Monolithic Power Systems, Inc. · NASDAQ:MPWR

Monolithic Power Systems — Technical Presentation (August 2021)

19 slides from Monolithic Power Systems's technical presentation, Aug 5, 2021

  1. Slide 1: Motor Driver ICs: Faults and Protection

    Motor Driver ICs Faults and Protection Jian Zhao Aug. 2021 rev 20180504

  2. Slide 2: Contents

    Contents • DC Motor Basics • Starting, Stopping, and Reversing Motors • Abnormal Stresses – Shorts, Overvoltage • Motor Driver Protection Features • Summary / Q&A

  3. Slide 3: DC Motor Basics

    DC Motor Basics Series Resistance RS Power Source Series Inductance VSRC LS Back EMF VBEMF

  4. Slide 4: Torque and Current

    Torque and Current mMmrS

  5. Slide 5: DC Motor Specs and Ratings

    DC Motor Specs and Ratings Output Power 15 Watts Nominal Voltage (VSRC) 24 Volts No Load Speed 4000 RPM No Load Current 0.11 Amps Full Load Speed 2920 RPM Full Load Continuous Torque 50 mNm Full Load Continuous Current 1 A Stall Torque 190 nMn Stall Current 3.6 Amps Resistance (RS) 6.7 Ω

  6. Slide 6: Startup of a DC Motor

    Startup of a DC Motor Electrical energy Kinetic energy Series Resistance RS Current Power Source VSRC Rotation Torque Back EMF 0V When speed = 0: I = VSRC / RS

  7. Slide 7: Managing Startup Current

    Managing Startup Current 3.6A 1A 60mS 120mS

  8. Slide 8: Stopping the Motor: Coasting

    Stopping the Motor: Coasting Kinetic energy Series Resistance RS Rotation Torque Back EMF VBEMF Heat Coast I=0

  9. Slide 9: Stopping the Motor: Braking

    Stopping the Motor: Braking Electrical energy Kinetic energy Series Resistance Heat RS Rotation Torque Current Back EMF VBEMF Heat Short Brake I = VSRC / RS

  10. Slide 10: Reversing the Motor

    Reversing the Motor Electrical energy Kinetic energy Series Resistance RS Current Power Source VSRC Back EMF VBEMF Reverse I = (VBEMF + VSRC) / RS = ~ 2 * VSRC / RS

  11. Slide 11: Short Circuits

    Short Circuits

  12. Slide 12: Voltage Stresses

    Voltage Stresses Current Driver

  13. Slide 13: Voltage Rise due to Deceleration

    Voltage Rise due to Deceleration Electrical energy Kinetic energy Voltage! Current Current Rotation Torque H-Bridge

  14. Slide 14: Thermal Stresses

    Thermal Stresses Resistive Losses PR = I2R VIN

  15. Slide 15: Motor Driver Protection Features: Overcurrent / Short Circuit

    Motor Driver Protection Features: Overcurrent / Short Circuit VIN HS Gate Timing and VCP Driver Control OUT1 Logic LS Gate OUT2 VG Driver `` OC_REF OCP Comparator VIN Fault nFAULT Handling UVLO_REF UVLO Comparator OVP_REF TSD VIN OVP Comparator

  16. Slide 16: False Overcurrent Trips

    False Overcurrent Trips VIN VIN OUT1 OUT2 GND

  17. Slide 17: Motor Driver Protection Features: Over/Under Voltage

    Motor Driver Protection Features: Over/Under Voltage VIN HS Gate Timing and VCP Driver Control OUT1 Logic LS Gate OUT2 VG Driver `` OC_REF OCP Comparator VIN Fault nFAULT Handling UVLO_REF UVLO Comparator OVP_REF TSD VIN OVP Comparator

  18. Slide 18: Motor Driver Protection Features: Thermal Protection

    Motor Driver Protection Features: Thermal Protection VIN HS Gate Timing and VCP Driver Control OUT1 Logic LS Gate OUT2 VG Driver `` OC_REF OCP Comparator VIN Fault nFAULT Handling UVLO_REF UVLO Comparator OVP_REF TSD VIN OVP Comparator

  19. Slide 19: Summary

    Summary • Consider the stresses in a motor drive circuit when starting, stopping, and reversing the motor • Minimize power supply inductance • Add clamp circuits and large bulk capacitors to mitigate voltage transients • Be aware of heat dissipated in a motor driver, especially during abnormal condi

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