Enhanced Diagnostic and Protection of Motor Drivers to Assist Robust System Development. Ryan Kehr Application Manager TI Motor Drive

Transcription

1 Enhanced Diagnostic and Protection of Motor Drivers to Assist Robust System Development Ryan Kehr Application Manager TI Motor Drive 1

2 Ryan Kehr Application Manager - TI Motor Drive Career BS in Electrical Engineering Purdue University 2000: Joined TI as a system engineer in Op Amp team 2000: Moved to Audio Amplifier team late in the year 2010: Motor Drive Business Unit was formed and joined as Application Manager Expertise 18 years experience as system/application engineer defining and supporting analog power devices 2

3 Detailed Agenda Trend of Automotive application and Motor Drivers Autonomous driving, Electrical vehicle Example applications : EPS, Braking Technical Deep Dive architecture, value position and system implementation Serial Communication integrity Over current of Power FETs Open and Short of Motor Connection TI solution with PMIC + Motor Driver for robust system design PMIC diagnostic can connect Motor Driver protection 3

4 Innovative Automotive Solutions: more electrification and motorized systems More Electric Vehicles More Driver Assistance More Motors More Comfortable 4

5 Trend Example : Power Steering system Direct mechanical steering wheel Motorized system Hydraulic power steering PMIC DRV M Mechanical back up (human) assist Electrical Power Steering (EPS) Advanced electrification PMIC DRV M Autonomous driving PMIC DRV 5

6 Trend Example : Braking system Motorized system Vacuum booster Traditional Vacuum Boosters assist braking force, and the vacuum needs engine. No engine or engine stop Replace the engine/vacuum with a Brushless DC Motor Electrically assisted brake system PMIC DRV M TI Information Selective Disclosure 6

7 Detailed Agenda Trend of Automotive application and Motor Drivers Autonomous driving, Electrical vehicle Example applications : EPS, Braking Technical Deep Dive architecture, value position and system implementation Over current of Power FETs Serial Communication integrity Open and Short of Motor Connection TI solution with PMIC + Motor Driver for robust system design PMIC diagnostic can connect Motor Driver protection 7

8 Over current of Power FETs 8

9 Tech Deep Dive: Over Current detection System Requirements (during motor operation) Requirement : Detect over current VDRAIN Power Supply Potential effect : External power FETs potentially get damage or over heating if the shoot through current condition lasts long Requirement : Shutdown gate driver to stop the shoot-through current Gate Driver GHx Big shoot through current SHx GLx Short to GND SLx Requirement : Report the fault to GND 9

10 Tech Deep Dive: Over Current detection of Power FETs System Requirement Solution Detection of power FETs from overcurrent Immediate shutdown of power FETs after the fault detection Fault is reported to Digital Logic TI Motor Driver + VDS Gate Driver VDRAIN GHx SHx Power Supply Advantages Reduction of external components for overcurrent protection. Error reporting + VDS GLx SLx GND Programmability of features allows user to change thresholds and times to meet system requirements. Integrated comparators to monitor drain-source voltage of external power FETs. 10

11 Tech Deep Dive: Over Current detection Solution Advantages: Fully integrated solution Reducing external components and fast response Power Supply DRV32xx / DRV83xx VDRAIN Advantages: 2 path fault reporting to Digital Logic Fault logic Deglitch Blanking shutdown + VDS Gate Driver GHx SHx Big shoot through current SPI SPI Threshold detection GLx Short to GND VCC Fault logic Deglitch Blanking + VDS SLx nfault GND Advantages: High accuracy threshold Vth = 0.5V) GND 11

12 Tech Deep Dive: Over Current detection Threshold is accuracy important? VDRAIN Power Supply Example system requirement I FET 60A Over current True over current may not be detected even exceeding over current +30% = 65A + VDS GHx SHx I FET R DSON = 10mΩ 40A +10% = 55A -10% = 45A Typ 50A = 0.5V / 10mΩ + VDS GLx SLx GND normal current -30% = 35A False over current may be detected even in normal current level 12

13 Tech Deep Dive: Over Current detection Selecting Parameter (Timing) Ex) DRV8305-Q1 Datasheet INH INL SHx V DS_TRIP Advantages: SPI Configuration (flexibility for the combination of FET and system requirement) VDS HS comparator output Logic deglitch counter VDS_HS (SPI flag) t blank_vds t deg_vds Comparator output is ignored during t blank_vds Comparator output is ignored if the fault condition is shorter than t deg_vds SPI status bit VDS_HS is set to 1 if the fault condition is longer than t deg_vds 13

14 Serial Communication integrity 14

15 Tech Deep Dive: Data Communication Integrity - Typical implementation Data IC Potential effect : Data error over communication can cause incorrect device setting of IC or incorrect status reporting from IC Typical Implementation Only Address + data Addres s one frame Data IC No error detection by device, read back Parity added to a frame Addres s one frame Data Parity IC Low or middle data integrity : two bit errors are not detected CRC added to a frame Addres s one frame Data CRC IC Middle or High data integrity, but increase SPI length affecting communication band width 15

16 Tech Deep Dive: Device Configuration Data Integrity Typical implementation register 1 Potential effect : Data error of register map can cause incorrect device setting of IC register 2 SPI I/F Typical Implementation register N Read back of registers Read IC /Software load is increased. Higher SPI bandwidth is required during motor operation. 16

17 Tech Deep Dive: Device Configuration Data Integrity Solution - Configuration Data CRC DRV32xx-Q1 register 1 register 2 SPI I/F register N CRC calculation engine + Error detection logic CRC runs periodically to monitor the register map, and the device reports to when a fault is detected. Advantages: Real time monitor of device parameters without extra resource of. High error detection capability using CRC 17

