Motorola M68HC08 User manual

MOTOROLA.COM/SEMICONDUCTORS

M68HC08

Microcontrollers

DRM046

Rev. 0, 09/2003

Low Power BLDC

Designer Reference

Reference Design

Manual

Drive for Fans using

the MC68HC908QY4

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DRM046 — Rev 0 Designer Reference Manual

MOTOROLA 3

Low Power BLDC Drive for

Fans using the

MC68HC908QY4 Reference

Design

Designer Reference Manual — Rev 0

by: Radim Visinka, MCSL, Roznov

BLDC Motor Theory by: Pavel Grasblum, MCSL, Roznov

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Designer Reference Manual DRM046 — Rev 0

4 MOTOROLA

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DRM046 — Rev 0 Designer Reference Manual

MOTOROLA List of Sections 5

Designer Reference Manual — DRM046

List of Sections

Section 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Section 2. MC68HC908QY Family Advantages and

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Section 3. BLDC Motor Theory . . . . . . . . . . . . . . . . . . . . 17

Section 4. 3-Phase BLDC Low Voltage Reference

Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Section 5. Hardware Design. . . . . . . . . . . . . . . . . . . . . . . 31

Section 6. Software Design . . . . . . . . . . . . . . . . . . . . . . . 45

Section 7. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Section 8. Appendix A — Schematics and Parts List . .63

Section 9. Appendix B — System Set-up . . . . . . . . . . . . 71

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List of Sections

Designer Reference Manual DRM046 — Rev 0

6 List of Sections MOTOROLA

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DRM046 — Rev 0 Designer Reference Manual

MOTOROLA Table of Contents 7

Designer Reference Manual — DRM046

Table of Contents

Section 1. Introduction

Section 2. MC68HC908QY Family Advantages and

Features

Section 3. BLDC Motor Theory

3.1 Digital Control of a BLDC Motor . . . . . . . . . . . . . . . . . . . . . . . .18

3.2 Independent Switching of Power Transistors . . . . . . . . . . . . . .19

3.3 Complementary Switching of Power Transistors . . . . . . . . . . .20

3.4 Commutation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Section 4. 3-Phase BLDC Low Voltage Reference Design

4.1 Application Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

4.2 Application Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

Section 5. Hardware Design

5.1 Pin-by-Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

5.2 Detailed Design Description . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Section 6. Software Design

6.1 Data Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45

6.2 Software Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49

6.3 Application Porting for the Customer Specific BLDC Motor . . .52

6.4 Software Listing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

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Table of Contents

Designer Reference Manual DRM046 — Rev 0

8 Table of Contents MOTOROLA

6.5 Microcontroller Memory and Peripheral Usage . . . . . . . . . . . .58

Section 7. References

Section 8. Appendix A — Schematics and Parts List

8.1 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63

8.2 Parts Lists. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

Section 9. Appendix B — System Set-up

9.1 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71

9.2 Hardware Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71

9.3 Jumper Settings for Controller Board . . . . . . . . . . . . . . . . . . . .72

9.4 Required Software Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74

9.5 Building and Uploading the Application . . . . . . . . . . . . . . . . . .74

9.6 Executing the Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75

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DRM046 — Rev 0 Designer Reference Manual

MOTOROLA List of Figures 9

Designer Reference Manual — DRM046

List of Figures

Figure Title Page

1-1 Low Power BLDC Drive for Fan . . . . . . . . . . . . . . . . . . . . . . . .13

3-1 BLDC Motor - Cross Section . . . . . . . . . . . . . . . . . . . . . . . . . .17

3-2 Voltage Strokes Applied to the 3-ph BLDC Motor . . . . . . . . . .18

3-3 3-phase BLDC Power Stage. . . . . . . . . . . . . . . . . . . . . . . . . . .19

3-4 Independent Switching of Power Transistors . . . . . . . . . . . . . .20

3-5 Complementary Switching of Power Transistors . . . . . . . . . . .21

3-6 Stator Flux Vectors at Six-Step Control . . . . . . . . . . . . . . . . . .22

