# US 12,015,363 B2 · Motor drive circuit, motor system, and electric device

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- Number: US 12,015,363 B2
- Document ID: US12015363B2
- Status: Granted
- Kind: B2
- Application number: 17/948,468
- Filed: 2022-09-20
- Published: 2023-03-30
- Granted: 2024-06-18
- Earliest claimed: 2021-09-27
- Assignees: Rohm Co., Ltd.
- Applicants: Rohm Co., Ltd.
- Inventors: Yoshito Otaguro
- Web page: https://patentgrep.com/patent/US12015363B2

## CPC

- H02P 27/08: with pulse width modulation
- H02P 6/08: Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence)
- H02P 6/15: Controlling commutation time
- H02P 6/157: {wherein the commutation is function of electro-magnetic force [EMF]}
- H02P 6/182: using back-emf in windings
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

A motor drive circuit includes: a PWM signal generation part configured to generate a PWM signal based on a count value of a counter; a detection part configured to detect a zero crossing of a counter electromotive voltage generated in a coil of a motor; a prediction part configured to predict an arrival timing of the zero crossing of the counter electromotive voltage; a stop part configured to stop a counting operation of the counter after a first time point going back from the arrival timing predicted by the prediction part; and a reset part configured to reset the count value at a timing at which the detection part detects the zero crossing of the counter electromotive voltage.

## Claims

### Claim 1

A motor drive circuit, comprising:
a PWM signal generation part configured to generate a PWM signal based on a count value of a counter;
a detection part configured to detect a zero crossing of a counter electromotive voltage generated in a coil of a motor;
a prediction part configured to predict an arrival timing of the zero crossing of the counter electromotive voltage;
a stop part configured to stop a counting operation of the counter after a time point at which the count value reaches a predetermined value, during a predetermined time period after a time point going back from the arrival timing predicted by the prediction part; and
a reset part configured to reset the count value at a timing at which the detection part detects the zero crossing of the counter electromotive voltage.

### Claim 2 (depends on 1)

The motor drive circuit of claim 1, wherein the prediction part is configured to predict the arrival timing from past detection results of the detection part.

### Claim 3 (depends on 1)

The motor drive circuit of claim 1, wherein the detection part is configured to detect the zero crossing of the counter electromotive voltage for each mechanical angle of 360 degrees of the motor.

### Claim 4 (depends on 1)

The motor drive circuit of claim 1, wherein the stop part and the reset part are configured to operate when the motor is driven at a constant target rotation speed.

### Claim 5 (depends on 1)

The motor drive circuit of claim 1, wherein a length of a time between the arrival timing and the time point going back from the arrival timing is longer than a cycle of the PWM signal.

### Claim 6 (depends on 1)

A motor system, comprising:
the motor; and
the motor drive circuit of claim 1 configured to drive the motor.

### Claim 7 (depends on 6)

An electric device, comprising:
the system of claim 6.