18 Open and Short of Motor Connection 18

19 Tech Deep Dive: Short Detection of Motor Connection (in development) System Requirement Short detection of motor connection (to GND and to Battery) before running motor Solution Short to battery Advantages GND short detection Reduction of external components for fault detection can take action to avoid system damage before the operation Battery short detection Short to GND 19

20 Tech Deep Dive: Short Detection of Motor Connection - System requirement (at power up) Requirement : Detect failure mode at power up before motor starts running. VDRAIN Power Supply Potential effect : External power FETs get damage if the shoot through current condition lasts long Gate Driver GHx SHx Requirement : No motor current is expected during the diagnostic GLx SLx Short to GND Requirement : Report the fault to so that can take the action (no PWM is driven in case of fault) GND 20

21 Tech Deep Dive: Short Detection of Motor Connection Typical implementation External components VDRAIN Power Supply Gate Driver GHx Level shifter SHx VCC GLx ADC SLx GND GND Customer need to know SHx Leakage current (typically not defined in datasheet) to decide the resistance parameters and error detection threshold. 21

22 Tech Deep Dive: Short Detection of Motor Connection Solution Short to GND No fault Short to GND fault VDRAIN Power Supply VDRAIN Power Supply + V TH GHx OFF + V TH GHx OFF V in SHx V in SHx V in < V TH GLx OFF V in > V TH GLx OFF SLx GND Comparator input voltage goes low and the comparator output is low. No fault is reported. SLx GND Comparator input voltage exceeds V TH and the comparator output is high. A fault is reported to via SPI and nfault pin Short to GND 22

23 Tech Deep Dive: Short Detection of Motor Connection Solution Short to Battery TI Products DRV834x-Q1 No fault Short to Battery fault Short to battery VDRAIN Power Supply VDRAIN Power Supply GHx OFF GHx OFF V in < V TH SHx V in > V TH SHx + V TH V in GLx SLx OFF GND + V TH V in GLx SLx OFF GND Comparator input voltage goes low and the comparator output is low. No fault is reported. Comparator input voltage exceeds V TH and the comparator output is high. A fault is reported to via SPI and nfault pin 23

24 Tech Deep Dive: Open Load Detection - System requirement (at power up) Requirement : Detect failure mode at power up before motor starts running. Power Supply Potential effect : Expected motor control is not available in the system. VDRAIN Gate Driver GHx Requirement : No motor current is expected during the diagnostic SHx GLx SLx Open fault GND Requirement : Report the fault to so that can take the action (no PWM) TI Information Selective Disclosure 24

25 Tech Deep Dive: Open Load Detection (in development) TI Products DRV834x-Q1 System Requirement Open detection of power FETs or Motor load before running motor Fault is reported to Driver IC Solution Advantages Reduction of external components for fault detection can take action to avoid system damage before the operation Diagnostic current injection to load Open 25

26 Detailed Agenda Trend of Automotive application and Motor Drivers Autonomous driving, Electrical vehicle Example applications : EPS, Braking Technical Deep Dive architecture, value position and system implementation Serial Communication integrity, Clock Monitor Over current of Power FETs Open and Short of Motor Connection TI solution with PMIC + Motor Driver for robust system design PMIC diagnostic can connect Motor Driver protection 26

27 Motor Driver System Consideration Requirement : Detect failure mode while motor is running, independent from Battery Potential effect : Unintended motor assist to the system. Power Power Supply Gate Driver PWM Requirement : Shutdown motor operation independent from potentially sends unintended PWM control signals to Gate Driver 27

28 Motor Driver System Consideration Typical implementation Battery SW Power External components Power Supply Gate Driver PWM reset in case of failure Special signal or additional communication interface Watchdog Timer IC External logic and level shifter 28

29 Motor Driver System Consideration Solution TPS6538x + DRV32xx Battery Supply TI Products DRV3205-Q1 DRV3245-Q1 TPS6538x-Q1 CAN PHY CANWU VDD5 IGN VDD6 Sensor Wake UP Charge Pump Buck- Boost Sensor Supply 1 Sensor Supply 2 Temp Prot Temp Prot Q&A WD CRC + BIST / DIAG Power Supply IC TPS6538x CAN Supply uc I/O Supply CLK MON VMON Reset / Enable with Readback uc ESM SPI AMUX / DMUX VDD3/5 ENDRV NRES ERROR SPI uc Core Supply Core Power nreset Error Monitor System I/O power PWM External Interrupt / GPIO SPI Multi-channel ADC EN VDDIO PWM DRVOFF nfault SPI VREF SOx sleep control I/O power Voltage Monitor SPI TSD device status Power Supply shutdown shutdown OSC DRV3245 VCPH Charge pump VDS Monitor Gate Driver VGS Monitor Current Sense x 3ch VCPH VDRAIN GHSx SHSx GLSx SLSx IPx INx ADC Phase Check 3 x Power FETs M Sensors DRV32xx : Shutdown path Note) Shutdown implementation will depend on the system requirement, such as independency or redundancy. TPS6538x : Watchdog Timer, error signal monitor and driver shutdown control Core failure 29

30 DRV3xxx family Collateral and Training Application Notes DRV3201 Current Sense Q&A Watchdog Timer DRV3205-Q1 DRV3201 Boost Converter DRV3205-Q1 Electronic Power Steering Design Guide Search "SLVA830" on ti.com White paper on Analog Functional Safety Search "SLYY111" on ti.com DRV3205-Q1 Applications in 24-V Automotive Systems Backwards Batteries: Protecting Automotive Motor- Drive Systems from Reverse Polarity Conditions DRV3000 Motor Driver for Functional Safety Applications training

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