiting and limit detection of the sensed signals). The over(under)-voltage and the over-current detection can be designed on the board using this possibility.
Customer Circuit Area
All feedback signals as well as all power supply voltages are available close to the customer circuit area.
The isolation gap in the customer circuit area provides the possibility to place very easy an opto isolation device for feedback signals. If an extra PCB board is used to handle the feedback signals (see Figure 2-1.), then it can be mounted onto the HV Power Board above the customer circuit area. See Figure A-1. Schematic.
Power can be connected to the power board through J1 and / or J2 and / or J3. J1 is an interface connector (refer to Figure 2-1 for specifications). All important power supply lines are included in the interface connector and this configuration allows all boards to be supplied from one board which simplifies the system. Connector J2 is dedicated for the power side and J3 for the microcontroller side when optoisolators are used. There are also voltage regulators placed on-board: U11 (+5 V) for the power side and U12 (+5 V) for the microcontroller side. For power supply considerations, it should be taken into account whether opto-isolators are used and how many voltages (+5 V, +15V, ..) are needed on the microcontroller side and on the power side. Then the right case can be chosen and the minimal number of power supplies reached. Power side +15 V (through J2) - VCC is created on the board by U11.
Power Supply
For example. The necessary voltages for a power board with opto-isolators and HV DC bus voltage sensing (HCPL7800 and MC34082 see Figure 2-4.) are: Microcontroller side +15 V (through J3) - VCC is created on the board by U12. -15 V (through J3)
The voltages +5 V, +15 V, -15 V are also available for the microcontroller and other board through J1. MOTOROLA For More Information On This Product, Go to: www.freescale.com AN1590
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3 3.1 CONFIGURATION Jumper JP4 - PWM Signals
The Jumper JP4 selects between pull-up or pull-down configurations. 1. 2. 3. 4.
Creates the capability to drive the IGBT drivers when no opto-isolation is used.
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The explanation is the following. Not every microcontroller is able to sink 15 mA in a logical low level. Therefore the integrated circuit U1 has been included to provide extra current to drive the other devices. When a non-isolated application is being developed, the first step is the implementation of an isolated version with compatible functions and signals. The opto-couplers invert the signal, thus an additional IC can compensate this function and creates an easy transition from isolated to non-isolated version.
Creates an easy transition from an isolated application to a non-isolated version of an application during development.
1 VCC JP4 1 VCC from connector J1 10k
JP4 10k 1 +5V 2 330
VCC 2k2 100nF to MPIC2112
74LS05 A 2 74LS07
IGBT ON
HP4504
Figure 3-1.
Adjusting the Signal for Isolated Gate Transistor
When the logic gates are not used, it is necessary to connect together pins 1-2, 3-4, 5-6, 8-9, 10-11, 12-13 of U1.
Jumper JP4 and resistor network RN1 ensure the turn off level of the Isolated Gate Transistors when the connector J1 is disconnected.
WARNING
If the jumper JP4 is not set correctly, then all the power switches could be turned on during power turn on or off. If this happen when the DC-Bus capacitor is already charged, then it will cause the short circuit and may damage of the HV Power Board.
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Jumpers JP3 and JP5 - Fault Signal
WARNING
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Different motor control applications require the ground potential to be referenced differently (before or after current sensing resistor R13). The jumpers JP1 and JP2 allow to select the ground reference for the whole application accordingly (see Figure A-1. Schematic).
Jumpers JP1 and JP2 - Ground Reference
When the HV Power Board is used in non-isolated (the "Micro side" is not isolated from "Power side") configuration, then the soldering bridge SB1 must be established.
Soldering Bridge SB1 - Isolated or Non-isolated Configuration
Solder thick wire here if no isolation is used
Figure 3-2.
Soldering Bridge
The mechanical design of the HV Power Board offers two different connection possibilities for additional boards through the UNI-2 interface. The Figure A-3. shows the possible configuration. Some boards can be mounted on top of the customer circuit area or they can be put next the Power Board PCB. All boards can share the necessary signals via connectors of the UNI-2 interface. Thus a variable and flexible system is achieved. For More Information On This Product, Go to: www.freescale.com
Additional PCBs
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4 DRIVER FOR ISOLATED GATE TRANSISTORS AND RELIABILITY CONSIDERATIONS
Since high current switching at high speed is not done without some difficulties, there are some subtle aspects which must be taken into account when designing such circuits. The PCB layout is probably more important than the schematic. Optimization of the layout requires one to minimize the stray inductances which severely affect the behaviour of the board. Stray inductances in the main current path can store a significant amount of energy and, at turn-off of the switching device, the following problems may occur: 1. 2. 3. 4. High voltage spikes Additional power dissipation in the switching devices due to absorbed inductive energy Noise generation Negative spikes on pin 5 of MPIC2112
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The noise can disturb the control circuit or cause misfire of the switching devices. An excessive negative voltage spike can damage the control IC (latch-up).
