ID 610 C Introduction to BLDC Motor Control

ID 610 C: Introduction to BLDC Motor Control Avnet Jim Carver Technical Director, Advanced Architectures 12 October 2010 Version 1. 0

Renesas Technology and Solution Portfolio Microcontrollers & Microprocessors #1 Market share worldwide * ASIC, ASSP & Memory Advanced and proven technologies Solutions for Innovation Analog and Power Devices #1 Market share in low-voltage MOSFET** * MCU: 31% revenue basis from Gartner "Semiconductor Applications Worldwide Annual Market Share: Database" 25 March 2010 ** Power MOSFET: 17. 1% on unit basis from Marketing Eye 2009 (17. 1% on unit basis). 2

Renesas Technology and Solution Portfolio Microcontrollers & Microprocessors #1 Market share worldwide * ASIC, ASSP & Memory Advanced and proven technologies Solutions for Innovation Analog and Power Devices #1 Market share in low-voltage MOSFET** * MCU: 31% revenue basis from Gartner "Semiconductor Applications Worldwide Annual Market Share: Database" 25 March 2010 ** Power MOSFET: 17. 1% on unit basis from Marketing Eye 2009 (17. 1% on unit basis). 3

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Microcontroller and Microprocessor Line-up Superscalar, MMU, Multimedia § Up to 1200 DMIPS, 45, 65 & 90 nm process § Video and audio processing on Linux § Server, Industrial & Automotive High Performance CPU, Low Power § Up to 500 DMIPS, 150 & 90 nm process § 600 u. A/MHz, 1. 5 u. A standby § Medical, Automotive & Industrial High Performance CPU, FPU, DSC H 8 SX M 16 C R 32 C General Purpose § Up to 10 DMIPS, 130 nm process § 350 u. A/MHz, 1 u. A standby § Capacitive touch 5 § Up to 165 DMIPS, 90 nm process § 500 u. A/MHz, 2. 5 u. A standby § Ethernet, CAN, USB, Motor Control, TFT Display § Legacy Cores § Next-generation migration to RX Ultra Low Power Embedded Security § Up to 25 DMIPS, 150 nm process § Up to 25 DMIPS, 180, 90 nm process § 190 u. A/MHz, 0. 3 u. A standby § 1 m. A/MHz, 100 u. A standby § Application-specific integration § Crypto engine, Hardware security

Agenda n Motor Types Overview n BLDC Motor Applications n Comparison of DC to Brushless DC Motors n Hall Sensors n Six-Step Commutation n Sensorless Commutation with Back-EMF n Vector Motor Control basics n Closed-Loop Speed Control n Introduction to BLDC Motor Control Evaluation Kit n Summary 6

Motor Types 7

Expanding BLDC Motor Control Applications Transition to AC, DC and Universal Motors 8 As consumers demand more energy efficient products, more BLDC motors are being used. BLDC

Brushed DC Motors Review n A winding assembly (armature) within a stationary magnetic field n Brushes and Commutators switch current to different windings in correct relation to the outer permanent magnet field. n Pros: n Electronic control is simple, no need to commutate in controller n Requires only four power transistors n Cons: n A sensor is required for speed control n The brushes and commutator create sparks and wear out n Sparks limit peak power n Heat in armature is difficult to remove n Low power density 9

Brushless DC Motors n Permanent magnet rotor within stationary windings Pros: n No brushes or commutator to wear out n No sparks and no extra friction n More efficient than DC motor n Higher speed than DC motor n Higher power density than DC motor Cons: n Rotor sensor OR sensorless methods needed to commutate n Requires six power transistors 10 Stator windings Permanent Magnet Rotor

Brushed DC Commutation n The windings in the armature are switched to the DC power by the brushes and armature + n Each winding sees a positive voltage, then a disconnect, then a negative voltage n The field produced in the armature interacts with the stationary magnet, producing torque and rotation + U 11 - U N S

DC Motor Bridge n The DC motor needs four transistors to operate the DC motor n The combination of transistor is called an H-Bridge, due to the obvious shape n Transistors are switched diagonally to allow DC current to flow in the motor in either direction n The transistors can be Pulse Width Modulated to reduce the average voltage at the motor, useful for controlling current and speed 12 1 0 0 1 0

Three-Phase Bridge to Drive BLDC Motor n The Brushless DC motor is really a DC motor constructed inside-out, but without the Brushes and Commutators n The mechanical switches are replaced with transistors n The windings are moved from the armature, to the stator n The magnet is moved from the outside to become the rotor N 13 S U V W N S

Six-step Commutation U V W 14

Six-Step Current Waveform n Here we see the individual steps in a real trapezoidal current waveform n The PWM ripple is visible when the phase is active n The rising and falling edges are sloped, giving the trapezoidal shape n The amount of slope is a function of the winding inductance 15