3-7 Situation Right Before Commutation . . . . . . . . . . . . . . . . . . . .23

3-8 Situation Right After Commutation . . . . . . . . . . . . . . . . . . . . . .23

4-1 System Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

5-1 Three-Phase BLDC Drive. . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

5-2 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

5-3 Microcontroller with Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

5-4 Hall Sensor Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

5-5 User’s Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

5-6 3-Phase H Bridge (Phase A Shown) . . . . . . . . . . . . . . . . . . . .42

5-7 Current Sensing - Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

6-1 Algorithm Data Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

6-2 Closed Loop Speed Control . . . . . . . . . . . . . . . . . . . . . . . . . . .48

6-3 Software Implementation - General Overview . . . . . . . . . . . . .50

6-4 Stator Flux Vectors with Sectors. . . . . . . . . . . . . . . . . . . . . . . .53

8-1 Microcontroller with Hall Sensor Input and User’s Interface. . .64

8-2 Power Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

8-3 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66

9-1 Setup of the Application with BLDC Motor . . . . . . . . . . . . . . . . 72

9-2 Jumper Reference of BLDC Drive Board . . . . . . . . . . . . . . . . .73

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List of Figures

Designer Reference Manual DRM046 — Rev 0

10 List of Figures MOTOROLA

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DRM046 — Rev 0 Designer Reference Manual

MOTOROLA List of Tables 11

Designer Reference Manual — DRM046

List of Tables

Table Title Page

2-1 Summary of Device Variations . . . . . . . . . . . . . . . . . . . . . . . . .15

3-1 Commutation Sequence for Counterclockwise Rotation . . . . .24

3-2 Commutation Sequence for Clockwise Rotation . . . . . . . . . . .24

5-1 Connector J4 Signal Descriptions. . . . . . . . . . . . . . . . . . . . . . .34

5-2 Jack Connector J2 Signal Descriptions . . . . . . . . . . . . . . . . . .34

5-3 Connector J5 Signal Descriptions. . . . . . . . . . . . . . . . . . . . . . .34

5-4 Jack Connector J1 Signal Descriptions . . . . . . . . . . . . . . . . . .35

5-5 Jack Connector J3 Signal Descriptions . . . . . . . . . . . . . . . . . .36

5-6 Connection of Signals to MCU . . . . . . . . . . . . . . . . . . . . . . . . .37

6-1 Determination of Hall Sensor Pattern . . . . . . . . . . . . . . . . . . . .53

6-2 Determination of Commutation Vector for CCW. . . . . . . . . . . .54

6-3 Determination of Commutation Vector for CW . . . . . . . . . . . . .55

6-4 Commutation Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56

6-5 Memory Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58

6-6 MC68HC908QY4 Modules Usage . . . . . . . . . . . . . . . . . . . . . .58

8-1 Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

9-1 BLDC Drive Board Jumper Settings . . . . . . . . . . . . . . . . . . . . .73

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List of Tables

Designer Reference Manual DRM046 — Rev 0

12 List of Tables MOTOROLA

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DRM046 — Rev 0 Designer Reference Manual

MOTOROLA Introduction 13

Designer Reference Manual — DRM046

Section 1. Introduction

This Application Note describes the design of a low power 3-phase

BLDC (Brushless DC) motor drive with Hall Sensors, based on

Motorola’s MC68HC908QY4 microcontroller.

Figure 1-1. Low Power BLDC Drive for Fan

BLDC motors are very popular in a wide application area. Compared

with a DC motor, the BLDC motor uses an electric commutator

(replacing the mechanical commutator), and so is more reliable than the

DC motor. In BLDC motors, rotor magnets generate the rotor’s magnetic

flux so that they achieve higher efficiency. Therefore, BLDC motors may

be used in white goods, high-end pumps, fans and in other appliances

which require high reliability and efficiency.

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Introduction

Designer Reference Manual DRM046 — Rev 0

14 Introduction MOTOROLA

The concept of the application is a speed-closed loop BLDC drive using

a Hall position sensor. It serves as a reference design of a BLDC motor

control system for a low voltage fan application. The power stage is

designed for 48V DC line voltage and 400W output power. The

application is based on the low-cost MC68HC908QY4 “Nitron“

microcontroller. The design is focused on minimal cost and maximal

component integration for low cost applications.