A typical half-bridge circuit, that employs two Isolated Gate Transistors and an MPIC2112, is shown in Figure 4-1. The critical stray inductances, which affect the behaviour of the circuit, are located in the high current path. Ld1 and Ls2 are due to the wiring inductance between the Isolated Gate Transistors and the decoupling capacitor. Therefore in Figure A-1. there is a decoupling electrolytic capacitor, C8 and / or C9, located very close to the Isolated Gate Transistors and the capacitor C7 is split into two parts C7a and C7b to decrease the influence of the stray inductances Ld1 and Ls2.
MPIC2112 HO Ls1 Ld2 LO Q2 Q1 Lload Rload + Ls2 Ld1 +
Figure 4-1.
Half Bridge with Stray Inductance
PCB LAYOUT FOR HIGH SPEED AND HIGH CURRENT LINES
The PCB for the power board has been designed as a double-sided board. For PCB layout design it is strictly recommended not to use an common autorouter. Big problems usually occur when an autorouter is allowed to place high speed, high current lines without guidance for this kind of circuit. A few general rules are listed below, that can minimize the difficulties in PCB layouts: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. High current switching lines as short and as wide as possible Minimize the stray inductances Avoid loops Minimize the area of the remaining high current loops Locate proper high frequency decoupling close to the Isolated Gate Transistors A "three-to-one rule": the trace width should not be less than 1 / 3 of its length Minimize length of lines between MPIC and Isolated Gate Transistor, Isolation gap (opto isolation) Isolation gaps between high voltage lines If Isolated Gate Transistors in case TO220 are used, then the middle pin of the transistor must be bent out of line for good isolation between soldering pads (VDE regulation on isolation distance). For More Information On This Product, Go to: www.freescale.com
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6 STARTING ACTIVITIES
1. 2. 3. 4. 5. 6. 7. 8. 9. Consider polarization of signal for opto-isolators. Before using this power board for three phase motors, perform the following steps: Consider opto isolation. When the opto-isolators are omitted, then connect the solder bridge between the ground on the power side and the ground on microcontroller side (located close to the interface connector J1). Consider how many power supplies are needed for the control board and the power board including HV DC bus voltages. Choose the jumper JP1 or JP2 to select ground reference for the application.
Connect the points PH1-PH2, PH3-PH4, PH5-PH6 with wires which are only as long as necessary for leg current measurement.
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Set the jumpers JP3, JP4, JP5 when the shutdown signal for MPIC2112 drivers is required. Wire the connector J4 (only if needed) from points PH1, PH3, PH5. Connect the control signals via connector J1 (UNI-2 interface) Use the customer circuit area to create the desired circuit for feedback signals.
SAFETY CONSIDERATIONS WARNING
When working with opto-isolators do not touch the board or any of its components outside the isolation barrier When working with opto-isolators and the HV DC bus is powered directly from the line, do not connect any computer, scope or development system outside the isolation barrier. In this case is necessary to use an isolation transformer. When working without opto-isolators, do not connect any computer, scope or development system when the HV DC bus is powered directly from the line. In this case it is necessary to use an isolation transformer.
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APPENDIX A
The board provides a number of useful measurement points.
