National Instruments NI 9751 User manual

SHC68-68-RDIO

USER MANUAL
NI 9751
NI Powertrain Controls Direct Injector Driver Module
Contents
Safety Guidelines...................................................................................................................... 2
Introduction .............................................................................................................................. 2
Pinout........................................................................................................................................ 3
Hardware .................................................................................................................................. 4
Powering the Module................................................................................................................ 4
Platform Compatibility ............................................................................................................. 6
Internal Boost Power Supply.................................................................................................... 7
Direct Injector Drivers.............................................................................................................. 10
Connecting Injectors to the Module ......................................................................................... 25
Specifications............................................................................................................................ 26
Where to Go for Support .......................................................................................................... 29

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Safety Guidelines
High Voltage The NI 9751 normally operates at voltages up to 190 V. Take
extreme care to protect against shock. Even when the NI 9751 is completely powered
off, allow approximately three minutes for the internal high voltage to dissipate. Do
not touch any of the module screw terminals or injector terminals while the NI 9751
is powered on.
Caution Do not operate this module in a manner not specified in these operating
instructions. Product misuse can result in a hazard. You can compromise the safety
protection built into the product if the product is damaged in any way. If the product
is damaged, return it to National Instruments for repair.
Caution The fuse illustrated in Figures 32 and 33 is user-supplied and required in
all instances.
Introduction
The NI 9751 Direct Injector (DI) Driver Module includes the following components:
• CompactRIO (cRIO) module with the following components for driving a variety of diesel
and gasoline DIs, including many piezo actuated injectors:
– 3-channel solenoid injector drivers
– 2-channel piezo injector drivers (in piezo mode)
– Up to 120 V internal boost power supply in solenoid mode
– Up to 190 V internal boost power supply in piezo mode
– Up to 40 A peak current drive
– 7 V to 32 V battery
– Optional external input for high voltage supply (up to 190 V)
• Internal boost supply automatically shuts down when external high voltage
applied is greater than 24 V
– Circuit protection and diagnostics features, including:
• Protected against INJ± short to battery/high voltage
• Protected against INJ± short to GND
• Internal power supply overload protection
• Internal power supply over-charge protection
• Module temperature protection
• Open circuit detection
• Fault flags reported for all above conditions

NI 9751 User Manual |© National Instruments |3
• LabVIEW FPGA and RT VIs with the following features for engine-synchronous,
multi-pulse injection control strategies:
– Up to 16 pulses per injection cycle (Engine Speed Limited)
– Configurable for any combination of angle and time triggering
– Current control profile with the following characteristics:
• Up to 8 phases
• Each phase provides settings for upper and lower current dithering setpoints
• Duration and drive voltage (battery or boost) specified for each phase
• First phase can be configured to end after first peak
• DI Calibrator application, which assists with firing injectors on a test bench for configuring
the injector current/voltage profile
• Piezo injector operation for unipolar drive
• Inverted piezo drive supported (Discharge = ON, Charge = OFF)
Each DI driver channel is individually controlled for timing and duration, but channel operation
cannot overlap. The NI 9751 cannot control piezo and solenoid actuator types simultaneously.
When configured for piezo mode, channel 3 is not available and you must short the terminals
together.
Pinout
BATT
INJ1–
INJ1+
INJ2–
INJ2+
INJ3–
INJ3+
EXT PWR
GND
GND
0
1
2
3
4
5
6
7
8
9

