1. Study Report for Brushless DC (BLDC) Motors
DRAFT
By Dean Hu
3/21/2014

2. Introductions to Motors
Types of Motors
AC Motors
INDUCTION MOTOR
SYNCHRONOUS MOTOR
DC Motors
Various wound field motors
Permanent Magnet (PMDC) MOTOR
Brushed DC (BDC) Motors
Brushless DC (BLDC) Motors
Sensored & Sensorless

3. BLDC Motors
Typical Block Diagram

4. BLDC Motors
Sensorless & Sensored Control

5. BLDC Motors
Detailed Block Diagram

6. BLDC Motor Controller
HOLTEK HT66FM5240 – Block Diagram

7. BLDC Motor Controller
HT66FM5240 – Application Circuits

8. BLDC Motor Controller HT66FM5240 – Features VDD/AVDD: 4.5V ~ 5.5V
Package types: 20/28-pin SSOP
Logic (CPU/Peripheral)
fSYS = 32kHz (LIRC) ~ 20MHz (HIRC) by Internal Oscillators
Multi-mode operations: NORMAL, SLOW, IDLE & SLEEP
Flash (program) / RAM (data) / EEPROM (data) Memories
Watchdog Timer & 16-bit/10-bit Periodic Type Timer Modules (PTM)
16-bit Capture Timer Module (CAPTM) for Motor Protection
3-channel 10-bit PWM w/ Complementary Outputs
Bidirectional I/O pins, UART I/F, & I2C I/F
Pin-shared External Interrupts / Time-Based Interrupt

9. BLDC Motor Controllers
HT66FM5240 Features
Analog
8-channel 12-bit A/D Converter (ADC)
One (1) OPAmp for Current Detection
4 Comparators - Comparator 0 has interrupt function
One (1) D/A Converter (DAC)
Low Voltage Reset (LVR)
Low Voltage Detect (LVD)

10. HD66FM5240
D.C. Characteristics

11. HT66FM5240
A.C. Characteristics

12. HT66FM5240 / Analog A/D Converter (ADC), AVDD = 5V (Typ.)
Characteristics

13. HT66FM5240 - ADC ADC Structure ADC Operation
There are two ways to initiate an A/D Converter conversion cycle: using the ADSTS bit, and use the PWM interrupt signal
Limitation: the minimum value of permissible 12-bit A/D converter clock period, tADCK, is 0.8ms

14. HT66FM ADC
A/D Conversion Timing Diagram

15. HT66FM5240 / Analog D/A Converter (DAC): VDD = VLVR (3.15V) ~ 5.5V
Characteristics

16. HT66FM5240 / Analog
Operational Amplifier (OPAmp/OPA): VDD = 3.3V (Typ.)
Characteristics

17. HT66FM5240 / Analog Comparator: VDD = 5V (Typ.)
Electrical Characteristics

18. HT66FM5240
Low Voltage Detector (LVD) - monitor the power supply voltage, VDD
LVD Operation
Low Voltage Detector function operates by comparing VDD with a pre-specified voltage level VLVD, namely, 3.6V, stored in the LVDC register

19. HT66FM5240
Power on Reset (POR)
Electrical Characteristics

20. HT66FM5240
Operating Modes and System Clocks – HIRC & LIRC

21. HT66FM5240 Watchdog Timer Timer Module (TM)
To prevent program malfunctions or sequences from jumping to unknown locations, due to certain uncontrollable external events such as electrical noise
Timer Module (TM)
Multi-purpose timing units
Periodic Type TM (PTM)
5 OP Modes/Functions

22. HT66FM PTM
Block Diagram (for n=0)

23. HT66FM5240 Capture Timer Module (CAPTM)
To detect and measure input signals’ pulse widths and periods, used for Motor Control purposes
2 modes: Compare Mode and Capture Mode
Block Diagram

24. HT66FM5240 - CAPTM Noise Filters for H1/H2/H3/CTIN input signals
Typical Waveforms for CAPNFT=0 & CATNFS = 0 (CAPTC1 Register b4 & b3)

25. HT66FM5240
Noise filter for NFIN input pin, source of 16-bit PTM, TM0, capture circuit

26. HT66FM5240 BLDC Motor Control Circuit
PWMO (output of PWM counter): adjusts PWM duty to control the output motor power thus controlling the motor speed
Mask circuit: determines which PWM modulation signals are enabled or disabled for motor speed control
Dead-Time Insertion circuit: ensures the upper and lower Gate Driver Transistor Pairs are not enabled simultaneously
Staggered circuit: forces all the outputs to off status if the software detects an error condition
Motor Protect circuit: includes functions for motor stall condition, over current protection, external edge triggered Pause pin, external level trigger Fault pin, etc.
Hall Sensor Decoder circuit: is a six-step system which can be used to control the motor direction; the motor forward, backward, brake and free functions are controlled by the HDCD/HDCR registers

