# US 2001/0022503 A1 · Driving device for three-phase brushless motor

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- Number: US 2001/0022503 A1
- Document ID: US20010022503A1
- Status: Published application
- Kind: A1
- Application number: 09/355,985
- Filed: 1999-08-23
- Published: 2001-09-20
- Earliest claimed: 1997-02-24
- Assignees: Rohm Co., Ltd.
- Inventors: TOMOHIDE HASHIMURA
- Web page: https://patentgrep.com/patent/US20010022503A1

## CPC

- H02P 6/182: using back-emf in windings
- H02P 6/15: Controlling commutation time
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

A driving device for a three-phase brushless motor offers stable rotation characteristics even in case of polarity inversion resulting from braking applied, noise appearing, or other factors arising during rotation of the motor. The driving device has a comparator circuit for comparing the back electromotive forces appearing in the motor individually with the common-terminal voltage to output square-wave signals, a synthesizing circuit for producing drive signals, a circuit for producing from the square-wave signals a speed signal and then shifting the phase thereof to produce a phase signal, and a current supply circuit for supplying drive currents to the motor in accordance with the drive signals and the phase signal. The driving device further has a selector circuit for feeding a select signal back to the gate circuits provided in the stage subsequent to the comparator to perform masking.

## Claims

### Claim 1

A three-phase brushless motor driving device for supplying a three-phase brushless motor with three-phase drive currents that differ in phase by 120 degrees from one another,
wherein passage control means is provided that compares back electromotive forces appearing in three coils provided one for each phase in the three-phase brushless motor individually with a common-terminal voltage of the three coils and that controls comparison outputs individually in such a way that each of the comparison outputs is, in a predetermined short period including a level-shift point thereof, permitted to pass through intact by a control signal output from the passage control means and is, in a period between one such predetermined period and a next such predetermined period, kept at a level at which it is set after the level-shift point, and
wherein the drive currents are produced by current supply means in accordance with signals resulting from passage control.

### Claim 2

A three-phase brushless motor driving device for supplying a three-phase brushless motor with drive currents, comprising:
a comparator circuit for comparing back electromotive forces appearing in three coils provided one for each phase in the three-phase brushless motor individually with a common-terminal voltage of the three coils to produce square-wave signals;
gate circuits for controlling passage of the square-wave signals individually;
a drive waveform synthesizing circuit for synthesizing together outputs of the gate circuits to produce drive signals;
an FG circuit for producing a speed signal from the outputs of the gate circuits;
a phase shifting circuit for producing from the speed signal a phase signal having a phase shifted by 30 degrees relative to the speed signal;
a current supply circuit for supplying the drive currents to the three-phase brushless motor in accordance with the drive signals and the phase signal; and
a selector circuit for feeding a select signal back to the gate circuits in accordance with the drive signals and the phase signal,
wherein the gate circuits allow passage of the square-wave signals individually only in a predetermined period.

### Claim 3 (depends on 2)

A three-phase brushless motor driving device as claimed in claim 2,
wherein the square-wave signals turn from a high level to a low level or from a low level to a high level individually in the predetermined period.

### Claim 4 (depends on 2, 3)

A three-phase brushless motor driving device as claimed in claim 2 or 3,
wherein the driving device is formed as an integrated circuit.