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Hardware
The NI 9751 provides three channels for driving unipolar solenoid and piezo injectors in a
National Instruments cRIO module. Use the included internal boost power supply to provide
short phases of boosted voltages for higher current operation.
Powering the Module
The NI 9751 requires power from each of the following sources:
• The CompactRIO backplane male high density 15-pin DSUB (HD15) connector, which
mates with the female HD15 connector on the module. This power source provides a
regulated 5 V and ground to various digital logic functions. The CompactRIO 5 V source
is active whenever the CompactRIO or R Series Expansion Chassis is properly powered.
You can power the NI 9757 only at the HD15 connector by plugging it into a CompactRIO
or R Series Expansion Chassis. Do not connect the HD15 connector to any other device.
• The external screw terminal connector block, the terminals of which are labeled BATT (0)
and GND (9). A typical power source is an automotive 12 VDC or 24 VDC battery system,
but the NI 9751 can accept power from a range of 7 VDC to 32 VDC.
Caution You must use a UL-listed power supply with the NI 9751.
With the internal boost power supply and injector outputs disabled, the NI 9751 requires up to
100 mA from the external supply. The following formula calculates the total power required to
operate the module and drive injectors:
Where: Ip (A) = Peak current
Ih (A) = Hold current
HVTarget (V) = High Voltage Target from internal boost supply
BattV (V) = Battery voltage supplied to BATT(0)
Tip (sec) = Time of peak current phase
DurAve (sec) = Average duration of all injection pulses within an engine cycle
RPMmax (RPM) = Maximum engine speed in RPM
Nchan = Number of channels used
Npulse = Number of injection pulses per engine cycle
This formula assumes a 4-stroke engine cycle. For 2-stroke engines, multiply the result by 2.
Power HVT etarg IP×Tip×
20.70×
----------------------------------------------------- BattV Ih×DurAve Tip–()×+


RPMmax Nchan×Npulse×
260×
-------------------------------------------------------------------------
×=

NI 9751 User Manual |© National Instruments |5
A 100 W power supply is sufficient for most applications. Power requirements might peak up to
150 W for more demanding applications.
The external battery ground is isolated, within the module, from the CompactRIO 5 V supply
ground. You can externally connect the external battery ground and the CompactRIO ground.
Note Both power supplies must be active for software to recognize the module.
Caution The external battery supply input terminals are not protected against
reverse-voltage polarity. Connecting power to the module in reverse polarity will
damage the module. This event is not covered by warranty.
The NI 9751 includes an optional power input to the external screw terminal connector block
labeled EXT PWR (7). The ground reference for EXT PWR (7) must be the same ground as
GND (9). This power input can range from 24 V to 190 V and is optionally used to provide the
boost voltage in place of the internal boost supply. Because the internal boost power supply is a
significant contributor to the internal module heat generation, this external power input might be
necessary if the injector drive requirements, in combination with maximum engine speeds, cause
the internal module temperature to exceed the limit.
When a voltage greater than 24 V is applied to the EXT PWR (7) terminal, the internal boost
power supply automatically shuts off, even if it is enabled via software. Even when EXT PWR
(7) is connected to an external high voltage power source, BATT (0) must still be connected to
7 V to 32 V in order for the module to be properly powered for general functions. In most
applications the EXT PWR (7) terminal is not necessary and should be left unconnected.
Table 1. Example Power Calculation
Parameter Value
Ip 25 A
Ih 15 A
HVTarget 75 V
BattV 13.8 V
Tip 0.000100 sec
DurAve 0.000800 sec
RPMmax 4500 RPM
Nchan 3
Npulse 2
Power 65 W
Continuous Current 4.5 A

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Platform Compatibility
NI Powertrain Control modules require a hardware support system to function. You cannot use
the modules independently or interfaced with third-party devices at the backplane HD15
connector. NI Powertrain Control modules are compatible with the following National
Instruments platforms:
• CompactRIO, which consists of a CompactRIO controller, chassis, or integrated
controller/chassis.
• NI PXI, which consists of any NI PXI chassis, NI PXI RT controller, and NI PXI-78xxR
R Series FPGA card. The NI Powertrain Control modules insert into an NI R Series
expansion chassis. Connect an NI R Series expansion chassis to the NI PXI FPGA card
using a SHC68-68-RDIO cable.
Note NI Powertrain Control modules are not compatible with the National
Instruments CompactDAQ chassis.
You can use NI Powertrain Control modules with NI cRIO-911x, NI cRIO-907x, and NI R Series
Expansion systems under the following conditions:
• Leave one empty chassis slot between NI Powertrain Control modules and other
NI modules.
• Maintain an ambient system operating temperature of 0 °C to 45 °C.
Note Typical specifications of National Instruments modules might not apply when
used in a system with NI Powertrain Control modules.
Note National Instruments guarantees warranted specifications for all National
Instruments modules except thermocouple modules when used in a system with
NI Powertrain Control modules.
Note National Instruments recommends the NI 9214 for thermocouple
measurements in CompactRIO systems using NI Powertrain Control modules.
Note NI Powertrain Control modules do not support Scan Interface mode,
auto-detection, or ID mode.