This Application Note includes the basic motor theory, system design

concept, hardware and software design, hardware schematics, and s/w

listing. The design can be used as a reference design for developing

customer specific applications.

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DRM046 — Rev 0 Designer Reference Manual

MOTOROLA MC68HC908QY Family Advantages and Features 15

Designer Reference Manual — DRM046

Section 2. MC68HC908QY Family Advantages and Features

The MC68HC908QY4 is a member of the low-cost, high-performance

M68HC08 Family of 8-bit microcontroller units (MCUs). All MCUs in the

family use the enhanced M68HC08 central processor unit (CPU08) and

are available with a variety of modules, memory sizes and types, and

package types.

Features include:

• High-performance M68HC08 CPU core

• 5-V and 3-V operating voltages (V

DD)

• 8-MHz internal bus operation at 5 V, 4-MHz at 3 V

• Trimmable internal oscillator

– 3.2 MHz internal bus operation

– 8-bit trim capability (± 25% untrimmed, ± 5% trimmed)

• Auto wake-up from STOP capability

Table 2-1. Summary of Device Variations

Device FLASH Memory Size RAM Memory Size

Analog-to-Digital

Converter

Count

MC68HC908QT1 1536 bytes 128 Bytes - 8 pins

MC68HC908QT2 1536 bytes 128 Bytes 4 ch, 8 bit 8 pins

MC68HC908QT4 4096 bytes 128 Bytes 4 ch, 8 bit 8 pins

MC68HC908QY1 1536 bytes 128 Bytes - 16 pins

MC68HC908QY2 1536 bytes 128 Bytes 4 ch, 8 bit 16 pins

MC68HC908QY4 4096 bytes 128 Bytes 4 ch, 8 bit 16 pins

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MC68HC908QY Family Advantages and Features

Designer Reference Manual DRM046 — Rev 0

16 MC68HC908QY Family Advantages and Features MOTOROLA

• On-chip in-application programmable FLASH memory

• On-chip random-access memory (RAM)

• • 2-channel, 16-bit timer interface module (TIM)

• • 4-channel, 8-bit analog-to-digital converter (ADC) on

MC68HC908QY2, MC68HC908QY4, MC68HC908QT2, and

MC68HC908QT4

• 5 or 13 bidirectional input/output (I/O) lines, and one input only

• 6-bit keyboard interrupt with walk-up feature (KBI)

• Low-voltage inhibit (LVI) module

• System protection features

• External asynchronous interrupt pin with internal pull-up (IRQ)

shared with general-purpose input pin

• Master asynchronous reset pin (RST) shared with

general-purpose input/output (I/O) pin

• Power-on reset

• Power saving stop and wait modes

• MC68HC908QY4, MC68HC908QY2, and MC68HC908QY1 are

available in these packages:

– 16-pin plastic dual in-line package (PDIP)

– 16-pin small outline integrated circuit (SOIC) package

– 16-pin thin shrink small outline package (TSSOP)

• • MC68HC908QT4, MC68HC908QT2, and MC68HC908QT1 are

available in these packages:

– 8-pin PDIP

– 8-pin SOIC

– 8-pin dual flat no lead (DFN) package

The BLDC motor control application requires six PWM outputs, three

Hall position sensor inputs and an ADC channel for voltage

measurements as a minimum. Therefore 16-pin MC68HC908QY2 or

MC68HC908QY4, that accommodate ADC, are the right choice.

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DRM046 — Rev 0 Designer Reference Manual

MOTOROLA BLDC Motor Theory 17

Designer Reference Manual — DRM046

Section 3. BLDC Motor Theory

A brushless DC (BLDC) motor is a rotating electric machine where the

stator is a classic three-phase stator like that of an induction motor, and

the rotor has surface-mounted permanent magnets (see Figure

3-1. BLDC Motor - Cross Section).