27. HT66FM5240
BLDC Motor Control Block Diagram

28. HT66FM5240 – BLDC Control PWM Counter Control Circuit
PWM Block & Timing Diagrams

29. HT66FM5240 – BLDC Control
Block Diagram for Mask, Dead Time, Staggered, and Polarity Functions

30. HT66FM5240 – BLDC Control Mask Function
3 modes: Normal / Brake / Motor Protect
Normal Mode: motor speed control method is determined by the PWMS/MPWE bits in the MCF register
H/W Mask Mode
S/W Mask Mode
Brake Mode: the Brake Mode has the highest priority. When activated, the external Gate Driver Transistor Pair Top arm will be off and the Bottom arm will be on
Motor Protect Mode: when activated, the external Gate Driver Transistor Pair can select the brake, where the top arm is off and the bottom arm is on, or select free running where the top and bottom arm are both off

31. HT66FM5240 – BLDC Control Dead Time Function
The actual dead time value can be setup to be within a value from 0.3μs to 5μs, which is selected by the application program
Timing Diagram

32. HT66FM5240 – BLDC Control Staggered Function
BLDC motor control circuit is designed for default N-type transistor pairs: a "1" value will switch the transistor on and a "0"value will switch it off
Polarity Function – Controlled by PLC register
Default of output pins GAT/GAB/GBT/GBB/GCT/GCB is high impedance

33. HT66FM5240 – BLDC Control Hall Sensor Decoder
Interfaces to the Hall Sensors in the BLDC motor for directional and speed control
Noise Filter, Delay Function, & Motor Control Drive Signals
Block Diagram

34. HT66FM5240 – BLDC Control Hall Sensor Noise Filter
Filters out the effects of noise generated by the large switching currents of the motor driver
Block Diagram

35. HT66FM5240 – BLDC Control Hall Sensor Delay Function
Implement a signal phase forward or phase backward operation
Block Diagram

36. HT66FM5240 – BLDC Control
Delay Function Timing

37. HT66FM5240 – BLDC Control Motor Control Drive Signals
Controlled using the HDCR, HDCD registers and a series of HDCT registers, namely, HDCT0 ~ HDCT11
HDCR: direction is determined using FRS bit while brake can be controlled using BRKE bit
HDCT0 ~ HDCT5 (6 bits) registers are used for the Motor Forward table
HDCT6 ~ HDCT11 (6 bits) registers are used for the Motor Backward table

38. HT66FM5240 – BLDC Control
Motor Drive Signal Timing Diagram – Forward Direction

39. HT66FM5240 – BLDC Control
Motor Drive Signal Timing Diagram – Backward Direction

40. HT66FM5240 – BLDC Control Motor Protection Function
Motors need to be protected from the problems of excessive drive currents, motor stalling, etc to reduce motor damage or for safety reasons
Over Current Protection, Stall Detection, Turn Off Motor using Software
Block Diagram

41. HT66FM5240 – BLDC Control Motor Protection Function
Protection Function Control

42. HT66FM5240 – BLDC Control Motor Protection Over Current Protection
Internal OPA with a gain of 10, high speed (2ms) 10-bit ADC, 8-bit DAC, and a Comparator
To avoid false triggering by noise amplified by OPA, the Fault Mode is needed.
Motor Stall Detection
For 3-phase BLDC applications with Hall Sensors, the 16-bit CAPTM can be used to monitor INT0A, INT0B and INT0C for rotor speed detection
Stall detect mechanism use the Pause Mode

43. HT66FM5240
Over Current Detection (OCD)
Block Diagram

44. HT66FM OCD
The over-current functional block includes an OPA, 12-bit ADC, 8-bit DAC, and Comparator
If an over-current situation is detected then the motor external drive circuit can be switched off immediately to prevent damage to the motor
Two kinds of interrupts are generated for OCD
A/D Converter interrupt - Int_AHL_Lim
Comparator 0 interrupt - Int_Is

45. HT66FM5240
I2C Interface
Block Diagram

46. HT66FM5240 UART Interface Features
Full-duplex, asynchronous communication
8 or 9 bits character length
Even, odd or no parity options
One or two stop bits
Baud rate generator with 8-bit prescaler
Parity, framing, noise and overrun error detection
2-byte deep FIFO Receive Data Buffer
Transmit and receive interrupts

47. HT66FM5240 Interrupts External Interrupt 0/1
Noise Filtered Input Interrupt
Comparator Interrupt
Time Base Interrupt
Multi-function Interrupt: 7 Multi-function interrupts from Hall Sensor interrupts, A/D interrupts, PWM Module interrupts, CAPTM Interrupts, TM Interrupts
A/D Converter Interrupt
PWM Module Interrupts
CAPTM Module Interrupt
TM Module Interrupt
EEPROM Interrupt
LVD Interrupt
I2C Interrupt
UART Interrupt
Interrupt Wake-up Function

48. HT66FM5240
I/O Pin Structures
Generic Input/Output Structure

49. HT66FM5240 – I/O Pins
A/D Input/Output Structure

50. Some Thoughts on HT66FM5240 Single supply: 5V
Internal LDO for 3.3V => OPAmp & Logic (?)
OPAmp is capable of driving 600W and 100pF, input offset can be reduced to ±2mV by calibration
Voltage Reference, such as bandgap
Trimming capability for HIRC & LIRC (embedded oscillators)
ADC might be 12-bit SAR, or using SD ADC for higher resolution (?)
DAC might be R-2R (HT66FM5230 uses R-2R DAC)
Comparators have hysteresis