NI 9751 User Manual |© National Instruments |7
Internal Boost Power Supply
The NI 9751 contains an internal boost power supply that can maintain a voltage level from
battery voltage up to 190 V. You can use software to enable or disable boost power supply at
any time. The internal booster power supply is disabled automatically whenever critical faults
occur and can only be enabled by clearing the faults. Internal capacitors store the high voltage,
which is used to drive the high-voltage phases of the injector current profile.
High Voltage The NI 9751 normally operates at voltages up to 190 V. Take
extreme care to protect against shock. Even when the NI 9751 is completely powered
off, allow approximately three minutes for the internal high voltage to dissipate. Do
not touch any of the module screw terminals or injector terminals while the NI 9751
is powered on.
Internal Boost Power Supply Performance
The following critical factors determine how well the internal boost power supply will perform
for a particular injector solenoid application:
• Injector solenoid resistance
• Injector solenoid inductance
• Peak current required to open the injector valve
• Working voltage requirement (HVTarget)
• Frequency of injection events
• Injector solenoid back-boost time (BackBoostTime)
Injector Solenoid Resistance
Typical common rail diesel injector solenoids will have a resistance of 1 Ωor less. This
resistance wastes, as heat, a portion of the energy supplied to the solenoid and affects the
maximum current achieved in the coil, which depends on the drive voltage applied. In general,
lower solenoid resistances are better for common rail solenoid injector applications.
Injector Solenoid Inductance
Typical common rail injector solenoids have an inductance of 1 mH or less. Inductance acts to
resist current change through the coil. As inductance increases, more time is required to achieve
the required peak current level, given a constant drive voltage. When you use the internal high
voltage to drive current, energy transfers from the internal high voltage capacitance to the
injector solenoid. Longer drive times deplete energy from the internal high voltage capacitance.
The internal boost supply works harder to maintain the high voltage target. Inductance is
proportional to the magnetic force generated for opening the injector valve.
Peak Current Requirement
Higher peak-currents require more energy from the internal boost power supply because the
internally stored high voltage depletes at a higher rate.

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Working Voltage Requirement
The internal boost power supply can maintain a higher working voltage to drive the peak current
level in a shorter amount of time and provide quicker valve opening times and more predictable
fuel injection quantities over a given injection duration. The boost power supplies operate less
efficiently at higher voltages. The power supply must work harder to maintain a higher working
voltage. Typical times to reach 20 A in common-rail diesel injectors are on the order of 30 to
100 μs, with a working voltage of 100 V.
Frequency of Injection Events
The frequency of injection events is directly proportional to the work the power supply requires
to maintain the working voltage.
Injector Back-Boost
You can obtain a significant and useful back-boost charge from the injector solenoid at the end
of each injection event. This back-boost from the solenoid depends on the hold-current level
during the injection event and the working voltage of the boost power supply. If you correctly
configure the current profile, a small back-boost on the order of 5 V occurs to the power supply,
which reduces the work required to maintain the working voltage.
You might incorrectly configure the module to use very little of the high voltage supply for
driving the peak current while also setting a high hold-current level. This configuration can lead
to back-boosting the power supply over the required working voltage. Use the internal high
voltage supply to prevent this from happening. If the working voltage exceeds 190 V, a fault
occurs and shut down proceeds automatically.
Power Supply Faults and Protections
The following critical faults related to the operation of the internal power supply might cause all
operations of the module to shut down automatically. Two or more of these faults might occur
under certain conditions. For example, the power supply might be loaded such that the board
temperature reaches its limit before the overload integrator limit is reached. You can re-enable
the internal boost power supply and injection control by manually clearing the faults with
software.
Power Supply Charge Fault (PSCharge)
If the power supply is actively attempting to recharge and detects that the voltage is not rising,
the charge fault is set. This fault most likely occurs when an internal problem, such as a capacitor
failure, exists with the module.
Power Supply Overload Fault (PSOverLoad)
The NI 9751 maintains an integrator of power supply usage. An internal counter increments with
each power supply voltage boost and decrements according to a fixed time interval. If the
integrator winds up to 148,480 counts, an overload fault is set. This fault indicates that the
module temperature will soon rise beyond the maximum operating temperature unless stopped.
The module temperature fault might trip before the overload fault, depending on the actual
conditions.