MP1 MP2 MP3 MP4 MP5 MP6 MP7 MP8 MP9 MP10 MP11 MP12 MP13 MP14 MP15 MP16 MP17 MP18 MP19 MP20 MP21 MP22 MP23 MP24 MP25 MP26 MP27 MP28 MP29 MP30 MP31 MP32 Gate of Q1 - Atop Gate of Q2 - Abot Phase A Gate of Q3 - Btop Gate of Q4 - Bbot Phase B Gate of Q5 - Ctop Gate of Q6 - Cbot Phase C Shunt DC Bus DC Bus + DC Bus sensing Fault signal (shut-down signal) Atop from microcontroller Abot from microcontroller Btop from microcontroller Bbot from microcontroller Ctop from microcontroller Cbot from microcontroller GND Isol. +5 V Isol. -15 V Isol. +15 V Isol. GND +5 V +15 V -15 V Phase A voltage (divided down-to 0-15V) Phase B voltage (divided down-to 0-15V) Phase C voltage (divided down-to 0-15V) Ground Reference - Isolated
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RN1 VCC R25 MP1 1 D1 MUR860 Q1 MP3 1 VCC isol U8 C1 220nF 1R0 R3 22R R4 D15 1 MP2 R22 MP4 1 R5 C3 220nF 1R0 D8 MUR160 1N4148 R6 22R C13 100nF U9 2k2 D16 R54 22R MGP20N60 D3 MUR860 Q3 DZ3 22V R7 22R D11 MUR160 D17 1 MP5 R31 1 C16 100nF +15V isol VCC isol 1 BF2 J6 BF1 1 Analog GND isol GNDP U10 2k2 C31 100nF MP7 1 1N4148 R8 22R R55 22R DZ4 22V Q4 MGP20N60 D4 MUR860 1N4148 22R R53 DZ2 22V 22R MGP20N60 D7 MUR160 R1 DZ1 22V 22R 1N4148 R2 22R MGP20N60 330 HP4504 R26 1 330 HP4504 U4 R21 C12 100nF 2k2 8 7 6 5 MPIC2112 C2 220nF D10 MUR160 MP15 1 R27 330 HP4504 U5 MP16 1 MP17 R28 330 HP4504 U6 R23 C14 100nF MP14 MPIC2112 1 R24 C15 100nF JP3 2k2 C4 220nF 2k2 1 MP18 1 R29 330 HP4504 U7 8 7 6 5 MP19 1 MP20 R30 330 HP4504 U13 C11 100nF U3 R20 2k2 8 7 6 5 8 9 10 11 12 13 14 N.C. VDD HIN SD LIN VSS N.C. Q2 HO VB VS N.C. VCC COM LO 7 6 5 4 3 2 1 C10 100nF C17 100nF GNDS 1 2 3 4 U2 8 7 6 5 R19 D14 R52 2k2
Across supply voltage pins of 74LS07
VCC VCC isol +15V isol
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1M5 R41 1M5 R42 1M5 MP29 A R43 150k
74LS07 U1B
74LS07 U1A
HV Power Board PCB
74LS07 U1F
74LS07 U1E
R44 1M5
74LS07 U1D
R45 1M5 R46 1M MP30 B R47 150k
74LS07
Figure A-1. Schematic
Micro side Customer Circuit Area
SB1 MP24 1 +15V isol -15V isol MP22 MP23 VCC isol 1 GNDS
100nF
R48 1M5
100nF
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Power side Customer Circuit Area
10uF / 50V
1M5 R50 1M MP31 1 C R51 150k
1000uF / 35V
Analog GND
1000uF / 35V
78L05
C21 100nF
100nF
10uF / 50V
100nF
Solder bridge. GND Junction when optoisolation is not used. min dist. 5mm
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Analog GND isol
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Connector for motor Power supply connector - isol.
Point for measurement
Co-pack or IGBT+Diode
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Customer circuit area microcontroller side
Wire connection
Interface connector Isolation barrier
Area for heatsink
Customer circuit area power side
Soldering bridge
Ileg Signals for customer circuit area
Power supply connector
Current probe
DC Bus
Figure A-2. PCB Layout
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Table A-1. List of components
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can be customized
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OPTIONS
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Sensor
Board
Figure A-3. Example of a Motor Control System AN1590
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3-Phas
e Powe
r Board
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How to reach us: MFAX: RMFAX0@email.sps.mot.com - TOUCHTONE (602) 244-6609 INTERNET: http://Design-NET.com USA / EUROPE: Motorola Literature Distribution P.O. Box 20912 Phoenix, Arizona 85036. 1-800441-2447 JAPAN: Nippon Motorola Ltd. Tatsumi-SPD-JLDC, Toshikatsu Otsuki, 6F Seibu-Butsuryu-Center, 3-14-2 Tatsumi Koto-Ku, Tokyo 135, Japan. 03-3521-8315 HONG KONG: Motorola Semiconductors H.K. Ltd. 8B Tai Ping Industrial Park, 51 Ting Kok Road, Tai Po, N.T., Hong Kong. 852-26629298
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