Hall Sensors detect magnetic fields, and can be used to sense rotor angle The output is a digital 1 or 0 for each sensor, depending on the magnetic field nearby Each is mounted 120 -degrees apart on the back of the motor As the rotor turns, the Hall sensors output logic bits which indicate the angle H 1 N S H 3 16 H 2

Hall Sensor Commutation The combination of all three sensors produce six unique logic combinations or steps These three bits are decoded into the motor phase combinations 17

3 -Phase PWM We can divide up the phase data into individual transistor gate signals Now we can see how we can modulate one transistor at a time to regulate the motor voltage, and also the speed 18

Sensorless Commutation n Instead of using sensors like Halls, we can let the motor tell us which phase should be energized n The Brushless DC motor acts as a generator when it rotates, creating voltages n The three phases produce three voltages 120 -degrees apart n The voltage generated by the motor is called Back Electro. Motive Force, a. k. a. Back-EMF or just BEMF 19

Brushless DC Motor BEMF n The Back-EMF is the voltage generated in stator windings as the rotor moves n BEMF voltages are more or less sinusoidal (depending on the motor) and are symmetrical from phase to phase n We detect the zero crossings of each phase to commutate n The motor MUST be moving to generate BEMF voltages 20

Brushless DC Motor BEMF n The Back-EMF is the voltage generated in stator windings as the rotor moves n BEMF voltages are more or less sinusoidal (depending on the motor) and are symmetrical from phase to phase n We detect the zero crossings of each phase to commutate n The motor MUST be moving to generate BEMF voltages 21

Startup of BEMF System n Since only a spinning motor generates BEMF signals n Start the motor in open loop l First align rotor to a known angle l Then energize the windings to step rotor to next step n Accelerate steps until speed is sufficient to “see” BEMF zero crossings reliably n Switch to BEMF commutation n Once operating, this is almost identical to six-step operation with Hall sensors 22

Sinusoidal Methods n Stepped commutation methods work well, but… n The Back-EMF waveform is more sinusoidal than trapezoidal n If we can match the sinusoidal waveform, we can improve performance n We will show two sinusoidal methods: l 180 -Degree Sinusoidal l “Field Oriented” or “Vector” control 23

180° Sinusoidal Commutation n Modulates sine waves in all three windings n Pros: n No square edges l Lower Torque Ripple then six-step drive l Lower audible noise n Higher efficiency and torque l Stator angle is rotated smoothly rather than in 60 degree jumps l Each phase is utilized all of the time n Cons: n Needs higher resolution feedback to calculate sine waves with low distortion n Needs more sophisticated processing to calculate sine PWM values on the fly n Bandwidth of currents are limited due to motor impedance, this hurts high speed performance 24

Vector (Field Oriented Control) Drive n This method mathematically converts the 3 -phase voltage and current into a simple DC motor representation n Uses this data to calculate the best angle for commutation n Creates new 3 -phase sinusoidal PWM based on calculation n Repeats the calculations at PWM frequency n Pros: l l Highest Torque efficiency Highest Bandwidth Widest Speed Range Lowest Audible Noise n Cons: l Complicated Algorithm l Needs powerful processor 25

BLDC Motor Speed Control n The goal of most Electronic Motor Control Systems is Speed Control n Speed Control systems are more or less complicated, depending on accuracy required n The simplest speed control is Open-Loop, that is, without speed feedback n In this configuration, a speed command is converted to a fixed voltage (PWM duty) which is sent to the motor n The motor may go the right speed, or it may not, it depends on the load n Without feedback, there is no way to tell internally what the real speed is and so may require outside adjustment Speed Command 26 Pulse Width Modulator Transistors Motor Load

Closed-Loop Control n To get automatic speed control, feedback is needed n Feedback systems could be Hall Sensors, Encoders, Resolvers, tachometers or other devices n The resolution and bandwidth of the feedback sensor limit the resolution and bandwidth of the speed loop n Below is a block diagram of a simple control loop n Our Reference Command is the speed we desire, and the Control Mechanism is our motor and motor control Feedback Reference Command 27 + Control Mechanism Sensor

Closed Loop Speed Control n The generic terms can be replaced with terms common to motor control n The speed is often referred to as the Greek Letter Omega w and motor angle is Theta θ n The Reference input is shown as Omega star w * n The Control Mechanism is a mathematical function, usually a Proportional-Integral (PI) algorithm n The speed sensors can be the same Hall sensors used for commutation, where the speed is calculated from the time between steps Motor PI Controller ω* θ ω Speed Calculation 28 PWM Generation Hall Sensors

Closed Loop Speed Control n The way the loop works is to first measure the difference between the commanded speed and the actual speed n If the speed is to low, the PI controller increases the PWM duty which sends more voltage to the motor, correcting speed n If the speed to too high, the PI controller reduces the PWM, reducing the average voltage, so the motor slows down to the correct speed n The Proportional and Integral parameters have to be tuned to optimized the speed loop response-prevent speed Motor oscillations PI Controller ω* θ ω Speed Calculation 29 PWM Generation Hall Sensors