NI 9751 User Manual |© National Instruments |9
Module Temperature Fault (ModuleTemperature)
Due to the C Series module housing design, there is limited ability for heat to escape. The
primary source of heat within the NI 9751 is the internal boost power supply. If the internal
module temperature rises above approximately 80 °C, the module temperature fault is set.
High Voltage Limit Fault (HighVoltageLimit)
If the charge on the internal power supply exceeds 190 V, the high voltage limit fault sets. This
fault can occur due to excessive injector solenoid back-boosting. Excessive solenoid
back-boosting can be caused by driving solenoids with very high inductance while not using
the boost supply.
Internal Boost Power Supply Benchmarks
Table 2 describes bench test results that demonstrate power supply capability.
With air flow over the NI 9751, you can extend the duration of operation at heavy loads.
Table 2. Bench Test Results
Test Condition
Test 1
(Solenoid)
Test 2
(Solenoid)
Test 3
(Piezo)
External Battery Voltage (V) 13.8 13.8 13.8
HVTarget (V) 75 75 190
PeakCurrent (A) 27 27 8
PeakTime (ms) 0.18 0.18 s N/A
HoldCurrent (A) 15 15 N/A
BackBoostTime (ms) 0.20 0.20 N/A
Number of injectors operated 3 3 2
Number of fuel pulses per cycle 1 5 1
Simulated engine speed (RPM) 5,000 2,000 7,200
Length of test (min) 10 10 480
Ambient temperature (°C) 25 25 25
Final module temperature (°C) 50 75 72
Temperature stabilized? Y N Y
Injector under test Bosch P/N 0445 110 072
Mercedes Benz P/N 611 070 09 87
Bosch P/N
0445 115 027

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The internal power supply requires approximately 10 ms to charge from 12 V to 100 V, and
approximately 20 ms to charge from 12 V to 150 V. This charge-up process occurs immediately
when enabling the power supply. With the power supply enabled, the requested working voltage
is maintained while injection events are not commanded. Depending on the working voltage,
you might hear a slow frequency of faint clicks from the module. This is normal noise from the
power supply.
The DI Calibrator application can assist you in determining the proper current and voltage
profile settings to meet your injector solenoid requirements. NI will assist you with determining
calibration parameters for your injectors at no cost if NI can reuse the calibration data for future
projects. This does not include fuel flow measurements. You must provide NI with current
profile information and a test solenoid or injector.
When the internal supply is disabled, the high voltage bleeds down to battery voltage from 190 V
in approximately 3 minutes.
Connecting an External Power Supply to EXT PWR (7)
Connect an optional high voltage external power supply to the EXT PWR (7) terminal if the
internal boost power supply is overheating or cannot keep up with the injection requirements.
Inside the module, the external high voltage supply connects to the same internal capacitance as
the internal boost supply. Ensure that you make a permanent connection before you power the
external power supply. When an external high voltage supply greater than 24 V is detected, the
internal boost supply automatically shuts down. The BATT (0) terminal must still be connected
and powered by 7 V to 32 V even when you use an external high voltage supply connected to
the EXT PWR (7) terminal. A high voltage external power supply is not necessary for most
applications.
If the internal boost power supply cannot meet the demands of the application, consider using
only two of the three available channels instead of all three before using an external high voltage
power supply. For example, consider using three DI driver modules for a six-cylinder engine to
lighten the load on each module.
Suggested External High Voltage Supplies
TDK Lambda Genesys 100-15
Direct Injector Drivers
Injector Driver Circuit Description
The NI 9751 contains three solenoid DI drivers and can drive two Piezo injectors. The driver
channels share some circuitry, so injection events cannot overlap among channels within the
same module. If injection events with different injectors must overlap, you must use multiple
modules. The NI 9751 contain a high-voltage circuit and battery-voltage circuit that drive
current to the injector load. Figure 1 shows the high-voltage and battery-voltage drive circuits in
the simplified schematics for operating various types of injectors.