In this respect, the BLDC motor is equivalent to a reversed DC

commutator motor, in which the magnet rotates while the conductors

remain stationary. In the DC commutator motor, the current polarity is

altered by the commutator and brushes. On the other hand, in the

brushless DC motor, the polarity reversal is performed by power

transistors switching in synchronization with the rotor position.

Therefore, BLDC motors often incorporate either internal or external

position sensors to sense the actual rotor position, or the position can be

detected without sensors.

Figure 3-1. BLDC Motor - Cross Section

Stator

Stator winding

(in slots)

Shaft

Rotor

Air gap

Permanent magnets

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BLDC Motor Theory

Designer Reference Manual DRM046 — Rev 0

18 BLDC Motor Theory MOTOROLA

3.1 Digital Control of a BLDC Motor

The BLDC motor is driven by rectangular voltage strokes coupled with

the given rotor position (see Figure 3-2. Voltage Strokes Applied to

the 3-ph BLDC Motor). The generated stator flux interacts with the rotor

flux, which is generated by a rotor magnet, defines the torque and thus

the speed of the motor. The voltage strokes must be properly applied to

the two phases of the three-phase winding system so that the angle

between the stator flux and the rotor flux is kept close to 90°, to get the

maximum generated torque. Due to this fact, the motor requires

electronic control for proper operation.

Figure 3-2. Voltage Strokes Applied to the 3-ph BLDC Motor

For the common 3-phase BLDC motor a standard 3-phase power stage

is used, as is illustrated in Figure 3-3. 3-phase BLDC Power Stage.

The power stage utilizes six power transistors with switching in either the

independent mode or complementary mode.

30º 60º 90º 120º 150º 180º 210º 240º 270º 300º 330º

Electrical

angle

Voltage

Phase A

Phase B

Phase C

+U

DCB

-U

DCB

+U

DCB

-U

DCB

+U

DCB

-U

DCB

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BLDC Motor Theory

Independent Switching of Power Transistors

DRM046 — Rev 0 Designer Reference Manual

MOTOROLA BLDC Motor Theory 19

Figure 3-3. 3-phase BLDC Power Stage

In both modes the 3-phase power stage energizes two motor phases

concurrently. The third phase is unpowered (see Figure 3-2. Voltage

Strokes Applied to the 3-ph BLDC Motor). Thus, we get six possible

voltage vectors that are applied to the BLDC motor using a PWM

technique. There are two basic types of power transistor switching:

independent switching, and complementary switching.

3.2 Independent Switching of Power Transistors

With independent switching, only two transistors are switched on when

current is conducted from the power supply to the phase of the BLDC

motor. In one phase, the top transistor is switched on; in the second

phase, the bottom transistor is switched on and the third phase is not

powered. During freewheeling all transistors are switched off (see

Figure 3-4. Independent Switching of Power Transistors).

Q1

PWM_Q5

Q6

Q4

C1

Phase_

C

PWM_Q1

PWM_Q4

PWM_Q3

Phase_B

GND

Q2

U

DCB

PWM_Q2

Phase_A

Q3

PWM_Q6

Q5

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BLDC Motor Theory

Designer Reference Manual DRM046 — Rev 0

20 BLDC Motor Theory MOTOROLA

Figure 3-4. Independent Switching of Power Transistors

3.3 Complementary Switching of Power Transistors

With complementary switching, two transistors are switched on when the

phase of the BLDC motor is connected to the power supply. But there is

a difference during freewheeling. With independent switching, all the

transistors are switched off. The current continues to flow in the same

direction through freewheeling diodes until it falls to zero. Contrary to

this, with complementary switching, the complementary transistors are

switched on during freewheeling. Thus the current may be able to flow

in the opposite direction. Figure 3-5. Complementary Switching of

Power Transistors depicts the complementary switching.

10º 20º

30º

40º 50º 60º 70º 80º 90º

Electrical

angle

PWM Q1

PWM Q2

PWM Q3

PWM Q4

PWM Q5

PWM Q6

PWM

switching

ON

OFF

ON

OFF

ON

OFF

ON

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