Motor Kit for Trapezoidal Control n BLDC Motor, Board, Software, Schematics, Tool and GUI R 8 C/25 30

Motor Control Evaluation Kit n In order to help users decide on what kind of motor control they need, Renesas has introduced the YMCRPR 8 C 25 Motor Control Evaluation Kit n The kit includes all that is needed to try Hall and BEMF commutated Brushless DC motor control with closed speed loops including, the control board, motor, debugger, power supply and software 31

YMCRPR 8 C 25 Block Diagram 32

Motor Control Board n IGBT module capable of 10 amps. n 3 -Phase output capable of running DC and BLDC motors n 15 V and 5 V regulators on board. n Voltage input from a single 24 V (18 -36 VDC) supply, no shock hazard. 33

Board User Interface n Large potentiometer for speed control setting n 2 x 8 LCD display with contrast pot for monitoring speed, current, etc. n Four push-buttons n Bus voltage monitoring to MCU n Current monitoring to the module for automatic protection 34

Commutation Options n Back-EMF detection comparators n Jumper selection (no soldering) between Hall and BEMF modes n Input connector for Hall signals from motor 35

Debugging Capabilities n Optically Isolated RS 232 communication n Optically Isolated E 8(a) connector n Prototyping areas (under LCD) n LED’s for monitoring PWM lines, and GPIO n Abundant test points 36

Motor Control Graphical User Interface Speed Slider Target Speed Actual Speed Stop Motor Current System Status 37

Project Navigator HEW Development Environment Source Code Editor Output Window 38

Summary n DC and BLDC motors were compared n BLDC motors were shown to offer better performance n A large number of applications are moving from other motor types to BLDC motors n Electronic BLDC motor control can be as simple as six-step or as complicated as Vector Control n Closed Loop Speed Control was explained n The Renesas BLDC Motor Control Evaluation Kit was introduced as a way to help get started in BLDC motor control development 39

Questions? 40

Appendix 41

R 32 C 50 MHz M 16 C 20 MHz 32 -bit 78 K 0 R 100 MHz V 850 ES 32 -bit RX 600 100 MHz 200 MHz H 8 S/SX 50 MHz 8 -bit 32 -bit 20 MHz 32 -bit 200 MHz RX 600 16 -bit 200 MHz 240 MHz SH-3 8 -bit V 850 ES 32 -bit SH-2 A 600 MHz SH-4 16 -bit General Purpose 32 -bit Ultra Low Power 32 -bit TFT LCD Control SH-2 A 32 -bit High-end Connectivity SH-4 A 32 -bit Application Processor 32 -bit Renesas MCU and MPU Solutions 50 MHz 78 K 0 10 MHz R 8 C 20 MHz Application Focused Solutions Wi. Fi SH, RX, R 8 C 42 Motor Control SH, V 850, RX, 78 K 0 R, R 8 C Capacitive Touch R 8 C Industrial CAN Lighting R 8 C, R 32 C, SH 78 K 0

Motor Control Applications & Renesas Solutions Super. H RX V 850 78 K 0 R R 8 C Fans, Kitchen Appliances, Pumps, Power-Tools SPEED CONTROL Torque Control (Limited) Low-Range 43 Medical Industrial, Washers, Compressors Motion Control Pool Pumps, Washers Health-Equipment Compressors SPEED + TORQUE CONTROL Mid-Range SPEED + DYNAMIC TORQUE + MOTION CONTROL High-End

Renesas Motor Control Solutions n Renesas covers every motor control application from low-end to high-end n Renesas can provide all motor algorithms from Trapezoidal control to Sensor-less Vector control n Wide product portfolio l 16 bit MCU (20 MHz): R 8 C, 78 K 0 R l 32 bit MCU (48 MHz to 200 MHz): RX, V 850, SH l These products have peripherals dedicated for Motor Control such as Timers and ADC 44

Motor Control Solution Summary Motor Type 1 -Ø ACIM (PSC) 1 -Ø BLDC Universal (Brushed) DC 3 -Ø ACIM Algorithm R 8 C V/f, Open Loop Y Fixed Duty (Hall) Y Closed Loop (Hall) Y TRIAC Control ( speed loop w/Tachometer) Y PWM Chopper (speed loop w/Tachometer) Y V/f, Open Loop Y 78 K 0 R RX Y Y Speed Loop w/Tachometer Y Sensorless Vector Control 3 -Ø BLDC V 850 SH 2/ SH 2 A 120 -deg Trapezoidal (Hall) Y 120 -deg Trapezoidal (BEMF) Y 180 -deg Sine (HALL) Y Y * Y Y Sensor based Vector Control Y Position Control (Encoder + Hall) Sensorless Vector Control, 2 DCCT, 3 -shunt, 1 -shunt 45 Y Y *: Under development