NI 9751 User Manual |© National Instruments |11
Solenoid Injector Operation
Figure 1 shows a representative simplified schematic that drives three solenoid injectors.
Figure 1. NI 9751 Simplified Schematic for Solenoid Injectors.
You can programmatically specify up to eight sequential drive phases within each solenoid
injection command pulse by using an 8-element IPhaseArray. Each phase is implemented
sequentially and can specify upper and lower current dithering setpoints, phase duration, and
high-voltage or battery-voltage drive circuit. Use the high-voltage drive circuit only when
necessary to conserve internal boost power supply energy and not overload it. A dual comparator
feedback circuit for upper and lower dithering thresholds controls the solenoid current. Other
current- and voltage- sensing circuits are used for fault detection.
Current Sense
& Comparator
Circuitry
Injector 1 Injector 2 Injector 3
+++
–––
CH1
Low-Side
Switch
CH2
Low-Side
Switch
CH3
Low-Side
Switch
Internal Boost
Power Supply
High-Side,
High-Voltage
Switch
High-Side,
Low-Voltage
Switch
BattV

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Figures 2 through 9, show oscilloscope images that demonstrate waveforms for four different
IPhaseArray configurations. Three of the examples show common direct injection waveforms.
The fourth waveform is not typical, but shows the flexibility of the IPhaseArray interface. The
total duration of the injection command is not determined by the total durations of the
IPhaseArray elements, but by the Boolean command delivered to the DI Driver FPGA Express
VI. If the Duration parameter of an IPhaseArray element is set to 0, the current levels for that
element are carried out for the remainder of the injection command.
Figure 2. Solenoid IPhaseArray Configuration Example 1
Figure 3. Current and Voltage Traces from Solenoid IPhaseArray Configuration Example 1
Figure 4. Solenoid IPhaseArray Configuration Example 2

NI 9751 User Manual |© National Instruments |13
Figure 5. Current and Voltage Traces from Solenoid IPhaseArray Configuration Example 2
Figure 6. Solenoid IPhaseArray Configuration Example 3
Figure 7. Current and Voltage Traces from Solenoid IPhaseArray Configuration Example 3

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Figure 8. Solenoid IPhaseArray Configuration Example 4
Figure 9. Current and Voltage Traces from Solenoid IPhaseArray Configuration Example 4
Phase1FirstPeakEnable
The Phase1FirstPeakEnable is a Boolean control that transfers operation from the first phase to
the second phase upon reaching the first current peak that corresponds to the first phase IUpper
threshold, as shown in Figure 10.
Figure 10. Current and Voltage Traces from
Phase1FirstPeakEnable=TRUE Operating Mode

NI 9751 User Manual |© National Instruments |15
BackBoostTime
The BackBoostTime is a global parameter that is critical for proper solenoid injector control.
This time period directly follows the end of the injection command duration and allows the
back-emf of the injector solenoid to be directed to the internal power supply for back-boosting
the internal high voltage power supply. The BackBoostTime brings the injector solenoid current
quickly to zero. If BackBoostTime is set to zero, injector current recirculates through the injector
until the energy dissipates, which might cause unpredictable injector valve closing. Calibrate the
BackBoostTime long enough for the energy within the injector solenoid to fully discharge to the
internal boost power supply. If BackBoostTime is greater than zero, but too short, the injector
current bumps up and recirculates until the energy fully dissipates. Extend BackBoostTime until
the scope solenoid current trace can no longer display the current recirculation. A typical
BackBoostTime is approximately 0.2 ms. Injectors with higher inductance provide more energy
to dissipate at the end of injection and thus require a longer BackBoostTime. Figures 11
through 15 show different values for BackBoostTime applied to the same solenoid injector.
Figure 11. BackBoostTime = 0.0 ms
Figure 12. BackBoostTime = 0.025 ms

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Figure 13. BackBoostTime = 0.050 ms
Figure 14. BackBoostTime = 0.100 ms
Figure 15. BackBoostTime = 0.150 ms

NI 9751 User Manual |© National Instruments |17
Piezo Injector Operation
The NI 9751 can of drive unipolar piezo injectors. Unipolar means the piezo injector is charged
to a positive voltage and discharged to ground. Bipolar drive means the piezo injector can be
charged to a positive or negative voltage. Channels 1 and 2 are viable for driving piezo
injectors. You must connect Channel 3 with a shorting jumper between the Inj+ and Inj-
terminals.Electrically, piezo injectors are a capacitive load, instead of an inductive load from
solenoid injectors. Solenoid injectors require current to be driven through the solenoid to create
the proper magnetic field within the injector body to mechanically open a valve. Piezo injectors
contain a stack of piezo crystal elements that respond mechanically to a voltage applied across
the stack. The two pins of the piezo injector are connected internally across the stack. As the
voltage across the stack increases, the stack expands, and exerts a force to open a fluid valve.
The piezo injectors respond more quickly than a solenoid operated injector. It is difficult to
estimate the fuel quantity injected while the injector valve is opening. By achieving a shorter
time from energizing to valve opening, the fuel injection quantity can be metered more
precisely.
Electrically, a piezo stack is like a capacitor because it requires current in one direction to charge
up to a specified voltage, and current in the opposite direction to discharge.The typical charge
voltage required for piezo injectors ranges from 100 V to 200 V. Most piezo injectors in
production today require up to 165 V, but vary depending on desired fuel rail pressure. A piezo
stack charges up to a specified voltage at a rate that does not damage the stack. The charge and
discharge current must be controlled. You can control charge and discharge current with an
inductive element in series with the piezo stack and treating the element similar to a current
control inductive load. The NI 9751 provides a special piezo mode of operation that utilizes the
same IPhaseArray interface to control current to the piezo stack for charge and discharge rates.
When charging the piezo stack, the final charge is a few volts less than the HVTarget setpoint.
When discharging the piezo stack, the final discharge state is 0 V.
The IPhaseArray behaves differently in piezo mode. The first four elements of the IPhaseArray
are used for charge and the last four elements are used for discharge. The BackBoostTime
parameter is not used for piezo injector operation. The DriveSrc Boolean for each IPhaseArray
element is not applicable for piezo injector operation because the high-voltage driver circuit is
always used. Figure 16 shows a representative simplified schematic that drives two piezo
injectors.

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Figure 16. DI Driver Simplified Schematic for Two Piezo Injectors
Internal Boost
Power Supply
Current Sense
& Comparator
Circuitry
High-Side,
High-Voltage
Switch
47 µH
Inductor
47 µH
Inductor Short
+++
–––
Piezo
Injector 1
CH1
Low-Side
Switch
CH2
Low-Side
Switch
CH3
Low-Side
Switch
Piezo
Injector 2

NI 9751 User Manual |© National Instruments |19
The NI 9751 can also operate inverted charge scheme piezo injectors. The PiezoInvert Boolean
determines the inverted piezo mode. The injector valve closes when the stack is charged and the
valve opens when the stack is discharged. Channel 1 can operate only a single piezo injector
when operated in inverted mode.You must leave Channel 2 disconnected and connect Channel 3
with a shorting jumper between the Inj+ and Inj- terminals. When you enable PiezoInvert mode,
the first four IPhaseArray elements are used for discharge and the last four elements are used for
charge. Figure 17 shows a representative simplified schematic that drives a single piezo injector
in inverted mode.
Figure 17. DI Driver Simplified Schematic for a Single Inverted Piezo Injector
Internal Boost
Power Supply
Current Sense
& Comparator
Circuitry
High-Side,
High-Voltage
Switch
47 µH
Inductor ShortOpen
+++
–––
Piezo
Injector 1
CH1
Low-Side
Switch
CH2
Low-Side
Switch
CH3
Low-Side
Switch